Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23524
M. Wagner, P. Pinsky, M. Malhotra
A solution methodology is introduced for the efficient computation of the acoustic field over restricted domains and for a frequency window. Typically, such partial field solutions include, for example, surfaces enclosing the radiating structure or even single points in the computational domain. The multiple-frequency partial-field (MFPF) method starts out by reformulating the finite element matrix system into a suitable shifted form. The DtN map is used as a radiation boundary condition and is interpreted as a low rank update of the matrix problem. The shifted standard form is then approximated by a rational matrix-valued Padé approximant and solved simultaneously over a frequency range. To obtain the Padé approximation, a banded unsymmetric Lanczos process is applied on the standard shifted form exploiting the matrix Padé-via-Lanczos connection. Numerical examples show the feasibility of the outlined procedure.
{"title":"A Multiple-Frequency Partial-Field Method for Exterior Acoustics Based on Padé via Lanczos Approximants","authors":"M. Wagner, P. Pinsky, M. Malhotra","doi":"10.1115/imece2001/nca-23524","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23524","url":null,"abstract":"\u0000 A solution methodology is introduced for the efficient computation of the acoustic field over restricted domains and for a frequency window. Typically, such partial field solutions include, for example, surfaces enclosing the radiating structure or even single points in the computational domain. The multiple-frequency partial-field (MFPF) method starts out by reformulating the finite element matrix system into a suitable shifted form. The DtN map is used as a radiation boundary condition and is interpreted as a low rank update of the matrix problem. The shifted standard form is then approximated by a rational matrix-valued Padé approximant and solved simultaneously over a frequency range. To obtain the Padé approximation, a banded unsymmetric Lanczos process is applied on the standard shifted form exploiting the matrix Padé-via-Lanczos connection. Numerical examples show the feasibility of the outlined procedure.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121017931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23521
J. McDaniel, Cory L. Clarke
This paper investigates dynamic models of submerged objects which are obtained by acoustically ensonifying an object and measuring the scattered field at a single point while varying frequency. From such measurements, one can compute an effective impedance that physically represents the impedance of a half-space that would reflect a normally incident plane wave with the same amplitude as the wave scattered by the object. This effective impedance is shown to be passive and causal when the magnitude of the scattered wave is less than one. The effective impedance is related to reflection and impedance matrices matrices that arise in network formulations for the scattering of plane and spherical waves.
{"title":"Simplified Dynamic Models of Submerged Objects From Limited Scattering Data","authors":"J. McDaniel, Cory L. Clarke","doi":"10.1115/imece2001/nca-23521","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23521","url":null,"abstract":"\u0000 This paper investigates dynamic models of submerged objects which are obtained by acoustically ensonifying an object and measuring the scattered field at a single point while varying frequency. From such measurements, one can compute an effective impedance that physically represents the impedance of a half-space that would reflect a normally incident plane wave with the same amplitude as the wave scattered by the object. This effective impedance is shown to be passive and causal when the magnitude of the scattered wave is less than one. The effective impedance is related to reflection and impedance matrices matrices that arise in network formulations for the scattering of plane and spherical waves.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"32 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116407134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23538
K. Frampton
Although the application of active control to vibrations has been investigated from many years, the extension of this technology to large-scale systems has been thwarted, in part, by an overwhelming need for computational effort, data transmission and electrical power. This need has been overwhelming in the sense that the potential applications are unable to bear the power, weight and complex communications requirement of large-scale centralized control systems. Recent developments in MEMS devices and networked embedded devices have changed the focus of such applications from centralized control architectures to decentralized ones. A decentralized control system is one that consists of many autonomous, or semi-autonomous, localized controllers called nodes, acting on a single plant, in order to achieve a global control objective. Each of these nodes has the following capabilities and assets: 1) a relatively limited computational capability including limited memory, 2) oversight of a suite of sensors and actuators and 3) a communications link (either wired or wireless) with neighboring or regional nodes. The objective of a decentralized controller is the same as for a centralized control system: to maintain some desirable global system behavior in the presences of disturbances. However, decentralized controllers do so with each node possessing only a limited amount of information on the global systems response. Exactly what information each node has access to, and how that information is used, is the topic of this investigation.
{"title":"Decentralized Control of Structural Acoustic Radiation","authors":"K. Frampton","doi":"10.1115/imece2001/nca-23538","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23538","url":null,"abstract":"\u0000 Although the application of active control to vibrations has been investigated from many years, the extension of this technology to large-scale systems has been thwarted, in part, by an overwhelming need for computational effort, data transmission and electrical power. This need has been overwhelming in the sense that the potential applications are unable to bear the power, weight and complex communications requirement of large-scale centralized control systems. Recent developments in MEMS devices and networked embedded devices have changed the focus of such applications from centralized control architectures to decentralized ones. A decentralized control system is one that consists of many autonomous, or semi-autonomous, localized controllers called nodes, acting on a single plant, in order to achieve a global control objective. Each of these nodes has the following capabilities and assets: 1) a relatively limited computational capability including limited memory, 2) oversight of a suite of sensors and actuators and 3) a communications link (either wired or wireless) with neighboring or regional nodes. The objective of a decentralized controller is the same as for a centralized control system: to maintain some desirable global system behavior in the presences of disturbances. However, decentralized controllers do so with each node possessing only a limited amount of information on the global systems response. Exactly what information each node has access to, and how that information is used, is the topic of this investigation.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122111319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23527
Dongjai Lee, A. Belegundu, G. Koopmann
This paper presents a rib-stiffener pattern design method for reducing vibration energy and/or radiated acoustic power from a vibrating structure. Structural dynamics, acoustics and optimization are programmed in a unified code. To avoid difficulties in defining proper design variables such as the location, the number and the size of stiffeners to be attached on a structure, this paper adopts the idea of “topology optimization”, based on finite elements. This approach enables one to find an optimal rib-stiffener pattern by using a simple design variable, e.g., the density of finite elements. To illustrate this method, a rectangular plate with clamped edges is optimized to reduce the radiated sound power/kinetic energy and the results are compared to that the same plate but without rib-stiffeners.
{"title":"Optimum Stiffener Design to Reduce Broadband Vibration and Sound Radiation","authors":"Dongjai Lee, A. Belegundu, G. Koopmann","doi":"10.1115/imece2001/nca-23527","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23527","url":null,"abstract":"\u0000 This paper presents a rib-stiffener pattern design method for reducing vibration energy and/or radiated acoustic power from a vibrating structure. Structural dynamics, acoustics and optimization are programmed in a unified code. To avoid difficulties in defining proper design variables such as the location, the number and the size of stiffeners to be attached on a structure, this paper adopts the idea of “topology optimization”, based on finite elements. This approach enables one to find an optimal rib-stiffener pattern by using a simple design variable, e.g., the density of finite elements. To illustrate this method, a rectangular plate with clamped edges is optimized to reduce the radiated sound power/kinetic energy and the results are compared to that the same plate but without rib-stiffeners.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131996306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23540
M. Moondra, Sean F. Wu
The paper examines the effectiveness of the Helmholtz equation least-squares (HELS) method (Wu and Yu, J. Acoust. Soc. Am., Vol. 104, 2054–2060, 1998; Wu, J. Acoust. Soc. Am., Vol. 107, 2511–2522, 2000) in visualizing the areas that are prone to noise transmission into a full-size vehicle passenger compartment due to exterior excitations such as the engine and turbulent flow. To simulate sound transmission, harmonic excitations are assumed to act on arbitrarily selected vehicle interior surfaces. The surface acoustic pressures are calculated using the boundary element method (BEM) based Helmholtz integral equation. A fine mesh for the interior cavity is generated so as to yield as accurate as possible the acoustic pressure distributions as benchmark using the BEM codes. The radiated acoustic pressures inside the vehicle compartment are calculated and taken as the input to the HELS formulation. Once the HELS formulation is established, the acoustic pressure anywhere including the vehicle interior surface is reconstructed. The normal component of the surface velocity can be reconstructed in a similar manner. Consequently, the normal component of the time-averaged acoustic intensity and acoustic energy flow inside a vehicle passenger compartment can be visualized. This three-dimensional acoustic image can provide valuable insight into vehicle interior noise reduction. The reconstructed acoustic pressures are compared with the benchmark values evaluated at the same locations. The effect of the measurement locations on the accuracy of reconstruction is investigated.
本文检验了亥姆霍兹方程最小二乘(HELS)方法的有效性(Wu和Yu, J. Acoust。Soc。点。，第104卷，2054-2060,1998年;吴杰。Soc。点。， Vol. 107, 2511-2522, 2000)在可视化的区域，容易产生噪音传播到一个全尺寸的车辆乘客室由于外部激励，如发动机和湍流。为了模拟声音的传播，假设在任意选择的车辆内部表面上存在谐波激励。采用基于亥姆霍兹积分方程的边界元法计算表面声压。为了尽可能精确地得到作为基准的声压分布，利用边界元代码生成了内部腔体的细网格。计算了车辆舱内的辐射声压，并将其作为HELS公式的输入。一旦建立了HELS公式，就可以重建包括车辆内部表面在内的任何地方的声压。表面速度的法向分量可以用类似的方法重建。因此，时间平均声强和声能流的法向分量可以被可视化。这种三维声学图像可以为车辆内部降噪提供有价值的见解。将重建的声压与同一位置的基准声压进行了比较。研究了测量位置对重建精度的影响。
{"title":"Visualization of Sound Transmission Into a Vehicle Passenger Compartment","authors":"M. Moondra, Sean F. Wu","doi":"10.1115/imece2001/nca-23540","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23540","url":null,"abstract":"\u0000 The paper examines the effectiveness of the Helmholtz equation least-squares (HELS) method (Wu and Yu, J. Acoust. Soc. Am., Vol. 104, 2054–2060, 1998; Wu, J. Acoust. Soc. Am., Vol. 107, 2511–2522, 2000) in visualizing the areas that are prone to noise transmission into a full-size vehicle passenger compartment due to exterior excitations such as the engine and turbulent flow. To simulate sound transmission, harmonic excitations are assumed to act on arbitrarily selected vehicle interior surfaces. The surface acoustic pressures are calculated using the boundary element method (BEM) based Helmholtz integral equation. A fine mesh for the interior cavity is generated so as to yield as accurate as possible the acoustic pressure distributions as benchmark using the BEM codes. The radiated acoustic pressures inside the vehicle compartment are calculated and taken as the input to the HELS formulation. Once the HELS formulation is established, the acoustic pressure anywhere including the vehicle interior surface is reconstructed. The normal component of the surface velocity can be reconstructed in a similar manner. Consequently, the normal component of the time-averaged acoustic intensity and acoustic energy flow inside a vehicle passenger compartment can be visualized. This three-dimensional acoustic image can provide valuable insight into vehicle interior noise reduction. The reconstructed acoustic pressures are compared with the benchmark values evaluated at the same locations. The effect of the measurement locations on the accuracy of reconstruction is investigated.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"32 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132609811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23505
D. A. Bourgoyne, Carolyn Q. Judge, J. Hamel, S. Ceccio, D. Dowling
This paper describes an experimental effort to identify and document the turbulent flow, induced surface pressures, and structural response of a hydrofoil at chord-based Reynolds numbers up to 60 million. Special interest is focused on the trailing edge of the foil where most of the measurements are made. The experiments are conducted at the US Navy’s W. B. Morgan Large Cavitation Channel with a two-dimensional test-section-spanning hydrofoil (2.1 m chord, 3.0 m span) at flow speeds from 0.5 to 18.3 m/s. The foil section is a modified NACA 16 with a flat pressure side. The measurements presented in this paper include foil surface static and dynamic pressures, foil vibration, LDV-determined average flow speeds and turbulence quantities, and PIV flow fields in the immediate vicinity of the foil’s trailing edge.
本文描述了一项实验工作，以确定和记录湍流、诱导表面压力和水翼在弦基雷诺数高达6000万时的结构响应。特别的兴趣集中在箔的后缘，在那里进行了大部分的测量。实验在美国海军的W. B. Morgan大型空化通道中进行，实验采用了一个二维跨截面水翼(2.1 m弦，3.0 m跨)，流速从0.5到18.3 m/s。箔段是一个改进的NACA 16与一个平坦的压力侧。本文给出的测量包括箔面静、动压力、箔振动、ldv确定的平均流速和湍流量，以及箔尾缘附近的PIV流场。
{"title":"Lifting Surface Flow, Pressure, and Vibration at High Reynolds-Number","authors":"D. A. Bourgoyne, Carolyn Q. Judge, J. Hamel, S. Ceccio, D. Dowling","doi":"10.1115/imece2001/nca-23505","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23505","url":null,"abstract":"\u0000 This paper describes an experimental effort to identify and document the turbulent flow, induced surface pressures, and structural response of a hydrofoil at chord-based Reynolds numbers up to 60 million. Special interest is focused on the trailing edge of the foil where most of the measurements are made. The experiments are conducted at the US Navy’s W. B. Morgan Large Cavitation Channel with a two-dimensional test-section-spanning hydrofoil (2.1 m chord, 3.0 m span) at flow speeds from 0.5 to 18.3 m/s. The foil section is a modified NACA 16 with a flat pressure side. The measurements presented in this paper include foil surface static and dynamic pressures, foil vibration, LDV-determined average flow speeds and turbulence quantities, and PIV flow fields in the immediate vicinity of the foil’s trailing edge.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114431259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23536
T. Wood, S. Grace
The boundary element method provides a low-order computational model for investigating unsteady wing response. This method is applied here to investigate the effect of fixed wing geometry on the blade-vortex interaction (BVI) problem. The method has been validated using a harmonic Sears gust as well as three-dimensional BVI analytical results for thin, flat, rectangular wings. It is shown that wing taper and twist do not significantly affect the BVI response while sweep greatly reduces it.
{"title":"Wing Geometry Effect on Blade-Vortex Interaction Response Using BEM","authors":"T. Wood, S. Grace","doi":"10.1115/imece2001/nca-23536","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23536","url":null,"abstract":"\u0000 The boundary element method provides a low-order computational model for investigating unsteady wing response. This method is applied here to investigate the effect of fixed wing geometry on the blade-vortex interaction (BVI) problem. The method has been validated using a harmonic Sears gust as well as three-dimensional BVI analytical results for thin, flat, rectangular wings. It is shown that wing taper and twist do not significantly affect the BVI response while sweep greatly reduces it.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117195630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23512
S. Raveendra, S. Sureshkumar
A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of multiple, incoherent noise sources from measured sound pressure fields are described. Initially, a partial coherence approach is adopted to decouple an incoherent acoustic field into a set of fully coherent, mutually incoherent partial fields. Subsequently, NAH is applied individually to each coherent partial field to reconstruct the corresponding source field. A boundary element based NAH reconstruction procedure is utilized so that the technique is valid for arbitrary source geometry. The process is validated by identifying the sources in a two-speaker system that was driven by independent signal generators.
{"title":"Identification of Incoherent Noise Sources","authors":"S. Raveendra, S. Sureshkumar","doi":"10.1115/imece2001/nca-23512","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23512","url":null,"abstract":"\u0000 A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of multiple, incoherent noise sources from measured sound pressure fields are described. Initially, a partial coherence approach is adopted to decouple an incoherent acoustic field into a set of fully coherent, mutually incoherent partial fields. Subsequently, NAH is applied individually to each coherent partial field to reconstruct the corresponding source field. A boundary element based NAH reconstruction procedure is utilized so that the technique is valid for arbitrary source geometry. The process is validated by identifying the sources in a two-speaker system that was driven by independent signal generators.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"385 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133450262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23506
M. Conti, A. Stokes, C. Corrado
We present recently developed experimental methods of estimating acoustic scattering matrix representations of piping components such as valves and bends. Scattering matrices quantify the frequency dependent reflection and transmission coefficients for a wave incident on a device, and include terms representing the conversion of energy from one wave type to another. Scattering matrix representations of individual components can be embedded in a transmission line model to numerically assess acoustic transmission through a full piping system. This paper addresses both the experiment design and signal processing algorithms required to measure the scattering matrix.
{"title":"Array-Based Methods of Characterizing Piping Component Acoustic Behavior","authors":"M. Conti, A. Stokes, C. Corrado","doi":"10.1115/imece2001/nca-23506","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23506","url":null,"abstract":"\u0000 We present recently developed experimental methods of estimating acoustic scattering matrix representations of piping components such as valves and bends. Scattering matrices quantify the frequency dependent reflection and transmission coefficients for a wave incident on a device, and include terms representing the conversion of energy from one wave type to another. Scattering matrix representations of individual components can be embedded in a transmission line model to numerically assess acoustic transmission through a full piping system. This paper addresses both the experiment design and signal processing algorithms required to measure the scattering matrix.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115166724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23520
L. Mongeau, A. Alexander, B. Minner, I. Paek, J. Braun
Experimental investigations of an electro-dynamically thermoacoustic cooler prototype were performed. The prototype was designed to provide 140 W of cooling across a 22 °C temperature lift. Operation using a 55% helium-argon mixture at a mean pressure of 20 bar and a frequency near 180 Hz was targeted. The prototype used a tuned “moving magnet” electro-mechanical actuator. Initial investigations aimed at characterizing the electro-mechanical behavior and performance of the driver. The acoustic response of the system with no cooling elements was then investigated to validate the experimental procedures. The thermal performance of the complete system was then measured over a range of operating conditions, for varying gas mixtures. Detailed sound pressure and temperature measurements provided information from which the overall efficiency, capacity, and temperature lift of the cooling system were estimated, in addition to the heat exchange coefficients and performance of the heat exchangers. Net acoustic power inputs of up to 120 W were achieved with an electro-acoustic transduction efficiency varying between 20% and 50%, reaching values as high as 60% in a few cases. In comparison, the theoretical maximum driver efficiency was 65%. The measured cooling capacity varied greatly and peaked near 130 W for a temperature lift of 12°C. The acoustic pressure amplitudes were near 3% of the mean pressure in the stack region, and the heat rejected to a secondary fluid reached 250 W. The best relative coefficient of performance achieved was less than 3% of Carnot, based on the net input acoustic power. The best overall efficiency achieved was thus 1.2% of Carnot. While the acoustic power level exceeded the target value for the desired cooling load, the cooling power was well below the expected value, and the target temperature lifts and efficiencies were not achieved. This was generally attributed to “nuisance” heat loads, acoustic streaming effects, and migration of species within the inhomogeneous mixture. The non-dimensional heat exchanger performance in the thermoacoustic system was found to be slightly less than that in a steady uniform flow when the root-mean-square particle velocity is used for a velocity scale, and the stack end temperature is used in the calculation of the temperature lift. It was also found that this performance value is significantly better than that predicted by linearized boundary layer models often used in linear acoustic models.
{"title":"Experimental Investigations of an Electro-Dynamically Driven Thermoacoustic Cooler","authors":"L. Mongeau, A. Alexander, B. Minner, I. Paek, J. Braun","doi":"10.1115/imece2001/nca-23520","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23520","url":null,"abstract":"\u0000 Experimental investigations of an electro-dynamically thermoacoustic cooler prototype were performed. The prototype was designed to provide 140 W of cooling across a 22 °C temperature lift. Operation using a 55% helium-argon mixture at a mean pressure of 20 bar and a frequency near 180 Hz was targeted. The prototype used a tuned “moving magnet” electro-mechanical actuator. Initial investigations aimed at characterizing the electro-mechanical behavior and performance of the driver. The acoustic response of the system with no cooling elements was then investigated to validate the experimental procedures. The thermal performance of the complete system was then measured over a range of operating conditions, for varying gas mixtures. Detailed sound pressure and temperature measurements provided information from which the overall efficiency, capacity, and temperature lift of the cooling system were estimated, in addition to the heat exchange coefficients and performance of the heat exchangers. Net acoustic power inputs of up to 120 W were achieved with an electro-acoustic transduction efficiency varying between 20% and 50%, reaching values as high as 60% in a few cases. In comparison, the theoretical maximum driver efficiency was 65%. The measured cooling capacity varied greatly and peaked near 130 W for a temperature lift of 12°C. The acoustic pressure amplitudes were near 3% of the mean pressure in the stack region, and the heat rejected to a secondary fluid reached 250 W. The best relative coefficient of performance achieved was less than 3% of Carnot, based on the net input acoustic power. The best overall efficiency achieved was thus 1.2% of Carnot. While the acoustic power level exceeded the target value for the desired cooling load, the cooling power was well below the expected value, and the target temperature lifts and efficiencies were not achieved. This was generally attributed to “nuisance” heat loads, acoustic streaming effects, and migration of species within the inhomogeneous mixture. The non-dimensional heat exchanger performance in the thermoacoustic system was found to be slightly less than that in a steady uniform flow when the root-mean-square particle velocity is used for a velocity scale, and the stack end temperature is used in the calculation of the temperature lift. It was also found that this performance value is significantly better than that predicted by linearized boundary layer models often used in linear acoustic models.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":"214 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122617687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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