JP2003004350A - Method for injecting liquid helium into low temperature holder wherein superconducting coil is incorporated and held and cooling system of superconducting generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injecting liquid helium into a low temperature holder wherein a superconducting coil is incorporated and held and a cooling system of a superconducting generator wherein a helium gas produced in a process of transfer is subjected to gas-liquid separation and only the liquid helium wherefrom the helium gas having no utility value is removed is injected into the low temperature holder, on the occasion when the liquid helium is transferred for injection from a liquid helium storage tank to the low temperature holder through a transfer tube. SOLUTION: The cooling system of the superconducting generator is constituted of a helium refrigerator 24, a device 25 for gas-liquid separation and injection, and the superconducting generator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting liquid helium into a cryostat which maintains and incorporates a superconducting coil and a cooling system for a superconducting generator.

[0002]

2. Description of the Related Art A cryostat, which is a cryostat, contains a superconducting wire wheel and liquid helium, etc., and is capable of maintaining the superconducting wire wheel in a superconducting state of 4K level. Among convection, conduction, and radiation, first, convection is solved by placing a superconducting wire wheel in a liquid helium container or a vacuum container, and radiation is obtained by vapor-depositing aluminum on a polyester film forming a multilayer heat insulating material. The multilayered stack of shields reduces the heat transfer due to radiation, and the support of the liquid helium container and the superconducting wire wheel is designed to block the inflow of heat due to conduction by using FPR or the like. In addition, between room temperature and 4K level, a thermal shield is installed at 80K or 20K level,
It is cooled by the evaporative gas of liquid nitrogen or liquid helium.

Regarding cooling of the superconducting wire wheel, several cooling methods are used. One of them is an immersion cooling method in which the superconducting wire wheel is immersed in liquid helium, and the superconducting wire wheel is placed in a vacuum. There is an indirect cooling method that cools by heat conduction with a placed liquid helium container or piping, the former is the most common and is used from large superconducting wire wheels to magnetic levitation wire wheels, medium and small ones such as MRI, and the latter. Is used for relatively small and medium sized products.

A cryostat which is built in together with the superconducting wire and liquid helium in order to keep the superconducting wire in a superconducting state at a cryogenic temperature of 4K level.
For example, in the case of a superconducting generator, as shown in FIG.
It is composed of a rotor 50 forming a vacuum double-tube heat insulating container and a stator 61 having a magnetic shield provided outside thereof. The rotor 50 has a hollow cylindrical torque tube 52 to which a superconducting field coil 51 is attached as an inner tube, a damper 54 forming an outer tube on the outer side thereof, and a double tube having the torque tube as an inner tube. A vacuum heat insulating layer is formed between the outer tube and the outer tube with a superconducting field coil 51 provided outside the torque tube forming the inner tube forming the structure, and an inner wall of the outer tube and the superconducting field magnet. A radiation shield 53 is interposed between the wire ring and the wire. The damper 54 having the torque tube 52 as an inner tube and forming an outer tube forms a container-shaped hollow cylindrical rotary shaft having a closed structure at one end and an open end at the other end. And
A helium supply / discharge device 11a made of a double pipe structure is provided at the other open end of the damper 54 having one closed end, the tip of the inner pipe forms a liquid helium inlet, and the outer pipe forms a helium gas outlet. To form. Liquid helium injected from the helium refrigeration system 57 via the helium supply / discharge system 11a and the inner tube of the double-tube structure forming the system is damped by the centrifugal force of the rotating rotor 50. 54 is unevenly distributed in the inner wall area of the torque tube 52 forming the inner tube of 54,
The helium gas evaporated by the invasion of external heat is separated into the shaft core of the damper 54. The separated helium gas is discharged to the outside after cooling the current lead 56 at the outer pipe part of the helium supply / discharge device 11a of the double pipe structure, and is recovered to the helium refrigerating device 57, and the helium circulation system is supplied. Form. The damper 54 forming the hollow cylindrical rotary shaft
The liquid helium introduced into the inside indirectly cools the superconducting field coil 51 in the vacuum heat insulating layer through the vacuum outer wall of the torque tube 52 forming the inner tube to cool it to a cryogenic temperature of about 4.2K. Built in to maintain superconductivity. The outer circumference of the damper 54 of the rotor 50 is kept at room temperature, and the inside of the torque tube 52 corresponding to the inner tube is kept at an extremely low temperature of about 4 degrees.
It is held at K level.

With the above structure, when cooling the superconducting field coil, liquid helium is supplied to the rotor 50 from the liquid helium storage tank (not shown) of the helium refrigerating device 57 via the helium supply / discharge device 11a at the shaft end. To be done. And
The helium gas evaporated by the external heat infiltration cools the torque tube 52, passes through the helium supply / discharge device 11a, and returns to the liquefied compression unit (not shown) of the helium refrigeration device 57 to be recompressed. Although the exciting current to the superconducting field coil is connected to the superconducting field coil 51 from the external DC power source through the collector ring 58 and the current lead 56, the current lead 56 is cooled. The helium gas used for is also discharged to the outside through the discharge port of the helium supply / discharge device 11a and then collected.

A magnetic shield 5 is provided on the outer periphery of the rotor 50.
A stator 61 having a void armature winding 60 having 9 is provided.

As described above, the helium refrigerating device is used for cooling the superconducting wire wheel, and the refrigerating device is composed of the following elements. a, a compressor arranged in a room temperature room temperature part for compressing a refrigerant (usually helium) to a high pressure, b, an expander installed in a low temperature part for expanding a refrigerant from a high pressure to a low pressure to generate cold, c, A Claude cycle is used in a large helium refrigerator, which comprises a heat exchanger installed between the compressor and an expander that thermally separates room temperature and cryogenic temperature.

The flow of liquefied helium production by the helium refrigeration system 57 formed by the above-mentioned Claude cycle is as follows.
As shown in FIG. 3, a circulation purification process in a helium gas tank 71 that stores a purified gas obtained by removing impurities such as air, moisture, and hydrocarbons from a reflux gas, a compression process by a liquefied compressor unit 72, and a high temperature cold The helium gas supplied from the helium gas tank 71 consists of a pre-cooling process by the box 73, a cooling process of isenthalpic expansion by the low temperature cold box 74, and a liquefaction process by Joule-Thomson expansion. The high-pressure high-temperature gas compressed to 0.5 MPa and 300 K is pre-cooled by liquid nitrogen in the high-temperature cold box 73 to lower the temperature to about 80 K, and further heat-exchanged by two expansion turbines in the low-temperature cold box 74 to about 1.5 MPa 10 K. To the final cold helium gas After passing through the heat exchanger, it is liquefied by the Joule-Thomson valve 78 and stored in a liquefied helium dewar 75, which is a liquid helium storage tank, in a state of approximately atmospheric pressure.

The liquid helium stored in the liquid helium storage tank (Dewar) 75 forms a cryogenic liquid, passes through the valve box 76, and in some cases, contains a gas component, and is transferred to the vacuum heat transfer structure transfer tube 77. Cryostat with built-in superconducting wire 1
1, and the transfer and filling is performed via the liquid helium inlet provided in the helium supply / discharge device 11a. Liquid helium, which is the filled cryogenic liquid, keeps the built-in superconducting wire ring in the superconducting state by the required immersion / indirect cooling in the cryostat, which is the cryostat, and in the process, it is evaporated by the heat intrusion from the outside. The helium gas is returned to the suction line of the liquefied compressor unit 72 via the outlet of the helium supply / discharge device 11a, reaches the room temperature, and is recompressed through the reflux passage 79. On the other hand, the low temperature helium gas that does not liquefy in the liquid helium dewar 75 is the low temperature cold box 7.
4, the temperature is increased while exchanging heat with the gas on the high pressure side in the heat exchanger, the temperature becomes normal at the outlet of the high temperature cold box 73, and it is returned to the compressor suction line and recompressed. As described above, the helium circulation system is formed to form the cooling system for the superconducting wire wheel.

[0010]

By the way, in the cooling system for the superconducting wire wheel described above, the liquid helium storage tank 7 is used.
When 5 cannot be installed close to the cryostat 11 which is a cryostat having a superconducting wire wheel as a load target, the helium storage tank 75 is connected to the helium supply / discharge device 11a.
The heat load (about 1 W / m) in the transfer pipe of the transfer tube 77 having the vacuum heat insulation structure up to the above becomes a non-negligible value. Therefore, part of the liquid helium being transferred is evaporated by the heat load, which not only causes an increase in pressure loss of the transfer tube which is the transfer pipe, but also has a utility value in cooling the superconducting wire wheel on the load side. There is a problem of increasing the loss in the superconducting wire wheel due to no helium gas.

The present invention has been made in view of the above problems, and liquid helium is transferred from a liquid helium storage tank through a transfer tube and injected into a low temperature holder that contains a superconducting wire and maintains a superconducting state. At that time, gas-liquid separation of helium gas generated during transfer was performed, and only liquid helium excluding helium gas that had no utility value was injected into the cryostat to improve transfer efficiency in the transfer tube and The purpose of the present invention is to provide a method for injecting liquid helium into a cryogenic retainer that maintains and incorporates a superconducting wheel and a cooling system for a superconducting generator that enables the superconducting wheel to be maintained in a superconducting state without causing heat loss. It is a thing.

[0012]

Therefore, a method of injecting liquid helium into a cryostat having a built-in superconducting wire ring according to the present invention is disclosed in a liquid helium storage tank for storing liquid helium at about atmospheric pressure. In a pouring method of transferring and injecting through a transfer tube into a cryostat equipped with a helium supply / discharge device for maintaining the superconducting state, vapor-liquid separation of vaporized gas evaporated during transfer at the transfer tube end point Then, only the separated liquid helium is introduced into the cryostat through the inlet of the supply / discharge device.

The invention according to claim 1 is the first aspect of the present invention.
The invention describes a method for injecting liquid helium into a cryostat that maintains a superconducting state by incorporating a superconducting coil, wherein the superconducting coil is maintained in a superconducting state from the liquid helium storage tank that stores the liquid helium. At the end of the transfer, the helium gas generated during the transfer is separated at the end of the transfer, and only liquid helium is injected into the injection port of the low-temperature holder to mix the helium gas of low utility value. There is no such thing.

Further, in the gas-liquid separation according to the first aspect, preferably, the vaporized gas generated during the transfer is separated through a vacuum heat insulation container provided at the transfer end of the transfer tube, and the separated liquid helium is separated. It is preferable to inject into the cryostat through the inlet.

To completely remove the helium gas generated during the transfer, the transfer tube is moved out in the vacuum space of the vacuum heat insulating container, and the liquid helium stored in the container is transferred to the inlet of the cryostat by the siphon effect. The cryostat is filled via the above.

Further, the evaporative gas separated by the gas-liquid separation according to the first aspect is provided with a JT effect provided above the liquid helium storage tank through the outer tube of the transfer tube having a vacuum heat insulation double tube structure. Therefore, it is preferable to suck the low-temperature helium gas through an ejector that liquefies the low-temperature helium gas and to return it to the liquid helium storage tank.

The liquid helium storage tank is provided with an ejector having a JT throttling function for liquefaction, and the helium gas which is the evaporative gas separated by the vacuum heat insulation container for gas-liquid separation is a vacuum heat insulation double pipe of a transfer tube. The ejector is made to suck and flow back through the outer tube of the structure.
By sucking and refluxing through this outer tube, the heat shield effect to the liquid helium being transferred is increased, and the amount of heat penetration is reduced.

A preferred cooling system for a superconducting generator using the liquid helium injection method according to any one of claims 1 to 3 is a refining compression unit for a recovered gas from a cryostat and a compression unit for a purified helium gas. And a low temperature helium gas generator comprising a high temperature cold box precooled with liquid nitrogen and a low temperature cold box with an expansion turbine, and liquid helium liquefied by liquefying the low temperature helium gas under substantially atmospheric pressure by the JT effect. A liquid helium storage tank for storage, a transfer tube for transferring and injecting the stored liquid helium into a superconducting generator equipped with a helium supply / discharge device, the superconducting generator, and a cooling system that forms a helium circulation system. Therefore, a double tube structure with a vacuum insulation structure is used for the transfer tube. A vacuum insulation container for gas-liquid separation is provided between the transfer end of the fur tube and the inlet of the helium supply / discharge device of the superconducting generator, and an ejector having the JT effect is provided in the liquid helium storage tank to separate the separated liquid. Helium is supplied to the inlet by the siphon effect, while evaporative gas is sucked by the ejector via the outer tube of the transfer tube and is returned to the liquid helium storage tank.

The invention according to claim 4 describes a cooling system for a superconducting generator, which is the second invention of the present invention. The system is the liquid helium cryostat according to the first invention of the present invention. Is preferably used.
In other words, after recovering helium gas to remove impure gases such as air, water, and hydrocarbons, a high-pressure low-temperature gas generator that compresses and reuses it and liquefied helium that is a cryogenic liquid that liquefies the high-pressure low-temperature gas from the device And a transfer tube for transferring the liquid helium stored in the storage tank, and a superconducting generator for placing the superconducting field coil in a superconducting state by the injected liquid helium. The transfer tube has a vacuum double tube structure, and a vacuum heat insulation container for gas-liquid separation is provided in the vicinity of the helium inlet of the helium supply / discharge device of the superconducting generator including the outlet of the tube, and the inside of the container The transfer liquid from the liquid helium storage tank is injected from the inner tube of the transfer tube, and the vaporized gas of helium generated during transfer is separated into gas and liquid. It is liquid helium only removing the free helium gas utility value that so as to inject the siphon effect to the inlet of the helium supply and discharge apparatus of the superconducting generator. On the other hand, an ejector is used for the liquefaction J-T throttle valve in the upper part of the liquid helium storage tank downstream of the high-pressure low-temperature gas generator, and the helium gas is separated by the ejector through the outer tube of the transfer tube. Is sucked and is refluxed and recovered in the liquid helium storage tank.

Liquid helium to be injected into the superconducting power generator is desirably supplied at a pressure of 0.1 to 0.13 MPa and 4.2 K or so.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
This will be described together with the illustrated example. However, unless otherwise specified, the dimensions, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Absent. The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a cooling system for a superconducting generator of the present invention.

As shown in FIG. 1, the cooling system for a superconducting generator of the present invention comprises a helium refrigerating device 24, a gas-liquid separating / injecting device 25, and a superconducting generator 10, and is produced by the helium refrigerating device 24. The liquid helium stored in the tank is separated by the gas-liquid separation injection device 25 to separate the helium gas generated during the transfer, and only the remaining liquid helium is injected from the injection port of the helium supply / discharge device 11a of the superconducting power generator 10, and The loss is minimized.

The helium refrigerating apparatus 24 is composed of a collecting and refining machine 16 and a freeze liquefying machine 17. The recovery and refiner 16 recovers a part of the reflux helium gas E vaporized by the heat invasion from the outside in the superconducting power generator 10 and the liquefied helium gas in the liquid helium storage tank 14, and collects air, water and hydrocarbons from the recovered gas. Impurity gas such as the above is removed and purified by the recovery and refiner 16 including the impure gas tank 16c, the recovery and refinement compressor 16a, and the refiner 16b, and the refined refined gas is stored in the refined gas tank 21.

The freezing liquefier 17 comprises a liquefaction compression unit 18, a high temperature cold box 19, a low temperature cold box 20, a liquid helium storage tank 14, and a valve box (not shown). In the liquefaction compression unit 18, the main compressor 18 that compresses most of the reflux helium gas E discharged from the superconducting power generator 10.
It is compressed by a to obtain high-pressure helium gas of about 300K.
Then, in the high temperature cold box 19, it is cooled by liquid nitrogen through the AC heat exchanger 19a and refined through the adsorber 19b to obtain a low temperature gas of about 80K. Then, in the low temperature cold box 20, the low temperature gas B of about 10 K or less is obtained by isenthalpic expansion by the AC heat exchanger and the expansion turbines 20a and 20b.

Next, in the liquid helium storage tank 14 composed of a vacuum heat insulation container, the J-T provided at the upper part
By providing an ejector 15 having an effect, the low-temperature gas whose temperature has been lowered to 10 K or less by isenthalpic expansion is expanded to about atmospheric pressure, and a part thereof is liquefied and stored as liquid helium in the liquid helium storage tank 14 and not liquefied. The low temperature helium gas C is returned to the low temperature cold box 20,
The temperature is increased while exchanging heat with the gas on the high pressure side in the heat exchanger, the temperature becomes normal at the outlet of the high temperature cold box 19, and the temperature is returned to the liquefaction compression unit 18 and recompressed. Liquid helium D
Is supplied to the superconducting generator 10 via the gas-liquid separation injection device 25 on the downstream side.

The gas-liquid separation / injection device 25 comprises a transfer tube 13 having a vacuum heat insulation double tube structure and a gas-liquid separation vacuum heat insulation container 12. The gas-liquid separation vacuum insulation container 1
2 is provided between the outlet of the transfer tube 13 and the helium supply / discharge device 11a of the superconducting generator 10, and discharges the liquid helium D transferred from the liquid helium storage tank 14 through the inner tube 13a of the transfer tube 13, Helium gas evaporated by the invasion of external heat in the transfer process is separated, and the separated liquid helium is stored at the bottom of the container. The separated and stored liquid helium is sucked by the siphon effect by the suction pipe 11b hanging from the liquid helium inlet of the adjacent helium supply / discharge device 11a into the stored liquid and introduced into the superconducting power generator 10. Thus, the helium gas, which has no utility value for cooling the superconducting generator and causes the reduction in cooling efficiency, is removed. The sucked liquid helium keeps the superconducting field coil of the rotor cooled in a superconducting state, evaporates due to heat invasion from the outside, and is discharged as reflux helium gas E, and is recovered by the liquefying compression unit 18 and recompressed. Is
Form a circulatory system.

The helium gas which has been gas-liquid separated in the gas-liquid separation vacuum insulation container 12 and which is generated during the transfer is transferred through the outer tube 13b of the transfer tube 13 to
Ejector 1 provided above the liquid helium storage tank 14.
It is made to suck and recirculate | reflux by 5. By the reflux, it can be used as a heat shield for the transfer tube 13 to reduce the amount of heat entering the tube. At the same time, it has an effect of lowering the pressure in the gas-liquid separation vacuum heat insulating container 12, which makes it possible to reduce the supply pressure to the rotor of the superconducting generator 10, and the sucked helium gas is reliquefied by the ejector. The liquefaction efficiency can be improved.

The superconducting generator 10 has the generally used structure shown in FIG. 2, and the rotor is constituted by a double-tube low-temperature holder having a vacuum heat insulating structure, and the inside of the vacuum outer tube is provided. A superconducting field coil is built in, and liquid helium is introduced into the inner tube for indirect cooling.

[0029]

With the above structure, it is possible to reduce the heat loss and to efficiently cool the superconducting generator into which liquid helium is injected.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a cooling system for a superconducting generator of the present invention.

FIG. 2 is a sectional view showing a vacuum heat insulating structure of a general superconducting generator.

FIG. 3 is a diagram showing a schematic configuration of a cooling system for a conventional superconducting generator.

[Explanation of symbols]

10 Superconducting generator 11 Cryostat (cryostat) 11a Helium supply and discharge device 11b Inhalation tube 12 Gas-liquid separation vacuum insulation container 13 Transfer tube 13a inner tube 13b outer tube 14 Liquid helium storage tank 15 ejectors 16 Recovery and refiner 17 Frozen liquefaction machine 18 Liquefaction compression unit 19 high temperature cold box 20 low temperature cold box

Claims (4)

[Claims] 1. A liquid helium storage tank that stores liquid helium at approximately atmospheric pressure, and transfers and injects it through a transfer tube into a cryostat having a helium supply / discharge device that maintains and stores a superconducting coil in a superconducting state. In the injection method, at the end of transfer of the transfer tube, the vaporized gas evaporated during the transfer is separated into gas and liquid, and only the separated liquid helium is introduced into the cryostat through the injection port of the supply / discharge device. A method for injecting liquid helium into a cryostat which maintains and incorporates a superconducting wire wheel, which is characterized in that. 2. In the gas-liquid separation, the vaporized gas generated during the transfer is separated through a vacuum heat insulation container provided at the transfer end of the transfer tube, and the separated liquid helium is kept at a low temperature through the injection port. The method for injecting liquid helium into a cryostat, which maintains and incorporates a superconducting coil according to claim 1, characterized in that the liquid helium is injected into the cryostat. 3. The evaporative gas separated by the gas-liquid separation passes through an outer tube of the transfer tube having a vacuum adiabatic double tube structure, and is installed on the liquid helium storage tank in the JT.
2. A cryogenic retainer having a superconducting wire wheel according to claim 1, which is sucked through an ejector for liquefying low temperature helium gas by the (Jule Thomson) effect and is returned to a liquid helium storage tank. Liquid helium injection method. 4. A low-temperature helium gas generator comprising a refining / compressing unit for recovered gas from a cryostat, a compressor unit for refining helium gas, a high-temperature cold box precooled by liquid nitrogen, and a low-temperature co-box by an expansion turbine. The low-temperature helium gas is liquefied under the substantially atmospheric pressure by the JT effect, and the liquid helium storage tank for storing the liquefied liquid helium and the stored liquid helium are transferred to a superconducting generator equipped with a helium supply / discharge device. A transfer tube for injection, a superconducting power generator, and a helium circulation system cooling system composed of a double tube structure having a vacuum insulation structure for the transfer tube, and a transfer end of the transfer tube. A vacuum insulation container for gas-liquid separation between the inlet of the helium supply and discharge device of the superconducting generator The liquid helium tank is provided with an ejector having a JT effect, and the separated liquid helium is supplied to the inlet by the siphon effect, while the evaporative gas is supplied by the ejector through the outer tube of the transfer tube. A cooling system for a superconducting generator, which is configured to be sucked and returned to a liquid helium storage tank.