Numerical Simulation of Thermal Stress for a Liquid-Cooled Exhaust Manifold

Liquid-cooled exhaust manifolds are widely used in turbocharged diesel engines. The large temperature gradient in the overall manifold will cause remarkable thermal stress. The objective of the project is to modify the current design for preventing the high thermal stress and extending the life span of the manifold. To achieve the objective, the combination between Computational Fluid Dynamics (CFD) with Finite Element (FE) is introduced. Firstly, CFD analysis is conducted to obtain temperature distribution, providing boundary conditions of the thermal load on the FE mesh. Afterward, FE analysis is carried out to determine the thermal stress. The interpolation of the temperature data from CFD to FE is done by Binary Space Partitioning (BSP) tree algorithm. To accurately quantify the thermal stress, nonlinear material behavior is considered. The computational results are compared with that of Number of Transfer Units (NTU) method, and are further verified with industrial experiment data. All these comparisons indicate that present investigation reasonably predicts the thermal stress behavior. Based on the results, recommendations are given to optimize the manifold design.