Numerical Estimation of End Corrections in Extended-Duct and Perforated-Duct Mufflers

Abstract

One-dimensional models for extended-duct and perforated-duct mufflers require the introduction of end corrections in order to account for multidimensional effects at the junctions. In this paper, a numerical two-dimensional finite element calculation has been used in order to obtain information on these end corrections. The results have been validated through comparison with experimental measurements performed with a modified version of the impulse method. Then, the influence of the different geometric characteristics of the mufflers on the end correction have been studied. A general correlation in terms of relevant nondimensional parameters is given for extended-duct mufflers, whereas for perforated mufflers a general correlation has not been obtained due to the eventual coupling with other attenuation mechanisms.

Sub-chamber optimization for silencer design

“…Reactive and dissipative silencers with a simple expansion chamber have been extensively investigated [1][2][3][4][5][6][7][8][9][10]. For reactive silencers, Selamet and Ji [1] studied the effect of adding inlet/outlet extensions on the suppression of the pass-bands of the dome-like transmission loss (TL) pattern.…”

Effect of wall thickness on the end corrections of the extended inlet and outlet of a double-tuned expansion chamber

“…Munjal and Gowri [7] implicitly did not consider the effect of wall thickness in their 3-D FE model inasmuch as they made use [5] did not mention the value of wall thickness but, as the end corrections are measured experimentally, they tally with the new end corrections observed in the present investigation except for D/d = 4. Generally, wall thickness varies from 1 mm to 2 mm.…”

“…Incidentally, Torregrosa concluded experimentally that the effect of length is negligible [5]. Kang and Ji concluded that the acoustic length correction decreases with an increase in the duct extension, and the difference in the acoustic length corrections gets smaller with increase of the ratio La d , and almost independent of the chamber length for long chambers [6].…”

“…[5,6,8], variation between the measurements or 3-D analysis and the 1-D model is due to the presence of three-dimensional (3-D) waves, which are not accounted for in the plane wave analysis. From the position of resonance peaks in the 1-D and 3-D/experimental models for a given configuration, it is seen that the resonance peak in the 3-D model had moved to the left of the corresponding resonance peak in the 1-D model, thereby indicating that the effective extended length in the 3-D model had increased by an end correction, d. Therefore, in order to consider the evanescent 3-D effects near the discontinuities, the geometric length in the 1-D model has to be increased by same d, in order to obtain the effective acoustic length [8].…”

“…Torregrosa et al explored the possibility of obtaining relatively accurate prediction of the acoustic performance of extended duct and perforated duct mufflers by introducing a suitable end correction into simple one-dimensional models. They introduced a general correlation in terms of a non-dimensional parameter such that multidimensional effects associated with the evanescent higher-order modes at a sudden area change are considered [5]. Kang and Ji examined the effects of chamber geometry like chamber length, duct extension and diametric ratio on the end correction and provided an approximate expression for evaluation of the end correction [6].…”