发动机排气歧管结构的优化设计

摘要

Crack failure is one of typical failure modes in exhaust manifold of the engine.In order to find the failure cause and improve the structure of exhaust manifold,the paper researched on structure optimization design of engine exhaust manifold.In the paper,it constructed the analytical model of thermal stress of engine exhaust manifold,researched on failure mechanism of manifold cracking under the condition of cold and thermal impact,based on reduction of thermal stress,residual stress and plastic strain for the focused position of manifold,and proposed the optimal design solution of exhaust manifold structure.The analysis of simulation experiments demonstrated that under the condition of cold and thermal load impact,for each index located at the key areas of"V" shape on manifold,all the thermal stress,residual stress and plastic strain are higher than designed limitation value,and it is the main cause resulted in manifold cracking failure.By means of the technical measure such as reinforced "V"shape and making subdivision of connection position and so on,it can improve the status of stress concentration,and the experience results validate that the solution of exhaust manifold optimization design is reasonable and effective.%开裂失效是发动机排气歧管典型的失效模式之一.为了找出失效原因并改进发动机排气歧管结构,研究了发动机排气歧管结构的优化设计.构建了发动机排气歧管热应力分析模型,研究了歧管在冷热冲击条件下开裂的失效机理,基于降低歧管关注位置的热应力和残余应力与塑性应变,提出了排气歧管结构的优化设计方案.仿真实验分析显示,在歧管“V”形位置处的各项指标在冷热冲击载荷作用下,其热应力、残余应力和塑性应变均高于设计极限值,是导致歧管开裂失效的主要原因.借助在“V”形位置加筋及外表面连接位置剖分等技术措施,可改善应力集中状况.实验结果验证了该排气歧管优化设计方案的合理性与有效性.