A GM pulse tube refrigerator and a pulse tube refrigerator diversion method

Abstract

This invention discloses a GM pulse tube refrigerator and a flow-splitting method for the pulse tube refrigerator, comprising a helium compressor, a primary accumulator, a secondary accumulator, a secondary pulse tube, and a primary pulse tube. The helium compressor is connected to the primary accumulator. The key feature is that a flow-splitting structure is provided at the connection end between the primary and secondary accumulators, with a primary gas channel and a secondary gas channel on the flow-splitting structure. The primary accumulator is connected to the primary pulse tube through the primary gas channel. In this invention, by setting a gas flow-splitting structure in the cold end of the GM pulse tube refrigerator, and by setting primary and secondary gas channels, and by changing the effective area ratio of the primary and secondary gas channels, the amount of helium entering the primary and secondary pulse tubes is configured, ensuring sufficient primary cooling and secondary pre-cooling. This rationally distributes the gas volume to achieve the expected primary and secondary cooling performance, ensuring ideal flow rates at deep cryogenic temperatures and guaranteeing stable cooling output.

Description

Technical Field

[0001] This invention relates to the field of regenerative GM pulse tube refrigerator technology, and more specifically to a GM pulse tube refrigerator and a pulse tube refrigerator diversion method. Background Technology

[0002] In the 1960s, pulse tube refrigerators were successfully developed. Compared with GM (Gifford-McMahon) refrigerators and Stirling refrigerators, pulse tube refrigerators have no moving parts at low temperatures, resulting in a simple structure and reliable operation. Furthermore, the vibration generated by pulse tube refrigerators is one to two orders of magnitude lower than that of the other two types. Therefore, pulse tube refrigerators have been widely used in dilution refrigerators, infrared devices, and superconducting magnet cooling, among which the two-stage bidirectional air intake pulse tube refrigerator is the most widely used.

[0003] A two-stage pulse tube refrigerator consists of a compressor, a first-stage accumulator, a first-stage cold-end heat exchanger, a first-stage pulse tube, a second-stage accumulator, and a second-stage pulse tube. Based on the spatial arrangement of the pulse tubes and accumulators, two-stage pulse tube refrigerators can be divided into the following three types: U-shaped arrangement, linear arrangement, and coaxial arrangement.

[0004] The development of linear pulse tube refrigerators is limited by the spatial size constraints. Although coaxial pulse tube refrigerators have a compact structure, the high-pressure gas supplied by the compressor will cause gas flow loss after a 180° sharp turn, which will affect the performance of the refrigerator and result in low refrigeration efficiency. In engineering, the regenerator and pulse tube of pulse tube refrigerators are mostly arranged in a U-shape.

[0005] When a pulse tube refrigerator adopts a U-shaped arrangement, its primary and secondary flow splitting scheme involves helium gas passing through a primary accumulator, with a portion entering an external U-tube for gas guidance. The U-tube connects the primary accumulator and the primary pulse tube. A fixed amount of high-pressure helium gas supplied by the compressor passes through the primary accumulator, with a portion of the gas splitting to the primary pulse tube, while the remaining portion directly enters the secondary regenerator and then the secondary pulse tube. The gas in the pulse tube undergoes adiabatic compression and expansion processes to obtain cooling capacity, thus fulfilling the refrigeration requirement. The helium flow distribution provided by the compressor depends on the resistance distribution of the U-tube and the secondary regenerator. The U-tube structure is complex and uses an integrated design, making it irreplaceable once integrated into the refrigerator. Furthermore, the helium flow ratio between the primary and secondary pulse tubes is fixed and cannot be changed, thus failing to achieve the primary and secondary pre-cooling effect.

[0006] In existing pulse tube refrigerators, there are no moving parts at the cold end, so the flow rate of gas entering the pulse tube cannot be adjusted. When the pulse tube refrigerator is running, it relies entirely on the regulation of mass flow and pressure waves to generate cooling capacity. If the adjustment is made at the hot end, its intervention in the cylinder distribution at the cold end is limited and cannot play a quantitative role. In actual operation, there is often an imbalance in the distribution of primary and secondary cooling performance. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to actively intervene in the airflow distribution according to the target requirements in order to achieve the expected primary and secondary cooling performance.

[0008] This invention solves the above-mentioned technical problems through the following technical means: a GM pulse tube refrigerator, comprising a helium compressor, a primary accumulator, a secondary accumulator, a secondary pulse tube, and a primary pulse tube. The helium compressor is connected to the primary accumulator. The connection end between the primary and secondary accumulators is provided with a flow-dividing structure. The flow-dividing structure is provided with a primary gas channel and a secondary gas channel. The primary accumulator is connected to the primary pulse tube through the primary gas channel, the primary accumulator is connected to the secondary accumulator through the secondary gas channel, and the secondary accumulator is connected to the secondary pulse tube. Cylinders are provided outside the primary accumulator, the secondary accumulator, the secondary pulse tube, and the primary pulse tube. The flow-dividing structure is detachably fixed at the connection end between the cylinder outside the primary accumulator and the cylinder outside the secondary 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 is configured, resulting in sufficient primary cooling and secondary pre-cooling.

[0009] As a preferred technical solution, the secondary gas channel results in the helium content entering the secondary accumulator from the primary accumulator being 20% ​​to 50% of the total helium volume.

[0010] As a preferred technical solution, a gap is left between the circumferential distribution structure and the inner wall of the cylinder of the first-stage accumulator to form a connecting 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 connecting hole. The connecting hole and the annular channel form a first-stage air passage. A central through hole is opened at the center of the distribution structure, and the central through hole forms a second-stage air passage.

[0011] As a preferred technical solution, the end of the flow splitting structure facing the secondary accumulator is provided with a first stepped surface. The first stepped surface forms an annular channel between the flow splitting structure and the inner wall of the cylinder. At least one connecting hole is provided on the flow splitting structure, extending from the top of the flow splitting structure to the first stepped surface of the flow splitting structure and communicating 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 splitting structure, and the central through hole forms a secondary air passage.

[0012] As a preferred technical solution, the end of the diversion structure facing the secondary accumulator is provided with a second stepped surface that is adapted to the cylinder end of the secondary accumulator.

[0013] As a preferred technical solution, the connection surfaces of the flow divider structure with the cylinders of the secondary accumulator and / or the cylinders of the primary accumulator are provided with sealing rings.

[0014] As a preferred technical solution, a rotary valve is also provided on the connecting pipeline between the helium compressor and the first-stage accumulator, and both the first-stage pulse pipe and the second-stage pulse pipe are connected to a phase-adjusting gas storage tank.

[0015] As a preferred technical solution, the first-stage cold accumulator is connected to the first-stage pulse tube through the first connecting pipe, and the second-stage cold accumulator is connected to the second-stage pulse tube through the second connecting pipe. Both 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 present invention also provides a flow distribution method for a pulse tube refrigerator, which uses a GM pulse tube refrigerator and sets the effective area ratio of the primary gas channel and the secondary gas channel to distribute the amount of helium entering the primary pulse tube and the secondary pulse tube, so that the helium content entering the secondary accumulator from the primary accumulator accounts for 20% to 50% of the total helium volume.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) In this invention, a gas splitting structure is set in the cold end of the GM pulse tube refrigerator, and a primary gas channel and a secondary gas channel are set. By changing the splitting structure with different effective area ratios of the primary and secondary gas channels, the amount of helium entering the primary and secondary pulse tubes is configured, and the primary refrigeration and secondary pre-cooling are fully achieved. Thus, the gas volume is reasonably allocated to achieve the expected primary and secondary refrigeration performance, so as to ensure that the ideal flow rate is obtained at deep low temperature and to ensure the stability of the cold output. By fixing the splitting structure detachably to the cold end of the refrigerator, not only can the amount of helium provided by the compressor in the primary and secondary pulse tubes be allocated, but also the compactness of the pulse tube refrigerator is improved and the cold output deterioration caused by the splitting is reduced because the splitting structure is detachable and does not occupy extra space. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the pulse tube refrigerator structure provided in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the flow splitting structure provided in Embodiment 1 of the present invention;

[0022] Figure 3 This is a top view schematic diagram of the diversion structure provided in Embodiment 1 of the present invention;

[0023] Figure 4 This is a schematic diagram of the flow splitting structure provided in Embodiment 2 of the present invention;

[0024] Figure 5 This is a top view schematic diagram of the diversion structure provided in Embodiment 2 of the present invention;

[0025] Figure 6 This is a schematic diagram illustrating the effect of the primary and secondary gas volume ratio on refrigeration performance under simulation conditions provided in Embodiment 1 of the present invention.

[0026] Figure 7This is a schematic diagram illustrating the effect of the primary and secondary gas volume ratio on refrigeration performance under experimental conditions provided in Embodiment 1 of the present invention.

[0027] Figure 8 Boundary condition diagrams for simulation and experimentation provided in Embodiment 1 of the present invention;

[0028] Reference numerals: 1. Phase-adjusting gas reservoir; 2. Primary pulse tube; 3. Secondary pulse tube; 4. First connecting pipe; 5. Helium compressor; 6. Rotary valve; 7. Primary accumulator; 8. Flow splitting structure; 81. Primary gas passage; 811. Connecting hole; 812. Annular passage; 82. Secondary gas passage; 83. Sealing ring; 84. Central through hole; 9. Secondary accumulator; 10. Second connecting pipe. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] In this embodiment, an active intervention measure is added to the GM pulse tube refrigerator, namely, a gas splitting structure 8 is set at the cold end of the pulse tube refrigerator. By replacing different splitting structures 8, i.e. splitting structures 8 with different effective area ratios, the gas volume is reasonably allocated to achieve the expected primary and secondary refrigeration performance, so as to ensure that the ideal flow rate is obtained at deep cryogenic temperatures.

[0032] It should be noted that the active intervention measures here refer to actively intervening by changing the flow distribution structure 8 with different effective area ratios according to different target needs, so as to adjust the airflow distribution and achieve the expected primary and secondary cooling performance.

[0033] Compared to existing pulse tube refrigerators that adjust the phase relationship between pressure waves and mass flow through gas distribution valves at the hot end, which limits the cylinder allocation at the cold end and cannot achieve a quantitative effect, this type of pulse tube refrigerator has its cooling performance limited during manufacturing.

[0034] Meanwhile, compared to the pulse tube refrigerators with U-shaped tubes in the prior art, the diversion structure 8 in this embodiment is detachable. Adjustment can be achieved simply by replacing the diversion structure 8, without the need to manufacture a complete pulse tube refrigerator as a whole, which greatly reduces costs.

[0035] See Figure 1 , Figure 2A GM pulse tube refrigerator includes a helium compressor 5, a primary accumulator 7, a secondary accumulator 9, a secondary pulse tube 3, a primary pulse tube 2, and a flow divider 8. The helium compressor 5 is connected to the primary accumulator 7. The connection between the primary accumulator 7 and the secondary accumulator 9 is provided with the flow divider 8. The flow divider 8 is provided with a primary gas channel 81 and a secondary gas channel 82. The primary accumulator 7 is connected to the primary pulse tube 2 through the primary gas channel 81. The primary accumulator 7 is connected to the secondary accumulator 9 through the secondary gas channel 82. The secondary accumulator 9 is connected to the secondary pulse tube 3. The effective area ratio of the primary gas channel 81 to the secondary gas channel 82 is 8:2, 7:3, 6:4, or 5:5, so that the helium content entering the secondary accumulator 9 is about 20% to 50%, and 20% to 50% is the optimal value for the gas volume ratio of the secondary accumulator 9.

[0036] See Figure 6 In this embodiment, Sage is used for simulation. The pulse tube refrigerator adopts a gas-coupled pulse tube refrigerator cylinder. The gas distribution ratio of the first and second stages will affect the cooling capacity generated by the first and second stages of the refrigerator. The simulation is set to keep the compressor gas delivery mass flow rate constant at 6g / s and change the gas distribution ratio of the first and second stages.

[0037] like Figure 6 As shown, as the proportion of secondary gas flow gradually increases, the primary cooling capacity gradually increases. However, the secondary cooling capacity shows a relatively small impact when the proportion of secondary gas flow is less than 60%, but a rapid decrease in secondary cooling capacity when it exceeds 60%. The reason for this phenomenon may be that the mass flow requirement of the secondary system of the chiller is relatively low. A proportion of 20% to 50% can generate about 1.7W of cooling capacity, while a proportion of more than 50% increases the secondary heat recovery loss and deteriorates the performance. At the same time, as the primary mass flow gradually decreases, the primary heat recovery loss decreases, leading to a gradual increase in primary cooling capacity.

[0038] Boundary conditions for simulation and experiment, such as Figure 8 As shown, the cold storage materials include stainless steel wire mesh, copper wire mesh, lead balls, hot copper, GOS (low-temperature material), etc.

[0039] The mass flow rate requirement of the secondary system of the chiller is relatively low. Simulation shows that a 20% to 50% proportion can generate about 1.7W of cooling capacity. However, if it exceeds 50%, the secondary heat recovery loss increases and the performance deteriorates. At the same time, as the primary mass flow rate gradually decreases, the primary heat recovery loss decreases, resulting in a gradual increase in the primary cooling capacity.

[0040] Experimental data on the cooling capacity of the primary and secondary refrigeration mechanisms achieved by adjusting the pore size are as follows: Figure 7 As shown.

[0041] See Figure 6 , Figure 7 The experimental data is generally lower than the simulation data because the simulation data ignores some heat loss during actual operation, etc., while the simulation data is under ideal conditions.

[0042] 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.

[0043] Based on both simulation and experimental data, a secondary gas volume ratio of 20% to 50% represents the most reasonable design range.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] See Figure 1 The 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Diversion method for pulse tube refrigerators:

[0059] 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.

[0060] 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.

[0061] Example 2

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 vascular 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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