Numerical and experimental study of a looped travelling-wave thermoacoustic electric generator for low-grade heat recovery

Thermoacoustic technology has drawn increasing attention due to its advantages such as reliability and environmental benignity. Aiming at low-grade heat recovery, we developed a travelling-wave thermoacoustic electric generator consisting of a looped travelling-wave thermoacoustic engine and a linear alternator. In order to explore the operating characteristics of the electric generator, we numerically analyzed the acoustic field characteristics with a modified model. The analysis shows that high acoustic impedance appears in all three stages, and the travelling-wave component dominates the acoustic field of the loop, which is significant for both thermoacoustic conversion and acoustic power propagation. Furthermore, we also investigated the effects of external electric compliance, resistance, and hot end temperature on the output electric power, thermal-electric efficiency, and other related parameters. In the experiments, a thermal-electric efficiency of 3.7% with an output electric power of 24 W has been achieved, when the hot end temperature is 120 degrees C. The relative Carnot efficiency can exceed 14% when the hot end temperature is between 120 degrees C and 190 degrees C. The promising results demonstrate the significant potential of thermoacoustic electric generation in low-grade heat recovery.