Research On Acoustic Energy Control And Acoustic Energy Utilization Based On Thermoaccoustic Theory

Thermo-acoustic oscillation has always been the concern of researchers in the power engineering field.On the one hand,it caused the thermoacoustic instability,namely the low frequency oscillation of large amplitude,resulting in fatigue damage to system in a certain extent,there may even cause accidents flameout and so on;on the other hand,because of the thermo-acoustic effect,thermo-acoustic power generation technology has been developed,which can make use of low grade heat,in order to provide new ideas for the efficient utilization of solar energy and industrial waste heat.The paper will study from two parts:acoustic energy control and acoustic energy utilization.First of all,this paper built a thermo-acoustic characteristics experiment platform based on Rijke tube,explores the basic thermal-acoustic characteristics of different length and different power.The experimental results show that,with the increase of tube length,the initial excitation power decreases first and then increases,and the lowest vibrational power when the aspect ratio is 20;under the same aspect ratio,the sound pressure level showed an increasing trend with the increase of electric power,and the frequency remained basically unchanged;under the same power,with the increase of tube length,the change of sound pressure level shows a "bimodal" variation and the frequency decreases gradually.Secondly,considering synthetically,the paper built an acoustic energy control experiment platform with one meter long Rijke tube,achieve thermo-acoustic instability of active control by the speaker.The results show that,when a loudspeaker is placed at a certain distance from the inlet end of the tube,the active acoustic wave emitted by the loudspeaker will affect the unstable thermal pressure fluctuation in the tube,and meanwhile the pressure oscillation with the active acoustic wave will be generated;when the speaker sound frequency of 200Hz,sound pressure level of 120dB,the best control,up to 81.7%.The experimental results further illustrate the speaker is an effective method to thermo-acoustic instability of active control.Finally,in order to explore the experimental mechanism of acoustic-electric conversion,a speaker-based cold state and thermal state experiments were carried out.The cold state experiment is realized by two loudspeakers(emitting source and receiving source,respectively).The thermal experiment is realized based on Rijke tube,namely thermo-acoustic tube and loudspeaker.The experimental results show that,the closer the emitter frequency is to loudspeaker’s resonant frequency,the higher the output power and conversion efficiency of the receiver;the conversion efficiency increases first and then decreases with the increase of load resistance,and there is an optimal load area That is,between 10-30Ω,the conversion efficiency η can be maintained at 30%-45%;as the heat source voltage increases,the speaker output voltage and output current also increased,namely the actual power of the speaker also gradually increased,which demonstrated the feasibility of thermo-acoustic conversion and provided the experience for task group project "Low-grade thermal-driven thermo-acoustic power generation research".