| In this thesis, by building the acoustics field and flow field of the 244S motorcar exhaust muffler with FEM, the muffler is improved. The main content is as follows:Firstly, based on one-dimension-plane wave theory, the transmission matrix of the basic muffler elements are deducted, and a sofeware for forecasting the performence of motorcar exhaust muffler is developed by using Visual Basic, Matlab Setup Factory software.Secondly, the 3D model of original muffler is carried out by UG and geometry clean-up and mesh job are finished by ANSA to get the FE model for flow field and acoustic analysis. Using ANSYS CFX software the velocity, temperature and pressure in muffler are figured out, by using in SYSNOISE, the acoustic FE model is calculated, and acoustic characteristic analysis of the muffler and erch chamber are achieved.At last, basing on the comparison between the simulation result and the experimental result, the two improvement models are presented. After flow field simulation and acoustics field are carried out of the improvement models, the fit model is gained. The experiment show that the power loss of the muffler change a little and noise is reduced in 1~2dB, which makes out that the improvement model is correct and valid. |
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