Critical temperature of traveling- and standing-wave thermoacoustic engines using a wet regenerator

Tsuda, Katsutoshi; Ueda, Yuichi

doi:10.1016/j.apenergy.2017.04.004

Cited by 41 publications

(20 citation statements)

References 25 publications

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“…In the calculations we demonstrated how modifying a gas mixture to contain a reactive gas, able to exchange mass with a sorbent layer, decreases the temperature difference required to trigger an instability in thermoacoustic systems. These findings are in good agreement with experimental results obtained for an air-water mixture (Tsuda & Ueda 2017).…”

Section: Discussionsupporting

confidence: 92%

“…The results of conduction-driven thermoacoustics are obtained by setting C m ≡ 0, reducing the equations to the known form of 'classical' thermoacoustics (Rott 1969). The experimental results, reported by Tsuda & Ueda (2017), show good agreement with the theoretical curves. In these experiments the working fluid comprises air and water vapour that evaporate/condense on the stack solid walls, matching the simple case of phase change derived by Raspet et al (2002), which in our model corresponds to η n = 1 (see § 2.1).…”

Section: Stability Analysismentioning

confidence: 80%

“…A substantial decrease in the onset temperature difference was measured by Tsuda & Ueda (2015 for thermoacoustic systems employing an air-water vapour gas mixture, with the latter presenting experimental results of three different system geometries corresponding to standing wave, travelling wave and a combination of the two. Tsuda & Ueda (2017) also measured the increase in pressure amplitude following onset of pressure oscillations in their systems. However, it appears that due to insufficient internal circulation of the finite volume of water in these closed systems, these oscillations could not maintain a limit cycle and naturally shut down shortly after the stability limit was exceeded.…”

Section: Introductionmentioning

confidence: 99%

“…The mean pressure is p m = 1 bar, the stack cold-side temperature is T c = 23 • C, and scaled stack length and location are L s /L = 0.026 and L 0 /L = 0.84, respectively. Experimental results, marked by filled dots, are taken fromTsuda & Ueda (2017).…”

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confidence: 99%

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Acoustic oscillations driven by boundary mass exchange

et al. 2019

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Thermoacoustic instability – self-sustained pressure oscillations triggered by temperature gradients – has become an increasingly studied topic in the context of energy conversion. Generally, the process relies on conductive heat transfer between a solid and the fluid in which the generated pressure oscillations are sustained. In the present study, the thermoacoustic theory is extended to include mass transfer; specifically, the working fluid is modified so as to incorporate a ‘reactive’ gas, able to exchange phase with a solid/liquid boundary through a sorption process (or through evaporation/condensation), such that most heat is transferred in the form of latent heat rather than through conduction. A set of differential equations is derived, accounting for phase-exchange heat and mass transfer, and de-coupled via a small-amplitude asymptotic expansion. These equations are solved and subsequently manipulated into the form of a wave equation, representing the small perturbation on the pressure field, and used to derive expressions for the time-averaged, second-order heat and mass fluxes. A stability analysis is performed on the wave equation, from which the marginal stability curve is calculated in terms of the temperature difference, $\unicode[STIX]{x0394}T_{onset}$, required for initiation of self-sustained oscillations. Calculated stability curves are compared with published experimental results, showing good agreement. Effects of gas mixture composition are studied, indicating that a lower heat capacity of the inert component, combined with a low boiling temperature and high latent heat of the reactive component substantially lower $\unicode[STIX]{x0394}T_{onset}$. Furthermore, an increase in the average mole fraction of the reactive gas, $C_{m}$ strongly affects onset conditions, leading to $\unicode[STIX]{x0394}T_{onset}\sim 5\,^{\circ }\text{C}$ at the highest value of $C_{m}$ achievable under atmospheric pressure. An analysis of the system limit cycle is performed for a wide range of parameters, indicating a systematic decrease in the temperature difference capable of sustaining the limit cycle, as well as a significant distortion of the acoustic wave form as the phase-exchange mechanism becomes dominant. These findings, combined, reveal the underlying mechanisms by which a phase-exchange engine may produce more acoustic power than its counterpart ‘classical’ thermoacoustic system, while its temperature difference is substantially lower.

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Section: Discussionsupporting

confidence: 92%

Section: Stability Analysismentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Acoustic oscillations driven by boundary mass exchange

et al. 2019

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“…Thermoacoustic engines (TAEs) are the acoustical equivalent of their conventional counterparts such as Stirling engines, but have no moving parts [1,2]. They use delicately designed acoustic network to force gas parcels within the thermoacoustic core (stack or regenerator) to experience engine cycles in thermodynamics, so that heat is converted to acoustic energy [3,4]. The acoustic energy produced within such engines can be further converted into electricity through transducers such as linear alternators, piezoelectric transducers, magnetohydrodynamic generators, bidirectional turbines [5].…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of thermally induced oscillatory flow in a thermoacoustic engine

et al. 2020

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In this paper, a comprehensive high-fidelity three-dimensional computational fluid dynamic research using large eddy simulation has been conducted to investigate a standing-wave quarter-wavelength thermoacoustic engine that consists of a hot buffer, a stack and a resonator. The performance of the thermoacoustic engine has been analysed in four aspects. Firstly, the dynamic characteristics of the engine during the initial start-up process are investigated when changing the temperature gradient imposed on the stack. Numerical results are compared with those from a system-wide reduced-order network model based on linear thermoacoustic theory. Secondly, the acoustic behaviour of the engine operating at steady state is studied. Fourier Series Model is utilized to decompose the steady-state acoustic pressure oscillations which reveals the unstable longitudinal acoustic modes excited in the engine. The stack serves as an energy source for the fundamental mode while it extracts acoustic power from the second harmonic. Thirdly, the hydrodynamic performances of the engine are inspected, and the obtained three-dimensional flow fields inside the engine enable us to probe into rich nonlinear phenomena including minor losses, mass streaming, etc. Finally, the heat transfer characteristics have been analysed by examining the mean temperature field and transversal heat fluxes along the engine. This research demonstrates that the large eddy simulation framework is effective in simulating the thermally induced oscillatory flow inside thermoacoustic engines. The multi-perspective analytical methodologies are valuable in comprehending the engine performance and provide guidelines for the design and optimization of efficient thermoacoustic engines for recovering waste thermal energy from various sources.

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Acoustic instability in aerosols

Offner

Ramon

2021

J Eng Math

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Critical temperature of traveling- and standing-wave thermoacoustic engines using a wet regenerator

Cited by 41 publications

References 25 publications

Acoustic oscillations driven by boundary mass exchange

Acoustic oscillations driven by boundary mass exchange

Large eddy simulation of thermally induced oscillatory flow in a thermoacoustic engine

Acoustic instability in aerosols

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