Análise de silenciadores de escape automotivo visando redução da emissão de ruído

Abstract

This work has the objective of evaluating the sound reduction in vehicle mufflers where the use of methodologies for numerical and computational analysis is used. The main parameter was the transmission loss (TL - Transmission Loss) in reactive exhausts with geometry defined in real parameters. For the first of analytical resolution in search of the determination of accessory elements, such as ducts and cutoff frequency, analytical equations were used, and for the geometry mold, the transfer matrix method was used. The second step consisted of a numerical analysis using the commercial software Matlab®. Based on the previous geometry, it was possible to create different configurations in order to determine which parameters have the greatest influence on sound attenuation. Thus, the length of the muffler and the diameter of the inlet and outlet ducts of the exhaust gases become the determining factors for noise reduction. The length of the silencer displaced the curves around the frequency, without changing the attenuation limits. For the diameter of the ducts, there was a proportional relationship between sound attenuation and this dimension. These two parameters are essential when designing an exhaust system, where an optimal condition is obtained by a combination of these when assessing transmission loss. Next, the two methods used were complementary for the creation of a theoretical model of automotive silencer.