Theoretical Study On The Noise Reduction Of An Automobile's Exhaust System

As people's living standards improve, people make higher demands on the quality of life. The noise is not only an important factor that affects a car's comfort ,but also an important indicators of a automobile's performance. In the development and design of a car, if the noise can be reduced, the comfort and the competitiveness of products can be improved. In this paper, the noise reduction of a automotive exhaust system are studied.First, the noise hazard and the development of the exhaust system at home and abroad are discussed. The principle and function of muffler, which is the main component in exhaust system are elaborated and the classification and evaluation indices of muffler are introduced. The acoustic basis and foundation of computational fluid dynamics are also introduced, which lay a good foundation for the following study of acoustic characteristics.The model of exhaust system which matches engine SOFIM8140.43C made by Nanjing Iveco Automobile Co. Ltd. Branch are established in CATIA, including catalytic converters, corrugated pipe, connecting pipe, pre-and post-muffler muffler.Next, Hypermesh is employed to get the air grid model in pre-muffler and rear muffler, then the grid model is imported into SYSNOISE where the acoustic characteristic will be analysed. The original exhaust system are analyzed, and the results show that the pre-muffler and rear muffler noise reduction feature is not satisfactory.According to the results, several improvements are proposed and transmission loss analysis are carried out. After comparative analysis, the final optimization solutions are determined, which can distinctly improve the effect of the original muffler noise reduction.The numerical simulation in this paper can accumulate some improved experiences and improved methods. What's more,a effective method for the characteristic's prediction of the engine's exhaust system is developed in this paper.