Theoretical And Experimental Study Of A Traveling-wave Thermoacoustic Engine

Thermoacoustic effect is the phenomenon of the conversion between thermal energy and acoustic power. Thermoacoustic engine is a kind of machine, which converts thermal energy into acoustic power by thermoacoustic effect. It is a new way of thinking to drive a pulse-tube refrigerator or other thermoacoustic refrigerators by using thermoacoustic engines instead of mechanical compressors so as to completely eliminate moving parts of refrigeration system for more reliable operation. Ceperley first proposed the idea of traveling-wave thermoacoustic heat engine in 1979 and it was practically realized by Swift in 1999. Because the thermoacoustic conversion process that occurs in its regenerator is reversible and velocity is in phase with pressure, traveling-wave thermoacoustic engine can produce and transmit acoustic power with higher efficiency theoretically.After a detailed review on the developments of the research on thermoacoustics, as well as the latest advancements in this field, prospective applications, and a survey of theoretical fundamentals, the author's work focuses on the following sections:According to predecessors' explanations, as well as personal understanding on thermoacoustic effects, a qualitative explanation for the operating mechanism of thermoacoustic engines from thermodynamic viewpoint is presented.After the analysis of feasibility, a large-scale multi-function thermoacoustic-stirling heat engine has been designed and constructed. With the length and height of 4.5meters and 1.25 meters, respectively, the engine is designed to have the maximal input power of 5,000W. It can operate in traveling wave mode with only the torus in experiment, as well as in hybrid mode of standing wave and traveling wave with the whole engine working, and it can be also used to drive a pulse-tube refrigerator. In comparison with standing-wave heat engine, it has lower onset temperature and higher pressure ratio, which is of great significance for introducing a variety of energies of low quality into thermoacoustic engines, such as solar energy, waste vapor energy and so on. With the filling nitrogen of 0.9 MPa, the maximal pressure ratio reaches 1.21 and the operation frequency is 25 Hz, which is a rather good result in this field.