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Effects of split injection with different EGR rate on combustion process and pollutant emissions in a DI diesel engine have been evaluated with CFD modeling. The model was validated with experimental data achieved from a Caterpillar 3401 DI diesel engine and 3D CFD simulation was carried out from intake valve closing (IVC) to exhaust valve opening (EVO). Totally 12 different injection strategies for which two injection pulses with different fuel amount for each pulse (up to 30% for the second pulse) and different separation between two pulses (up to 30° CA) were evaluated. Results show that adequate injection separation and enough fuel amount of the second pulse could form a separate 2nd stage of heat release which could reduce the peak combustion temperature and improve the oxidation of soot formed in the first heat release stage.

An advanced turbulence modeling using Large Eddy Simulation (LES) has been employed for studying diesel engine flow and its effects on combustion process and amount of pollutant emissions in a DI Diesel engine. An improved version of the Extended Coherent Flame Model combustion model (ECFM-3Z) coupled with advanced models for NOx and soot formation has been applied for CFD simulation. The model performance was assessed by comparison of the calculation results with corresponding experimental data. Very good agreement of calculated and measured in-cylinder pressure, heat release rate as well as pollutant formation trends were obtained. The simulation results was further compared with those obtained by traditional Reynolds-averaged Navier-Stokes model (RANS) at three different mesh resolutions. It was concluded that sensivity of LES approach to geometric details is affected by increasing resolution as compared to existing RANS.