某柴油机进排气门热-机耦合应力场分析

Analysis of Thermal-Mechanical Coupling Stress Distribution on Inlet and Outlet Valve of Diesel Engine

为详细分析某柴油机进排气门在热-机械负荷作用下的耦合应力情况,应用GT-power软件计算分析了某柴油机在标定工况下燃烧室、进排气道内气体的瞬时平均温度和瞬时平均换热系数。以此为边界条件,对进排气门开启和落座的瞬态温度场进行迭代,得到进角排气门的稳态温度场,并利用试验对气门温度场进行了验证。以计算得到的温度场为基站,对进排气门的热应力进行了计算分析,随后施加缸内燃气压力最大时的机械负荷得到热-机搞合应力场。计算结果显示,排气门的温度变化较为剧烈、热应力较大,应力集中的部位主要出现在气门导杆与气门座之间过渡的区域。为气门疲劳失效分析、结构优化改进以及设计制造等提供了参考。

In order to analyze the rules of stress field in inlet and outlet valve subjected to thermal load and mechanical load in diesel engine,use GT-power software to compute and analyze the instantaneous average temperature and heat transfer coefficient in combustion cylinder,inlet pipe and outlet pipe of diesel engine in rated conditions.According to the result as the boundary condition,iterate through the transient temperature field in the period of the valve crashing and opening to compute the rules of the steady temperature field.Based on temperature field of diesel engine,compute and analyze the thermal stress.Then apply mechanical load when the cylinder pressure is maximal,compute the coupled stress.The result shows that the temperature fluctuation in the outlet valve is intense and the thermal load of the outlet valve is larger,and stress concentrates on the transition region between the valve guide and valve seat,and provides references for valve's stress,fatigue invalidation analysis and improvement of structure.