Effects of Fuel Injection Timing on the performance of a Direct-Injection Spark-Ignition Engine

Abstract:

Through the numerical simulation on cylinder flow, mixture formation and combustion process of a turbo-charged gasoline direct injection engine, meanwhile, with the help of break specific fuel consumption, emission and combustion data from engine test, the effect of start of injection timing on engine performance was studied. The results show, for 5000r/min condition, the case whose injection is started at 400ºCA obtains the optimal mixture formation. Because of the more uniform mixture distribution, higher turbulence kinetic energy around spark plug at spark time, shortest 10-90% burning duration and lower HC emission, it has the best fuel economy and combustion stability. While the best start of injection timing is retarded 30ºCA at 2000r/min. When injection is advanced, wall film increases, the decreased equivalence ratio and lower turbulence kinetic energy around spark lead to lower burning rate, so HC emissions, fuel economy and combustion stability may go bad. The same situation occurs in delayed injection, the mixture uniformity goes worsens at spark time because of insufficient mix, consequently engine performance is deteriorated.