Structural Design Research On The Exhaust System For Vibration Problem

Exhaust system is an indispensable part of engine power assembly,on the one hand,the exhaust system is subjected to the engine vibration excitation and the road roughness,making the exhaust system vibrate;on the other hand,The vibration of the exhaust system is also transferred to the frame through the suspension support element,effecting of vehicle comfort,Therefore,it is necessary to analyze the vibration of the exhaust system.This thesis was based on the practical problems encountered in the process of independent research and development.Firstly,this thesis analyzed the present situation of the research and development of engine design and exhaust system structure,according to the general requirements of the enterprise,clarified the purpose and significance,put forward the research target and content.After analyzed the structure and working environment of the exhaust system,combined with the task of the project team,formulated the general planning of structural design of engine exhaust system for vibration problem.Secondly,this thesis introduced the basic theory of vibration,Including the theory of multi rigid body dynamics,the basic theory of continum vibration,the source of engine vibration excitation and the theory of structural optimization design.Thirdly,according to the overall research plan,this thesis established parametric model of engine vibration based on Virtual Prototyping Technology,presented a new simplified method of cylinder pressure,and adjusted and verified the vibration model of the engine by vibration test,the results showed that the vibration model of the engine was highly corresponing to with the actual situation.Fourthly,this thesis carried out modal analysis,frequency response analysis and transient response analysis by finite element method.The results indicated that the vibration characteristics of the exhaust system were bad,and the dynamic stress in the cracking failure occurs position was large.Lastly,this thesis used the shape optimization method to optimize the connection area of the vent connection,vent support and muffler from the perspective of improving the dynamic characteristics of structures.The results turned out that the natural frequency of the optimized structure increased,the frequency range of the excitation was avoided effectively,the dynamic stress of the response was decreased obviously,the optimized structure had a certain light weight effect.In conclude,this thesis not only solved the practical problems encountered in the design and development of the enterprise,and also put forward a more feasible method of vibration simulation of engine,exhaust system structure analysis and optimization design.In order to solve this problem,a set of complete design flow was proposed,which provided the flow scheme and data reference for the future design and development of the product.