乙醇DI对汽油PI发动机性能与爆震的影响

Effect of ethanol DI on performance and knocking of gasoline PI engine

文章在一台汽油缸内直喷发动机的基础上,建立了发动机的三维计算模型,标定了原机的喷雾模型和燃烧模型,并在此基础上进行了乙醇缸内直喷(ethanol direct injection,EDI)+汽油进气道喷射(gasoline port injection,GPI)的仿真模拟,研究EDI喷油时刻、点火时刻、进气温度对发动机缸内混合气的形成、燃烧、排放的影响和乙醇燃料特性对爆震抑制的贡献率。仿真模拟结果表明:通过改变EDI喷油时刻,影响乙醇的蒸发雾化程度,在缸内形成不同程度的混合气当量比分布;喷油时刻在上止点前250°CA时,缸内混合气均匀,产生最佳的燃烧相位。在最大爆震极限火花提前时,通过进气加热抵消乙醇汽化潜热的影响,得出乙醇高汽化潜热和高火焰传播速度对OH自由基的抑制率分别为23.5%、76.5%。

In this paper,the effect of ethanol direct injection(EDI)injection time,ignition time and inlet temperature on the formation and combustion of in-cylinder mixture and the contribution rate of ethanol fuel characteristics to knock suppression were studied on a gasoline engine equipped with an EDI plus gasoline port injection(EDI+GPI)system.A three-dimensional model of EDI+GPI engine was established,and the experimental conditions were simulated numerically.In the simulation calculation,the spray model and combustion model were calibrated respectively.The experimental results and simulation showed that by changing the EDI injection time,the extent of evaporation and atomization of ethanol was affected,and the mixture equivalent ratio distribution was formed in the cylinder.The competitive EDI injection time was 250°CA BTDC,better combustion phase was generated because of homogeneous mixture in cylinder.The influence of latent heat of ethanol vaporization was offset by intake heating which inhibited OH radical formation at 23.5%by high latent heat of ethanol vaporization and OH radical formation at 76.5%by high flame propagation velocity.