Research On The Vibration And Acoustics Performances Of The Tailpipe Of A SUV

With the rapid development of the automotive industry,people pay more attention to the ride comfort performance of the car.The tail pipe noise of the car exhaust system is related to the interior noise,which directly affects the comfort performance of the car.The acoustic performance study of the exhaust system muffler can quickly and effectively reduce the exhaust pipe noise of the exhaust system and improve the comfort performance of the car.One end of the exhaust system is connected to the engine exhaust manifold,and the other end is connected to the frame through a hook,which transmits engine vibration to the vehicle body,and its vibration characteristics also affect the ride comfort of the car.Therefore,the exhaust system should be designed with both acoustic and vibration properties.In this paper,by using the muffling unit with different muffling characteristics,the transmission loss of the original muffler in certain frequency bands is increased,and the muffling effect of the muffler is improved;A multi-objective robust optimization model with the Z-direction dynamic reaction force extreme value and standard deviation of the hook,the Z-direction static deformation of the lifting lug and its static preload force standard deviation as the optimization target is established.The vibration performance optimization results show that the Z-direction dynamic reaction force extreme value and standard deviation of the hook,and the standard deviation of the static preload force of the lifting ear are significantly reduced.In the real vehicle test,the overall and order noise of the idle speed and the third-speed full throttle(3WOT)acceleration tailpipe noise are greatly reduced compared with the original scheme.Firstly,the GT-Power model and the finite element model of the original exhaust system were established,and the accuracy of the model was verified based on the engine bench test and the modal test analysis of the exhaust system.Secondly,the acoustic performance,aerodynamic performance and transmission loss of the muffler of the original scheme exhaust system were analyzed by GT-Power.Combined with the Fluent flow field analysis of the muffler,an improved scheme of the muffler structure is proposed.The influence of the cross-flow pipe perforation parameters on the transmission loss of the muffler is studied,and the specific structure of the muffler of the improved scheme is determined.The GT-Power simulation analysis was carried out on the improved scheme of the exhaust system,and the real vehicle test was designed to verify the the acoustic performance of the improved scheme.Finally,static and dynamic vibration performance analysis of the acoustically improved exhaust system is performed.The results show that the dynamic reaction force of the lifting system is large,and the static preload force and the dynamic reaction force extreme value distribution are uneven,which will affect the ride comfort performance and the durability of the lifting lugs.In order to improve the vibration performance of the exhaust system,the lifting stiffness of the lifting lugs and the bellows are taken as the design variables,and an optimization model based on minimizing the static displacement,the standard deviation of the static preload force,and the extreme value and the standard deviation of the dynamic reaction force of the lifting lugs is proposed.At the same time,the constraints such as the vibration isolation of the lifting lugs are considered.The multidisciplinary optimization design software Isight is integrated with Nastran to optimize the vibration performance of the exhaust system.