Performance Research And Design Of Automobile Exhaust Muffler

The automobile exhaust noise is one of the main sources of vehicle noise, it can do harm to human health, the environment, the development of economy, and so on. The most effective way to control exhaust noise is to install an exhaust muffler, which will be a hindrance to sound and allow airflow to get through. However, this device can also increase the exhaust resistance, thus affecting the economy and power of the car. Therefore, it has been a major project of noise control engineer to explore the method of designing the muffler with high noise elimination ability and low exhaust resistance.The automobile exhaust noise is made up of the basic muffler units(expansion, resonance and dissipative muffler), for this reason, first of all, this paper uses the numerical analysis methods to summarize the influence rules of expansion radio, hole diameter, flow resistivity, external environment and other factors on acoustics and flow field performance of the muffler units and its combination based on the results of previous studies. Besides, some correction and supplement will be done. All of these results will provide a theoretical basis for the design of enterprise scheme.Secondly, the engine and exhaust muffler performance testing platform was built base on relevant standard. It is used to test engine power, intake and exhaust pressure and other parameters of the muffler which is provided by the enterprise(Hereinafter referred to as enterprise scheme) and equivalent straight pipe on thirteen kinds of steady-state conditions. According to the results, there is no enough noise reduction on low-frequency and strong internal turbulence of the muffler. Besides, the spectral characteristic of exhaust noise is analyzed to provide data support for the acoustic design of exhaust muffler.In the software GT-Power, a coupling model of engine and exhaust system was established according to the structure parameter provided by enterprise. Compared the caculation results with the experimental results, and it shows that almost all the errors were below 5%, which verified the effectiveness of the coupling model. This model will be used on the subsequent design with the purpose to analyze if the designed muffler(Hereinafter referred to as design scheme) match with the engine.Finally, this paper presents the positive design process of muffler. It goes from the design goal to overall program and then to the specific design. It gives priority to acoustic performance, flow field performance and others will be put on the next. The main muffler will also be given priority, and the deputy muffler will supplement it. From the perspective of the exhaust noise spectrum, by a reasonable choice, complication and combinations of basic muffler units, a muffler will be finished gradually. And then the muffler will be improved according the flow field contours. After finishing the design, a compare between the designed muffler and the muffler provided by the enterprise shows that the designed muffler is feasible, but also shows that the positive design method in this paper is reasonable, and it may have some reference value in the design of automotive exhaust muffler.