Mechanism And Suppression Method Of Automobile Exhaust Muffler Shell Noise Radiation

Vehicle NVH performance not only affects the feelings of drivers and riders,but also directly affects the market competitiveness of its,At the same time,it has a great contribution to the noise level of modern urban environment.Exhaust system is a large part of the noise of fuel-fired vehicles,Noise reduction of exhaust system by controlling exhaust pipe exit noise can no longer meet the increasingly stringent requirements of market and environment for NVH performance of vehicles,The radiation noise of muffler shell usually be ignored in the past impacts even greater than exhaust pipe exit noise in some models.Therefore,it is of great significance to study the mechanism and suppression method of muffler shell.radiation noise.This study comes from the real vehicle NVH performance development project,In the later period of development,the noise at rear seat of a vehicle exceeds the target,and it is proved that the noise radiation noise of the muffler shell is the cause.Then a simulation model is established to optimize the design,and the robust design of related parameters based on tolerance model is carried out.The specific research works are as follows:(1)For the vehicle's problem of excessive noise at rear seat under the idle condition,using modern vibration and noise testing and analysis equipment,combined with subjective evaluation method,spectrum analysis method and elimination method,the sound source under idle condition is investigated,and It is found that the radiation noise of muffler shell contributes greatly to the sound pressure level of the car interior noise at rear seat.(2)Structural modal analysis and vibration-noise transfer function test are carried out for single muffler.Structural Finite element model and acoustic boundary element model are established.Structural modal and vibration-noise transfer function of the muffler are calculated.it is verified that the simulation model has high credibility,By comparing the simulation results with the experimental results,it shows that the research works based on this simulation model has much practical.Engineering significance.(3)Based on the experimental and simulation results,the mechanism of the radiated noise of the muffler is elxplaind,and the influencing factors are judged.Nine parameters of the exhaust system that can be adjusted at the present period of the car model are given,and the local sensitivity of each factor is calculated by using the shell radiation noise simulation model.Seven of the most influential parameters are further picked,and several numerical points near the current value for the simulation are calculated,the variation curves of the shell radiation noise changing with each factor is obtained,and the influence rule of each parameter on the radiated noise are briefly analyzed.(4)Seven parameters with high local sensitivity are selected to carry out orthogonal optimization simulation.The prototype production and vehicle matching verification are completed after obtaining the optimized parameters.The results show that the optimization scheme is feasible.Then,robust design of the optimized parameters is carried out,which improves the qualified rate of the muffler sample for shell radiation noise.The innovation of the study:(1)By means of test and CAE,the structure mode and vibration sound transfer function of muffler are analyzed,and the formation mechanism of radiation noise of muffler shell is elxplaind,that is,the shell vibrates violently to form noise radiation when the structure mode of muffler is excited.(2)Robust design is applied to the suppression of muffler shell radiation.By the reasonable design of the value range of the muffler structure parameters and material parameters,the optimization plan to reduce the noise of the muffler shell is obtained.