增压发动机排气歧管开裂问题分析与解决措施

Analysis and Solution to Crack Problem about Exhaust Manifold of the Pressure-charging Engine

某四缸增压直喷发动机在整机台架试验过程中出现排气歧管开裂问题。为解决此问题,首先,现场确认失效排气歧管的开裂程度及位置。其次,进行失效分析,对失效样件进行断口分析、断口周边元素检测,初步确认排气歧管开裂原因。再次,通过计算机仿真分析对排气歧管开裂真因进一步确定,并制定整改对策。最后,样件整改并策划试验进行验证。结果表明:排气歧管开裂位置为热应力分布最大的区域,长期冷热冲击致使排气歧管在此位置表现为开裂失效。因此,通过排气歧管结构优化,降低开裂位置的热应力,并通过发动机可靠性试验验证确认整改方案有效,此问题最终得以解决。

During the engine test bench experiment, a certain four cylinder turbocharged ignition gasoline engine occured the phenomenon of the exhaust manifold cracking. To solve this problem, firstly, we had confirmed the position and the extent. Secondly, we carried through an analysis on the fracture location and an element test near the fracture, so that we could preliminary make sure the original cause of the crack. Thirdly, laying down countermeasures after the CAE simulation on this exhaust manifold. Finally, carrying on the test on the modified component to confirm the effect. The result shows that the failure position is among the re,on of max thermal stress, long time temperature cycle cause this failure problem. So we optimized the structure of the exhaust manifold to lower the thermal stress, in this way we solved this problem and which was proved to be effective through the engine＇s reliability tests.