为了开发适用于增程式电动汽车用分层稀薄燃烧二冲程LPG直喷发动机，首先，建立描述高压LPG喷嘴内外流动过程的多相流数学模型，并按照相似准则制作放大的旋流喷嘴透明模型，由可视化（光学纹影法、激光片光散射法）实验和计算机数值模拟揭示在气穴流动和减压沸腾双重作用下LPG喷束的分裂、蒸发和碰壁过程。在此基础上，为了解决二冲程直喷汽油机转速高、在关闭排气口后的压缩过程中后期燃料喷射时，存在着混合气形成不充分的问题，利用车用LPG沸点低、易蒸发汽化的特点，本申请提出了不同扫气方式的喷雾引导燃烧系统和设计一个进气门及纵向进气道、利用进气滚流形成分层混合气的壁面引导燃烧系统。它采用旋流喷嘴或非旋流2孔喷嘴，由激光诱导荧光法和数值模拟探明不同喷嘴位置、喷射条件（喷射时期、喷雾形态、喷射压力）、活塞凹坑形状、缸内气流运动等对混合气分层构造的影响，并将这些优化结果用于二冲程LPG直喷发动机的开发。

In order to exploit a two-stroke LPG DI engine adopting stratified lean combustion used for extended range electric vehicles. Firstly, the mathematical model used to described internal flow and spray for a LPG high pressure injector is established and a transparent scaled-up nozzle is made. The break-up,evaporation and wall interaction processes of LPG spray under the effect of the cavitating flow and flash boiling are revealed using visualization experiments and CFD simulations. Because of the high speed of gasoline direct injection two-stroke engine, the mixture preparation is insufficient when the fuel is injected during the middle or late stage of the compression stroke after exhaust port closes. Spray-guided combustion systems with different scavenging methods are presented. And a wall-guided combustion system with one inlet valve and vertical intake port are designed, which can obtain stratified mixture by using intake tumble. The swirl injector or two-hole injector is used. The effect of injector positions, injection conditions (injection timing, spray pattern, injection pressure), shapes of the piston bowl and the in-cylinder gas motion on stratified mixture formation are investigated using CFD simulations. And these optimization results are used on the development of the LPG direct injection two-stroke engine.