Vibration Analysis And Control Of An Automotive Exhaust System

Exhaust system is the main part of the vehicle. Under the engine moment excitation, exhaust system will transfer the vibration to the car body as a vibration transmission path, and deteriorate the NVH performance of the vehicle. If the exhaust system modal frequencies couple with the engine excitation frequencies, the vibration will be amplified by the exhaust system, and the vibration of the car body will reach a high level.This paper makes a study on the problem of exhaust system idle vibration. Firstly, the finite element method is used to creat the exhaust system model. Secondly, the model is validated by comparing the modal parameters acquired by finite element modal analysis and experimental modal analysis respectively. Finally, the simulation and experiment reveals that the exhaust system modal frequencies couple with the engine idle second-order and fourth-order vibration frequencies, which amplifies the vehicle vibration.In order to adjust the natural frequency of the exhaust system, firstly, orthogonal design has been used for the thickness parameters of the exhaust system components and the isolators’ dynamic stiffness parameters based on the validated finite element mode. Secondly, Pearson product-moment correlation coefficient and the main effect plot have been calculated to obtain the relation between the thickness parameters of the exhaust system components, the isolators’ dynamic stiffness parameters and exhaust system modal frequencies. At last, an experiment has been carried out according to the result calculated above by replacing the specific isolators. It is seen that this improvement measure can reduce the vibration at idle speed greatly.