Preliminary Study On The Onset Mechanism Of Thermoacoustic Systems

Thermoacoustic engine is a new type of engine, which is based on the thermoacoustic effect. With no moving parts and using inert gas as working fluid, it has many advantages, such as simplicity, reliability, long operating life and pollution free over the traditional engines. As the fundamental problem of the thermoacoustic effect, onset mechanism of thermoacoustic systems has attracted more and more attention. The study will be helpful not only for understanding the energy conversion process in the thermoacoustic phenomena, but also for lowering the onset temperature of the system to make use of low-grade energy. Unfortunately, up to now scholars haven't come to an understanding on this problem.The research and development of onset mechanism of thermoacoustic systems in recent years were reviewed first. Focusing on the main theories and the experimental methods used in the thermoacoustic onset study, the difference between current theories and real thermoacoustic process was pointed out and the development prospect of thermoacoustic theory was given.In the theoretical analysis, we took the representative nonlinear model of thermoacoustic devices developed by the Johns Hopkins University as a research object. By correcting the momentum and energy exchange terms, a totally nonlinear quasi-one-dimensional model of thermoacoustic engine based on the cross section average was built in time domain. By programming and simulation with Matlab, the characteristics of self-oscillating process in a thermoacoustic Stirling engine was studied. Referring to the fluid network model and nonlinear oscillating circuit theory, the qualitative interpretations were given for the self-oscillation processes both in electric circuit and thermoacoustic engine.Meanwhile, the self-oscillating process in a thermoacoustic Stirling engine was experimentally studied. Through the analysis of pressure and spectrum, the characteristics of the three stages, energy storing, onset and saturation of the self-oscillating process were revealed. The influence of the helmholz resonator on the self-oscillating process was also given. In addition, our results were compared with the Sakamoto's experimental results.