Numerical modelling of spray and combustion process

Korištenje Računalne Dinamike Fluida (RDF) u kombinaciji s eksperimentalnim istraživanjem postalo je uobičajeni pristup u razvijanju dizel motora. U ovom radu je prikazana usporedba rezultata numeričke simulacija izgaranja u dizel motoru koristeći komercijalni programski paket AVL FIRE® s eksperimentalnim podacima. Eksperimentalni podaci su dobiveni u suradnji s Fakultetom Strojarstva, Sveučilišta u Ljubljani. Karakteristično za promatrani eksperimentalni dizel motor je pojedinačno ubrizgavanje goriva u pred ubrizgavanju i u glavnom ubrizgavanju. Izgaranjem relativno male količine isparenog goriva ubrizganog u pred ubrizgavanju postiže se viši tlak unutar cilindra prije glavnog ubrizgavanja. Glavno ubrizgavanje počinje u trenutku kad je klip u blizini gornje mrtve točke. U ovom radu također je prikazan usporedba između modela izgaranja ECFM 3Z+ i kemijskog mehanizma. Na kraju je prikazana analiza eksperimentalnih podataka i rezultata simulacija za dva radna stanja motora. Rezultati tlaka i temperature u cilindru te brzina oslobođene topline dobivena iz numeričkih simulacija prikazuju dobro poklapanje s eksperimentalnim podacima.Using CFD in combination with experimental research has become a standard approach in the development of Diesel engines. In this work, the numerical simulation of Diesel engine combustion process with the commercial 3D Computational Fluid Dynamics (CFD) software AVL FIRE® is compared with the experimental data. The experimental data was provided by collaboration with the Faculty of Mechanical Engineering, the University of Ljubljana. Characteristic for the observed experimental Diesel engine is that the liquid fuel is injected through the pilot and main injections. The pilot injection is used to produce an amount of vapour that later ignites, and increases the mean in-cylinder temperature. At later crank angle positions the main injection occurs. The comparison between modelling results obtained with the combustion model ECFM 3Z+ and chemical mechanism is shown. Furthermore, an investigation of the calculated and the experimental data for two different engine operating points is presented. The results from numerical simulations, such as the mean pressure, mean temperature, and the rate of heat release are found to be in agreement with the experimental data