Optimal Design of Mufflers Equipped with Pod and Concentric Acoustical Rings using the SA Method

Abstract

Abstract There has been, of recently, much research on mufflers lined with sound absorbing material. In dealing with high frequency noise emitted from venting systems, a sound absorbing material inside a tube covered with a perforated plate has been used. However, the acoustical performance of mufflers equipped with one-layer of sound absorbing material has still proved to be insufficient. In order to promote acoustic performance, a design and theoretical assessment on pod mufflers hybridized with multi-layer concentric sound- absorbing rings is proposed. By using the acoustical-lumped-method, a four-pole system matrix for evaluating the acoustic performance (STL) will emerge. During the optimization process, the simulated annealing (SA) method, which is a robust scheme utilized to search for the global optimum by imitating a physical annealing process, is used. Before dealing with a broadband noise, the STL’s maximization relative to a one-tone noise (1000Hz) is offered to confirm the SA method’s reliability. To appreciate the influence of acoustical efficiency with respect to the design parameters, an analysis of design parameters (dh: the diameter of a perforated hole; W: the width of an air channel; R: acoustic flow resistivity of the acoustic fiber; σ : the porosity of the perforated plate; Df: the thickness of the acoustic fiber; L1: the horizontal length of the sound absorbing ring) is completed. Subsequently, to bring into focus the acoustical interaction with respect to the number of air-channels (between the sound absorbing rings), three types of mufflers (mufflers A∼C) hybridized with one, two, and three air-channels have been surveyed. Results reveal that for a rectangular muffler internally conjugated with one air-channel, the maximal STL is located at the desired tone, and the acoustical performance of a cone muffler will increase if the number of air-channels internally conjugated within the cone muffler increases. Consequently, the approach used for the optimal design of the STL on pod mufflers internally equipped with multiple air-channels within a space-constrained situation can be easily assessed.