Phase tuning mechanism in a thermoacoustic Stirling engine

When a steep temperature gradient is imposed on a regenerator contained in a looped tube by using two heat exchangers, acoustic waves are spontaneously generated as a result of the thermoacoustic energy conversions through the Stirling cycle. While the energy conversion in a conventional Stirling engine is performed by the carefully tuned pistons, a thermoacoustic Stirling engine does not have any mechanical parts to tune the acoustic wave responsible for the energy conversion. Thus, it is of great importance to study how the thermoacoustic engines perform energy conversions without moving parts. In this experiment, we focused on the phase angle between the pressure and velocity oscillations of gas parcels in a looped tube thermoacoustic engine. We demonstrate that the phase angle changes corresponding to the energy conversion process within the regenerator.