Study On The Performance Of Looped Thermoacoustic Generator Driven By Low-grade Heat Source

Thermoacoustic engine is a type of heat engine without moving parts,converting thermal energy into mechanical energy.It has been widely studied thanks to its outstanding merits of high reliability,long operating life and environmental friendliness.Thermoacoustic power generation is one of the important applications of this engine,and significant progresses have been made in the past years.However,the conversion efficiencies of such systems are usually lower than the traditional thermal engines,which seriously restrict the applications.Recent breakthrough in decreasing the onset temperature of thermoacoustic engine provides much space for its use of low-grade heat source.This work will focus on a looped travelling-wave thermoacoustic engine with variable stages to drive a linear generator.The main work is as follows.1.Based on thermoacoustics theory,the one-stage to four-stage looped travelling-wave thermoacoustic engine to drive a load in place of generator has been numerically simulated.In order to explore the coupling relationship of the thermoacoustic engine and the load,for obtaining the suitable range of the load impedance,the effects of load impedance,load location and operating frequency on the acoustic work and thermo-acoustic efficiency of the engine have been discussed.2.Based on acoustic-mechanical-electrical conversion analogy,a theoretical model of an oppoed-piston linear generator has been built and the functions of its acoustic-electrical efficiency,acoustic work and impedance have been deduced.Then,the looped thermoacoustic engine with variable stages to drive the linear generator has been numerically analyzed.In the calculation,the highest acoustic-electrical efficiency of 70%and the highest thermo-electrical efficiency of 5.1%can be achieved.3.An experimental system of variable-stage looped travelling-wave thermoacoustic engine to drive a linear generator has been built.The performance of the system operated with the working fluid of helium/argon mixture of 2.4MPa and the heating temperature below 200?has been studied.The lowest onset temperatures of 142?,82?,62? and 49? have been achieved in the experiments of one-,two-,three-and four-stage systems,respectively.In addition,the highest thermo-electrical efficiency with heating temperature of 3.50%@193?,3.14%@196? 3.90%@192? and 2.37%@155? corresponding to one-,two-,three-and four-stage system have been also obtained,which can verify the feasibility of using low-grade heat source in this thermoacoustic power generation system.