Acoustic field in a thermoacoustic Stirling engine having a looped tube and resonator

Abstract

S. Backhaus and G. W. Swift [Nature 399, 335(1999)] have built a prototype thermoacoustic Stirling engine based on traveling wave energy conversions, and demonstrated that its efficiency reached above 40% of the Carnot efficiency. We experimentally investigate an acoustic field in the engine through simultaneous measurements of velocity U and pressure P. By focusing on the phase lead Φ of U relative to P in its regenerator, we find that the engine can achieve such a high efficiency by the negative Φ about −20° rather than a traveling wave phase (Φ=0).