Computational And Experimental Study Of A New Type Diesel Engine Exhaust Muffler For A Vehicle

The exhaust noise of engine is one of the main noise sources of automobile noise. At present, muffler in exhaust system is the most effective device to control exhaust noise. Aerodynamics performance is one of the evaluating indicators for muffler. The exhaust muffler is a noise reduction device, which prevents the spread of noise and allows airflow through it, it not only reduces the exhaust noise but also increases exhaust pressure drop, affects the power and oil-consume performance of engine. In serious case even affects the normal operation of the engine. So designing a muffler with high acoustic attenuation performance and low resistance loss has been an important subject on exhaust noise control. The computational and experimental study of muffler is very important.Base on the acoustic theory and muffler design method, an existent muffler was selected for new-model heavy truck. In order to enhancing anechoic performance and aerodynamics performance of the muffler, its internal structure was modified. The analysis of the flow field inside the new type muffler was made with the help of FLUENT. The pressure drop and insertion loss of both mufflers were studied in the engine bench test. The main research of the article included the following works:(1) The article summarized the design principles of muffler and exhaust system, a suitable muffler was selected using the design method and empirical equation. The anechoic mechanism of the perforated tube muffler was analyzed. According to the practical experience, the structure of existent muffler was modified.(2) The numerical simulation of the flow field inside modified muffler was made with the FLUENT, and the article analyzed velocity field and pressure field. The flow characteristics inside the new type muffler, the local pressure drop and the regenerated noise for perforated tubes were studied.(3) The pressure drop and insertion loss of both mufflers were analyzed in the engine bench test. The accuracy of the numerical simulation was verified by the experimental data. The contrastive analysis of anechoic performance between the currently existing muffler and the new type muffler was made by using the computational method of weighted insertion loss.