GM pulse tube refrigerator and pulse tube refrigerator shunting method

Abstract

The GM pulse tube refrigerator comprises a helium compressor, a first-stage regenerator, a second-stage regenerator, a second-stage pulse tube and a first-stage pulse tube, the helium compressor is communicated with the first-stage regenerator, and the GM pulse tube refrigerator is characterized in that a flow dividing structure is arranged at the connecting end of the first-stage regenerator and the second-stage regenerator; a first-stage air channel and a second-stage air channel are arranged on the flow dividing structure, and the first-stage regenerator communicates with the first-stage pulse tube through the first-stage air channel. According to the GM pulse tube refrigerator, the gas flow dividing structure is arranged in the cold end of the GM pulse tube refrigerator, the first-stage gas channel and the second-stage gas channel are arranged, the amount of helium entering the first-stage pulse tube and the second-stage pulse tube is configured by replacing the flow dividing structure with different effective area ratios of the first-stage gas channel and the second-stage gas channel, and first-stage refrigeration and second-stage precooling are sufficient; therefore, the air quantity is reasonably distributed, the first-stage refrigeration performance and the second-stage refrigeration performance reach the expectation, the ideal flow is obtained at the deep hypothermia, and the cooling capacity output stability is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of regenerative GM pulse tube cryocooler, and more particularly to a GM pulse tube cryocooler and a pulse tube cryocooler flow distribution method. BACKGROUND

[0002] The pulse tube cryocooler was successfully developed in the 1960s. Compared with the GM (Gifford-McMahon) cryocooler and the Stirling cryocooler, the pulse tube cryocooler has no moving parts at low temperature, is simple in structure, reliable in operation, and has 1 to 2 orders of magnitude lower vibration than the other two types. Therefore, the pulse tube cryocooler has been widely used in the fields of dilution refrigerators, infrared devices, superconducting magnet cooling, etc., among which the two-stage bidirectional inlet type pulse tube cryocooler is the most widely used.

[0003] The two-stage pulse tube cryocooler is composed of a compressor, a first-stage regenerator, a first-stage cold-end heat exchanger, a first-stage pulse tube, a second-stage regenerator, and a second-stage pulse tube. According to the spatial arrangement of the pulse tube and the regenerator, the two-stage pulse tube cryocooler can be divided into the following three types: U-shaped arrangement, straight-line arrangement, and coaxial arrangement.

[0004] The straight-line type pulse tube cryocooler is limited in development due to the limitation of the set spatial size; the coaxial type pulse tube cryocooler has a compact structure, but the high-pressure gas provided by the compressor will bring gas flow loss through a 180° sharp turn, affecting the performance of the cryocooler and reducing the refrigeration efficiency. In engineering, the regenerator and the pulse tube of the pulse tube cryocooler are mostly arranged in a U shape.

[0005] When the pulse tube cryocooler adopts the U-shaped arrangement, the first-stage and second-stage flow distribution scheme is that a part of helium gas after passing through the first-stage regenerator enters a U-shaped tube for gas guiding, and the U-shaped tube is connected with the first-stage regenerator and the first-stage pulse tube. A part of the quantitatively high-pressure helium gas provided by the compressor is distributed to the first-stage pulse tube after passing through the first-stage regenerator, and the other part of the helium gas directly enters the second-stage regenerator and the second-stage pulse tube. The gas in the pulse tube obtains cold energy through the processes of adiabatic compression and adiabatic expansion to achieve the refrigeration requirement. The distribution of the helium gas flow provided by the compressor depends on the resistance distribution of the U-shaped tube and the second-stage regenerator. The U-shaped tube has a complex structure and is integrated in the cryocooler, so it cannot be replaced. Moreover, the flow ratio of the helium gas in the first-stage and second-stage pulse tubes is fixed and cannot be changed, so the pre-cooling effect of the first-stage and second-stage cannot be achieved.

[0006] The pulse tube cryocooler in the prior art has no moving parts at the cold end, and the flow size of the gas entering the pulse tube cannot be adjusted. The pulse tube cryocooler relies entirely on the adjustment of the mass flow and the pressure wave to form the refrigeration capacity during operation. If the adjustment is made at the hot end, the intervention of the gas cylinder distribution at the cold end is limited, and the quantification cannot be achieved. In actual operation, the refrigeration performance distribution of the first-stage and second-stage is often unbalanced. SUMMARY

[0007] The technical problem to be solved by the present application is how to actively intervene in air flow distribution according to target requirements to achieve expected primary and secondary refrigeration performance.

[0008] The present application solves the above technical problems by the following technical means: a GM pulse tube refrigerator, comprising a helium compressor, a primary cold accumulator, a secondary cold accumulator, a secondary pulse tube and a primary pulse tube, the helium compressor being in communication with the primary cold accumulator, a shunt structure being arranged at the connection end of the primary cold accumulator and the secondary cold accumulator, the shunt structure being provided with a primary gas passage and a secondary gas passage, the primary cold accumulator being in communication with the primary pulse tube through the primary gas passage, the primary cold accumulator being in communication with the secondary cold accumulator through the secondary gas passage, the secondary cold accumulator being in communication with the secondary pulse tube, gas cylinders being arranged outside the primary cold accumulator, the secondary cold accumulator, the secondary pulse tube and the primary pulse tube, the shunt structure being detachably fixed at the connection end of the gas cylinder outside the primary cold accumulator and the gas cylinder outside the secondary cold accumulator, and the helium amount entering the primary pulse tube and the secondary pulse tube being effectively configured by replacing the shunt structure with different effective area ratios of the primary gas passage and the secondary gas passage, so that the primary refrigeration and the secondary precooling are fully achieved.

[0009] As a preferred technical solution, the secondary gas passage causes the helium amount entering the secondary cold accumulator from the primary cold accumulator to account for 20% to 50% of the total helium amount.

[0010] As a preferred technical solution, a gap is left between the shunt structure and the inner wall of the gas cylinder of the primary cold accumulator in the circumferential direction and a connection hole is formed, a first step surface is arranged at the end of the shunt structure facing the secondary cold accumulator, the first step surface causes the shunt structure and the inner wall of the gas cylinder to form an annular passage in communication with the connection hole, the connection hole and the annular passage form the primary gas passage, a center through hole is arranged at the center of the shunt structure, and the center through hole forms the secondary gas passage.

[0011] As a preferred technical solution, a first step surface is arranged at the end of the shunt structure facing the secondary cold accumulator, the first step surface causes the shunt structure and the inner wall of the gas cylinder to form an annular passage, at least one connection hole extending from the top of the shunt structure to the first step surface of the shunt structure and in communication with the annular passage is arranged on the shunt structure, the connection hole and the annular passage form the primary gas passage, a center through hole is arranged at the center of the shunt structure, and the center through hole forms the secondary gas passage.

[0012] As a preferred technical solution, a second step surface is arranged at the end of the shunt structure facing the secondary cold accumulator and matched with the end of the gas cylinder of the secondary cold accumulator.

[0013] As a preferred technical solution, a sealing ring is arranged at the connection surface of the shunt structure and the gas cylinder of the secondary cold accumulator and / or the gas cylinder of the primary cold accumulator.

[0014] As a preferred technical solution, a rotary valve is further arranged on the connection pipeline of the helium compressor and the primary cold accumulator, and one phase-adjusting gas reservoir is connected to each of the primary pulse tube and the secondary pulse tube.

[0015] As a preferred technical solution, the first-stage accumulator is communicated with the first-stage pulse tube through a first connecting pipe, and the second-stage accumulator is communicated with the second-stage pulse tube through a second connecting pipe, and the first connecting pipe and the second connecting pipe are straight pipes.

[0016] As a preferred technical solution, the sealing ring is made of polytetrafluoroethylene.

[0017] The application also provides a pulse tube refrigerator shunting method, which adopts a GM pulse tube refrigerator, and sets an effective area ratio of a first-stage gas passage to a second-stage gas passage to distribute the amount of helium entering the first-stage pulse tube and the second-stage pulse tube, so that the amount of helium entering the second-stage accumulator from the first-stage accumulator accounts for 20% to 50% of the total amount of helium.

[0018] The application has the following beneficial effects: (1) In the application, the gas shunting structure is arranged in the cold end of the GM pulse tube refrigerator, the first-stage gas passage and the second-stage gas passage are arranged, the amount of helium entering the first-stage pulse tube and the second-stage pulse tube is distributed by replacing the shunting structure configuration of different effective area ratios of the first-stage gas passage to the second-stage gas passage, and the first-stage refrigeration and the second-stage precooling are fully achieved, so that the gas amount is reasonably distributed, the performance of the first-stage and the second-stage refrigeration reaches the expectation, the ideal flow size is obtained at deep low temperature, the stability of the cold energy output is ensured, the shunting structure is detachably fixed in the cold end of the refrigerator, the amount of helium in the first-stage and the second-stage pulse tubes provided by the compressor is distributed, and the compactness of the pulse tube refrigerator is improved due to the fact that the shunting structure is detachable and does not occupy extra space, and the influence of the cold energy deterioration caused by shunting is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The pulse tube refrigerator structure schematic diagram provided for the embodiment 1 of the application; Figure 2 The shunting structure schematic diagram provided for the embodiment 1 of the application; Figure 3 The shunting structure top view structure schematic diagram provided for the embodiment 1 of the application; Figure 4 The shunting structure schematic diagram provided for the embodiment 2 of the application; Figure 5 The shunting structure top view structure schematic diagram provided for the embodiment 2 of the application; Figure 6 The influence schematic diagram of the first-stage and the second-stage gas amount ratio on the refrigeration performance under the simulation condition provided for the embodiment 1 of the application; Figure 7 The influence schematic diagram of the first-stage and the second-stage gas amount ratio on the refrigeration performance under the experimental condition provided for the embodiment 1 of the application; Figure 8 The boundary condition diagram of the simulation and the experiment provided for the embodiment 1 of the application; Fig. 1 is a phase-adjusting gas reservoir; Fig. 2 is a primary pulse tube; Fig. 3 is a secondary pulse tube; Fig. 4 is a first connecting tube; Fig. 5 is a helium compressor; Fig. 6 is a rotary valve; Fig. 7 is a primary cold accumulator; Fig. 8 is a flow splitting structure; 81 is a primary gas passage; 811 is a connecting hole; 812 is an annular passage; 82 is a secondary gas passage; 83 is a sealing ring; 84 is a central through hole; Fig. 9 is a secondary cold accumulator; and Fig. 10 is a second connecting tube. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0021] Embodiment 1 In this embodiment, an active intervention measure is added in the GM pulse tube refrigerator, i.e. a gas flow splitting structure 8 is arranged at the cold end of the pulse tube refrigerator, and by replacing different flow splitting structures 8, i.e. flow splitting structures 8 with different effective area ratios, the gas flow is reasonably distributed to achieve the expected primary and secondary refrigeration performance, so as to ensure that the ideal flow size is obtained at deep low temperature.

[0022] It should be noted that the active intervention measure here refers to replacing the flow splitting structure 8 with different effective area ratios to achieve active intervention for adjusting the gas flow distribution, so as to achieve the expected primary and secondary refrigeration performance.

[0023] Compared with the pulse tube refrigerator in the prior art, which adjusts the phase relationship between the pressure wave and the mass flow at the hot end through a gas distribution valve, the intervention on the cylinder distribution at the cold end is limited, and the pulse tube refrigerator cannot play a quantitative role. The refrigeration performance of the pulse tube refrigerator is limited when it is manufactured.

[0024] Meanwhile, compared with the pulse tube refrigerator with a U-shaped tube in the prior art, the flow splitting structure 8 in this embodiment is detachable, and the adjustment can be realized only by replacing the flow splitting structure 8, without the need to manufacture a complete pulse tube refrigerator, thereby greatly reducing the cost.

[0025] Reference is made to Figure 1 , Figure 2The application discloses a GM pulse tube refrigerator, which comprises a helium compressor 5, a first-stage cold accumulator 7, a second-stage cold accumulator 9, a second-stage pulse tube 3, a first-stage pulse tube 2 and a flow distribution structure 8, the helium compressor 5 is communicated with the first-stage cold accumulator 7, the first-stage cold accumulator 7 is provided with the flow distribution structure 8 at a connecting end of the second-stage cold accumulator 9, the flow distribution structure 8 is provided with a first-stage gas passage 81 and a second-stage gas passage 82, the first-stage cold accumulator 7 is communicated with the first-stage pulse tube 2 through the first-stage gas passage 81, the first-stage cold accumulator 7 is communicated with the second-stage cold accumulator 9 through the second-stage gas passage 82, the second-stage cold accumulator 9 is communicated with the second-stage pulse tube 3, and the effective area ratio of the first-stage gas passage 81 to the second-stage gas passage 82 is 8:2 or 7:3 or 6:4 or 5:5, so that the helium content ratio entering the second-stage cold accumulator 9 is about 20% to 50%, and 20% to 50% is the optimal value of the gas volume ratio of the second-stage cold accumulator 9. Referring to Figure 6 , Sage is used for simulation in the embodiment, the pulse tube refrigerator adopts a gas-coupled pulse tube refrigerator cylinder, and the first-stage and second-stage gas volume distribution ratio will affect the refrigerating capacity generated by the first-stage and second-stage of the final refrigerator; the compressor gas mass flow is simulated to be kept unchanged at 6 g / s, and the first-stage and second-stage gas volume distribution ratio is changed. As shown in Figure 6 , with the gradual increase of the second-stage gas volume ratio, the first-stage refrigerating capacity gradually increases, but the second-stage refrigerating capacity presents a relatively small influence when the second-stage gas volume ratio is less than 60%, and rapidly decreases when the second-stage gas volume ratio exceeds 60%; the reason for the phenomenon is that the second-stage system mass flow demand of the refrigerator is low, the refrigerating capacity of about 1.7 W can be generated when the second-stage gas volume ratio is 20% to 50%, and the performance is deteriorated due to the increase of the second-stage regenerative loss when the second-stage gas volume ratio exceeds 50%; meanwhile, the first-stage regenerative loss is reduced due to the gradual decrease of the first-stage mass flow, and the first-stage refrigerating capacity is gradually increased.

[0026] The boundary conditions of simulation and experiment are shown in Figure 8 , the cold storage materials are stainless steel wire mesh, copper wire mesh, lead ball, fire copper, GOS (low-temperature material) and the like.

[0027] The second-stage system mass flow demand of the refrigerator is low, simulation shows that the refrigerating capacity of about 1.7 W can be generated when the second-stage gas volume ratio is 20% to 50%, and the performance is deteriorated due to the increase of the second-stage regenerative loss when the second-stage gas volume ratio exceeds 50%; meanwhile, the first-stage regenerative loss is reduced due to the gradual decrease of the first-stage mass flow, and the first-stage refrigerating capacity is gradually increased.

[0028] The first-stage and second-stage refrigerating capacity experimental data are shown in Figure 7 by adjusting the porosity.

[0029] Referring to Figure 6 , Figure 7 , the experimental data are generally lower than the simulation data, because the simulation data ignore part of the heat loss and the like in actual operation, and the simulation data belong to an ideal state. Meanwhile, the application side of the refrigeration unit has minimum requirements for the secondary cooling capacity of the refrigeration unit, which requires precooling some key gases, and also has limitations on the required system power consumption. Therefore, the primary cooling capacity is not necessarily better the larger it is, and it needs to be matched with the customer's needs. Based on both simulation and experimental data, a secondary gas volume ratio of 20% to 50% represents the most reasonable design range.

[0030] It should be noted that the effective area ratio of the primary air passage 81 to the secondary air passage 82 can be the ratio of the cross-sectional area of ​​the primary air passage 81 to the cross-sectional area of ​​the secondary air passage 82. See Figure 2 , Figure 3 The high and low pressure helium gas supplied by the helium compressor 5 passes through the first-stage accumulator 7 and then to the diversion structure 8. The diversion structure 8 divides the helium gas into two gas passages, namely the primary gas passage 81 and the secondary gas passage 82. One of them is a gap passage formed by the gap fit between the diversion structure and the outer wall of the cylinder. It should be noted that cylinders are provided on the outside of the first-stage accumulator 7, the second-stage accumulator 9, the second-stage pulse tube 3, and the first-stage pulse tube 2. In this embodiment, the cylinder refers to the cylinder body that is vented, and the cylinder body can be a stainless steel pipe. The flow divider structure 8 controls the flow ratio of high-pressure helium in the primary pulse tube 2 and the secondary pulse tube 3. It is a key structure that affects the required cooling capacity generated by the primary and secondary stages of the pulse tube refrigerator. Furthermore, the size design of the flow divider structure 8 cannot exceed the set space size requirements, otherwise it will occupy the cold storage space and affect the efficiency of the refrigerator. In this embodiment, the space size refers to the thickness of the flow divider structure 8.

[0031] In this embodiment, the optimal ratio of the primary gas channel 81 and the secondary gas channel 82 exists because the cooling performance generated by the helium entering the primary pulse tube 2 will pre-cool the helium in the secondary accumulator 9. If the gas volume ratio in the primary pulse tube 2 is too small, the pre-cooling effect will be insufficient, and the primary cooling performance will not meet expectations. At the same time, the axial thermal conductivity of the helium entering the primary accumulator 7 and the secondary accumulator 9 will increase, thereby deteriorating the performance of the secondary refrigerator. On the other hand, if the gas volume ratio in the primary pulse tube 2 is too large, the primary cooling performance will meet expectations and the pre-cooling will be good, but the gas volume in the secondary pulse tube 3 will be too low, and the secondary cooling performance will not meet expectations.

[0032] The gas in the primary gas channel 81 reaches the primary pulse tube 2 and undergoes adiabatic compression and expansion. Another path leads the high-pressure gas directly to the secondary accumulator 9 through the secondary gas channel 82. This gas exchanges heat fully with the heat exchange material in the secondary accumulator 9 and then reaches the secondary pulse tube 3. The high-pressure gas in the secondary pulse tube 3 undergoes compression and expansion similar to the gas in the primary pulse tube 2, ultimately generating cooling capacity.

[0033] See Figure 1The first-stage cold storage 7 is connected to the first-stage pulse tube 2 through the first connecting pipe 4, and the second-stage cold storage 9 is connected to the second-stage pulse tube 3 through the second connecting pipe 10. In this embodiment, both the first connecting pipe 4 and the second connecting pipe 10 are straight pipes. The flow divider structure 8 has a first step surface and a second step surface at one end facing the secondary accumulator 9. The first step surface reduces the diameter of the flow divider structure 8 and forms an annular channel 812 between it and the inner wall of the cylinder of the primary accumulator 7. The second step surface is adapted to the cylinder end of the secondary accumulator 9.

[0034] See Figure 2 The bottom of the diversion structure 8 is provided with two protrusions connected in sequence. The two protrusions are the first protrusion and the second protrusion. One end of the first protrusion is fixedly connected to the diversion structure 8, and the other end of the first protrusion is fixedly connected to the second protrusion. In this embodiment, the diversion structure 8, the first protrusion, and the second protrusion are integrally formed. The connection surface between the diversion structure 8 and the first protrusion forms a first stepped surface, and the connection surface between the first protrusion and the second protrusion forms a second stepped surface. The circumferential direction of the first protrusion forms an annular channel 812 with the inner wall of the cylinder of the first-stage accumulator 7. The circumferential direction of the second protrusion is fixedly connected to the inner wall of the cylinder of the second-stage accumulator 9 and is sealed to it.

[0035] In this embodiment, the primary air passage 81 of the diversion structure 8 includes a gap between the diversion structure 8 and the cylinder of the primary accumulator 7, and an annular channel 812. A gap is left between the diversion structure 8 and the inner wall of the cylinder of the primary accumulator 7 in the circumferential direction. This annular gap forms a connecting hole 811, which communicates with the annular channel 812. The annular channel 812 communicates with the first connecting pipe 4. A central through hole 84 is provided at the center of the diversion structure 8. The advantage of opening the central through hole 84 at the center of the diversion structure 8 is that the temperature is consistent at the same radial distance from the central hole during secondary cooling; at the same time, opening the hole at the center reduces machining costs. The primary accumulator 7 is connected to the secondary accumulator 9 through the secondary air passage 82; the second step surface of the diversion structure 8 and the cylinder connection end face of the secondary accumulator 9 are provided with a sealing ring 83. The function of the sealing ring 83 is to isolate the cross-flow effect between the primary air passage 81 and the secondary air passage 82, and to ensure that the air volume distribution ratio meets the design requirements. It should be noted that, in order to ensure that the sealing ring 83 can be used at low temperatures, the sealing ring 83 in this embodiment is a low-temperature wear-resistant sealing ring made of polytetrafluoroethylene filler, such as the low-temperature wear-resistant sealing ring in the patent document with patent publication number CN203189918U. Of course, this type of sealing ring 83 is a commercially available part.

[0036] It should be noted that, compared to the existing technology where the pressure wave and mass flow phase relationship is adjusted by the gas distribution valve at the hot end of the refrigeration unit, the intervention of the cylinder distribution at the cold end is limited and cannot play a quantitative role. In this embodiment, the flow splitting structure 8 is installed inside the refrigeration unit and can effectively intervene in the gas distribution.

[0037] See Figure 1 A rotary valve 6 is also provided on the connecting pipeline between the helium compressor 5 and the first-stage accumulator 7. The first-stage pulse pipe 2 and the second-stage pulse pipe 3 are both connected to a phase-adjusting gas reservoir 1. The phase-adjusting gas reservoir 1 is used to adjust the phase angle of the pressure wave and mass flow of the helium gas input from the compressor direction.

[0038] The diversion structure 8 is detachably fixed inside the cylinder of the primary accumulator 7. In this embodiment, the diversion structure 8 is connected and fastened to the cylinder of the primary accumulator 7 by bolts, or the diversion structure 8 is threadedly fixed to the cylinder of the primary accumulator 7.

[0039] Diversion method for pulse tube refrigerators: By adjusting the effective diameter area ratio of the primary gas channel 81 and the secondary gas channel 82 on the diversion structure 8, the amount of helium entering the primary pulse tube 2 and the secondary pulse tube 3 is adjusted, thereby ensuring sufficient precooling and achieving the expected primary and secondary cooling performance to meet the application requirements.

[0040] It should be noted that during actual processing, the drawings require the single-sided gap of the annular channel 812 to be between 0.5mm and 3mm. The machining error of the inner and outer rings of the flow divider structure 8 and each cylinder is at the micrometer level. Currently, domestic machining manufacturers can meet this machining error and it is relatively easy to control. At the same time, this error is already at the level required for precision instruments, with an error ratio of about 0.5%, and its impact on actual assembly can be ignored.

[0041] Example 2 See Figure 4 , Figure 5 The difference between this embodiment and embodiment 1 is that the structure of the primary air channel 81 in this embodiment is different from that in embodiment 1. The primary air channel 81 in embodiment 1 has a fixed size, and the effective area ratio of the primary air channel 81 to the secondary air channel 82 can only be adjusted by changing the diameter of the diversion structure 8. In this embodiment, the primary air channel 81 includes a connecting hole 811 and an annular channel 812. By increasing the number of openings in the connecting hole 811, the effective area of ​​the primary air channel 81 can be increased. A connection hole 811 is provided on the diversion structure 8. The connection hole 811 extends from the top of the diversion structure 8 to the first step surface of the diversion structure 8 and communicates with the annular channel 812. The first-stage cold storage 7 is connected to the annular channel 812 and the first connecting pipe 4 through the connection hole 811. In this embodiment, four connecting holes 811 are provided, all of which are straight holes. Of course, they can also be curved holes or irregularly shaped holes. The distribution ratio of helium gas between the first and second stages depends on the ratio of the total cross-sectional area formed by the total number of connecting holes 811 in the diversion structure 8 to the cross-sectional area of ​​the gas vent of the central through hole 84. Therefore, the flow splitting structure 8 in this embodiment can not only distribute the amount of helium gas provided by the helium compressor 5 to the primary pulse tube 2 and the secondary pulse tube 3, but also the flow splitting structure 8 is designed to be flexible, detachable and does not occupy extra space, which will improve the compactness of the pulse tube refrigerator and reduce the impact of cooling capacity deterioration caused by flow splitting.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A GM pulse tube refrigerator, comprising a helium compressor, a primary accumulator, a secondary accumulator, a secondary pulse tube, and a primary pulse tube, wherein the helium compressor is connected to the primary accumulator, characterized in that, The connection between the primary and secondary cold accumulators is equipped with a flow-dividing structure, which includes a primary gas channel and a secondary gas channel. The primary cold accumulator is connected to the primary pulse tube through the primary gas channel, and the primary cold accumulator is connected to the secondary cold accumulator through the secondary gas channel. The secondary cold accumulator is connected to the secondary pulse tube. Cylinders are installed outside the primary cold accumulator, the secondary cold accumulator, the secondary pulse tube, and the primary pulse tube. The flow-dividing structure can be detachably fixed at the connection between the cylinders outside the primary cold accumulator and the cylinders outside the secondary cold accumulator. By changing the flow-dividing structure with different effective area ratios of the primary and secondary gas channels, the amount of helium entering the primary and secondary pulse tubes can be configured, thus ensuring sufficient primary refrigeration and secondary precooling.

2. The GM pulse tube refrigerator according to claim 1, characterized in that, The secondary gas passage results in the helium content entering the secondary accumulator from the primary accumulator being 20% ​​to 50% of the total helium volume.

3. The GM pulse tube refrigerator according to claim 1, characterized in that, A gap is left between the circumferential distribution structure and the inner wall of the cylinder of the first-stage accumulator, forming a connection hole. The end of the distribution structure facing the second-stage accumulator is provided with a first stepped surface. The first stepped surface makes the distribution structure and the inner wall of the cylinder form an annular channel that communicates with the connection hole. The connection hole and the annular channel form a first-stage air passage. A central through hole is opened at the center of the distribution structure, forming a second-stage air passage.

4. The GM pulse tube refrigerator according to claim 1, characterized in that, The flow divider structure has a first stepped surface at one end facing the secondary accumulator. The first stepped surface forms an annular channel between the flow divider structure and the cylinder inner wall. The flow divider structure has at least one connecting hole that extends from the top of the flow divider structure to the first stepped surface of the flow divider structure and communicates with the annular channel. The connecting hole and the annular channel form a primary air passage. A central through hole is provided at the center of the flow divider structure, and the central through hole forms a secondary air passage.

5. A GM pulse tube refrigerator according to claim 3 or 4, characterized in that, The flow divider structure has a second stepped surface at one end facing the secondary accumulator that matches the cylinder end of the secondary accumulator.

6. A GM pulse tube refrigerator according to claim 1, characterized in that, A sealing ring is provided at the connection surface between the split structure and the cylinder of the secondary accumulator and / or the cylinder of the primary accumulator.

7. A GM pulse tube refrigerator according to claim 1, characterized in that, A rotary valve is also installed on the connecting pipeline between the helium compressor and the first-stage accumulator. Both the first-stage and second-stage pulse pipes are connected to a phase-adjusting gas storage tank.

8. A GM pulse tube refrigerator according to claim 1, characterized in that, The first-stage cold accumulator is connected to the first-stage pulse tube via a first connecting pipe, and the second-stage cold accumulator is connected to the second-stage pulse tube via a second connecting pipe. Both the first and second connecting pipes are straight pipes.

9. A GM pulse tube refrigerator according to claim 1, characterized in that, The sealing ring is made of polytetrafluoroethylene.

10. A method for diverting flow in a pulse tube refrigerator, characterized in that, Using the GM pulse tube refrigerator as described in any one of claims 1-9, the amount of helium entering the first-stage and second-stage pulse tubes is configured by changing the effective area ratio of the first-stage and second-stage gas channels in the split structure, so that the helium content entering the second-stage accumulator from the first-stage accumulator accounts for 20% to 50% of the total helium volume.

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