An Optimal Design Methodology for a Family of Perforated Mufflers

Usually when mufflers are designed by well established numerical techniques like boundary element method or finite element method, the numerical model generation is time consuming often limiting the user to try various other possible design alternates. This paper proposes a shorter and faster way to handle such problems by using the conventional four-pole method which retains the transfer matrix for a muffler, this matrix keeps updating with combination of various possible muffler elements. This proves to be a quite efficient one-dimensional approach giving results with satisfactory accuracy. The muffler designs that can be made include all types of expansion chambers, Helmholtz's resonator, extended inlets/outlets, the whole family of perforated elements and many more. It provides a measure of evaluation of the muffler in terms of their Transmission Loss (TL), Insertion Loss (IL) and Noise Reduction (NR).

This paper also provides a comparison of experimental results of silencer of a tractor with that of the prediction made from the model proposed. The basic structure of the silencer includes two sets of cross-flow perforated element plugged with each other. The result comes very close to the actual values obtained. Based on the noise reduction of the silencer, it suggests an improvement. The faster and easier approach facilitates a user to get better design by readily evaluating the performance of any combinations of the above mentioned muffler elements.