3D Acoustic Performance Simulation And Optimal Design Of Complex Muffler

With the development of technology and the progress of time, people understand more and more about noise, and are also increasingly concerned about its danger. With the rapid development of China's automobile industry, the increasing of vehicle population, vehicle noise has become a major source of urban noise. Motor vehicle exhaust noise is one of the main noise source. Utilization of the exhaust muffler is the most effective way to control the exhaust noise. In this thesis, acoustic performance and optimal design of the muffler has been studied by using three-dimensional acoustic simulation.Firstly, this thesis described the current research status about muffler and introduced the basis theory of muffler design.Secondly, the theory of three-dimensional numerical simulation of acoustic was introduced. Then the three-dimensional acoustic simulation of muffler was done by using the software Sysnoise, and the transmission loss of the muffler was calculated. According to comparing about the results of the relevant experimental and simulation, the three-dimensional acoustic simulation of the muffler was verifiedThirdly, the influence of some structures of expansion chamber muffler and two-chamber muffler was analyzed by 3D acoustic simulation. The results show that the bigger expansion ratio, the better the acoustic performance of mufflers. Intubation structure can improve the acoustic performance of mufflers and widen the frequency range of mufflers, but its length must be designed according to the exhaust spectrum. Through the numerical simulation about the different cross-section layout of muffler, it was found that according to the exhaust spectrum, the muffler can be further optimized by changing the cross-section layout without changing the basic structure. Changing volume ratio of the two-chamber muffler can improve the effective noise reduction frequency range of the muffler.Fourthly, the acoustics performance relationship between complex mufflers and simple mufflers were analyzed. It was discoveried that the acoustic performance of complex muffler is the superposition of acoustic performance characteristics about its relative simple mufflers in most frequency range. According to the above results, four schemes of three-chamber mufflers have been designed and optimized through the analysis of the acoustic simulation. The third scheme is the best for this engine spectrum.Finally, by using relevant software, this thesis simulated the insertion loss and pressure loss of the optimized muffler. The results of the insertion loss and the transmission loss were coincided. The results of pressure loss meet the design requirements. It were explained that the results of the previous optimal design is reasonable.