9546 KB281 KB0 KB2022Kokalj, FilipZadravec, TomasXIV, 133 str., 30 cmCOBISSID:127263491URN:URN:NBN:SI:doc-5M4V5SXGslT. Zadravecvisokošolska delacombustioncombustion temperaturecomputational fluid dynamics (CFD)Disertacijeeksperimentalno deloemission measurementsempirical fuel bed modelempirični modeli zgorevanjaexperimental workfiksna rešetkafixed grateLesni peletimale kurilne napravemeasurements of process parametersmeritve emisijmeritve procesnih parametrovračunalniška dinamika tekočin (RDT)small-scale boilertemperatura zgorevanjaUniverzitetna in visokošolska delawood pelletsZgorevanjeEksperimentalno podprt numerični model za simulacijo zgorevanja lesnih pelet v mali kurilni napravi| doktorska disertacija|The commercial wood pellet boiler was structurally modified so that it was possible to perform measurements of various parameters during operation. Several vital process parameters were determined: (1) basic boiler operating parameters such as cooling water temperature, cooling water flow, flue gas temperature and fuel supply, (2) emissions, i.e.. concentrations of several pollutants in the flue gases, (3) combustion temperatures and flue gases in the combustion chamber, and (4) airflows entering the combustion chamber. The results of the experimental work served to establish and validate a numerical combustion simulation. In this work, the combustion modelling is performed by introducing a two-way exchange between the fuel ned conversion model and the gas phase combustion simulation. Solid fuel conversion is modelled with an empirical 1D fuel layer model, which depends on the measured operating parameters, fuel properties and empirical description of the solid fuel conversion process. Two cases were investigated numerically. Example A is a representative of a “weak” staged air supply strategy, and example B is a “strong” strategy. The results showed that the temperatures predicted by the CFD followed the same trend as the measured values, although on average they were too high. The CFD forecasts of CO emissions showed the same trend as the measurements, but in the transition from a weak to a strong combustion strategy, a reduction of 69 % was predicted compared to the measured CO reduction. The CFD forecasts of NO emissions showed the same trend as the measurements, but in the transition from a weak to a strong staged combustion strategy, a 10 % higher reduction was predicted compared to the measured NO reduction. Despite the excessive temperature forecast, taking into account the engineering modelling approach with many simplifications and unknowns, the accuracy of emission forecasts can be considered sufficient for engineering purposes. The presented modelling approach could thus be used to evaluate new process parameters, geometric designs and configurations of secondary air supply nozzlesKomercialni toplovodni kotel na lesene pelete je bil konstrukcijsko spremenjen tako, da je bilo mogoče izvajati merjenje procesnih parametrov tekom obratovanja. Med eksperimentalno preiskavo je bilo izmerjenih in zabeleženi več vitalnih procesnih parametrov: (1) osnovni parametri delovanja kotla, kot so temperatura hladilne vode, pretok hladilne vode, temperatura dimnih plinov in dovajanje goriva, (2) emisije snovi, tj. koncentracije več vrst snovi v dimnih plini, (3) temperature zgorevanja in dimnih plinov v zgorevalni komori in (4) pretoki zračnih tokov, ki so vstopali v zgorevalno komoro. Rezultati eksperimentalnega dela so služili vzpostavitvi in validacijo numerične simulacije zgorevanja. V tem delu je modeliranje zgorevanja izvedeno z uvedbo dvosmerne izmenjave med modelom pretvorbe sloja goriva in simulacijo zgorevanja plinske faze. Pretvorba trdnega goriva je modelirana z empiričnim 1D modelom gorivne plasti, ki je odvisen od izmerjenih obratovalnih parametrov, lastnosti goriva in empiričnega opisa procesa pretvorbe trdnega goriva. Numerično sta bila raziskana dva primera. Primer A je predstavnik »šibke« strategije stopenjskega dovajanja zraka, primer B pa »močne« strategije. Rezultati so pokazali da so temperature napovedane z RDT so sledile enakemu trendu kot izmerjene vrednosti, čeprav so bile v povprečju previsoke. RDT napovedi emisij CO so pokazale enak trend kot meritve, vendar je bilo pri prehodu s šibke na močno strategijo zgorevanja po stopnjah, napovedana za 69 % nižja redukcija v primerjavi z izmerjeno redukcijo CO. RDT napovedi emisij NO so pokazale enak trend kot meritve, vendar je bilo pri prehodu s šibkega na močno strategijo zgorevanja po stopnjah, napovedana za 10 % višja redukcija v primerjavi z izmerjeno redukcijo NO. Kljub preveliki napovedi temperature, ob upoštevanju pristopa inženirskega modeliranja s številnimi poenostavitvami in neznankami, lahko natančnost napovedi emisij štejemo za zadostno za inženirske namene. Predstavljeni pristop modeliranja bi tako lahko uporabili za vrednotenje novih procesnih parametrov, geometrijskih zasnov in konfiguracij šob za dovod SZTEXTvisokošolska delatheses and dissertationsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Mariboru, Fakulteta za strojništvo