Thermodynamic characteristics during the onset and damping processes in a looped thermoacoustic prime mover

Highlights: • Onset and damping processes in a looped travelling-wave thermoacoustic prime mover are studied. • Hysteretic loop due to the discrepancy of onset/damping temperature differences is discovered. • Inserting a compliance unit to the loop reduced the onset temperature difference by up to 223 K. - Abstract: The onset and damping processes of self-excited working-fluid oscillation in thermoacoustic prime movers, related to the quality of the utilizable thermal energy, have attracted everlasting research interest and effort. This work is intended to observe and analyze the temperature and pressure characteristics of the onset and damping processes in a recently developed looped travelling-wave thermoacoustic prime mover with enlarged thermoacoustic cores. A hysteretic loop, caused by the discrepancy between the onset temperature difference and the damping temperature difference, can be found in the looped structure, which indicates the potential in decreasing the onset temperature difference. Additionally, in order to optimize the acoustic field in the thermoacoustic prime mover, a compliance unit was inserted into the loop. The experimental results show that the onset temperature difference drops by up to 223 K with the appropriately located compliance unit, which is advantageous to the utilization of low-grade thermal energy.