COMPARATIVE STUDY OF LARGE EDDY AND K-ε MODELING OF DIESEL SPRAY COMBUSTION USING PaSR MODEL

In this paper, Turbulent spray combustion is studied in a constant volume chamber using large eddy simulation (LES) method and partially stirredreactor(PaSR) by further development of an Eulerian – Lagrangian two phase computer code. This improvement was made by implementing theLES turbulence model and PaSR combustion model. In LES method the large scale eddies are solved directly and small scale eddies are modeled.Therefore, it can potentially improve the predictive capability by better capturing the large scale mixing of ambient air with the fuel vapor.Validation of the home-made computer code performance is carried out in two steps. Firstly, results of non-reacting spray tip penetration lengthin gas environment is compared with experimental data. In the second step results of velocity profile and fluctuation velocity during the intake stage arecompared with related experimental data. Results of LES method shows a better agreement with experimental data than RANS method. Also,Simulations of reacting liquid spray and fuel vapor tip penetration length are compared with experimental data in constant volume chamberusing LES method. It is shown that overall characteristics of diesel spray combustion such as liquid spray and fuel vapor tip penetration are bothin good agreement with experimental data using LES (smagorinesky and dynamic smagorinesky) in comparison to RANS (standard k   ). Maximumand minimum temperatures are predicted to be the same in both methods, but LES (dynamic based model) predicts small eddies and makes the flameshape and lift-off length more similar to experimental one.

کلیدواژه ها:

Turbulence ، Diesel Spray combustion ، Large Eddy Simulation (LES) ، Reynolds Averaged of Navier Stocks (RANS) ، Diesel Engine ، Partially Stirred Reactor (PaSR)