Influence Of Injection Strategies On Combustion And Emission Of The Turbocharged GDI Engine

Because of the increasingly stringent emission regulation and the massive consumption of fossil fuel,the gasoline direct injection engine has been getting attention recently in the field of passenger cars because of its great effects in decreasing fuel consumption and reducing emissions.And it is becoming the primary direction of the future.Compared with port fuel injection engine,gasoline direct injection engine has shorter time that mixes fuel and air.Therefore,optimization of injection strategy can form better fuel and air mixture which benefits to the ignition and flame propagation.It has great importance for gasoline direct injection engine in optimizing dynamic performance,economical efficiency and decreasing emissions.In this paper,the injection strategies were conducted on the turbocharged direct injection gasoline engine under constant speed and load.The injection timing and injection pressure under single injection,two-stagnation injection with its second fuel mass repartition and second injection termination timing were comprehensively investigated to analyze the influences of injection strategies to combustion,performances and emissions.The results indicated that 300°CA bTDC was the optimized injection timing for the injection timing experiments under single injection mode.The brake thermal efficiency?BTE?reached up to the highest 35.17%and the brake specific fuel consumption?BSFC?reduced 8.79%.The 50%combustion location shifted to the top dead center and the combustion duration shorten with the retarding of the injection timing.The NOx,THC and CO emissions had the trend of being decreased first and then increased.The emissions were the lowest level when the injection timing was300°CA bTDC.Furthermore,12 MPa was the optimized injection pressure for the injection pressure experiments under single injection mode.The BTE reached up to the highest 34.35%.With the decreasing of the first fuel mass repartition,the 50%combustion location far away from the top dead center and the combustion duration was longer,the BTE decreased while the(1and the BSFC increased under two-stagnation injection model.CO emissions were gradually increased,NOx and THC emissions were decreased.But when the fuel mass repartition was decreased to 40%,THC emissions were significantly increased.For the second injection termination timing experiment,the results indicated that the 50%combustion location far away from the top dead center,the combustion duration was longer,the BTE decreased and the BSFC increased with the retard of second injection termination timing.The NOx emissions were gradually decreased while CO and THC emissions were increased.By the way,the later the second injection termination timing was,the higher the THC emissions were.