中文摘要：

发动机工作时活塞裙部的变形会直接影响与缸套的配合间隙和润滑状态。文中以某通用航空二冲程活塞发动机为研究对象，建立活塞-活塞销-连杆-气缸套组合体有限元模型，计算并分析了不同负荷作用下活塞裙部的变形，并通过建立二阶运动动力学模型分析了活塞的横向位移，对活塞裙部与气缸套间的润滑油膜厚度和油膜压力进行了模拟计算。结果表明：不同负荷作用下活塞裙部主推力面有不同的变形；热负荷使裙部膨胀变形；机械负荷作用下裙部上端膨胀、下端收缩；热-机负荷耦合作用时的裙部变形复杂，不是两者的简单叠加；发动机工作时裙部两端与气缸套壁面间形成楔形空间，活塞裙部与气缸套之间能够建立油膜润滑。

英文摘要：

The deformation of piston skirt directly affects the assembly clearance with cylinder liner and the lubrica-tion state during the engine operation.In this paper,by taking a general aviation two-stroke piston engine as the re-search object,a finite element model describing the piston-piston pin-connecting rod-cylinder liner assembly is con-structed,the deformation of piston skirt under different loads is calculated and discussed,and a second-order dy-namic model is set up to analyze the lateral displacement of the piston.Moreover,the thickness and pressure of the lubricant film between the piston skirt and the cylinder liner are simulated.The results show that （1 ）the main thrust plane of the skirt is of a deformation varying with the load;（2）thermal load may result in a skirt expansion and mechanical load may cause an expansion of the skirt upper end as well as a contraction of the lower end of the skirt;（3）under coupled thermal-mechanical load,the deformation of the skirt is not the sum of the deformations respectively under thermal and mechanical loads but varies complicatedly;and （4）during the operation of the en-gine,a wedge-shaped space may occur between the ends of the piston skirt and the wall of the cylinder liner,which makes the appearance of film lubrication between the piston skirt and the cylinder liner possible.