Design And Optimization Of The Car Muffler

As of December 2010, the vehicle holdings in China reached 199 million, including more than 8500 million automobiles. China has become the world's second-largest vehicle holdings country. With the growth in vehicle holdings, an increasingly prominent issue of vehicle noise comes. Vehicle noise causes great harm on people's work and life.Governments, automobile manufacturers all pay attention on the issue. Exhaust noise is a main component of automobile noise, account for about 36%. Generally, it was higher than the vehicle noise at 10-20dB (A). Reduce the exhaust noise can significantly reduce vehicle noise. In this paper, numerical analysis and the test are combined to finish an automobile exhaust muffler design. As provides new methods and ideas for the muffler optimization this paper has important engineering significance.According to the actual engine parameters, engine model was build based on GT-Power, from which the engine exhaust spectrum was got. The exhaust spectrum show that muffler was required to focus on 300-800Hz, the sound deadening capacity must be above 20dB (A) at most frequencies. The preliminary muffler schemes were designed and coupled with the engine model to simulate the acoustic and aerodynamic performance. Then the testing was carried out. The simulation and testing results show the same trend:At 2100r/min arise a resonance peak, at high speed high the tail noise zoomed.According to test results, optimization was implemented for the tail noise. The optimization reduces the peak noise at 2100r/min and the tail noise at high engine speed effectively. The optimization scheme of muffler had a sound deadening capacity of above 25dB (A), as well as back pressure achieved 13kPa. The tail noise, order noise, back pressure all can meet the targets.Study on radiated noise of muffler which had single and double layers based on LMS-Sysnoise.Results showed that the radiatied noise of single layer muffler had significantly increased. The resonance occurred in a number of speeds. Dual layer muffler can decrease the stiffness, so it can inhibit resonance at a number of speeds. Increase joints between the shell and baffle had no significant effect on radiated noise.Designed the tailpipe reasonably can effectively reduce tail noise. Tail pipe length, diameter, shape of exports have an impact on the tail noise. But to the limit of the chassis, only the shape of tail pipe exports can be changed. Through the three different tailpipe export shape comparison by simulation and testing method, using fishtail pipe can reduce the tail pipe noise 3-4dB (A).