小型强化内燃机波致疲劳模拟与结构优化

Wave Induced Fatigue Simulation and Structural Optimum of Downsized Engine

基于RoverK16内燃机模型,建立了热机耦合仿真模型,并得到了文献的验证。仿真结果表明,最大应力出现在活塞顶部上表面中心处,并随着顶部厚度增大而降低。对活塞进行了爆震工况下的寿命预测,当活塞顶部厚度由7.6mm提高至12.6mm时,普通爆震工况下疲劳寿命对应的行驶里程由2.42万公里增加到21.13万公里。将顶部结构改为平顶或凸顶时,活塞寿命大幅提升且薄弱区域变为泄油孔处。通过优化活塞销孔参数降低了泄油孔处的应力集中情况,改善了疲劳寿命。最后,对凸顶无泄油孔灰铸铁活塞在超级爆震工况下的疲劳寿命进行了仿真,得到内燃机可连续运行22.68万公里,达到了规定的22万公里里程。

Based on Rover K16 internal combustion engine model,a thermal-mechanical coupling simulation model was established and verified by literatures.The simulation results show that the maximum stress appears at the center of the top surface of the piston and decreases as the top thickness increases.The fatigue life of the piston under knocking condition was predicted.When the top thickness of the piston increased from 7.6mm to 12.6mm,the driving mileage under normal knocking condition increased from 24,200km to 213,300km.When the top structure is changed to flat top or convex top,the piston life is greatly improved and the weak area becomes the oil drain hole.By optimizing the parameters of piston pin hole,the stress concentration at the oil drain hole is reduced and the fatigue life is improved.Finally,the fatigue life of the gray cast iron piston with convex top without drain hole under super knocking condition was simulated,and it was obtained that the internal combustion engine could run continuously for 226,800km,reaching the prescribed mileage of 220,000km.