Abstract
The finite element method is employed to calculate the transmission loss of three-pass perforated reactive and hybrid mufflers. The effects of perforated tubes and bulkheads on the transmission loss of three-pass reactive mufflers are investigated numerically. Two types of hybrid mufflers are considered, and the effects of sound-absorbing material filling and packed outlet tube on the acoustic attenuation performance of mufflers are analyzed. The perforations of the tubes and bulkheads and sound-absorbing material filling are demonstrated to have significant influence on the acoustic attenuation behaviors of the mufflers. The perforation of the tubes and bulkheads may shift the resonance from the low- to middle-frequency range. The sound-absorbing material filling in the middle chamber improves the acoustic attenuation performance at middle to higher frequencies and provides a relatively flat and broadband acoustic attenuation. It is found that the solid inlet or outlet tube replacing the perforated tube and sound-absorbing material filling in the middle chamber increases the pressure drops, while the rest configurations change the pressure drops slightly.
Highlights
Three-pass perforated (TPP) muffler is a highly desirable device to reduce the vehicle’s exhaust noise with reasonable low backpressure
The pressure drops of different configurations are predicted using the software ANSYS Fluent
The perforated tubes have the inner diameter of d = 48:8 mm, the tube thickness of tw = 1:5 mm, the perforated diameter of dh = 2:5 mm, and perforated porosity of u = 6%
Summary
Three-pass perforated (TPP) muffler is a highly desirable device to reduce the vehicle’s exhaust noise with reasonable low backpressure. The 1D approaches are valid only at low frequencies since these studies assumed the plane wave propagation in the axial direction and excluded the effect of threedimensional (3D) waves inside the mufflers. The numerical methods such as finite element method (FEM) and boundary element method (BEM) are no longer confined to a plane wave treatment. Ross[5] introduced the FEM to determine the transmission loss of simple perforated muffler using the measured acoustic impedance of perforation.
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