增压直喷汽油机排气歧管低周疲劳的研究

Low Cycle Fatigue Study of Turbocharged Direct Injection Engine Exhaust Manifold

为了探索某增压直喷汽油机排气歧管在交变载荷作用下的低周疲劳,首先利用AVL-Fire软件对排气歧管进行内外流场CFD分析,得到排气歧管的热边界条件;然后把热边界条件映射到有限元网格,通过有限元分析计算出排气歧管瞬变循环工况下的温度场、应力场和应变场。最后利用疲劳分析软件计算出排气歧管的疲劳寿命。结果表明,排气歧管疲劳寿命预测合理反映了在交变载荷和高温的共同作用下排气歧管低周疲劳损伤区域的寿命,验证了该预测方法的有效性和准确性。

In order to investigate the low cycle fatigue of the exhaust manifold in a turbocharged direct injection gasoline engine under alternate loading,a CFD analysis is carried out on the inner and outer flow field of exhaust manifold with software AVL-Fire first,with its thermal boundary conditions acquired. Then the thermal boundary conditions are mapped into the FE mesh,and the temperature,stress and strain fields of exhaust manifold under transient cycle conditions are calculated by a finite element analysis. Finally the fatigue life of exhaust manifold is calculated using fatigue analysis software. The results demonstrate that the fatigue life prediction of exhaust manifold reasonably reflects the life span of low-cycle fatigue damage areas in exhaust manifold under the coactions of alternate loading and high temperature,verifying the effectiveness and correctness of the prediction method adopted.