Explanations on the onset and damping behaviors in a standing-wave thermoacoustic engine

In order to understand the onset and damping behaviors of the thermoacoustic engine, a series of experiments and a simplified thermodynamics analysis are carried out. It is found that both the efficiency and the acoustic power of the gas increase with the increase of the gas-stack heat transfer coefficient, the gas displacement amplitude and the heating difference. Before onset, since the gas-stack heat transfer coefficient of natural convection and the amplitude of the gas are very low, a higher temperature difference is required to produce enough acoustic power to overcome the thermal and viscous dissipation and to excite oscillation. In the damping process, the gas-stack heat transfer coefficient and the amplitude of the gas are much higher because of the thermoacoustic oscillation. So a lower temperature difference is required to maintain the oscillation. In order to further verify this analysis, the experimental investigations are carried out at different tilted angles ranging from 90° to −90°. As the tilted angle decreases, the gas-stack heat transfer coefficient of the natural convection increases. The experimental results show that both the onset and damping temperature differences decrease with the decreasing of the tilted angle, which further confirms the above explanations.