Numerical Simulation For Stack Structure Of Thermoacoustic Pulse Tube Refrigerator And Phase Modulation Mechanism

Abstract:Thermoacoustic stirling pulse tube refrigerator is a kind of cooling machine which is based on the stirling cycle, improving its efficiency is helpful to the application of national defence and military、 space exploration and so on; A pulse tube refrigerator is driven by thermoacoustic engine can improve stability and has a very broad application prospect. And the regenerator is the key to realize the thermoacoustic transformation, its special structure has a huge influence to the efficiency of thermoacoustic transformation. The numerical simulation of this paper by CFD commercial software Fluent as follows:(1) According to flat-plate regenerator, respectively establishing the numerical research model of thermoacoustic standing-wave engine for parallel-plate and sketch-plate regenerator, successfully capturing the thermoacoustic self-excited oscillation process, showing that the time required to achive saturation is shorter for self-excited oscillation of sketch-plate regenerator; analyzing the phase relationship between pressure and velocity,verifying the Rayleign criterion, the phase difference between axial pressure and velocity is90°,complying with the important property of standing-wave acoustic field; discussing the spectrum characteristic, the pressure amplitude for sketch-plate regenerator is much higher than parallel-plate, and is more steady, which is conductive to the matching for thermoacoustic system; observing the swirl flow around regenerator, sketch-plate regenerator is stronger, which is conductive to coupling between fluid and solid, improving the efficiency of thermoacoustic conversion;(2) Establishing the numerical simulation model of thermoacoustic refrigerator driven by thermoacoustic engine, investigating the phase relationship between pressure、velocity and the properties of axial distribution, verifying the correctness of numerical research; analyzing the characteristics of acoustic power distribution for different time, parallel-plate is relatively less; capturing the discipline of oscillation temperature at both cold and hot ends, the results show the refrigeration efficiency for parallel-plate is lower; in addition, for the disturbance of nonlinear acoustic field, the temperature-distribution for the both cold and hot ends is unstability;(3) Establishing the numerical simulation model of thermoacoustic stirling pulse tube refrigerator, respectively investigating the diameter and length of inertial, working frequency, and the entrance effect for the influence on refrigeration efficiency, the results show that refrigeration efficiency is decided by pressure、mass flow rate and the phase difference between them at the cold end heat exchanger, the smaller the diameter, the higher the frequency, the smaller the phase of the entrance, which is conducive to improve refrigeration efficiency; analyzing the velocity annular effect at the exit of the cold-end heat exchanger for different conditions, the results show it is decided by Valensi number Va and the maximum Reynolds number Remax; investigating the property of flow field distribution for compliance volume, observing many flow corners at the interface between the inertial tube and compliance volume, which lead to the heat could not discharge in time, the great temperature gradient exists between cold heat exchanger and compliance volume, seriously decreasing refrigeration efficiency and in addition. Pictures87, Tables6, References78...