The Heat Load Of A Gasoline Engine Exhaust Manifold

The exhaust manifold, which is one of the most important part of the engine’s exhaust system, is the linking hub of the engine and follow-up exhaust system. Due to the exhaust gas of high temperature, the exhaust manifold, which is directly linked to the cylinder head, subjects to serious thermal shock. The exhaust manifold of complex structure and uneven temperature distribution, suffers coupled action of alternating temperature and alternating stress, which easily lead to the initiation and propagation of hot cracks. Besides that, many exhaust manifolds are made from thin-walled tube in lightweight vehicle. Therefore, the thermal load analysis is an important guidance for the exhaust manifold design.Firstly, according to the engine parameters and the layout of the exhaust system, the3D model of a gasoline engine exhaust is modeled through Catia, which is a kind of3D modeling software. Secondly, the joint analysis methods of CFD and FEM are put forward to predict the temperature distribution, thermal stress and thermal deformation of the exhaust manifold under the rated conditions. Finally, the cycle of engine working and stopping is simulated to indicated the equivalent plastic strain, which is considered as a criterion for evaluate the reliability of the exhaust manifold.The analysis results show that the temperature distribution of the exhaust manifold is closed related to the complexity and heat-dissipating condition. And the thermal stress is mainly concentrated in the structural transition region of weak stiffness. The equivalent plastic strain mainly occurs in the first several cycles, and then the exhaust manifold gets into a relatively stable state, which has a small contribution of the equivalent plastic strain.The simulation data are fairly right by comparing the measured data with simulation results, which is helpful for the exhaust manifold design.