气缸盖中两相流沸腾换热热机耦合仿真分析

Cylinder Head Thermo-Mechanical Coupling Simulation on Two-Phase Flow Boiling Heat Transfer System

基于汽液两相流沸腾换热的基本理论和计算方法,对某柴油机气缸盖与冷却水腔组成的流固耦合传热系统进行了整场求解,得到了气缸盖的温度场分布,并通过与气缸盖温度场试验结果对比分析,证明了计算模型的有效性。将温度场结果施加于气缸盖、螺栓、机体所组成的热机耦合系统中,对气缸盖进行了结构强度计算,得到了气缸盖火力面热机耦合应力分布。采用试验设计方法,将冷却水进口温度和速度作为输入参数,对火力面应力较大区域的最大等效应力进行了响应分析,结果表明:考虑汽液两相流的沸腾换热可以有效降低气缸盖火力面的最大热机耦合应力;火力面的最大应力出现在喷油器座孔周围;冷却水进口温度对火力面应力较大区域的最大等效应力的影响不可忽略。

From the theory and calculation methods of vapor-liquid two-phase flow boiling heat transfer,the fluid-solid coupling heat transfer system comprising a cylinder head and a cooling water jacket for a diesel engine was solved.The distribution of the cylinder head temperature was obtained and validated by the experimental data.The cylinder head temperature field simulation result was added to the thermo-mechanical coupling system which consists of the cylinder head,bolts and cylinder block,and the distribution of the cylinder head thermo-mechanical coupling stress field was achieved.Using the experiment design method,the cylinder head flame-face maximum equivalent stress of some large stress areas were analyzed with the cooling water inlet temperature and velocity as input parameters.The results show that considering the vapor-liquid two-phase flow boiling heat transfer can effectively reduce the maximum thermo-mechanical coupling stress of the cylinder head flame-face.The maximum thermo-mechanical coupling stress appears around the injector hole.In addition,the effects of cooling water inlet temperature on the cylinder head flame-face maximum equivalent stress of some large stress areas cannot be ignored.