Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

Abstract

A systematic comparative examination of different single-chamber and double-chamber muffler geometries, comprised of various baffle geometry and size, number of chambers, and inlet-outlet positioning was conducted to determine the most suitable geometry for size-efficient mufflers which can meet size-limitations of automotive applications, confirming enhanced transmission loss (TL). First, we considered a reference model for validation of the simulation method. Then, we objectively studied the effects of circular and rectangular baffles of different sizes on the TL of single-chamber mufflers. Next, double- and single-chamber models were compared. Consequently, to better analyze the performance of the representative benchmark double-chamber muffler, the effects of different layouts of the outlet were studied and the corresponding TL was derived, while the inlet and baffle type and size were fixed. Finally, the effect of inlet layout, considering given outlet position, baffle type, and size, was studied on the noise control performance of the muffler. Results indicate that the 75% circular baffle has a wide frequency range and high TL of 58 dB, where the 75% rectangular plate baffle has a transmission loss of 67 dB. The double-chamber muffler has a wider frequency range and a higher TL of 78 dB compared to the single-chamber muffler. Moreover, changes in the inlet-outlet of the silencer significantly affect TL. As the inlet-outlet positioning of the silencer greatly contributes to the space constraints and packaging of the vehicle components, therefore, the variations of the inlet-outlet position of the silencer in the limited space available in vehicles need to be considered as an important design parameter, considering packaging limitations and noise control performance, which can significantly affect tailpipe radiated noise.