Numerical Calculation Of Muffler Flow Regeneration Noise Based On CFD

As the development of high speed engine, exhaust airflow regeneration noise has become the main reason affecting the attenuation performance. Therefore, the research on regenerative noise has theoretical and practical significance.In this paper, do numerical calculation by fluent and Virtual.Lab Acoustics to get the sound pressure level information. Firstly, through the CFD numerical simulation,analyze the velocity and turbulent kinetic energy inside the muffler, which provide help for recognition of flow regeneration noise mechanism, and validate the feasibility of numerical simulation on flow regeneration noise. Secondly, the numerical simulation method is discussed, analyze several influence factors to the calculation.Thirdly, study the influence of structure parameters of each muffler unit and airflow velocity on regenerative noise, find the influence law. Finally, the influence law was used to improve a vehicle muffler.The research results show that: the airflow regeneration noise of perforated pipe muffler unit is slightly decreased with the increase of the airflow velocity, and the rest type increases with the increase of airflow velocity. In the case of the same shape and size, the regeneration noise of the perforated pipe muffler unit is minimized. In a certain range, increase the expansion ratio, the length of the expansion chamber and the inner diameter of the inlet pipe, use circular-section expansion chamber,set the inlet and outlet pipe in same axis, use the bevel and rounded transition structure in cross-section mutation position of the import and export tube can reduce regeneration noise. Increase insert length of the inlet and outlet pipe, the perforation aperture,decrease the perforated wall thickness, increase the distance from perforation plate to the entrance pipe section mutation and the number of the perforated pipe unit may increase the airflow regeneration noise. Regenerative noise of the improved muffler decreased significantly, the pressure loss and transmission loss are improved, too.This article mainly does tentative exploration which aims at researching theinfluence factors of flow regeneration noise, and compare the results with the results which were derived in the published paper using other methods, the conclusions agree well. It is further showed that using numerical simulation method can be effective and thorough on the muffler research and design. What’s more, the cost is low, the efficiency is much higher than the experimental method, and has better accuracy.