A regenerative refrigerator multistage expansion system

Abstract

The application relates to a multi-stage expansion system of a regenerative refrigerator, which comprises a compressor device and a regenerative refrigerator device connected in sequence; the expansion assembly comprises multi-stage expansion cylinders, expansion pistons arranged in the multi-stage expansion cylinders, and regenerators matched with the expansion pistons; the diameters of the multi-stage expansion pistons are sequentially reduced; at least one expansion cylinder in the multi-stage expansion cylinders is provided with an augmented expansion piston, and an expansion piston sealing mechanism matched with each expansion piston including the augmented expansion piston is arranged in the expansion cylinder, so that the refrigeration stage number of the refrigerator is correspondingly increased. Compared with the prior art, the application adds the insertion unit of the cylinder and forms the stepped expansion piston, the refrigeration stage number of the refrigerator is increased by a simple method, more refrigeration capacity of temperature level is output, the entropy production loss caused by the temperature difference is reduced, the refrigeration efficiency and the liquefaction efficiency are improved, and a lower refrigeration temperature is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of refrigeration technology, in particular to a multi-stage expansion system of a regenerative refrigerator. BACKGROUND

[0002] The regenerative refrigerator is a kind of refrigeration technology in the form of alternating flow, which uses a regenerator to realize the periodic heat storage and release between the gas working medium and the regenerator filler, and uses the expansion of the gas to produce the refrigeration effect. The regenerator generally has a large specific surface area per unit volume, and the structural forms include wire mesh, pellet filler, gap type, etc. The regenerative low-temperature refrigerator has the advantages of high reliability, simple structure, high efficiency, etc., and is widely used in low-temperature technologies such as gas liquefaction and superconducting cooling.

[0003] The basic refrigeration principle of the G-M refrigerator is adiabatic expansion work. The GM compressor compresses the low-pressure gas to high pressure, cools and separates the oil, connects the refrigerator cold head part through the gas distribution mechanism, transmits PV work, realizes high and low pressure fluctuation, regenerates in the regenerator, and expands to refrigerate in the expansion chamber.

[0004] In the Stirling refrigerator, the compressor reciprocates to realize high and low pressure fluctuation, and then there is no gas valve, which connects the direct refrigerator cold head part, transmits PV work, regenerates in the regenerator, and expands to refrigerate in the expansion chamber. The compression piston and the expansion piston move with a certain phase difference. The expansion piston is also called the displacer.

[0005] The G-M refrigerator and the expansion piston type refrigerator such as the Stirling refrigerator generally adopt an internal structure, that is, the regenerator is placed in the expansion piston, so that the structure is compact.

[0006] A refrigerator that uses the same compressor to drive multiple-stage expansion cylinders to refrigerate at multiple temperature levels is called a multi-stage expansion refrigerator, and this refrigeration process can also be called "series expansion".

[0007] The two-stage refrigerator has one compression space and two expansion spaces. In fact, the expansion piston is made into a stepped shape to form two expansion chambers, so that a small amount of gas is expanded in the first-stage expansion chamber, and a large amount of gas is expanded in the second-stage expansion chamber. The first-stage refrigeration temperature is higher, and the second-stage refrigeration temperature is lower. The refrigeration capacity generated by the first stage provides a thermal barrier for the second stage, absorbs heat leakage from room temperature, and protects the second stage from refrigerating at a lower temperature. The first-stage expansion chamber acts as an intermediate refrigeration point, which generates refrigeration capacity to compensate for all irreversible losses from room temperature to the first-stage refrigeration temperature interval, so that the second-stage expansion chamber only needs to provide additional refrigeration capacity to compensate for the additional refrigeration capacity required to compensate for the cold loss from the intermediate refrigeration point to the second-stage refrigeration temperature interval.

[0008] Current liquefaction and other applications are widely used, and need to provide refrigeration capacity at more refrigeration temperature levels for sensible heat. The prior art uses the cold end refrigeration capacity (temperature T c ) of the refrigeration machine (usually two stages) to utilize the cold capacity, and provides the refrigeration capacity at the intermediate temperature of the pre-cooling stage (temperature T1). However, the cold capacity cannot be provided between the cold end temperature T c and the pre-cooling stage temperature T1, and between the pre-cooling stage temperature T1 and room temperature, that is, the refrigeration capacity cannot be provided in those intervals, resulting in reduced pre-cooling efficiency. If the number of expansion stages is increased, the structural complexity is increased and the manufacturing cost is relatively high. SUMMARY

[0009] The purpose of the present application is to overcome the defects of the prior art and provide a regenerative refrigeration machine multi-stage expansion system. The present application increases the number of refrigeration stages of the refrigeration machine to output more refrigeration capacity at different temperature levels, so that the refrigeration capacity at a suitable temperature level can be selected according to actual needs, thereby reducing the entropy loss caused by temperature difference and improving the refrigeration efficiency.

[0010] In the present application, if a multi-stage expansion method is used, the cold loss can be compensated by outputting cold capacity at the intermediate temperature level, thereby saving the cold capacity at the low temperature level, making the energy utilization more reasonable, improving the overall efficiency of the machine, and obtaining a lower refrigeration temperature. The method of modifying the original refrigeration machine has a low manufacturing cost and low structural complexity.

[0011] The purpose of the present application can be achieved by the following technical solutions:

[0012] The purpose of the present application is to provide a regenerative refrigeration machine multi-stage expansion system, comprising a compressor device and a regenerative refrigeration machine device connected to each other, wherein the regenerative refrigeration machine device comprises a regenerator assembly, an expansion assembly, and a cold end heat exchanger assembly;

[0013] The expansion assembly comprises multi-stage expansion cylinders, expansion pistons arranged in each stage of the expansion cylinders, and regenerators matched with each stage of the expansion pistons, wherein the diameters of the multi-stage expansion pistons decrease in turn;

[0014] The lower end of each stage of the expansion pistons is provided with a tubular low-thermal-conductivity insertion unit, and the insertion unit is matched with the multi-stage expansion pistons in diameter and length;

[0015] In the multi-stage expansion cylinder, at least one expansion cylinder is additionally provided with a multi-stage expansion piston, and a matching expansion piston sealing mechanism is arranged between the insertion unit and each expansion piston, so that the number of refrigeration stages of the refrigeration machine is correspondingly increased.

[0016] Further, the insertion unit is fixedly connected with the corresponding stage of the expansion cylinder, and the expansion piston sealing mechanism is clamped between the insertion unit and the expansion piston.

[0017] Further, the expansion piston sealing mechanism is arranged on each stage of the expansion piston and the cylinder, or distributed in part or the entire expansion piston interval.

[0018] Further, the expansion piston sealing mechanism is an elastic sealing ring or a gap sealing ring.

[0019] The space above the insertion unit constitutes an expansion chamber.

[0020] The diameters of the multi-stage expansion pistons decrease from top to bottom, thereby forming a stepped expansion piston.

[0021] Further, in one or more stages of the multi-stage expansion system of the regenerative refrigerator, the expansion piston sealing mechanism is arranged on each stage of the expansion piston and the cylinder, or distributed in part or the entire expansion piston interval.

[0022] In at least one stage of the expansion structure, an additional expansion piston is arranged, and in other stages of the expansion structure, no additional expansion piston is arranged.

[0023] Further, the regenerative refrigerator device is a refrigerator that uses a regenerator component to realize the alternate storage and release of heat, and the regenerator component is arranged in the expansion component.

[0024] Further, the refrigerator includes one or more of the following: a GM refrigerator, a Solvay refrigerator, a Stirling refrigerator, and a VM refrigerator, or a mixed structure formed by coupling one of the GM refrigerator, the Solvay refrigerator, the Stirling refrigerator, and the VM refrigerator with a pulse tube refrigerator.

[0025] Further, the average working pressure in the multi-stage expansion system of the regenerative refrigerator is 0.1 to 3000 times the atmospheric pressure (0.01-300 MPa).

[0026] Compared with the prior art, the present application has the following technical advantages:

[0027] 1) The present application uses a variable cross-section multi-stage regenerative refrigerator unit, which changes the cross-sectional area of the expansion piston and adds an expansion piston sealing mechanism, thereby increasing the number of expansion stages of the refrigerator, outputting more refrigeration capacity at different temperature levels, and selecting the appropriate temperature level of the refrigeration capacity for use according to actual needs, thereby reducing the entropy production loss caused by temperature difference and improving the refrigeration efficiency.

[0028] 2) The present application uses a multi-stage expansion method to output appropriate temperature level of cold energy at intermediate temperature to compensate for these cold losses, avoiding the need to use low-temperature refrigeration capacity to compensate for high-temperature heat loss, thereby saving low-temperature cold energy, making energy utilization more reasonable, improving the overall efficiency of the machine, and achieving lower refrigeration temperature.

[0029] 3) The method of the variable cross-section multi-stage regenerative refrigerator unit of the structural form of the present application can be applied to small and large systems, and to various working substances such as liquid helium, liquid hydrogen, liquid nitrogen, and liquefied methane, and has a wide application prospect.

[0030] 4) The structural scheme in the present application can be used to transform the refrigerator cylinder and piston on the basis of the original refrigeration system, and has low transformation cost and low structural complexity. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram of the intermediate temperature refrigeration capacity utilization system of a four-stage GM refrigerator transformed from a two-stage GM refrigerator according to Embodiment 1 of the present application.

[0032] Figure 2 The figure is a schematic diagram of the intermediate temperature refrigeration capacity utilization system of a three-stage Stirling refrigerator transformed from a one-stage Stirling refrigerator and coupled with a pulse tube refrigerator according to Embodiment 2 of the present application. DETAILED DESCRIPTION

[0033] The present application will be described in detail below with reference to the drawings and specific embodiments. In the present technical scheme, the component models, material names, connection structures, control methods, algorithms, and other features that are not explicitly described are considered to be common technical features disclosed in the prior art.

[0034] The present application increases the number of refrigeration stages of the refrigerator, outputs more refrigeration capacity at different temperature levels, and selects appropriate refrigeration capacity at different temperature levels according to actual needs to perform refrigeration, thereby reducing the entropy production loss caused by temperature difference and improving the refrigeration efficiency. If a multi-stage expansion method is used, the cold loss can be compensated by outputting cold at the intermediate temperature, the cold at the low temperature can be saved, the energy utilization is more reasonable, the overall efficiency can be improved, and a lower refrigeration temperature can be obtained. The method of transforming the original refrigerator has low manufacturing cost and low structural complexity.

[0035] In the present application, the cylinder structure of the cylinder structure module remains unchanged in the length direction, a low-thermal-conductivity insertion unit is added in the cylinder, and the insertion unit is connected with the original cylinder to form a new expansion cavity between the insertion unit and the stepped expansion piston.

[0036] In the present application, the variable cross-section multi-stage regenerative refrigerator unit changes the cross-sectional area of the expansion piston and adds an expansion piston sealing mechanism, so that the expansion stage number of the refrigerator is increased, more refrigeration capacity at different temperature levels can be output, and appropriate refrigeration capacity at different temperature levels can be selected for utilization according to actual needs.

[0037] In the present application, the transmission of cold from the intermediate temperature cold end heat exchanger to the refrigeration capacity utilization module includes pipeline transmission of cooling medium, solid thermal conduction, and gas thermal conduction.

[0038] The regenerative refrigerator unit in the present invention utilizes a regenerator component to alternately store and release heat. This includes GM refrigerators, Solvay refrigerators, Stirling refrigerators, or hybrid structures combining multiple types of refrigerators in a multi-stage coupling. The regenerator is positioned within the expansion piston. The average operating pressure within the regenerative refrigerator module is 0.1 to 3000 times atmospheric pressure (0.01-300 MPa).

[0039] Example 1

[0040] like Figure 1 As shown, the variable cross-section multi-stage expansion regenerative refrigerator used in this embodiment includes: a regenerator, an expansion assembly, and a cylinder insertion unit;

[0041] The cylinder structure maintains a constant cross section along the length direction, and a low-heat-conductivity insert unit (40, 41) is added to the cylinder to form a connection with the original cylinder, forming a new expansion chamber (13, 17, 23, 27) above the insert unit and between the stepped expansion piston.

[0042] The regenerative refrigerator unit includes a compression device 1, a compressor low-pressure air storage tank 2, a compressor cooler and filter device 3, a compressor high-pressure air storage tank 4, a GM type compressor high and low pressure air distribution valve 5, a refrigerator air inlet channel 6, a refrigerator cylinder 7, a first-stage expansion piston 11, a first-stage regenerator 8, a first-stage expansion piston sealing mechanism 9, a gap 10 between the first-stage expansion piston and the cylinder, and a first-stage expansion chamber 13.

[0043] The variable-cross-section multi-stage structure innovatively adds a first-stage expansion piston 16, a first-stage heat regenerator 15, a first-stage expansion piston sealing mechanism 14, a gap 18 between the first-stage expansion piston and the cylinder, a first-stage expansion chamber 17, and a first-stage cold-end heat exchanger 19.

[0044] At the same time, the variable-section multi-stage structure innovatively designs the secondary expansion piston 21, the secondary heat regenerator 22, the secondary expansion piston sealing mechanism 20, the gap 30 between the secondary expansion piston and the cylinder, and the secondary expansion chamber 23.

[0045] Second-stage expansion piston 25 , second-stage regenerator 24 , second-stage expansion piston sealing mechanism 29 , gap 26 between second-stage regenerator and cylinder, second-stage expansion chamber 27 , second-stage cold-end heat exchanger 28 .

[0046] The working process of this embodiment is:

[0047] The system is installed according to the above process, and the gas working substance is filled with working pressure. First, run the compressor 1, and the high-pressure gas from the compressor enters the expander, and the expansion chamber and the regenerator are adiabatically filled with gas. The pressure in the regenerator 8 and the hot chamber increases. When the pressure is balanced, the first-stage expansion piston 11 moves upward, pushing the high-pressure gas entering the hot chamber through the regenerator into the first-stage expansion chamber 13. When the gas passes through the regenerator, heat is released to the filler, and the temperature and pressure of the gas decrease. When the first-stage expansion piston 11 moves to the top of the refrigerator cylinder 7, the inlet valve is closed, a part of the gas enters the first-stage expansion chamber 13 for expansion refrigeration, and another part of the gas enters the first-stage expansion chamber 13 for expansion refrigeration. The first-stage expansion chamber 13 is cooled and enters the first-stage expansion chamber 17 for expansion, obtaining a lower refrigeration temperature than the first stage. At the same time, part of the gas is cooled by the second-stage regenerator 22 and reaches the second-stage expansion chamber 23 for expansion. Part of the gas enters the second-stage expansion chamber 27 through the second-stage regenerator 24 for expansion refrigeration, obtaining a second-stage refrigeration temperature. In the refrigeration system shown in the figure, two stages of different temperatures and refrigeration capacities can be expanded. The refrigeration capacity is introduced through the cold end heat exchange assembly 28 and enters the refrigeration capacity utilization module 31 for utilization. In actual production, appropriate cold end heat exchangers can be selected to introduce cold capacity for refrigeration according to needs.

[0048] Example 2

[0049] As shown in Figure 2 , the variable cross-section multistage expansion regenerative refrigerator used in this embodiment includes a regenerator, an expansion assembly, and an insertion unit of a cylinder.

[0050] The structure of the cylinder keeps the cross-section unchanged along the length direction, and low-thermal-conductivity insertion units 61 and 62 are added in the cylinder to form connections with the original cylinder, and new expansion chambers 13, 33, and 43 are formed between the insertion units and the stepped expansion pistons above the insertion units.

[0051] The regenerative refrigerator unit includes a piston-type compression device 1, a compressor cooler 3, a refrigerator inlet pipeline 6, a refrigerator cylinder 7, a second-stage cold end connecting pipeline 50, a second-stage pulse tube cold end heat exchanger 51, a second-stage pulse tube 52, a second-stage pulse tube hot end heat exchanger 53, a second-stage phase adjustment mechanism 54, a thermal bridge 63 between the second-stage pulse tube hot end heat exchanger and the second-stage expansion piston 11, a first-stage regenerator 8, a first-stage expansion piston sealing mechanism 9, a gap 10 between the first-stage expansion piston and the cylinder, and a first-stage expansion chamber 13.

[0052] The first-stage expansion piston 11, the first-stage regenerator 8, the first-stage expansion piston sealing mechanism 9, the gap 10 between the first-stage expansion piston and the cylinder, and the first-stage expansion chamber 13.

[0053] Expanded secondary expansion piston 41, expanded secondary heat regenerator 48, expanded secondary expansion piston sealing mechanism 49, expanded secondary expansion piston and cylinder gap 40, expanded secondary expansion chamber 43, expanded secondary cold end heat exchanger 42.

[0054] The second-stage regenerator 16 , the gap 20 between the second-stage regenerator and the cylinder, and the second-stage cold-end heat exchanger 24 .

[0055] The working process of this embodiment is:

[0056] Complete the system installation according to the above process and fill it with the working pressure gas. First, run the compressor 1. The high-pressure gas from the compressor enters the expander, adiabatically filling the expansion chamber and regenerator, increasing the pressure in the regenerator 8 and the heat chamber. When the pressure is balanced, the first-stage expansion piston 11 moves upward. The high-pressure gas entering the heat chamber is pushed through the regenerator and cooled by the regenerative filler in the regenerator, entering the first-stage expansion chamber 13, while the pressure is reduced. When the first-stage expansion piston 11 moves to the top of the refrigerator cylinder 7, part of the gas enters the first-stage expansion chamber 13 for expansion and cooling. Another part of the gas enters the expanded first-stage regenerator 38 for further cooling, then enters the expanded first-stage expansion chamber 33 for expansion, achieving a lower refrigeration temperature than the first stage. Another part of the gas continues to cool in the expanded second-stage regenerator 48, then enters the expanded second-stage expansion chamber 43 for expansion, achieving an even lower refrigeration temperature. Similarly, in the illustrated refrigeration system, two stages with different temperatures and cooling capacities can be expanded. The heat then enters the second-stage pulse tube refrigerator, passing through the regenerator, cold-end connecting pipe, pulse tube, and phase-shifting mechanism. The cooling capacity is extracted through the cold-end heat exchange assembly 24. The hot end of the pulse tube and the phase-shifting mechanism are connected to the hot end of the regenerator via a thermal bridge. Precooling by increasing the number of expansion stages reduces entropy generation, improves cooling efficiency, and achieves lower cooling temperatures. In actual production, the appropriate cold-end heat exchanger can be selected to extract the cooling capacity for cooling purposes.

[0057] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A regenerative refrigerator multistage expansion system, characterized by, The invention comprises a compressor device and a regenerative refrigerator device connected to each other, wherein the regenerative refrigerator device comprises a regenerator assembly, an expansion assembly, and a cold end heat exchanger assembly; The expansion assembly includes a multi-stage expansion cylinder, an expansion piston provided in each stage of the expansion cylinder, and a regenerator matched with each stage of the expansion piston, wherein the diameters of the multi-stage expansion pistons decrease in sequence; The lower end of each stage of the expansion piston is provided with a tubular low-thermal-conductivity insertion unit, which matches the diameter and length of the multi-stage expansion pistons with decreasing diameters. In the multi-stage expansion cylinder, a multi-stage expansion piston is added to at least one stage of the expansion cylinder, and an expansion piston sealing mechanism is matched between the insertion unit and each expansion piston, so that the number of refrigeration stages of the refrigerator is increased accordingly; The insertion unit is fixedly connected to the corresponding stage expansion cylinder, and the expansion piston sealing mechanism is sandwiched between the insertion unit and the expansion piston; The expansion piston sealing mechanism is arranged on each level of the expansion piston and the cylinder, or distributed in part or the entire expansion piston area.

2. A regenerative refrigerator multistage expansion system according to claim 1, wherein, The expansion piston sealing mechanism is an elastic sealing ring or a gap-type sealing ring; The space above the insertion unit constitutes an expansion chamber; The diameters of the multi-stage expansion piston decrease from top to bottom, thereby forming an overall stepped expansion piston.

3. The multi-stage expansion system of a regenerative refrigerator according to claim 1, characterized in that: In the one-stage or multi-stage expansion structure of the multi-stage expansion system of the regenerative refrigerator: An expansion piston is added to at least one expansion structure, while no expansion piston is added to the expansion structures of other levels.

4. A regenerative refrigerator multistage expansion system according to claim 1, wherein The regenerative refrigerator device is a refrigerator that uses a regenerator component to achieve alternating storage and release of heat, wherein the regenerator component is placed in the expansion component.

5. A regenerative refrigerator multistage expansion system according to claim 3, wherein, The refrigerator includes a hybrid structure in which one or more refrigerators selected from the group consisting of a GM refrigerator, a Solvay refrigerator, a Stirling refrigerator, and a Villemire (VM) refrigerator are coupled in multiple stages, or a hybrid structure in which one of the refrigerators selected from the group consisting of a GM refrigerator, a Solvay refrigerator, a Stirling refrigerator, and a Villemire (VM) refrigerator is coupled with a pulse tube refrigerator.

6. A regenerative refrigerator multistage expansion system according to claim 1, wherein The average working pressure in the multi-stage expansion system of the regenerative refrigerator is 0.1 to 3000 times the atmospheric pressure.

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