Study On Operating Mechanism And Performance Of Energy-focused Thermoacoustic Engine's Resonator

A thermoacoustic engine has obvious advantages of high reliability and environmental friendliness and the good potential of reaching high conversion efficiency. Great progresses have been seen for thermoacoustic technology in recent years. The resonator is one important part in the thermoacoustic engine, which has complicated interplay with the thermoacoustic transformation core, and it needs to be studied in-depth. Focusing on the operating mechanism of the resonator and the operating characteristics of thermoacoustic engines with several hundreds Hertz, the following works have been conducted:1. The thesis summarized the progress of thermoacoustic technology briefly. In addition, linear thermoacoustic theory in Euler viewpoint was reviewed. Then, thermoacoustic micro-cycle theory in Lagrangian viewpoint was introduced.2. The operating mechanism of the resonator was analyzed. First, an analytical expression for the fundamental resonant frequency of symmetrical tapered resonators was obtained. Then, three simulation tools, a self-developed numerical simulation code based on linear thermoacoustic theory, computational fluid dynamics (CFD) simulation and a thermoacoustic code (DeltaE) were used to study the operating performance of the different tapered resonators and were compared each other. The simulations clearly indicate that a tapered resonator has a function of improving the pressure ratio and thermoacoustic conversion performance.3. A 300Hz standing-wave thermoacoustic engine was designed and experimentally investigated. The experimental result showed how the operating parameters and structural parameters (including stack and resonator) affected the onset temperature, the pressure ratio, the heating temperature, the oscillating pressure amplitude and so on. Furthermore, the experiment proved the analysis for the tapered resonator in the afforded-mentioned numerical simulation, and indicated that the thermoacoustic system with a tapered resonator has a better thermoacoustic conversion performance.4. The output performance of acoustic power for a 500 Hz standing-wave thermoacoustic engine was investigated experimentally. By applying the RC load method, we experimentally studied the influence of locations and different resonators (straight and tapered resonators) on the net output performance of the thermoacoustic engine. It was found that the location affected little for the straight resonator, while a bigger influence for the tapered resonator; moreover, the tapered may increase thermoacoustic efficiency by about 20% compared with the straight resonator.