变形对小型Wankel转子发动机端面漏气的影响研究

以计算得到理想状态下的缸内压力、温度、传热系数为初始边界条件,用有限元方法计算发动机温度场,用试验测得的温度场校核计算的准确性,然后将温度场结果作为已知条件计算变形,得到漏气面积并计算端面漏气初值。用漏气后转子发动机状态更新计算边界条件,进行循环计算,最终得到端面漏气量。之后,用此方法研究了转速对端面漏气量的影响,得出如下结论:发生变形后,转子与端盖之间的漏气面积在曲轴转角约630°时达到最大值,最大漏气面积随转速的增加呈拟线性下降趋势;漏气率在上止点附近达到最大值,在上止点附近端面漏气量约占端面总漏气量的50%。漏气率随发动机转速的增加逐渐减小,最大漏气率所对应的曲轴转角随转速的增加而减小。

Study on Influence of Deformation on the End Face Leakage of a Small Wankel Rotary Engine

A temperature field model of a small Wankel rotary engine was established by the finite element method with cylinder pressure, temperature and heat transfer coefficient under the ideal condition as initial boundary conditions. The result of the temperature field calculation was checked by experiment. The initial value of gas leak and the leakage area were acquired from the deformation calculation performed based on the checked temperature field result. Then the boundary conditions were then updated by considering leakage, and the final leakage at end faces was obtained by cyclic simulation with the new boundary conditions. Finally, the influence of the engine speed on the end faces leakage was studied with the method above. The results show that the leakage area reaches the maximum value when the crank angle is about 630°, and the maximum leakage area decreases in quasi linear with the increase of the engine speed. The leakage rate reaches the maximum at near top dead center, where the leakage is about 50% of the total. Furthermore, the leakage rate decreases with the increase of the engine speed, while the crank angle corresponding to the maximum leakage rate decreases as the engine speed increases.