基于流固耦合的某增压汽油机排气歧管热分析

Thermal Analysis for the Exhaust Manifold of a Supercharged Gasoline Engine Based on Fluid-solid Coupling

鉴于某增压汽油机排气歧管在热冲击试验中的开裂问题,采用流固耦合热分析方法,用计算流体力学和有限元软件计算了排气歧管的温度场和热应力分布,计算结果与试验数据吻合较好,并证实了排气歧管的开裂系热应力过高所致。据此,对排气歧管结构进行了若干方案的改进,最终采用四二合一的构型,经试验测试不再发生开裂现象。说明流固耦合热分析是解决排气歧管开裂问题的有效途径。

In view of the problem of cracks, which appear on the exhaust manifold of a specific gasoline engine in thermal-shock test, the temperature field and thermal stress distribution of manifold are calculated by using CFD and FEA software with fluid-solid coupling thermal analysis technique. The results of calculation well agree with test data and conclude that the cracks on exhaust manifold are caused by high thermal stress. Accordingly the structure of manifold is modified with several schemes and finally a scheme with four-to-two-to-one configuration is adopted. The manifold with that configuration has obviously lower thermal stress and cracks no longer happen again, indicating fluid-solid coupling thermal analysis being an effective way for solving the crack problem of exhaust manifold.