Generalized analysis of a muffler with any number of interacting ducts

Abstract

The muffler elements that use perforated elements for acoustic attenuation are common in practice. In typical commercial mufflers perforated elements are used involving two, three, four or more interacting ducts. Analysis of such configurations involves writing down the basic governing equations of mass continuity, momentum balance, etc., and then elimination of velocity variables to obtain the coupled ordinary differential equations in terms of acoustic pressure variables. Mathematical modelling and the consequent analytical derivation of the transmission loss for these multi-duct acoustical elements become increasingly tedious, as just not the number of ducts, but also their relative arrangement along with the boundary conditions dictate the analysis considerably. In the present paper, authors have proposed a generalization and thus an algebraic algorithm to directly produce the system matrix, eliminating the tedium of writing the basic governing equations and elimination of velocity variables. Also, a convenient approach for applying the boundary conditions is outlined here.

The Effect of Soot Layer on Transmission Losses and Noise Reduction Factor of a Diesel Particulate Filter Unit

“…As a new soot layer is loaded; therefore more transmission losses in sound waves and more noise reduction occurs. Figure (13) compares values of transmission losses of the present study and those of Allam [1]. It is clear that values of transmission losses of the present study are higher than those of Allam [1].…”

Plane wave propagation in generalized multiply connected acoustic filters

“…The medium inside the elements is assumed to be a gaseous fluid so that the rigidity assumption for the walls can be relied upon to a reasonable degree of accuracy. These elements can be simple rigid walled ducts, expansion chambers with or without any extended inlet/outlet, concentric tube resonators, duct with any number of mutually interacting perforated ducts, 16 or for that matter, any other newly developed element. The theory of deriving the transfer matrices for many of these filter elements has been discussed in the literature.…”

A Study on Exhaust Muffler Counteract

“…Installing exhaust muffler is the most direct and effective method to control the exhaust noise [1]. But most of the traditional exhaust mufflers are composed of expansion chamber, and perforated pipe or perforated board [2], whose exhaust resistance is rather great and whose function of noise reduction is very poor, especially for the low frequency, which is the major part of exhaust noise [3]. Pointing at the problem in the traditional mufflers of diesel engines, the author puts forth a new theory of exhaust silencer of diesel engine based on counter-phase counteract and split-gas rushing .…”