Optimization Design Of Engine Exhaust Manifold Based On Finite Element Analysis

If the structure of exhaust manifold is unreasonable, the vibration of engine will cause the exhaust manifold breaking easily when the vehicle in experiment or run normally. The breaking of exhaust manifold will lead to the air leakage phenomenon appearing on the vehicle. The air leakage will not only cause the engine power dropping, but also cause the vehicle spontaneous combustion possibly. Therefore, the structural strength rationality of the exhaust manifold which is as one of engine important periphery parts influences the engine performance and the vehicle security directly. So that the optimization design of exhaust manifold is very important.In this paper, in view of the exhaust manifold breaking phenomenon which appeared during pedestal experiment of a certain model engine, the dynamic characteristic of the exhaust manifold is analyzed and studied with the FEM based on the engineering vibration theory. The primary reason of the breaking phenomenon has been discovered. The reason is that the first two steps of the exhaust manifold's natural frequency fell into the frequency range which is corresponded with the normal work rotational speed of the engine, then the harmonic excitation which is produced during the engine normal work caused the exhaust manifold resonating. Based on these, a technical program is proposed .The technical program aimed at raising the natural frequency of the exhaust manifold. It is an optimization design which is carried on by the modification of both material and its structure. After the optimization, the analysis and the practical application indicate that the optimization plan has solved the exhaust manifold breaking problem which is caused by engine excitation effectively.