汽油机歧管式催化转化器流固耦合热应力分析

Fluid-structure thermal simulation of gasoline engine manifold catalytic converter

采用流固耦合的方法计算了某汽油机歧管式催化转化器结构热应力状态与振动特性。首先,计算了歧管式催化转化器结构的内流场和外流场,得到了内外壁面的温度与压力分布;进一步利用有限元的方法计算了歧管式催化转化器结构的热应力状态和振动特性。计算结果表明,歧管式催化转化器结构在入口法兰区域热应力过大,容易产生应力集中,是最容易损坏的区域;另外,排气歧管和催化转化器连接处,与螺栓固定点的距离较大,热变形较大。据此,进行了结构改进,并与原结构进行了相应的分析对比,结果表明改进后的歧管式催化转化器较原结构在最高温度及最大热应力、振动特性等方面均有所改善。

The thermal stress and vibration characteristic of original structure of gasoline engine manifold catalytic converter are calculated with the fluid-structure thermal simulation. The heat transfer boundary conditions,such as the temperature of fluid boundaries and stress distribution, are calculated. Then, the thermal stress and vibration characteristic of original structure of manifold catalytic converter are calculated with Finite Element Analysis technology. According to the results, the thermal stress is excessive in entrance flange area. It is easy to produce the thermal stress concentration and is damaged easily in this area. In addition, the thermal deformation is large in the junction area between exhaust manifold and catalytic converter. Finally,the improved structure is presented according to the calculation results. The corresponding analysis and comparison show that the improved structure is better than the original structure in the highest temperature,the maximum thermal stresses and the vibration characteristic.