Diesel Engine Exhaust Manifold Failure Analysis And Optimization

Exhaust manifold is an import part of diesel engine exhaust system, it is the critical channel for exhaust gas. It is quite hard working condition for exhaust manifold, on one hand, it is under the thermal shock from high temperature exhaust gas in cylinder, on the other hand, it is vibration fatigue during engine working process. It is continuously impact to exhaust manifold in diesel cylinder, if the exhaust gas could not be released smoothly from the exhaust manifold, then certain area would be at high temperature, which results in thermal fatigue, oxidation peeling, deformation, corrosion and cracking. In condition of failure of exhaust manifold, exhaust gas could not be released quite quickly, then inlet fresh air can not be taken in, so the exhaust gas in combustion would reduce combustion efficiency during whole cycle. So the exhaust manifold failure would affect engine a lot at driving power, cost saving and exhaust gas, then the focus on study of the exhaust manifold would be very meaning and practical.This article will focus on the typical non-turbo and turbo exhaust manifold, especially at its structure and feature, such as special requirement of material, normal difference between China and foreign material, meanwhile the developing tend. Manufacturing process and key characteristic from raw casting to machining. Then the design feature, study of vibration, internal flow field and thermal stress. Finally, based on the actual example, to set up simulation model, to analysis with professional CFD fluid dynamics analysis software of STAR-CD, also finite element software ABAQUS, which is to calculate surface temperature of exhaust manifold, thermal transfer rate, temperature port at different positions, thermal stress and thermal fatigue safety rate at failure field to find out tension point, to optimize structure of exhaust manifold; at the same time, make mode analysis of exhaust manifold and booster, check and eliminate risk of vibration, to avoid failure of exhaust manifold.The study shows that root cause of failure of exhaust manifold is thermal fatigue stress, to avoid the failure stress point and induce thermal fatigue lift of exhaust manifold, which should be improvement actions that proposed. This article also offer the total method of analysis, through simulation analysis to calculate temperature field, thermal stress and thermal fatigue safety rate,assess thermal fatigue risk; meanwhile apply the mode analysis on exhaust manifold and booster, assess vibration risk.