汽油机活塞二阶运动分析及优化设计

Analysis and optimization design on piston secondary motion of gasoline engine

为了降低活塞二阶运动并寻求优化措施,综合考虑裙部润滑摩擦状况、活塞体径向刚度、活塞体及缸套热态型面影响,建立某汽油机活塞组件动力学模型,采用数值仿真方法进行分析研究.从换向平稳性、运动平稳性、活塞敲击能和摩擦损耗4个方面对活塞二阶运动计算结果进行评价.分析在多种工况下(1 200、4 200、6 000r/min)活塞裙部型线、配缸间隙和活塞销偏置对活塞二阶运动的影响,以敲击能和摩擦损耗为主要评价标准,提出相应的优化思路.结果表明:优化后的裙部型线使活塞的径向位移和角位移有一定幅度减小,径向位移最大值在3种工况下分别降低了22.2%、19.8%、21.2%,角位移最大值降低了12.9%、13.3%、23.6%;活塞对缸套的动态敲击力在优化后也有明显降低,为活塞整体优化提供可靠依据.

In order to reduce piston secondary motion and provide the improved solution, the dynamic model of a gasoline engine piston set was established based on skirt lubrication and friction, piston radial stiffness and warm profile of piston and liner, and analyzed by numerical simulation method. The calculation result of piston secondary motion was evaluated from four aspects as switching stationarity, motion stability, piston kinetic energy and friction loss. The effects of piston skirt profile, radial clearance and pin offset on piston secondary motion were evaluated under different working conditions （1 200, 4 200, 6 000 r/min）. Optimization methods were put forward mainly based on the piston kinetic energy and friction loss. The result shows that the optimized skirt profile decreases the piston radial displacement and titling angle. Under the three working conditions, the maximum of the radial displacement and titling angle decreases by 22.2% ,19.8% ,21.2% and 12.9%.13.3% .23.6% respectively. Dynamic excitation to the liner decreases obviously through optimization, which provides a reliable reference to the entire optimization of piston.