A connecting pipe and a cryogenic refrigerator having the connecting pipe

Abstract

This utility model provides a connecting pipe and a cryogenic refrigerator having the connecting pipe. The connecting pipe includes a double-layer structure consisting of an inner liner and an outer casing. The inner liner has a continuous and tightly arranged rectangular parallel corrugated section in the middle, and smooth sections at both ends. The smooth sections are covered with stepped end sleeves, which include a first section covering the smooth sections at both ends of the inner liner, a second section covering the two ends of the outer casing, and a transitional third section. The end sleeves are welded to an adapter, and the adapter is threadedly connected to a self-sealing joint. This connecting pipe, by improving the corrugated pipe structure and size as well as the connection structure, effectively reduces turbulence and vortices inside the pipe, reduces vibration and noise, and makes the pipe more flexible and easier to connect and arrange. It can significantly improve measurement accuracy and improve the noise environment at the site.

Description

Technical Field

[0001] This utility model relates to the field of refrigeration, further to the field of cryogenic refrigeration machines, and more specifically to a connecting pipe and a cryogenic refrigeration machine having the connecting pipe. Background Technology

[0002] Cryogenic refrigerators are closed-loop refrigerators that can provide cooling at extremely low temperatures. They have only been developed in recent decades, and with the advancements in cryogenic physics, electronics, and aerospace technology, cryogenic refrigerators have gained a crucial position in medium-sized, small-scale, and especially micro-scale cryogenic refrigeration technologies. Among the most important are pulse tube refrigerators and GM refrigerators, both typical refrigerators operating in the liquid helium temperature range. They have wide applications in condensed matter physics, quantum computing, communications, medicine, power, energy, scientific instruments, aerospace, and military fields, such as in magnetic resonance imaging (MRI), dilution refrigerators, particle accelerators, and astronomical telescopes, among other medical and scientific research equipment.

[0003] The GM (Gifford-McMahon) refrigerator is based on the GM cycle principle and mainly consists of a motor, cylinder, piston, regenerator, and cold-end heat exchanger. It achieves refrigeration by utilizing the charging and discharging process of high and low-pressure helium gas within a closed pulse tube. During operation, in the intake phase, high-pressure gas enters the expansion chamber after heat exchange with the regenerator. The piston then moves upward to a designated position. Once the expansion chamber is filled with high-pressure gas, the intake ends, and the rotary valve switches the gas passage to the low-pressure circuit. The high-pressure gas in the expansion chamber then expands into the low-pressure circuit, exchanges heat with the regenerator again, and flows out of the refrigerator. Simultaneously, the cooling energy is transferred to the object being cooled through the cold-end heat exchanger. Subsequently, the piston moves towards the bottom of the cylinder to expel the remaining helium gas in the expansion chamber, completing one refrigeration cycle. This continuous switching between high and low pressure for continuous Simon expansion, with the regenerator constantly accumulating cooling energy, results in a sustained cooling effect for the GM refrigerator. Compared to GM refrigerators, pulse tube refrigerators have fewer vibrations and lower reliability because they do not have reciprocating pistons. Instead, they rely on a "gas-like piston" formed by helium gas within the pulse tube to compress the helium. This reduces wear and tear and potential malfunctions caused by moving parts. Since their regenerators do not require reciprocating motion, resulting in low vibration and high reliability, they are widely used in fields such as low-temperature superconductivity and quantum computing.

[0004] For cryogenic refrigerators such as GM refrigerators and pulse tube refrigerators, there are connecting pipes between the refrigerator body and the compressor, especially between the compressor and the rotary valve, typically including inlet and return connecting pipes. In existing technology, the inner lining of the inlet and return connecting pipes is a metal spiral corrugated pipe. When high-pressure helium gas flows rapidly through the connecting pipe, the collision between the helium gas and obstacles such as the corrugated grooves on the pipe wall easily creates turbulence and vortices. Furthermore, excessively wide wave pitch can cause abrupt changes in the pipe diameter, triggering pressure wave reflection. The superposition of incident and reflected waves can form standing waves, leading to local pressure fluctuations and generating noise and vibration. Under certain conditions, it may even excite the natural frequency of the pipe, causing resonance and amplifying noise, typically such as whistling or booming sounds. Such noise has a significant impact on high-precision refrigeration systems, such as dilution refrigeration systems using GM and pulse tube refrigerators. Therefore, it is necessary to improve the design of the connecting pipes to reduce the noise of the refrigerator during operation. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems mentioned in the background section, thereby providing a connecting pipe and a cryogenic refrigerator having the connecting pipe. The connecting pipe can be used as the inlet and outlet pipe of the cryogenic refrigerator, and can significantly reduce the vibration and noise generated during the operation of the cryogenic refrigerator. The specific invention details are as follows:

[0006] A connecting pipe includes a double-layer structure consisting of an inner liner and an outer sheath. The inner liner includes a corrugated section in the middle and smooth sections at both ends. The corrugated section in the middle of the inner liner is covered and in close contact with the outer sheath. The smooth sections at both ends of the inner liner are covered with end sleeves. The end sleeves include three sections: a first section covering the outer periphery of the smooth sections, a second section covering the outer periphery of both ends of the outer sheath, and the second section extending inward to a suitable length. A third section is provided between the first and second sections, thus forming a stepped structure. The end sleeves are welded to an adapter, and the adapter is threaded to a self-sealing connector. The corrugated section in the middle of the inner liner has a continuous and closely arranged rectangular parallel corrugated structure.

[0007] Furthermore, the outer casing is made of stainless steel dense woven mesh, preferably 316 stainless steel dense woven mesh.

[0008] Furthermore, the wave spacing between two adjacent crests or two troughs in the corrugated pipe section in the middle of the liner is 1.5-2mm, and the distance between the crest and trough in the height direction is half the outer diameter of the corrugated pipe minus the inner diameter.

[0009] Furthermore, the distance between the crests and troughs of the corrugated pipe section in the middle of the inner liner pipe in the height direction is 2-4 mm.

[0010] Furthermore, the single-wave width of the corrugated section in the middle of the inner liner is 1-1.5mm.

[0011] Furthermore, the nominal diameter of the corrugated pipe section in the middle of the inner liner is DN25, the inner diameter is 25.0mm, the outer diameter is 32.0mm, and the distance between the crest and trough in the height direction is 3.5mm.

[0012] Furthermore, both the inner liner and the outer sheath are made of stainless steel.

[0013] This utility model also provides a cryogenic refrigerator with the aforementioned connecting pipe, including a helium compressor, a rotary valve and a refrigerator body, with an inlet pipe and a return pipe provided between the helium compressor and the rotary valve, and the inlet pipe and the return pipe respectively using the aforementioned connecting pipe provided by this utility model.

[0014] Furthermore, the cryogenic refrigerator with the aforementioned connecting pipe is a GM refrigerator or a pulse tube refrigerator.

[0015] Based on the above-described invention, this utility model innovatively discovers, compared to existing technologies, that improving the corrugated structure of the corrugated pipe section can reduce vibration and noise. Furthermore, it makes significant and groundbreaking improvements to the overall structure, addressing the shape, size, and arrangement of the corrugated structure. The connections between the end sleeves, the corrugated pipe, and the adapters are also improved to enhance strength, sealing, and stability. This utility model overcomes conventional understandings of corrugated pipe structure, processing technology, and performance parameters in existing technologies, resulting in the following beneficial technical effects: effectively reducing turbulence and / or vortices within the pipe, thereby reducing vibration and noise (measured noise reduction of up to 10 dB); significantly improving the measurement accuracy of upper-level systems such as dilution refrigeration systems; greatly improving the on-site noise environment; reducing adverse effects on worker health; and making the connecting pipes for cryogenic refrigeration units more flexible and easier to connect and arrange. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 : A schematic diagram of the connecting pipe of this utility model;

[0018] Figure 2 : A partially enlarged schematic diagram of the connecting tube of this utility model;

[0019] Figure 3: A schematic diagram of the overall structure of a cryogenic refrigeration machine with the connecting pipe of this utility model.

[0020] Figure label:

[0021] 1-Connecting pipe; 2-Inner liner pipe; 2A-Corrugated pipe section; 2B-Smooth pipe section; 3-Outer casing pipe; 4-End sleeve; 4A-First section; 4B-Second section; 4C-Third section; 5-Adapter; 6-Self-sealing connector; 11-Helium compressor; 12-Rotary valve; 13-Inlet pipe; 14-Return pipe; 15-Refrigeration unit body. Detailed Implementation

[0022] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. It is obvious that the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0023] like Figure 1 As shown, the connecting pipe 1 of this application includes a double-layer structure consisting of an inner liner pipe 2 and an outer casing pipe 3. The outer casing pipe 3 is made of stainless steel dense braided mesh, and more specifically, 316 stainless steel braided mesh can be used. The inner liner pipe 2 includes a corrugated pipe section 2A located in the middle and smooth pipe sections 2B located at both ends, thereby forming a corrugated pipe as a whole, and can be made of 316 stainless steel. The outer casing pipe 3 covers the outer periphery of the corrugated pipe section 2A of the inner liner pipe 2 and is in close contact with it. The outer periphery of the smooth pipe sections 2B located at both ends of the inner liner pipe 2 is covered with end sleeves 4. Specifically, the end sleeves 4 actually include three sections, wherein the first section 4A is covered on the outer periphery of the smooth pipe section 2B, the second section 4B is covered on the outer periphery of both ends of the outer casing pipe 3, and the second section 4B extends inward by a suitable length; there is a transitional third section 4C between the first section 4A and the second section 4B. According to the above description, as Figure 1 As shown, the end sleeve 4 is actually stepped, thus fitting entirely onto the corrugated pipe section 2A and the smooth pipe section 2B of the inner liner pipe 2. Compared with the prior art, this utility model tightly fits the first section 4A of the end sleeve 4 with the smooth pipe section 2A of the inner liner pipe 2, thereby enhancing the strength of the connecting pipe 1 for the cryogenic refrigeration unit at both ends and improving sealing and stability, while reducing vibration and noise generated when high-pressure gas passes through. Furthermore, both ends of the end sleeve 4 are welded to the adapter 5, thereby fixing the adapter 5 to the end sleeve 4 at both ends. The adapter 5 at both ends is respectively threaded with a self-sealing connector 6, and an O-ring is used for sealing in the middle to connect to other components through the self-sealing connector 6.

[0024] As described in the background section, the connecting pipes used in cryogenic refrigerators generate noise during operation. This noise level is typically between 70-100 dB, which is not a significant concern for general applications. However, when cryogenic refrigerators such as GM refrigerators or pulse tube refrigerators are used in dilution refrigeration systems to provide an extremely low-temperature environment for quantum computers, noise becomes a major concern, directly impacting the accuracy of the quantum computers. Furthermore, the noise impact is substantial when multiple machines operate together, making it imperative to reduce the noise level during refrigerator operation. Through collaborative research with universities, research institutes, and enterprises, and combined with extensive experiments and tests, the inventors discovered that the corrugated structure of the corrugated pipe section 2A of the inner liner 2 has a significant impact on the noise level. Therefore, they innovatively found that vibration reduction and noise reduction can be achieved by improving the corrugated structure of the corrugated pipe section 2A of the inner liner 2.

[0025] Specifically, refer to Figure 2 The corrugated structure of the corrugated pipe section 2A of the inner liner pipe 2 in this invention is specifically rectangular parallel corrugations, which is significantly different from the traditional spiral corrugations. The crests and troughs of traditional spiral corrugations are arc-shaped or pointed, causing turbulence or vortices to form at the crests and / or troughs when high-pressure airflow passes through. Furthermore, the wide wave pitch of traditional spiral corrugations can lead to abrupt changes in pipe diameter, resulting in significant noise and vibration. In contrast, the corrugated structure of the corrugated pipe section 2A of the inner liner pipe 2 in this invention is a continuous and tightly arranged rectangular parallel corrugation. This means that the crests and troughs of the corrugated pipe section 2A of the inner liner pipe 2 are actually horizontal, allowing for close contact with the outer casing pipe 3 without gaps, thus preventing significant turbulence or vortices. Furthermore, the parallel corrugations are continuous and tightly arranged, with a wave pitch of only 1.5-2 mm between adjacent wave crests or troughs. The distance between the wave crests and troughs in the height direction is half the outer diameter minus the inner diameter of the corrugated pipe section 2A, specifically 2-4 mm, and the width of a single wave is 1-1.5 mm. By changing the distance between the wave crests and troughs in the height direction, the collision between high-pressure helium gas and the pipe wall can be effectively reduced, thus reducing turbulence and / or vortices. By reducing the wave pitch, i.e., densifying the corrugated structure, abrupt changes in the pipe diameter can be effectively reduced.

[0026] In one embodiment, the nominal diameter of the corrugated section 2A of the inner liner pipe 2 is DN25, i.e., the inner diameter is 25.0 mm and the outer diameter is 32.0 mm, thus the distance between the crest and trough in the height direction is 3.5 mm; the width of a single wave is 1-1.5 mm, and the wave pitch is 1.5-2 mm. The length of the connecting pipe 1 is 20 meters, and the end sleeves 4 at both ends are welded to the adapter 5. The adapter 5 is designed with threads for connecting a self-sealing connector 6. Before connection, 4 MPa of helium gas is injected for leak testing, and the leak rate is <1.0 × 10⁻⁶. -7 Pa∙m 3 / s. By modifying the corrugated structure parameters of corrugated pipe section 2A, the vibration of connecting pipe 1 is significantly reduced, and the noise is reduced by 10dB. At the same time, because the corrugated structure is denser, the pipeline of connecting pipe 1 is more flexible and easier to connect and arrange.

[0027] Compared to existing corrugated pipes, the corrugated pipe section 2A of this invention employs a denser corrugation process. The challenge lies in achieving a thinner wall thickness for section 2A while maintaining both strength and ductility to prevent breakage during continuous molding. The thinner the wall, the higher the requirements for the welding process. Welding must be done carefully to avoid burn-through, and the weld quality must be high to prevent leaks. This is particularly critical in the field of cryogenic refrigeration, where helium leakage rates are extremely stringent, typically <1.0 × 10⁻⁶. -7 Pa∙m 3 / s. Furthermore, a smaller corrugation pitch requires higher pressure stability during molding, necessitating improvements to the hydraulic press and control system. Simultaneously, a smaller corrugation pitch makes cleaning the inner wall folded surface of corrugated pipe section 2A more difficult, requiring mirror-finish molds and a dust-free workshop environment. These requirements for processing technology and production environment break through the conventional understanding of corrugated pipes held by those skilled in the art. This improvement is the result of the inventor's creative labor and continuous refinement, based on research and development and production practice.

[0028] Figure 3 The diagram shows the overall structure of the cryogenic refrigerator using the connecting pipe 1 of this invention. Two connecting pipes 1 are used in the cryogenic refrigerator, each 20 meters long. One serves as an inlet pipe 13, connecting the outlet of the helium compressor 11 to the inlet of the rotary valve 12; the other serves as a return pipe 14, connecting the outlet of the rotary valve 12 to the inlet of the helium compressor 11. High-pressure helium from the helium compressor 11 passes through the inlet pipe 13, then through the rotary valve 12, and enters the refrigerator body 15. After undergoing the refrigeration process, the helium is returned to the helium compressor 11 via the return pipe 14 by controlling the rotary valve 12, thus beginning a new cycle.

[0029] After applying the connecting pipe 1 of this utility model, the noise of the cryogenic refrigerator is significantly reduced. The specific test results are shown in Table 1.

[0030] Table 1: Comparison of Noise Test Results for Connecting Pipes Used in Low-Temperature Refrigeration Units

[0031] This utility model Rectangular parallel ripples 2-4mm 1.5-2mm 1-1.5mm 60dB Existing technology Spiral ripples 5mm or more 4mm and above 3mm and above 70dB

[0032] Tests show that using the connecting pipe 1 of this invention in the cryogenic refrigeration unit can effectively reduce turbulence and vortices, thereby reducing vibration. The measured noise level can be reduced by 10dB, which is very valuable for applications with stringent noise requirements: First, it significantly improves the measurement accuracy of upper-level systems such as dilution refrigeration units; second, it can greatly improve the noise environment on site and reduce the adverse effects on the health of workers; and third, the connecting pipe 1 for the refrigeration unit is more flexible and easier to connect and arrange.

[0033] It is obvious to those skilled in the art that the connecting pipe 1 can be used in cryogenic refrigerators such as GM refrigerators and pulse tube refrigerators. Of course, the connecting pipe 1 of this invention can also be used as a gas connecting pipe in other applications, and there are no technical obstacles to such conversion for those skilled in the art.

[0034] The connecting pipe 1 provided by this utility model has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. For those skilled in the art, the technical solution of this utility model is not limited to the solution defined in the specific implementation. Technical solutions formed by other modifications that can be obviously implemented based on ordinary technical knowledge in the art are all within the protection scope of this utility model.

Claims

1. A connecting pipe (1), comprising a double-layer structure consisting of an inner liner (2) and an outer casing (3), wherein the inner liner (2) comprises a corrugated pipe section (2A) located in the middle and smooth pipe sections (2B) located at both ends, the outer casing (3) is wrapped around the outer periphery of the corrugated pipe section (2A) in the middle of the inner liner (2) and is in close contact with it, and the outer periphery of the smooth pipe sections (2B) at both ends of the inner liner (2) is covered by end sleeves (4), characterized in that: The end sleeve (4) comprises three sections, of which the first section (4A) covers the outer periphery of the smooth tube section (2B), the second section (4B) covers the outer periphery of both ends of the outer tube (3), the second section (4B) extends inward to a suitable length, and there is a transitional third section (4C) between the first section (4A) and the second section (4B), thereby forming a stepped structure of the end sleeve (4); the end sleeve (4) is welded to the adapter (5), and the adapter (5) is threaded to the self-sealing connector (6); the corrugated tube section (2A) in the middle of the inner liner tube (2) has a continuous and closely arranged rectangular parallel corrugated structure.

2. A connecting pipe (1) as claimed in claim 1, characterized in that: The wave distance between two adjacent crests or two troughs in the corrugated pipe section (2A) in the middle of the inner liner pipe (2) is 1.5-2mm. The distance between the crests and troughs in the height direction is half the outer diameter of the corrugated pipe section (2A) minus the inner diameter.

3. The connecting pipe (1) according to claim 1 or 2, characterized in that: The single-wave width of the corrugated pipe section (2A) in the middle of the inner liner (2) is 1-1.5mm.

4. The connecting pipe (1) according to claim 3, characterized in that: The distance between the crest and trough of the corrugated pipe section (2A) in the middle of the inner liner (2) is 2-4 mm in the height direction.

5. The connecting pipe (1) according to claim 4, characterized in that: The nominal diameter of the corrugated pipe section (2A) in the middle of the inner liner pipe (2) is DN25, with an inner diameter of 25.0 mm, an outer diameter of 32.0 mm, and a distance of 3.5 mm between the crest and trough in the height direction.

6. A connecting pipe (1) according to claim 5, characterized in that: Both the inner liner (2) and the outer casing (3) are made of stainless steel.

7. A connecting pipe (1) according to claim 6, characterized in that: The outer tube (3) is made of 316 stainless steel dense woven mesh.

8. A cryogenic refrigerator having the connection pipe (1) according to any one of claims 1 to 7, comprising a helium compressor (11), a rotary valve (12) and a refrigerator main body (15), an intake pipe (13) and a return pipe (14) being provided between the helium compressor (11) and the rotary valve (12), characterized in that: The intake pipe (13) and the return pipe (14) respectively use the connecting pipe (1) as described in any one of claims 1-7.

9. A cryogenic refrigerator as claimed in claim 8, characterised in that: The cryogenic refrigeration unit is either a GM refrigeration unit or a pulse tube refrigeration unit.

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