考虑配气机构冲击的气缸盖结构动力学仿真分析

Study on Dynamic Simulation of Cylinder Head Considering Valve-train Impact

配气机构的冲击作用会对柴油机气缸盖的应力场分布产生较大的影响。首先建立了某柴油机配气机构的多体动力学仿真模型,获得气门底座对于气缸盖的气门座圈的循环冲击载荷。在此基础上,综合考虑热应力及循环机械应力和冲击压力作用,对含气缸盖、机体、冷却水套等的组合结构模型进行瞬态动力学响应分析,对比分析了配气机构循环冲击对气缸盖的结构强度的影响大小。结果表明:相比于恒定等效的配气底座冲击作用力的加载,采用瞬态动力学并考虑变化配气机构底座冲击作用影响下得到的气缸盖应力场分布,气缸盖进排气门座圈处的应力值明显增加,应力值增幅可达到10%左右;火力面处的应力值也会增加,局部应力增幅可以达到30 MPa;同时,气缸盖的整体应力场也出现了不同程度的增加。

The impact of valve-train could have a great effect on the stress distribution of cylinder head. Firstly, In order to get the cycle impact load of the cylinder head valve seat resulting from the valve-train, the multi-body dynamics simulation model for a diesel engine valve train was established. After that, it is necessary to analyze the alteration of the stress distribution of cylinder head due to the impact load of valve-train. Based on this results, considering the influence of thermal stresses and cyclic mechanical stress and impact pressure, the combination structure model which containing the cylinder head, the body, cooling water jacket and other related component was established to simulate the transient dynamic response. Finally, it is also required to compare the difference between the two multi-body dynamics simulation models. The results show that the stress distribution of cylinder head which considering the variable impact pressure of the valve-train display a more reliable conclusion. Besides, the stress of cylinder head intake and exhaust valve seat were at significantly augmented and its value can increase by 10%. In addition, stress at the fire deck surface also got augmented and its value can increase to 30 MPa. Meanwhile, the overall stress field of the cylinder head has been varying degrees of increase.