Experimental investigation on the dynamic behavior of a standing-wave thermoacoustic engine subjected to low-frequency axial oscillatory motion

In recent years, active control of thermoacoustic engines (TAEs) has emerged as a significant research topic, driven by the need to modulate the acoustic field and achieve better thermal performance. Motivated by previous numerical studies on Rijke tubes, this work systematically investigates the influence of axial oscillatory motion on the dynamic behavior of a standing-wave TAE. A linear actuator is employed to realize the axial oscillatory motion of the TAE. Comparative studies on the effects of acoustic boundary conditions (fully-closed versus partially-closed left end), as well as the start-up timing and magnitude of the imposed oscillatory motion, on TAE performance are conducted. Results show that the TAE with a partially-closed left end (orifice plus short tube) can still produce self-excited acoustic oscillations. The axial oscillatory motion modulates the pressure oscillations inside the thermally-driven TAE, leading to quasi-periodic or beating oscillations. The maximum pressure of the TAE subjected to axial oscillatory motion is higher than that under the stationary condition. A lower rotation speed and a larger stroke of the linear actuator contribute to higher pressure amplitude, more pronounced beating effect, and longer beating periods. This study fulfills the research gap of previously unexplored complex interplay between axial oscillatory motion and self-excited acoustic oscillations in TAEs, and provides important guidance for studying the various nonlinear phenomena in thermoacoustic devices.