letnik/volume 53 - {t./no. 1/07 - str./pp. 1-64 Ljubljana, jan./Jan. 2007, zvezek/issue 501 STROJNIŠKI VESTNIK JOURNAL OF MECHANICAL ENGINEERING cena 3,34 EUR 9 770039 248001 I96(200m/si 'otOGOrrt/s) ISSN 0039-2480 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 1 Vsebina - Contents Vsebina - Contents Strojniški vestnik - Journal of Mechanical Engineering letnik - volume 53, (2007), številka - number 1 Ljubljana, januar - January 2007 ISSN 0039-2480 Izhaja mesečno - Published monthly Uvodnik Editorial Alujevie A.: Strojniški vestnik v letu 2007 2 Alujevie A.: Journal of Mechanical Engineering in Year 2007 Razprave Papers Ozalp, A. A.: Vzporedni vplivi pospeška in Ozalp, A. A: Parallel Effects of Acceleration and površinskega ogrevanja na stisljiv tok: Surface Heating on Compressible Flow: simulacija vesoljske pogonske šobe s srednje Simulation of an Aerospace Propulsion Nozzle veliko površinsko obrabo 3 with a Medium Amount of Surface Wear Imrak, C. E., Gerdemeli, L: Določitev tornega Imrak, C. E., Gerdemeli, I.: Determination of the količnika v brazdah z napetostno Friction Coefficient of Groove Forms Using funkcijo 13 the Stress-Function Method Bazaras, J., Bazaras, Ž., Sapragonas, J.: Numerično Bazaras, J., Bazaras, Ž., Sapragonas, J.: Numerical modeliranje notranjih zvokov v železniških Modelling of the Internal Sound in Railway vozilih 18 Rolling Stock Ulozas, R. V.: Teoretična in eksperimentalna analiza Ulozas, R V.: A Theoretical and Experimental Investigation dinamike mehanizmov Rolamite 26 of the Dynamics of Rolamite-Type Mechanisms Voča, N., Krička, T, Janušič, V.: Optimizacija Voča, N, Krička, T., Janušič, V.: Optimization of the neprekinjenega postopka sušenja v Performance of the Continuous-Drying težnostnih sušilnicah 48 Process in Gravity Dryers Osebne vesti Personal Events Prešernove nagrade za študente Fakultete za Students’ Prešeren Awards of the Faculty of strojništvo v Ljubljani 59 Mechanical Engineering in Ljubljana Doktorati, magisterija in diplome 61 Doctor’s, Master’s and Diploma Degrees Navodila avtorjem 63 Instructions for Authors Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 2 Uvodnik - Editorial Strojniški vestnik v letu 2007 - Journal of Mechanical Engineering in Year 2007 Leto je naokrog in naša Slovenija je vstopila in odlivov sredstev. Ko mi bo konec 2007 potekel v evroobmočje. Ob tem je Izdajateljski svet petletni mandat, bom uredniška opravila prepustil Strojniškega vestnika zaradi denarnih težav uporabil svojemu namestniku, ki naj ga izvolijo ali pa izberejo "zasilno zavoro" in uvedel prispevno dajatev 20 koga, da bo zbiral oglase in bo iz tega prejemal tudi evrov/stran, to bodo morali poravnati avtorji v objavo svoje plačilo. Tak podjetniški način utegne izkopati sprejetih prispevkov, ki so prispeli v uredništvo po rešitev denarnih problemov Strojniškega vestnika. 1.1.2007. Drugače se ne moremo izkopati iz “rdečih Meni so bili pred dvema letoma ukinjeni potni številk”. Tematske so bile tudi že doslej obremenjene stroški. z “globo” 500.000,00 SIT na zvezek, kolikor nam V letu 2007 Strojniški vestnik za zdaj nima prispeva tudi Javna agencija za raziskovalno težav z izbiro vsebine. Gradiva iz preteklega leta, ki je dejavnost Republike Slovenije. Mogoče pa je tudi že prestalo recenzijski postopek ocenjevanja (1.01 namesto neposrednega plačila pridobiti sponzorska tudi v tujini) se ga je nabralo kar precej, tako da bomo sredstva za oglase v Strojniškem vestniku. Z anketo v letošnjem letu poleg “mešanih” objavili naslednja smo povprašali nove avtorje, ali sprejemajo to tematska zvezka z izbranimi ter dopolnjenimi prispevki obvezo, in večina nam je odgovorila pritrdilno. s konferenc TMCE’06 (Tools and Methods of Kot urednik sem sicer žalosten, saj bomo Competitive Engineering) in TMT 2006 (Trends in verjetno izgubili nekaj kakovostnih člankov. Nisem the Development of Machinery and Associated član Izdajateljskega sveta Strojniškega vestnika, Technology). prav tako tudi nisem zadolžen za finančno pokritje (poslovodni organ sta dekana obeh fakultet), kajti Urednik nihče mi ne daje možnosti vpliva na potek prilivov prof.dr. Andro AlujeviČ Osnutek (p)osebne znamke Pošte Slovenije d.o.o. 2 Uvodnik - Editorial Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 UDK - UDC 62-225.5:532.525 Kratki znanstveni prispevek - Short scientific paper (1.03) Vzporedni vplivi pospeška in površinskega ogrevanja na stisljiv tok: simulacija vesoljske pogonske šobe s srednje veliko površinsko obrabo Parallel Effects of Acceleration and Surface Heating on Compressible Flow: Simulation of an Aerospace Propulsion Nozzle with a Medium Amount of Surface Wear A. Alper Ozalp (Uludag University, Turkey) Numerične simulacije vesoljskih pogonskih šob so, zaradi nujnosti sočasnega obravnavanja pospeška toka, stopenj prenosa toplote, hrapavosti površine, temperaturno odvisnih lastnosti zraka in sprememb gostote tokovnic zaradi stisljivosti toka, zelo zapletene. Da bi zagotovili pregled za večstransko obravnavo toka pogonskih šob, smo razvili nov računski model, ki vključuje osnosimetrično zveznost, vztrajnostne in energijske enačbe. Izvedli smo računske preizkuse z različnimi geometrijskimi oblikami šob in vstopnimi robnimi pogoji ter s skupno obravnavo površinskega toplotnega toka in hrapavosti. Izračuni so pokazali, da se vstopna moč pogonske šobe in njene izgube povečujejo z večanjem notranjega statičnega tlaka ter zmanjšujejo z zoževalnim kotom šobe in površinskim toplotnim tokom. Ugotovili smo, da je razmerje izgub glede na vstopno moč neodvisno od toplotnega toka, vendar pa se linearno zmanjšuje s povečanjem zoževalnih kotov. © 2007 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: pogonske šobe, stisljivi tok, pretočni koeficient, izgube moči) Numerical simulations of aerospace propulsion nozzles are very complex due to the necessity to simultaneously handle flow acceleration, momentum heat-transfer rates, surface roughness, temperature-dependent air properties and streamwise density variations due to the compressible character of the flow. To provide an overview for a multitask consideration of the propulsion-nozzle flows, a new computational model that integrates the axi-symmetrical continuity, the momentum and the energy equations has been developed. Numerical experiments were performed with various nozzle geometries, inlet-boundary conditions, with the combined handling of the surface heat flux and roughness conditions. The computations indicated that the input and loss power values of the propulsion nozzle increase with higher inlet stagnation pressures and decrease with higher nozzle convergence half angles and surface heat flux. The ratio oj the loss to the input power was found to be independent of the heat flux; however, it decreases linearly with an increase in the convergence half angles. © 2007 Journal of Mechanical Engineering. All rights reserved. (Keywords: propulsion nozzle, compressible flow, discharge coefficient, power losses) 0 INTRODUCTION Compressible flows are encountered in a wide variety of engineering applications, e.g., the flow accelerator of environmental control systems in commercial aircraft [1] which supplies fresh air to the passenger cabins of aircraft and the exhaust system of nuclear propulsion engines [2], which generate energy and thrust. Most aerospace applications are equipped with nozzles such that the overall system performance is significantly influenced by the flow acceleration, the surface heating, the inlet conditions and the wear-based friction. Recent studies have pointed out the considerable influence of high pressures and temperatures on the frictional behaviours of nozzle flows. In spite of the objective, an accurate : 3 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 prediction in the design-oriented calculations of compressible flows is still a challenging task that is becoming increasingly important. The main design considerations for compressible-flow applications with nozzles are the flow geometries, the inlet-boundary conditions and the flow heat-transfer characteristics, where the performance predictions are reported by several experimental and numerical investigations. The effect of nozzle-exit over-pressure on vortex formation, with its contribution to nozzle thrust, was experimentally examined by Krueger and Gharib [3]. Significant losses in efficiency, due to heat transfer, especially when the ratio of the inlet stagnation to the back pressure converges to unity was determined by Lear et al. [4], who modelled the dissipative effects of heat transfer on the exit kinetic energy and the nozzle efficiency. Orieux et al. [5] illustrated the steady and transient performance of micro-nozzles for various nozzle geometries, ambient conditions and surface cooling, where the thrust values decreased both with cooling and with a narrower nozzle exit. The heat transfer and gas dynamics structure in a choked nozzle with cooling was experimentally investigated by Back et al. [6]. Instabilities in the propulsion of rockets, due to pressure and temperature fluctuations at the upstream of the rocket nozzle and due to the flow geometry, were numerically considered by Assovskii and Rashkovskii [7]. Bartz [8] handled the heat-transfer phenomena in compressible nozzle flows and considered the Nusselt number as a function of the inlet stagnation pressure and the convergence half angle, and Ahmad [9] correlated the variation of the nozzle discharge coefficients and surface heat-transfer values for various nozzle geometries. A 10o convergence half-angle nozzle with different working fluids and with a wide range of inlet stagnation pressures was experimentally considered by Massier et al. [10], who recorded lower discharge coefficients with a decrease in the inlet stagnation pressure. Paik et al. [11] studied the influence of flow geometry and Reynolds number on the variation of the discharge coefficients for sonic nozzles that are applied to gas flow-rate measurements, and reported higher discharge coefficients with an increase in the mass flow rate. Kim et al. [12] considered the effects of several kinds of gases and turbulence models with a wide range of Reynolds numbers on different sonic nozzle geometries. The combined effects of Reynolds number, area ratio and flow velocity on the critical pressure ratio of sonic nozzles were investigated by Park et al. [13]. Sato et al. [14] presented recent data on a real-time air-cooled propulsion ramjet engine. Ribault and Friedrich [15] investigated compressible flow behaviour along adiabatic and cooled walls by implementing the turbulent momentum and heat-transport analogies in a code. Although the available literature is highly concentrated on heating/cooling applications, inlet/ exit conditions and the geometrical structures of the nozzles, surface roughness (e) is becoming of major interest for compressible/incompressible nozzle flows. Gas-solid particle flows in the nozzles together with the high pressures and temperatures within the flow volume are the main sources of augmentations in the surface roughness. Kumar et al. [16] performed an experimental study of nozzle wear due to gassolid particle flow and determined an increase in the relative roughness (e/Din) values from 0.006 to 0.052. Bussiere and Mora [17] presented the real-time data of an Ariane 5 rocket-booster nozzle, where the relative roughness increased from a perfect surface finish to 0.012 during a flight that initiates with a launch and ends with the rocket in orbit. Although the surface roughness and the surface heat flux act simultaneously in real-time systems, the available literature deals with them separately. The combined effects have not yet been considered. To perform a comprehensive computational study, a new mathematical model, capable of implementing both the surface roughness and the surface heat flux (Q) conditions for aerospace propulsion nozzles was developed. Choked and un-choked cases were investigated for various convergence half angles (a), ratia of inlet stagnation to back pressure (b=(Po)in/Pb) and Q cases, and the proposed method was validated with the previous experimental and numerical reports. 1 MODELLING AND COMPUTATION The overall aim here is to build a predictive model for propulsion-nozzle flows in the presence of surface roughness and constant heat-flux conditions. The model should permit the determination of the necessary design parameters, such as the nozzle geometry and the inlet-boundary conditions for any given performance requirement depending on the applications. Thus, the main requirements are adaptability, simplicity and a short calculation time. The calculations rely on the principles of mass and en- 4 Ozalp A. A. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 Stagnant Air at (To). (PJ m s v 'in Fig. 1. Schematic outline of the aerospace propulsion nozzle ergy conservation and on the momentum and state equations applied to the control volume, given in Fig. 1. It is assumed that the stagnation conditions of pressure and temperature in the storage tank, upstream of the nozzle, are homogeneous and, as in many numerical studies [2] to [13], the air velocity, pressure and temperature are considered to be uniform across any section normal to the flow axis. Since air properties, like the specific heat at constant pressure (C ), the kinematic viscosity ( n) and the Prandtl number (Pr), are substantially dependent on temperature (T) [18], they are characterized by 6th-order polynomials with an uncertainty of less than 0.02%, and the temperature dependency is indicated by the superscript T throughout the formulation. As the study is focused on flows with friction and heat transfer, the stagnation pressure (P ) o and stagnation temperature (T ) values will also vary in the flow direction with the variation in the Mach number (M). Thus, the conventional equations (Eqs. 1 and 2) for compressible, isentropic and one-dimensional flows are applicable only with the simultaneous handling of the momentum and energy equations. ,P\ , 1+ Mi2 2 g -1 2 1+ Mi 2 m = riUiAi Ui=MigRTi P ri ( ReDn RTi UD (1) (2) (3) (4) (5) (6) The nodal values (subscript i) of the mass . flow rate ( m ) the air velocity (U) and the density (r) can be calculated using Eqs. 3 to 5, where the mass flow rate, the most significant consideration from a numerical point of view, is kept constant in the flow direction. On the other hand, the diameter (D), based the Reynolds number (Eq. 6), is assigned to each differential cell with the mean cellular values of U, D and n. The friction coefficient (f) is a function of both ReD and e (Eq. 7), and the cell-based (subscript n) shear stress (t) and friction force (Ff ) can be expressed with Eqs. 8 to 9. 1 -3.6 log 6.9 eD (ReD)n { 3.7 r (^ (7) (8) (9) (Ff)n =tnp DnDxn The one-dimensional momentum (Eq. 10) and energy equations (Eq. 11) are applied to each differential cell in the nozzle, where the nodal properties, such as P, U and Cp, are interrelated with the contributions of cellular variants like Ff and the impulse (I). Eq. 11 represents the conservation of mechanical and thermal energy by the implementation of a cell-based surface flux and the frictional loss term. (10) Pi Ai +m. Ui = Pi+1 Ai+1 +m. Ui+1 +(Ff )n + In ()i U22 Q(As ) ()i +1 U22 (Ff )U n CPT Ti+ i + . n =CPT Ti+1+ i+1+ n m (11) Vargas and Bejan [1] evaluated heat-transfer data in their mathematical model for a compressible nozzle flow, where the Mach number was in the range Vzporedni vplivi pospeška in površinskega ogrevanja - Parallel Effects of Acceleration and Surface Heating 5 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 tion data (P , T ), were calculated at the nodes of these cells, which are numbered from i=1 to n+1, whereas r, I, ReD and NuD were evaluated on a cell basis using the mean values of nodal inlet and exit data of each cell. As shown in Fig. 2, by disregarding the surface roughness and heat transfer, the flow of the solution logic first handles the problem as an isentropic type, which is manipulated as described by Laney [20]. The M value of the isentropic approach is the initial guess of the iterative solution procedure of the non-isentropic nozzle flow. The non-isentropic approach governs the complete equation set described above; however, if the solution scheme encounters singularities, like M>1, M =1 i ex & P

0.3 m (a=9o) is due to the higher acceleration rates of the flowing air, which can also be seen in Fig. 3. The streamwise variations of the fluid (Tf ) and surface (Ts) temperatures are presented in Fig. 5. As a consequence of the applied surface heat flux, the Ts values are above Tf for the complete a and b ranges and also throughout the flow volume. On the other hand, as the Ts values decrease in the streamwise direction, the opposite is true for Tf in all cases. The decrease rates of Ts become more significant towards the nozzle exit, especially for x>0.45 m, where the highest flow acceleration is determined for all the nozzles. Lower b and higher a indicates lower mass flow rates, which constitutes higher Ts and Tf, especially at the nozzle inlet. The durability of the nozzle material is directly related to the Ts, and the computations suggest the upstream nozzle sections should be carefully considered. On the other hand, surface wear is connected with Tf, and the vital regions appear towards the downstream regions of the nozzle, specifically at the exit plane. Fig. 6 presents the streamwise variations of surface heat-transfer rates for various convergence-half-angle and pressure-ratio cases, with the application of constant surface heat-flux values of 800 and 1600 kW/m2. The Nusselt numbers (NuD) were observed to increase in the flow direction for the complete set of investigated systems; however, a and Q appeared to cause the NuD to decrease in both the choked (b=2.00) and un-choked (b<2.00) cases. This outcome is highly dependent on the fact that narrower nozzles and higher heat-flux values contributed to lower mass flow rate values (Fig. 3), and thus M and U, which also decrease the amount of heat swept from the nozzle wall. On the other hand, the ratio of the exit to inlet Nusselt numbers l=(NuD)ex/(NuD)in increases with b and a, whereas it decreases with Q. Bartz [8] also reported increased l ratia with higher a and b; moreover, the typical report of Ahmad [9] for a nozzle with a=45o is l=3.9. The most significant ratio, evaluated in the present Fig. 4. Streamwise variation of non-dimensional pressure with various a, b and Q conditions 8 Ozalp A. A. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 i kW/ii]2 — •:!;-. *:TS ).(Q = 1600 kW/m2 Fig. 5. Streamwise variation of flow and surface temperature with various a, ß and Q conditions kW/m2. Fig. 6. Streamwise variation of Nusselt number with various a, ß and Q conditions paper for the choking case of c=9o, is /1=2.70, and this is higher than the corresponding report of Back et al. [6] (/1=1.61) for the nozzle with c=15o. Fig. 6 further suggests that the application of different heat-flux values causes NuD to vary both at the inlet and exit planes of the nozzle. The most significant variations are recorded for the y?case of 1.01 for the complete a set, where these intervals are ±9.4% (inlet) and ±19.8% (exit) for o=3o and ±11.8% (inlet) and ±28.1% (exit) for the a=9o case. These values additionally imply that the effect of the wall’s heat flux on surface heat-transfer rates becomes more significant in higher a cases, and thus in tasks with lower mass flow rates. The combined effects of a, ReD and Q conditions on the discharge coefficient is given in Fig. 7a for the choked case of ß=2.00. It can be seen from Fig. 7a that the isentropic values are not only in agreement with the ISO 9300 (Paik et al. [11]) standardized correlation of C=f((ReD )J for choked nozzles but also with the experimental reports of Massier et al. [10] and Kim et al. [12]. A higher «produced a lower exit ReD, where the lower ReD and higher Q are accompanied by reduced values of Cd and point to lower mass flow rates, which show parallelism with the Mach-number variations of Fig. 3 and are similar to the reports of Paik et al. [11]. C = 0.2636+ 4.6279-10"2 ln ( Re„)„ (14) (15) Q=r1.0106 + 0.0074(lna)2 The adiabatic (g=0) correlations (Eqs. 14 and 15) of Ahmad [9] produce higher Cd values for the present a and ReD intervals; the gap is the outcome of the applied heat flux values; however, the gap decreases with lower a and with higher (ReJ^ values. The numerical results show, particularly for the ß=1600 kW/m2 case, that the nozzles of o=3o, 6o, 9o result in Rvalues of 0.935, 0.933 and 0.93 respectively, where Kim et al. [12] also reported a lower Cd with higher convergence half angles. The input power ( f) necessary to form the compressible flow within the nozzle and the amount of power loss ( flo) are the main considerations from the point of view" of the energy requirements to run the propulsion nozzles. Fig. 7(b) demonstrates that both fand ^ increase with higher y?and lower a, which indicates that the amount of air directed towards the nozzle is the characteristic design parameter. Increasing the surface heat flux from 800 to 1600 kW/m2 caused a decrease in >Fby 2.7% for all a Vzporedni vplivi pospeška in površinskega ogrevanja - Parallel Effects of Acceleration and Surface Heating 9 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 kW/m2 kW/in2, Q,=16Ô0 kW/m rlsentropic Cases) (a) (b) Fig. 7. Variation of (a) discharge coefficient for the choked flow and (b) input and loss power values with various a, b and Q conditions values with b=2.00, where this influence is slightly lower than the Cd gap among the identical cases shown in Fig. 7a. However, the effect of Q on Yloss definitely varies with a; as the decrease rate for a=3o is 2.9% the corresponding values for a=6o and a=9o are 1.4% and 0.8%, respectively. Since the main source of Yloss is Ff (Eq. 9), Fig. 7b further suggests that Q also has an opposite effect on Ff, which is in agreement with the reports of Ribault and Friedrich [15], who determined higher friction-coefficient values (Eq. 7) with surface cooling. Lastly, the Yloss/Y ratio is dependent on both a and b and appears to be independent of Q: for b=1.01 the ratio is equal to 0.03% for the complete a set, whereas for b=2.00 the ratio exhibits a linear style and has values of 1.3%, 1.1% and 0.9% for a of 3o, 6o and 9o, respectively. 3 CONCLUSION A computational method for an investigation of compressible flow and heat-transfer characteristics in aerospace propulsion nozzles was developed. The model is capable of handling various flow geometries and inlet-boundary conditions, together with the simultaneous application of surface heating and roughness conditions. The main conclusions from the numerical experiments can be summarized as follows: Surface heating produces lower inlet Mach numbers but higher inlet non-dimensional pressure values; moreover, the effect of Q on both of the values is more apparent in flows with lower acceleration. The heat flux, especially in cases with high acceleration, directly increases the stagnation pressure and causes augmented static pressure values, which is remarkable from the point of view of surface wear and system damage, specifically for the nozzle section of 0.25 to 0.40 m. Moreover, the point of maximum shifts downstream in the flows with lower b and a reduced mass flow rate. The Nusselt numbers decrease with lower inlet stagnation pressures and with higher convergence half angles and heat-flux conditions; moreover, the effect of surface heat flux on the Nusselt numbers is more apparent in un-choked flows. The maximum values of Ts are recorded in the downstream nozzle sections, which is the very important for the nozzle material; and the decrease rates of Ts become significant towards the nozzle exit, especially for x>0.45 m, where the highest flow acceleration is determined for all the nozzle geometries. The augmentation of Tf in the flow direction is accompanied by the energy-transfer mechanism and also with the contribution of a lower Ts, and labels the exit-plane neighbourhood as vital from the point of view of wear. 4 NOMENCLATURE A cross-sectional area, m2 Ff frictional force, N Cd discharge coefficient I thrust, N Cp specific heat at constant pressure, J/kgK L nozzle length, m D nozzle diameter, mm m mass flow rate, kg/s f skin friction factor M Mach number 10 Ozalp A. A. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 Nud Nusselt number n kinematic viscosity, m2/s P pressure, Pa r density, kg/m3 Pr Prandtl number t shear stress, Pa Q surface heat flux, W/m2 Y power, kW R gas constant, J/kgK ReD Reynolds number Subscripts T temperature, K b, o back, stagnation U air velocity, m/s D diameter X streamwise direction, m ex, in exit, inlet i, n node, cell number Greek Letters loss loss power a convergence half angle, deg s heat-transfer surface b ratio of the inlet stagnation to the back pressure Superscripts e surface roughness, mm T temperature dependency g specific heat ratio __ cellular average 5 REFERENCES [I] Vargas, J.V.C., A. Bejan (2001) Thermodynamic optimization of finned crossflow heat exchangers for aircraft environmental control systems. Int J Heat Fluid Flow 22(2001), pp. 657-665. [2] Kammash, T., T. Godfroy (1997) An open cycle gas core fusion rocket for space exploration. Acta Astronautica 41(1997), pp. 229-237. [3] Krueger, P.S., M. Gharib (2003) The significance of vortex ring formation to the impulse and thrust of a starting jet. Physics of Fluids 15(2003), pp. 1271-1281. [4] Lear, W.E., S.A. Sherif, J.R. Langford (1997) Efficiency and gas dynamics analysis of two-phase mixtures in supersonic nozzles with inter-phase heat transfer and slip. Acta Astronautica 40(1997), pp. 701-706. [5] Orieux, S., C. Rossi, D. Esteve (2002) Compact model based on a lumped parameter approach for the prediction of solid propellant micro-rocket performance. Sensors and Actuators A-Physical 101(2002), pp. 383-391. [6] Back, L.H., P.F. Massier, R.F. Cuffel (1996) Some observations on reduction of turbulent boundary-layer heat transfer in nozzle. AIAA Journal 4(1996), pp. 2226-2229. [7] Assovskii, I.G., S.A. Rashkovskii (2001) Low-frequency instability of solid rocket motors: Influence of the Mach effect and charge geometry. Combustion, Explosion and Shock Waves 37(2001), pp. 321-330. [8] Bartz, D.R. (1957) A simple equation for rapid estimation of rocket nozzle convective heat transfer coefficients. Jet Propulsion 27(1957), pp. 49-51. [9] Ahmad, R.A. (2001) Discharge coefficients and heat transfer for axisymmetric supersonic nozzles. Heat Transfer Engineering 22(2001), pp. 40-61. [10] Massier, P.F., L.H. Back, M.B. Noel, F. Saheli (1970) Viscous effects on the flow coefficient for supersonic nozzle. AIAA Journal 8(1970), pp. 605-607. [II] Paik, J.S., K.A. Park, J.T. Park (2000) Inter-laboratory comparison of sonic nozzles at KRISS. Flow Measurement and Instrumentation 11(2000), pp. 339-344. [12] Kim, H.D., J.H. Kim, K.A. Park, T. Setoguchi, S. Matsuo (2003) Computational study of the gas flow through a critical nozzle. Proc Instn Mech Engrs Part C: J Mech Eng Sci 217(2003), pp. 1179-1189. [13] Park, K.A., Y.M. Choi, H.M. Choi, T.S. Cha, B.H. Yoon (2001) The evaluation of critical pressure ratios of sonic nozzles at low Reynolds numbers. Flow Measurement and Instrumentation 12(2001), pp. 37-41. [14] S ato, T., N. Tanatusgu, Y. Naruo, T. Kashiwagi, J. Omi, J. Tomike, T. Nishino (2000) Development study on ATREX engine. Acta Astronautica 47(2000), pp. 799-808. [15] Ribault, C.L., R. Friedrich (1997) Investigation of transport equations for turbulent heat fluxes in compressible flows. Int J Heat Mass Trans 40(1997), pp. 2721-2738. Vzporedni vplivi pospeška in površinskega ogrevanja - Parallel Effects of Acceleration and Surface Heating 11 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 3-12 [16] Kumar, R., A.P. Verma, G.K. Lal (1983) Nozzle wear during the flow of a gas-particle mixture. Wear 91(1983), pp. 33-43. [17] Bussiere, M., B. Mora (1994) Ariane 5 booster nozzle: components description and dimensioning. Acta Astronautica 34(1994), pp. 83-89. [18] Incropera, F.P., D.P. De Witt (1990) Fundamentals of heat and mass transfer. John Wiley & Sons, New York. [19] Chapra, S.C., R.P. Canale (1990) Numerical methods for engineers. McGraw Hill, Singapore. [20] Laney, C.B. (1998) Computational gasdynamics. Cambridge University Press, Cambridge. [21] Wu , J.S., K.C. Tseng (2001) Analysis of micro-scale gas flows with pressure boundaries using direct simulation Monte Carlo method. Computers and Fluids 30(2001), pp. 711-735. Author’s Address: Prof. Dr. A. Alper Ozalp Uludag University Department of Mechanical Eng. 16059 Gorukle, Bursa, Turkey aozalp@uludag.edu.tr Prejeto: Sprejeto: Odprto za diskusijo: 1 leto 27.4.2005 25.10.2006 Received: Accepted: Open for discussion: 1 year 12 Ozalp A. A. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 13-17 UDK - UDC 621.894:539.4 Kratki znanstveni prispevek - Short scientific paper (1.03) Določitev tornega količnika v brazdah z napetostno funkcijo Determination of the Friction Coefficient of Groove Forms Using the Stress-Function Method C. Erdem Imrak - Ismail Gerdemeli (Istanbul Technical University, Turkey) Največja sila trenja, ki lahko nastane v brazdah, je funkcija dejanskega tornega količnika med vrvjo in brazdo. Tomi količnik je predstavljen na različne načina za vsako vrsto oblike brazde. V prispevku je prikazan obrazec za porazdelitev tlaka na stični površini okrogle in/ali brazde v obliki črke U. Z metodo napetostne funkcije smo določili tudi torni količnik brazd. © 2007 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: žleb na obodu koluta, torni količnik, napetostne funkcije) The maximum traction that can be developed in sheave grooves is a function of the actual coefficient of friction between the rope and the groove. The coefficient of friction is presented in different ways for every type of groove form. In this paper an expression for the pressure distribution on the contact surface of round and/or U-shaped groves is obtained, and the friction coefficient of the groove forms is determined by the stress-function method. © 2007 Journal of Mechanical Engineering. All rights reserved. (Keywords: rope groove, friction coefficient, stress function method) 0 INTRODUCTION Driving sheaves are widely employed to transmit power to the ropes that drive elevators, cable cars, funiculars, etc. The groove form favourably increases the effective coefficient of friction between the rope and the groove at the expense of increasing the pressure and wear on the groove surface. The trade off between the traction produced and the pressure causing the abrasion of the groove may be best explained by the concept of shape factors for the coefficient of friction of U-shaped grooves. During normal operations sheave and drum grooves are under constant pressure. The groove form affects the magnitude of the tractive force on the driving sheaves for power transmission. The contact area between the rope and the groove is smaller with U-shaped grooves than with round grooves since the rope loses contact with the groove where the undercut is machined. Thus an undercut groove provides a tighter grip- ping action due to an increased groove pressure, and its traction capability is greater than that of a round groove. However, a round groove has a longer rope life and a lower level of noise because of the lower groove pressure at high speeds. When the problem of insufficient traction arises with a round groove it should be noted that it can be overcome by increasing the angle of wrap, by changing the groove form to a U-shaped groove with an appropriate shape or by using a material with a higher coefficient of friction [1]. The U-shaped groove sheave, found predominantly in older installations, is the sheave of choice for optimum rope life. Its large size, when compared with the drive sheave diameters in newer installations, in combination with its supportive grooves minimizes the amount of abrasion and fatigue. The support given to the rope by the groove is illustrated in Fig.1. The groove cradles the rope, resulting in low groove pressures that allow the wires and strands to move about freely while the rope is 13 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 13-17 Fig.1. The U-shaped groove form operating. Also important to the U-shaped groove’s success in achieving excellent rope life is the relative diameter of the sheave required to maintain traction. In general, an undercut U groove, a modern type of groove, increases the traction by increasing the groove pressures. The beauty of these groove types is that the diameter of the sheave utilizing this modern groove design can be reduced. The maximum traction that can be developed in the sheave grooves is a function of the effective coefficient of friction between the rope and the groove and the angle of contact that the rope makes with the circumference of the sheave (known as the angle of wrap). The groove form can favourably increase the effective coefficient of friction between the rope and the groove since the radial force due to the rope tension produces greater normal and frictional forces acting along the area of contact given by the shape of the groove [2]. Airy introduced his stress function as a device for solving certain problems in linear elastostatics for homogenous isotropic bodies. There are many published studies on the Airy stress function applied to solid mechanics ([3] to [10]). In this paper, to obtain the pressure distribution on the contact surface of undercut groves, the Airy stress-function method was used. The effects of the groove geometry and the angle of wrap on the traction were investigated and tabulated with the ratio of the forces for different angle values by Imrak and Ozkirim [1]. In this paper the application of the Airy stress-function method for determining the shape factors for the coefficient of friction for both round and undercut grooves is presented. The effect of the changes in the groove angle and the undercut- ting angle on the coefficient of friction and the traction are also studied. 1 BASIC EQUATIONS Due to the existence of axial symmetry related to the geometry and specific pressure distribution along the boundary of a U-shaped groove it is preferable to employ polar coordinates rather than the Cartesian system and to assume that the stress condition is one of plane stress. The geometry and the loading of an undercut groove are illustrated in Fig. 1. The angle of the outer normal lines of the contact area cîmay have a maximum value 180°; the angle of the undercutting y?must not be greater than 105°, as shown in Fig. 1. Due to the normal force and the symmetrical loading in the traction drive, only the plane stress is employed. In the plane-stress state the following relations are valid as long as the mass forces are negligible. By plugging in the equations associated with Airy’s stress function into the equilibrium condition we can illustrate that the functions do indeed satisfy the equilibrium. The Airy function is chosen so as to satisfy the equilibrium equations automatically. The equation of compatibility, which means that the body must be physically pieced together in terms of Airy’s stress function, is [11]: [dr 2 r1dip2 r dr){dr 2 r 2 dip r dr) (1) where V2 is the Laplace operator. The Airy stress function is developed and used to solve classic two-dimensional problems fundamental to stress analysis. The Airy stress-function approach works best 14 Imrak C. E. - Gerdemeli I. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 13-17 for problems where a solid is subjected to prescribed tractions on its boundary, rather than prescribed displacements [8]. Using symmetrical straining we obtain d/dr = d/dr. Therefore, Eq.(1) becomes: d (1 dip) 1 dip 1 a2 dr ±±\\a!ž r dr l\ dr2 1 df r dr (2). Thus, the solution reduces to finding a solution of the differential equation of compatibility that satisfies the boundary conditions of the problem. To obtain a solution of these two equations, one can write an arbitrary function f = f (r,j). This arbitrary function is called the Airy stress function [12]. In the case of plane stress and in the event that the body forces are negligible the differential equations of equilibrium in polar coordinates are as follows: dt2 aY dr2 d2 drdt (3) and the boundary conditions are a = p, a = 0, and r = 0. dt = r sin dip * r rfp with respect to the radial derivative. If the second derivative is evaluated in the tangential direction, we advance in the r direction by dr, then the angular change is d _ „ dr rdip r (4). 1 dg> dr 2r _ r dtp dr r The usual method for solving these equations is by introducing a single new function = (r,ç), commonly known as Airy’s stress function, which satisfies Eqs. (4) and is related to the stresses as follows: ar r 2dç2 rdr ^ dr 2 (5). d (1 d = T7 r dip r dr r dr 0 0 , 2 (6). dr\r dip J r dip r drdip The radial force distribution F per unit length Y along the circumference of the sheave, induced by the tangential rope tension S, is: dN(= Sdip) 2S (7), Fr D dj 2 D where D is the pitch diameter of the sheave. The boundary conditions along the area of contact, for r = d/2, in the radial plane at an angle of a are expressed by: n -dN = —Fr — da = 2 \ 2 (8), where r. is the distance of the ;-th sound source from the field-sound source point of the rolling-stock cabin under consideration; Q = 4^ for spherical sound radiation, and f2= 2n for semi-spherical sound radiation (semi-spherical sound radiation will be for H - v= 30 km/h lr--=90 km/h <- v= 120 km/h 31.5 63 125 250 500 1000 f,Hz Fig. 9. Change of sound level in the cabin of the M62 locomotive driving at 30 to 120 km/h Numerično modeliranje notranjih zvokov - Numerical Modelling of the Internal Noise 23 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 18-25 c) Fig. 10. Change of the sound level [db], when the excitation frequency is: a) 125 Hz; b) 500 Hz; c) 1000 Hz islated levels by 5 to 25 dB. The main sources 2. The highest sound level in the control cabin of of sound pollution, such as the main and additional power aggregates, the road-wheel interaction, the braking equipment, and the soundisolation equipment, have a mechanical character. the TEP60 passenger locomotive is 106 dB; in the M62 locomotive it is 106 dB, in the machine section of the TEP60 locomotive it is 120 dB, and in the M60 locomotive it is 125 dB in the 31.5 to 250 Hz range of sound frequencies. 5 REFERENCES [1] [2] [3] [4] [5] [6] [7] Steel J. A. (1998) A study of engine sound transmission using statistical energy analysis. J. of Automobile Engineering, vol.212, part D , 205-213. Wunderli J. M. (2005) A measurement procedure for the sound emission of railway sources including source separation. J. Rail and Rapid Transit, vol.219, part F, 125-137. Bazaras Ž., Leonavičius M. (2005) Simulating the lateral vibrations of passenger wagons. Strojniški vestnik, vol.51, No6/05, 346-355. A study of European priorities and strategies for railway noise abatement (2002) Final Report. Gelezinkeliu bendradarbiavimo organizacija OSZD (2001) Gelezinkeliu transporto keliamo triuksmo poveikio aplinkai vertinimo rekomendacijos,Vilnius. Bausys R. (1999) Quality assessed solutions in acoustic analysis . J. Mechanika Nr.1(16) 1999, 39-43. CnpaBOHHiiK no 3JieKTpono/iBii5KHOMy cocTaBy TeiuiOBoaaM ii /ui3ejn>-noe3/iaM. new o6m. pea. A. H. TiimeHKO. T.2. Tpaucnopm, MocKBa (1976) 24 Bazaras J. - Bazaras Ž - Sapragonas J. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 18-25 [8] AKycTiiKa: CnpaBOHHiiK (1989) A. IL Ehmob, A. B. Hhkohob, M. A.Cano5KKOB, B. H. IIIopoB; no/rpe/i. M. A. Cano5KKOBa. Paduo u cexsb. MocKBa,. - 336 c. [9] Koo D.H., Kim J.C., Yoo W.H., Park T.W. (2002) An experimental study of the effect of low-sound wheels in reducing sound and vibration. Transportation Reasearch Part D 7, 429-439. [10] Bazaras Ž., Ramanauskas M., Ilgakojis P. (2002) Triukšmo modeliavimas lokomotyve. Tarptautinës konferencijos ,,Transporto priemonës-2002” pranesimumedziaga. Technologija Kaunas, Lithuania. [11] Thompson D.J., Jones C.J.C. (2000) A review of the modelling of wheel/rail sound generation J.Sound Vibration., vol.231(3), 519-536. [12] Hardy A.E.J. (1999) Noise from railway bridges. J. Rail and Rapid Transit. ISSN 0954-4097, 1999, vol.213, part. F, 161-172. [13] Hardy A.E.J. (1999) Noise from railway bridges . J. Rail and Rapid Transit, vol. 213, part F,173-180. [14] Cervello S., Donzella G., Pola A., Scepi M. (2001) J. Rail and Rapid Transit. ISSN 0954-4097, vol. 215, part F, 179-192. Authors’ Address: Mag. Jonas Bazaras Prof. Dr. Žilvinas Bazaras Prof. Dr. Jonas Sapragonas Department of Transport Engineering Kaunas University of Technology Kestucio str. 27 LT-44025 Kaunas-4, Lithuania jonasB1@one.lt zilvinas.bazaras@ktu.lt jonas.sapragonas@ktu.lt Prejeto: Sprejeto: Odprto za diskusijo: 1 leto 4.1.2006 22.6.2006 Received: Accepted: Open for discussion: 1 year Numerično modeliranje notranjih zvokov - Numerical Modelling of the Internal Noise 25 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 UDK - UDC 62-23:681.892 Strokovni članek - Speciality paper (1.04) Teoretična in eksperimentalna analiza dinamike mehanizmov Rolamite A Theoretical and Experimental Investigation of the Dynamics of Rolamite-Type Mechanisms Ričardas Viktoras Ulozas (Šiauliai University, Lithuania) Prispevek najprej poroča o teoretični raziskavi dinamičnega modela valja in jermena pri mehanizmu tipa Rolamite (RTM). Dinamični model valja in jermena mehanizma RTM je opisan z diferencialnimi enačbami ter analiziran na dva načina, tj. v primeru, ko na sistem ne vpliva vibracijsko vzbujanje, in v primeru, ko leto vpliva na sistem. Ugotovili smo, da je mogoče s parametri vibracijskega vzbujanja spreminjati parametre nezdrsnega območja. To nas je vodilo do predpostavke, da je v dejanskih mehanizmih tipa Rolamite mogoče vplivati na trenje med strukturnimi elementi mehanizma RTM. Eksperimentalni del raziskave dinamike mehanizma tipa Rolamite z vibrajočimi elementi je bil izveden v treh smereh: kot analiza dinamičnih pojavov v mehanizmu valja in jermena, kot analiza postopkov obvladovanja trenja med elementi mehanizma RTM in kot analiza dinamičnih pojavov v vibramotorjih Rolamite. Povečanje amplitude električne napetosti, zmanjšanje sile obremenitve gibkega jermena, in zmanjšanje kota, pod katerim gibki jermen ovija valj, povzročijo povečanje amplitude vibracij valjev. Mehanizem RTM z vrtečima se in vibrajočima valjema ima v primerjavi z vibrajočima valjema drugačnega tipa boljšo ležajno zmogljivost in je precej bolj občutljiv. Največjo sinhronost vrtenja rotorjev zagotavlja vibramotor Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki hkrati vrti oba rotorja. Ta vibramotor primerjamo z vibramotorjem Rolamite z dvema rotorjema in piezo električnim pretvornikom vibracij, ki vrti le enega od rotorjev. © 2007 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: Rolamite mehanizmi, zdrsavanje, vibracije, dinamični modeli) This paper looks at theoretical research of the dynamic model of the "roller-band" system of the Rolamite-type mechanism (RTM). The dynamic model of the "roller-band" system of the RTM is described by differential equations and is investigated in two ways, i.e., when the system is not influenced by the excitation of vibrations, and when it is influenced by them. We have established that with the parameters of excitation of vibration it is possible to operate the parameters of a non-slipping zone. This allows us to assume that in a real Rolamite-type mechanism it is possible to operate on the friction between the structural elements of the RTM. Experimental research on the dynamics of the Rolamite-type mechanism with vibrating elements was done in three directions: research on the dynamic processes running in the RTM roller-band system; research on the processes of friction-control between the elements of the RTM; and research on the dynamic processes running in the Rolamite vibromotors. The increase of the supply-voltage amplitude, the decrease of the force-load magnitude of the flexible band, and the decrease of the angle of the wrapping of the roller by the flexible band cause an increase in the amplitude of the roller vibrations. An RTM with rotating vibrating rollers, compared with the vibrating rollers of the other type, has a better bearing capacity and is much more sensitive. The highest synchronicity of rotation of the rotors is provided by a Rolamite vibromotor with two rotors and a piezoelectric converter of vibrations that simultaneously rotates both rotors. This is compared with the Rolamite vibromotor with two rotors and a piezoelectric converter of vibrations, which rotates only one rotor. © 2007 Journal of Mechanical Engineering. All rights reserved. (Keywords: Rolamite type mechanisms, slipping, vibrations, dynamic models) 26 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 OUVOD Donald F. Wilkes je izumil kotalni mehanizem tipa Rolamite (RTM) v letu 1967 ([1] in [2]). Pri mehanizmu RTM se valja brez trenja kotalita po jermenu, vendar pa avtorji [3] tudi navajajo, da valja pri določenih parametrih mehanizma zdrsneta, čeprav ne podajo nikakršne teoretične podlage za ta pojav. V viru [4] sta navedeni dve vrsti zdrsa mehanizma RTM (geometrični in vzmetni zdrs). Raziskovalci so predlagali, da bi trenje zmanjšali z uporabo vibracij [5]. Ena izmed metod za zmanjšanje trenja temelji na rabi usmerjevalnih vibracij, ki jih dovajamo stičnim telesom. Če se vibracijska amplituda vibrajočih elementov med stičnima telesoma povečuje, se pojavi plast vibracij (FV). Mehanizem nastanka plasti vibracij je temeljito opisan v viru [6], zato tu ne bo podrobno opisan. Najpogosteje uporabljeni sestavni deli vibrajočih elementov mehanizma RTM so piezoelektrični pretvorniki, tj. piezo keramični elementi. Pri mnogih konstrukcijah mehanizma RTM le-ti tvorijo dele valjev, ki imajo osi pritrjene na nepremično osnovo. Okrov mehanizma RTM se giblje premočrtno pod vplivom zunanjih sil ali sil, ki jih ustvarja kinematično delovanje valjev in jermena. Pri takšnem mehanizmu valja opravljata funkcijo vibracijske podpore (VS) ali vibramotorja (VM) [7]. Ko načrtujemo precizni mehanizem RTM z nadzorovanim trenjem za določitev ali krmiljenje napetosti gibkega jermena kakor tudi natančni mehanizem vlečnega jermena z vibramotorjem Rolamite (RVM), moramo teoretično in eksperimentalno raziskati dinamične pojave, ki potekajo v mehanizmu RTM in vibramotorju. Vibramotorje lahko v mehanizmu RTM uporabimo kot vibracijsko podporo usmerjevalnemu gibanju, mehanizmu vlečnega jermena, črevesni črpalki, mikro vpenjalni čeljusti, idr. Namen teoretične raziskave je razkritje razmer, v katerih se valja in jermen mehanizma RTM gibljejo sinhrono in brez zdrsov, saj je poznavanje teh razmer bistvenega pomena pri oblikovanju natančnega mehanizma. Drugi namen raziskave pa je analiza mehanizma RTM, ki je izpostavljen vplivu vibracij. Namen eksperimentalnega dela raziskave je seznanitev z dinamičnimi pojavi v mehanizmu valjev in jermena, analiza možnosti krmiljenja trenja 0 INTRODUCTION Donald F. Wilkes invented the Rolamite-type mechanism (RTM) in 1967 ([1] and [2]). In the RTM the rollers are rolling on the band without friction; however, the authors of [3] specify that the rollers slip for certain parameters of the mechanism, although they do not provide any theoretical substantiation for this. In [4] two variants of slipping in the Rolamite-type mechanism (geometric and springy slipping) are defined. Researchers have suggested that the friction could be decreased using vibrations [5]. One of the methods to reduce friction is to provide directional vibrations to the contact bodies. If the vibrational amplitude of the vibrating elements is increasing between the interacting bodies a film of vibrations (FV) occurs. The mechanism of the FV’s formation is comprehensively described in [6], thus we will not describe it in detail here. The most frequently used constituent parts of the RTM’s vibrating elements are piezoelectric converters i.e., piezoceramic elements. In many RTM constructions they form part of the rollers that have their axes fixed to the immobile base. The casing of the RTM under external forces or forces arising in the kinematic roller-band pair performs a rectilinear movement. The rollers of such an RTM perform the functions of vibrosupport (VS) or vibromotors (VM) [7]. When designing precision Rolamite mechanisms with controlled friction for positioning or regulating the tension of the flexible band, as well as precision band-pulling mechanisms with a Rolamite vibromotor (RVM), the dynamic processes taking place in the RTM and RVM have to be explored both theoretically and experimentally. Vibromotors may be used in a RTM as the vibrosupport of the directional movement, band-pulling mechanisms, peristaltic pumps, micro-manipulator grips, etc. The purpose of theoretical research is to reveal the conditions under which the bodies of the roller-band of an RTM are moving synchronically without slipping, because their detection is the most important problem in the design of precision mechanisms. The other purpose is to investigate the RTM that is influenced by vibrations. The purpose of experimental research is to explore the dynamic processes in the RTM rollerband system; to explore the possibilities of control- 27 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 mehanizma RTM ter analiza dinamičnih pojavov v vibramotorjih. Predmeti ekperimentiranja so izvirni mehanizmi RTM, pri katerih sta valja vzbujena z visokofrekvenčnim vibriranjem, ter vibramotor, čigar delovanje je utemeljeno na visokofrekvenčnih diagonalnih udarcih piezokeramične plošče ob vrteči se rotor. 1 DINAMIČNI MODELI VALJEV IN JERMENA PRI MEHANIZMU RTM ling the friction of the Rolamite mechanisms; and to explore the dynamic processes in Rolamite vibromotors. The objects of the experiments are the original RTM, where the rollers are induced by high-frequency vibration, and the RVM, where the functioning is based on high-frequency diagonal hits by the piezoceramic plate onto the rotor that is rotating. 1 DYNAMIC MODELS OF THE ROLLER-BAND SYSTEM OF AN RTM Dinamični modeli sklopa valjev in jermena pri mehanizmu RTM v primeru deformiranih in nedeformiranih stikov med telesi (si. 1) so opisani z deferencialnimi enačbami in analizirani. Slika 1 kaže, da so z (i - 1 do 6) pomiki elementov (v pravokotni in stri izni smeri), P 1 je vlečna sila, P6 je sila odpora gibanju, P4 je sila, ki pritiska maso m ob maso M (in povzroča pravokotno tlačno silo N). Jermen opišemo z dvojicami parametrov. V sredini stičnega predela med valjem in jermenom je zgoščena masa jermena m, preostali del jermena pa je v vzdolžni smeri spremenjen v elastični element c12 in razsipni element H12, ki sta povezana vzporedno. Masa jermena m je zbrana vzdolž površine valja. Valj je izražen kot telo z maso M. Medsebojno delovanje jermena in valja je prikazano s prej omenjeno zgoščenje mase m ter s primerno povezavo elastičnih elementov c23, c45 in razsipnih elementov H23, H45, ti omogočajo deformacije jermena, ki se dotika valja v strižni in pravokotni smeri. Zgoščena masa se deloma nanaša na maso m in deloma na maso mv ki je zbrana neposredno na površini valja in pridobljena s telesom, ki ima maso M. Dynamic models of the roller-band system of an RTM in the cases of deformed and non-deformed contact between the bodies (Fig. 1) were described by differential equations and investigated. It is shown in Fig. 1 that zi (i – 1 to 6) are the displacements of the elrements (in the normal rand tangential directions), P1 is the pulling force, P6 is r the force of the resistance to movement, P4 is the force that is pressing the mass m to mass M (causing the normal pressing force N). The band is represented by coupled parameters. In the center of the contact zone between the roller and the band is concentrated the band’s reduced mass m, the remaining piece of the band in a longitudinal direction is changed to the elastic element c12 and the dissipative element H12, connected in parallel. The mass of the band m is concentrated along the roller’s surface. The roller is expressed as a body with the mass M. The interaction of a band with a roller is shown by means of the above-mentioned reduced mass m, and connecting in appropriate way the elastic c23, c45 and dissipative H23, H45 elements, which allow deformations of the band contacting the roller in the tangential and normal directions. The part of the reduced mass of the band relates to the mass m h h SI. 1. Dinamična modela valja in jermena pri mehanizmu RTM v primeru stika med telesoma: a - deformirani stik, b - nedeformirani stik Fig. 1.Dynamic models of the roller-band system of the RTM in the case of a contact between bodies: a - deformed, b - non-deformed 28 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 Deformacija stika med jermenom in obema valjema je mogoča zaradi elastičnih in razsipnih elementov c2V c45, H2V H45 ter tudi zaradi mase my Analiziran je primer neprekinjenega gibanja mas m in M v pravokotni smeri. Poenostavljeni dinamični model natančnega mehanizma valja in jermena, kakršnega poznamo pri sistemu RTM, je opisan z diferencialnimi enačbami in analiziran. V skladu s sliko la imajo diferencialne enačbe gibanja naslednje izraze: and the part to mass m3, concentrated directly to the surface of a roller adopted by the way of a body with mass of M. The deformed contact between a band on both rollers is allowed by the elastic and dissipa-tive elements c23, c45 , H23, H45 and also by mass m3. An example of the continuous movement of the masses m and M in the normal direction is analyzed. The simplified dynamic model of a precision rollerband mechanism such as the RTM roller-band system was described by differential equations and investigated. The differential equations of movement, in accordance with Fig.1 a, have these expressions: H12(ž1-ž2) + c12(z1-z2) = P1 mz2 - H12 (ž1 - ž2 ) - c12 (z1 - z2 ) + H23 (ž2 - ž3 ) + c23 (z2 - z3 ) = 0 3ž3 - H23 (ž2 - ž3 ) - c23 (z2 - z3 ) + [H45 (ž4 - ž5 ) + c45 (z4 - z5 )] ¦ f0sign(ž3 - ž6 ) + /(ž3 - ž6 ) = 0 Mz6 - [H45 (ž4 - ž5 ) + c45 (z4 - z5 )]/0 ¦ «gn(ž3 - ž6 ) - /(ž3 - ž6 ) = -P6 (1). mž4 + H45 (ž4 - ž5 ) + c45 (z4 - z5 ) = -P4 V skladu s sliko lb imajo diferencialne enačbe The differential equations of movement, in gibanja naslednje izraze: accordance with Fig.1 b, have the following expressions: H12(ž1-ž2) + c12(z1-z2) = P1 mž2-H12(ž1-ž2)-c12(z1-z2) + Nf0sign(ž2-ž6) + f(ž2-ž6) = 0 Mz6 -Nf0sign(ž2 -ž6)-f(ž2-ž6) = -P6 (2), mz5 Hu, H2V H45 - koeficienti viskoznega dušenja; cn, c2V c45 - koeficienti togosti; f0 - koeficient suhega trenja; / - koeficient mokrega trenja. Včasih je koeficient mokrega trenja/ sorazmeren vrednosti pravokotne reakcije, tj.: +P4 = N H , H, H 12 23 45 c, c, c 12 23 45 f0 f - viscous damping coefficients; - coefficients of stiffness; - coefficient of dry friction; - coefficient of wet friction. Sometimes the coefficient of wet friction, f, is proportional to the value of the normal reaction, i.e.: - koeficient mokrega trenja. V primeru zunanjega vzbujanja: f N45= H45 V fN 1 45 f1 - coefficient of wet friction. z&5 )+c45 (z4 -z5 ) For external excitation: (3), A1, A4, A6 B1, B4, B6 D1, D4, D6 w P1 = 4 + S1i1 + D1 sin (o? + ö1 j P4 = A4 + B4ž4 + D4 sin(cot + a4 ) P6= A+ ^6+ D6sin(mt + a6) z5 =D5sin(a>t + a5) . _d_ ~ dt komponente nespremenljivih sil; A1, A4, A6 stalnice, ki določajo linearno razmerje B1, B4, B6 med silami in ustreznimi hitrostmi; amplitude komponent harmoničnih sil; D1, D4, D6 kotna frekvenca; a (5). constant force components; constants defining the linear relationship between the forces and the appropriate velocities; amplitudes of the harmonic force components; angular frequency; a , a , a , a faze. a1, a4, a6, a5 phases. f Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 29 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 Da bi ocenili delovanje sistema, moramo To estimate the work of the system's performance upoštevati osnovne značilke, na primer delo ali moč, we consider basic characteristics, for example, the work or gonilne sile, silo koristnega upora itn. power, the moving forces, the force of useful resistance, etc. Glede na sliko 1 je delo gonilnih sil opisano According to Fig.1, the work of moving kot: forces is described as: \P^=\PAdt (6). 00 T - čas integracije; T - time of integration; H - značilna razdalja opravljena v času T. H - appropriate distance covered during the time T. Dejansko delo je podano z naslednjim izrazom: The useful work is given by the expression: H, T A = \Pidz6=)p6i6dt (7). 00 Izkoristek je podan z naslednjim izrazom: T The efficiency is given by the expression: ]p6ž6dt J>_______ (8). Au h= A JW P^dt Nepravilnost hitrosti gibanja je podana z o The irregularity of the motion velocity is naslednjim izrazom: given by the expression J Z (9), Z-tZ- (10). Z vnosom nove spremenljivke dobimo naslednje: By entering a new variable we obtain: 3 m (11), zi i /-\ \cv d co H N M m, x. =— (i = l,...,o); p =, ^ ; t = pt; = — ; v =— ; 2h =----- (rs = 12, 23,45) ; N =— ; u = — ; lu= — 1 I U dr p " pm p 2 ml M m m Aj Bj Dj D Ff=J = ^ (/- = 1,4,6); af=-L; 6,=—L; d, =—L ; d5 =^-; Sn =^ ; S45=^-pml c12l cnl pm cnl I l - dolžina jermena; / - band length; p in t sta novi spremenljivki. p and t are new variables. Če upoštevamo novo spremenljivko (11), Considering a new variable (11), the differential diferencialne enačbe gibanja (1) spremenimo takole: equations of movement (1) are converted to the type: 2Aj2 [x[-x'2) + [x1-x2) = Fl, /hA-2^23 {x'2 -x'3)-S2i (x2 -x3) + [2h45 (x'4 -x'5) + S45 (x4 -x5)] ¦ [f0sign(x'3 -x'6)] + f(x'3 -x'6) = 0 (12), ßx"6-\_2h45(x'4-x'5) + ö45(x4-x5)\f<3-sign(x[-x'6)-f(x[-x'6) = -F6 x"4 + 2h45 (x'4 - x'5 ) + S45 (x4 - x5 ) = -F4 hn, hiv h4S so koeficienti dušenja A hw A45 - coefficients of damping. Če upoštevamo novo spremenljivko (11), Considering the new variable (11), the differenti- diferencialne enačbe gibanja (2) spremenimo takole: al equations of movement (2) are converted to the type: 2Aj2 (x1'-x2) + (x1 -x2) = Fl x"2-2hl2(x[-x'2)-(xl-x2) + N'f0sign(x'2-x'6) + f(x'2-x'6) = 0 ^^ ß4-N%sign(x'2-x'6)-f(x'2 -x'6) = -F6 x"5+F4=N' Nato enačbo (3) spremenimo: Furthermore, Equation (3) is converted to the type: f = fl[2h45(x'4-x'5) + S45(x4-x5)\ (14). Zunanje vzbujanje (5) v neparametričnem The external excitation (5) in the non-para- izrazu vodi v naslednje: metric expression leads to: A 30 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 F1=a1+ ft1X1 + d1 sin (vt + a1 ) F4=a4+ b4x'4 + d4 sin (vt + a4 ] F6=a6+ b6x'6 + d6 sin (vt + a6} (15), x5 = d5 sin(nt + a5) kjer je v=w /p. here v=w /p. Izkoristek je podan z naslednjim izrazom: The efficiency is given by the expression: ]fx dt F^dz (16). Nepravilnost hitrosti gibanja je podana takole: 2 ANALIZA DINAMIČMH POJAVOV V DELOVANJU SKLOPA VALJEV IN JERMENA PRI MEHANIZMU RTM, KADAR NANJE NE VPLIVA VIBRACIJSKO VZBUJANJE The irregularity of the motion's velocity is given by the expression: c ' __ s max______,? min (s =1,2,6) 2 (17), (18). 2 THE ANALYSIS OF DYNAMIC PROCESSES OCCURRING IN THE “ROLLER-BAND” SYSTEM OF THE RTM, NOT INFLUENCED BY THE EXCITATION OF VIBRATIONS Namen te raziskave je definiranje dela, ki ga opravi sklop valjev in jermena pri mehanizmu RTM v odsotnosti vibracijskega vzbujanja. Raziskava je opravljena na nezdrsnem območju (NZ) upoštevajoč parametre mehanizma. Nezdrsnost je okoliščina, v kateri se telesa raziskovanega mehanizma pomikajo skupaj brez zdrsovanja, tj. x’ = x’2 = x’6 (si. 2 do 7): d1 = d4 kakor se to dogaja v obravnavanem primeru. Raziskava analizira dinamične pojave, ki potekajo v mehanizmu valjev in jermena v sistemu natančnega valja, tj. v jermenskem mehanizmu z nedeformirajočim stikom med telesi. Značaj dinamičnih pojavov v mehanizmu valjev in jermena z deformirajočim stikom med telesi v enakomernem gibanju je analogen pojavom, ki so v primeru nedeformirajočega stika. Iz krivulj diagrama zato lahko določimo razmerja med enakomernim gibanjem in njegovimi parametri. Pod vsakim diagramom so v oklepaju prikazani parametri sistema z deformirajočim stikom med telesi. Glede na sliko 2 pri definirani vrednosti a, hitrosti x\, x\ in x\ proučevanih teles postanejo istovetne, kar pomeni, da telesa ne zdrsujejo v tolikšni meri, da bi se znatno povečal koeficient suhega trenja The purpose of the research is to define the work of the “roller-band” system of the RTM in the absence of vibrating excitation. It is presented in the research of a non-slipping zone of bodies (NZ), depending on the parameters of the system. The non-slipping zone is understood as the condition when the bodies of the investigated system are moving together without slipping, i.e., x’1= x’2= x’6 (Figs. 2 to 7): =d6 =0 (19), as in the considered case. It is presented as research of the dynamic processes occurring in the “roller-band” system of a precision roller, i.e., band mechanisms with a non-deforming contact between the bodies. The character of the dynamic processes occurring in the “roller-band” system with a deforming contact between the bodies in steady motion is analogous to the processes occurring in this system with a non-deforming contact. Furthermore, from the graphical curves we can determine the relations of steady motion with its parameters. In brackets, under the figures, the parameters of the system with a deforming contact between the bodies are indicated. According to Fig. 2, at a defined value a4, the velocities x’1, x’2 and x’6 of the investigated bodies become identical, i.e., the bodies do not slip between themselves at a sufficient increase of the coefficient of 0 Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 31 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 x' 0.8 0.4 -0.4 x. = x'2 /o =0 /fo =0.1 i/o =0.3 ffoM\ /o=i.oVy Kjo= 0.6 /o= 0.8\V Lv v- /o= 0.6N)ç /fOaJ/ ynix'jS' VJU0 =01, /0 =0 0.8 0.4 0.4 ¦0.4 a4 0 -^l -lt:2 a4 =0.3 /"4 =0.6 a4 = l-Oj* K =0^^ « a4 =0.3 *6 0.4 /0 a b SI. 2. Gra/fl kažeta odvisnost hitrosti teles sistema pri enakomernem gibanju od parametrov gibanja Fig. 2. Graphs showing the dependence of the velocity of bodies of a system in steady motion on the parameters of motion a = 0,5; a = -0,2; b= b6 = -0,5; 2h12= 0,2; ju =1,0; f= 0,1 (2h2=2h4=2,0; S2=S4 = 10; ju= 0,01; b=-0,5) /0 (sl. 2 a). Spoznali bomo, da večja ko je vrednosto, pri/0 = konst, hitreje nastane nezdrsno območje med telesi (si. 2 b). To pokaže tudi slika 3. Tako je, pri definirani vrednosti /, zvečanje vrednosti a4 pomembno le, dokler se približuje vrednosti NZ. Ko pa to vrednost doseže, izgubi pomen, saj se telesa zdaj začnejo gibati z enakimi hitrostmi (si. 2 in 3). S povečanjem a4, pri koeficientu suhega trenja f0 = konst., NZ postane definirana vrednost a4 ne glede na koeficient viskoznega trenja/; (si. 4 a). Pri dani vrednosti a4 povečana vrednost/, povzroči le rahlo zmanjšanje hitrosti x \ (krivulje odvisnosti v diagramu postanejo bolj izbočene) (si. 5 b); vendar pa NZ, pri dani vrednosti/, postane definirana vrednost a4, hitrosti x\, x’2, x ; pa se izenačijo (si. 4 a in b). Pri definirani vrednosti a4 se hitrosti x \, x \, x ; obravnavanih teles izenačijo, hkrati pa se zmanjša vrednost ap kar pomeni, da manjša ko je vrednost av večje je nezdrsno gibanje med telesi (si. 5 a). Pri al = konst. se zdrsovanje teles zmanjša ob povečanju a4 (si. 5 b). Krivulje odvisnosti na sliki 5 se ostro prelomijo ob vstopu v NZ. Če je a, = konst. in se vrednost a4 zveča, se poveča hitrost nastanka pojava NZ. Če je a4 = konst, se navor nezdrsnosti med telesi pojavi ob povečanju a6 do svoje določene vrednosti (si. 6 a in b). V času povečevanja a6 se povečajo tudi hitrosti x \ = x \ = x \ (SI. 6 a); kljub temu je pojav NZ x[ -x'6 ' 1.2 0.9 0.6 0.3 W^^ /o = ° /„= 0.6 / /o = 0.3 / /„=i-o 7 0.2 0.4 0.6 0.8 a4 SI. 3. Graf kaže odvisnost hitrosti zdrsovanja med telesi sistema pri enakomernem gibanju od parametrov gibanja Fig. 3. The graph showing the dependence of the velocity of slipping between bodies of a system in steady motion on the parameters of motion a = 0,5; a= -0,2; b= b6 = -0,5; 2h12= 0,2; ju=l,0; f= 0J(2h 2=2h4=2,0; S2=S4 = 10; ju3= 0,01; b=-0,5) dry friction,/ (Fig. 2 a). It wiUbe clear that the greater the value a4 at/ = const, the faster it makes a non-slipping zone of the bodies (Fig. 2 b). Fig. 3 also shows this. Furthermore, at a defined value,/, the increasing value of a4 is meaningful only up to NZ. After reaching this value it loses sense, as the bodies start to move with an identical velocity (Fig. 2 and 3). With increasing a4 at the coefficient of dry friction/ = const, NZ becomes a definite value a4, irrespective of the coefficient of viscous friction,/ (Fig. 4 a). The increasing/ resulted only in a minor decrease of the velocities x \ at a given data a4 (the dependence curves in the figure have a more convex character) (Fig. 5 b); however, NZ at a given data/ becomes a defined value a4, and the velocities x\, x \, x \ become equal (Fig. 4 a and b). At a defined value a4 the velocities x\, x\, x \ of the investigated bodies level off, with a decreasing of value av i.e., the smaller is ap the faster the non-slipping movement between the bodies comes (Fig. 5 a). At ax = const the slipping of the bodies decreases with an increase of a4 (Fig. 5 b). The curves of dependences in Fig. 5 break sharply when going into NZ. If a6 = const and value a4 increases, NZ becomes faster. If a4 = const, the moment of non-slipping between the bodies comes with an increase of a6 up to its definite value (Fig. 6 a and b). During the increase of a6 the velocities of bodies x \=x \=x \ are increased (Fig. 6 a); however, o 32 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 x' 0.8 0.4 //i= 0 yf\ = 0.1 x[ = x'2 ^ //,= 0-2 A ^ = 0.2 Yi=o.i ~7i=o X 0.35 0.3 0.25 0.4 0. 2 *1 = X2 Î4= 0.5 \ / I4= 1.0 y; J4 = 0.5 / 0 0.1 0.2 /. a b SI. 4. Gra/fl kažeta odvisnost hitrosti teles sistema pri enakomernem gibanju od parametrov gibanja Fig. 4. Graphs of the dependence of the velocity of the bodies of a system in steady motion on the parameters of motion a= 0,5; a = -0,2; b = b6 = -0,5; 2h12= 0,2; ju =1,0; f= 0,6 (2h2=2h4=2,0; 82=84 = 10; ju= 0,01; b=-0,5) x' 0.6 0.2 -0.2 -0.6 -0.2 0.2 0.6 a4= 0.3x a4= 0.5\ «4=l-0\/ '/ x[ a4= 0'.5\y\ = x2^t / jL * / yk-M "l - "^6 0.8 0.6 0.4 0.2 0.2 0.4 0.6 a b SI. 5. Grafa kažeta odvisnost hitrosti teles sistema pri enakomernem gibanju od parametrov gibanja Fig. 5. Graphs of the dependence of the velocity of the bodies of a system in steady motion on the parameters of motion b,= b6 = -0,5; 2hn= 0,2; f0= 0,6; fi= 0,1; a6= -0,2 (2h23=2h45=2,0; 023 = 045= 10; jUs= 0,01; b4= -0,5) mogoč, in sicer pri zmanjšani vrednosti a4 (SI. 7 a). Če je a = konst, NZ nastane ob povečanju f, v nasprotnem primeru pa, ko je/0 = konst, NZ nastane ob povečanju fl4 (SI. 7 b). Glede na sliko 7 povečanje a4 in a6 povzroči nezdrsno območje med telesi. Pri definirani vrednosti a6 naraščanje vrednosti a4 po vstopu teles v območje NZ nima več pomena, ker se telesa zdaj gibljejo z enakimi hitrostmi. Na spodnjih slikah je območje NZšrafrrano. Poudariti je treba, da je/0 a4 = konst. the coming of NZ is possible, and at a smaller value of a4 (Fig. 7 a). At a= const NZ comes with increasing^ and, in contrast, at/0= const with increasing a4, we achieve NZ (Fig. 7 b). According to Fig. 7, the increasing a4 and a6 resulted in a non-slipping between the bodies. At a defined value a6 the increasing value of a4 after the arrival of the bodies in NZ has no sense, because they are moving with identical velocities. NZ is hatched. It is necessary to point out that/0 a4 = const. 0.2 -0.2 \ \ / a4= 0 3 a4= 0 49 «4 = 1 0\ \ 1 \ ¦¦ X' I -1 =-2 \y- 1.0 0.8 0.6 0.4 0.2 0 -0.5 -0.3 -0.1 0.1 0.3 a6 -0.5 -0.3 -0.1 0.1 a6 a b SI. 6. Grafa kažeta odvisnost hitrosti teles sistema pri enakomernem gibanju od parametrov gibanja Fig. 6. Graphs of the dependence of the velocity of the bodies of a system in steady motion on the parameters of motion b= b6 = -0,5; 2h12= 0,2; f= 0,6; f= 0,1 (2h2=2h4=2,0; S2=S4 = 10; /u = 0,01; b=-0,5; a = 0,5) 0.75 0.5 0.25 ^ // v/ Va Y/ v/ 7// i <4 V/ V/ v i  0.75 0.5 /// /// /// -0.5 -0.3 -0.1 0.1 0.3 0.25 0.5 0.75 a4 a b SI. 7. Področja obstoja menjavajočih se enakomernih režimov gibanja teles, odvisnih od parametrov gibanja Fig. 7. The areas of existence of varying steady regimes of motion of a system of bodies depending on its parameters a= 0,5; b= b6 = -0,5; f= 0,1; 2h]2= 0,2 (2h2=2h4=2,0; 82=84 = 10; /u = 0,01; b=-0,5): a- f= 0,6; b- a= -0,2 o a a 4 a Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 33 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 3 ANALIZA DINAMIČNIH POJAVOV V DELOVANJU SKLOPA VALJEV IN JERMENA, KADAR NANJE VPLIVA VIBRACIJSKO VZBUJANJE 3 THE ANALYSIS OF THE DYNAMIC PROCESSES OCCURING IN THE “ROLLER-BAND” SYSTEM, INFLUENCED BY THE EXCITATION OF VIBRATIONS Namen te raziskave je definiranje razmer pri delu, ki ga opravi sklop valjev in jermena, kar omogoči nadzor nad pojavom NZ med telesi sistema z vibracijskim vzbujanjem. Analiziramo delovanje sklopa valjev in jermena pri mehanizmu RTM, na katerega vplivamo z vibriranjem, tj. z ustvarjanjem naslednjega pogoja: dpd4, d5, d6*0. Da bi zagotovili pojav NZ, moramo povečati f0 (pri tem je v = konst), kar omogoči zmanjšanje vrednosti a. povečanje vrednosti v (pri čemer je/. = konst.) pa povzroči neznatno zmanjšanje vrednosti a. (si. 8 a). Če na sistem ne vplivamo z vibracijami, kar pomeni, da je d4 = 0, NZ, in je/ = konst., ima a4 manjši pomen kakor sicer (si. 8 a in b). Slednje lahko razložimo z zmanjšanjem sile trenja v primeru, ko vibracije delujejo na sistem in nastane območje NZ, ki ima povečane vrednosti a4. Večja ko je amplituda vzbujajočih vibracij d4, večja mora biti vrednost a4, kar je potrebno za zagotovitev območja NZ (sl. 8 b). Vrednost povprečne hitrosti X se zveča, medtem ko se vrednost % zmanjša s povečanjem amplitude vibracijskega vzbujanja dp koeficient izkoristka r| se tako strmo zmanjša (si. 9). Dogajanje lahko razložimo z zmanjšanjem sile trenja med telesi, zaradi česar se poveča zdrsno območje, posledično pa se zniža vrednost h . Pri dejanski konstrukciji mehanizma RTM lahko moč sile trenja nadziramo z uporabo vibracij (si. 10). Kakor je razvidno iz dosedanje raziskave, se nezdrsno območje zmanjša, če začnemo na sistem The purpose of the research is to define the conditions of work of the “roller-band” system, ensuring an opportunity to control the NZ between bodies of the system by the excitation of vibrations. The case is investigated for the “roller-band” system of RTM when it is influenced by vibrations, i.e., dpd4, dpd6i0. To ensure NZ, it needs to increase/ (having v=const), which ensures the decrease of a4 and the increase of v (having/0=const) ensures the non-considerable decrease of a4 (Fig. 8 a). If the system is not influenced by vibrations, i.e., d =0, NZ, when the meanings of/ = const, it will appear to have fewer meanings of a4 (Fig. 8 a and b). This can be explained by the friction force decreases in the case of vibrations influencing the system and NZ is reached, having greater meanings of a4. The greater the amplitude of the exciting vibrations d4, the greater must be the meaning of a4; which is necessary to ensure NZ (Fig. 8 b). The value of the average velocity x[ increases, and % decreases with the increase of the amplitude of the vibrating excitations d5; the coefficient of efficiency, r|, thus sharply decreases (Fig. 9). It is explained in such a way that the force of friction between the bodies of the system decreases, owing to which the slipping zone of the bodies is increased, and consequently the value of n decreases. In the real construction of an RTM we can control the magnitude of the friction force with the vibrations (Fig.10). As can be seen from this material, the non-slipping zone recedes when the influence of the SI. 8. Polja gibanja teles v različnih razmerah, odvisnih od parametrov vibracijskega vzbujanja Fig. 8. Fields of movements of bodies in different types of conditions, depending on the parameters of the exciting vibrations a = 0,5; a= -0,2; b= b=-0,5; f = 0,1; x’= x,'= x.'=0,3; a) d = 0,1; b) f = 0,6; v/2n = 0,5. 34 Ulozas R. V. SI. 9. Prikaz odvisnosti povprečnih hitrosti gibanja teles in izkoristka od parametrov vibracijskega vzbujanja, ko je f0 = 1,0 Fig. 9. The diagram of the dependence of the average velocities of the movement of the bodies and the efficiency on the parameters of the vibrating excitation at f =1.0 vplivati z vibracijami. To pomeni, da je v dejanskem sistemu mogoče nadzirati zdrsovanje med elementi mehanizma RTM, tj. nadzirati navor odpornosti za gibanje. To je pomembno, kadar oblikujemo konstrukcije RTM, saj lahko tako zagotovimo boljšo kakovost in natančnost ter ustvarimo bolj natančne dinamične značilke. 4 ANALIZA DINAMIČNIH POJAVOV MEHANIZMA RTM Meritve vibracij v mehanizmu RTM so težavna naloga, toda ne le zaradi majhne amplitude vibracij v valjih, ampak predvsem zaradi dejstva, da poleg vibracij zabeležimo tudi njihove številne medsebojne vplive. Ti nastanejo zaradi vibriranja podstavka in geometrične nenatančnosti izdelave posameznih delov mehanizma; ti vplivi se najpogosteje pojavljajo naključno. Veliko pozornosti namenjamo razvoju metod meritev vibracij in izločevanju vplivov. Metode stične raziskave so omejene, ker vplivi pogosto popačijo rezultate beleženja in tako znatno vplivajo na izid poizkusa. Precej obetavne pa so nestične optične metode meritev, ki v polni meri izpolnjujejo zahteve poizkusov, tj. potrebe po nestičnih, zelo natančnih meritvah in veliki ločljivosti. Te metode so bile uporabljene v analizi značilk vibriranja v valjih mehanizma RTM. SI. 10. Teoretična raziskava poenostavljenega dinamičnega modela RTM z valjema in jermenom Fig. 10. Theoretical investigation of the simplified dynamic model of RTM “roller-band” system a = 0,5; a6 = -0,2; b = b =-0,5; f = 0,l; %i ’= x2’= x6’=0,3; 2hu= 0,2; 2h23 = 2h4S = 2,0; S23 = S45 = 10; |i = 1,0, \±3 = 0,01; Sistem: 1 - vibriranje ni aktivirano {d4 = 0 ); 2 - vibriranje je aktivirano (d4 = 0,1; v/2'n = 0,1), območje NZ je šrafirano The system: 1 - vibrations do not influence (d4 = 0), 2 - vibrations influence (d4 = 0.1;(v/2n) 0.1), NZ is hatched system by vibrations starts. This means that in a real system it can be possible to control the slipping-by between the elements of the RTM, i.e., control of the moment of resistance to motion. This is important when designing the constructions of the RTM, which ensures higher quality and precision and more precise dynamic characteristics. 4 RESEARCH OF THE DYNAMIC PROCESSES RUNNING IN THE RTM ROLLER-BAND SYSTEM The measurement of vibrations in Rolamite-type mechanisms is quite a complicated task, not only because of the small amplitude of vibrations in the rollers, but mainly because of the fact that along with vibrations there is plenty of interference registered. This arises because of the vibration of the base, the geometrical imprecision of the produced parts, and most often the interference is random. Much attention is paid to the development of the methods of measuring the vibrations and the separation of interference. The methods of contact research are limited, because the interference quite often distorts the results of the registration and significantly influences the results of the experiment. Quite promising are the non-contact optical methods of measurement, which fully meet the demands of the experiment, i.e. non-contact, high-precision measurements, high dimensional resolution. These methods were used in the research of the characteristics of vibration in the RTM rollers. Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 35 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 Raziskana sta bila dva tipa vibrirajočih valjev Two types of RTM vibrating rollers were mehanizma RTM (si. 11). explored (Fig. 11). Ko elektrode piezokeramičnega obroča When the electrodes of the piezoceramic ring pritrjenega valja št. 7 (SI. 11 a), ki je ovit z gibkim of the fixed RTM roller No 1 (Fig. 11 a) wrapped by a jermenom, sprejmejo visokofrekvenčni električni sig- flexible band receive a high-frequency electric signal, nal, valj začne vibrirati. Dejansko področje stika med the roller starts to vibrate. The actual area of the gibkim jermenom, ki ovija valj 7, in piezokeramičnim contact zone between the flexible band wrapping the obročem 2, ki obdaja elastični torni obroč 3, se roller 1 and the piezoceramic ring 2 wrapping the elastic zmanjša in pojavi se plast vibracij. Valj 7je namenjen frictional ring 3 reduces and the film of vibrations zmanjšanju trenja v napravah, ki vključujejo occurs. The roller 1 is intended to reduce the friction mehanizem RTM. Os valja 7 je čvrsto pritrjena na in devices containing an RTM. The axis of the roller 1 osnovo, tako da se valja mehanizma RTM ne kotalita is fixedly attached to the base, and the rollers of the po gibkem jermenu, ampak drsita. RTM do not roll on the flexible band, but slip. Eksperimentalni valjšt. 2 (sl.llb) je namenjen The experimental roller No 2 (Fig. 11 b) is zmanjšanju trenja v napravah, ki vključujejo intended to reduce the friction in devices contain- mehanizem RTM. Toda valja takšnega mehanizma se ing an RTM. But the rollers of such an RTM roll on kotalita po gibkem jermenu. the flexible band. Valj (si. 11 b) je sestavljen iz osi 7, ki je The roller (Fig. 11 b) consists of an axis 1, fixedly čvrsto pritrjena na osnovo, ter iz piezokeramičnega attached to the base, and of an assembled piezoceramic obročastega elementa, ki je montiran na os. Na ring element that is put on it. It is made of a piezoceramic notranjo stran piezokeramičnega obroča 2 je ring 2, in which the internal side of an elastic frictional pritrjen elastični torni obroč 3, ki je v stiku z osjo ring 3 is fixed; this contacts axis 1, and on the outside 7 ; z zunanje strani pa je obroč 2 prekrit s togim ring 2 is wrapped by a rigid ring-like cover 4, attached obročastim pokrovom, ki je čvrsto pritrjen na obroč to it fixedly, which in turn contacts with the wrapping in je v stiku z ovijajočim gibkim jermenom. Vibracije flexible band. A vibrations-pressed gas film (VPGF) is valja med montiranim obročnim piezokeramičnim produced by vibrations of the roller between the elementom, elastičnim tornim obročem 3 in covering assembled ring-like piezoceramic element pritrjeno togo osjo 7 ustvarjajo tlačeno plinasto elastic frictional ring 3 and the fixed rigid axis 1. plast (PGF). The vibrations of the rollers in a radial direction Raziskali smo vibracije valjev v prečni smeri in the loaded and unloaded functioning modes were ter v primerih obremenitve in neobremenitve (si. investigated (Fig 12). 12). In the loaded mode, the roller is wrapped by V primeru obremenitve je valj ovit z gibkim the flexible band at angles from p /4 to 3/2 p. One end jermenom pod kotom od p /4 do 3/2 p. En konec of the band is fixed to the rigid basis, and a weight is jermena je pritrjen na togo osnovo, utež pa je fixed on the other end of the band. As is obvious from pritrjena na drugi konec jermena. Kakor je očitno the data of the performed experiment, the amplitude iz izvedenega preizkusa, se amplituda in and resonant frequency of the roller vibrations, 1 2 3 4 b SI. 11. Vibrirajoča valja mehanizma RTM: a - pritrjeni valj (1); b - vrteči se valj (2);1 - os, ki je trdno pritrjena na osnovo; 2 - piezokeramični obroč; 3 - elastični torni obroč; 4 - tesno prilegajoči se obročasti pokrov, ki ga ovija gibki jermen Fig. 11. RTM vibrating rollers: a - fixed (1); b - rotating (2); 1 - axis, fixedly attached to the base;2 -piezoceramic ring; 3 - elastic frictional ring; 4 - tight ring-like cover, wrapped by a flexible band 36 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 resonančna frekvenca vibracij valja ovitega z jermenom pod enakima kotoma in z različno obremenitvijo, zmanjšata s povečanjem ravni bremena jermena (si. 12 a). Ko analiziramo odvisnost amplitude vibracij valja od električne moči z nespremenljivo resonančno frekvenco in različno stopnjo obremenitve jermena, lahko ugotovimo, da se amplituda vibracij valja zmanjša, če se obremenitev jermena poveča (si. 12 b). Kadar je obremenitev jermena majhna, je odvisnost amplitude vibracij valja skoraj linearna. Če je dovedena napetost povečana, se poveča tudi amplituda vibracij. Iz grafov (si. 12 c in d), ki opisujeta odvisnost sprememb amplitude in frekvence vibracij valja od kota, pod katerim jermen ovija valj pri različnih ravneh obremenitve, lahko povzamemo, da se amplituda in frekvenca zmanjšata, če se kot ovijajočega jermena poveča. Krivulje eksperimentalne raziskave valja št. 2 so prikazane na sliki 13. Značilnosti frekvenčne amplitude vibracij valja št. 2, ki se sestoji iz piezokeramičnega obroča piezokeramičnega elementa 2 z dejujočo (notranjo) wrapped by a band at equal angles and with loads of different magnitude, diminish when increasing the level of load of the band (Fig.12 a). When analyzing the dependence of the amplitude of the roller vibrations on the magnitude of the power-supply voltage, with a constant resonance frequency and a different level of load on the band, one can draw a conclusion, that if the load of the band is increased, the amplitude of the roller vibrations diminishes (Fig. 12 b). When the load on the band is small, the dependence of the amplitude of the roller vibrations is almost linear. If the power-supply voltage is increased, the amplitude of the roller vibrations increases as well. From the graphs provided (Fig. 12 c and d), describing the dependence of the changes of amplitude and frequency of the roller vibrations on the angle of the roller wrapping band, with a different level of load applied, one may draw a conclusion that, if the wrapping angle of the band increases, the amplitude and frequency become reduced. The curves of the experimental research of the RTM experimental roller No 2 are presented in Fig. 13. The frequency amplitude vibration characteristics of the roller No 2, consisting of the piezoceramic ring of the piezoceramic ring element 2 A, 0.60 -1 ,2 0 45 3 /ffliuL 4 0.15 A, um 1y 0.60 2~> 3X 0.30 0 00 N4 N5 94.8 95.2 f, kHz 9.0 16.2 a b u,V a, um 0.75 0.45 1 2- f, kHz 95.35 95.25 s V *N N \ * S ^ ^¦1 .-2 S \ N 0.25 ji 0.75 ji ç), rad ' 0.25n 0 75 ti çj, rad c d SI. 12. Krivulje eksperimentalne raziskave vibrirajočega valja 1, ovitega s tesno prilegajočim se (obremenjenim) jermenom Fig. 12. The curves of an experimental research of an RTM vibrating roller 1, wrapped by a tight (loaded) band: a - A=f(f), ko/if U = 40 V; ->>. 4 2.25 V ¦"-* < l\ *~— *—, 3 1.35 ,2 0 45 1 36.9 37.2 f, kHz 0.25 p 0.75 p f, rad ^5 *4 *-3 ,_ 14 x2 1 0 a b A, mm 1.8 0.9 0.25 p 0.75 p f, rad 0 6 12 c d SI. 13. Krivulje eksperimentalne raziskave vibrirajočega valja 2, ovitega s tesno prilegajočim se (obremenjenim) jermenom: a - A = f(j) - velja za montirani piezokeramični obročasti element (si. 2 b), ko je U = 60 V; 1 -velja za delovno površino piezokeramičnega obroča; 2 - velja za zunanjo površino togega obročastega pokrova 4 Fig. 13. The curves of an experimental research of RTM vibrating roller No 2, wrapped by a tight (loaded) band: a - A=f(f) for an assembled piezoceramic ring element (Fig 2 b), when U = 60 V; 1 - for the working surface of the piezoceramic ring; 2 - for the outer surface of a rigid ring-like cover 4; b - A=f( SI. 15. Vibrirajoči valji RTM: a - nepremični (1), glej sliko 11 a; b - nepremični (1) z valovnim vodilom; c - rotacijski (2), glej sliko 11 b Fig. 15. RTM vibrating rollers: a - immovable (1), see Fig. 11 a; b - immovable (1) with a waveguide; c - rotary (2), see Fig 11 b dolžine premika s (razdalje, za katero se valj premakne v enem obdobju krmilnega sunka) od dolžine sunka t. , - s = fit. ), od natezne sile jermena Gv- s = fiGx), od vlečne sile valja G2, - s = fiG2), in od kota, pod katerim jermen ovija valja a - s = f(a). Iz grafa (si. 16 a, krivulja 1) je razvidno, da je ob daljšem sunku t. daljša tudi razdalja s, ki jo naredita valja v enenTobdobju krmilnega sunka. Sila trenja Ftr in čas t sta potrebna, da valja naredita razdaljo s, ko se vlečna sila jermena G2 = konst. zmanjšuje, če na valja vpliva večja amplituda dovedene napetosti in ju vleče večja sila Gl (si. 16 b). Del preizkusa smo izvedli tako, da smo vibrajočim valjem energijo dovajali zvezno pri a = 530°, G2 = 2,0 N = konst.. Razdalja s, na kateri se premakneta valja v eni dobi krmilnega sunka, se poveča, kadar je povečana vlečna sila valja G.. To je razvidno iz grafa (si. 16 a, krivulja 2). Če je G, > FQ in jcF0 zanemarljiva vrednost sile lepenja, se v primeru, ko je ta vrednost presežena, se valja začneta gibati the roller skip length s (the distance covered by the roller in one period of regulating impulse) on impulse duration tim , - s = ft ), on te rollers’ stretching force G1, - s = f(G1), on the band’s pulling force G2, - s = f(G2), on the angle of the band wrapping the rollers a - s = f(a). As is clear from the graph (Fig. 16 a, curve 1), the longer is the duration of the impulse t , the longer is the distance, s, that is covered by the im rollers in one period of the regulating impulse. The friction force Ftr and time, t, is needed for the rollers to cover the distance s, when the pulling force G2 = const of the band is decreasing if the rollers are influenced by a larger amplitude of feeding voltage and they are pulled by a greater force G1 (Fig. 16 b). An experiment was made so that the vibrating rollers were fed by a continuous power-supply mode, when a = 530°, G2 = 2.0 N = const. The distance s covered by the rollers in one period of regulating impulse increases, when increasing the force of the roller pulling G1. This is clear from the graph (Fig. 16 a, curve 2). If G1 > F0, where F0 is the marginal value of the still friction force, so that when it is exceeded the rollers start moving c 40 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 SI. 16. Krivulje odvisnosti: a - pomiki valja 1 v obdobju krmilnega sunka: 1 - s = f(timp ); 2 - s = f(G1 ); 3 - s = f(G2; 4 - s=f(a); b - odvisnosti Ftr = f(G1 ) - 1 do 3; t = f(G1 ) - 4 do 6 (za mehanizem RTM z valji 1); Ftr = f(G1 ) - 7 do 9 (RTM z nepremičnimi valji z valovnim vodilom). Napajanje napetosti U je naslednje: 3, 4 in 7 - 10 V; 1, 5 in 8 - 20 V; 2, 6 in 9 - 30 V. Fig. 16. Curves of dependencies: a - displacements of RTM roller 1 per one period of regulating impulse: 1 - s=f(t. ); 2 - s=f(G,); 3 - s=f(GJ; 4 - s=f(a); b - dependencies F =f(G.) - 1 to 3; t=f(G.) - 4 to 6 (for ROTamite mechanisms with the rollers 1); F^GJ - 7 to 9 (RTM with immovable rollers with waveguides). Feeding voltage U equals: 3, 4 and 7 - 10 V; 1, 5 and 8 - 20 V; 2, 6 and 9 - 30 V. brez stimulacije visokofrekvenčnih električnih signalov. Območje, v katerem je G1 >F0, je dodatno označeno s pikčasto črto (si. 16 a). Dane razmere pri preizkusu so naslednje: mehanizem RTM deluje na diskretni način; G2 = 2,0 N = konst; a = 530°; f = 88,5 kHz; U = 51 V; fimk = 5 Hz; tim = 1,5 ms; e - G. = 3,0 N; f - G, = 3,5 nTg - G, = 3,6 N; h - G = 3,7 N. Razdalja s, na kateri se premakneta valja v enem obdobju krmilnega sunka, se poveča, kadar se zmanjša natezna sila jermena (vlečna sila valja Gl = konst). To je razvidno iz grafa (si. 16 a, krivulja 3). Kadar je sila G2 (nategnjeni jermen) zelo majhna, se valja začneta premikati brez stimulacije z visokofrekvenčnimi električnimi signali. P Razmere pri preizkusu so v tem primeru naslednje: mehanizem RTM deluje na diskretni način; a = 530°; fr = 88,5 kHz; U = 51 V; G1 = 3,0 N = konst.; fim k = 5Rz; tim =l,5 ms; G.: j - 4,0 N; k - 2,0 N; l -I,7 N; m -l,5 N. Razdalja s, na kateri se premakneta valja v enem obdobju krmilnega sunka, se zmanjša, kadar ta poveča kot, pod katerim jermen ovije valja. To je razvidno iz grafikona (si. 16 a, krivulja 4). Ko je kot zavoja jermena zelo oster, G1>F0, se valja začneta premikati brez stimulacije z visokofrekvenčnimi električnimi signali. Razmere pri without being influenced by the high-frequency electrical signals. The zone in which G1 >F0 is additionally marked by a dotted line (Fig. 16 a). The conditions of the experiment are given as follows: RTM operating mode is start-stop; G2 = 2.0 N = ccwrf; «= 530°;^= 88.5 kHz; L/= 51 V; / = 5 Hz; t = 1.5 ms; e - G1 = 3.0 N;/- G1 = 3.5 N; g - G1 = 3.6 N; -^ = 3.7 N. The distance s covered by the rollers in one period of the regulated impulse increases when this is decreasing the stretching force of band (the pulling force of roller G1 = const). This is clear from the graph (Fig. 16 a, curve 3). When the force G2 (stretching the band) is very low, the rollers start moving without being influenced by the high-frequency electrical signals. The conditions of the experiment are as follows: RTM operating mode is start-stop; a = 530°;/ = 88.5 kHz; L7= 51 V; G1 = 3.0 N = const; f ,= 5 Hz;^ = 1.5 ms; G2: j - 4.0 N;yfc- 2.0 N; /- 1.7 N; m - 1.5 N. The distance s covered by the rollers in one period of the regulated impulse is decreasing when this is increasing the angle of the rollers’ wrapping by the band. This is clear from the graphs (Fig. 16 a, curve 4). When the wrapping angle is very low, G1>F0, the rollers start moving without being influenced by the high-frequency electrical signals. The conditions of the Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 41 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 preizkusu so v tem primeru naslednje: mehanizem RTM deluje na diskretni način; za a velja naslednje: n - 450°; o - 4S0°; p - 500°; r - 53Qr; G1 = 3,01 i '1 -2 0.1 0.4 G1, N 20 40 u, V 450 480 a b c a, rees SI. 18. Mehanizem RTM z valjema 2 (glej sl. 11 b in sl. 15 c) krivulje odvisnosti Fig. 18. RTM with rollers 2 (see Fig. 11 b and Fig. 15 c) dependency curves a - Ftr = f(G), ho/if a = 500°; G2 = 5,0 N; U je/is: 1 - 50 V; 2 - 35 V; 3 - 20 V; b - F& = f(U), ho/if Gt = 0,5 N; a = 500°; G2 je/is: 7 - 4,0 N; 2 - 5,0 N; 3 - 7,0 N; 4 - 8,0 N; 5 - 9,0 N; c - Ftr = f(a); Gt = 0,5 N; G2 = 5,0 N; U je/is: 1 - 50 V; 2 - 30 V The curves from the theoretical research were used when designing the Rolamite vibromotors. 6 RESEARCH OF THE DYNAMIC PROCESSES RUNNING IN THE ROLAMITE VIBROMOTORS Prvi vibramotorji so izkoriščali diagonalno udarjanje piezokeramičnega pretvornika vibracij (piezokeramični elementi) ob gibljiv element, tj. ploščo ali valj [7]. Ko na elektrode pretvornika dovedemo visoko frekvenčni električni signal, se končni del piezoelektričnega pretvornika, ki ima netogi stik z rotorjem, prične eliptično gibati in obračati rotor (sl. 19). Določili smo najboljši kot piezokeramičnega pretvornika vibracij 2, ki udarjajo ob rotor 1, pri katerem je zagotovljeno največje število vrtljajev rotorja 1. Pri raziskovani konstrukciji vibramotorja je najboljša vrednost kota a 125°. Ob konstruiranju vrtilnega vibramotorja Rolamite ter mehanizmov vlečnega jermena je bilo treba ugotoviti, kakšen vpliv ima na sinhronost vrtenja valjev uporaba načela Rolamite v mehanizmih vlečnega jermena. Model mehanizma prenosa gibanja je bil oblikovan kot vrtilni vibramotor Rolamite (sl. 20 a), na podlagi tega pa je bilo oblikovano eksperimentalno stojalo (sl. 20 b). The first vibromotors used diagonal hits by the piezoelectric converter of the vibrations (piezoceramic elements) onto a movable element, i.e., a plate or a roller [7]. After providing a high-frequency electrical signal on the electrodes of the converter, the end of the piezoelectric converter, elastically connected to the rotor, starts making elliptical movements and turns the rotor (Fig. 19). The optimal angle of the piezoelectric converter of the vibrations 2 hitting the rotor 1, at which the maximum rotations of rotor 1 are ensured, was found. The optimal value of the angle a in the explored design of the vibromotor is 125°. When designing the rotary RVM and the mechanisms of band pulling, it was necessary to find what impact the applying of the Rolamite principle in the mechanisms of band pulling has on the synchronicity of the rotation of the rollers. The model of a mechanism of movement transmission was designed as a rotary Rolamite vibromotor (Fig. 20 a), and based on that an experimental stand was designed (Fig. 20 b). 6 0 3 Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 43 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 SI. 19. Pot vrhnjega dela menjalnika (a - v trenutku, ko na elektrode pretvornika dovedemo visokofrekvenčni električni signal; b - ko se delovanje ustali) in model mehanizma z vlečnim papirnim jermenom, ki uporablja vibramotor: 1 - rotor; 2 - piezoelektrični pretvornik vibracij; 3 - žica, ki piezoelektričnemu pretvorniku vibracij dovaja visokofrekvenčno električno napetost; 4 - papirni jermen Fig. 19. Path of the tip of the changer (a - at the moment of providing a high-frequency electrical signal on the electrodes of the converter; b - when the working mode has been stabilized) and a model of the mechanism of paper s band pulling, using a vibromotor: 1 - rotor; 2 - piezoelectric converter of vibrations; 3 - power supply wire of piezoelectric converter that provides a high-frequency voltage; 4 - the paper band Pogonsko vozlišče sestoji iz piezoelektričnega The drive node consists of a piezoelectric pretvornika vibracij 1, ki ustvarja vrtenje valjev - converter of the vibrations 1, which is providing a rotorjev 2 in 3. Valja -rotorja 2 in 3, kakor tudi tesno rotation of the rollers-rotors 2 and 3. The rollers-rotors 2 prilegajoči se valj manjšega premera 4, so oviti z and 3, and also a roller of a smaller diameter 4 that is tight neskončnim jermenom 5. Valja 2 in 3 sta ovita z are wrapped by an endless band 5. The rollers 2 and 3 are neskončnim jermenom 5 pod kotom, ki je večji od wrapped by an endless band 5 by an angle of more than 270°, valj 4 pa je ovit pod kotom, večjim od 180°. 270°, and a roller 4 by an angle of more than 180°. The Shema meritev je predstavljena na sliki 20 b. scheme of measurement is presented in Fig. 20 b. Na gredi rotorjevlin 2 sta pritrjena dva enaka On the shaft of rotors 1 and 2 two identical raster rastrska diska 3 in 4 z znakom, ki se odziva na disks 3 and 4 with a raster mark that interacts with the svetlobni zaznavali 5 in 6. Predojačevalnika 7 in 8 sta photo sensors 5 and 6 are fixed. The former-amplifiers 7 a) b) SI. 20. Model mehanizma prenosa gibanja kot rotacijski vibramotor Rolamite (a): 1 - piezoelektrični pretvornik vibracij; 2 in 3 - valj - rotor;4 - valj manjšega premera; 5 - neskončni jermen in shema eksperimentalnega stojala (b): 1 in 2 - rotorja; 3 in 4 - rastrska diska; 5 in 6 - svetlobni zaznavali; 7 in 8 - predojačevalnika; 9 in 10 - merilnika frekvence; 11 in 12 - razločevalnika frekvence; 13 - blok dvojnega kanala registracije; 14 - napajalnik piezoelektričnega pretvornika vibracij Fig. 20. The model of a mechanism of movement transmission as a rotary Rolamite vibromotor (a): 1 - piezoelectric converter of vibrations; 2 and 3 - roller-rotor; 4 - roller of smaller diameter; 5 - endless band and scheme of experimental stand (b): 1 and 2 - rotors; 3 and 4 - raster disks; 5 and 6 - photosensors; 7 and 8 - former-amplifiers; 9 and 10 - frequency meters; 11 and 12 - frequency discriminators; 13 - block of double channels of registration; 14 - power-supply unit of piezoelectric converter of vibrations 44 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 povezana z merilnikoma frekvence 9 in 10 ter prek enakih razločevalnikov frekvence 11 in 12 tudi na blok dvojnega kanala zapisa 13. Elektrode piezoelektričnega pretvornika vibracij so priključene na napajalnik 14 in zaradi visokofrekvenčnega električnega signala, ki prihaja iz napajalnika 14, začne piezoelektrični pretvornik vibracij vibrirati in vrteti rotorja lin 2. Na ekperimentalnem stojalu (si. 20 b) smo raziskali dva rotorja RVM, katerih vrtilno gibanje je spodbudil piezoelektrični pretvornik vibracij. Nastavili smo najboljši kot (120° do 130°) stika pretvornika vibracij z vrtečim rotorjem. Najprej smo raziskali vibriranje dveh rotorjev vibramotorja pri prostem (neobremenjenem) teku, ko je bil pretvornik vibracij togo pritrjen na sredino vibramotorja. Ko se amplituda dovedene električne napetosti U zveča, se poveča tudi število rotorjevih vrtljajev n, vendar pa nenatančno pritrjen piezoelektrični pretvornik povzroči nesinhrono vrtenje rotorjev (si. 21, krivulji 7 in 2). Če sta rotorja vibramotorja ovita z neskončnim jermenom v obliki mehanizma RTM in se oba rotorja vrtita, nesinhronost vrtenja dveh rotorjev izgine, kar pomeni, da A«=0 (si. 21, krivulja 5). Ko se poveča zunanja obremenitev enega od rotorjev, se močno poveča tudi nesinhronost vrtenja obeh rotorjev (si. 22, krivulja 7). Povezava dveh rotorjev z neskončnim jermenom v obliki mehanizma RTM zmanjša nesinhronost njunega vrtenja na najmanjšo vrednost (si. 22, krivulja 3). S slike 22 tudi izhaja, da je nesinhronost vrtenja rotorjev vibramotorja Rolamite, ki sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki vrti oba rotorja, dosti manjša od nesinhronosti vrtenja rotorjev vibramotorja Rolamite, ki sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki vrti le enega od rotorjev (si. 22, krivulja 2). Iz navedenega je mogoče sklepati, da največjo sinhronost vrtenja rotorjev zagotavlja vibramotor Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki hkrati vrti oba rotorja. Pomanjkljivost vibramotorja, ki uporablja diagonalno udarjanje piezo električnega pretvornika vibracij (piezokeramični elementi) ob rotor, je njegova nezmožnost spremeniti smer vrtenja rotorja. and 8 are connected to the frequency meters 9 and 10, and through identical frequency discriminators 11 and 12 to a block of double channels of registration 13. The electrodes of the piezoelectric converter of vibrations are connected to a power-supply unit 14, and during a high-frequency electrical signal from a power-supply unit 14, the piezoelectric converter of the vibrations starts to vibrate and rotates the rotors 1 and 2. On an experimental stand (Fig. 20 b) the two RVM rotors were investigated, where the rotors rotational movement was obtained from one piezoelectric converter of vibrations. The optimal angle (120° to 130°) of contact for the converter of vibrations with a rotor rotated by it was used. First, the vibration mode of the two rotors, with the vibration’s converter rigidly fixed to the middle of it, is investigated in the empty (unloaded) working mode. When the amplitude of the feeding voltage U is increased, then the number of turns n of rotors increases; however, inexact fastening of the piezoelectric converter leads to non-synchronous rotations of the rotors (Fig. 21, curves 7 and 2). If the two VM rotors are wrapped by an endless band in the form of RTM and both rotors are rotating, the nonsynchronicity of the rotors’ rotations disappears, i.e., A«=0 (Fig. 21, the curve 3). When the external loading incereases on one of the rotors, the nonsynchronicity of the rotations of both rotors sharply increases (Fig. 22, the curve 7). The connection of the two rotors by an endless band in the form of an RTM reduces to a minimum the nonsynchronicity of their rotations (Fig. 22, the curve 3). From Fig. 22 it also follows that the magnitude of the nonsynchronicity of the rotation of the rotors of the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations, which rotates both rotors, is much less than the magnitude of the nonsynchronicity of the rotation of the rotors of the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations, which rotates only one rotor (Fig. 22, the curve 2). From this it is necessary to draw a conclusion that the highest synchronicity of rotation of the rotors is provided by the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations that simultaneously rotates both rotors. A weakness of the vibromotor that used diagonal hits of the piezoelectric converter of vibrations (piezoceramic elements) onto a rotor is the impossibility of reversing the rotation of a rotor. Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 45 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 An, min-' SS -Si n. min-' SS K / 40 ® 2\ // / 3 S UV SI. 21. Krivulji odvisnosti za nesinhrono vrtenje rotorjev vibramotorja pri prostem (neobremenjenem) teku: krivulji 1 in 2 - ko je n=f(U) pri dveh rotorjih, ki nista povezana z neskončnim jermenom in čigar vrtenje ustvarja splošni piezoelektrični pretvornik; krivulja 3 - ko je An=f(U) pri vibramotorju dveh rotorjev s splošnim piezoelektričnim pretvornikom vibracij potrebnim za vrtenje obeh rotorjev Fig. 21. Dependency curves for non-synchronous rotations of rotors VM in the empty (unloaded) mode of working: curves 1 and 2 - when n=f(U) for two rotors unconnected by an endless band and getting the rotation from the general piezoelectric converter of vibrations; the curve 3 - when An=f(U) for RVM of two rotors with general piezoelectric converter of vibrations for rotating both rotors 7 SKLEPNE OPOMBE SI. 22. Krivulje odvisnosti vrtilne nesinhronosti rotorjev od moči zunanje obremenile enega od rotorjev A = f(M), ko je U = konst. = 50 V: 1 - za primer dveh rotorjev, M nista povezana z neskončnim jermenom in ju vrti splošni piezoelektrični pretvornik vibracij; 2 - za primer vibramotorja Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, M vrti le en rotor; 3 - za primer vibramotorja Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki vrti oba rotorja Fig. 22. Curves of the dependencies of the rotations nonsynchronicity of the rotors on the magnitude of the external loading on one of the rotors A=f(M) when U=const=50V: 1 - for two rotors not connected by an endless band and both getting rotation from the general piezoelectric converter of vibrations; 2 - for the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations, which rotates only one rotor; 3 - for the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations that rotates both rotors 7 CONCLUDING REMARKS S teoretičnim delom raziskave smo dokazali naslednje: 1. Povečanje koeficienta suhega trenja omogoči hitrejše oblikovanje nezdrsnega območja med telesi mehanizma RTM. 2. Parametri vibracij mehanizma RTM se spremenijo takoj, ko elementi sistema RTM dosežejo nezdrsno območje, kar pomeni, da lahko na nezdrsno področje vplivamo z vibracijskim vzbujanjem. 3. Če povečamo amplitudo vibracij, se sila trenja med telesi sistema zmanjša; če se poveča zdrsno področje med telesi sistema, se zmanjša izkoristek. Z eksperimentalnim delom raziskave smo dokazali naslednje: 1. Povečanje amplitude električne napetosti, zmanjšanje sile obremenitve gibkega jermena in Theoretical research proved: 1. The increasing magnitude of the dry-friction coefficient makes it faster to achieve a non-slipping zone between the bodies of the “roller-band” system of the RTM. 2. From the “roller-band” system of the RTM the vibration parameters depend as quickly as bodies of the system achieve a non-slipping zone, and this means that the non-slipping zone can be operated by the excitation of vibrations. 3. If the amplitude of vibrations is increasing, then the force of friction between the bodies of the system is decreasing; if the zone of slipping between the bodies of the system is increasing, the magnitude of the efficiency is decreasing. Experimental research proved: 1. The increase of the supply-voltage amplitude, the decrease of the force load magnitude of the flexible 46 Ulozas R. V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 26-47 zmanjšanje kota, pod katerim gibki jermen ovija valj, povzročijo povečanje amplitude vibracij valja. 2. Mehanizem RTM z vrtečima se, vibrirajočima valjema, ima v primerjavi z vibrirajočima valjema drugega tipa boljšo ležajno zmogljivost in je bolj občutljiv. Zato je priporočljivo, da ga uporabljamo v izredno občutljivih sistemih. 3. Če primerjamo vibramotor Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki sočasno vrti oba rotorja, ter vibramotor Rolamite, ki se sestoji iz dveh rotorjev in piezoelektričnega pretvornika vibracij, ki vrti le enega od rotorjev, prva možnost omogoči večjo sinhronost vrtenja rotorjev. band and the decrease of the angle wrapping of the roller by the flexible band cause the increase in the amplitude of the roller vibrations. 2. The RTM with rotating vibrating rollers, compared with vibrating rollers of another type, have a better bearing capacity and are much more sensitive. Therefore, it is advisable to use them in exceptionally sensitive systems. 3. If we compare the Rolamite vibromotor of two rotors with the piezoelectric converter of vibrations, which simultaneously rotates both rotors, and the Rolamite vibromotor of two rotors with a piezoelectric converter of vibrations, which rotates only one rotor, the first variant provides the highest synchronicity of the rotation of rotors. 8 VIRI 8 REFERENCES [1] Wilkes, D.F. (1967) Rolamite: A new mechanical design concept.-Research report SC-RR-67-656 A, Sandia Laboratories, December, 223p. [2] Wilkes, D.F. (1968) Rolamite: A new mechanism. Mechanical Engineering. April, v. 90, No 4, 11-29. [3] Percival, CM., Norwood, FR. (1969) A theoretical and experimental investigation of the dynamic response of Rolamite. Trans. ASME, Ser.B, v. 91, No 1, 235-239. [4] Ulozas, R.V. (2004) Raziskava zdrsa v mehanizmu med valjem in trakom - An investigation of slipping in Rolamite-type mechanisms. Strojniški vestnik - Journal of Mechanical Engineering, v.50, No 6, 302-309. [5] Fridman, H.D., Levesque, P. (1959) Reduction of static friction by sonic vibration.-J. Appl. Phys., v. 30, No 10. [6] KaHaneHac, P. M. (1984) Bn6poonopi,i.- Bhjibhioc, MoKCJiac, 208 c. [7] EaHCJiBiiHioc, PK)., ParyiBCKHC, K.M. (1981) BH6poflBHraTenH.-BHni.Hioc, MoKCJiac, 193 e. [8] Invention of USSR JV° 609074. Avtorjev naslov:prof. dr. Ričardas Viktoras Ulozas Univerza Šiauliai Vilniaus 141 LT-76353 Šiauliai, Litva ulozas@tf.su.lt Author’s address: Prof. Dr. Ričardas Viktoras Ulozas Šiauliai University Vilniaus 141 LT-76353 Šiauliai, Lithuania ulozas@tf.su.lt Prejeto: Received: 17.10.2005 Sprejeto: Accepted: 23.2.2006 Odprto za diskusijo: 1 leto Open for discussion: 1 year Teoretična in eksperimentalna analiza - A Theoretical and Experimental Investigation 47 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 UDK - UDC 631.365:681.5 Strokovni članek - Speciality paper (1.04) Optimizacija neprekinjenega postopka sušenja v težnostnih sušilnicah Optimization of the Performance of the Continuous-Drying Process in Gravity Dryers Neven Voča - Tajana Krička - Vanja Janušič (University of Zagreb, Croatia) V prihodnosti pričakujemo razvoj tehnologije in izvedbo tehnoloških načrtov; seveda pa bo obseg njihove uporabe določen tudi z dejanskimi možnostmi, potrebami in delovnimi razmerami. Na vseh področjih človeške dejavnosti, tudi na področju kmetijstva, nastajajo načrti in napovedi za prihodnji razvoj. Na podlagi znanja, ki je bilo doslej uporabljeno v postopku osuševanja v gravitacijskih sušilnicah, in dosegljivih podatkov o medsebojni odvisnosti velikega števila parametrov, ta prispevek predlaga način optimizacije posameznih sklopov postopka osuševanja. Celoten postopek optimizacije sušenja v gravitacijskih sušilnicah moramo razviti v posameznih stopnjah, upoštevajoč posamezne funkcionalne sklope. Vsaka stopnja vpliva na izboljšanje celotnega postopka in vse stopnje skupaj vodijo v optimizacijo delovanja sistema. Dodatna prednost predlaganega postopka je v tem, da ga lahko izvedemo postopoma. Z optimizacijo sušenja dosežemo večjo stabilnost delovanja sušilnic, zmanjšanje porabe energije in boljšo kakovost zrn. © 2007 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: sušenje, optimiranje, statična lastnost, učinkovitost, mikroprocesorsko krmiljenje) Technology and technological expectations are expected to develop with time; however, opportunities, needs and working conditions affect the extent of their usage. Predictions are made in all areas of human activity, and this includes the agricultural sector. Using the know-how so far applied during the drying process in gravity dryers, together with the available data on the interdependencies of a large number oj parameters, this paper suggests how a system for drying could be organized by optimising the functional ensembles. A comprehensive method for drying-process optimization in gravity dryers can be built in several steps from several functional ensembles. Each step improves the process, and together they represent the complete system for performance optimization. An additional property is the possibility of realizing each step. The drying-process optimization results in the stabilisation of the dryer functions, a decrease in the specific energy consumption, and better kernel quality. © 2007 Journal of Mechanical Engineering. All rights reserved. (Keywords: drying process, optimization, static properties, performance, microprocessor controller) 0 UVOD 0 INTRODUCTION Visoke cene energije in drugi problemi, povezani z naftnim trgom, so v zadnjem desetletju spodbudili vrsto znanstvenih raziskav na področju energetike. Na primer, priča smo bili intenzivnemu raziskovanju sušenja kmetijskih pridelkov, ki je razkrilo, da je kar 40% vseh stroškov porabljenih za to opravilo [1]. Vsi lahko kvarljivi pridelki morajo biti konzervirani. Konzerviranje je postopek popolne High energy costs and problems in the oil market have resulted in many scientific investigations in the field of energetics over the past ten years. As an example, intensive investigations have been carried out in the field of drying agricultural products, and it was determined that 40% of the overall energy costs are spent during this process [1]. All easily perishable products have to be preserved. This term refers to the final operation of com- 48 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 odstranitve prisotnih mikroorganizmov ali vsaj ustavitev njihove rasti in razmnoževanja. Ta postopek omogoči hrambo izdelka za določeno časovno obdobje, ko izdelek ostane nespremenjen, in tako omogoči njegovo uporabo ne glede na čas in kraj njegove pridelave. Namen konzerviranja je torej ohranitev primarnih značilnosti izdelka in podaljšanje njegovega roka trajanja [2]. Na podlagi dosegljivih podatkov o žitaricah je bilo ugotovljeno, da je osuševanje postopek, ki ga določa medsebojno vplivanje številnih parametrov. Kakovost osuševanja je odvisna od fizikalnih značilnosti ozračja, v katerem poteka osuševanje, fizičnih ter kemijskih značilnosti poljščine in debeline plasti, skozi katero prehaja voda; slednja pa je odvisna od značilnosti sušilnice. Hitrost sušenja je odvisna od vseh omenjenih dejavnikov, katerih učinke lahko opazujemo z vidika kinetike osuševalnega postopka, pa tudi s tehnološkega vidika, tj. glede na kakovost osušenega pridelka [3]. Na zbirnem mestu imajo koruzna zrna delež vlage večji od ravnovesnega stanja, ki je najbolj primerno za shranjevanje. Zaradi tega je postopek osuševanja le nadaljevanje in dokončanje spontanega zorenja zrna, ki se ne more zgoditi po naravni poti. Da bi podaljšali dobo skladiščenja zrna, mora biti postopek osuševanja osredotočen na konzerviranje zrna in na ustvarjanje primernih okoliščin. Namen osuševanja je odstranitev odvečne vsebnosti vode, tj. ohranitev le deleža vode, ki je potrebna za mirujoč obstoj [4]. Hitrost in kakovost sušenja zrna sta odvisni od postopka sušenja. Na primer, pri spontanem sušenju je temperatura zraka skoraj enaka temperaturi zrn, zaradi cesar je sušenje zelo počasno. Ko pa pri postopku sušenja uporabljamo vroč zrak, se hitrost sušenja poveča. V tem primeru povečana temperatura zraka povzroči zmanj sanje vlage v zrnih in povečana razlika med vlažnostjo zrna ter vlažnostjo zraka pospeši sušenje ([5] in [6]). Učinkovitost sušenja je odvisna od parametrov, ki se navezujejo na značilnosti zraka, tj. od toplotne intenzivnosti, hitrosti zračnega toka, relativne vlažnosti, pa tudi od načina izgradnje sušilnice ter temperature zrn. Slednja je, kot funkcija temperature zraka, najbolj pomemben in najbolj občutljiv parameter v postopku sušenja. Največje dovoljene temperature zrn, ki so odvisne od namena uporabe zrn, določajo tudi temperaturo zraka, uporabljeno v postopku sušenja. To pomeni, pletely removing the micro-organisms that are present, or at least stopping their growth and multiplication. This process ensures the product is preserved without any changes during a specific period of time and therefore ensures that it can be used, no matter when and where it was produced. Hence, the aim of the preservation is to maintain the product’s primary properties and to prolong its useful lifetime [2]. According to the available data on plants for cereal finishing, it was determined that the drying process involves the multiple interconnections of parameters. The quality of the drying process itself depends on the physical properties of the atmosphere the drying is being conducted in, on the physical and chemical properties of the product, and on the thickness of the layer the water is diffusing through. The last of these properties depends on the properties of the dryer. The velocity of the drying process depends on the above-mentioned parameters, whose effects can be observed in terms of the drying-process kinetics, and from the technological point of view, i.e., the quality of the dried product [3]. At the collection point the corn kernel has a higher moisture content than at equilibrium point, which is a desirable property for storing. This is why the drying process is only a continuation and finishing of the spontaneous ripening of the kernel, which cannot be carried out naturally. In order to store the kernel for a longer period the drying process has to be focused on kernel preservation and on providing the necessary related conditions. The aim of the drying process is to remove the redundant water content, i.e., to retain only the water content necessary for dormant life [4]. The velocity and quality of the kernel-drying process depend on the drying procedure. For instance, the air temperature during the spontaneous drying process is almost equal to the kernel temperature, which leads to a very slow drying rate. When heated air is used in the drying process, the drying rate is faster, i.e., an increased air temperature leads to a decrease in the kernel’s moisture content, and so a greater difference in the moisture contents of the kernel and the air speeds up the drying process ([5] and [6]). The drying efficiency depends on a few parameters associated with the air, i.e., its thermal intensity, flow velocity and relative humidity, as well as the dryer construction and the temperature of the kernel. The last of these is, as a function of the air temperature, the most important and the most sensitive parameter in the drying process. The maximum allowed temperatures of the kernel, which again depend on the purpose, limit the air temperatures that can be used in the drying process. This Optimizacija neprekinjenega postopka sušenja - Optimization of the Performance of the Continuous-Drying 49 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 da se zmogljivosti sušilnice na more povečati s preprostim povečanjem temperature zraka, saj bi v tem primeru sušenje zrna poškodovalo. Za postopek sušenja velja, da je osuševanje bolj izrazito pri višji temperaturi in boljšem prenosu toplote iz zraka na sušeni pridelek. Še več, pomemben parameter sušenja je tudi hitrost prehajanja vode v razdalji med jedrom in površino pridelka ([3], [7] in [8]). Zrna so običajno v sušilnico dostavljena z različnih krajev Zato imajo razliČna zrna različne deleže vlage, pripadajo različnim sortam in hibridom, a so v sušilnici pomešana in skupaj osušena. Ker se zrna razlikujejo glede na morfološko strukturo in pripadajoča razmerja, se tudi v postopku sušenja različno obnašajo. Hitrost sprostitve odvečne vode, ki ustvari higroskopično ravnovesje, se spreminja glede na vrsto hibrida (v primeru koruznih zrn znaša 14 %). Glede na prehajanje vode skozi zrna je najbolj problematičen semenski mešiček in Katic [9] je ugotovil, da je debelina semenskega mešička obratno sorazmerna (r=0,&3) s hitrostjo sušenja. Razmerja v zrnih vplivajo na postopek sušenja tudi z ustvarjanjem odpornosti proti zračnemu toku. Sušenje lahko zmanjša prostornino zrn za 40 %, zaradi česar se spremeni poroznost kupa zrn v sušilnici, kar še dodatno poveča odpornost proti zračnemu toku [9]. Ob izhodu iz sušilnice imajo zato zrna različne deleže vlage. V preteklih desetih letih so se razlike med vlago osušenih zrn še dodatno povečale zaradi slabih gradenj sušilnic, tako da se je razpon deleža vode lahko povečal tudi do 11 %. V takšni situaciji je skoraj nemogoče organizirati dolgotrajno skladiščenje zrn, zato je treba uvesti nove tehnologije osuševanja. Ko govorimo o postopku sušenja, je poleg dejavnikov, kakor sta kakovost zrn in zmogljivost sušilnice pomemben tudi dejavnik porabe energije na kilogram vode, ki izhlapi iz zrn. Teoretično je energija potrebna za izparevanje vode enaka specifični entalpiji nasičene pare pri tlaku, ki ustreza temperaturi izparevanja ([l 1] do [13]). Namen tega prispevka je, na podlagi najnovejšega znanja in sodobnih tehnik, predlagati nov način organizacije sistema neprekinjenega sušenja v navpičnih gravitacijskih sušilnicah. 1 RAZISKOVALNA METODOLOGIJA Za potrebe nadzora neprekinjenega sušenja zrna smo upoštevali le posamezne odvisnosti med means that the capacity of the dryer cannot be increased simply by increasing the air temperature, because this would lead to a drying process that has detrimental effects on the dried kernel. For the drying regime, the higher the temperature and the better the air-to-product heat transfer, the more intensive is the resulting drying process. Moreover, an important parameter in the drying process is the rate of water fluctuation from the centre of the product to its surface ([3], [7] and [8]). The kernels that are dried in a dryer are usually being supplied from different places. Consequently, these kernels have different moisture contents and are of different varieties and hybrids, which are then mixed and dried when entering the dryer. Because the kernels differ in morphological structure and proportions, they behave differently in the drying process. The rate of release of the redundant water content until the hygroscopic equilibrium is achieved differs depending on the hybrid (for the corn kernel this means 14%). The pericarp is the major problem in terms of the water flow through the kernel, and Katie (1985) established that its thickness is inversely related (t=0.83) to the velocity of the drying process. Kernel proportions also affect the drying process by providing a resistance to the air flow The drying process can decrease the kernel’s volume by 40%, which changes the pile porosity in the dryer and subsequently leads to a greater resistance to the flow of air [9]. Accordingly, these exceptional kernels have a different moisture content when exiting the dryer. In the past ten years the differences in kernel moisture after the drying process were even more obvious because of poor dryer constructions, which caused variations in the water content of up to 11% [10]. The long-term storage of such kernels is almost impossible to achieve, so there is a need for the introduction of new drying technologies. When speaking of the drying process, besides parameters such as kernel quality and dryer capacity, the specific energy consumption per kilogramme of water evaporated from the kernel is also an important parameter. Theoretically, the energy that is necessary for the evaporation of the water is equal to the specific enthalpy of saturated steam at the pressure that corresponds to the evaporation temperature ([11] to [13]). The aim of this paper is to propose a new way of organising a system of continuous drying in vertical gravity dryers, based on the latest knowledge and modern techniques. 1 RESEARCH METHODOLOGY For the purposes of monitoring the continuous kernel drying, single dependencies 50 Foca N. - Krička T. - Janušič V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 dvema ali tremi spremenljivkami, drugim pa smo določili stalne vrednosti in tako preprečili njihovo učinkovanje. Kakovostni nadzor parametrov postopka sušenja zrn je osnova za zadovoljivo neprekinjeno sušenje, saj omogoča potrebno kakovost zrn ob izhodu iz sušilnice. Za sušenje množice zrn je potrebno, da spremenimo nekatere dejavnike, npr. temperaturo osuševalnega zraka ali hitrost prezračevanja. V gravitacijskih sušilnicah so zrna izpostavljena enakim razmeram, zato so na svoji poti proti izhodu iz sušilnice lahko izpostavljena načrtovanim parametrom. Če spremenimo enega izmed dejavnikov in pri tem želimo, da rezultat osuševalnega postopka ostane nespremenjen, moramo spremeniti tudi preostale dejavnike. To je osnovno vodilo optimizacije sušenja, s katerim želimo doseči: - najboljšo mogočo kakovost zrn, - najmanjši čas sušenja ali največjo zmogljivost sušilnice, - najamanjšo porabo energije. Doseganje največje zmogljivosti sušilnice in najmanjše porabe energije je težavna naloga. Za doseganje najboljše mogoče kakovosti zrn pa je potrebno temeljito poznavanje obnašanja zrn v različnih razmerah. Poznati moramo vse dejavnike, ki vplivajo na kakovost zrn. Te dejavnike lahko izrazimo v obliki: - preglednic ali diagramov ustaljenih odvisnosti med spremenljivkami; - krivulj dejavnikov, ki kažejo ustaljene odvisnosti; - matematičnih izrazov, s katerimi dobimo približne vrednosti odvisnosti spremenljivk; - preglednic in diagramov, ki kažejo odvisnosti spremenljivk od časa; - diferencialnih enačb sistemov, posebej tistih, ki izrazijo približne vrednosti odvisnosti določenih spremenljivk od časa ter drugih spremenljivk. Zaradi velikega števila podatkov je treba voditi njihovo klasifikacijo glede na tip in potencialno rabo podatkov. Sam postopek osuševanja pa lahko opazujemo z uporabo ustaljenih ali dinamičnih značilnosti, odvisno od tega, ali čas definiramo kot dejavnik naše raziskave. 1.1 Ustaljene lastnosti Naši predlogi za izboljšano gradnjo gravitacijskih sušilnic se nanašajo tudi na določitev številnih meril, potrebnih za boljše delovanje between two to three variables were taken into consideration, while others were kept at constant values and their effects were eliminated. Qualitative monitoring of the parameters of the kernel-drying process is the basis for satisfactory continuous drying because it ensures the required quality of the kernel when it exits the dryer. The batch-drying process requires the parameters, e.g., the drying-air temperature or the ventilation speed, to be changed. In gravity dryers the kernel is exposed to the same conditions in order to be exposed to the programmed parameters on its journey to the dryer’s exit. If one of the parameters is being modified, and the result of the drying process is expected to remain unchanged, the other parameters need to be modified, too. This is the basis for the drying-process optimization, in order to achieve: - the best kernel quality, - the minimum drying period or maximum dryer capacity, - the minimum energy consumption. Achieving the maximum dryer capacity and the minimum energy consumption is a difficult problem. However, obtaining the best kernel quality requires a comprehensive knowledge of kernel behaviour in different conditions. All the parameters that affect the kernel quality need to be known. These parameters are expressed in the form of: - tables or diagrams of the static dependencies between variables, - parameter curves showing static dependencies, - mathematical expressions, used for an approximation of the variables’ dependencies, - tables or diagrams expressing the variables’ dependence on time, - differential equations of the systems, especially those which approximate a particular variable’s dependence on time and other variables. Because of the large amount of data it is necessary to carry out their classification from the data-type and the potential-application points of view. The drying process itself can be observed by using either static or dynamic properties, depending on whether time is taken into consideration as a parameter. 1.1 Static properties The present proposals for improving the gravity dryers’ construction also refer to establishing numerous criteria for better operation of the dryer, Optimizacija neprekinjenega postopka sušenja - Optimization of the Performance of the Continuous-Drying 51 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 sušilnice, kar pa je spet povezano s kakovostjo izdelka, najmanjšimi stroški izdelave sušilnice in njenimi tehničnimi rešitvami, ki naj omogočijo najmanjšo porabo energije in časa. Razpon spremenljivk postopka in “delovno polje” določimo z izbiro določenega tipa konstrukcije in zmogljivosti sušilnice, v kateri je večina postopkov optimiziranih. Diagrami odvisnosti določenih spremenljivk znotraj določenih delovnih polj kažejo ustaljene lastnosti. Izbira avtomatičnega upravljanja ali avtomatiziranega vodenja temelji na teh lastnostih. Poleg tega so pogosto določeni tudi pomembni podatki o vrednostih tretje spremenljivke. V primeru večje vrednosti določene spremenljivke ali parametra je ustaljena lastnost izražena kot krivulja parametra. Ko v izračunih uporabljamo ustaljene lastnosti, je koristno, da odvisnosti med spremenljivkami pokažemo z matematičnimi izrazi. 1.2. Dinamične lastnosti Dinamične lastnosti določijo obnašanje spremenljivk v času. Ko govorimo o sušilnicah, je primerno, da določimo njihovo dinamično obnašanje in ga predstavimo v obliki prehodnih lastnosti ali kot odziv na skočno funkcijo. Tovrstni časovni diagrami kažejo potencialne pojave odziva neke spremenljivke v času, ko druga spremenljivka skokovito spremeni svojo vrednost. Te podatke uporabimo, ko določamo čas in način obnašanja določene spremenljivke, ki smo jo spremenili zato, da bi lahko predvideli obnašanje druge spremenljivke. Dinamično obnašanje izrazimo matematično v obliki diferencialnih enačb. Vendar pa moramo, pred določitvijo postopka z uporabo diferencialnih enačb, nastaviti toliko enačb, kolikor je spremenljivk. Da bi lahko uporabljali te enačbe na določenih predmetih, morajo koeficienti enačb ustrezati izbranemu predmetu. V našem primeru morajo ustrezati sušilnici. Pregled rezultatov osuševanja je prikazan z dvema diferencialnima enačbama. V praksi smo enačbi preizkusili z uporabo določenega osušitvenega modela, ki smo ga kasneje uporabili tudi za določitev koeficientov enačb. Numerične rešitve teh enačb, in posledično tudi vrednosti spremenljivk, se niso znatno spreminjale. Vendar se je ta sistem diferencialnih enačb nanašal na zelo preprost model in veliko parametrov ter podmen smo zanemarili. Zato lahko ta pregled osuševalnega postopka uporabljamo le v nekaterih splošnih which again refer to the quality of the existing product, to the minimum dryer-production costs and to the plant’s technical solutions with a minimum energy and time consumption. The range of the process variables and the “working field” are determined by choosing the dryer’s construction and capacity type, in which the majority of processes are optimal. Diagrams showing the dependence of particular variables within estimated working fields are known as static properties. The selection of automatic manipulation or automatic conduction is based upon these properties. In addition to that, important data regarding the values of the third variable are often specified. In the case of a higher value of a particular variable or parameter, the static property is expressed as parameter curves. When using static properties in calculations it is useful to express dependencies between variables with mathematical expressions. 1.2. Dynamic properties The dynamic properties define the behaviour of the variables with time. When speaking of dryer-type plants it is convenient to determine the dynamic behaviour and to present it in the form of transitive properties or as a response to the leap. Time diagrams of this kind indicate the potential occurrence of one variable’s response when the other variable changes its value by leaps. This data is used when determining the time and conduction modus of particular variables, which were changed in order to predict the behaviour of the latter. The dynamic behaviour is mathematically expressed in the form of differential equations. However, before determining a process using differential equations it is necessary to set up as many equations as there are variables. In order to use these equations on a specific object, the equation coefficients have to correspond with this object. In this case they have to correspond to the dryer. An overview of the drying-process results is presented with two differential equations. In practise they were tested by using a certain drying model, which was again used to determine the equation coefficients. Numerical solutions of these equations, and consequently the variables’ values, did not differ significantly. However, this system of differential equations was related to a very simple model and a lot of parameters and hypotheses were omitted. Accordingly, this drying process overview can be 52 Voča N. - Krička T. - Janušič V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 analizah, ne moremo pa ga uporabljati za potrebe delovanja določene sušilnice. 2 REZULTATI IN RAZPRAVA Iz izkušenj upravljanja osuševalnega postopka v težnostnih sušilnicah in ob upoštevanju medsebojnih vplivov velikega števila spremenljivk v prispevku predlagamo optimizacijo sistema znotraj posameznih funkcionalnih enot, ki vključujejo meritve in signalizacijo, upravljanje, avtomatsko krmiljenje, ustavitvene ukrepe in vodenje. 2.1 Meritve in signalizacija Meritve določenih spremenljivk ponujajo vpogled v način poteka postopka. Tako sledimo stalno spreminjajočim se spremenljivkam pa tudi mejnim in kritičnim spremenljivkam. Prve se nanašajo na vlago v vstopnih zrnih, temperaturo vročega zraka po končanem segrevanju, temperature posameznih predelov osuševalnega zraka, hitrost zračnega toka ali znižanje zračnega tlaka v sušilnici, temperaturo zraka v sušilnici in v hladilniku, temperaturo zrn ob izpustu iz sušilnice, fluktuacijo zrn v sušilnici, porabo goriva, temperaturo in vlažnost okolja ter vlažnost izhodnega zraka. Mejne in kritične spremenljivke se nanašajo na zasedenost sušilnice, dovod vlažnih zrn, najvišjo temperaturo v sušilnici, stanje motornih naprav itn. 2.2 Upravljanje Sklop upravljalnih naprav omogoči neposredno ali posredno vplivanje na osnovne spremenljivke postopka in s tem popravke postopka. Upravljanje izvajamo na tri načine: ročno, ročno na daljavo in avtomatsko. Spremenljivke, ki jih upravljamo, vključujejo mešanje vročega in zunanjega zraka, mešanje vročega in povratnega zraka, delovanje ventilacije (hitrost osuševalnega zraka in delovanje zapore za zrna) in hitrost zrn, ki potujejo skozi sušilnico. 2.3 Avtomatsko krmiljenje Z združitvijo meritvenih in upravljalskih funkcij z učinkovito negativno povratno zvezo je mogoče ustvariti krmilne zanke, ki pomagajo ohraniti used in some analyses, but it is not applicable when operating a specific dryer. 2 RESULTS AND DISCUSSION Using the experience of managing the drying process in gravity dryers, and based on the interde-pendencies of a great number of variables, this paper suggests organising the system for the purpose of its optimization through functional units, which include measurement and signalization, managing, automatic control, blocking effects and conduction. 2.1 Measurement and signalization The measurement of particular variables gives an insight into the way the process is being run. The continuously changeable variables, the borderline and the critical variables are monitored. The first relates to the moisture of the entering kernel, the hot-air temperature after the heating process, the section drying-air temperatures, the air-flow velocity or the air-pressure decrease in the dryer, the air temperature in the dryer and the cooler, the temperature of the exiting kernel, the kernel fluctuation in the dryer, the fuel consumption, the environmental temperature and the humidity, and the exiting air’s humidity. The borderline and critical variables relate to the dryer’s occupancy, the delivery of humid kernels, the maximum air temperature in the dryer, the condition of the motor device, etc. 2.2 Managing The group of managing devices enables a direct or indirect effect on the fundamental process variables and therefore ensures the process corrections. It is carried out in three steps, i.e., manually, remote manually, and automatically. The variables that are being managed include the hot-and outer-air mixing, the hot- and recurrent-air mixing, the ventilator operation (the velocity of the drying air, and the working of the kernel excluder) and the kernel velocity when passing through the dryer. 2.3 Automatic control By integrating the measuring and managing functions with a meaningful negative recurrent conjunction it is possible to deliver controlling circuits 53 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 vrednosti spremenljivk v določenih mejah. S tem preprečimo motnje, ki bi jih lahko povzročile nenadzorovane spremembe omenjenih spremenljivk kar pomeni, da z omenjenim postopkom zmanjšamo število spremenljivk, ki bi lahko povzročile prekinitev osuševalnega postopka. Krmilne funkcije izvajamo z naslednjimi sklopi opreme: - posameznimi krmilnimi zankami s stabilnimi vrednostmi; - posameznimi krmilnimi zankami z nastavljenimi vrednostmi; - industrijskim krmilnikom, ki združuje vse merjene in krmilne spremenljivke in vodi postopek. 2.4 Ustavitveni ukrepi Ko se sprožijo signali, ki opozarjajo na mejne in kritične vrednosti, se sprožijo določeni ustavitveni ukrepi za postopek. Ti so prilagojeni dogodkom v sušilnici in v sosednjih prostorih: povečanje temperature v sušilnici nad predpisano, premajhen dotok vlažnih zrn, motnje v postopku ogrevanja ali prekinitev delovanja katerihkoli bistvenih rabljenih naprav. 2.5 Vodenje Postopek vodenja vključuje ustaljeno in dinamično sinhronizacijo spremenljivk ali parametrov, tako da lahko kljub nekaterim nenadzorovanim spremembam ohranimo nespremenjene rezultate postopka in stalno kakovost pridelka. Ta postopek nadzoruje inteligentni industrijski krmilnik, čigar nastavitve moramo prilagoditi tovrstnemu opravilu (upoštevati moramo odvisnosti med spremenljivkami ter tehnološke in ekonomske kriterije). Krmilnik mora biti zmožen sprejeti več tipov podatkov, ki v obliki preglednic in diagramov izražajo ustaljene in dinamične lastnosti. Krmilnik izvaja tudi obdelavo podatkov, tako da podatke lahko prepozna kot matematične funkcije, ki jih nato preoblikuje v enačbe. Drugi tip podatkov so matematični izrazi. Tretji tip podatkov so posamezni podatki, ki določajo parametre postopka kakor na primer vrsta sušenega blaga, cena goriva itn. Nazadnje mora krmilnik sprejeti še podatke o določenem postopku, pridobljene od naprav za merjenje in signaliziranje, hkrati s podatki o vrednostih in spremembah nenadzorovanih spremenljivk. Ob uporabi vseh navedenih podatkov, krmilnik nenehno izvaja izračune, ki pomenijo temelj that can help in maintaining the variables’ values within set margins. This ensures the elimination of interferences caused by uncontrolled changes to these values, i.e., this leads to a decrease in the number of variables that can cause an interception of the drying process. The control functions are accomplished through a few levels of plant equipping: - single control circuits with stable values, - single control circuits with externally set values, - an industrial controller that unites all the measured and controlling variables and operates the process. 2.4 Blocking effects When borderline and critical values are being signalled, the critical values activate certain blocking effects in the process. They are specified by the dryer’s and attached buildings’ solutions: exceeding the prescribed dryer temperature, the shortage of humid kernel inflow, the interferences with the burner functions and the ending of the vital device functions in the plant. 2.5 Conduction The conduction procedure involves the static and dynamic synchronization of process variables or parameters, so that constant process results and constant product quality are preserved in spite of uncontrolled changes. This procedure is supervised by an intelligent industrial controller, which needs to be set up for this kind of operation (i.e., the dependencies between the variables and the technological and economic criteria need to be entered). The controller has to be able to accept a few types of data that contain the static and dynamic properties in the form of tables and diagrams. Data processing is also conducted by the controller so it can recognize them as mathematical functions, which are then transformed into equations. The second types of data are previously arranged mathematical expressions. The third forms are single data, which specify the process parameters such as the type of the drying material, the fuel price, etc. Finally, the controller has to accept the actual process data that are obtained from the measuring and signalling equipment, together with data relating to the values and changes of unmonitored variables. Using all the above-mentioned data, the controller continuously performs calculations, which 54 Voča N. - Krička T. - Janušič V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 Wi (%) AW, (1.1.) Wi (%) t (s) brez popravka without correction AW, (1.2.) ©air (°C)' to |^-| ------1„----------=> ^-H t (s) A©ai, y / (1.3.) W, (%) t (s) s popravkom with correction (1.4.) t (s) SI. 1. Dinamične lastnosti Fig. 1. Dynamic properties za nadzor spremenljivk in njihovo spreminjanje glede na vrednosti in čas. Še več, izračuni vsebujejo merila za optimalno krmiljenje postopka, ki pa jih lahko tudi spremenimo in jih prilagodimo želeni odvisnosti med kakovostjo osušenega pridelka, zmogljivostjo in porabo energije. Slike 1, 2 in 3 prikazujejo delovanje krmilnika. Glede na sliko 1.1 se v primeru, ko se začetni delež vlage v zrnih (w.) poveča med postopkom stabilnega sušenja,'drugi parametri pa ohranijo nespremenjene vrednosti, končni delež vlage v zrnih (w) poveča po preteku določenega časa prenosa (tj (si. 2.3). To povečanje se pokaže postopoma (si. 1.2) in z določeno časovno stalnico, t. Končna sprememba končnega deleža vlage bo W,(%) AW, (2.1.) W,(%) AW, (2.2.) AW, Wi (%) > bc i v A©ai, ©air ("C) ©air (°C), Vair(m/g) w (2.3.) začetni delež vlage v zmMnitial moisture content of kernel končni delež vlage v zrruh/final moisture content of kernel 0 . temperatura zraka pri osuševalnem postopku/air "temperature of drying process t čas susenja/drying period t čas prenosa pri osuševalnem postopku/transport period of drying process Qf poraba energije/energy consumption SI. 2. Ustaljene lastnosti Fig. 2. Static properties represent the basis for variables’ monitoring and their variation with value and time. Furthermore, the calculations include the conduction criteria for an optimal process, which can then be altered and consequently balanced to a desired dependence between the dried material’s quality, capacity and energy consumption. Figures 1, 2 and 3 show a controller-functioning system. According to Figure 1.1., if the initial kernel moisture content (w.) is increased during a stabilized drying process, while other parameters retain the same values, the final kernel moisture content (w) will be increased after a certain transport period^) (Fig. 2.3). This increase will manifest itself gradually (Fig. 1.2) with a particular time constant, . The final change of the final moisture content will be equal to the static to to w to Optimizacija neprekinjenega postopka sušenja - Optimization of the Performance of the Continuous-Drying 55 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 (3.1.) (3.2.) vair (m/s)j vair (m/s)" "> v^- hiti Dvair j \| Dvair v h" 1" kWf Wf (%) t0 t (sec) SI. 3. Ustaljene in dinamične lastnosti hitrosti osuševalnega zraka Fig. 3. Static and dynamic properties of the velocity of the drying air enaka ustaljeni lastnosti s slike 2.1. Popravki delovanja sušilnice, ki so zasnovani na podatkih o spremembi končnega deleža vlage, kažejo, da mora skozi sušilnico iti vsaj en tovor zrn z nezaželenim končnim deležem vlage. Za potrebe pridobitve primerno osušenih zrn lahko, po opravljenih meritvah začetnega deleža vlage v zrnih, vplivamo na več parametrov. Gre za naslednje mogoče spremembe: - povečanje temperature osuševalnega zraka, - povečanje hitrosti toka osuševalnega zraka, - podaljšanje časa sušenja. Glede na sliko 1 lahko odstranitev začetnega deleža vlage v zrnu, w., dosežemo s povečanjem temperature osuševalnega zraka za vredno st <9.r, ki jo za določen osuševani pridelek izračunamo z ustaljenimi lastnostmi s slike 2.2. Polna črta na sliki 1.3 kaže spremembo temperature osuševalnega zraka, ki je potrebna za doseganje kar najbolj učinkovite poprave končnega deleža vlage v zrnih. Po popravku bomo dobili končni delež vlage zrn, ki jo prikazuje polna črta na sliki 1.4. Če do temperaturnih sprememb pride kasneje, kakor to prikazuje prekinjena črta na sliki 1.3, bo končni delež vlage v zrnih vsebovala večjo napako, ki bo trajala dlje časa kakor napaka iz prvega primera (prekinjena črta na si. 1.4). Do nezadovoljivega rezultata bo prišlo tudi v primeru, ko se temperatura premočno poveča. V tem primeru bo imela napaka končnega deleža vlage v zrnih nasprotni predznak (pikčasti črti v si. 1.3 in 1.4). Če predpostavimo, da je povečanje hitrosti toka osuševalnega zraka kompenzacijska spremenljivka, lahko ustaljeno lastnost (si. 3.1) uporabimo v izračunih, ki posledično vplivajo na spremembo hitrosti zraka za vrednost Dvair. Zdaj tudi ugotovimo, da imajo dinamične lasTnosti temperaturne spremembe in hitrosti spremembe zračnega toka podobne časovne stalnice. To pomeni, da bo končno delovanje podobno, takšno, kakršnega prikazuje polna krivulja na sliki 1.4. property shown in Figure 2.1. The correction of the dryer functions, based on the data regarding the modification of the final moisture content suggests that at least one filling with an undesired final moisture content has to be passed through. By measuring the initial moisture content of the kernel for the purpose of obtaining qualitatively dried kernels, several parameters can be affected on time. They are: - an increase in the drying-air temperature, - an increase in the drying-air velocity flow, - a prolongation of the drying period. According to Figure 1, removing the initial moisture content of the kernel, wi, can be accomplished by increasing the drying-air temperature by Qair, which is calculated using the static properties shown in Figure 2.2 for a specific material that is being dried. The solid line shown in Figure 1.3 shows the change in the drying-air temperature that is required to achieve the most efficient correction of the final moisture content of the kernel. This will lead to the final moisture content of the kernel shown with the solid line in Figure 1.4. If the temperature changes begin later, as shown with the dashed line in Figure 1.3, the final moisture content of the kernel will have a greater error and will exist for longer than in the first case (the dashed line in Fig. 1.4.). An unsatisfactory result will also be achieved if there is a large effect on the temperature increase. In this case the final moisture content of the kernel will take an error of the opposite sign (the dotted lines shown in Figs. 1.3. and 1.4.). If an increase in the velocity of the drying air flow is considered as a compensating variable, then the static property (Fig. 3.1.) can be used in calculations, which subsequently affects the change in the air velocity by Dvair. Furthermore, it is clear that the dynamic properties of the temperature change and the velocity of the air-flow change have similar time constants. This means that the final functioning will be similar, as shown in the solid curve in Figure 1.4. 56 Voča N. - Krička T. - Janušič V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 Merila za odločitev med tema dvema The criteria for choosing between these two funkcijama so tehnološka in ekonomska. Krmilnik functions are technological and economic. The con- izvaja izračune, s katerimi ugotavlja, katera možnost troller performs calculations to determine which of je optimalna. Še več, krmilnik ima že nastavljena them is optimal. Moreover, it has already set techno- tehnološka merila, po katerih najvišja temperatura logical criteria, i.e., that the maximum drying-air tem- osuševalnega zraka ne sme biti presežena, perature cannot be exceeded, and that the increase povečanje hitrosti zračnega toka pa ne sme in the velocity of the air flow must not cause a povzročiti utekočinjenja. fluidization process. Če zgoraj opisani primeri vsebujejo If there is any hazard in the above-mentioned kakršnakoli tveganja, jih lahko preprečimo z ukrepi, situations, there are some measures that need to be kot npr. upočasnitev gibanja zrn skozi sušilnico s taken, such as slowing down the kernel’s movement podaljšanjem osuševalnega časa ali z zmanjšanjem through the dryer by prolonging the drying period zmogljivosti sušilnice. or by decreasing its capacity. V praksi manjšanje zmogljivost sušilnice In practice it is not common to decrease the sicer ni običajno; kljub temu pa v primeru, ko ima capacity of a dryer; however, if the dryer has an sušilnica neprimerno zmogljivost, ki ne ustreza inadequate capacity, which does not match the kernel’s naravnim razmeram osuševanja zrna, lahko pride natural conditions, i.e., its drying possibilities, this do povečane rabe energije, velikih razlik v deležu leads to an increase in energy consumption, large vlage v zrnih, tveganega skladiščenja in celo differences in the kernel’s moisture content, unsafe nevarnosti požara. storage and a possible fire hazard. 3 SKLEP 3 CONCLUSION Ne glede na finančne možnosti lastnikov Plants designated for process monitoring, sušilnic in njihovo opremljenost predmeti, izbrani za managing and conducting, unfortunately, do not nadzor, upravljanje in vodenje osuševalnega meet the present solutions in the Republic of Croatia postopka, žal ne ustrezajo trenutnim zahtevam v nor abroad, no matter what the financial potentials Republiki Hrvaški ali v tujini. Ne le, da niti najbolj of the dryer’s owner are or what equipment is avail- moderno opremljene sušilnice niso optimalno able. Indeed, even the most modern equipped dry- izkoriščene, njihovo delovanje ustvarja velike stroške ers are not only non-optimised, but in fact represent in daje nezanesljive rezultate. Na podlagi high costs and unreliable results. Based on such raziskovalnih poročil in poznavanja moderne reports and knowledge regarding the modern mikroprocesorske tehnologije lahko priporočimo achievements of microprocessor technology, it is rabo zgoraj opisane rešitve, tj. namestitev krmilnikov, advisable to introduce the above given solution, i.e., ki bodo krožno izvajali potrebne izračune. Ti izračuni to introduce controllers that will perform calculations so temelj za upravljanje s spremenljivkami, ki se v cyclically. These are a basis for managing the vari- določenem obdobju spremenijo, kar vodi v ables, so that they are modified by their value dur- optimizacijo osuševalnega postopka v gravitacijskih ing a certain period, which consequently leads to sušilnicah. optimization of the drying process in gravity dryers. Dodatna prednost opisanega predloga je v An additional property of the proposed tem, da je mogoče tehnična dela in finančne vložke solution is the possibility to realize in phases the investitorja izvesti postopno. Rezultati predlagane technical equipment and the financial possibilities rešitve so izboljšano in poenoteno delovanje of the investor. The results are better and uniform sušilnice, manjša poraba energije in boljša kakovost dryer functions with lower energy consumption and osušenih zrn. a better kernel quality. 4 LITERATURA 4 REFERENCES [1] Putier, F. (1993) Product quality and thermal treatment. Feed mix. 1(2), 34-37. Optimizacija neprekinjenega postopka sušenja - Optimization of the Performance of the Continuous-Drying 57 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 48-58 [2] [3] [4] [5] [6] [7] [8] [9] [10] [H] [12] [13] Brooker D. B., F. W. Bakker-Arkema, C. W. Hali (1992). Drying and storage of grain and oilseeds. Van Nostrana Reinhold. New York, USA. Mujumdar, A.S. (2000) Drying technology in agriculture science. Science Publisher, Enfield, USA Krička, T., N. Voča, Ž. Jukic, D. Kiš, S. Voča (2005) Motnje v postopku hlejanja koruznega zrnja v vertikalnih gravitacijskih sušilnicah. Strojniški vestnik - Journal of Mechanical Engineering. 51(4), 204-216. Li, H., R.V. Morey (1989) Thin-layer drying of yellow dent corn. Transactions of the American Society of Agricultural Engineers. 27(2), 581-585. Doyomaz, L, M. Pala (2003) The thin-layer drying characteristics of corn. Journal of Food Engineering. 60, 125-130 Soponronnarit, S., A. Pongtornkulpanich, S. Prachayawarakorn (1997) Corn quality after drying fluidiza-tion technique at high temperature. Drying Technology. 15(10), 2577-2586 Nedeljkov, M. L, M. P. Stakič (1987) Prikaz eksperimentalnog postrojenja i rezultata ispitivanja kinetike konvektivnog sušenja zrnatih kultura. Symposium proceedings. XV International Symposium of Technologists for Drying and Storing, Stubičke Toplice. 36-58. Katic, Z. (1985) Istodobno sušenje kukuruznog zrna raznih sorata i hibrida različite vlage na početku sušenja. Symposium proceedings. I International Symposium of Technologists for Drying and Storing. Stubičke Toplice, 86-104. Bratko, J. (1990) Neujednačenost vlage zrna kukuruza na izlazu iz sušare. Symposium Proceedings. VI International Symposium of technologists for drying and storing. Tuheljske Toplice. 108-116. Katic, Z., S. Pliestič, T. Krička, N. Kerep (1989) Utjecaj visokotemperaturnog predsušenja na energetski i materijalnu bilancu sušenja kukuruza Symposium Proceedings. V International Symposium of Technologists for Drying and Storing, Stubičke Toplice. 1-13. Miketinac, M. J., S. Sokansanj, Z. Tutek (1992) Odredivanje koeficijenta prijenosa mase i topline u isušivanju sloja. Symposium Proceedings. XV International Symposium of Technologists for Drying and Storing, Tuheljske Toplice. 14-23. Katic, Z. (1997) Sušenje i sušare u poljoprivredi, Multigraf doo. Zagreb. Naslov avtorjev: mag. Neven Voča Authors’ Address: Mag. Neven Voča prof. dr. Tajana Krička Prof. Dr. Tajana Krička Vanja Janušič Vanja Janušič Univerza v Zagrebu University of Zagreb Fakulteta za kmetijstvo Faculty of Agriculture Svetošimunska 25 Svetošimunska 25 10 000 Zagreb, Hrvaška 10 000 Zagreb, Croatia nvoca@agr.hr nvoca@agr.hr Prejeto: 13.3.2006 Received: Sprejeto: Accepted: 22.6.2006 Odprto za diskusij Open for discussio 58 Voča N. - Krička T. - Janušič V. Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 59-62 Osebne vesti - Personal Events Osebne vesti - Personal Events Prešernove nagrade za študente Fakultete za strojništvo v Ljubljani -Students’ Prešeren Awards of the Faculty of Mechanical Engineering in Ljubljana JANEZ GARVAS Naslov: Študija izvedljivosti proizvodnje bioplina 400 GVŽ za soproizvodnjo toplotne in električne energije Mentor: izr. prof. dr. Vincenc Butala Janez Garvas je bil rojen 24. avgusta 1981 v Ljubljani. Osnovno šolo je obiskoval v domačem kraju na Škofljici. Srednješolsko izobrazbo si je pridobil na Gimnaziji Ledina in uspešno maturiral leta 2000. Oktobra istega leta se je vpisal na Fakulteto za strojništvo v Ljubljani in septembra 2005 diplomiral na visokošolskem strokovnem študiju, smer energetsko in procesno strojništvo. V času študija je opravljal in sodeloval pri različnih projektih na področjih energetskega in procesnega strojništva. Oktobra istega leta se je vpisal na Fakulteti za strojništvo v program za pridobitev univerzitetne izobrazbe. V okviru Laboratorija za ogrevalno, sanitarno in solarno tehniko na Fakulteti za strojništvo je kandidiral na razpisano temo za Prešernovo nagrado in izvedel delo z naslovom: "Študija izvedljivosti pridobivanja bioplina 400 GVŽ za soproizvodnjo toplotne in električne energije". V omenjenem delu je obravnavana problematika soproizvodnje toplotne in električne energije iz ostankov, ki nastajajo pri vzreji govedi. Študija je izvedena s tehnično-procesnega in tudi ekonomskega vidika. ALEŠ BIZJAK Naslov: Optomehatronski sistem za rastrsko vodenje žarka pri laserskem označevanju Mentor: izr. prof. dr. Janez Diaci AlešBizjak je bil rojen 3. junija 1981 v Novem mestu. Osnovno šolo je obiskoval v Leskovcu pri Krškem, gimnazijo pa v Brežicah. Po maturi leta 2000 se je odločil za študij strojništva v Ljubljani. V tretjem letniku se je usmeril v študij mehatronike in ga junija 2006 tudi uspešno končal z zagovorom diplomske naloge "Krmilnik sistema za rastrsko vodenje žarka pri laserskem označevanju". Decembra 2006 se je zaposlil v podjetju I.H.S. d.o.o. v Krškem kot mladi raziskovalec. Nagrajenec je v okviru raziskave preučil izvedljivost in uporabnost rastrskega vodenja žarka pri laserskem označevanju. V ta namen je samostojno zasnoval in razvil izviren odklonski sistem na osnovi vrtljivega poligonskega zrcala in lečja, ki omogoča vodenje laserskega žarka po vrstici na tak način, da je gorišče žarka ves čas na površini obdelovanca. Delovanje sistema za rastrsko vodenje žarka je preizkusil in opredelil na laboratorijskem laserskem označevalnem sistemu. Pri tem je prikazal, da je sistem zlasti primeren za izdelavo večjih in/ali preprostejših označb na obdelovancih, ki se pomikajo po tekočem traku. V takšnih primerih je rastrski sistem tudi bistveno cenejši in hitrejši od sedanjih vektorskih. ALJAŽ OSTERMAN Naslov: Termični efekti kavitacije Mentor: prof. dr. Brane Širok Aljaž Osterman je bil rojen 20. decembra 1982 v Ljubljani. Po končani osnovni šoli je postal Zoisov štipendist, šolanje pa je nadaljeval na Gimnaziji Bežigrad, kjer je leta 2001 z odliko maturiral. V šolskem letu 2001/02 se je vpisal na Fakulteto za strojništvo v Ljubljani, kjer je v tretjem letniku izbral usmeritev Toplotni stroji in naprave na energetski smeri. Med študijem je bil večkrat nagrajen za najboljšega študenta v letniku. Dodiplomski študij je sklenil z zagovorom diplome v jeseni 2006. Sedaj je zaposlen na Fakulteti za strojništvo kot mladi raziskovalec, ukvarja pa se predvsem s kavitacijo. V nalogi je kandidat Aljaž Osterman predstavil nov - izviren postopek vrednotenja kavitacije s pomočjo računalniško podprte infrardeče termografije. V prvem delu naloge opiše eksperimentalno raziskavo kavitacije na osnovni (fenomenološki) ravni. V osrednjem delu naloge predstavi eksperimentalno metodo zaznavanja temperaturnih učinkov kavitacije. Postopek omogoča detekcijo temperaturnih polj neposredno na površini germanijevega stekla v stiku s kapljevino. Časovno in krajevno spreminjanje temperaturnih polj v mejni plasti kapljevine opazuje kot posledico propada 59 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 59-62 kavitacijskih mehurčkov, ki so nastali z ultrazvočnim vzbujanjem. Iz oblike in kinematike širjenja temperaturnih polj sklepa o intenzivnosti kavitacije. Na fenomenološki ravni oblikuje medsebojno povezavo med kavitacijo in termičnimi učinki kavitacije. Osnovni prispevek dela je novo razvita infrardeča termovizijska metoda merjenja kavitacijskih učinkov. Metoda bo uporabljena v nadaljnjih raziskavah temeljnih mehanizmov kavitacije, odpirajo pa se tudi možnosti razvoja eksperimentalne metode za diagnostiko kavitacije in erozijskih posledic. Delo je podano pregledno z jasnim opisom izhodišč naloge, dobljenimi rezultati in pogledom v prihodnje dejavnosti. URBAN MOHAR in JURIJ FERFOLJA Naslov: Analiza vpliva strukture (morfologije) na časovno odvisno vedenje polimerov Mentor: prof. dr. Igor Emri Urban Mohar je bil rojen 16. februarja 1981 v Ljubljani. Osnovno šolo je končal na Vrhniki in šolanje nadaljeval na Gimnaziji Ledina v Ljubljani. Leta 2000 se je vpisal na visokošolski študijski program Fakultete za strojništvo v Ljubljani. Dejaven je v Klubu vrhniških študentov. Trenutno je zaposlen v podjetju Ydria Motors. Jurij Ferfolja je bil rojen 1. februarja 1981 v Šempetru pri Gorici. Po končani osnovni šoli v Novi Gorici se je leta 1996 vpisal na Srednjo strojno tehnično šolo na Tehničnem šolskem centru Nova Gorica. V tem času se je dejavno ukvarjal s cestnim kolesarstvom, bil reden član mladinske kolesarske reprezentance v letih 1998 in 1999, nastopil na svetovnem mladinskem prvenstvu leta 1998 ter osvojil več medalj na mladinskih državnih prvenstvih. Leta 2002 se je vpisal na visokošolski študijski program Fakultete za strojništvo v Ljubljani. V študijskem letu 2004/05 je bil v sklopu študijske izmenjave na programu Erasmus Socrates 10 mesecev na Universität Politecnica de Catalunya v Barceloni. V prostem času dela kot sommelier za Slovensko turistično organizacijo, kjer skrbi za promocijo slovenskih vin na svetovnih turističnih borzah. Trenutno opravlja pripravništvo v razvojnem oddelku podjetja ITW Metalflex iz Tolmina in pripravlja diplomo. Delo obravnava nove možnosti spreminjanja funkcionalnosti polimernega izdelka s pomočjo spreminjanja strukture materiala v fazi predelovanja in posledično njegovega časovno odvisnega vedenja, ki opredeljuje trajnost končnega izdelka. Predstavljena raziskava išče odgovore na dvoje vprašanj: (i) ali je mogoče s sedanjo opremo za procesiranje polimerov v industrijskem okolju (npr. ekstrudiranje) ustvariti razmere, pri katerih se pojavijo nelinearni postopki med oblikovanjem strukture materiala, in (ii) kolikšne spremembe strukture in posledično mehanske in druge lastnosti končnega polimernega izdelka lahko dosežemo v industrijskem okolju s spremembami v tehnologiji (tj., s spremembo parametrov postopkov). Rezultati predstavljene analize kažejo, da je mogoče tehnološke razmere v območju temperatur in tlakov, tipičnih za iztiskovanje polimerov v industrijskih razmerah, spremeniti tako, da pomembno vplivamo na oblikovanje strukture in posledično na časovno odvisne mehanske lastnosti materiala in s tem na funkcionalnost končnega izdelka. Avtorja raziskave pokažeta, da je s spremembami postopkovnih parametrov v območju industrijskih razmer mogoče izboljšati trajnost za več velikostnih razredov. To odpira nove možnosti na področju spreminjanja funkcionalnosti polimernih izdelkov in s tem povečevanje njihove konkurenčne zmožnosti na svetovnem trgu. JANČERNETIČ Naslov: Aktivno dušenje hrupa na primeru prezračevalnega kanala Mentor: prof. dr. Mirko Čudina Jan Černelič je bil rojen 11. junija 1982 v Ljubljani. Osnovno šolo je obiskoval v Logu pri Brezovici, leta 1997 se je vpisal na Gimnazijo Jožeta Plečnika. Po maturi leta 2001 se je vpisal na univerzitetni študij Fakultete za strojništvo v Ljubljani in se usmeril v energetsko strojništvo. I. del strokovne prakse je opravil leta 2002 v Laboratoriju za eksperimentalno mehaniko, II. del pa leta 2005 v podjetju IMS Industrijski merilni sistemi na področju merjenja in vrednotenja hrupa. Leta 2006 je z odliko diplomiral na področju aktivnega dušenja hrupa. Istega leta je kandidiral za mesto mladega raziskovalca na Fakulteti za strojništvo in bil tudi sprejet. V času študija je dejavno sodeloval z laboratorijem za delovne stroje in tehnično akustiko v okviru katerega je izdelal nalogo z naslovom "Aktivno dušenje hrupa na primeru prezračevalnega kanala". Kandidat je v delu podrobneje predstavil zančno 60 Osebne vesti - Personal Events Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 59-62 strukturo pri dejavnem dušenju hrupa. Opravil je tudi številne preizkuse z namenom izdelati čimbolj preprost in učinkovit analogni sistem dejavnega dušenja hrupa v prezračevalnem kanalu. Namen je bil prikazati, da je učinkovit sistem mogoče narediti tudi brez uporabe elektronskih ali analognih filtrov ter krmilnikov. V ožjem frekvenčnem pasu je dosegel zmanjšanje hrupa za 18 dB(A), največja raven dušenja pa je znašala 22 dB(A). MITJA MAZEJ Naslov: Polje koncentracij primesi pri lokalni klimatizaciji Mentor: izr. prof. dr. Vincenc Butala Mitja Mazej je bil rojen 21. maja 1982 v Celju, kjer je obiskoval osnovno šolo in gimnazijo. Po DOKTORATI Na Fakulteti za strojništvo Univerze v Ljubljani so z uspehom zagovarjali svoje doktorske disertacije: dne 5. decembra 2006: Boštjan Drobnič, z naslovom: "Tokovne in temperaturne razmere v rotacijskem regenerativnem prenosniku toplote" (mentorja: prof. dr. Janez Oman in prof. dr. Matija Tuma); dne 8. decembra 2006: Tadej Kokalj, z naslovom: "Modeliranje in optimizacija laserskega tvorjenja kapljic iz kovinske žice" (mentorja: prof. dr. Edvard Govekar in prof. dr. Igor Grabeč); dne 22. decembra 2006: Boštjan Černe, z naslovom: "Vpliv večdimenzijskega prenosa toplote na toplotni odziv lahkih gradbenih elementov" (mentor: prof. dr. Sašo Medved) in Nikola Holeček, z naslovom: "Modeliranje aerodinamičnih lastnosti kondenzatorjev sušilnih strojev nove generacije" (mentorji: prof. dr. Brane Širok, prof. dr. Mirko Čudina in prof. dr. Rudolf Podgornik). Na Fakulteti za strojništvo Univerze v Mariboru sta z uspehom zagovarjala svoji doktorski disertaciji: dne 15. decembra 2006: mag. Andrej Godina, z naslovom: "Merilna negotovost pri kalibraciji merilnih kladic iz različnih materialov po postopku mehanske primerjave" (mentor: prof. dr. Janko Drnovšek); dne 18. decembra 2006: mag. Matejka Turel, z naslovom: "Razvoj novih optičnih uspešno opravljeni maturi leta 2001 se je vpisal na Fakulteto za strojništvo Univerze v Ljubljani, kjer je 30. junija 2006 diplomiral na smeri Energetsko in procesno strojništvo, usmeritev toplotna tehnika -procesno strojništvo. Za Prešernovo nagrado je kandidiral z razpisano temo "Polje koncentracij primesi pri lokalni klimatizaciji". V delu je bilo analizirano delovanje sistema za lokalno klimatizacijo delovnega mesta na podlagi opravljenih meritev hitrosti zraka in koncentracij slednega plina z uporabo metode zmanjševanja Takoj po diplomiranju se je za krajši čas zaposlil v zasebnem podjetju v Celju, od 1. novembra 2006 dalje pa je zaposlen na Fakulteti za strojništvo Univerze v Ljubljani kot mladi raziskovalec na področju energetike v Laboratoriju za ogrevalno, sanitarno in solarno tehniko. senzorskih sistemov za spremljanje anorganskih parametrov odpadne vode" (mentorja: prof. dr. Aleksandra Lobnik in prof. dr. Otto S. Wolfbeis); S tem so navedeni kandidati dosegli akademsko stopnjo doktorja znanosti. MAGISTERIJA Na Fakulteti za strojništvo Univerze v Ljubljani je z uspehom zagovarjal svoje magistrsko delo: dne 21. decembra 2006: Martin Mele, z naslovom: "Spajanje aluminija z gnetenjem" (mentor: prof. dr. Janez Tušek). Na Fakulteti za strojništvo Univerze v Mariboru je z uspehom zagovarjala svoje magistrsko delo: dne 13. decembra 2006: Marija Pintar, z naslovom: "Industrijski tekstilni odpadki v Sloveniji in njihovo recikliranje" (mentorja: prof. dr. Bojana Vončina in prof. dr. Niko Samec). S tem sta navedena kandidata dosegla akademsko stopnjo magistra znanosti. DIPLOMIRALI SO Na Fakulteti za strojništvo Univerze v Ljubljani sta pridobila naziv univerzitetni diplomirani Doktorati, magisterija in diplome - Doctor’s, Master’s and Diploma Degrees Osebne vesti - Personal Events 61 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 59-62 inženir strojništva: dne 27. decembra 2006: Metod IVANČIČ. Tomaž OŠTIR. Na Fakulteti za strojništvo Univerze v Mariboru sta pridobila naziv univerzitetni diplomirani inženir strojništva: dne 21. decembra 2006: Peter GROBELNIK, Teo VIDA. * Na Fakulteti za strojništvo Univerze v Ljubljani so pridobili naziv diplomirani inženir strojništva: dne 14. decembra 2006: Matej DURIČ, Kristijan KRAJNIK, Aleš KUŽMK, Luka LEVSTEK, Andrej MEDVEDEC, Matej MOŽINA, Primož TEKAVEC, Jernej VUGA; dne 18. decembra 2006: Vojko LAJOVEC, Gregor KLINC, Matjaž RUPNIK, Aleksandar ILIČ. Na Fakulteti za strojništvo Univerze v Mariboru so pridobili naziv diplomirani inženir strojništva: dne 4. decembra 2006: Marko MALAVAŠIČ; dne 21. decembra 2006: Igor KAPITAN, Martin PETRIČ, Miran POPIČ, Roman ŠUŠTARŠIČ. 62 Osebne vesti - Personal Events Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 63-64 Navodila avtorjem - Instructions for Authors Navodila avtorjem - Instructions for Authors Članki morajo vsebovati: - naslov, povzetek, besedilo članka in podnaslove slik v slovenskem in angleškem jeziku, - dvojezične preglednice in slike (diagrami, risbe ali fotografije), - seznam literature in - podatke o avtorjih. Strojniški vestnik izhaja od leta 1992 v dveh jezikih, tj. v slovenščini in angleščini, zato je obvezen prevod v angleščino. Obe besedili morata biti strokovno in jezikovno med seboj usklajeni. Članki naj bodo kratki in naj obsegajo približno 8 strani. Izjemoma so strokovni članki, na željo avtorja, lahko tudi samo v slovenščini, vsebovati pa morajo angleški povzetek. Za članke iz tujine (v primeru, da so vsi avtorji tujci) morajo prevod v slovenščino priskrbeti avtorji. Prevajanje lahko proti plačilu organizira uredništvo. Če je članek ocenjen kot znanstveni, je lahko objavljen tudi samo v angleščini s slovenskim povzetkom, ki ga pripravi uredništvo. Članek naj bo napisan v naslednji obliki: - Naslov, ki primerno opisuje vsebino članka. - Povzetek, ki naj bo skrajšana oblika članka in naj ne presega 250 besed. Povzetek mora vsebovati osnove jedro in cilje raziskave, uporabljeno metodologijo dela,povzetek rezulatov in osnovne sklepe. - Uvod, v katerem naj bo pregled novej šega stanja in zadostne informacije za razumevanje ter pregled rezultatov dela, predstavljenih v članku. - Teorija. - Eksperimentalni del, ki naj vsebuje podatke o postavitvi preskusa in metode, uporabljene pri pridobitvi rezultatov. - Rezultati, ki naj bodo jasno prikazani, po potrebi v obliki slik in preglednic. - Razprava, v kateri naj bodo prikazane povezave in posplošitve, uporabljene za pridobitev rezultatov. Prikazana naj bo tudi pomembnost rezultatov in primerjava s poprej objavljenimi deli. (Zaradi narave posameznih raziskav so lahko rezultati in razprava, za jasnost in preprostejše bralčevo razumevanje, združeni v eno poglavje.) - Sklepi, v katerih naj bo prikazan en ali več sklepov, ki izhajajo iz rezultatov in razprave. - Literatura, ki mora biti v besedilu oštevilčena zaporedno in označena z oglatimi oklepaji [1] ter na koncu članka zbrana v seznamu literature. Vse opombe naj bodo označene z uporabo dvignjene številke1. Besedilo članka naj bo pripravljeno v urejevalnilku Microsoft Word. Članek nam dostavite v elektronski obliki. Ne uporabljajte urejevalnika LaTeX, saj program, s katerim pripravljamo Strojniški vestnik, ne uporablja njegovega formata. Enačbe naj bodo v besedilu postavljene v ločene vrstice in na desnem robu označene s tekočo številko v okroglih oklepajih Papers submitted for publication should comprise: - Title, Abstract, Main Body of Text and Figure Captions in Slovene and English, - Bilingual Tables and Figures (graphs, drawings or photographs), - List of references and - Information about the authors. Since 1992, the Journal of Mechanical Engineering has been published bilingually, in Slovenian and English. The two texts must be compatible both in terms of technical content and language. Papers should be as short as possible and should on average comprise 8 pages. In exceptional cases, at the request of the authors, speciality papers may be written only in Slovene, but must include an English abstract. For papers from abroad (in case that none of authors is Slovene) authors should provide Slovenian translation. Translation could be organised by editorial, but the authors have to pay for it. If the paper is reviewed as scientific, it can be published only in English language with Slovenian abstract, that is prepared by the editorial board. The paper should be written in the following format: - A Title, which adequately describes the content of the paper. - An Abstract, which should be viewed as a mini version of the paper and should not exceed 250 words. The Abstract should state the principal objectives and the scope of the investigation, the methodology employed, summarize the results and state the principal conclusions. - An Introduction, which should provide a review of recent literature and sufficient background information to allow the results of the paper to be understood and evaluated. - A Theory - An Experimental section, which should provide details of the experimental set-up and the methods used for obtaining the results. - A Results section, which should clearly and concisely present the data using figures and tables where appropriate. - A Discussion section, which should describe the relationships and generalisations shown by the results and discuss the significance of the results making comparisons with previously published work. (Because of the nature of some studies it may be appropriate to combine the Results and Discussion sections into a single section to improve the clarity and make it easier for the reader.) - Conclusions, which should present one or more conclusions that have been drawn from the results and subsequent discussion. - References, which must be numbered consecutively in the text using square brackets [1] and collected together in a reference list at the end of the paper. Any footnotes should be indicated by the use of a superscript1. Texts should be written in Microsoft Word format. Paper must be submitted in electronic version. Do not use a LaTeX text editor, since this is not compatible with the publishing procedure of the Journal of Mechanical Engineering. Equations should be on a separate line in the main body of the text and marked on the right-hand side of the page with numbers in round brackets. VSEBINA ČLANKA THE FORMAT OF THE PAPER OBLIKACLANKA THE LAYOUT OF THE TEXT 63 Strojniški vestnik - Journal of Mechanical Engineering 53(2007)1, 63-64 Enote in okrajšave V besedilu, preglednicah in slikah uporabljajte le standardne označbe in okraj save SI. Simbole fizikalnih veličin v besedilu pišite poševno (kurzivno), (npr. v, T, n itn.). Simbole enot, ki sestojijo iz črk, pa pokončno (npr. ms1, K, min, mm itn.). Vse okrajšave naj bodo, ko se prvič pojavijo, napisane v celoti v slovenskem jeziku, npr. časovno spremenljiva geometrija (ČSG). Slike Slike morajo biti zaporedno oštevilčene in označene, v besedilu in podnaslovu, kot si. 1, si. 2 itn. Posnete naj bodo v ločljivosti, primerni za tisk, v kateremkoli od razširjenih formatov, npr. BMP, JPG, GIF. Diagrami in risbe morajo biti pripravljeni v vektorskem formatu, npr. CDR, Al. Pri označevanju osi v diagramih, kadar je le mogoče, uporabite označbe veličin (npr. t, v, m itn.), da ni potrebno dvojezično označevanje. V diagramih z več krivuljami, mora biti vsaka krivulja označena. Pomen oznake mora biti pojasnjen v podnapisu slike. Vse označbe na slikah morajo biti dvojezične. Preglednice Preglednice morajo biti zaporedno oštevilčene in označene, v besedilu in podnaslovu, kot preglednica 1, preglednica 2 itn. V preglednicah ne uporabljajte izpisanih imen veličin, ampak samo ustrezne simbole, da se izognemo dvojezični podvojitvi imen. K fizikalnim veličinam, npr. t (pisano poševno), pripišite enote (pisano pokončno) v novo vrsto brez oklepajev. Vsi podnaslovi preglednic morajo biti dvojezični. Seznam literature Vsa literatura mora biti navedena v seznamu na koncu članka v prikazani obliki po vrsti za revije, zbornike in knjige: [1] A. Wagner, I. Bajsič, M. Fajdiga (2004) Measurement of the surface-temperature field in a fog lamp using resistance-based temperature detectors, Stroj. vestn. 2(2004), pp. 72-79. [2] Vesenjak, M., Ren Z. (2003) Dinamična simulacija deformiranja cestne varnostne ograje pri naletu vozila. Kuhljevi dnevi ’03, Zreče, 25.-26. september 2003. [3] Muhs, D. et al. (2003) Roloff/Matek Maschinenelemente - Tabellen, 16. Auflage. Vieweg Verlag, Wiesbaden. SPREJEM ČLANKOV IN AVTORSKE PRAVICE Uredništvo Strojniškega vestnika si pridržuje pravico do odločanja o sprejemu članka za objavo, strokovno oceno recenzentov in morebitnem predlogu za krajšanje ali izpopolnitev ter terminološke in jezikovne korekture. Avtor mora predložiti pisno izjavo, da je besedilo njegovo izvirno delo in ni bilo v dani obliki še nikjer objavljeno. Z objavo preidejo avtorske pravice na Strojniški vestnik. Pri morebitnih kasnejših objavah mora biti SV naveden kot vir. PLAČILO OBJAVE Avtorji vseh prispevkov morajo za objavo plačati prispevek v višini 20,00 EUR na stiskano stran prispevka. Prispevek se zaračuna po sprejemu članka za objavo na seji Uredniškega odbora. 64 Units and abbreviations Only standard SI symbols and abbreviations should be used in the text, tables and figures. Symbols for physical quantities in the text should be written in italics (e.g. v, T, n, etc.). Symbols for units that consist of letters should be in plain text (e.g. ms1, K, min, mm, etc.). All abbreviations should be spelt out in full on first appearance, e.g., variable time geometry (VTG). Figures Figures must be cited in consecutive numerical order in the text and referred to in both the text and the caption as Fig. 1, Fig. 2, etc. Pictures may be saved in resolution good enough for printing in any common format, e.g. BMP, GIF, JPG. However, graphs and line drawings sholud be prepared as vector images, e.g. CDR, AI. When labelling axes, physical quantities, e.g. t, v, m, etc. should be used whenever possible to minimise the need to label the axes in two languages. Multi-curve graphs should have individual curves marked with a symbol, the meaning of the symbol should be explained in the figure caption. All figure captions must be bilingual. Tables Tables must be cited in consecutive numerical order in the text and referred to in both the text and the caption as Table 1, Table 2, etc. The use of names for quantities in tables should be avoided if possible: corresponding symbols are preferred to minimise the need to use both Slovenian and English names. In addition to the physical quantity, e.g. t (in italics), units (normal text), should be added in new line without brackets. All table captions must be bilingual. The list of references References should be collected at the end of the paper in &e Mowing styles for journals, proceedings and books, respectively: [1] A. Wagner, I. Bajsič, M. Fajdiga (2004) Measurement of the surface-temperature field in a fog lamp using resistance-based temperature detectors, Stroj. vestn. 2(2004), pp. 72-79. [2] Vesenjak, M., Ren Z. (2003) Dinamična simulacija deformiranja cestne varnostne ograje pri naletu vozila. Kuhljevi dnevi ’03, Zreče, 25.-26. september 2003. [3] Muhs, D. et al. (2003) Roloff/Matek Maschinenelemente - Tabellen, 16. Auflage. Vieweg Verlag, Wiesbaden. ACCEPTANCE OF PAPERS AND COPYRIGHT The Editorial Committee of the Journal of Mechanical Engineering reserves the right to decide whether a paper is acceptable for publication, obtain professional reviews for submitted papers, and if necessary, require changes to the content, length or language. Authors must also enclose a written statement that the paper is original unpublished work, and not under consideration for publication elsewhere. On publication, copyright for the paper shall pass to the Journal of Mechanical Engineering. The JME must be stated as a source in all later publications. PUBLICATION FEE For all papers authors will be asked to pay a publication fee prior to the paper appearing in the journal. However, this fee only needs to be paid after the paper is accepted by the Editorial Board. The fee is €20.00 per printed paper page.