缸内直接喷射式汽油机点火稳定性的数值分析

缸内直接喷射式汽油机的一个显著特点是依靠火花塞点燃喷入缸内的汽油油束。由于缸内混合气浓度极不均匀，所以其点火及火焰传播过程与普通均质燃烧式发动机有很大的不同。火焰核心的稳定形成及初始火焰发展对缸内的整个燃烧过程有极其重要的影响。本文利用二维两相混合模型模拟喷雾过程，利用一个详细的准维模型模拟火花塞的点火过程，并采用特殊处理方法使两个子模型相匹配，计算了缸内直接喷射式汽油机从喷雾到形成稳定火核的全过程，分析了多种因素对点火稳定性的影响，尤其是对涡流比、点火时刻和喷油定时之间的适当配合进行了模拟分析。计算结果对优化实验有明显的指导作用。

Numerical Analysis on the Ignition Stability in Direct Injection Gasoline Engines

The combustion process of direct injection(DI) gasoline engines relies on the spark ignition of the fuel spray injected into the cylinder.The flame kernel initiation and flame propagation process are very different from those of the traditional homogeneous charge gasoline engines because the mixture concentration is rather inhomogeneous in DI gasoline engines.The stable formation of flame kernel and initial flame development have very important effects on the whole combustion process in the cylinder.In this paper,the atomization and ignition process in a DI gasoline engine are computed by a detailed theoretical model,including a two dimensional two phase spray model and a quasi dimensional thermodynamics ignition model.Effects of some parameters on the ignition stability are analysed from the calculation.Optimization of swirl ratio,spark timing and injection timing are carried out through the numerical analysis.These computing results are very useful to the experiment.