Analysis And Experimental Research Of Effect To Load On The Output Characteristics Of Thermoacoustic Electric Generation System

As the promising thermal-electric conversion device,thermoacoustic electric generation technology can convert solar energy,industrial waste heat,automobile exhaust and other low-quality heat into electric energy,which features good heat adaptability,no-polluted operating gas,high efficiency,no moving parts and long service life.And the characteristics of thermoacoustic electric generation system(TAEGS)are researched by domestic and foreign experts worldwide.The TAEGS is mainly composed of low-quality heat source,thermoacoustic engine,linear generator and external electric load.It is of high priority to study the effect of the load on the output acoustic characteristics and electrical characteristics of TAEGS,which is of significance to improve the efficiency.In this thesis,the acoustic resonance characteristics and electrical resonance characteristics of the thermoacoustic linear electric generation system is focused on,the researches of this thesis mainly are:Firstly,according to the operating principle of the TAEGS,the acoustic-mechano-electro analog model of the linear generator is established.Then,the input acoustic power,the output electrical power,the acoustic-electric efficiency,the displacement of the primary and the output current of the primary winding are derived.And the influential coefficients of the load on the acoustic and electrical characteristics of the thermoacoustic electric generation system are analyzed.Secondly,based on the linear thermoacoustic theory,the numerical simulation analysis of the TAEGS is carried out.The influence of the operating frequency,external electric load,inlet pressure amplitude,mechanical spring coefficient and piston area on the output characteristics and impedance distribution of the TAEGS are analyzed and discussed.Considering that low-quality heat source constitutes the source energy of thermoacoustic engine,the frequency of the acoustic driving force can not be kept in constant,therefore,the direct current control,instead of the external load capacitance,is employed in Matlab/simulink to design the PWM rectifier circuit to obtain the unit power factor,which assures that the output current and voltage of linear generator in-phase,so as to improve the output characteristics of thermoacoustic electric generation system.The influence of variable external load resistance,driving spring frequency,spring coefficient and piston area on the output characteristics ofTAEGS is analyzed combined with Matlab/simulink.Finally,through the experimental platform of thermoacoustic electric generation system,the spring coefficient is chosen at 3.248×105N/m to ensure linear generator oscillating at the acoustic resonance state.The electrical resonance status of TAEGS is realized through external load capacitance and PWM rectifier circuit.The influence of the average pressure of the inner-cavity on start-off temperature is concluded.Moreover,on the basis of which,the influence of the load resistance on the operating frequency of the system is compared.Furthermore,the effects of two different electrical resonances on the output power of the TAEGS are compared with the numerical analogical results to prove the validity of theoretical research and simulation analysis.