变压缩比活塞结构设计与仿真

Design and Simulation of Variable Compression Ratio Piston Structure

为了改善大排量柴油发动机的冷起动性能,提高发动机中小负荷的动力性,避免发动机大载荷发生爆震,设计了一种变压缩比活塞。该变压缩比活塞由内体、外体两部分组成,外体直径为180 mm,内体与外体之间通过梯形槽产生相对的螺旋运动,在改变发动机压缩比的同时可以实现清除积炭的目的。通过对变压缩比活塞的内部结构设计,实现了液压控制的发动机压缩比随着发动机工况变化的自动调节。通过建立活塞外体的ANSYS有限元模型,分析了在最大压缩比情况下活塞外体的应力及应变分布规律。结果表明:在压缩比为21、材料弹性模量为0.7 MPa、泊松比为0.3、外体的瞬时温度为588 K、最大爆发压力为13.5 MPa情况下,变压缩比活塞外体的应力及应变分布与最大压缩比时外体相对于活塞销的转动位置有关,同时与距活塞顶面和裙部的位置有关。

In order to improve the cold-start performance of large displacement diesel engine, improve the ce of medium-small iable compression ratio piston dynamic load engine, and avoid the occurrence of detonation of big load engine, a kind of varis designed. The variable compression ratio piston is composed of an inner body and an exterior body. The diameter of the exterior body is and the exterior body which is generated through the changing 180mm. There is spiral movement between the inner body trapezoidal groove. Deposition carbon can be removed by the engine compression ratio. Through internal structure design of the variable compression ratio piston, the compression ratio of hydraulic control engine can achieve automatic adjustment with the changing of engine working condition. We established the ANSYS finite element model of the exterior piston body, and analyzed the distribution rule of stress and strain of the exterior piston body under the circumstance of maximum compression ratio. The result shows that when the compression ratio is 21, the material elastic modulus is 0. 7MPa, the Poisson ratio is 0. 3, the instantaneous temperature of the working fluid is 588 K, and the maximum explosive power is 13.5 MPa, stress and strain distribution of the exterior body of variable compression ratio piston is related to the ro- tation location of exterior body relative to the piston pin when the compression ratio is at its maximum; it is also related to the distance between the exterior body and the piston top surface and the distance between the exterior body and the skirt section.