Engine Exhaust System Structure Strength Simulation Analysis Which Based On Fluid Solid Coupling

As the strengthening degree of internal combustion engine continues to increase,the thermal load and mechanical load also increase.The exhaust system is subject to the impact of high exhaust temperature,bolt preload and high frequency vibration from the engine,whether the design is reasonable directly influences the stability of the whole engine structure,durability of engine and reliability of engine.Unreasonable design will lead to lower intake efficiency,cracks in the exhaust pipe,deformation,bolt loosening,exhaust leakage and other problems.Therefore,it is of great practical significance to improve the performance and reliability of the engine by analyzing the thermal mechanical load of the exhaust systems and optimizing the structure of the intake and exhaust systems.In this paper,we study the intake system and exhaust system of a diesel engine.We carried out the one-dimensional and three-dimensional coupled calculation of the engine,cylinder combustion calculation and the exhaust flow calculation through the CFD method,and the accurate fluid temperature and heat transfer coefficient of the exhaust pipe wall have been obtained.Finite element simulation analysis of engine exhaust system start with the exhaust system temperature field which obtained by fluid solid coupling calculation,and combined with the mechanical loads such as vibration and bolt pretension to do thermo mechanical coupling calculation.And we use it's result to analysis the thermal mechanical working stress,the exhaust pipe deformation,the exhaust system vibration mode,the sealing performance of exhaust pipe and turbocharger gasket.The results show that the design of exhaust pipe structure is reasonable,The distribution of homogenizing treatment heat transfer coefficient has the tendency that it present high at both ends and low among them,The temperature distribution presents the characteristics that it is high in branch and low in other position.In terms of air intake uniformity,new air intake system is better designed.The exhaust pipe stress concentrated in the exhaust pipe bolt hole and the exhaust pipe flange connection area,flange deformation of exhaust pipe is big and the exhaust system has the risk of resonance.Exhaust pipe gasket contact pressure is enough,however the exhaust pipe flange deformation is so large that the exhaust pipe is in risk of flange deformation leakage;Turbocharger gaskets contact pressure is not enough to prevent from exhaust shock leakage.