Theory And Experimental Study Of Traveling-wave Thermoacoustic Electrical Generator

Travelling-wave thermoacoustic electric generation technology is developed in recent years. Thermoacoustic electric generator consists of two parts, thermoacoustic engine and generator. It has the merits of utilizate low grade thermal energy, no moving parts, friendly to environment, etc. But the travelling wave thermoacoustic electric generator, which has reported, the electric power output capacity and the thermoelectric conversion efficiency is not very ideal. The coupling mechanism between thermoacoustic engine and alt is unclear. The expensive linear motor in the thermoacoustic electric generator blocks the way of its possible commercialization. Low cost of thermal power generation system of the machine needs to be improved. Around these problems, this paper has carried out as follow:1. In-depth investigation on low cost thermoacoustic electric generation system. A two-stage traveling-wave thermoacoustic electric generator has been designed, which consists of two traveling wave thermoacoustic engine and two generating units. For reason of cost, we used loudspeaker, instead of traditional linear alternator, as the generating unit. Loudspeaker’s acoustic network diagram is given. Based on the network diagram, the basic expression was deduced. We selected the appropriate loudspeakers on account of the output electric power capacity and the thermoelectric conversion efficiency. We have given performance comparison of several types of loudspeakers.2. After theoretical analysis on thermoacoustic engine and alternator, a new-style two stage travelling wave thermoacoustic electric generator has been designed: two thermoacoustic engines are on the high impedance and low velocity area of ring, a loudspeaker in the low impedance of the loop area, the other loudspeaker in the top of bypass tube(stub). The thermoacoustic engines are placed in a high impedance area due to in the high impedance area the gas velocity is small, which can reduce acoustic viscous losses. Loudspeakers are placed in high velocity area because of high velocity means a bigger oscillate velocity and displacement. Electric power output ability is proportional to oscillation speed, so that we can get more electric power output.,3. The numerical simulation and optimized analysis on the two-stage traveling-wave thermoacoustic electric generator by the numerical simulation tools-DeltaEC.4. Based on numerical optimized analysis, a prototype was built. A ball valve was used in the loop to partly correct the acoustic field that was altered by manufacturing errors. Device used pressurized helium at 1.8 MPa as the working gas and operated at a frequency of about 171 Hz, a maximum electric power of 204 W and a maximum thermal-to-electric efficiency of 3.43% were achieved.5. An equivalent acoustic circuit of a loop-tube-type thermoacoustic system is built and analyzed the standing wave ratio using electro–methanol-acoustical analogy. It is found that the resistance, the inertance and compliance of the components in the system can influence strongly on the standing wave ratio. Furthermore, the detail study on the standing wave ratio using the linear thermoacoustic theory is described. The effect on the standing wave of the key parameters will be discussed, and criteria will be given to obtain an optimal standing wave ratio in the system.