Acoustic Power in Lined Ducts

AbstractThis study investigates the suppression of the sound produced when a jet, issued from a circular nozzle or hole in a plate, goes through a similar hole in a second plate. The sound, known as a hole tone, is encountered in many practical engineering situations. The mean velocity of the air jet $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}u_0$ was $6\text {--}12\ \mathrm{m}\ {\mathrm{s}}^{-1}$. The nozzle and the end plate hole both had a diameter of 51 mm, and the impingement length $L_{im}$ between the nozzle and the end plate was 50–90 mm. We propose a novel passive control method of suppressing the tone with an axisymmetric obstacle on the end plate. We find that the effect of the obstacle is well described by the combination ($W/L_{im}$, $h$) where $W$ is the distance from the edge of the end plate hole to the inner wall of the obstacle, and $h$ is the obstacle height. The tone is suppressed when backflows from the obstacle affect the jet shear layers near the nozzle exit. We do a direct sound computation for a typical case where the tone is successfully suppressed. Axisymmetric uniformity observed in the uncontrolled case is broken almost completely in the controlled case. The destruction is maintained by the process in which three-dimensional vortices in the jet shear layers convect downstream, interact with the obstacle and recursively disturb the jet flow from the nozzle exit. While regions near the edge of the end plate hole are responsible for producing the sound in the controlled case as well as in the uncontrolled case, acoustic power in the controlled case is much lower than in the uncontrolled case because of the disorganized state.

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Acoustic power flow measurement in a thermoacoustic resonator by means of laser Doppler anemometry (L.D.A.) and microphonic measurement

Applied Acoustics ◽

10.1016/s0003-682x(99)00046-8 ◽

2000 ◽

Vol 60 (1) ◽

pp. 1-11 ◽

Cited By ~ 31

Author(s):

H. Bailliet ◽

P. Lotton ◽

M. Bruneau ◽

V. Gusev ◽

J.C. Valière ◽

...

Keyword(s):

Flow Measurement ◽

Power Flow ◽

Laser Doppler Anemometry ◽

Acoustic Power ◽

Laser Doppler

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Numerical Modeling and Performance Evaluation of Standing Wave Thermoacoustic Refrigerators with a Multi-Layered Stack

Energies ◽

10.3390/en13174360 ◽

2020 ◽

Vol 13 (17) ◽

pp. 4360

Author(s):

Umar Nawaz Bhatti ◽

Salem Bashmal ◽

Sikandar Khan ◽

Rached Ben-Mansour

Keyword(s):

Standing Wave ◽

Numerical Study ◽

Temperature Drop ◽

Acoustic Power ◽

Heat Energy ◽

Coefficient Of Performance ◽

Material Layer ◽

And Performance ◽

Stacked Material ◽

Thermoacoustic Refrigerators

Thermoacoustic refrigerators have huge potential to replace conventional refrigeration systems as an alternative clean refrigeration technology. These devices utilize conversion of acoustic power and heat energy to generate the desired cooling. The stack plays a pivotal role in the performance of Standing Wave Thermoacoustic Refrigerators (SWTARs), as the heat transfer takes place across it. Performance of stacks can be significantly improved by making an arrangement of different materials inside the stack, resulting in anisotropic thermal properties along the length. In the present numerical study, the effect of multi-layered stack on the refrigeration performance of a SWTAR has been evaluated in terms of temperature drop across the stack, acoustic power consumed and device Coefficient of Performance (COP). Two different aspects of multi-layered stack, namely, different material combinations and different lengths of stacked layers, have been investigated. The combinations of four stack materials and length ratios have been investigated. The numerical results showed that multi-layered stacks produce lower refrigeration temperatures, consume less energy and have higher COP value than their homogeneous counterparts. Among all the material combinations of multi-layered stack investigated, stacks composed of a material layer with low thermal conductivity at the ends, i.e., RVC, produced the best performance with an increase of 26.14% in temperature drop value, reduction in the acoustic power consumption by 4.55% and COP enhancement of 5.12%. The results also showed that, for a constant overall length, an increase in length of side stacked material layer results in an increase in values of both temperature drop and COP.

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Experimental Investigation and Modeling of Inertance Tubes

Journal of Fluids Engineering ◽

10.1115/1.1989369 ◽

2005 ◽

Vol 127 (5) ◽

pp. 1029-1037 ◽

Cited By ~ 6

Author(s):

L. O. Schunk ◽

G. F. Nellis ◽

J. M. Pfotenhauer

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Acoustic Power ◽

Operating Conditions ◽

Thermodynamic Efficiency ◽

Pulse Tube ◽

Design Charts ◽

Wide Range ◽

Pulse Tube Refrigerators

Growing interest in larger scale pulse tubes has focused attention on optimizing their thermodynamic efficiency. For Stirling-type pulse tubes, the performance is governed by the phase difference between the pressure and mass flow, a characteristic that can be conveniently adjusted through the use of inertance tubes. In this paper we present a model in which the inertance tube is divided into a large number of increments; each increment is represented by a resistance, compliance, and inertance. This model can include local variations along the inertance tube and is capable of predicting pressure, mass flow rate, and the phase between these quantities at any location in the inertance tube as well as in the attached reservoir. The model is verified through careful comparison with those quantities that can be easily and reliably measured; these include the pressure variations along the length of the inertance tube and the mass flow rate into the reservoir. These experimental quantities are shown to be in good agreement with the model’s predictions over a wide range of operating conditions. Design charts are subsequently generated using the model and are presented for various operating conditions in order to facilitate the design of inertance tubes for pulse tube refrigerators. These design charts enable the pulse tube designer to select an inertance tube geometry that achieves a desired phase shift for a given level of acoustic power.

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Microstructure and Mechanical Properties of Mg-6Zn-1.4Y Alloy Produced by Rheo-Squeeze Casting Process

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.530 ◽

2016 ◽

Vol 879 ◽

pp. 530-535

Author(s):

Xiao Gang Fang ◽

Shu Sen Wu ◽

Shu Lin Lü

Keyword(s):

Mechanical Properties ◽

Power Density ◽

Squeeze Casting ◽

Casting Process ◽

Acoustic Power ◽

Icosahedral Quasicrystal ◽

Microstructure And Mechanical Properties ◽

Average Grain Size ◽

Grain Size And Shape ◽

Semi Solid

Mg-Zn-Y alloys containing a thermally stable icosahedral quasicrystal phase (I-phase) will have wide application future on condition that primary α-Mg dendrite and the I-phase can be refined during the casting process. In this research, the microstructure and mechanical properties of the rheo-squeeze casting (RSC) Mg-6Zn-1.4Y alloys have been investigated. The Mg alloy melt was exposed to ultrasonic vibration (USV) with different acoustic power densities from 0 W/mL to 9 W/mL, and then the slurry was formed by squeeze casting. The results show that good semi-solid slurry with fine and spherical α-Mg particles could be obtained with the acoustic power density of 6 W/mL, and the average grain size and shape factor of primary α-Mg were 32 μm and 0.76, respectively. Meanwhile the coarse eutectic I-phase (Mg3Zn6Y) was refined obviously and dispersed uniformly. Compared with the samples without USV, the tensile strength and elongation of the RSC casting samples with 6 W/mL acoustic power density were elevated by 10.6% and 55.5%, respectively.

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