| Summary: | 碩士 === 逢甲大學 === 機械工程學所 === 93 === Abstract
This paper is aimed to investigate the acoustic modeling of catalyst converter, and the effect of the transmission loss of catalyst inside muffler. The catalyst is formed with metal which is full of creases. Because of it’s complex shape, it is hard to analyze it. So in this research, it regards the catalyst as the porous material, and regards the catalyst as the second media of outside layer of air, establish the sound field model of catalyst. On the other hand, basing on acoustic theory, we deduce the governing equation from sound field inside muffler, and the boundary element method is chosen to be a numerical tool to calculate the transmission loss inside muffler. The numerical result shows a good agreement with theory, which validates the reliability of computer program and numerical method in present method.
In the aspect of sound absorption, we use experiments to test and verify with numerical result and theory. The result proves that the catalyst indeed have the effect of sound absorption. In the aspect of transmission loss, we investigate the effects of the transmission loss by comparing the catalyst with different length、different caliber size、different cell per square inch (cpsi)、and different place angle. The result shows the catalyst promoted the effects of transmission loss when it was applied in the muffler, the different cell per square inch and the place angle can create the effects of different transmission loss, but the thickness, and the caliber size certainly cannot have the effects to the transmission loss.
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