CFD-FE耦合计算分析某汽油机排气歧管热负荷

Couple CFD-FE-Analysis for a Gasoline Engine Exhaust Manifold of Thermal Load

为了在开发设计过程中预测排气歧管的热负荷,采用了计算流体力学-有限元(CFD-FE)耦合计算分析方法。首先用计算流体力学(CFD)软件计算了排气歧管的瞬态内流场和稳态外流场,得到了排气歧管内外壁面的热边界条件。再以此为边界条件,使用有限元软件计算了排气歧管的温度场,并以此温度场为边界条件,计算了其热应力和热变形。结果表明,在只有热负荷作用时,排气歧管外壁面存在着较大拉应力,最大值为80.4MPa;最大热变形出现在和排气后处理器相连的法兰盘前端突台上,其值为1.08 mm。

A combined computational fluid dynamics(CFD) and finite element method(FE) analysis approach has been developed to estimate the thermal load of a gasoline engine exhaust manifold in the early stages of design.To simulate the heat transfer coefficients of the exhaust manifold wall under actual operating conditions,the external and internal flow fields are predicted using the STAR-CD fluid-heats analysis code.The predicted heat transfer coefficients are used in finite element analysis to predict the temperature field.Then,it is employed to predict thermal stress and deformation.The result reveals a large tensile stress field in the outer wall of exhaust manifold,the maximum thermal stress is 80.4 MPa;the maximum thermal deformation occurs in the front of flange connecting three-way catalyst,which is 1.08 mm.