基于折射率匹配法GDI发动机附壁油膜特性

Under the trend of engine lightweight and high injection pressure, gasoline direct injection( GDI)engines with multi-hole injectors are prone to spray collapse and impingement, resulting in fuel film on the piston. In order to study the impingement characteristics under different fuel temperatures, a refractive index matching method was used to investigate the macroscopic morphology of spray impingement and analyze the fuel film thickness distribution and the evaporation process. The results show that, at low fuel temperature without flash boiling, the fuel wall films impinged from each spray plume are separated each other and the film thickness is large with a slow evaporation rate. When the fuel temperature increases to reach the flashing point, the spray collapse begins to occur and the film thickness becomes thin and uniform with a fast evaporation speed. When the fuel temperature continues to rise, violent spray collapse can be seen under high fuel temperature, and the impingement footprint turns into an approximately spherical shape with a slow evaporation rate.