Electro-acoustic-analogy Analysis And Experimental Study Of A Thermoacoustic Engine With Liquid-vapor Phase Change

A thermoacoustic engine, as a heat engine without moving parts, can convert heat into mechanical energy. Most of the existing thermoacoustic engines use single-phase working fluids, and have been well developed to achieve quite high efficiency and to show promising application potential. However, the single-phase thermoacoustic engines have much difficulty in utilizing the waste heat and miniaturizing the size. The present study tried to improve the performance of thermoacoustic engine by introducing the liquid-vapor phase change process into the thermoacoustic conversion. The features of liquid-vapor phase change were expected to improve the applicability of thermoacoustic engines in the low-grade heat source and to raise the energy density. The theoretical simulation and experiments have been conducted, mainly including the following aspects:1. Modification of an existing thermoacoustic engine with liquid-vapor phase change. Based on our previous study, a liquid-vapor phase change thermoacoustic engine, which had one end open to the surrounding, has been modified into a closed loop-type one by connecting the load tube to a reservoir. The closed system can be operated at an operation pressure higher than the atmospheric one, enhancing the acoustic oscillation, and then leading to a prospective higher power density.2. Electro-acoustic-analogy analysis of a closed-loop thermoacoustic engine with liquid-vapor phase change. Based on the electric-acoustic analogy theory, an electric circuit is proposed to analog the physical model of the closed-loop thermoacoustic engine with liquid-vapor phase change, which can then be used to indirectly calculate its thermophysical performance. The analysis was focused on the influence of the load liquid column, reservoir, feedback tube, power piston, adiabatic tube and working fluid on the operating frequency and onset temperature of the engine system.3. Experimental study of the closed-loop thermoacoustic engine with liquid-vapor phase change. An experimental apparatus of the closed-loop thermoacoustic engine with liquid-vapor phase change process has been built. The experimental study focused on observing the influence of the load liquid column length, distance between two heat exchangers, reservoir size, heating power and working fluids, and the operating frequency, onset temperature, pressure ratio and pressure amplitude are recorded for further analysis and discussion.