Three-pass mufflers with uniform perforations

Abstract

A quasi-one-dimensional approach is presented to analyze three-pass mufflers with perforated elements using numerical decoupling. The approach is further developed to include mufflers with ducts extended into the end cavities. Theoretical predictions are compared with experiments for three different muffler configurations, one fabricated and two commercially available mufflers, and shown to agree reasonably well. The effect of porosity, length of the end cavities, and expansion chamber diameter are studied. Also, the effect of ducts extending into the end cavities are investigated.

Simulation of Multiple Pass Perforated Tube Silencers Based on the Method of Characteristics

“…The first type of length correction pertaining to neck-cavity interface, referred to in fig. 4-a, follows that derived by Ingard [19], which was also used in the work of Dickey et al [7], Selamet et al [8] and Onorati [11], is as follows:…”

“…The transmission loss of two anechoically terminated multiple pass silencer configurations was determined computationally and verified experimentally for the limiting case of low sound pressure level and zero mean flow. Later, Selamet et al [8] has developed a quasi one-dimensional model to analyze three pass perforated tube silencer, based on the transfer matrix method and the numerical decoupling of Peat [5].…”

Three-pass perforated tube muffler with perforated bulkheads

“…Following the works of Selamet et al, 3 the relationship of sound pressures and particle velocities at the inlet (x = 0) and outlet (x = L p ) of the common perforated section in the middle chamber of mufflers shown in Figures 1-3 may be expressed as…”

“…where ½R can be derived from the matrix ½T of equation (62) in Selamet et al;3 p is the sound pressure; u is the particle velocity; r 0 is the density of air; c 0 is the speed of sound; r c is the complex density of soundabsorbing material; c c is the complex speed of sound in the sound-absorbing material; and subscripts 1, 2, 3, and 4 represent the perforated inlet tube, center tube, outlet tube, and expansion chamber, respectively.…”

“…Munjal 1,2 and Selamet et al 3 presented the one-dimensional (1D) frequency-domain approaches, and Dickey et al 4 developed the 1D timedomain approach to predict the acoustic attenuation performance of the typical three-pass perforated tube mufflers. For a prototype muffler, their predictions of transmission loss agree reasonably well with the experiments within the plane wave range.…”