Study On Performance Of Feedback Jet-oscillator And Application

High-performance expansion refrigeration equipment suited for operating condition of high pressure is needed urgently for natural gas' expansion refrigeration technology. Jet-oscillation refrigerator is a new type of expansion refrigerator, in which self-induced jet oscillator is used to generate oscillation jet's periodical injection into receiving tube with one-closed end. In the oscillation tube, gas waves are produced owing to interaction between the injected gas and the intrinsic gas. Energy is rapidly transferred from the injected gas to the intrinsic gas by means of propagation of those gas waves, which results in temperature increase of the latter and then heat dissipation to environment across the tube wall. The refrigeration of the injected gas is obtained due to its energy loss. The jet-oscillation refrigerator has no moving part and its seal is simple. Hence, its use is not confined under the condition of high pressure. Yet, the refrigeration efficiency of the jet-oscillation refrigerator is at a low level presently, and could not satisfy requirement of natural gas's industrial production. In this paper, the feedback fluidic device is introduced to jet-oscillation refrigerator for the high frequency performance. The performance and mechanism of the jet-oscillation refrigerator with feedback fluidic device are investigated in the current paper supported by Chinese 863 National Program Foundation "Study on new technology of combined utilization of natural gas's pressure energy "(No.2006AA05Z216).The bistable fluidic device is a key component of jet-oscillation refrigerator and it is developed on the basis of jet's wall-attaching effect which is also called Coanda effect. The frequency modulation of the jet's oscillation and decrease of total pressure loss of the jet passing the oscillator are important approach to improve the performance of the refrigerator. This paper studies the oscillation performance of jet in feedback device. First of all, the waveforms and internal flow field of the oscillation in feedback fluidic device are studies through the numerical simulation. The influence of geometrical size and operating condition also the media physical property on the performance of feedback device is investigated. The study emphasize on the variation of frequency and ratio of oscillation-available pressure with the geometrical size. Other factors determine the availability and stability of oscillation.The oscillation performance of jet, as oscillation frequency, is the essential data for designing the fluidic device, which is also the key factor that influence the coupling effect of fluidic device and receiving tube. This paper does experiment on the oscillation availability and frequency of feedback jet-oscillation gas wave refrigeration. As a conclusion, the jet oscillates only in a certain range of geometrical sizes and operating conditions. Under the condition of high pressure ratio, the frequency of the jet's oscillation is only affected by the feedback tube's length and chamber remarkably. Under the condition of low pressure ratio, the frequency descends with rise of the pressure ratio. The influence of outlet port clearance is explored. The change of receiving tube length mainly results in the variation of the highest oscillation-availability ratio of pressure and tube response.The field application showed that the multi-tube gas wave refrigerator is more effective than the double-tube. This paper also studies on the performance of multi-tube through numerical simulation emphasizing on the switching time. This paper draws a conclusion that the switching time grows with the increasing of feedback tube chamber. This law is favorable to improve the refrigeration efficiency.This paper introduces positive feedback to Jet-oscillation refrigerator and high frequency and a wide range of oscillation are obtained based on the oscillation property. This method widens the operation range of jet-oscillation refrigerator and lays a foundation for finding the optimal couple point and improving the refrigeration efficiency.