Gas-liquid thermoacoustic engine, using gas as working fluid and liquid as phase-matching element, can operate at a lower heat source temperature than the gas-only thermoacoustic engine, which is attractive for low-grade heat recovery. Rayleigh-Taylor instability, which is induced when a low-density fluid accelerates a high-density fluid, can occur in gas-liquid thermoacoustic engine. In this work, cylindrical or spherical floats with different dimensions were employed to suppress the Rayleigh-Taylor instability in a gas-liquid standing-wave thermoacoustic engine. Comparison between the onset and damping temperature differences obtained from the conditions with or without float was conducted to analyze the effects of instability on the onset and damping processes. The experimental results show that the dimension of float has marked effects on the onset and damping temperature differences, and there exists an optimal dimension for both cylindrical and spherical floats to achieve the lowest onset and damping temperature differences. After installing the float, the maximum decreases in the onset and damping temperature differences are 19.0% and 21.8%, respectively. This work demonstrates that the suppression of Rayleigh- Taylor instability by the suitably sized float can reduce the onset and damping temperature differences of a gas-liquid standing-wave thermoacoustic engine for low-grade heat recovery.
Keywords gas-liquid thermoacoustic engine, low-grade heat, Rayleigh-Taylor instability, float, onset and damping temperature differences