| Gas-wave refrigeration is a kind of refrigeration technology that utilizes waves moving in the oscillation tube to transfer energy between gases.It holds the characteristics of high expansion efficiency,large liquid carrying capacity and easy maintenance.At present,it has been successfully implemented in the field of gas expansion refrigeration;such as small and medium-sized subzero wind tunnel and natural gas subzero treatment system.In order to improve the theory of gas-wave refrigeration,expand the application range of gas-wave refrigeration technology and promote the development of gas-wave refrigeration technology,the characteristics of gas flow and energy transfer in double-opening oscillating tube should be studied in depth and the methods of improving the performance of gas-wave refrigeration should be sought.It is found that the double-opening oscillating tube has high supercharging performance,which is derived from the dynamic characteristics of the moving shock wave in the tube.Using this supercharging method to improve the performance of gas-wave refrigerator is a novel direction of gas-wave refrigeration technology.Based on the thought of pressure energy recovery,it is proposed to construct a pressurization process by using shock wave before gas expansion.In this way the expansion work can be recycled,the inlet pressure of the compressor can be improved.The compression ratio of the compressor can be low down and the power consumption of the external compressor is greatly reduced.Thanks to the fresh gas is pressurized twice before expansion refrigeration.This method can be called twice pressurized gas-wave refrigeration method,which is suitable for improving the performance of gas-wave refrigeration with external pressurization.In this paper,the experimental platform is established.The gas-wave refrigeration method with shock pressurization process is studied combining theory and experiment.The research contents and conclusions are summarized as follows:(1)The gas fluctuation process in a double-opening oscillating tube is researched.Based on the one-dimensional unsteady flow theory,the flow wave diagram of the double-opening oscillating tube is established to reveal the gas flow and energy transfer law in the double-opening oscillating tube.The energy transfer efficiency of the shock wave in that tube is analyzed,and the relationship curve between the pressure ratio of expansion refrigeration and efficiency of shock wave pressurization is obtained.The structure design method of the double-opening oscillation tube gas-wave refrigerator is established.The method can be used to optimize the structure parameters of gas-wave refrigerator.(2)The morphology of interface between cold and hot gas in a double-opening oscillate tube is studied.The effects of interfacial morphology on the performance of gas-wave refrigeration with supercharging process are revealed.Two graphical representation methods are proposed to reveal the shape of the interface.The results show that the width of the interface reflects the mass and energy exchange in the double-opening oscillating tube.The maximum moving distance Lmax and the low temperature exhaust width WLT have a great influence on the performance of the twice pressurized gas-wave refrigeration.What's more,the mixing of the exhaust gas at the tail end of the interface is an important factor affecting the refrigeration efficiency.With increase efficiency of shock wave pressurization,the shape of that interface changes from wide to narrow.It reveals the matching relationship between the performance of shock wave pressurization and the width of the low temperature exhaust port.The performance of gas-wave refrigerator can be improved by controlling the mixing area of cold and hot gas in the oscillating tube.(3)The effect of low-temperature exhaust direction on the performance of gas-wave refrigerator in double-opening oscillating tube was studied.According to the different exhaust direction of low temperature,the double-opening oscillation tube can be divided into two types:through-flow(TF)type and reverse-flow(RF)type.Gas flow and energy transfer in these two kinds of double-opening oscillating tubes are analyzed by numerical and experimental methods.The results show that the flow wave diagrams of these two types are quite different.However,pressurization performance of the shock wave in these two types is exactly the same.There is another mixing process between low-temperature gas and normal gas in the through-flow oscillation tube,hance the matching accuracy of the TF oscillating tube is higher than the RF oscillating tube.The experimental results show that gas leakage and heat transfer have a great influence on the performance of TF gas-wave refrigerator,so the RF double-opening oscillating tube is more suitable for refrigeration.(4)The method of twice pressurized gas-wave refrigeration using shock wave to transfer energy is studied systematically.A flow model with external pressurization and heat dissipation is established.In this numerical model the effect of external compressor pressurization and heat dissipation are taken into account.The energy transfer phenomenon in the whole refrigeration process is analyzed.The results show that the calculated results of the numerical model are in good agreement with the experimental results.What's more,the thermodynamic model of refrigeration system is established,and the influence of main parameters on refrigeration performance is analyzed.It is found that improving the efficiency of expansion is the key to improve the refrigeration performance of the system.Experimental analyses are carried out to study the influence of operating parameters and structural parameters on the performance of twice pressurized gas-wave refrigeration.The results show that the performance of the twice pressurized gas-wave refrigeration is 2.3 times of that of the external dissipation gas-wave refrigeration.About 53 percent of the expansion work can be recovered by shock wave in the double-opening oscillation tube,so the refrigeration performance is greatly improved.(5)The method of gas-wave dehumidification with pressurization process is studied.The pressure energy of dehumidification dry gas can be recovered by shock wave transmission energy,which can reduce the expansion ratio and improve the refrigeration efficiency of the refrigeration system.The cold quantity of the dry gas can be recovered and be used to precool the high pressure gas of the next refrigeration cycle,which could increase the depth of refrigeration.Because the fresh gas expansion process and dry gas pressurization process are carried out simultaneously in a double-opening oscillating tube,dry and wet gas mixing is inevitable.In this paper,a control method for the mixing section of dry and wet gas in a double-opening oscillating tube is proposed.What's more,a thermodynamic model of gas-wave dehumidification is established,and the influence of main parameters on the system performance is analyzed.Finally,the experimental study is carried out.The results show that under the condition of 1.1 pressure ratios of system refrigeration,the temperature drop is 35?in the system,and the pressure recovery coefficient reaches at 0.9.It means that this method can enhance the refrigeration efficiency.Although the refrigeration method does not output cold quantity to outside,it can be utilized in the process of gas dehumidification and purification.The experimental results can provide guidance for industrial applications. |
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