muffler

Topics: Frequency, Attenuation, Acoustics Pages: 57 (5864 words) Published: December 26, 2013
Applied Acoustics 74 (2013) 1499–1510

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Applied Acoustics
journal homepage: www.elsevier.com/locate/apacoust

Transmission loss analysis of single-inlet/double-outlet (SIDO) and double-inlet/single-outlet (DISO) circular chamber mufflers by using Green’s function method
Subhabrata Banerjee, Anthony M. Jacobi ⇑
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, IL-61801, USA

a r t i c l e

i n f o

Article history:
Received 31 July 2012
Received in revised form 6 June 2013
Accepted 17 June 2013

Keywords:
Expansion-chamber mufflers
Transmission loss
Green’s function

a b s t r a c t
A Green’s function solution method is implemented to study sound attenuation in single-inlet/ double-outlet (SIDO) and double-inlet/single-outlet (DISO) circular chamber mufflers. The mufflers are modeled as piston driven rigid circular chambers containing a stationary fluid. The pistons are assumed to perform simple harmonic motion with uniform velocities. Velocity potential in the chamber is derived as a superposition of three dimensional velocity potential due to each piston. Pressure field in the chamber is calculated from the velocity potential through conservation of linear momentum equation. Acoustic pressure acting on each piston is calculated by averaging over the surface of the piston. Transmission loss (TL) is evaluated from incident and transmitted acoustic energy. TL curves for various inlet/outlet orientations derived from this method is validated with results obtained from the literature. The effect of locations of inlet/outlet on TL is studied.

Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction
Expansion chamber mufflers are widely used in automotive systems, HVAC ducts, reciprocating compressors and in other industrial systems. Sound attenuation in such mufflers is strongly dependent on geometry as well as on the orientation of inlet/outlet ports. In order to understand these effects, a number of analytical and numerical works has been reported in the literature. The simplest analytical method assumes plane wave propagation in the muffler. Based on this assumption, a four-pole parameter (transfer matrix) which maps upstream condition to downstream condition is derived. Munjal [1–3] discussed the basic concepts of four-pole parameters and derived them for different muffler configurations with rigid-wall boundary conditions. Plane wave analysis yields results only for acoustically long chamber mufflers below the cutoff frequency of higher order modes. In acoustically short chamber mufflers, higher order modes are not completely suppressed as they propagate along the chamber, and they influence the propagation characteristics. In order to overcome the limitations of plane wave analysis, Ih and Lee [4] derived four-pole parameter for a circular chamber with end inlet/outlet, accounting for higher order mode effects by assuming uniform velocity piston sources. The three dimensional acoustic field in the chamber was expressed as ⇑ Corresponding author. Tel.: +1 217 333 4108; fax: +1 217 244 6534. E-mail addresses: banerje6@illinois.edu (S. Banerjee), a-jacobi@illinois.edu (A.M. Jacobi).

0003-682X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apacoust.2013.06.007

an infinite summation of rigid body modes (eigenfunctions). Yi and Lee [5,6] obtained four-pole parameters of a circular expansion chamber with side-inlet/outlet based on uniform velocity piston driven model. Experimental validation of the model for different inlet/outlet locations established the effectiveness of the model. Selamet et al. [7–9] developed a three dimensional mode matching technique to study the attenuation for various inlet/outlet conditions in a circular chamber muffler. Similar to prior work [4], acoustic field was expressed as a linear combination of eigenfunctions for a rigid cylinder. Using...


References: international congress on sound and vibration, Stockholm, Sweden. 7–10
July, 2003, 3287–3294.
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