Analysis and performance of a large thermoacoustic engine

Abstract

Measurements and analysis of a 13-cm-diam thermoacoustic engine are presented. At its most powerful operating point, using 13.8-bar helium, the engine delivered 630 W to an external acoustic load, converting heat to delivered acoustic power with an efficiency of 9%. At low acoustic amplitudes, where (linear) thermoacoustic theory is expected to apply, measurements of temperature difference and frequency agree with the predictions of theory to within 4%, over conditions spanning factors of 4 in mean pressure, 10 in pressure amplitude, 6 in frequency, and 3 in gas sound speeds. But measurements of the square of pressure amplitude versus heater power differ from the predictions of theory by 20%, twice the estimated uncertainty in the results. At higher pressure amplitudes (up to 16% of the mean pressure), even more significant deviation from existing thermoacoustic theory is observed. Several causes of this amplitude-dependent deviation are identified, including resonance-enhanced harmonic content in the acoustic wave, and a new, first-order temperature defect in thermoacoustic heat exchangers. These causes explain some, but not all, of the amplitude-dependent deviation of the high-amplitude measurements from existing (linear) theory.

Linear and nonlinear modelling of a theoretical travelling-wave thermoacoustic heat engine

“…Issues addressed include the onset of instability, thermoacoustic heating, transport due to acoustic nonlinearities and effects of variable cross-sectional area. Later, Swift and co-workers used Rott's work as the basis for the development of semi-empirical low-order models for the acoustics in various components found in real thermoacoustic engines (Swift 1988(Swift , 1992Swift & Ward 1996). This resulted in the development of the prediction software package DeltaE (Ward & Swift 1994) (replaced now by DeltaEC), which, together with similar modeling tools such as SAGE and REGEN, is still actively used in the academic literature as well as in industry.…”

Thermal performance of finned-tube thermoacoustic heat exchangers in oscillatory flow conditions

“…In this section, the experimental results are compared with other physical models, such as the RMSRe model, the TASFE model [23], the boundary layer conduction model [24,25], the model integrating the Valensi number (Va) [13,26], and some of their variations.…”

Numerical Study of Entropy Generation Within Thermoacoustic Heat Exchangers with Plane Fins

“…Entropy 2015, 17, [1][2][3][4][5][6][7][8][9][10][11] shown in Figure 1. The system is supposed to work in the refrigeration mode so heat is pumped from the cold to the hot HX through the stack along the positive longitudinal x direction (see Figure 1).…”

“…A typical thermoacoustic device consists of: (a) an acoustic network (acoustic resonator), (b) an electro-acoustic transducer, (c) a porous solid medium (namely a regenerator in travelling-wave systems [3] or a stack in standing-wave systems [4]) and (d) at least a pair of heat exchangers (HXs) [5]. The stack/regenerator is the component where the desired heat/sound energy conversion takes place.…”