| A thermoacoustically driven pulse tube refrigerator, which has no moving parts, is attracting more and more interest of academic circles and industry. This new concept refrigerator occupies outstanding advantages of simplicity, reliability, stability, longevity, no pollution and so on.This paper reviews the developments and applications of thermoacoustic engines, introduces the research development of thermoacoustic theories, analyzes the significance of the exploration of non-linear thermoacoustic theory and concludes the development of the non-linear thermoacoustics. Then, The following sections are carried out:1) The structure, function and the influence on the performance of thermoacoustic engine of heaters, water-coolers, and hot buffers of both the former and present standing-wave thermoacoustic engine have been discussed respectively.2) The performances of the former and present thermoacoustic engines without load, thermoacoustic engine driven RC (Resistance and Capacitance) load with the pressure amplifier and thermoacoustic engine driven pulse tube refrigerator have been compared and analyzed. According to the results of experimentation, it is found that the present thermoacoustic engine can drive a longer pressure amplifier, work under higher heating power and provide bigger pressure ratio and pressure amplitude at the outlet of the pressure amplifier. Consequently, the maximum acoustic power supplied to the RC load by the present thermoacoust engine is increased compared with the former system. The pulse tube refrigerator driven by the present thermoacoustic engine has achieved a cooling temperature as low as 75.62K, lower than that of 79.7K which is achieved with the former engine.3) The effect on amplifying pressure of the acoustic pressure amplifier is analyzed theoretically. The influence of length of the pressure amplifier on the performance of the standing-wave thermoacoustic engine was simulated and investigated experimentally. It is shown that in two different ranges of acoustic resistance, the performance of the system along with the increase of the length of the pressure amplifier greatly differences from each other.4) Firstly, the phenomena of frequency shift that is observed in the experiment is concluded and the operating patterns of the standing-wave thermoacoustic system are classified and defined respectively. Then, the range of acoustic resistance in which frequency shifts, the relationship between frequency shift and input power and the relationship between frequency shift and the length of the acoustic pressure amplifier are analyzed and concluded. Eventually, a weakly nonlinear theory of the thermoacoustic instability which was proposed by S. karpov, A. Prosperetti et al. is used to qualitatively analyze and explain the phenomena of frequency shift. The results of experiments are found to be basically in accordance with the weakly nonlinear theory.
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