A fully automatic 3-D analysis tool for expansion chamber mufflers

The matrix condensation technique in conjunction with the substructuring principle has been previously used to model complex commercial automotive mufflers. Though complete 3-D finite element modelling is partially eliminated, it still requires the nodal-coordinate data and connectivity data of the elements forming the segment of each substructure. It also demands the connectivity of the degrees of freedom left after matrix condensation. Thus, the data preparation phase is tedious and cannot be claimed to be simple. Moreover, the existing FEM code requires the user to have a knowledge of acoustic theory and finite element modelling. This paper describes a way to completely eliminate the data preparation phase. Given the geometric dimensions of the muffler as input, the muffler performance is obtained as the output. The results obtained are compared with analytical and experimental results for simple as well as extended-tube expansion chambers, with or without an offset