In the overall optimization scheme, in order to improve the exhaust efficiency of the exhaust manifold, ensure that the exhaust of the manifold is uniform and the flow is good, it needs to be considered as a whole. At the same time, it should be ensured that the new exhaust manifold will not have adverse effects on the conversion efficiency of the three-way catalytic converter.

Therefore, in order to ensure the rationality and scientificity of the improved design, the CFD analysis of the exhaust manifold is carried out first. With the help of the relevant analysis software, the overall analysis of the new exhaust manifold is carried out. The mesh type is mixed hexahedron / tetrahedron. In the process of meshing, the total number of grids is about one million in the range of 1.5-2.5mm for a single cell. After the completion of the mesh generation, the divided mesh is imported into the ANSYS FLUENT software to load the boundary conditions.

In addition, the ideal inert gas is used to set the medium type in the pipeline, and the standard k – ε turbulence model is used to calculate it. Finally, the flow velocity uniformity of the three-way catalyst can be obtained when the branch pipe exhausts alone.