液态LPG中心喷射发动机混合气形成的研究

Research on mixture formation of LPG for a center injection DISI engine

当液态LPG以5MPa高压直接喷入气缸时,将发生剧烈地闪急沸腾现象,这对于改善壁面引导式燃烧系统的缸内直喷发动机的燃料附壁现象、降低HC排放具有非常积极的作用。在验证了采用的计算方法可行性的基础上,就提出的中心喷射的壁面引导式燃烧室结构,数值解析了电控LPG缸内直喷发动机在不同负荷工况时混合气的形成过程。结果表明:部分负荷时采用压缩过程中后期喷射,15°BTDC时缸内可形成理想的分层构造;大负荷时采用进气中期130°ATDC喷射,在压缩冲程末期可形成均质功率混合气。

While liquid phase LPG＇s（liquefied petroleum gas） is directly injected into cylinder by a high pressure（5 MPa）,the occurrence of flash boiling is being proposed to play an important role in reducing wall wetting of the cylinder and HC emissions at a wall guided DISI（direct injection spark ignition） engine.With the validation of the feasibility on models,this paper numerically simulates the mixture formation in different conditions for a center injection wall guided DISI engine model.The results show that LPG spray forms an ideal stratified mixture at 15°BTDC with a post-compression process in part load conditions,and that it forms a homogeneous power mixture at a high load when injected at 130°ATDC.