3889 KB42 KB199920252014Jošt, DragicaLipej, AndrejŠkerlavaj, Aljažštevilka:2letnik:60str. 124-134, SI 25ISSN:0039-2480COBISSID:13354267URN:URN:NBN:SI:doc-LZS0BROKenZveza strojnih inženirjev in tehnikov Slovenije et al.Strojniški vestnikaksialne turbinenapoved izkoristkaračunalniška dinamika tekočinturbulentni modelivodne turbineZLESImprovement of efficiency prediction for a Kaplan turbine with advanced turbulence models|A comparison between numerical simulations and measurements of a six-blade Kaplan turbine is presented in order to determine anappropriate numerical setup for accurate and reliable simulations of Kaplan turbines. Values of discharge, torque and losses obtained bydifferent turbulence models are compared to each other and to the measurements. Steady state simulations with various turbulence modelstend to predict large errors at full discharge rate, which are the result of underestimated torque on the shaft and overestimated flow energylosses in the draft tube. The results were slightly improved with the curvature correction (CC) and Kato-Launder (KL) limiter of turbulenceproduction. Transient simulations were performed with shear-stress-transport (SST) turbulence model, the scale-adaptive-simulation (SAS) SSTmodel, and with zonal large-eddy-simulation (ZLES). Details about turbulent structures in the draft tube are illustrated in order to explain thereasons for differences in flow energy losses obtained by different turbulence models. The effects of advection schemes and mesh refinementwere tested. It was shown that all of the transient simulations considerably improved results at full discharge rate. The largest improvementwas achieved with the SAS SST and the ZLES models in combination with the bounded central differential scheme. In addition, it was shownthat the ZLES model produced accurate results at all operating points, with discrepancy lower than 1%Numerična analiza toka je v minulih dvajsetih letih pomembno prispevala k razumevanju pojavov v aksialnih vodnih turbinah in k izboljšanju njihovih karakteristik. Dokaj natančno lahko napovemo vpliv sprememb hidravličnih oblik na izkoristek turbine, manj točna pa je napoved same vrednosti izkoristka. Namen tega članka je pokazati, zakaj lahko s stacionarnimi izračuni dobimo napačne rezultate in kako jih s časovno odvisnimi izračuni in naprednimi turbulentnimi modeli bistveno izboljšamo.V ta namen smo numerično analizirali tok v 6-lopatični Kaplanovi turbini za srednje padce. Model turbine je bil preizkušen na merilni postaji v Turboinštitutu v skladu z mednarodnimi standardi IEC 60193. Obravnavali smo tri kote gonilnih lopatic pri konstantnem padcu. Rezultati preračuna so navor na gredi turbine, izgube v posameznih delih turbine in izkoristek ter pretok ali padec. Kadar je podan padec, je rezultat preračuna pretok, in obratno. Numerične rezultate, razen izgub, smo primerjali z izmerjenimi vrednostmiTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Ljubljani, Fakulteta za strojništvo