Simulation Study On Combusiton Optimization And High Load Extention Of Gasoline PPCI Engine

Under the pressure of severe energy supply and environment protection, the development of efficient and clean combustion mode has become one of the most important solutions to the strict regulations for emissions.In recent years, the compressed ignition internal combustion engine could run with varius fuels such as diesel, gasoline and natural gas as fuel with the help of specific control of inlet charge, EGR, fuel injection.The PPCI engine fueled with gasoline, which has long delay period and its ignition happens after finish of fuel injection, can achieve higher thermal efficiency and has lower emission of Soot compared to diesel engine. The enormous potentiality of PPCI engine has been proved.In this study, the experiments of PPCI engine fueled with gasoline have been conducted on a test bench of ZH1130 diesel engine. The CFD model of the engine combustion chamber with air inlet is built, and the modle parameters which is calibrated with experiment data is established by engine numerical simulation commercial software,CONVERGE. Calculations are conducted to study the process of intake charge, compressed and combustion of gasoline PPCI engine. The effects of fuel injection advance angle, injection pressure, fuel injection angle on the combustion of gasoline PPCI engine has also been calculated and discussed. The results show that the fuel will be burned completely with at least 15oBTDC fuel injection advance angle, 20 MPa injection pressure, and a higher thermal efficiency could be achieved at 140ofuel injection angle. Two types of fuel injection strategy have been studied in this paper, which is pilot injection+ main injection and main injection+post injection. Pilot injection can improve the combusion efficiency, post injection can reduce the rate of pressure rise while the emissons of HC, CO and Soot will be increased a few.The load of PPCI engine has been expanded by boost and EGR in the medium speed with the restrict of the emission of NOx and the rate of pressure rise. The operation range could be expanded to IMEP=0.8MPa with the boost. With intake pressure 0.18 MPa, 20%EGR, the range could been expanded to 0.88 MPa, but the fuel economy is decreased. All those calculation results could provide guidance for conducting experiments on test bench.