Active control of thermoacoustic amplification in a thermo-acousto-electric engine

Abstract

In this paper, a new approach is proposed to control the operation of a thermoacoustic Stirling electricity generator. This control basically consists in adding an additional acoustic source to the device, connected through a feedback loop to a reference microphone, a phase-shifter, and an audio amplifier. Experiments are performed to characterize the impact of the feedback loop (and especially that of the controlled phase-shift) on the overall efficiency of the thermal to electric energy conversion performed by the engine. It is demonstrated that this external forcing of thermoacoustic self-sustained oscillations strongly impacts the performance of the engine, and that it is possible under some circumstances to improve the efficiency of the thermo-electric transduction, compared to the one reached without active control. Applicability and further directions of investigation are also discussed. V C 2014 AIP Publishing LLC. [http://dx.

Hysteretic behavior induced by an electroacoustic feedback loop in a thermo-acousto-electric generator

“…[31] and therefore only a brief description will be provided here. to the previous study [31] lies in the acoustic source position: it is located inside the loop-tube, whereas it was enclosed in a small cavity and coupled to the loop guide via a capillary tube in the previous study. It is placed just above the main ambient heat exchanger at a high acoustic impedance position (i.e.…”

“…In particular, a proof-of-concept study provided by Desjouy et al [28] in an annular engine has demonstrated that the addition of two auxiliary sources, appropriately tuned, can significantly improve the overall efficiency. More recently, Olivier et al [31] successfully applied an active control method to the TAEG considered in this paper.…”

“…Some studies have focused on the description of the variety of nonlinear dynamics behavior observed in experiments (synchronization [24,25], route to chaos [26],...). Other studies [27,28,29,30,31] have focused on the forcing of acoustic oscillations in the context of thermoacoustic engines. In particular, a proof-of-concept study provided by Desjouy et al [28] in an annular engine has demonstrated that the addition of two auxiliary sources, appropriately tuned, can significantly improve the overall efficiency.…”

Beating effect between a thermoacoustic source and its mechanical partner

“…In recent years, great efforts have been made to take advantages of thermoacoustic effects for converting heat into mechanical power by thermoacoustic engines. [1][2][3][4][5][6][7] Simple acoustic networks formed by several pipes rather than reciprocating mechanical pistons are adopted in thermoacoustic engines.…”

Theoretical study of a thermo-acousto-electric generator equipped with an electroacoustic feedback loop

“…In this study, we use a simplified modeling of thermoacoustic engines to help understanding recent experimental observations dealing with the external forcing of thermoacoustic oscillations [3,4,5]. Indeed, at the present time the multiplicity of the involved nonlinear effects and their complexity does not allow to understand why and how the mechanisms at stake in this process of active control enable to increase the global efficiency of the thermoacoustic engine.…”