Optimal Design Of The Vehicle Muffler And Noise Reduction

The exhaust noise of Auto automotive engine is one of the main noise sources of auto motive noise. Installing muffler on the exhaust system is the most efficient method to control the exhaust noise. The main issue in the scopes of the exhaust noise control is that how to design a muffler which can reduce much noise value and has low pressure loss. Traditional design is based on the theory of one-dimensional plane wave, but it can not accurately simulate the effect of three-dimensional wave and other practical factors. As a three-dimensional numerical method, the FEM can simulate accurately the muffler's property. It is a high efficient method to design and improve the muffler. The paper uses the acoustic module of ANSYS to calculate the muffler's acoustic property, as well as use ANSYS/FLOTRAN to analyze aero-dynamic characteristics.The paper has some preliminary study about t characteristics of noise elimination of the typical mufflers, especially the impedance compound muffler. On this basis, the paper designs an exhaust muffler which used on a truck, and applies the software above on simulating the acoustic and aerodynamic characteristics. According to the results, the paper improves the defect and calculates again. It will not be over until the results meet the standard. Finally, do a test on the muffler product. Through the repeated simulations, two conclusions can be gotten. One is that the structure of muffler design has been matured, the muffler designed by design manual can get a good noise characteristic in the low and mid frequency, and the muffler has a better noise characteristic in high frequency by the new sound-absorbing materials. The other is that improving the inside structure can reduce the pressure loss value and keep air flow is stationary. For example, dig the holes on the clapboard can effectively inhibit the formation of turbulence, and so on. At last, the testing results show that the product has a higher muffler volume and lower pressure loss than the previous.The numerical simulation of exhaust muffler in this thesis can provide reference and new method for muffler design. It is of important instructional significance for improving the design and analysis of muffler.