中文摘要：

按照直喷式汽油机的要求对ROTAX914汽油机的部分结构和参数进行了改造和调整，并使用AVLFIRE软件对改造后缸内混合气的形成过程进行了模拟研究。研究发现，喷射角度、喷油定时、初始滚流比浓区中心位置、浓区中心的形成、浓区中心的形状及位置有较明显的影响；通过喷射参数的调整及缸内气流的组织，在燃烧室中形成了满足直喷式发动机要求的分层混合气。

英文摘要：

Fuel economy can be improved by gasoline direct injection, and the formation of stratified mixture is the basic and key of this improving. In this paper, the structure and parameters of the ROTAX 914 engine was reformatted and modified to satisfy the requirements of gasoline direct injection engine. The process of the formation of stratified mixture and its influencing factors were studied using the AVL FIRE software. It＇ s found that injection angle, injection timing and initial tumble ratio separately had an obvious effect on the location, the formation, the shape and location of center of dense mixture. Stratified mixture of high quality came into being in the combustion chamber through modifying spray parameters and the flow in the cylinder.