Numerical Optimization of Rectangular Mufflers with Multi-channel Splitters Using the Simulated Annealing Method

Abstract

Rectangular mufflers internally hybridized with splitters have been extensively applied in industrial noise abatement. However, there has been a palpable lack of academic work directed toward space-constrained mufflers conjugated with multi-channel splitters that disperse venting fluid and reduce secondary noise. That being so, an analysis of the Sound Transmission Loss (STL) of rectangular mufflers internally hybridized with multiple parallel splitters that are optimally designed to perform within a limited space will be considered, here. By using an acoustical lumped method, a four-pole system matrix for evaluating the acoustic performance (STL) emerges. 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 (250Hz) is offered to confirm the SA method’s reliability. Moreover, the mathematical model is also checked for accuracy. To appreciate the influence of acoustical efficiency with respect to the design parameters, the sensitivity analysis of six design parameters (dh: the diameter of a perforated hole; W: the width of 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 splitter) is performed. Subsequently, to bring into focus the acoustical interaction with respect to the number of air-channels (between the splitters), three types of mufflers (mufflers A∼C) hybridized with one, two, and four air-channels (with parallel splitters) have been surveyed. Results divulge that for a rectangular muffler internally conjugated with a one-channel splitter, the maximal STL is located at the desired tone. The acoustical performance of a rectangular muffler will increase and the induced back pressure will decrease simultaneously if the number of the splitters internally conjugated within the rectangular muffler increases. Consequently, optimally designed rectangular mufflers with multiple parallel splitters that avoid secondary noise induced by high speed flow while simultaneously maximizing acoustical performance within a constrained space are preferable.