Study On Flow Field Optimization And Airflow Regeneration Noise Of Split-stream-rushing Muffler

The exhaust noise is dominant in the whole machine noise of internal combustion engine,even much greater than the sum of the other noise sources,therefore,to control the exhaust noise is of great significance.Pressure loss is an important factor in evaluating the muffler's aerodynamic performance.In this thesis,the airflow field was analyzed using the Fluent software for the split-stream-rushing muffler which was formerly developed by our research group.the results show:clapboard and hedge areas are the places where the pressure loss is greater,and some suggestions were put forward to improve the structure of the muffler.A comparison was conducted between the pressure loss of original and improved mufflers,showing that the pressure loss of the improved muffler is greatly reduced.Tests on pressure loss of the original and improved mufflers were carried out on a self-made muffler test bench under different inlet airflow speeds,and the results from the test and the simulation were compared,showing a good consistency and the pressure loss of muffler increases with the increase of inlet velocity.The flow field distribution in muffler and the airflow regeneration noise is closely related.By using broadband noise models and FW-H acoustic analogy method,the regeneration noise of the muffler was studied,proved that the sound pressure level at each measuring point of the improved muffler is lower than that of the original muffler,and the sound pressure level increases with increase of the inlet airflow velocity,also the outlet noise of the muffler has a certain directivity.