Acoustic characteristics of bi-directional turbines for thermoacoustic generators
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RESEARCH ARTICLE
Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO
Acoustic characteristics of bi-directional turbines for thermoacoustic generators
© Higher Education Press 2020
Abstract Bi-directional turbines combined with rotary motors may be a feasible option for developing high power thermoacoustic generators with low cost. A general expression for the acoustic characteristics of the bidirectional turbine was proposed based on theoretical derivation, which was validated by computational fluid dynamics modeling of an impulse turbine with fixed guide vanes. The structure of the turbine was optimized primarily using steady flow with an efficiency of near 70% (the shaft power divided by the total energy consumed by the turbine). The turbine in the oscillating flow was treated in a lumped-parameter model to extract the acoustic impedance characteristics from the simulation results. The key acoustic impedance characteristic of the turbine was the resistance and inertance due to complex flow condition in the turbine, whereas the capacitance was treated as an adiabatic case because of the large-scale flow channel relative to the heat penetration depth. Correlations for the impedance were obtained from both theoretical predictions and numerical fittings. The good fit of the correlations shows that these characteristics are valid for describing the bi-directional turbine, providing the basis for optimization of the coupling between the thermoacoustic engine and the turbine using quasi-one-dimensional theory in the frequency domain. Keywords thermoacoustic power generator, acoustic characteristics, bi-directional impulse turbine, energy conversion Received Jan. 8, 2020; accepted May 15, 2020; online Oct. 20, 2020
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Dongdong LIU ( ) University of Chinese Academy of Sciences, Beijing 101408, China; Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China E-mail: [email protected]
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Yanyan CHEN ( ), Wei DAI, Ercang LUO Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China E-mail: [email protected]
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Introduction
Nowadays, due to environment and energy crisis, it is an urgent task to explore a green and economic energy technology. The thermoacoustic power generation technology provides a good solution for this problem because it has the advantage of providing an environmentally friendly working medium with high reliability, and can recover low-grade heat. During the last three decades, numerous research studies have shown great potential for thermoacoustic heat engine (TAHE) in refrigeration and electricity generation [1–5]. The thermoacoustic electrical generator (TAEG) is composed of a TAHE and an acoustic-to-electric converter, which are acoustically coupled. During the operation of the TAEG, the heat energy is converted, through the TAEG, into acoustic power which is then used by the acoustic-to-electric conversion device for power generation [6–8]. To date, the acoustic-to-electric converters that have been reported for
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