Efficiency of the Thermoacoustic Engine Induced by Stack Position, Pipe Aspect Ratio and Working Fluid

Alexandra Morvayovà, Alessandro Nobile, Myriam E. Bruno, Andrea Romano, Paolo Oresta () and Laura Fabbiano
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Alexandra Morvayovà: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy
Alessandro Nobile: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy
Myriam E. Bruno: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy
Andrea Romano: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy
Paolo Oresta: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy
Laura Fabbiano: Department of Mechanics, Mathematics and Management (DMMM), Polytechnic University of Bari, 70125 Bari, Italy

Energies, 2025, vol. 18, issue 18, 1-29

Abstract: This study investigates the performance of thermoacoustic engines by examining the influence of stack position, resonator length, and working fluid on energy conversion efficiency. Numerical simulations reveal that placing the stack at an intermediate location (e.g., 60 mm in a 350 mm resonator) maximises efficiency by promoting stable, single-mode harmonic oscillations and minimising boundary layer interference. Deviations from this optimal position (e.g., 30 mm or 90 mm) induce secondary harmonics, reducing efficiency. Doubling the resonator length while maintaining proportional stack scaling preserves performance, indicating aspect ratio is not a limiting factor. Simulations with helium, as opposed to air, yield a tripled resonance frequency (∼ 700 H z v s . 245 H z ) and significantly higher efficiency (∼ 0.38 vs . ∼ 0.13 ), due to helium’s superior thermal and acoustic properties. These results provide quantitative guidelines for optimising thermoacoustic engine design for sustainable energy applications.

Keywords: thermoacoustic engine; numerical simulation; heat transfer; acoustic wave; thermal energy efficiency (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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