Search Results

Perforated ducts are present in most designs of exhaust mufflers, due to their convenient sound attenuation properties. While suitable tools are available for the estimation of this attenuation, accounting for the influence on attenuation of the perforated ducts for different arrangements, a similar tool but related to the back-pressure generated by mufflers containing perforated ducts is not available. In this paper, the basis for such a tool are set by defining a suitable characterisation of perforated pipes that may allow for the consideration of the influence of a particular perforated duct on the back pressure generated by a given muffler. The results obtained have been validated in a particularly simple case, and the results confirm the feasibility of the proposed methodology, while suggesting possible future improvements.

Concentric perforated duct mufflers are broadly used when designing automotive front mufflers because of their acceptable acoustic performance and their low backpressure. In the frame of the design methodologies presently used, suitable theoretical models are needed in order to estimate this performance without the need to build prototypes and perform experimental tests. A lot of work has been performed in this sense; nevertheless, there remains a reasonable doubt that the results obtained with purely linear models are representative of the muffler behaviour under actual engine conditions. In the present paper, a two dimensional finite element model is used in order to compute the transmission loss of several concentric perforated duct mufflers, and the results are compared with experimental measurements performed with a modified version of the impulse method that allows for the use of high amplitude pressure pulses as excitation.