Investigation of Simultaneous Effects of Pilot Fuel Quantity and Pilot Injection Timing on Emission Formation and Engine Performance in a High Speed Direct Injection (HSDI) Diesel Engine

In this research, the simultaneous effects of pilot fuel quantity and pilot injection timing on engine performance and pollutant formation have been studied in a High Speed Direct Injection (HSDI) diesel engine. For this purpose, an improved version of the ECFM-3Z combustion model has been applied. In the first step, the simulated results has been compared with the experimental data and good agreement has been achieved for simulating the in-cylinder pressure, the heat release rate and the amount of pollutant emissions. In the next step, nine different strategies in terms of two main variable parameters (the dwell between pilot injection and main injection as well as the amount of injected fuel in each phase) have been investigated. The results show the amount of pilot injection and its timing have an important effect on the amount of pollutant emissions and the amount of brake specific fuel consumption. These results show by 0.5 mg pilot fuel injection and also the retarding the injection timing by 10 crank angle degree, the amount of NOx and soot emissions have been considerably decreased compared to the baseline case. However, increasing the amount of the brake specific fuel consumption (for about 2.5 %) and decreasing the indicated mean effective pressure (for about 2.2 %) should be considered as two negative factors.