Optimal thermoacoustic energy extraction via temporal phase control and traveling wave generation

Abstract

This work presents a novel class of thermoacoustic devices that comprises a simple resonator geometry and a control transducer to excite hybrid standing-traveling waves, thereby increasing the amount of extractable acoustic power in thermoacoustic energy converters. The onset gas oscillations in compact thermoacoustic resonators are predominantly standing waves, which exhibit a pressure-velocity time-phasing that is detrimental to the acoustic power output of conventional thermoacoustic systems. By employing open and closed-loop feedback control in a thermoacoustic energy converter with dual sensing and actuating piezoelectric transducers located at both ends of the resonator cavity, it is shown that the traveling wave portion of the resultant wave dynamics can be significantly increased at a relatively small cost of power pumped into the system. As a result, the controlled thermoacoustic system outperforms a conventional one of the same size and configuration by virtue of the increased acoustic power output. The new design also drastically improves the power density due to the lack of additional structural components typically needed to sustain traveling waves. Stability criteria are investigated, along with a standing wave ratio ellipsoidal fit analysis that gives both qualitative and quantitative measures of the energy converter’s behavior. The proposed thermoacoustic energy conversion mechanism presents a new methodology for increasing the energy generation capabilities of this class of energy harvesters.