Numerical investigation of the effect of two-stage injection strategy on combustion and emission characteristics of a diesel engine☆

Abstract This work assessed two types of two-stage injection strategies for the operation of a diesel engine: pilot and early injection. The effects of the two-stage injection interval and the first-stage fuel injection proportion on the combustion and emission characteristics when employing these two injection strategies were investigated by numerical modeling, dividing the in-cylinder zone into three different regions. Variations in the NOx, soot, HC and CO emissions in each region were determined at various values of two-stage injection interval and first-stage fuel injection proportion for both strategies. The results demonstrate that, considering both the engine combustion and emission characteristics, a two-stage injection strategy in conjunction with an injection interval of 30–40°CA and a first-stage fuel injection proportion of 30–60% is advisable.