Numerical Investigation on the Effect of Injection Timing on Combustion and Emissions in a DI Diesel Engine at Low Temperature Combustion Condition

One promising way to achieve low temperature combustion regime is using a large amountof cooled EGR. In this paper, the effect of injection timing on low temperature combustion process and emissions were investigated via three dimensional computational fluid dynamics (CFD) procedures in a DI diesel engine using high EGR rates. The results show that when increasing EGR from low levels to levels corresponding to reduced temperature combustion, soot emission after first increasing is decreased beyond 40% EGR and reaches its lowest value at 58% EGR rate. Advanced injection timing before 20.5 ºCA BTDC together with applying 58% EGR leads to simultaneous reduction in NOx and soot formation compared with the base engines. The predicted values of combustion process, emissions by this CFD model at high EGR levels show a good agreement with the corresponding data in the literature.