Resonance mode control by superposing external sound on the sound in standing-wave type thermoacoustic system

The technique to control the resonance mode necessary for enhancing the energy conversion efficiency of thermoacoustic system is discussed. A standing-wave type thermoacoustic system is set in the condition that the self-excited vibration with 3/2 wavelength of the total tube length takes place by adjusting the position of the stack. The sound wave of the fundamental mode is then externally superposed on the sound wave excited in the system. As a result, the resonance of the system is shifted to the fundamental mode from the higher mode. Furthermore, the resonance control is supposed to be realized by the reason that thickness of the viscous boundary layer is reduced and that the self-excited vibration is enabled at the lower entropy generation comparing with the higher-mode resonance. These results suggest that the technique to use the superposing sound wave is valid for enhancing the energy conversion efficiency by the resonance control.