Shape optimization of reactive mufflers using threshold acceptance and finite element methods

Abstract

Recently, the acoustic performance of reactive mufflers under space constraint became important. In this paper the attenuation performance of single and double expansion-chambers under space constraint is presented using a shape optimization analysis with a novel scheme called Threshold Acceptance (TA), the best design obtained by the shape optimization method are analysed by Finite Element Method (FEM). The numerical assessment is based on the maximisation of the sound transmission loss (STL) using the Transfer Matrix Method (TMM), a modelling method based on the plane wave propagation model. The FEM solution used to analyse the STL of the shape optimized mufflers is based on the Acoustic Power method, a standard computational code COMSOL Multiphysics is used to analyse in 3D the sound attenuation of the mufflers by the FE method. The acoustical ability of the mufflers obtained is than assessed by comparing the FEM solution with the analytical method. Results show that the maximal STL is precisely located at the desired targeted tone. In addition, the acoustical performance of mufflers with double expansion-chamber is found to be superiors to the other one. Consequently, this approach provides a quick and novel scheme for the shape optimization of reactive mufflers