Open-air traveling-wave thermoacoustic generator

Abstract

Taking the input and reflected waves into account, the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed. Closed and open acoustic configurations that influence the pressure, volumetric velocity, impedance and acoustic work were compared in detail. Based on the above investigation, an open-air traveling-wave thermoacoustic generator was designed and fabricated. It is composed of a looped tube, a resonator open at one end, a regenerator, and hot and cold heat exchangers. It is a small scale and simple configuration. The resonant frequency is 74 Hz at 1 bar in air. The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20 μPa when the heating power was 210 W, respectively. Acoustic pressure is reasonable for practical application as a low-frequency acoustic source. In further work, we believe that the acoustic pressure at the open end can achieve 150 dB, which could be a solution to problems in existing acoustic generators. These problems include low acoustic pressure and system complexity. It can be used as a basic acoustic source for low frequency and long-range noise experiments, and as a supply for high acoustic pressures necessary for industrial sources. open-air, traveling-wave, thermoacoustic generator Citation:Xie X J, Gao G, Zhou G, et al. Open-air traveling-wave thermoacoustic generator. Chinese Sci Bull, 2011Bull, , 56: 2167Bull, −2173Bull, , doi: 10.1007 The thermoacoustic principle [1] is a thermodynamic effect that occurs between compressible gases (the first medium) and solids (the second medium) in an acoustic field. It results in a time-averaged heat flow and a time-averaged work flow along (against) the sound propagation direction at penetration depths that are far from the solid boundaries. The conversion of heat to work is called thermal to acoustic effect, and the opposing process is called the acoustic to thermal effect. Based on these two effects, thermoacoustic systems can be classified as thermoacoustic engines and thermoacoustic refrigerators. A regenerator in an acoustic field can bring standing-waves [2,3], traveling-waves [4][5][6] and standing-traveling waves [7,8] into being. In the latest two decades, engineering applications in thermoacoustic refrigeration and thermoacoustic electricity have been rapidly developed. In 1990, thermoacoustic engines first re-

Stirling cycle engines for recovering low and moderate temperature heat: A review

“…The engine was capable of converting thermal energy into acoustic power with an efficiency of 30%, corresponding to 41% of Carnot efficiency. The demonstrated great features of lacking hot moving parts and potentially high efficiency of thermoacoustic Stirling engines have attracted worldwide interest into the field since then [53][54][55][56][57][58][59][60][61][62]. Up to now, thermoacoustic Stirling engines have achieved the highest efficiency up to 49% of Carnot efficiency [63] and acoustic power up to tens of kilowatts [55].…”

Investigation on acoustic radiation characteristics of an open-air traveling-wave thermoacoustic generator

“…The theoretical model of OTTAG [3] is composed of a looped tube and an open resonator, shown in Fig.1. There are a regenerator, a cold heat exchanger, a hot heat exchanger, a thermal buffer tube and a secondary cold heat exchanger along the looped tube.…”

“…The resonator is a stainless-steel duct, the shapes of which had tremendous effect on the external acoustic field radiated from the thermoacoustic generator. Eight pressure sensors P1~P8 were distributed along the system to measure the oscillating pressure, which described in detail in Ref [3]. A B&K microphone P9 with high sensitivity is used to acquire SPL directly 1m far away from the output of the open resonator.…”

“…With the development of open-air thermoacoustic generator [2][3][4], another thermoacoustic application is foreseen as a low-frequency acoustic source. In 2010, Slaton [2] has constructed an open air standing-wave thermoacoustic system, which acquire the maximum acoustic pressure radiated from the open end of the resonator corresponds to 81 dB-SPL ref μPa at an input electric power of 276 W. He has expected that a higher power version of this kind of device may be used as a continuous source of low frequency.…”

“…In 2010, Slaton [2] has constructed an open air standing-wave thermoacoustic system, which acquire the maximum acoustic pressure radiated from the open end of the resonator corresponds to 81 dB-SPL ref μPa at an input electric power of 276 W. He has expected that a higher power version of this kind of device may be used as a continuous source of low frequency. I n 2011, Xie et al [3][4] has built up an Open-air Traveling-wave ThermoAcoustic Generator (OTTAG). Based on the simulations and experiments, the dimensions of regenerator and resonator influence on the resonant frequency, driver ratio, acoustic power and temperature difference have been optimized to acquire the perfect performance.…”