Multi-Pass Perforated Tube Silencers: A Computational Approach

Miazgowicz

et al. 2005

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Models for viscothermal effects in catalytic converter substrates are developed for time domain computational methods. The models are suitable for use in one-dimensional approaches for the prediction of exhaust system performance ͑engine tuning characteristics͒ and radiated sound levels. Starting with the "low reduced frequency" equations for viscothermal acoustic propagation in capillary tubes, time domain submodels are developed for the frequency-dependent wall friction, frequency-dependent wall heat transfer, and porous wall effects exhibited by catalytic converter substrates. Results from a time domain computational approach employing these submodels are compared to available analytical solutions for the low reduced frequency equations. The computational results are shown to agree well with the analytical solutions for capillary geometries representative of automotive catalytic converter substrates.

Section: Time Domain Computationsmentioning

confidence: 99%

“…Consistent with the approach for perforated tube silencers, communication between the main and secondary ducts is treated using an "interface" momentum equation given by 20,21 t l eq dU p dt…”

Section: Wall Porositymentioning

confidence: 99%

Time domain computational modeling of viscothermal acoustic propagation in catalytic converter substrates with porous walls

Dickey

Miazgowicz

et al. 2005

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“…At the expansion from the central tubes to the end chambers, an end correction is necessary in the model to account for the local multidimensional effects. 30 For simplicity, the end correction is taken from the work of Ingard 29 for concentric Helmholtz resonators as ⌬l end chamber ϭ0.425d pipeͩ 1Ϫ1. 25 d pipe…”

Section: A Geometriesmentioning

confidence: 99%

The effect of high-amplitude sound on the attenuation of perforated tube silencers

Dickey

Novak

2000

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A time-domain computational approach is applied to investigate the behavior of perforated tube silencers at high sound levels. The one-dimensional computational technique employs a lumped parameter model for the perforate flows. The lumped parameter perforate model is based on time-invariant approximations for the equivalent length l(eq) and resistance R, consistent with the use of a nonlinear perforate impedance. Empirical expressions for l(eq) and R are developed experimentally using nondimensional scaling parameters. The model is applied to geometries representative of automotive resonators and multiple-duct mufflers. Conditions are simplified from those in an actual automotive system by considering single-frequency excitation and zero mean flow. Simulations with linear perforate behavior are compared to experimental data obtained with an extended impedance tube system. Simulations with nonlinear perforate behavior for one concentric tube resonator are compared to published experimental data.

“…Ross 12 attempted the analysis of the three-pass muffler using the finite element method, but only demonstrated the results for the case where the middle pipe was just pass through ͑not perforated͒. Recently, Dickey et al 13 presented a time-domain computational analysis of a multi-pass perforated muffler, and illustrated the results for a three-pass muffler. The corresponding frequency domain analysis of this muffler was later presented by Munjal, 14 via a decoupling method, which was also refined to include the extended-tube three-pass perforated element muffler.…”

Section: Introductionmentioning

confidence: 97%

Three-pass mufflers with uniform perforations

Easwaran

Falkowski

1999

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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.