Experimental investigation the impacts of injection strategies coupled with gasoline/ethanol blend on combustion, performance and emissions characteristics of a GDI spark-ignition engine

The injection timing under single injection strategy and double injection strategy consisting of an optimal timing for the first injection and a later timing for the second injection were investigated on a turbocharged GDI engine fuelled with gasoline and ethanol blend under stoichiometric air/fuel ratio. The combustion phasing, performance and emissions characteristics were comprehensively analyzed. The results indicated that the peak combustion pressure, maximum heat release rate and maximum in-cylinder temperature first increased and then decreased with sweeping the injection timing from 340 degrees CA bTDC to 280 degrees CA bTDC, reaching a peak value at 300 degrees CA bTDC. While the peak combustion pressure, maximum heat release rate and the maximum in-cylinder temperature gradually decreased with decreasing the percentage of first fuel injection distribution. In addition, the 50% combustion location was gradually stayed away from the top dead center, the combustion duration was prolonged, and the gasoline equivalent brake thermal efficiency decreased with decreasing the percentage of the first fuel distribution. Moreover, the injection timing under single injection strategy had no apparent impact on the COVIMEP. However, the fuel distribution under double injection strategy remarkably affected the COVIMEP. Lastly, the concentration of the HC increased with decreasing the percentage of the first fuel injection distribution. While the NOx emissions decreased with decreasing the percentage of the first fuel injection distribution.