基于热机耦合的机体主轴承壁性能数值模拟与实验研究

Numerical and experimental research on performance of main bearing wall based on coupled thermal and mechanical load analysis

针对一款2.7 L高增压柴油机,采用有限元方法计算了机体的结构强度,分析了热载荷与机械载荷对机体主轴承壁区域的应变分布影响。设计了发动机台架实验,测取机体主轴承壁面的温度与动态应变,对计算结果进行验证并分析了产生误差的原因。研究结果表明:机体主轴承壁的工作应力由热应力与动载应力两部分组成,在额定工况下,热应力占主导地位。通过对比模拟与实验结果可以发现,基于第3类热载荷边界条件计算得到的壁面温度精度较高,但是该方法精度强烈依赖输入的换热系数精度。基于有限元方法获得的应变模拟值表现出良好的跟随性。有限元方法对最大动载荷模拟精度较高。最大工作应变计算误差主要来自于最大热应力的计算误差。计算模型的拓扑网格结构、测点当地材料属性与换热条件是造成计算误差的3个主要因素。

The structure performance of the block of a 2.7 L highly boosted diesel engine was investigated based on finite element analysis（FEA）,and effects of the thermal and mechanical load on the strain distribution of the main bearing wall were analyzed.The bench test was performed to measure the temperature and the dynamic strain of the main bearing wall in order to certificate the FEA results,and the factors were found out,which may cause the error in the simulation.The results show that the working stress of the main bearing consists of thermal stress and the dynamic loading stress,and the thermal stress is dominant at the rated load condition.Compared with the experimental results,the simulated temperature based on the 3 rd boundary is highly accurate.However its accuracy depends on the accuracy of the heat transfer coefficient.The simulated values of strain based on the FEA show good following.The FEA has high precision for the simulation of maximum dynamic load.The calculation error of maximum working strain mainly comes from the calculation error of the maximum thermal stress.The error mainly results from three factors,i.e.the topological grid structure,the local material property,and the local condition of heat transfer.