Investigation On The Output Characteristics And Acoustic Resonator Of A Traveling-wave Thermoacoustic Electric Generator

Traveling-wave thermoacoustic electric generator has the merits of utilizating low-grade thermal energy, potential high efficiency, high reliability, and environment-friendly. However, the conversion efficiency of the thermoacoustic power generation technology needs to be further increased, and the power density of such system is usually low to get more output electric power. The problems have seriously restricted the applications. Investigation on the output characteristics and acoustic resonator of a traveling-wave thermoacoustic electric generator has great significance on improving the efficiency and making the whole system compact. To study the output characteristics and acoustic resonator of a traveling-wave thermoacoustic electric generator, theoretical analysis and experimental measurements have been conducted as follows.1. Theoretical investigation on the linear alternator and the spring oscillator. Analysis is made on the physical models of a linear alternator and a spring oscillator based on the electro-mechano-acoustical analogy. Electro-mechano-acoustical analogy diagrams and mechanical impedance diagrams of a linear alternator and a spring oscillator are obtained, respectively. The governing equations of a linear alternator and a spring oscillator are derived according to the mechanical impedance diagrams. The results of theoretical analysis show that the acoustic-to-electric efficiency of the linear alternator and the output characteristics of the traveling-wave thermoacoustic electric generator can be improved significantly by reducing the imaginary part of the circuit impedance.2. Theoretical and experimental investigation on the output improvement of the traveling-wave thermoacoustic electric generator. Traveling-wave thermoacoustic electric generator is simulated based on the linear thermoacoustic theory. The effects of load resistance, circuit resonance and pressure amplitude on the output characteristics of the system are analysed. An experimental traveling-wave thermoacoustic electric generator is designed and constructed. Experimental results show that the performance of the system can be improved significantly. The output electrical power is increased from122.9W to150.6W, corresponding to an increase from5.3%to7.8%for the thermal-to-electric efficiency after circuit resonance is achieved by reducing the imaginary part of the circuit impedance.3. Numerical simulation on the further improvement of the output performance of the traveling-wave thermoacoustic system with the use of mechanical resonator. The effects of mechanical resonator on the output characteristics of thermoacoustic system are simulated based on the linear thermoacoustic theory. The results of simulation show that the output characteristics of thermoacoustic system are improved significantly by the use of mechanical resonator: the maximum output acoustic power of the thermoacoustic engine is increased from266.8W to289.4W, when using the twin spring oscillators as mechanical resonator. When using the twin linear alternators as mechanical resonator, the maximum output electrical power of the traveling-wave thermoacoustic electric generator is increased from166.39W to379.05W.