Studies Of Acoustic And Flow Resistance Characteristics Of Internal Combustion Engine Exhaust Silencers

The 3-D numerical methods are used to predict the acoustic attenuation performance and flow resistance characteristics of internal combustion engine exhaust silencers. The fundamental theories of acoustic finite element method and finite volume method, as well as the related software SYSNOISE and FLUENT are introduced. The transmission loss is predicted by the finite element method and SYSNOISE, while the pressure loss is predicted by the finite volume method and FLUENT. The comparison between the numerical results and experiments validated the accurancy of numerical methods.Numerical results showed that the configurations of inlet/outlet affect transmission loss and pressure loss at different degree. Extensions of inlet and outlet tubes into chambers produce axial direction resonance, and increase the acoustic attenuation and decrease the pressure loss. The pressure loss is lowered as increasing the extensions. Gradual contraction and dividing tubes or guiding annulus affect the silencers' acoustic attenuation performance marginally but decrease the pressure loss to a considerable degree. Compared to expansion chambers, perforated tubes' influence on the acoustic performance of silencers is marginal at lower frequencies, important at medium frequencies and limited at higher frequencies, while the pressure loss is much lower than the others.Compared to the expansion chambers with concentric inlet/outlet, the offset of inlet or outlet affects the acoustic attenuation performance of silencers largely at higher frequencies and widens the effective frequency band. However, the offset inlet and offset outlet can not improve the acoustic attenuation performance of the expansion chamber. The acoustic attenuation performance of chambers with single-inlet and...