Study On Fluctuation And Phase Transition Characteristics Of Gradual Pressure Oscillating Tube

The gas wave refrigeration technology uses the shock wave and the expansion wave in the pressure oscillation tube to realize the cold and heat separation,thereby achieving the purpose of refrigeration.The shock wave and the expansion wave in the oscillating tube respectively increase and decrease the temperature of the gas in the tube,in order to reduce the shock intensity in the oscillating tube and increase the intensity of the expansion wave,thereby increasing the expansion depth of the oscillating tube.In this paper,a gradient pressure oscillating tube structure is proposed,the pressure fluctuation and phase transition characteristics in the tube are studied.The main research work and conclusions of this paper are as follows:(1)The incident shock wave,the incident expansion wave,and the expansion depth in the gradient type and the straight pressure oscillation tube are compared.Through research,it is found that the gradient pressure oscillation tube can effectively weaken the intensity of the incident shock wave and increase the intensity of the incident expansion wave.The gradual structure increases the expansion depth by 24%,and the increase of the expansion depth increases with the increase of the compression ratio.As the gradient angle increases,the expansion depth increases first and then decreases.(2)The difference between the contact surface of the gradient type and the straight pressure oscillating tube,the moving distance of the blending surface and the port matching were studied.The gradient type pressure oscillation tube can reduce the moving distance of the contact surface in the oscillation tube and reduce the length of the blending surface.As the gradient angle increases,the moving distance of the contact surface and the length of the blending surface gradually decrease.In the case of the same size of the high pressure port,the high temperature port of the gradient type pressure oscillation tube refrigerator is smaller than the straight pressure oscillation tube,and the solid wall length of the upper end of the high pressure inlet is larger than that of the straight pressure oscillation tube.(3)The liquid phase parameters of the gradient type and the straight pressure oscillation tube after the reflection expansion wave were studied,and the influence of the working condition on the liquid phase parameters was studied.The gradual structure makes the radius of the condensation droplets smaller,but the range of the sufficient liquefaction zone,the number of droplets,and the mass of the liquid phase become large.As the gradient angle increases,the number of droplets and the mass of the liquid phase increase,and the droplet radius and liquefaction rate decrease.As the relative humidity of the intake air increases,the number of droplets increases first and then decreases.When the relative humidity is 40%,the number of droplets reaches a maximum,and the radius of the droplets,the range of the sufficient liquefaction zone,and the mass of the liquid phase increase.The relative humidity of the intake air is constant.As the intake air temperature decreases,the number of droplets and the liquefaction rate increase,and the droplet radius and liquid phase quality decrease.The moisture content of the intake air is constant,and as the intake air temperature decreases,the number of droplets,the liquefaction rate and the droplet radius increase,and the liquid phase quality decreases.The relative humidity of the intake air is constant.As the intake pressure increases,the number of droplets and the liquefaction rate increase,and the droplet radius and liquid phase quality become smaller.The moisture content of the intake air is constant.As the intake pressure increases,the number of droplets,the droplet radius and the liquefaction rate increase,but the liquid phase quality decreases.(4)Set up an experimental platform for external circulation gas wave refrigerator to study the effect of different operating parameters on the efficiency of the refrigerator.When the high-pressure intake air moisture content increased,the entropy efficiency of the refrigerator gradually decreased.The isentropic efficiency decreased by 3.6% and 6.0%,respectively,when the compression ratio was 2.5 and 3.5.As the pressure of the high temperature port increases,the isentropic efficiency of the refrigerator increases first and then decreases.The isentropic efficiency of the refrigerator increases first and then decreases as the speed increases.When the compression ratio is the same,increasing the high pressure intake pressure can increase the isentropic efficiency of the refrigerator.