Theoretical And Experimental Research For Characteristic Time Of Thermoacoustic Engine

Thermoacoustic engine is a new type heat engine, which is converting energy basedon thermoacoustic effect. Due to its various advantages，thermoacoustic engine has beenattracted much attention. In the research of thermoacoustic engine, various characteristicparameters are used to reflect energy transfer effect of thermoacoustic system byresearchers.Understanding and summarizing the development of thermoacoustic engine theoriesand researches comprehensively，and based on the Fractional Change, Scaling andAnalysis method (FCSA), the characteristic times of thermoacoustic system are calculated,optimized and analysed as characteristic parameters. And effects of characteristic times onthermoacoustic engine performance parameters were researched, which provide guidanceto the thermoacoustic theory researches and design works. And the experimental platformwas built to measure and analyze the characteristic time. According to those, the researchesfor characteristic times of thermoacoustic system were achieved through theory andexperiment.The main researches include the following sections:Firstly, the FCSA was introduced and analyzed, and the expressions of thecharacteristic time of thermoacoustic system were obtained. They were optimized andanalysed with some kinds of objective functions. Analyzing on ecological objectivefunction, for the thermoacoustic heat engine and refrigerator, with the characteristic time,the ecological function value increases firstly and then decreases. There is an optimalcharacteristic time to make the ecological objective function value maximum. And thetemperature gradient and value of x make an impact on function value. Analyzing onacoustic power, it is monotonically decreasing with characteristic times. Analyzing onefficiency, the thermoacoustic heat engine efficiency increases with characteristic time.Analyzing on refrigeration efficiency or the coefficient of performance, there is an optimalcharacteristic time to make them maximum.Secondly, as an example with standing-wave sound field, entropy production rate of thermoacoustic engine was calculated and analysed. The influence of factors, likecharacteristic time and temperature gradient, on entropy production rate were analysed. Forheat exchanger, the entropy production rate decreases with the characteristic times firstly,then increases; and for regenerator, the entropy production rate increases sharply with thecharacteristic times firstly, and then decreases sharply, then gently increases after aminimum point. There are optimal characteristic times to make irreversible entropyproduction minimum. And there are values of temperature gradient, plate spacing andimpedance ratio to make entropy production rate minimum.Thirdly, considering the effects of the heat leakage and internal irreversibility on thequality factor of thermoacoustic system, the quality factor was calculated from the view ofenergy. Quality factor increases monotonically with the characteristic time in some case ofenergy loss. The effect of heat leakage on the quality factor is larger than the effect of theirreversible factor. The quality factor is increased monotonically with the resonantfrequency and porous materials characteristic factor, and decreased monotonically withheat leakage conductivity, irreversibility factor andr0.Finally, the measurement method of thermoacoustic system characteristic time isanalysed. According to the experiments platform in laboratory, it is measured and theexperimental results are analysed.