Performance of a three-stage travelling-wave thermoacoustic engine utilizing low-grade heat

Thermoacoustic technology is capable of converting thermal energy into usable energy with the advantages of simple structure, high reliability, and low costs due to the absence of mechanical moving parts. And multi-stage travelling-wave thermoacoustic devices have high potential in recovering low-grade heat source into usable energy which can contribute to ease the energy shortage. In this work, a three-stage travelling-wave thermoacoustic engine has been proposed and studied numerically and experimentally. In the experiment, at the mean pressure of 3.0 MPa and the temperature difference between the hot and cold end of the regenerator of about 285 K, the working frequency is about 20 Hz, the onset temperature difference is 55 K, the pressure amplitude is 278.0 kPa, and the pressure ratio can achieve 1.19, when the working gas is nitrogen; meanwhile, the working frequency is about 55 Hz, the onset temperature difference is 71 K, the pressure amplitude is 194.3 kPa, and the pressure ration can achieve 1.13, when the working gas is helium. Furthermore, an electric generator driven by the three-stage traveling-wave thermoacoustic engine with helium as the working gas was modelled by DeltaEC. And the conversion from low-grade heat to electric energy is verified. A maximum electric power of 1427.2 W and a highest thermal-to-electric efficiency of 10.7% are obtained numerically when the mean pressure is 3.0 MPa and the heating temperature is 623 K.