Study On The Acoustic Performance Of Flow Field In Muffler

Automobile transportation has been a necessary part of modern life. Along with enhancing of our living-level and continuously increasing of automobile possession amount, traffic noise has been a more serious problem than ever. Exhaust noise is one of the main sources of the vehicle noise, so the muffler study and design get the recognition once more. Studying application computer simulation and emulation on muffler design could improve its reduction effects. Through combined emulation design with experiments, we could get advantages of the both methods. This would change the tradition of only stressing on the external results but difficult to perform internal research. and makes us enable to design mufflers on the hypostasis, reduce design cost and save development periods. Muffler cannot be researched and designed without considering of sound wave transmission medium. Automobile exhaust noise transmits in the gas medium field; it is impossible to analyses the internal acoustic field and flow field thoroughly by experiments. Emulation software could simulate the actual condition of the internal acoustic field and flow field without disturbing them and the results could be taken as design reference. Actual noise elimination and gas dynamical characteristic of mufflers are the most important targetes of muffler designing. In fact, the dynamic noise elimination of mufflers is always lower than static noise elimination and it will produce regeneration noise when airflow speed is beyond a certain one. In this paper, we consulted the China nation standard Acoustic Muffler Meterage Method GB/T4760-1995 and built an experiment bench. According to the pipeline experimentation, we measured the noise elimination characteristics of the midst part and the last part ofJetta mufflers and a Changling CM125-2B muffler. The content included the effect of airflow on the noise elimination, regeneration noise and pressure lost. From the test data, we got the conclusion that the effect of airflow was very small on the noise elimination within a certain speed and that beyond the limit, noise elimination evidently reduced and pressure lost increased at the same time. According to the experiment data, we simulated the flow field in the muffler with the integration fluid emulation software FLUENT. This software uses the numerical solution of finite volume method and could build models with non-structure meshes. It could be universally used and is utilized in a...