Xiujuan Xie

Investigation on the oscillation modes in a thermoacoustic Stirling prime mover: mode stability and mode transition

The purpose of this paper is to investigate the stability of oscillation modes in a thermoacoustic Stirling prime mover, which is a combination of looped tube and resonator. Two modes, with oscillation frequencies of 76 and 528 Hz, have been observed, stabilities of which are widely different. The stability of the high frequency mode (HFM) is affected by low frequency mode (LFM) strongly. Once the LFM is excited when the HFM is present, the HFM will be gradually slaved and suppressed by the LFM. The details of the transition from HFM to LFM have been described. The two stability curves of the two modes have been measured. Mean pressure Pm is an important control parameter influencing the mode stability in the tested system.

NaAlSi3O8-hollandite and other high-pressure minerals in the shock melt veins of the Suizhou meteorite

The Suizhou L6 chondrite contains a few very thin shock melt veins of 0.02–0.09 mm in width. In spite of small width of the veins, shock-induced high-pressure phases, such as coarse-grained NaAlSi3O8-hollandite, ringwoodite, majorite and fine-grained matrix majorite-pyropess have been discovered in these veins. NaAlSi3O8-hollandite, the high-pressure phase of plagioclase, in Suizhou shock veins occurs as a single phase mineral, no silicate glassy phase, such as albitic glass, was incorporated with it. The presence of above-mentioned high-pressure phases constrains the high pressure (up to 23–24 GPa) and high temperature (up to 1900–2000°C) regime in Suizhou shock veins, and indicates that the duration of high-pressure regime in the veins should be long enough (a few seconds) for phase transformation and crystallization of minerals under pressure. The discovery of the first natural single-phase crystalline NaAlSi3O8-hollandite in Suizhou meteorite is of important significance in understanding the Earth’s mantle geochemistry.

Analysis of entropy generation rate inside the stack of standing-wave thermoacoustic refrigerator

Considering from the second law of thermodynamics, the equation for entropy generation rate near a single-plate, representative of the stack inside thermoacoustic refrigerators was derived in this paper. It indicates that entropy generation is produced due to heat transfer in the x-y direction of finite temperature gradients and fluid friction irreversibility. Analysis of global entropy generation rate versus the position of the stack, 2x/λ and the volume porosity, φ were carried out. The results demonstrated that the optimal position of the stack was within 0.8 <2x/λ <0.83, and the optimal volume porosity was 0.7.

Study of an open-air traveling-wave thermoacoustic generator

Based on linear thermoacoustic theory, an open-air traveling-wave thermoacoustic generator with 1 bar air has been designed and built up. The dimensions of regenerator and resonator influence on the resonant frequency, driver ratio, acoustic power and temperature difference are simulated and optimized to acquire the perfect performance, respectively. According to above simulated results, the acoustic pressures at the open end and 0.5 m far away from the open end of the resonator versus the heating power are investigated experimentally. The improved maximum acoustic pressures are up to 133 dB and 101 dB ref 20 μPa, respectively.