Study On The Mechanism Of Parametric Excitation Of Thermoacoustic Engine

With the improvement of efficiency and the extension of application foreground, thermoacoustic engine has stepped up to the stage of engineering practice. It is necessary to develope new theory and method to satisfy engineering demand, because any operating thermoacoustic engines are all open nonlinear system. Based on experimental investigation of thermoacoustic engines and former works, the theory of mechanism of parametric excitation of thermoacoustic resonance is gradually formed, and experimental mode analysis is put forward as an important research method.In this paper, basing on thermal dynamics, phenomenon of self-oscillation of thermoacoustic engine, and substituting time-varied parameter for periodic average parameter, stability of the system is opened out with mechanism of parameter excitation. In this way, it is possible for the net theory of mechanism of parameter excitation to be used to research nonlinear problem. We discuss several aspects about the mechanism of the parametric excitation which include the action of regenerator's storing energy, filtering, magnifying, the condition of onset oscillation, stability of the system, and so on.The dynamic characteristics of the system are researched, and plentiful data are obtained which are sound pressure and temperature of regenerator. By analyzing these time serial data, we obtain trends of parametric variation of regenerator. The correlation of the trends and dynamic transformation of the system, which include mode, penetration depth, distribution function and time scale, etc. Model and value of the regenerator's percentage modulation is established with experimental identification method.The author design and make a standing-wave tube for lucubrating the mechanism of the parametric excitation, and calculate mode of this tube with the DeltaE program. The natural frequency of the tube is obtained with the calculating.The author experiments dynamic characters of the tube with sweep-frequency technology. The author obtain some illumination by analyzing time serial of input and output pressure signal, it is possibly important signification for engineering practice to realize regenerator's optimization configuration and the system matching. The dynamic character of the regenerator is researched with method of the experimental mode analysis, transfer function and oscillation modes of the regenerator are obtained with ARMA modes of the time serial. Results of the mode analysis help are in favor of understanding theory of mechanism of parametric excitation of thermoacoustic resonance and optimizing the system.