WO2019146270A1

WO2019146270A1 - Superconductive cable system

Info

Publication number: WO2019146270A1
Application number: PCT/JP2018/045061
Authority: WO
Inventors: 茂樹礒嶋
Original assignee: 住友電気工業株式会社
Priority date: 2018-01-23
Filing date: 2018-12-07
Publication date: 2019-08-01

Abstract

A superconductive cable system according to one aspect of the present disclosure is for transmitting electric power among a plurality of electric power devices mounted on an aircraft. This superconductive cable system is provided with: a heat insulation pipe through which a liquid refrigerant is circulated; cores that each have a superconductive layer and that are housed in the heat insulation pipe; a tank that stores the liquid refrigerant; a pump that is provided to a liquid refrigerant circulation path including the tank and the heat insulation pipe and that circulates the liquid refrigerant; and a gas-liquid separator that is provided to the circulation path and that is for discharging a gas refrigerant generated by vaporization of the liquid refrigerant.

Description

Superconducting cable system

The present disclosure relates to a superconducting cable system. This application claims priority based on Japanese Patent Application No. 2018-008945 filed on Jan. 23, 2018. The entire contents of the description of the Japanese patent application are incorporated herein by reference.

As a technique for cooling a superconducting cable, a technique for performing circulating cooling using a subcooled refrigerant is known. In this method, the refrigerant is cooled to the subcooling state using a refrigerator, and the cooled refrigerant is sent to the superconducting cable using the pump, whereby the superconducting cable is cooled by the refrigerant cooled to the subcooling state by the refrigerator The refrigerant that has been used to cool the superconducting cable is returned to the refrigerator again.

As described above, for example, Patent Document 1 discloses a technique for circulating a refrigerant in the order of a refrigerator → a superconducting cable → a pump → a refrigerator, and cooling the superconducting cable in a path of a single stroke.

Unexamined-Japanese-Patent No. 2016-100221

A superconducting cable system according to an aspect of the present disclosure is a superconducting cable system that transports electric power between a plurality of power devices mounted on an aircraft, and is housed in a thermal insulation pipe for circulating a liquid refrigerant, and a thermal insulation pipe. A core having a superconducting layer, a tank for storing liquid refrigerant, a tank and a circulation channel of liquid refrigerant including a heat insulation pipe, a pump for circulating the liquid refrigerant, and a circulation channel, the liquid refrigerant being vaporized And a gas-liquid separator for discharging the gaseous refrigerant.

FIG. 1 is a schematic view showing an outline of an aircraft equipped with the superconducting cable system according to the present embodiment. FIG. 2 is a schematic view of a superconducting cable system disposed between two power devices mounted on the aircraft shown in FIG. FIG. 3 is a cross-sectional view taken along line III-III of FIG. FIG. 4 is a cross-sectional view showing the core shown in FIG. FIG. 5 is a cross-sectional view schematically showing a configuration example of the gas-liquid separator shown in FIG. FIG. 6 is a cross-sectional view schematically showing a configuration example of the gas-liquid separator shown in FIG. FIG. 7 is a cross-sectional view schematically showing a configuration example of the gas-liquid separator shown in FIG. FIG. 8 schematically shows temporal changes in the temperature and amount of liquid nitrogen present in the superconducting cable.

[Problems to be solved by the present disclosure]
An object of one aspect of the present disclosure is to provide a superconducting cable system that transports power between a plurality of power devices mounted on an aircraft, and which has a novel configuration suitable for weight reduction.
[Effect of the present disclosure]
According to the present disclosure, it is possible to provide a novel configuration that is suitable for weight reduction by using a superconducting cable that transports power between a plurality of power devices mounted on an aircraft.

[Description of the embodiment of the present disclosure]
First, embodiments of the present disclosure will be listed and described.

(1) The superconducting cable system 110 according to an aspect of the present disclosure transports power between a plurality of power devices mounted on the aircraft 1000 (see FIG. 1). The superconducting cable system 110 (see FIG. 2) includes the heat insulation pipe 30, the core 10, the tank 130, the pump 131, and the gas-liquid separator 132. The heat insulation pipe 30 distributes the liquid refrigerant. The core 10 is housed in the heat insulating tube 30 and has a superconducting layer. The tank 130 stores liquid refrigerant. The pump 131 is installed in a circulation channel of the liquid refrigerant including the tank 130 and the heat insulation pipe 30, and circulates the liquid refrigerant. The gas-liquid separator 132 is installed in the circulation flow path, and discharges the gas refrigerant in which the liquid refrigerant is vaporized.

According to the superconducting cable system 110 according to the above (1), the core 10 is cooled using the latent heat of vaporization of the liquid refrigerant flowing in the heat insulating pipe 30. Therefore, a refrigerator for cooling the liquid refrigerant to the supercooled state is not required as compared with the conventional cooling technique of the superconducting cable in which the core is cooled by circulation using the subcooled refrigerant. Therefore, when the superconducting cable system 110 is applied to a power cable for transporting electric power in an aircraft, it is not necessary to connect a refrigerator to the superconducting cable, so the weight of the power cable can be reduced.

Further, by providing the gas-liquid separator 132 in the circulation flow path of the liquid refrigerant, it is possible to suppress an increase in the refrigerant pressure in the heat insulation pipe 30 due to the gas refrigerant generated by the evaporative cooling of the core 10.

(2) In the superconducting cable system 110 according to the above (1), the tank 130 is filled with the liquid refrigerant cooled to the temperature of the boiling point.

According to this, the core 10 is cooled using the latent heat of evaporation of the liquid refrigerant supplied from the tank 130 into the heat insulation pipe 30 via the circulation flow path. During the operation of the aircraft 1000, the tank 130 is filled with the liquid refrigerant in an amount necessary to cool the core 10 based on the loss and the like generated during the operation of the aircraft 1000 before the takeoff of the aircraft 1000. The core 10 can always be maintained in the superconducting state.

(3) In the superconducting cable system 110 which concerns on said (1) or (2), the gas-liquid separator 132 (refer FIG. 2) has the pressure control valve 132A arrange | positioned at the exit of a gaseous refrigerant.

In this way, the pressure regulating valve 132A can maintain the differential pressure between the refrigerant pressure in the heat insulating pipe 30 and the external pressure. Therefore, even when the attitude of the airframe is inclined during operation of the aircraft and the refrigerant pressure rises, the gaseous refrigerant can be discharged without flowing out the liquid refrigerant from the inside of the heat insulation pipe 30.

(4) In the superconducting cable system 110 according to (1) to (3) above, the core 10 (see FIGS. 3 and 4) includes the former 12, the superconducting layer 13 disposed on the outer periphery of the former 12, and the superconducting layer An insulating layer 14 disposed on the outer periphery of the electrode 13 and a shield layer 15 disposed on the outer periphery of the insulating layer 14 are provided.

According to this, it is possible to cool the superconducting layer 13 and the shield layer 15 of the core 10 by utilizing the latent heat of evaporation of the liquid refrigerant flowing in the heat insulating pipe 30.

(5) In the superconducting cable system 110 according to (1) to (4) above, the liquid refrigerant is liquid nitrogen. In this way, it is possible to realize a reduction in weight and cost of a superconducting cable that transports power between a plurality of power devices mounted on an aircraft.

Details of Embodiments of the Present Disclosure
Hereinafter, embodiments of the present disclosure will be described based on the drawings. In the following drawings, the same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated.

(Example of application of superconducting cable system)
First, with reference to FIG. 1, an example of a scene where the superconducting cable system 110 according to the present embodiment is applied will be described. FIG. 1 is a schematic view showing an outline of an aircraft 1000 equipped with a superconducting cable system 110 according to the present embodiment. The aircraft 1000 is a hybrid electric aircraft using an engine and a motor as a power source.

The superconducting cable system 110 according to the present embodiment has a superconducting cable 100. The superconducting cable 100 is applied to a power cable that transports power between a plurality of power devices mounted on the aircraft 1000. In the example of FIG. 1, the aircraft 1000 is equipped with a plurality of power devices such as a generator 102, a motor 106,

power converters

104 and 108, a power distributor 111, and a power storage device 112. Only one of the four engines, motor 106 is shown. The superconducting cable 100 is disposed between these power devices to transport power.

The power cables mounted on the aircraft 1000 may have a total length of several tens of meters. If the power cable consists of an existing normal conducting cable (for example, an OF cable or CV cable), the weight of the power cable for transporting, for example, 4 MW three-phase AC power (AC frequency 400 Hz, rated voltage 230 V, rated current 10 kA) Is about 15 tons. Assuming two lines per motor, the total weight of the power cable is about 60 tons when replacing the two engines with the motor, and the ratio of the weight of the power cable to the total weight of the aircraft 1000 can not be ignored Become.

In recent years, in power cables in power facilities such as substations, development for practical use of superconducting cables is in progress. A superconducting cable has a smaller power transmission loss than a conventional normal conducting cable and can flow a large current, so that a lightweight and compact power cable can be realized. Therefore, from the viewpoint of reducing the weight of the power cable, application of the superconducting cable to a power cable for aircraft is expected.

Here, a superconducting cable typically employs a structure in which a core having a superconducting layer is accommodated in a heat insulating pipe, and the core is cooled by circulating liquid refrigerant (for example, liquid nitrogen) in the heat insulating pipe. . In this cooling structure, operation is performed by connecting a cooling system to the superconducting cable and supplying and circulating the liquid refrigerant from the cooling system into the heat insulating pipe. The cooling system includes a refrigerator for cooling the liquid refrigerant, a pump for pumping the liquid refrigerant, a reservoir tank for storing the liquid refrigerant, and the like, and constitutes a refrigerant flow path for circulating the liquid refrigerant together with the heat insulation pipe of the superconducting cable. The liquid refrigerant cooled by the refrigerator is fed into the heat insulating pipe, and the core is cooled by circulating the liquid refrigerant by the pump.

Therefore, when the superconducting cable is applied to a power cable for an aircraft, it is necessary to construct the cooling system described above in the aircraft 1000. Therefore, there is a concern that the weight of the cooling system is increased, and sufficient benefits can not be obtained from the viewpoint of weight reduction.

In the present embodiment, the configuration of a superconducting cable system suitable as a power cable for an aircraft will be described.

(Superconducting cable system)
Hereinafter, the configuration of the superconducting cable system 110 according to the present embodiment will be described.

First, the overall configuration of the superconducting cable system 110 will be described with reference to FIG. FIG. 2 is a schematic view of a superconducting cable system 110 disposed between two power devices mounted on the aircraft 1000 shown in FIG.

As shown in FIG. 2, the superconducting cable system 110 mainly includes a superconducting cable 100, a tank 130, a pump 131, a gas-liquid separator 132, and refrigerant pipes 133 to 136. As described later, the tank 130, the pump 131, and the refrigerant pipes 133 to 136, together with the heat insulation pipe 30 of the superconducting cable 100, constitute a circulation flow path for circulating the liquid refrigerant.

(Superconducting cable)
The superconducting cable 100 includes a core 10 having a superconducting layer. The core 10 is housed inside the heat insulation pipe 30. The superconducting cable 100 causes the liquid refrigerant to flow in the heat insulating pipe 30, thereby cooling the core 10 with the liquid refrigerant to bring it into a superconducting state, and is used for transporting power. In the following description, liquid nitrogen is used as the liquid refrigerant. Nitrogen has a melting point of about 63.1 K and a boiling point of about 77.3 K (atmospheric pressure).

The number of cores 10 stored in the heat insulation pipe 30 may be single core or multiple cores. The following description exemplifies a three-core collective type three-phase AC cable in which a three-core core 10 is twisted and housed in a heat insulation pipe.

FIG. 3 is a cross-sectional view taken along line III-III of FIG. FIG. 4 is a cross-sectional view showing the core 10 shown in FIG.

As shown in FIGS. 3 and 4, the superconducting cable 100 mainly includes a three-core core 10, a heat insulation pipe 30, a vacuum layer 31, a corrugated pipe 32, and a reinforcing layer (anticorrosion layer) 33. .

As shown in FIG. 4, the core 10 includes a former 12, an inner superconducting layer 13, an insulating layer 14, an outer superconducting layer 15, and a protective layer 16 in this order from the inside.

The former 12 maintains mechanical characteristics such as rigidity and bending characteristics of the core 10 and functions as a shunt for abnormal current. Specifically, when an accident such as a short circuit occurs in a power device to which the superconducting cable 100 is electrically connected, an abnormal current exceeding the current in the steady state occurs in the superconducting cable 100. Then, when a large current exceeding the critical current value Ic flows to the superconducting layer, the superconducting layer is transitioned (quenched) to normal conduction, and Joule loss (heat loss) occurs due to this transition. If the Joule loss is large, the core 10 constituting the superconducting layer may be burnt or the critical current value Ic may be reduced due to a rapid temperature rise even if the burn does not occur. When a large current is generated due to an accident such as a short circuit, heat generation of the superconducting layer can be suppressed by shunting the accident current to the former 12.

The former 12 has a hollow structure or a solid structure. Pipes or stranded wires made of a metal having a low electrical resistance (for example, copper or aluminum) can be suitably used.

The inner superconducting layer 13 is disposed on the outer periphery of the former 12. The inner superconducting layer 13 constitutes a power transmission path. As the inner superconducting layer 13, for example, a tape-shaped wire provided with an oxide superconductor can be suitably used. As the tape-shaped wire, for example, a Bi2223-based superconducting tape wire or an RE123-based thin film wire can be used. Examples of the Bi2223-based superconducting tape wire include a sheath wire in which a filament made of a Bi2223-based oxide superconductor is disposed in a stabilized metal such as Ag—Mn or Ag. The Bi2223 superconductor has a Bi2223 phase represented by a ratio of (Bismuth and Lead): Strontium: Calcium: Copper at an approximate ratio of 2: 2: 2: 3 as the main phase, with the balance being the Bi2212 phase and the Bi2223 phase. It means a material consisting of unavoidable impurities. Examples of the RE123-based thin film wire include a laminated wire in which an oxide superconducting phase of a rare earth element RE such as Y (yttrium), Ho (phornium), Sm (samarium), and Gd (gadolinium) is formed on a metal substrate. The RE123-based superconductor means a superconductor represented as REBa ₂ Cu ₃ O _y (y is 6 to 8, more preferably 7). The thing of the single layer structure formed by winding the said tape-shaped wire material helically, or a multilayer structure is mentioned. Although it simplifies and shows in FIG. 4, it is set as the superconducting layer 13 of a multilayer structure.

Insulating layer 14 is a layer for securing the insulation required for the working voltage in internal superconducting layer 13.

The outer superconducting layer 15 is disposed on the outer periphery of the insulating layer 14. As the outer superconducting layer 15, a tape-shaped wire including an oxide superconductor as in the case of the inner superconducting layer 13 can be suitably used. The oxide superconductor used for the outer superconducting layer 15 may be the same as that used for the formation of the inner superconducting layer 13. When the superconducting cable 100 is a three-phase AC cable, the outer superconducting layer 15 can be used as a shield layer for flowing a shield current induced by the current flowing in the inner superconducting layer 13.

Protective layer 16 is disposed on the outer periphery of outer superconducting layer 15. The protective layer 16 is intended to ensure the electrical insulation of the outer superconducting layer 15 and to mechanically protect the outer superconducting layer 15. The protective layer 16 is formed, for example, by spirally winding an insulating paper such as PPLP or kraft paper around the outer superconducting layer 15.

Returning to FIG. 3, the heat insulating pipe 30 houses the core 10 (excluding the terminal). As a material of the heat insulation pipe 30, copper, stainless steel or aluminum (alloy) can be suitably used. Insulating pipe 30 is, for example, a corrugated pipe. Liquid nitrogen 20 flows through the inside of the heat insulation pipe 30.

Inside the heat insulation pipe 30, the core 10 is cooled using liquid nitrogen 20. The latent heat of evaporation is used to cool the core 10.

The corrugated pipe 32 is disposed on the outer periphery of the heat insulating pipe 30. The corrugated pipe 32 is, for example, a corrugated cylindrical shape made of stainless steel. A space between the heat insulation pipe 30 and the corrugated pipe 32 is a vacuum layer 31 and is used as a heat insulation space. This space may be filled with a heat insulating material.

The reinforcing layer 33 (anticorrosion layer) is disposed on the outer periphery of the corrugated pipe 32. The reinforcing layer 33 is formed using, for example, polyvinyl chloride or the like.

(Liquid nitrogen circulation channel)
Returning to FIG. 2, the superconducting cable 100 has

end portions

120A and 120B at both ends in the longitudinal direction. The terminal unit 120 </ b> A accommodates one of the terminals in the longitudinal direction of the core 10. The terminal unit 120 </ b> B accommodates the other terminal in the longitudinal direction of the core 10. The terminal of the core 10 is electrically connected to the electrode 122 in each of the

terminal units

120A and 120B. The electrode 122 is electrically connected to a power device (not shown). The electrode 122 is formed of, for example, a conductive material such as a metal having a low electric resistance value near the temperature of liquid nitrogen, such as copper or aluminum.

The heat insulating pipe 30 is connected to the

end portions

120A and 120B, and the space in the

end portions

120A and 120B communicates with the inside of the heat insulating pipe 30, and is filled with liquid nitrogen.

The tank 130 stores liquid nitrogen. The tank 130 is connected to the terminal unit 120 </ b> A through the refrigerant pipe 133. The inside of the refrigerant pipe 133 and the space in the terminal portion 120A communicate with each other, and liquid nitrogen flows in the refrigerant pipe 133. When liquid nitrogen is supplied from the tank 130 into the end portion 120A via the refrigerant pipe 133, the liquid nitrogen is supplied into the heat insulation pipe 30 via the end portion 120A. The black arrows in FIG. 2 indicate the flow direction of liquid nitrogen. The liquid nitrogen flowing in the heat insulating pipe 30 flows into the space in the terminal portion 120B. The terminal unit 120 </ b> B is connected to the gas-liquid separator 132 via the refrigerant pipe 134. The space in the terminal portion 120 B communicates with the inside of the refrigerant pipe 134, and liquid nitrogen flows in the refrigerant pipe 134. The liquid nitrogen flowing in the refrigerant pipe 134 flows into the gas-liquid separator 132.

The gas-liquid separator 132 discharges nitrogen gas to the outside while suppressing the outflow of liquid nitrogen. As described above, in the inside of the heat insulating pipe 30, since the core 10 is evaporated and cooled using liquid nitrogen, the liquid nitrogen is vaporized to generate nitrogen gas. When a gas-liquid two-phase refrigerant mixed with nitrogen gas and liquid nitrogen is introduced into the gas-liquid separator 132, it is separated into liquid nitrogen and nitrogen gas, and the nitrogen gas is discharged to the outside of the gas-liquid separator 132 . The white arrows in FIG. 2 indicate the flow direction of nitrogen gas.

A pressure control valve 132A is disposed at the gas outlet of the gas-liquid separator 132. During operation of the aircraft 1000, the refrigerant pressure in the heat insulation pipe 30 may increase due to the inclination of the attitude of the airframe. Since the outside of the heat insulation pipe 30 is at atmospheric pressure or lower than atmospheric pressure, in such a case, both liquid nitrogen and nitrogen gas may be discharged from the gas outlet of the gas-liquid separator 132. The pressure control valve 132A is installed at the gas outlet, and can maintain the pressure difference between the refrigerant pressure in the heat insulation pipe 30 and the external pressure. Thus, the nitrogen gas can be efficiently discharged to the outside without flowing out the liquid nitrogen from the heat insulation pipe 30, including the case where the airframe is greatly inclined.

5 to 7 are cross-sectional views schematically showing the configuration example of the gas-liquid separator 132 shown in FIG. In the gas-liquid separator 132, generally, a gas-liquid separator using centrifugal force (FIG. 5), a gas-liquid separator using surface tension (FIG. 6), and a gas-liquid separation coalescer (FIG. 7) And so on can be used.

FIG. 5 is a cross-sectional view schematically showing the structure of a centrifugal gas-liquid separator. As shown in FIG. 5, a gas-liquid two-phase inlet 140 into which a gas-liquid two-phase refrigerant flows is provided on the side of the separator main body 143. A gas outlet 141 from which gas is output is provided at the top of the separator body 143, and a liquid outlet 142 from which liquid is output is provided at the bottom of the separator body 143. A spiral flow passage is formed inside the separator body 143, and one end of the spiral flow passage communicates with the gas-liquid two-phase inlet 140. A liquid outlet 142 is provided on the other end side of the spiral flow channel and in communication with the outer peripheral side portion of the spiral flow channel viewed from the axial direction of the spiral flow channel, and viewed from the axial direction of the spiral flow channel A gas outlet 141 is provided to communicate with the inner peripheral side portion of the helical flow passage.

The gas-liquid two-phase refrigerant flowing from the gas-liquid two-phase inlet 140 is given a swirling component by a spiral flow path, and is separated into liquid nitrogen and nitrogen gas by its centrifugal force. That is, since liquid nitrogen having a large specific gravity is subjected to a larger centrifugal force, it gathers on the outer peripheral side of the spiral channel, while nitrogen gas having a small specific gravity collects on the other part, that is, the inner peripheral side of the spiral channel. It will be.

FIG. 6 is a cross-sectional view schematically showing the structure of a surface tension type gas-liquid separator. As shown in FIG. 6, a gas-liquid two-phase inlet 140 is provided at the upper portion of the separator body 143, a gas outlet 141 is provided at the side of the separator body 143, and the lower portion of the separator body 143. A liquid outlet 142 is provided.

A bellows-like groove 144 is formed on the inner peripheral surface of the separator body 143. Between the upper portion of the groove 144 and the gas-liquid two-phase inlet 140, the gas-liquid two-phase flow is guided to the groove 144, and the gas released from the groove 144 is prevented from backflowing to the gas-liquid two-phase inlet 140 The partition 143A for doing is arranged. Between the lower portion of the groove 144 and the gas outlet 141 and the liquid outlet 142, a partition 143B for guiding the gas and liquid having passed through the groove 144 to the respective outlets is disposed.

When the gas-liquid two-phase refrigerant flows in from the upper portion of the bellows-like groove portion 144, the gas-liquid two-phase refrigerant contacts the groove portion 144. The gas-liquid two-phase refrigerant in contact with the groove 144 is separated into liquid nitrogen and nitrogen gas by the surface tension of the liquid nitrogen. The separated liquid nitrogen is collected after flowing along the groove 144 and flows out from the liquid outlet 142. Nitrogen gas is exhausted from the gas outlet 141.

FIG. 7 is a cross-sectional view schematically showing the structure of the gas-liquid separation coalescer. As shown in FIG. 7, a coalescer cartridge 145 having a microfiber structure is installed inside the separator body 143. The gas-liquid two-phase refrigerant flowing from the gas-liquid two-phase inlet 140 flows into the coalescer cartridge 145. While passing through the coalescer cartridge 145, liquid nitrogen contained in the gas-liquid two-phase refrigerant is separated and collected at the lower part of the separator body 143. Liquid nitrogen flows out of a liquid outlet 142 provided at the bottom of the separator body 143. After passing through the coalescer cartridge 145, the nitrogen gas is exhausted from a gas outlet 141 provided on the top of the separator body 143.

Returning to FIG. 2, the liquid outlet 142 of the gas-liquid separator 132 is connected to the tank 130 via

refrigerant pipes

135 and 136. The pump 131 is connected between the refrigerant pipe 135 and the refrigerant pipe 136. The liquid outlet 142 of the gas-liquid separator 132 and the inside of the refrigerant pipe 135 are in communication, and the liquid nitrogen drawn out from the gas-liquid separator 132 flows in the refrigerant pipe 135. The liquid nitrogen is pumped by the pump 131 and supplied into the tank 130 via the refrigerant pipe 136. That is, liquid nitrogen is supplied from the tank 130 to the terminal portion 120A through the refrigerant pipe 133 and flows in the heat insulating pipe 30. The liquid refrigerant having flowed in the heat insulating pipe 30 is discharged from the terminal portion 120B, returned to the tank 130 via the refrigerant pipe 134, the gas-liquid separator 132, the refrigerant pipe 135, the pump 131 and the refrigerant pipe 136, and heat insulation again. It is fed into the tube 30. That is, the heat insulating pipe 30, the

end portions

120A and 120B, the refrigerant pipes 133 to 135, the tank 130, the gas-liquid separator 132, and the pump 131 constitute a circulation channel of liquid nitrogen, and liquid nitrogen circulates in this circulation channel. .

During the period from the takeoff to the landing of the aircraft 1000, liquid nitrogen is heated by AC loss generated in the core 10, heat entering from the outside of the heat insulation pipe 30, and the like. By storing liquid nitrogen cooled to a boiling point (77.3 K) or so at atmospheric pressure before taking off the aircraft 1000, the liquid nitrogen circulates in the above-described circulation path after taking off the aircraft 1000. The temperature of the liquid nitrogen is maintained at a temperature near the boiling point until all the liquid nitrogen in the circulation flow path is vaporized. The tank 130 stores an amount of liquid nitrogen necessary to cool the core 10 to a superconducting state, based on the loss generated during the operation period from the takeoff to the landing of the aircraft 1000. For example, if the time when the load is 100% for 24 hours operation time is 1 hour and the time when the load is 33% is 23 hours, the amount of liquid nitrogen to be initially stored in the tank 130 is about 700 kg It is. According to this, it is possible to prevent all the liquid nitrogen in the circulation channel from being vaporized before the aircraft 1000 lands.

Since nitrogen gas is generated in the adiabatic pipe 30, the refrigerant pressure in the adiabatic pipe 30 increases if the nitrogen gas is not discharged, and the cooling of the core 10 becomes insufficient, and the temperature of the core 10 rises. there's a possibility that. Therefore, in order to maintain the temperature of the core 10, it is necessary to discharge nitrogen gas.

Here, if the heat insulation pipe 30 is always arranged horizontally with respect to the ground, a discharge hole for discharging nitrogen gas is formed in a part of the heat insulation pipe 30, and nitrogen gas is discharged autonomously through this discharge hole. In the case of the aircraft 1000, the aircraft 1000 can take various attitudes while operating. For example, if the aircraft 1000 is inclined at an angle close to perpendicular to the ground, the superconducting cable 100 may also incline at an angle close to perpendicular to the ground. In such a case, there is a possibility that liquid nitrogen inside the heat insulation pipe 30 gathers downward according to gravity, and the liquid nitrogen may leak to the outside from the discharge hole. In order to prevent leakage of liquid nitrogen, the superconducting cable 100 needs to have a sealed structure, which makes it difficult to discharge liquid nitrogen autonomously.

Therefore, in the present embodiment, the nitrogen gas generated in the heat insulation pipe 30 is discharged to the outside by using the gas-liquid separator 132 by providing the gas-liquid separator 132 in the circulation flow path.

When the superconducting cable 100 is also inclined at an angle close to perpendicular to the ground because the airframe of the aircraft 1000 is inclined at an angle close to perpendicular to the ground, the liquid nitrogen 20 inside the heat insulation pipe 30 is moved downward according to gravity. Gather in Since the inside of the heat insulation pipe 30 is a single space, this state can be compared with the state in which the elongated container contains liquid nitrogen. Therefore, in the heat insulating pipe 30 serving as the container, a pressure corresponding to the depth from the liquid surface of liquid nitrogen is applied to the portion located on the lower side in the direction of gravity. Since the pressure increases as the length of the heat insulating tube 30 increases, the heat insulating tube 30 has sufficient robustness to withstand the pressure.

Further, the maximum discharge pressure of the pump 131 is set to be equal to or higher than the pressure of the liquid nitrogen by its own weight so that the circulation of the liquid nitrogen can be maintained regardless of the attitude of the aircraft 1000.

(Example of operation of superconducting cable system)
Next, an operation example of the superconducting cable system 110 according to the present embodiment will be described.

First, before the takeoff of the aircraft 1000, the inside of the tank 130 is filled with liquid nitrogen. In this process, for example, liquid nitrogen saturated at boiling point (77.3 K) at atmospheric pressure is supplied to the inside of the tank 130. In the tank 130, an amount of liquid nitrogen necessary to cool the core 10 to a superconducting state is stored in a period from the takeoff to the landing of the aircraft 1000.

FIG. 8 schematically shows temporal changes in the temperature and amount of liquid nitrogen present in superconducting cable system 110.

As shown in FIG. 8, the supply of liquid nitrogen to the tank 130 is started at time t0. Liquid nitrogen is cooled to a temperature near the boiling point (77.3 K). When a prescribed amount of liquid nitrogen is stored inside the heat insulation pipe 30 at time t1, the supply of liquid nitrogen to the tank 130 is stopped.

When the aircraft 1000 takes off at time t2 after time t1, by operating the pump 131, circulation of liquid nitrogen in the circulation flow path is started, and liquid nitrogen flows in the heat insulation pipe 30. At this time, the liquid nitrogen is heated by the AC loss generated in the core 10 and the heat of external penetration. Because the core 10 is cooled using the latent heat of vaporization of liquid nitrogen, the temperature of the liquid nitrogen is maintained near the boiling point during operation of the aircraft 1000. The nitrogen gas generated by the evaporative cooling is introduced into the gas-liquid separator 132 together with liquid nitrogen, and is discharged to the outside of the gas-liquid separator 132.

After time t2, the amount of liquid nitrogen gradually decreases. When the aircraft 1000 lands at time t3, most of the liquid nitrogen in the tank 130 is consumed.

After time t3, the liquid nitrogen is again supplied to the tank 130 in preparation for the operation of the aircraft 1000.

As described above, according to the superconducting cable system 110 according to the present embodiment, the core 10 is cooled using the latent heat of vaporization of liquid nitrogen flowing in the heat insulating pipe 30. Therefore, a refrigerator for cooling liquid nitrogen to a state of supercooling becomes unnecessary, as compared with the conventional cooling technique of a superconducting cable in which a core is cooled by circulation using a subcooled refrigerant. Therefore, when the superconducting cable system 110 is applied to a power cable for transporting electric power in an aircraft, it is not necessary to connect a refrigerator to the superconducting cable, so the weight of the power cable can be reduced. Therefore, superconducting cable 100 according to the present embodiment can contribute to the realization of an electric aircraft capable of reducing fuel consumption and environmental load.

Further, by providing the gas-liquid separator 132 in the circulation path of liquid nitrogen, it is possible to suppress that the pressure of the refrigerant in the heat insulation pipe 30 is increased by the nitrogen gas generated by the evaporative cooling of the core 10.

In the embodiment described above, although the configuration in which the tank 130 is filled with liquid nitrogen at a temperature near the boiling point has been described, it may be configured to receive liquid nitrogen cooled to a temperature below the boiling point. In this way, since the core 10 can be cooled using the sensible heat and the latent heat of evaporation of liquid nitrogen, more liquid refrigerant is used than when the core 10 is cooled using the latent heat of evaporation alone. It can absorb heat. Therefore, even when the operation time of the aircraft 1000 is long or the Joule loss (heat loss) generated in the power cable is large, the core 10 can be constantly cooled and maintained in the superconducting state.

Further, although the configuration in which the superconducting cable system 110 is used for AC power transmission (for example, three-phase AC power transmission) has been described in the above embodiment, the superconducting cable system according to the present embodiment is DC power transmission (for example, bipole power transmission) , Monopole power transmission).

It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the embodiments described above but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

10 core, 12 former, 13 inner superconducting layer, 14 insulating layer, 15 outer superconducting layer (shield layer), 16 protective layer, 20 liquid nitrogen, 30 adiabatic tube, 31 vacuum layer, 32 corrugated tube, 33 reinforcing layer, 100 superconducting Cable, 110 superconducting cable system, 102 generator, 104, 108 power converter, 106 motor, 111 power distributor, 112 power storage device, 120A, 120B terminal part, 122 electrode, 130 tank, 131 pump, 132 gas-liquid separator , 132A pressure control valve, 133 to 136 refrigerant piping, 140 gas-liquid two-phase inlet, 141 gas outlet, 142 liquid outlet, 143 separator main body, 143A, 143B partition body, 144 groove portion, 145 coreless cartridge, 1000 aircraft.

Claims

A superconducting cable system for transporting power between a plurality of power devices mounted on an aircraft, comprising:
An insulating pipe for circulating liquid refrigerant,
A core having a superconducting layer housed in the heat insulating pipe;
A tank for storing the liquid refrigerant;
A pump installed in a circulation flow path of the liquid refrigerant including the tank and the heat insulating pipe, and circulating the liquid refrigerant;
And a gas-liquid separator, disposed in the circulation flow path, for discharging a gas refrigerant in which the liquid refrigerant is vaporized.
The superconducting cable system according to claim 1, wherein the tank is filled with the liquid refrigerant cooled to a boiling point temperature.
The superconducting cable system according to claim 1, wherein the gas-liquid separator has a pressure control valve disposed at an outlet of the gas refrigerant.
The core is
With the former
The superconducting layer disposed on the outer periphery of the former;
An insulating layer disposed on the outer periphery of the superconducting layer;
The superconducting cable system according to any one of claims 1 to 3, further comprising: a shield layer disposed on an outer periphery of the insulating layer.
The superconducting cable system according to any one of claims 1 to 4, wherein the liquid refrigerant is liquid nitrogen.