The Movement And The Influence Of Shock Wave On The Cooling Effect In The Oscillatory Tube

As a novel expander for cooling gas, the pressure wave refrigerator (PWR) is widespread application in the domain of petrochemical industry, gas cooling and cryogenic engineering. The cooling effect of oscillatory tube, which is the basic refrigeration unit, is mainly influenced by the generation and movement of the shock wave in the tube. The coupling relationship between the structural parameters and operation parameters of oscillatory tube and the flow parameter in the tube is established based on the shock wave, so it is necessary to make an intensive study of the generation reason, the movement regular pattern, the strength and influence factor on that of the shock wave in the oscillatory tube. Thus this study is not only provided the basis for optimal design of PWR, but also used to reveal the flow regular pattern of this style unsteady flow and refrigeration principle of PWR, which does its little bit to help the Gas Dynamic.The methods including theoretical analysis, experimental test and numerical simulation are used to study the movement of shock wave in the oscillatory tube and the influence on the cooling effect of the oscillatory tube. The main work and conclusions are as follows:(1) The flow between the two sides of contact face in the gas charging instant was analyzed theoretically by utilizing the principle of gas dynamic. That three generation reasons of shock wave in the tube was got. The computing results show that the strength of incident shock wave when using the contraction nozzle was strongest in the same gas charging and exhausting parameters, when the ratio of the expansion ε was form 2.0 to 12.0.(2) The phenomenon of partial injection in the process of actual gas charging was analyzed. It was founded that the shock wave in the tube was generated at a position which was a certain distance from the open end. The theoretical formula about the shock wave generation position was derived. The results showed that the value of the shock wave generation position coordinate xc was relative with the driving gas total pressure and the nozzle rotating speed. The reason that refrigeration efficiency of PWR was very low and the variation gradient was large in low rotating speed region, but the variation gradient of refrigerating efficiency was small in high rotating speed region was analyzed.(3) The process of incident shock wave attenuation in oscillatory tube was investigated by the experimental data. The results showed that the relative strength of incident shock wave △px/△po was reduced with the increase of relative position in length x/L because the energy of the reflected shock wave was exhausted by the viscosity and friction of the gas inside the tube. The other reason was the result of the gas in the tube pressurized and heated by the shock wave. The shock wave strength also was influenced by transmission and reflection effects occurred with the reflected shock wave. The influence on the cooling effect of oscillatory tube was also investigated. The attenuation formula was got by the dimensional analysis and experimental data, and the results were in good agreement with the experimental data. The maximum error is 5.70%。(4) Based on the theory of gas dynamics and thermodynamics, the influence of the flow parameters on the strength of incident shock wave and ideal refrigeration efficiency was investigated. The results showed that strength of incident shock wave and refrigeration efficiency could be enhanced by enhancing the wall heat transfer and increasing the pressure ratio With the help of movement regular pattern of shock wave in the tube, the universal relation between the operation parameters, the working medium properties, structural parameters and refrigeration performance of PWR were established. The coupling relationship between those factors and the unsteady flow in the tube was derived.(5) The influence of the movement of shock wave on refrigeration performance of PWR were studied experimentally. The experiment results showed that the maximum refrigeration efficiency of the pressure wave refrigerator (ηmax) was firstly increased when the pressure ratio (ε) was increased, and then decreased after ηmax achieving the maximum. It was the similar regular pattern for the influence of tube length (L), relative ratio of charge-to-exhaust time (ζ) and relative depth of jet hole in the gas distribution (b1/d) for 77 respectively, but increasing interval distance between oscillatory tube and jet hole (δ) and misalignment angles between the central axises of nozzle and oscillatory tube (ψ) would cause η sudden drop. It was useful to weaken reflected shock wave and improve the refrigeration performance of PWR when installing shock wave absorber. The influence of the structural transformation of shock wave absorber and the operation parameters and structural parameters of oscillatory tube on the effect of wave dissipation was investigated.(6) The partial injection effect and the influence of that on the generation movement of shock wave at the closed end of oscillatory tube were studied by utilizing the numerical simulation method. The results showed that the vortex was generated what was caused by the partly injection effect. The driving gas was strongly mixed with the oscillating gas, at the same time the driving gas was partly leaked to the exhaust chamber. Thus the generation and strength of the incident shock wave was influenced by that. Finally the influence of the factors, i. e. the ratio of expansion and rotating speed, on the partial injection effcet was analyzed.