Study On Liquid Carrying Characteristics Of Two-phase Pressure Oscillation Tube

Gas wave refrigeration technology is a new type of gas expansion refrigeration technology,which uses the unsteady wave system of gas with different pressure in the pressure oscillation tube to realize energy exchange and separation of cold and heat to achieve the purpose of refrigeration,and has been widely used in the field of natural gas dehydration and dehydrocarbon.In order to prevent the formation of natural gas hydrate in the pipeline,alcohols are sometimes added to the air intake and there will be a variety of condensable components such as water and alcohol in the pressure oscillation tube.The water vapor in natural gas will affect wave system and the port matching of gas wave refrigeration.When the natural gas is in supersaturated state,the medium entering the gas wave refrigerator is in gas-liquid two-phase state.In view of the above problems,the following studies are carried out in this paper:(1)Set up the pressure oscillation tube double condensable components of non-equilibrium condensation and evaporation model,uses the CPA gas state equation in consideration of real gas effect.A single tube experimental platform with liquid quantity control was built,and the correctness of the numerical model was verified by pressure fluctuation experimental data.(2)The non-equilibrium phase change behavior and the change rule of wave system and properties in the pressure oscillation tube before and after alcohol injection of natural gas were studied by numerical simulation.The pressure fluctuation in the pressure oscillation tube during phase change was measured by using the whole machine experimental platform.Water vapor condenses and evaporates under the action of wave system,and the condensation heat release makes the low-temperature outlet temperature of gas wave refrigerator rise.The shock wave intensity of wet natural gas is lower than that of dry natural gas,and the condensation will weaken the expansion wave intensity,which is consistent with the conclusion of the whole machine experiment.The condensed droplets absorb the energy of the reverse shock and reduce its intensity and speed of propagation.The condensable components will affect the port matching of the gas wave refrigerator and increase the offset angle.With the increase of pressure ratio,the difference between the offset angle of dry gas and wet gas decreases gradually,which was reduced from 7.9% at pressure ratio 1.5 to 3.7% at pressure ratio 3.Adding methanol to wet natural gas can inhibit the condensation of water vapor and reduce the liquid water quantity,which is of great significance to prevent freezing and blocking and the formation of natural gas hydrate.After alcohol injection,the total condensable components of natural gas increases,the total condensed liquid phase increases,and the low-temperature outlet temperature increases.(3)The performance of the pressure oscillation tube with liquid is studied by numerical simulation when the inlet medium is gas-liquid two-phase state.After the liquid enters the pressure oscillation tube,most of it is discharged from the low-temperature outlet,and a small amount remains in the tube to enter the next cycle.The liquid phase in the tube tends to accumulate in the opposite moving direction of the tube.With the increase of liquid quantity and droplet size,it is not conducive to droplet timely discharge and refrigeration performance.The increase of high-temperature outlet pressure is beneficial to the discharge of droplets.The area with high liquid content in the tube is prone to droplet coalescence.Droplet breakage occurs at the left end of the tube at high pressure incident stage.Droplets movement in the tube was observed by high-speed photography experiment,and the results show that a large number of fog droplets appeared in the tube after the jet flow,and an inclined contact surface is formed behind the droplet jet during closing.Increasing the pressure ratio will increase the liquid flow rate and velocity during the jet.The results of single tube experiment show that the shock intensity in the pressure oscillation tube is weakened and the peak pressure is lower than that of dry gas.At 30wt% liquid quantity,the peak pressure decreased by 16.9%compared with dry air.The peak pressure decreases gradually with the increase of liquid quantity and rotational speed.