Investigation On Output Characteristics Of A Thermoacoustic Stirling Engine Loaded With Linear Alternator

A thermoacoustic engine (TE) is a novel heat engine which converts thermal energy into acoustic power via the thermoacoustic effects. With advantages such as having no moving parts, no pollution, and its use of low-grade thermal energy, the TE has a promising prospect in the field of natural gas liquefaction, electronic cooling, air separation and power generation. The study on the output characteristics of a thermoacoustic engine is of importance for the match of the engine and loads to improve the whole efficiency of thermoacoustic engine connected with loads. To further investigate the output characteristics of thermoacoustic engine, theoretical and experimental reserches have been performed as follows:(1) Based on electro-mechanical-acoustic analogy, a simplified physical model of linear alternator has been built. The energy conversion from acoustic to electrical power has been analyzed. The simulation model on thermoacoustic engine connected with linear alternator loads based on linear thermoacoustic theory also has been built.(2) Alternator, thermoacoustic engine connected with an RC (resistance and capacitance) load, thermoacoustic engine connected with an alternator have been numerically simulated with linear thermoacoustics theory. According to the computed results, the effect of the frequency, load, inlet pressure amplitude, piston area on the performance and impedance of alternator have been discussed; with helium as working gas, the impedance ranges corresponding to the best output characteristics of engine has been obtained; the effect of the working gas, load, mean pressure and heating power on the performance of the engine connected with alternator have been analyzed. The coupling relation of the thermoacoustic engine and linear alternator load has been discussed.(3) Preliminary coupling experiments with nitrogen and helium were conducted. The experimental results show the transfer tube between the engine and the alternator load will improve the output characteristics. With2.1MPa helium,140W output electrical power was obtained. The experiment results agree well with the calculation. Further, from the perspectives of impedance match and improvement of acoustic-electrical efficiency, the optimization has been calculated. After optimization248W electrical power can be generated as well as the thermo-acoustic efficiency of15.2%and thermo-electrical efficiency of11.1%with2.1MPa helium, heating temperature of650℃and160Ω. resistance load.