| The research in this article is based on the study contents and patents of NSFC Projects(51276026).The different excitation modes and the response characteristics of the main jet are studied in the stationary gas wave refrigerator.Thestructures of feedback and sonic self-excited jet oscillator have been optimized to compare with the optimized structure of the new external stimulation oscillator.And the results have been verified by experiments.According to the urgent need of time-avenged jet in low duty cycle of high refrigeration efficiency,the study of external stimulationtwo-stage oscillation has been started.A kind of two-stage stimulating flow modulation device has been designed and manufactured,which worked in the two-stage oscillation experiment.The specific research contents and corresponding conclusions are as follows:(1)The evaluation indexes of wall-attached jet oscillatorare defined,which are total pressure retention rate K and wall-attached jet switching time cycle proportion R.Taking K and R as the performance evaluation indexes in the self-excited oscillator’s optimization process,the optimal feature parameters of two kinds of self-excited jet oscillators have been obtained.After optimization,the total pressure retention rate of the feedback wall-attached oscillator is relatively increased by 9.6%,and the K of the sonic wall-attached oscillator is relatively increased by 19.7%.(2)The total pressure simulation curvesof the stimulation orifice and the outlet,which is in self-excited and external stimulation oscillators,suggested that the total pressure of the self-excited jet oscillator is lower than that of the external stimulation oscillator,and would consumethe primary jet flow energy.The self-excited flow produces a large amount of energy loss and cannot be avoided.As a result,the total pressure retention rate of self-excited oscillator is lower than that of the external stimulation jet oscillator.Even in the optimized structure,the K of the feedback and the sonic oscillator is still lower 14.0% and 6.0% than that of external stimulation oscillator respectively.The wall-attached jet switching time of self-excited is longer than that of external stimulation oscillator.After optimization,the R of the feedback and sonic oscillator is higher than that of the external stimulation oscillator 12.5% and 10.7% respectively.(3)The optimized wall-attached jet oscillators have been modeled,which have been used to experiment.The experimental results were compared with the simulation results,then the comparative analysis was made among the different excitation modes of wall-attached oscillators.The experimentalK value is lower than that of the simulation in self-excited and external stimulation oscillators.The K of the feedback and the sonic oscillator reduced 17.0% and 23.5% respectively,and the K of the external stimulation oscillator reduced 6.3%.The experimental R value is higher than that of the simulation in self-excited and external stimulation oscillators.The R of the feedback and the sonic oscillatorwere increased by 13.0% and 13.5%respectively,and the R of the external stimulation oscillator was increased by 7.1%.The experimental results suggest that the energy efficiency of the new external stimulation jet oscillator is much higher than that of the self-excited jet oscillator.(4)The numerical simulation of external stimulation two-stage jet oscillator suggested that,two-stage jet oscillation switch should be from the insideof branch channel switching to another outside of branch channel,same order in return.Under different oscillation frequencies,the outlet jet of the two-stage oscillator has fine properties,which canfulfill the requirements of multi-tube static gas wave refrigerator.The total pressure retention rate of the four outlet of the external stimulation two-stage jet oscillator can be maintained at K of 87.3%,which is 5.7% higher than the lateral branch of multi-tube oscillator,and 26.3% higher than that of the medial branch of multi-tube oscillator.Therefore,the external stimulation two-stage oscillator efficiency and performance are better than the traditional multi-tube sonic jet oscillator.(5)On the basis of the numerical simulation of the two-stage wall-attached oscillator,experimental study on two-stage wall-attached oscillation was carried out.Aiming at the modulation of two-stage stimulation flow,the two-stage rotary valve was designed and manufactured,which worked in the stimulation flow modulation generation system.The measured waveform and analog waveform of stimulation orifice and outlet were compared,and the exhaust sequence of outlets was verified experimentally.Through the contrast experiment under the same operating condition of multi-tube wall-attached sonic oscillator,it has been proved that the external stimulationtwo-double stage wall-attached oscillator has the bettertime-averaged and energy efficiency. |
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