Theoretical and experimental investigation of acoustic field adjustment of a gas-liquid standing-wave thermoacoustic engine

Acoustic field is a crucial aspect for designing thermoacoustic engines, especially that in the stack where thermoacoustic effect occurs. The present work analyzes the acoustic field characteristics of a gas-liquid standingwave thermoacoustic engine, based on which the acoustic field in the stack is adjusted through suitable combination of buffer length and liquid column length. Calculation and experiments have been conducted on the system with different frequencies, working gases and charging pressures to verify the method of acoustic field adjustment. The onset and steady-state characteristics of the system with different acoustic fields in the stack are then experimentally studied. Compared with the lowest onset temperature difference up to 108 K in our previous experiments, the system can be initiated at a temperature difference of 53 K after adjusting the acoustic field in the stack, showing good applicability to recover low-grade heat. Furthermore, the acoustic field in the stack close to the pressure antinode is also found preferred to achieve large acoustic power and high efficiency. This work can be instructive for adjusting the acoustic field in the stack of gas-liquid standing-wave thermoacoustic engines.