Shape optimisation on constrained single-chamber muffler by using GA method and mathematical gradient method

Shape optimisation to maximise a muffler's performance is essential when the space volume of the muffler is constrained for the necessity of maintenance and operation in practical design work. This paper presents numerical optimal studies on single chamber mufflers. Additionally, two numerical approaches, the genetic algorithm (GA) method and mathematical gradient searches, are applied to muffler design work. In this paper, the exterior penalty function method (EPFM), interior penalty function method (IPFM), and feasible direction method (FDM) all belong to mathematical optimal searches. The four-pole transfer matrix was used in evaluating the sound transmission loss (STL) in conjunction with the numerical techniques. Furthermore, a numerical case of noise elimination of pure tone noise was studied. Before optimisation, a simple example was tested and compared with the experimental data in order to check the accuracy of the mathematical model. Results reveal that multiple local optimal solutions exist with respect to the GA and gradient methods. The optimal values of STL in the GA and the gradient method are found to be the same. Consequently, we investigated GA parameters and optimal muffler shapes that produced various pure tones. From an economics point of view, GA is indeed a good tool that provides a quick and effective approach in optimising the shape of single-chamber mufflers.