Large eddy simulation of thermally induced oscillatory flow in a thermoacoustic engine. (15th October 2020)

• Record Type: Journal Article
• Authors: Chen, Geng; Wang, Yufan; Tang, Lihua; Wang, Kai; Yu, Zhibin
• Is Part Of: Applied energy. Volume 276(2020)
• Publication Date: 2020-10-15
• Subjects: Thermoacoustic engine -- Large eddy simulation -- Network model -- Minor losses -- Mass streaming; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2020.115458
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Large eddy simulation of a full-scale thermoacoustic engine (TAE) is conducted. A reduced-order network model is employed to predict the dynamic behavior. The stack serves as an acoustic energy sink for the second harmonic at steady state. Three-dimensional representations of vortex cores at the stack ends are displayed. Mean temperature field and transversal heat fluxes along the engine are examined. Abstract: 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.