Acoustic Characteristics of an Expansion Chamber With Constant Mass Flow and Steady Temperature Gradient (Theory and Numerical Simulation)

Kim, Yang-Hann; Choi, Jae Woong; Lim, Byoung-Duk

doi:10.1115/1.2930129

Cited by 18 publications

(10 citation statements)

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“…As the temperature distribution can affect the acoustic behavior of the silencer considerably, several authors studied the influence of these gradients in the silencer transmission loss. Kim et al [17] applied an analytic multidimensional approach to some reactive configurations considering axial temperature variation and mean flow. In this work, the silencer was divided into segments of uniform temperature to model the acoustic effect of the thermal gradient, obtaining the acoustic fields in each segment by using the corresponding continuity conditions.…”

Section: Introductionmentioning

confidence: 99%

Point collocation scheme in silencers with temperature gradient and mean flow

Denia

Sánchez-Orgaz

Baeza

et al. 2016

Journal of Computational and Applied Mathematics

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This work presents a mathematical approach based on the point collocation technique to compute the transmission loss of perforated dissipative silencers with transversal temperature gradients and mean flow. Three-dimensional wave propagation is considered in silencer geometries with arbitrary, but axially uniform, cross section. To reduce the computational requirements of a full multidimensional finite element calculation, a method is developed combining axial and transversal solutions of the wave equation. First, the finite element method is employed in a two-dimensional problem to extract the eigenvalues and associated eigenvectors for the silencer cross section. Mean flow as well as transversal temperature gradients and the corresponding thermal-induced material heterogeneities are included in the model. In addition, an axially uniform temperature field is taken into account, its value being the inlet/outlet average. A point collocation technique is then used to match the acoustic fields (pressure and axial acoustic velocity) at the geometric discontinuities between the silencer chamber and the inlet and outlet pipes. Transmission loss predictions are compared favorably with a general three-dimensional finite element approach, offering a reduction in the computational effort.

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Section: Introductionmentioning

confidence: 99%

Point collocation scheme in silencers with temperature gradient and mean flow

Denia

Sánchez-Orgaz

Baeza

et al. 2016

Journal of Computational and Applied Mathematics

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“…Subsequent works [4][5][6][7][8] attempted to decoupling methods for coupled governing equations. Other works analyzed more complex perforated tube mufflers [9][10][11][12][13], while others [14][15][16] considered the temperature gradient effects on a muffler's performance. Additional works discussed exactly how sound absorbent material influences the noise reduction of a silencer [17][18].…”

Section: Introductionmentioning

confidence: 99%

Flow Induced Aerodynamic Noise Analysis of Perforated Tube Mufflers

Wang¹,

Tse²,

Chen³

2012

J. mech.

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Despite the analysis of muffler performance for many years, most works focus mainly on reducing inlet sound and fail to consider the flow effect. Most of their results correlate well with the experimental measurements. Subsequent works have considered the mean flow effect. Owing to Doppler's effect, transmission loss curve of the muffler will shift in its corresponding frequency. However, the correlation is worse than the experimental results since the flow induced noise does not include in the analysis. This work elucidates how flow induced noise affects muffler performance by analyzing a uniform flow that passes through perforated mufflers. The flow field is calculated with the CFD method, followed by evaluation of the aerodynamic noise based on the simulation results. Additionally, the procedure is simplified by computing and comparing only the total sound power induced by the flow in the muffler interior. Two muffler types, Helmholtz resonator and plug perforated tube muffler, are analyzed and discussed.

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“…Kim et al [21] presented a multidimensional analytical approach for the acoustic modelling of expansion chambers with mean flow and a temperature gradient. A segmentation technique was applied dividing the silencer into segments with constant temperature and mean flow, and matching the acoustic fields through the corresponding continuity conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The corresponding boundary surfaces are denoted by Γa and Γm, respectively, the inlet and outlet sections are represented by Γi and Γo, and the perforated surface is Γp. The temperature field is assumed one-dimensional in the central passage, reaching its maximum value at the inlet while decreasing gradually along the flow path [14,16,17,18,21,23]. A more general multidimensional function T(x,y,z) = T(x) is considered in the chamber [17].…”

Section: Introductionmentioning

confidence: 99%

Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

Denia

Sánchez-Orgaz

Martínez‐Casas

et al. 2015

Finite Elements in Analysis and Design

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A mixed finite element model has been derived for the acoustic analysis of perforated dissipative silencers including several effects simultaneously: (1) High temperature and thermal gradients in the central duct and the outer absorbent material; (2) A perforated passage carrying non-uniform axial mean flow. For such a combination, the properties of sound propagation media and flow are inhomogeneous and vary with position. The material of the outer chamber can be modelled by its complex equivalent acoustic properties, which completely determine the propagation of sound waves in the air contained in the absorbent medium. Temperature gradients introduce variations in these properties that can be evaluated through a heterogeneous temperature-dependent resistivity in combination with material models obtained at room temperature. A pressure-based wave equation for stationary medium is then used with the equivalent density and speed of sound of the absorbent material varying as functions of the spatial coordinates. Regarding the central air passage, a wave equation in terms of acoustic velocity potential can be used to model the non-uniform moving medium since the presence of temperature variations introduce not only heterogeneous acoustic properties of the air but also a gradient in the mean flow velocity. The acoustic connection between the central passage and the outer chamber is given by the acoustic impedance of the perforated duct. This impedance depends on the heterogeneous properties of the absorbent material and the non-uniform mean flow, leading to a spatial variation of the acoustic coupling and also to additional convective terms in the governing equations. The results presented show the influence of temperature, thermal gradients and mean flow on the transmission loss of automotive silencers. It has been found that high temperature and thermal-induced heterogeneity can have a significant influence on the acoustic attenuation of an automotive silencer and so should be included in theoretical models. In some particular configurations it may be relatively accurate to approximate the temperature field by using a uniform profile with an average value, specially for low resistivity materials. It has been shown, however, that this is not always possible and attenuation overestimation is likely to be predicted, mainly for high radial thermal gradients and high material flow resistivities, if the temperature distribution is not taken into account.

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Acoustic Characteristics of an Expansion Chamber With Constant Mass Flow and Steady Temperature Gradient (Theory and Numerical Simulation)

Cited by 18 publications

References 0 publications

Point collocation scheme in silencers with temperature gradient and mean flow

Point collocation scheme in silencers with temperature gradient and mean flow

Flow Induced Aerodynamic Noise Analysis of Perforated Tube Mufflers

Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

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