Acoustic behaviour of elliptical mufflers with single-inlet and double-outlet

Denia, F.D., Baeza, L., Albelda, J. and Fuenmayor, F.J. (2003) Acoustic behaviour of elliptical mufflers with single-inlet and double-outlet. In Proceedings of the Tenth International Congress on Sound and Vibration. pp. 3287-3294 .

Abstract

Expansion chambers with single-inlet and double-outlet are used in the exhaust system of internal combustion engines since they provide noise attenuation similar to simple chambers (single inlet/outlet), and reduce the flow noise and back pressure. This work presents a detailed analysis of the acoustic attenuation performance of elliptical expansion chambers with single-inlet and double-outlet. First, the finite element method (FEM) is considered in order to obtain a reference solution. Then, the mode-matching method (MMM) is applied at the area discontinuities of the muffler, considering a circular inlet pipe, a central elliptical chamber and two circular outlet pipes. This method reduces the computational requirements and enables to couple the acoustic fields within each region, described by means of Mathieu functions in the elliptical chamber and Bessel functions in the circular pipes. The solution given by this analytical approach is compared with finite element results and experimental measurements for a selected configuration, showing a good agreement. The acoustic behaviour is then analysed in detail as a function of the chamber length, the . eccentricity of the elliptical cross-section and the position of the inlet and outlet pipes. Some potential means to improve the acoustic performance are proposed.

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Contributors

Author: L. Baeza

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