喷油策略对直喷汽油机混合气形成影响的模拟计算

Simulation Research on Effect of Injection Strategy on Formation of Mixture of Gasoline Direct Injection Engine

利用三维仿真软件FIRE建立直喷发动机的仿真计算模型。经过喷雾可视化试验标定,对直喷发动机的单次喷射和二次喷射进行仿真计算,得出二次喷射策略的燃油碰壁量比单次喷射降低25%,有利于混合气的形成和燃烧。进一步研究推迟二次喷射时间对混合气形成的影响发现,一定程度上推迟喷油时间后,燃油的碰壁量会有所下降,同时也会导致最终油膜量的提高,反而导致混合结果不佳。此外,若喷油过迟,碰壁量不仅不会减少,还会增加。

A simulation computation model for GDI engine was built up by using 3Dsimulation software FIRE and calibrated by spray visualization test.The model was used to calculate single injection and two stage injection in GDI engine.Results show that the fuel quantity impinging to wall of two stage injection is 25%,less than single injection.This is beneficial to fuel/air mixture formation and its combustion.It is found that injection timing delay of two stage injection in certain range can reduce fuel quantity impinging to wall,but finally causing addition of fuel film quantity adhering on wall and resulting in poor mixture formation.If injection timing too late,the fuel quantity impinging to wall would increase,instead of reduction.