Liquefied gas boosting pump

Abstract

A liquefied gas boosting pump 10 comprises: a storage tank 12 having an intake port 16a and a delivery port 17a; a casing 22 having a liquefied gas delivery path 25 including a suction port 26a, a discharge port 27a, and an impeller placement part 28 formed therebetween; an impeller 52 placed in the impeller placement part 28; and a superconducting motor 45 having a motor shaft 49 which protrudes from a motor body 46 into the impeller placement part 28 and to which the impeller 52 is attached.

Description

Liquefied gas booster pump

[0001] The present invention relates to a liquefied gas booster pump.

[0002] Pumps that pressurize and deliver liquefied gas, such as liquid hydrogen, which has a lower density than water at the same temperature, are known. The pump system disclosed in Patent Document 1 includes two pump units connected in series within a barrel capable of storing a fixed amount of liquefied gas. Each pump unit includes a motor and a multi-stage impeller with multiple impellers arranged in series within a casing. This allows the impellers to be multi-staged without a shortage of power, enabling the liquefied gas to be pressurized and delivered.

[0003] JP 2022-184024 A

[0004] The pump system of Patent Document 1 has two pump units using multi-stage impellers arranged inside a barrel, which disadvantageously increases the overall system size. In other words, Patent Document 1 does not give any consideration to efficiently delivering liquefied gas while preventing the overall pump size from increasing.

[0005] An object of the present invention is to deliver liquefied gas with high efficiency while preventing the overall size of the pump from increasing.

[0006] The liquefied gas boost pump of the present invention comprises a storage tank having an inlet and a delivery port for storing liquefied gas taken in through the inlet, a casing disposed within the storage tank and having a suction port that opens to face the inside of the storage tank, a discharge port that communicates with the delivery port, and a liquefied gas delivery path including an impeller arrangement section formed between the suction port and the discharge port, and a pump disposed within the impeller arrangement section that rotates to draw the liquefied gas in the storage tank through the suction port and deliver it from the delivery port. a superconducting motor having an impeller for rotating the impeller, a motor main body disposed within the casing, and a motor shaft protruding from the motor main body toward the impeller arrangement section for rotating the impeller, wherein the casing is formed with a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and that is a space in which the motor main body is disposed, and a cooling flow path that spatially communicates the storage tank with the motor arrangement section and that cools the superconducting motor with the liquefied gas. In a first aspect, there is provided a liquefied gas boost pump, wherein the suction port of the liquefied gas delivery path is provided between the impeller arrangement section and the motor arrangement section, and the cooling flow path has a first inlet portion that communicates with the motor arrangement section and opens to face the inside of the storage tank, and a first outlet portion that communicates with the motor arrangement section on a side of the liquefied gas delivery path upstream of the impeller arrangement section. In a second aspect, there is provided a liquefied gas boost pump, wherein the suction port of the liquefied gas delivery passage is provided between the impeller arrangement section and the motor arrangement section, and the cooling flow passage has a first inlet portion communicating with the motor arrangement section at a portion of the liquefied gas delivery passage upstream of the impeller arrangement section, and a first outlet portion communicating with the motor arrangement section and opening to face the inside of the storage tank.In a third aspect, there is provided a liquefied gas boost pump, wherein the suction port of the liquefied gas delivery passage is provided between the impeller arrangement section and the motor arrangement section, and the cooling flow passage has a first inlet portion and a first outlet portion communicating with the motor arrangement section and opening to face the inside of the storage tank.In a fourth aspect, the motor shaft protrudes in both directions from the motor body, the impeller arrangement section includes a first arrangement section and a second arrangement section that are arranged at an interval in the axial direction of the motor shaft, the impeller includes a first impeller arranged in the first arrangement section and a second impeller arranged in the second arrangement section, the motor arrangement section is provided between the first arrangement section and the second arrangement section, the cooling flow path communicates with the first arrangement section and is connected to the storage tank via the liquefied gas delivery path. a second inlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, and a return port for directly returning the liquefied gas from the motor arrangement portion to the impeller arrangement portion, the second inlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, the second outlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, and a second outlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, the second inlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, the second outlet ... outlet port communicating with the impeller arrangement portion and the interior of the reservoir tank via the liquefied gas delivery path, the second in

[0007] When a normal conduction motor (a general-purpose three-phase motor) is used as a drive source to pump liquefied gases such as liquid hydrogen, which are colder than water, it is difficult to start the motor because it is difficult to rotate due to the difficulty in linking magnetic flux and generating induced electromotive force. Furthermore, heat loss can cause the liquefied gas to heat up and gasify, which reduces the efficiency of pumping the liquefied gas. Here, "lower than water" means that the temperature at which the gas can remain liquid is lower than that of water at the same pressure.

[0008] In this embodiment, a superconducting motor, which has higher motor efficiency than a normal conducting motor, is used as the drive source, allowing for highly efficient pumping of liquefied gas. Vaporization of the liquefied gas due to heat loss can also be suppressed. Furthermore, the axial length of the motor shaft can be shortened compared to when two pump units using normal conducting motors are arranged, allowing for a more compact overall system.

[0009] In the present invention, liquefied gas can be delivered with high efficiency while preventing the overall size of the pump from increasing.

[0010] 1 is a schematic diagram of a hydrogen receiving facility using a liquefied gas boost pump of the present invention. FIG. 1 is a cross-sectional view of a liquefied gas boost pump according to a first embodiment. FIG. 2 is an enlarged cross-sectional view of the outflow section of FIG. 2. FIG. 1 is a cross-sectional view of a liquefied gas boost pump according to a second embodiment. FIG. 2 is a cross-sectional view of a liquefied gas boost pump according to a third embodiment. FIG. 3 is a cross-sectional view of a liquefied gas boost pump according to a fourth embodiment. FIG. 3 is a cross-sectional view of a liquefied gas boost pump according to a fifth embodiment. FIG. 4 is a cross-sectional view of a liquefied gas boost pump according to a sixth embodiment. FIG. 4 is a cross-sectional view of a liquefied gas boost pump according to a seventh embodiment. FIG. 5 is an enlarged cross-sectional view of a portion of FIG. 9. FIG. 10 is a cross-sectional view of a liquefied gas boost pump according to an eighth embodiment. FIG. 11 is a cross-sectional view of a liquefied gas boost pump according to an eleventh embodiment. FIG. 12 is a cross-sectional view of a liquefied gas boost pump according to a thirteenth embodiment. FIG. 14 is a cross-sectional view of a liquefied gas boost pump according to a fourteenth embodiment. FIG. 15 is a cross-sectional view of a liquefied gas boost pump according to a fifteenth embodiment. A cross-sectional view of a liquefied gas boost pump according to a sixteenth embodiment. A cross-sectional view of a liquefied gas boost pump according to a seventeenth embodiment. A cross-sectional view of a liquefied gas boost pump according to an eighteenth embodiment. A cross-sectional view of a liquefied gas boost pump according to a nineteenth embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] A liquefied gas boost pump (hereinafter simply referred to as "pump") 10 of the present invention is used in, for example, hydrogen receiving facility 1 shown in Figure 1, and supplies liquefied hydrogen in tank 2 to gas turbine 4 via vaporizer 3. However, pump 10 can also be used in tank discharge facilities other than hydrogen receiving facility 1, and can also be used to supply fuel to aircraft and ships. Pump 10 can also deliver liquefied gases other than liquefied hydrogen.

[0013] In addition to liquefied hydrogen, liquefied gases that can be delivered by the pump 10 include liquefied helium, liquefied neon, liquefied nitrogen, liquefied argon, liquefied natural gas, liquefied carbon dioxide, liquefied petroleum gas, and liquefied ammonia. Compared to water, these liquefied gases have lower temperatures, lower boiling points, lower viscosities, and lower densities. Specifically, the boiling point of liquefied helium is −269°C, that of liquefied hydrogen is −253°C, that of liquefied neon is −246°C, that of liquefied nitrogen is −196°C, that of liquefied argon is −186°C, that of liquefied natural gas is −162°C, that of liquefied carbon dioxide is −78°C, that of liquefied petroleum gas is −42°C, and that of liquefied ammonia is −33°C.

[0014] (First embodiment) Referring to Figure 2, a pump 10 of the first embodiment is composed of a barrel (storage tank) 12 that stores a fixed amount of liquefied gas, and one pump unit 20 arranged inside the barrel 12, and delivers the liquefied gas inside the barrel 12 without vaporizing it.

[0015] The barrel 12 includes a cylindrical outer peripheral wall 13, a bottom wall 14 closing the lower end of the outer peripheral wall 13, and a top wall 15 closing the upper end of the outer peripheral wall 13. This barrel 12 is configured such that at least the top wall 15 is formed separately from the outer peripheral wall 13 and they are joined liquid-tightly. However, the outer peripheral wall 13 may be polygonal cylindrical, and the barrel 12 may have any configuration as long as both ends of the cylindrical outer peripheral wall 13 are closed. Furthermore, the amount of liquefied gas stored in the barrel 12 is sufficient as long as the liquid level is above the intake port 16a. Furthermore, the upper end of the outer peripheral wall 13 may be open as long as the liquefied gas in the barrel 12 does not leak.

[0016] The outer peripheral wall 13 is provided with a cylindrical intake portion 16 that protrudes radially outward. The top wall 15 is provided with a cylindrical delivery portion 17 that protrudes outward along the axis A of the outer peripheral wall 13 (barrel 12). The outer end opening of the intake portion 16 constitutes an intake port 16a, which is connected to, for example, the tank 2 shown in FIG. 1 and can introduce liquefied gas into the barrel 12. The outer end opening of the delivery portion 17 constitutes a delivery port 17a, which is connected to, for example, the vaporizer 3 shown in FIG. 1. However, instead of providing the cylindrical intake portion 16 and delivery portion 17, the intake port 16a may be provided directly on the outer peripheral wall 13 and the delivery port 17a may be provided directly on the top wall 15. Alternatively, the intake portion 16 may be provided on the top wall 15. The position of the intake portion 16 can be changed as needed as long as the intake portion 16 can take in liquefied gas. The delivery portion 17 can be provided on the outer peripheral wall 13. The position of the delivery portion 17 can be changed as needed as long as the delivery portion 17 can deliver liquefied gas. In addition, for ease of maintenance, it is preferable to provide a valve for discharging the remaining liquefied gas and a valve for discharging the air in the barrel 12. However, if the intake section 16 and the delivery section 17 are provided in the top wall 15, the valve for discharging the air is not necessary.

[0017] 2 , the pump unit 20 is configured as a vertical-shaft turbo-type multi-stage diffuser pump. The pump unit 20 includes a casing 22 in which a liquefied gas delivery passage 25, a motor mounting section 30, and a cooling passage 31 are formed. The pump unit 20 also includes a superconducting motor 45, an impeller 52, and a plurality of bearings 55, 56, and 57, which are disposed within the casing 22.

[0018] The pump unit 20 of this embodiment is submerged in the liquefied gas in the barrel 12, and by rotating the impeller 52 by the superconducting motor 45, the liquefied gas in the barrel 12 is pressurized and discharged from the discharge port 17a.

[0019] First, the configuration other than the casing 22 will be specifically described.

[0020] The superconducting motor 45 includes a motor body 46 and a motor shaft 49, and has a higher output density per unit mass than a normal conducting motor (a general-purpose three-phase motor). This allows the mass of the rotor 48 included in the motor body 46 to be reduced, and the eigenvalues ​​of all rotating bodies including the impeller 52 and the rotor 48 to be increased, making it suitable for high-speed rotation. In this embodiment, a superconducting motor 45 is used in which the rotation speed of the motor shaft 49 is constant (fixed speed). However, the superconducting motor 45 may be configured so that the rotation speed of the motor shaft 49 can be changed by inverter control.

[0021] The motor body 46 is mounted within the motor mounting section 30 of the casing 22. The motor body 46 includes a cylindrical stator 47 fixed to the motor casing 22 and a cylindrical rotor 48 disposed within the stator 47. The superconducting motor 45 of this embodiment is configured with a stator 47 having a configuration similar to that of a normal conducting motor, and a rotor 48 using superconducting wires. For example, the stator 47 has the same structure as a squirrel-cage induction motor, and the magnetic field formed by the coils generates a rotating magnetic field in synchronization with the AC power supply. The rotor 48 is configured with superconducting wires electrically connected to conductor rods and end rings, and rotates due to the rotating magnetic field of the stator 47. However, the superconducting motor 45 may be a fully superconducting motor in which both the stator 47 and the rotor 48 use superconducting wires.

[0022] The motor shaft 49 is attached to the rotor 48 of the motor body 46 so as to be unable to move relative to it in either the circumferential or axial direction, and protrudes upward and downward (in both directions) from the motor body 46. A main portion 49a of the motor shaft 49 protruding downward protrudes into the impeller mounting portion 28 of the liquefied gas delivery passage 25 of the casing 22. A sub-portion 49b of the motor shaft 49 protruding upward protrudes into the bearing mounting portion 34 of the cooling passage 31 of the casing 22. The axis (axial direction) of the motor shaft 49, the axis of the casing 22, and the axis A of the barrel 12 are all coincident. In other words, the motor shaft 49 extends along the axis A, and the axial direction of the motor shaft 49 is coincident with the axis A.

[0023] The impeller 52 rotates integrally with the motor shaft 49, sucks the liquefied gas in the barrel 12 into the liquefied gas delivery passage 25 of the casing 22, and delivers it from the delivery port 17a. The impeller 52 is disposed in the impeller mounting portion 28 of the casing 22 located below the motor main body 46, and is attached so as to be immovable relative to the main portion 49a of the motor shaft 49 in both the circumferential and axial directions. The impeller 52 of this embodiment is a single-suction type, and is configured as a multi-stage impeller in which multiple (ten in this embodiment) closed impellers 53 are arranged in series with spaces in the axial direction of the motor shaft 49. The number of closed impellers 53 can be changed depending on the liquefied gas to be delivered.

[0024] The multiple bearings 55, 56, and 57 are attached to the casing 22 at intervals in the axial direction of the motor shaft 49 and rotatably support the motor shaft 49. In this embodiment, one magnetic bearing (axial bearing) 55, one touchdown bearing 56 formed by a rolling bearing, and three rolling bearings (radial bearings) 57 are used. In the following description, the three rolling bearings 57 are sometimes referred to as rolling bearings 57A, 57B, and 57C, from top to bottom. However, the number of magnetic bearings 55 and rolling bearings 57 can be changed as needed. However, it is preferable that the number of magnetic bearings 55 is two or less and the number of rolling bearings 57 is two or more. Furthermore, the arrangement of the magnetic bearings 55 and rolling bearings 57 can be changed as needed.

[0025] The magnetic bearing 55 is disposed in the bearing arrangement portion 34 of the casing 22 located above the motor main body 46 and supports the secondary portion 49b of the motor shaft 49. The magnetic bearing 55 is disposed on the opposite side of the rolling bearing 57A from the motor main body 46. The magnetic bearing 55 is an axial bearing that includes a substrate and an electromagnet and receives the axial load of the motor shaft 49 without contact. The substrate is made of a ferromagnetic metal and is attached to the secondary portion 49b of the motor shaft 49 so as to be immovable relative to the substrate in both the circumferential and axial directions. The electromagnet is attached to the bearing arrangement portion 34 so as to be spaced apart from the substrate in the axial direction of the motor shaft 49. However, the magnetic bearing 55 may be a superconducting magnetic bearing using a superconducting coil as the electromagnet. Alternatively, a permanent magnet may be used instead of the electromagnet. Alternatively, a rolling bearing or a plain bearing capable of supporting the axial direction may be used instead of the magnetic bearing 55. Further, other members may be interposed between the magnetic bearing 55 and the rolling bearing 57 .

[0026] Touchdown bearing 56 and rolling bearing 57 each include an inner ring that is attached to motor shaft 49 so as to be immovable relative to it in both the circumferential and axial directions, an outer ring that is attached to casing 22, and a plurality of rolling elements that are arranged to be able to roll between the inner and outer rings. Of these, touchdown bearing 56 is an axial bearing that receives the axial load of motor shaft 49, and rolling bearing 57 is a radial bearing that receives the radial load of motor shaft 49.

[0027] The touchdown bearing 56 is disposed above the magnetic bearing 55 and supports the tip of the sub-portion 49b of the motor shaft 49. The touchdown bearing 56 prevents the board from coming into contact with the electromagnet when the magnetic bearing 55 is not operating, and functions as a fail-safe device to prevent damage to the magnetic bearing 55.

[0028] Rolling bearing 57A is disposed intermediate motor body 46 and magnetic bearing 55 and supports the base end of sub-section 49b of motor shaft 49. Rolling bearing 57B is disposed intermediate motor body 46 and impeller 52 and supports the base end of main section 49a of motor shaft 49. Rolling bearing 57C is disposed below impeller 52 and supports the tip end of main section 49a of motor shaft 49. However, if there are no problems with the analysis results of the natural frequencies and displacements of all rotating bodies including impeller 52 and rotor 48, rolling bearing 57C may be unnecessary. Also, a magnetic bearing or a sliding bearing capable of supporting in the radial direction may be used instead of rolling bearing 57.

[0029] An inducer 58 is disposed between the rolling bearing 57C and the impeller 52. The inducer 58 is attached to the tip of the main portion 49a of the motor shaft 49 so as to be unable to move relative to it in either the circumferential or axial direction, and rotates integrally with the motor shaft 49. This promotes the suction of liquid by the impeller 52. However, if the amount of liquid suction by the impeller 52 can be ensured, the inducer 58 does not have to be disposed.

[0030] As described above, in a configuration in which the impeller 52 is disposed on the motor shaft 49 of the superconducting motor 45, the high motor efficiency of the superconducting motor 45 allows for highly efficient delivery of liquefied gas, and also suppresses evaporation of the liquefied gas due to heat loss. Although the magnetic bearing 55 requires a control unit 60 to control the magnetic force, it can support the motor shaft 49 in a contactless manner and is free from wear, allowing for semi-permanent use. Unlike the magnetic bearing 55, the rolling bearing 57 does not require a control unit, thereby reducing the manufacturing cost of the pump 10. In this embodiment, the use of the magnetic bearing 55 and the rolling bearing 57 minimizes cost increases and improves support performance. Furthermore, if a superconducting magnetic bearing is used as the magnetic bearing 55, a strong repulsive levitation force can be achieved by the pinning effect of the magnetic flux.

[0031] The pump 10 of this embodiment includes a control unit 60 that controls the superconducting motor 45 and the magnetic bearings 55. The control unit 60 is constructed of hardware including a central processing unit (CPU), random access memory (RAM), and memory devices such as read-only memory (ROM), and software implemented therein. However, the superconducting motor 45 and the magnetic bearings 55 may be controlled individually by separate control units.

[0032] The control unit 60 rotates the motor shaft 49 of the superconducting motor 45 at a high speed at a specified rotation speed, for example, by an operator operating an operating unit (not shown). The control unit 60 also controls the magnetic bearing 55 based on the detection results of a distance measurement sensor (detector) 61 that detects the end position of the motor shaft 49, i.e., the axial movement of the motor shaft 49. Specifically, the control unit 60 adjusts the amount of current passed through the electromagnet of the magnetic bearing 55 to adjust the axial support force of the motor shaft 49 provided by the magnetic bearing 55, thereby restricting the motor shaft 49 and the rotor 37 of the balance piston 35 (described in detail below) to predetermined positions. However, the magnetic bearing including the superconducting magnetic bearing is not limited to an active type and may be a passive type. The superconducting motor 45 may also be configured to include an axial balance mechanism.

[0033] Next, the configuration of the casing 22 will be described in detail.

[0034] 2 , the casing 22 is fixed to the top wall 15 of the barrel 12 and hangs down along the axis A of the barrel 12. As described above, the casing 22 includes the liquefied gas delivery passage 25, the motor arrangement portion 30, and the cooling passage 31.

[0035] The liquefied gas delivery passage 25 includes a suction section 26 , a discharge section 27 , and an impeller arrangement section 28 , and extends from the lower end to the upper end of the casing 22 .

[0036] The suction section 26 is provided at the lower end of the casing 22 and protrudes downward to form a cylindrical shape. The opening at the lower end of the suction section 26 forms an suction port 26a for sucking liquefied gas inside the barrel 12. The suction port 26a is located above the bottom wall 14 of the barrel 12 with a gap therebetween and opens to face the inside of the barrel 12. However, the suction port 26a may be provided directly at the lower end of the casing 22 without providing a cylindrical suction section 26.

[0037] A rolling bearing 57C and an inducer 58 are disposed within the suction section 26. The rolling bearing 57C separates the interior of the impeller mounting section 28 from the interior of the barrel 12. The interior of the impeller mounting section 28 and the interior of the barrel 12 are spatially connected via the rolling bearing 57C. In this embodiment, a communication hole 26b is provided in the mounting seat of the rolling bearing 57C within the suction section 26. The communication hole 26b ensures the amount of liquefied gas suctioned into the liquefied gas delivery path 25.

[0038] The discharge section 27 is provided at the top of the casing 22 and communicates with the suction section 26 via the impeller mounting section 28. The discharge section 27 is connected to the outer periphery of the upper end of the impeller mounting section 28 and extends upward, bypassing the motor mounting section 30 and the cooling flow path 31. The upper end of the discharge section 27 is a discharge port 27a for discharging the liquefied gas. The discharge port 27a opens on the axis A at the upper end of the casing 22 so as to be located directly below the delivery section 17 of the barrel 12. As a result, the discharge port 27a communicates with the delivery port 17a.

[0039] The impeller arrangement section 28 communicates with the upper end of the suction section 26 including the suction port 26a and the lower end of the discharge section 27 including the discharge port 27a, and extends along the axis A. The impeller arrangement section 28 is provided with a plurality of annular partition walls 28a that separate adjacent closed impellers 53 of the impellers 52.

[0040] By configuring the liquefied gas delivery path 25 in this manner, the liquefied gas in the barrel 12 is sucked in through the suction port 26a by the rotation of the impeller 52 and the inducer 58 by the superconducting motor 45. The liquefied gas then passes through the suction section 26, the impeller arrangement section 28, and the discharge section 27 in this order, and is discharged from the discharge port 27a. The liquefied gas then passes through the delivery section 17 and is delivered from the delivery port 17a.

[0041] The motor mounting section 30 is a space for arranging the motor body 46 of the superconducting motor 45. The motor mounting section 30 is provided in the casing 22 between the upper and lower ends of the discharge section 27, and extends along the axis A. In other words, the motor mounting section 30 is provided adjacent to the upper side of the impeller mounting section 28, which is on the discharge port 27a side.

[0042] A rolling bearing 57B is disposed between the motor mounting section 30 and the impeller mounting section 28. In other words, the rolling bearing 57B is disposed on the impeller mounting section 28 side of the motor mounting section 30. The motor mounting section 30 and the impeller mounting section 28 are separated by the rolling bearing 57B. The interior of the motor mounting section 30 and the interior of the impeller mounting section 28 are spatially connected via the rolling bearing 57B.

[0043] The cooling flow path 31 is provided to spatially communicate the interior of the barrel 12 with the interior of the motor placement section 30 and to directly cool the superconducting motor 45 with liquefied gas. The cooling flow path 31 is composed of an inlet section 32 that indirectly communicates with the interior of the barrel 12 via the liquefied gas delivery path 25, an outlet section 33 that directly communicates with the interior of the barrel 12, and a bearing placement section 34.

[0044] The inlet section 32 is provided between the motor mounting section 30 and the impeller mounting section 28. The inlet section 32 opens to face the inside of the discharge section 28f of the impeller mounting section 28, and communicates with the inside of the barrel 12 via the impeller mounting section 28 and the suction section 26 of the liquefied gas delivery path 25. The inlet section 32 also communicates with the inside of the motor mounting section 30. This allows communication between the inside of the barrel 12 and the inside of the motor mounting section 30 via the inlet section 32, the impeller mounting section 28, and the suction section 26. More specifically, the inlet section 32 communicates with the discharge section 28f, which is downstream of the impeller mounting section 28 in the direction in which the liquefied gas is delivered. A balance piston 35, which will be described in detail later, is arranged in the inlet section 32.

[0045] The outflow portion 33 is provided on the upper side of the motor mounting portion 30, opposite the inflow portion 32. The outflow portion 33 is in communication with the motor mounting portion 30 via the bearing mounting portion 34. The outflow portion 33 opens on the outer peripheral surface of the casing 22 so as to face the inside of the barrel 12. More specifically, as shown in FIG. 3 , the outflow portion 33 includes a first portion 33a extending along the axis A and a second portion 33b extending in a direction intersecting (orthogonal to) the first portion 33a and facing the inside of the barrel 12. An orifice 39, which will be described in detail later, is provided at the outlet of the outflow portion 33.

[0046] 2 , the bearing arrangement section 34 is a space for arranging a magnetic bearing 55. The bearing arrangement section 34 is provided between the motor arrangement section 30 and the outlet section 33 and extends along the axis A. In other words, the bearing arrangement section 34 is provided between the inlet section 32 and the outlet section 33, on the opposite side of the motor arrangement section 30 from the impeller arrangement section 28. The bearing arrangement section 34 is in communication with both the motor arrangement section 30 and the outlet section 33. The magnetic bearing arranged in the bearing arrangement section 34 is not limited to the magnetic bearing 55 that can support the motor shaft 49 in the axial direction. As long as an axial bearing is arranged in a portion other than the bearing arrangement section 34, it may be configured to support the motor shaft 49 in the radial direction.

[0047] A rolling bearing 57A is disposed between the bearing arrangement section 34 and the motor arrangement section 30. In other words, the rolling bearing 57A is disposed on the bearing arrangement section 34 side of the motor arrangement section 30. The bearing arrangement section 34 and the motor arrangement section 30 are separated by the rolling bearing 57A. The interior of the bearing arrangement section 34 and the interior of the motor arrangement section 30 are spatially connected via the rolling bearing 57A.

[0048] The upper end of the bearing arrangement section 34 is provided with a recess 34a that is recessed upward and accommodates the upper end of the motor shaft 49. A touchdown bearing 56 is disposed within the recess 34a, as well as a distance measurement sensor 61 that detects the upper end of the motor shaft 49. However, the distance measurement sensor 61 may be provided in the magnetic bearing 55 itself.

[0049] The balance piston 35 is disposed within the inlet section 31 and serves as a balancing device that adjusts the amount of liquefied gas flowing into the cooling passage 31, including the motor placement section 30, and reduces axial thrust by reducing pressure. The balance piston 35 includes a fixed seat 36 and a rotor 37. The gap and shape between the fixed seat 36 and the rotor 37 are set so that the difference (pressure difference) between the internal pressure of the discharge section 28f of the liquefied gas delivery passage 25, more specifically, the discharge pressure of the impeller 52, and the internal pressure of the cooling passage 31, including the motor placement section 30, is within an appropriate range. The balance piston 35 also functions as a pressure reducing element on the low-pressure side. In this embodiment, a single balance piston is used as the balance piston 35. However, a double balance piston may be used in place of the balance piston 35 in the balancing device.

[0050] The fixed seat 36 is cylindrical with its center aligned with the axis A, and is attached to the inner periphery of the inlet section 32. The internal space defined by the inner periphery of the fixed seat 36 functions as a communication hole that connects the interior of the impeller mounting section 28 with the interior of the motor mounting section 30. The lower end of the communication hole opens to face the discharge portion 28f of the impeller mounting section 28, and the upper end of the communication hole opens to face the motor mounting section 30.

[0051] The rotor 37 is cylindrical, attached so as to be immovable relative to the motor shaft 49 in both the circumferential and axial directions, and disposed within the internal space of the fixed seat 36. The rotor 37 is movable integrally with the motor shaft 49 along the axis A due to the pressure difference between the liquefied gas delivery path 25 and the cooling flow path 31 including the motor mounting portion 30.

[0052] The balance piston 35 limits the amount of liquefied gas that flows from the discharge portion 28f of the liquefied gas delivery passage 25 into the cooling passage 31, and allows the liquefied gas to flow from the liquefied gas delivery passage 25 into the cooling passage 31 by using the gap (i.e., the opening area) between the inner circumferential surface of the fixed seat 36 and the outer circumferential surface of the rotor 37. A load that supports the rotor 37 is generated by the pressure difference between the upstream and downstream sides of the balance piston 35. Moreover, excessive movement of the rotor 37 in the direction along the axis A is regulated by the control of the magnetic bearing 55 by the control unit 60 based on the detection result of the distance measurement sensor 61, as described above.

[0053] 2 and 3 , the orifice 39 is disposed at the outlet of the outflow section 33 and maintains the pressure in the cooling passage 31, including the motor mounting section 30, higher than the pressure in the barrel 12. More specifically, the outlet of the outflow section 33 is threaded, and a bolt 40 having a through hole is threaded into the thread. The through hole of the bolt 40 is smaller than the inner diameter of the second portion 33b of the outflow section 33, forming the orifice 39, which is a type of pressure reducing device. However, the pressure reducing device is not limited to the orifice 39 having a uniform cross-sectional shape. It may also be a venturi shape whose cross-sectional shape gradually decreases from the upstream side to the downstream side in the flow direction, an open / close valve, or a labyrinth. Furthermore, the pressure reducing device may be a multi-stage orifice in which multiple orifices are arranged in series at intervals. Using a multi-stage orifice as the pressure reducing device reliably maintains the pressure in the cooling passage 31 higher than the pressure in the barrel 12.

[0054] In the cooling flow path 31 configured in this manner, when the liquefied gas in the barrel 12 is delivered through the liquefied gas delivery path 25 by rotation of the impeller 52 by the superconducting motor 45, a portion of the delivered liquefied gas flows into the inlet portion 32 via the balance piston 35 due to the discharge pressure of the impeller 52. The inflowing liquefied gas then flows out (recirculates) into the barrel 12 via the rolling bearing 57B, the motor mounting portion 30, the rolling bearing 57A, the bearing mounting portion 34, and the outlet portion 33. This ensures that the superconducting motor 45, the magnetic bearing 55, and the rolling bearing 57 are cooled by heat exchange. Furthermore, the orifice 39 prevents the liquefied gas from flowing into the barrel 12. This increases the pressure inside the cooling flow path 31, including the motor mounting portion 30, and prevents the liquefied gas from vaporizing.

[0055] In the pump 10 configured as described above, the barrel 12 is filled with liquefied gas. Therefore, if a normal conduction motor is used as a drive source for pumping the liquefied gas, it is difficult to start the motor because it is difficult to rotate due to the difficulty in linking magnetic flux and generating induced electromotive force. In addition, the generated heat loss may cause the liquefied gas to heat up and gasify, which reduces the efficiency of pumping the liquefied gas.

[0056] On the other hand, in order to pressurize liquefied gas to a pressure similar to that of water, it is necessary to increase the number of stages of the closed impeller 53 constituting the impeller 52, lower the specific speed, or increase the rotation speed. However, increasing the number of stages of the impeller 52 increases the length of the motor shaft 49, which may lead to concerns about increased costs and increased vibration. Furthermore, a lower specific speed may lead to concerns about reduced efficiency and boil-off gas (BOG). Furthermore, a higher rotation speed may lead to concerns about increased vibration and resonance.

[0057] In contrast, the pump 10 of this embodiment employs a superconducting motor 45 as its drive source. The superconducting motor 45 can operate normally because the electrical resistance of the superconducting wire becomes zero when cooled to a low temperature, reducing loss. The superconducting motor 45 can also rotate at higher speeds than a normal conducting motor, eliminating the need to increase the number of stages in the impeller 52, enabling a high output density and enabling the motor to be made more compact. This allows for highly efficient pumping of liquefied gas while minimizing overall size and suppressing BOG. ​​Furthermore, a magnetic bearing 55 is used as one of the multiple bearings. This allows for vibration control and reduced maintenance costs.

[0058] More specifically, the liquefied gas booster pump 10 of this embodiment has the following features.

[0059] A superconducting motor 45, which is more efficient than a normal conducting motor, is used as the drive source. This allows for highly efficient pumping of liquefied gas. It also prevents the liquefied gas from evaporating due to heat loss. Furthermore, the axial length of the motor shaft 49 can be shortened compared to when two pump units using normal conducting motors are arranged, allowing for a more compact overall system. Furthermore, the barrel 12 is filled with liquefied gas, and the casing 22 containing the superconducting motor 45 is submerged in the liquid, so the superconducting motor 45 can be maintained in a superconducting state.

[0060] The casing 22 has a cooling passage 31 formed therein, which spatially connects the interior of the barrel 12 with the interior of the motor placement section 30 and cools the superconducting motor 45 with liquefied gas. Therefore, the superconducting motor 45 can be reliably maintained in a superconducting state by direct cooling with the liquefied gas.

[0061] The cooling flow path 31 has an inlet portion 32 that communicates with the discharge portion 28f of the impeller arrangement portion 28. This allows the liquefied gas to be supplied to the cooling flow path 31 by the discharge pressure of the impeller 52. Therefore, the superconducting motor 45 can be reliably cooled by the liquefied gas.

[0062] The bearing arrangement section 34 is provided on the opposite side of the motor arrangement section 30 from the impeller arrangement section 28, and is connected to both the motor arrangement section 30 and the outlet section 33. A magnetic bearing 55 that supports the motor shaft 49 is disposed in this bearing arrangement section 34. Therefore, the magnetic bearing 55, which becomes heated by the rotation of the motor shaft 49, can be cooled by the liquefied gas.

[0063] Because magnetic bearings 55 and rolling bearings 57 are used as bearings to support motor shaft 49, cost increases can be minimized, and motor shaft 49 can be rotated at high speed and with low vibration. Furthermore, loss due to sliding contact, i.e., wear and heat generation, can be reduced, which suppresses evaporation of liquefied gas and enables highly efficient delivery of liquefied gas. Furthermore, by arranging multiple rolling bearings 57A to 57C, the distance between the motor shaft 49 support members can be shortened, thereby increasing shaft rigidity, raising the resonance frequency, and suppressing resonance.

[0064] By using a superconducting magnetic bearing as the magnetic bearing 55, a powerful repulsive levitation force can be achieved by the pinning effect of the magnetic flux, which enables non-contact support on the motor shaft 49 in an uncontrolled state, thereby realizing a configuration that can minimize bearing loss.

[0065] The outflow portion 33 is provided with an orifice 39 for making the pressure inside the cooling flow path 31 higher than the pressure inside the barrel 12. This makes it possible to suppress evaporation of the liquefied gas inside the cooling flow path 31. Furthermore, by configuring the restriction as a multi-stage orifice made up of multiple orifices 39, it is possible to reliably maintain a higher pressure inside the cooling flow path 31 than inside the barrel 12.

[0066] A balance piston 35 is disposed in the inflow section 32 that constitutes the cooling flow path 31. This makes it possible to adjust the amount of liquefied gas that flows from the discharge section 28f of the liquefied gas delivery path 25 into the cooling flow path 31 by the differential pressure between them. Furthermore, the balance piston 35 can apply an axial load from the upstream high-pressure side to the downstream low-pressure side, and this axial load is generated in the opposite direction to the axial load caused by hydraulic force, thereby reducing the axial load of the pump.

[0067] The impeller 52 is configured as a multi-stage impeller in which a plurality of closed impellers 53 are arranged in series, so that the liquid can be pressurized to a pressure similar to that of water and sent out with high efficiency.

[0068] Other embodiments and various modifications of the present invention will be described below, but in these descriptions, points that are not particularly mentioned are the same as those in the first embodiment.

[0069] In the pump 10 of the first embodiment shown in Fig. 2, the superconducting motor 45 is disposed downstream of the impeller 52 in the direction of delivery of the liquefied gas through the liquefied gas delivery path 25, whereas in the pumps 10 of the second to fourth embodiments shown in Figs. 4 to 6, the superconducting motor 45 is disposed upstream of the impeller 52. This allows the superconducting motor 45 to be cooled by the liquefied gas immediately after it flows into the casing 22. Furthermore, the superconducting motor 45 and the magnetic bearing 55 can be cooled by different cooling flow paths 31, 68. The configurations of the pumps 10 of the second to fourth embodiments will be described below in order.

[0070] 4 , in a pump 10 according to a second embodiment, the superconducting pump 10, the impeller 52, and the magnetic bearing 55 are arranged in this order from bottom to top along the axis A. Rolling bearings 57 are arranged above and below the superconducting motor 45. An inducer 58 is arranged in the liquid delivery path 25 upstream of the impeller 52, and an axial impeller 65 is further arranged between the inducer 58 and the motor body 46 of the superconducting motor 45.

[0071] The superconducting motor 45 is arranged so that a main portion 49a of the motor shaft 49 projects upward from the motor body 46, and a sub-portion 49b of the motor shaft 49 projects downward from the motor body 46. The tip end of the main portion 49a of the motor shaft 49 is supported by a magnetic bearing 55, and the base end is supported by a rolling bearing 57. The sub-portion 49b of the motor shaft 49 is supported by one rolling bearing 57.

[0072] The axial flow impeller 65 is attached so as to be immovable relative to the main portion 49a of the motor shaft 49. The axial flow impeller 65 rotates integrally with the motor shaft 49, and causes the liquefied gas to flow from the bottom to the top along the axis A. However, instead of the axial flow impeller 65, a centrifugal impeller or a mixed flow impeller may be used, and the type of impeller can be changed as necessary.

[0073] The casing 22 is provided with a liquefied gas delivery path 25 and a motor placement section 30. The casing 22 of this embodiment is also provided with a cooling flow path (first cooling flow path) 31 for cooling the superconducting motor 45 and a cooling flow path (second cooling flow path) 68 for cooling the magnetic bearing 55.

[0074] As in the first embodiment, the liquefied gas delivery passage 25 includes a suction section 26, a discharge section 27, and an impeller mounting section 28. The suction section 26 is located between the inducer 58 and the axial impeller 65 at the center of the overall height of the casing 22. The suction port 26a of the suction section 26 is spaced apart from the inner side of the outer peripheral wall 13 of the barrel 12 and opens to face the interior of the barrel 12. The suction section 26 extends radially inward from the suction port 26a located on the outer peripheral surface of the casing 22. However, the suction section 26 may be formed by a plurality of through-holes that radially penetrate the casing 22, or ribs may be provided within the suction section 26. The discharge section 27 is connected to the outer peripheral portion of the discharge portion 28f of the impeller mounting section 28 and extends upward, bypassing the cooling flow path 68. The impeller mounting portion 28 extends along the axis A and communicates with the inner end of the suction portion 26 including the suction port 26a and the lower end of the discharge portion 27 including the discharge port 27a.

[0075] The motor mounting section 30 is provided below the suction section 26 of the liquefied gas delivery passage 25 and extends along the axis A. In other words, the motor mounting section 30 is provided adjacent to the suction port 26a of the impeller mounting section 28. Rolling bearings 57 are provided above and below the motor mounting section 30.

[0076] The cooling flow path 31 is composed of an inlet section (first inlet section) 32 that is directly connected to the inside of the barrel 12, an outlet section (first outlet section) 33 that is connected to the suction section 26 of the liquefied gas discharge path 25, and an axial flow impeller arrangement section 66.

[0077] The inlet section 32 is provided on the lower side of the motor mounting section 30, opposite the liquefied gas delivery path 25, and opens on the outer peripheral surface of the casing 22 so as to face the inside of the barrel 12. The inlet section 32 extends radially inward from the outer peripheral surface of the casing 22, and is provided on its inner side with an expanded section 32a having a circular cross section centered on the axis A. A rolling bearing 57 is disposed between the inlet section 32 and the motor mounting section 30. The inlet section 32 and the motor mounting section 30 are separated by the rolling bearing 57. The inlet section 32 and the motor mounting section 30 are spatially connected via the rolling bearing 57. However, the inlet section 32 may be constituted by a plurality of through holes that penetrate the casing 22 in the radial direction, or ribs may be provided inside the inlet section 32.

[0078] The outflow portion 33 is provided between the suction portion 26 of the liquefied gas delivery passage 25 and the axial flow impeller arrangement portion 66. The outflow portion 33 opens to face the inside of the suction portion 26 and communicates with the upstream side of the impeller arrangement portion 28 in the direction in which the liquefied gas is delivered. The outflow portion 33 also communicates with the inside of the motor arrangement portion 30 via the axial flow impeller arrangement portion 66. However, the outflow portion 33 may be configured to communicate with the portion in which the inducer 58 is arranged. The outflow portion 33 may also be configured to communicate with the upstream side of the impeller arrangement portion 28, which is downstream of the inducer 58.

[0079] The axial impeller mounting section 66 is a space for mounting the axial impeller 65, and is connected to the outflow section 33 and the motor mounting section 30. A rolling bearing 57 is disposed between the axial impeller mounting section 66 and the motor mounting section 30. The axial impeller mounting section 66 and the motor mounting section 30 are separated by the rolling bearing 57. The interior of the axial impeller mounting section 66 and the interior of the motor mounting section 30 are spatially connected via the rolling bearing 57.

[0080] In the cooling flow path 31 configured in this manner, the rotation of the impeller 52 and the inducer 58 by the superconducting motor 45, which in turn generates an attractive force on the liquefied gas delivered through the liquefied gas delivery path 25, causing the liquefied gas in the barrel 12 to flow in from the inlet portion 32. The liquefied gas then flows through the motor arrangement portion 30 and the axial impeller arrangement portion 66 and out from the outlet portion 33 into the liquefied gas delivery path 25. The rotation of the axial impeller 65 by the superconducting motor 45 also promotes the flow of the liquefied gas toward the liquefied gas delivery path 25 via the inlet portion 32, the motor arrangement portion 30, the axial impeller arrangement portion 66, and the outlet portion 33 in this order.

[0081] As a result, the superconducting motor 45 is cooled highly efficiently by heat exchange with the unheated liquefied gas that flows in from inside the barrel 12. The liquefied gas that has been heated by cooling the superconducting motor 45 is delivered into the liquefied gas delivery path 25 and delivered to the outside of the barrel 12 in a mixed state with the unheated liquefied gas that has flowed directly into the liquefied gas delivery path 25 from inside the barrel 12. Therefore, evaporation of the liquefied gas due to a temperature rise can be suppressed, and the temperature rise of the liquefied gas in the barrel 12 can also be suppressed.

[0082] However, the direction of delivery of the liquefied gas by the axial flow impeller 65 may be toward (below) the motor body 47, and a portion of the liquefied gas sucked through the suction portion 26 may be supplied to the motor body 47. In this case, the outlet portion 33 in Figure 4 constitutes the inlet portion, and the inlet portion 32 in Figure 4 constitutes the outlet portion.

[0083] The bearing arrangement section 34 in which the magnetic bearing 55 is disposed is provided in the casing 22 between the upper and lower ends of the discharge section 27, and extends along the axis A. In other words, the bearing arrangement section 34 is provided adjacent to the upper side of the impeller arrangement section 28, opposite the motor arrangement section 30, i.e., on the discharge port 27a side. The magnetic bearing 55 and a distance measurement sensor 61 are disposed within the bearing arrangement section 34.

[0084] The cooling flow path 68 is provided to spatially communicate the interior of the barrel 12 with the interior of the bearing arrangement portion 34 and to cool the magnetic bearing 55 with liquefied gas. The cooling flow path 68 is composed of an inlet portion (second inlet portion) 69 that indirectly communicates with the interior of the barrel 12 via the liquefied gas delivery path 25, and an outlet portion (second outlet portion) 70 that directly communicates with the interior of the barrel 12.

[0085] The inlet portion 69 is provided between the impeller arrangement portion 28 and the bearing arrangement portion 34. The inlet portion 69 opens to face the inside of the discharge portion 28f of the impeller arrangement portion 28 and communicates with the inside of the barrel 12 via the liquefied gas delivery path 25. The inlet portion 69 also communicates with the inside of the bearing arrangement portion 34. This allows the inside of the barrel 12 to communicate with the inside of the bearing arrangement portion 34 via the inlet portion 69, the impeller arrangement portion 28, and the suction portion 26. More specifically, the inlet portion 69 communicates with the downstream side of the impeller arrangement portion 28 in the direction in which the liquefied gas is delivered. This allows the liquefied gas to be supplied to the cooling flow path 68, including the impeller arrangement portion 28, by the discharge pressure of the impeller 52. A balance piston 35 is disposed in the inlet portion 69. The balance piston 35 adjusts the amount of liquefied gas flowing into the cooling flow path 68, including the impeller arrangement portion 28.

[0086] The outlet portion 70 is provided on the upper side of the bearing arrangement portion 34, opposite the inlet portion 69, and is in communication with the bearing arrangement portion 34. The outlet portion 70 opens on the outer peripheral surface of the casing 22 so as to face the inside of the barrel 12. More specifically, the outlet portion 70 includes a first portion extending along the axis A and a second portion extending in a direction intersecting the first portion and facing the inside of the barrel 12. An orifice 39 similar to that of the first embodiment shown in FIG. 3 is disposed at the outlet portion of the outlet portion 70. The orifice 39 maintains a higher pressure inside the cooling flow passage 68, including the impeller arrangement portion 28, than inside the barrel 12.

[0087] In the cooling flow path 68 configured in this manner, when the liquefied gas in the barrel 12 is delivered through the liquefied gas delivery path 25 by rotation of the impeller 52 by the superconducting motor 45, a portion of the delivered liquefied gas flows into the inlet portion 69 via the balance piston 35 due to the discharge pressure of the impeller 52. The inflowing liquefied gas then flows out into the barrel 12 via the bearing arrangement portion 34 and the outlet portion 70. This ensures that the magnetic bearing 55 is cooled. Furthermore, the outflow of liquefied gas into the barrel 12 is suppressed by the orifice 39. This ensures that the pressure in the cooling flow path 68, including the bearing arrangement portion 34, is increased.

[0088] Third Embodiment Referring to Fig. 5, the pump 10 of the third embodiment differs from the pump 10 of the second embodiment shown in Fig. 4 in that the configuration of the cooling flow path (first cooling flow path) 31 is changed. The cooling flow path 31 of the pump 10 of the third embodiment does not use the axial flow impeller 65 including the axial flow impeller arrangement portion 66 shown in Fig. 4. In Fig. 5, the same elements as those of the second embodiment shown in Fig. 4 are denoted by the same reference numerals.

[0089] The cooling flow path 31 is made up of a plurality of through holes that penetrate in the radial direction. Each through hole has an outer end that opens to face the inside of the barrel 12 and an inner end that opens to face the inside of the motor mounting section 30. Of the plurality of through holes configured in this manner, some form inlet sections (first inlet sections) 32, and the rest form outlet sections (first outlet sections) 33.

[0090] In the cooling flow path 31 configured in this manner, the liquefied gas flows into and out of the motor mounting portion 30 due to the temperature difference between the barrel 12 and the motor mounting portion 30 and the rotational force of the rotor 48. As a result, the superconducting motor 45 is cooled highly efficiently because heat is exchanged with the unheated liquefied gas flowing in from the barrel 12. Furthermore, the liquefied gas heated by cooling the superconducting motor 45 is returned to the barrel 12 and mixed with the unheated liquefied gas, thereby suppressing evaporation due to an increase in temperature. Note that because the flow of liquefied gas into and out of the motor mounting portion 30 is due to the temperature difference and the rotational force of the rotor 48, the liquefied gas rarely flows between the motor mounting portion 30 and the liquefied gas delivery path 25 via the rolling bearing 57. However, a circulation impeller may be disposed in the motor mounting portion 30 to ensure a sufficient circulation amount of liquefied gas.

[0091] 6, a pump 10 of a fourth embodiment differs from the pumps 10 of the other embodiments described above in that it includes a first impeller 52A and a second impeller 52B spaced apart along the axis A, with a superconducting motor 45 disposed between them, and in that the configurations of the liquefied gas delivery path 25 and the cooling flow path (first cooling flow path) 31 have been changed. In FIG. 6, the same elements as those of the other embodiments are denoted by the same reference numerals.

[0092] The first impeller 52A and the second impeller 52B are both configured as multi-stage impellers. The first impeller 52A is disposed below the superconducting motor 45, and the second impeller 52B is disposed above the superconducting motor 45. The number of closed impellers 53 configuring the first impeller 52A is smaller than the number of closed impellers 53 configuring the second impeller 52B. In this embodiment, the number of closed impellers 53 configuring the first impeller 52A is two, and the number of closed impellers 53 configuring the second impeller 52B is four. However, the number of closed impellers 53 configuring the first impeller 52A and the second impeller 52B can both be changed as necessary.

[0093] The liquefied gas discharge path 25 includes an intake section 26, a discharge section 27, a first impeller arrangement section (first arrangement section) 28A, a second impeller arrangement section (second arrangement section) 28B, and a communication section 72, and extends from the lower end to the upper end of the casing 22.

[0094] The suction section 26 is provided at the lower end of the casing 22 and is connected to the center of the lower end of the lower first impeller mounting section 28A, as in the first embodiment shown in Fig. 2. A rolling bearing 57 and an inducer 58 are disposed within the suction section 26. The discharge section 27 is connected to the outer periphery of the discharge portion 28f of the upper second impeller mounting section 28B, and extends upward, bypassing the cooling flow path (second cooling flow path) 68, as in the second embodiment shown in Fig. 4.

[0095] The first impeller mounting section 28A is provided for mounting the first impeller 52A. The first impeller mounting section 28A communicates with the upper end of the suction section 26 including the suction port 26a, and extends along the axis A. The first impeller mounting section 28A is provided with a partition wall 28a that separates adjacent closed impellers 53 of the first impeller 52A.

[0096] The second impeller mounting portion 28B is provided for mounting the second impeller 52B. The second impeller mounting portion 28B is provided at a distance from the first impeller mounting portion 28A along the axis A. The second impeller mounting portion 28B communicates with the lower end of the discharge portion 27 including the discharge port 27a, and extends along the axis A. The second impeller mounting portion 28B is provided with a partition wall 28a that separates adjacent closed impellers 53 of the second impeller 52B.

[0097] A bearing arrangement portion 34 is provided adjacent to each of the impeller arrangement portions 28A, 28B on the discharge port 27a side. In other words, the bearing arrangement portion 34 is provided adjacent to the second impeller arrangement portion 28B on the opposite side from the motor arrangement portion 30. An inlet portion 69 of a cooling flow path 68 communicating with the bearing arrangement portion 34 is connected to the downstream side (discharge portion 28f) of the second impeller arrangement portion 28B in the direction in which the liquefied gas is discharged. The second impeller arrangement portion 28B and the cooling flow path 68 including the bearing arrangement portion 34 are connected via a balance piston 35.

[0098] The communication portion 72 is connected to the upper end of the first impeller mounting portion 28 A and the lower end of the second impeller mounting portion 28 B. The communication portion 72 extends in the vertical direction, bypassing the motor mounting portion 30 .

[0099] By configuring the liquefied gas discharge path 25 in this manner, the liquefied gas in the barrel 12 is sucked in through the suction port 26a by the rotation of the impellers 52A and 52B by the superconducting motor 45, and passes through the suction section 26, the first impeller arrangement section 28A and the communication section 72, the second impeller arrangement section 28B, and the discharge section 27 in that order, before being discharged from the discharge port 27a.

[0100] The motor mounting section 30 is provided in the casing 22 between the first impeller mounting section 28A and the second impeller mounting section 28B, and extends along the axis A. In other words, the motor mounting section 30 is provided adjacent to the lower side of the second impeller mounting section 28B, which is closer to the suction port 26a. Rolling bearings 57 are provided between the motor mounting section 30 and the first impeller mounting section 28A, and between the motor mounting section 30 and the second impeller mounting section 28B. The motor mounting section 30 and the first impeller mounting section 28A, and the motor mounting section 30 and the second impeller mounting section 28B are spatially connected via the rolling bearings 57.

[0101] The cooling flow path 31 is composed of an inlet section (first inlet section) 32 that is indirectly connected to the suction section 26 of the liquefied gas discharge path 25 and the inside of the barrel 12 via the first impeller arrangement section 28A, and an outlet section (first outlet section) 33 that is connected to the communication section 72 of the liquefied gas discharge path 25.

[0102] The inlet section 32 is provided between the first impeller mounting section 28A and the motor mounting section 30. The inlet section 32 opens to face the inside of the discharge section 28f of the first impeller mounting section 28A and is connected to the inside of the barrel 12 via the first impeller mounting section 28A of the liquefied gas delivery path 25 and the suction section 26. The inlet section 32 also communicates with the inside of the motor mounting section 30. This allows communication between the inside of the barrel 12 and the inside of the motor mounting section 30 via the inlet section 32, the impeller mounting section 28A, and the suction section 26. More specifically, the inlet section 32 communicates with the discharge section 28f, which is downstream of the first impeller mounting section 28A in the direction in which the liquefied gas is delivered. A rolling bearing 57 is disposed in the inlet section 32. The inside of the motor mounting section 30 and the inside of the first impeller mounting section 28A are spatially connected via the rolling bearing 57. The liquefied gas can be supplied to the cooling flow passage 31 by the discharge pressure of the first impeller 52A.

[0103] The outflow section 33 is provided between the second impeller arrangement section 28B and the motor arrangement section 30 of the liquefied gas delivery passage 25. The outflow section 33 opens to face the inside of the second impeller arrangement section 28B, and communicates with the upstream side of the second impeller arrangement section 28B in the direction in which the liquefied gas is delivered. A rolling bearing 57 is arranged in the outflow section 33, and the inside of the motor arrangement section 30 and the second impeller arrangement section 28B are spatially communicated with each other via the rolling bearing 57.

[0104] In the cooling flow path 31 configured as described above, when the liquefied gas in the barrel 12 is delivered through the liquefied gas delivery path 25 by the rotation of the impellers 52A, 52B and the inducer 58 caused by the superconducting motor 45, the discharge pressure of the first impeller 52A and the attractive force of the second impeller 52B cause the liquefied gas to flow from the inlet 32 ​​into the motor mounting section 30. This ensures reliable cooling of the superconducting motor 45 and the pair of rolling bearings 57. Furthermore, the internal pressure of the motor mounting section 30 can be maintained high. Furthermore, the liquefied gas heated by cooling the superconducting motor 45 returns from the outlet 33 into the liquefied gas delivery path 25 (second impeller mounting section 28B) and is mixed with unheated liquefied gas before being delivered. This prevents the liquefied gas from vaporizing due to a temperature rise, and also prevents the liquefied gas in the barrel 12 from heating up.

[0105] In the pump 10 of the second to fourth embodiments configured as described above, the liquefied gas in the barrel 12 can be pressurized and delivered from the delivery port 17a with high efficiency, as in the first embodiment. Moreover, since the superconducting motor 45 is used, the overall size of the pump 10 can be suppressed.

[0106] 7, a pump 10 according to a fifth embodiment differs from the pump 10 according to the first embodiment in that an impeller 52 is attached to a rotary shaft 74, and the rotary shaft 74 is connected to a motor shaft 49 by a coupling 75. However, the configuration in which the rotary shaft 74 is attached to the motor shaft 49 by a coupling 75 can also be applied to the pumps 10 according to the other embodiments.

[0107] The superconducting motor 45 has a motor shaft 49 whose main portion 49 a projects into a coupling arrangement portion 76 formed in the casing 22 and terminates within the coupling arrangement portion 76 .

[0108] The rotating shaft 74 extends downward along the axis A from within the coupling arrangement portion 76 of the casing 22 to the suction portion 26. The upper and lower ends of the rotating shaft 74 are rotatably supported by rolling bearings 57. The rotor 37 of the balance piston 35 and the impeller 52 are respectively attached to the rotating shaft 74 so as to be unable to move relative to each other in either the circumferential or axial direction.

[0109] The coupling 75 is disposed in a coupling arrangement portion 76 of the casing 22, and couples the ends of the motor shaft 49 and the rotating shaft 74 together so that they cannot rotate relative to each other. The coupling 75 may have any configuration as long as it can couple the motor shaft 49 and the rotating shaft 74 together. The coupling 75 may be, for example, a magnetic coupling, a rigid coupling, or a flexible coupling.

[0110] Similar to the first embodiment, the cooling flow path 31 provided in the casing 22 includes an inlet portion 32, an outlet portion 33, and a bearing arrangement portion 34. Furthermore, the cooling flow path 31 of the present embodiment includes a coupling arrangement portion 76 between the inlet portion 32 and the motor arrangement portion 30.

[0111] The coupling arrangement portion 76 is a space for arranging the coupling 75, and is provided between the inlet portion 32 and the motor arrangement portion 30. Rolling bearings 57 are respectively arranged between the coupling arrangement portion 76 and the inlet portion 32, and between the coupling arrangement portion 76 and the motor arrangement portion 30. The rolling bearings 57 separate the coupling arrangement portion 76 from the inlet portion 32 and the motor arrangement portion 30. The coupling arrangement portion 76 is also spatially connected to the inlet portion 32 and the motor arrangement portion 30 via the rolling bearings 57. This allows a portion of the liquefied gas delivered through the liquefied gas delivery path 25 to be supplied to the cooling flow path 31, including the motor arrangement portion 30, as in the first embodiment.

[0112] 8, a pump 10 according to a sixth embodiment differs from the pump 10 according to the first embodiment in that a balance disk 78 is used as a balancing device instead of the balance piston 35 shown in FIG. 2, and the pump 10 does not use the magnetic bearing 55. However, the configuration in which the balance disk 78 is used instead of the balance piston 35 can also be applied to the pumps 10 according to the other embodiments.

[0113] The balance disk 78 is disposed within the inlet portion 32 of the cooling flow passage 31 in the casing 22. The balance disk 78 includes a fixed disk 78a and a rotating disk 78b, and also functions as a pressure reducing element, similar to the balance piston 35 shown in FIG.

[0114] The fixed disk 78a is attached to the inlet portion 32 of the cooling flow path 31 in the casing 22. The rotating disk 78b is attached to the motor shaft 49 of the superconducting motor 45 so as to be immovable relative to the motor shaft 49 in both the circumferential and axial directions. A first gap extending axially along the motor shaft 49 and a second gap extending radially perpendicular to the motor shaft 49 are provided between the fixed disk 78a and the rotating disk 78b. These gaps form a flow path for passing liquefied gas. In other words, the balance disk 78 communicates the liquefied gas delivery path 25 with the cooling flow path 31 via the gap between the fixed disk 78a and the rotating disk 78b. As a result, as in the first embodiment, a portion of the liquefied gas delivered through the liquefied gas delivery path 25 can be supplied to the cooling flow path 31, including the motor mounting portion 30.

[0115] In the pump unit 20 using the balance disk 78, a load can be generated in the opposite direction (upward in FIG. 8 ) to the thrust (downward in FIG. 8 ) by the impeller 52 due to the difference between the discharge pressure on the liquefied gas delivery path 25 side and the back pressure on the cooling path 31 side. This makes it possible to balance the axial thrust of the motor shaft 49 of the superconducting motor 45. In other words, because the thrust by the impeller 52 can be canceled out, the magnetic bearing 55 for supporting the axial direction can be made unnecessary.

[0116] However, the location of the balance disk 78 is not limited to between the motor body 46 and the impeller 52 and can be changed as needed. For example, the balance disk 78 may be located at the tip of the secondary portion 49b of the motor shaft 49, i.e., downstream of the motor mounting section 30 in the cooling flow passage 31. This allows the interior of the motor mounting section 30 to be maintained at a high pressure equivalent to the pump discharge pressure. This allows the cooling flow passage 31, including the motor mounting section 30, to be maintained at a high pressure, effectively suppressing evaporation of the liquefied gas. Furthermore, because the liquefied gas heated by the heat generated by the balance disk 78 does not flow into the motor mounting section 30, the temperature within the motor mounting section 30 can be kept lower. This allows the motor body 46 to be effectively cooled.

[0117] 9, the pump 10 of the seventh embodiment differs from the pump 10 of the first embodiment in that balance holes 53a are provided in the plurality of closed impellers 53 that make up the impeller 52. However, the configuration in which balance holes 53a are provided in the closed impellers 53 is also applicable to the pumps 10 of the other embodiments. Note that while the present embodiment shows a configuration in which the balance piston 35 is not used, the balance piston 35 may be used as in the first embodiment, or the balance disk 78 may be used as in the sixth embodiment.

[0118] 10, the balance hole 53a is provided in the rear shroud 53c of the front shroud 53b and rear shroud 53c that constitute the closed impeller 53, and penetrates along the motor shaft 49. A plurality of balance holes 53a are provided at intervals around the motor shaft 49. Note that reference numeral 53d in FIG. 10 denotes a vane. A reduced pressure space 80 is secured between the rear shroud 53c and the partition wall 28a.

[0119] In the pump 10 configured as described above, due to the pressure difference between the suction side (lower side in FIG. 10 ) and discharge side (upper side in FIG. 10 ) of the closed impeller 53, a portion of the liquefied gas discharged from the closed impeller 53 tends to flow back upstream through the gap between the closed impeller 53 and the partition wall 28a. In contrast, in this embodiment, the closed impeller 53 is provided with a balance hole 53a, and a reduced-pressure space 80 is provided between the rear shroud 53c and the partition wall 28a. This reduces the pressure acting on the back surface of the closed impeller 53 (rear shroud 53c). This reduces the pressure difference between the suction side and the discharge side of the closed impeller 53, thereby reducing the axial thrust of the impeller 52. As a result, the pump 10 can be configured without using the balance piston 35 shown in FIG. 2. Furthermore, when the balance piston 35 or the balance disk 78 is used, the size and shape of the balance piston 35 can be simplified.

[0120] 11 , a pump 10 of an eighth embodiment differs from the pump 10 of the first embodiment in that a first impeller 52A and a second impeller 52B are arranged at a distance from each other along a motor shaft 49 so as to cancel out the axial thrust of the first impeller 52A and the second impeller 52B. However, the configuration in which the axial thrust is canceled out by the first impeller 52A and the second impeller 52B can also be applied to the pumps 10 of the other embodiments.

[0121] The first impeller 52A is disposed on the suction section 26 side of the liquefied gas delivery path 25, and the second impeller 52B is disposed between the first impeller 52A and the superconducting motor 45. The first impeller 52A and the second impeller 52B are configured as multi-stage impellers having the same number of closed impellers 53. Of the first impeller 52A, the suction side is disposed on the lower side, and the discharge side is disposed on the upper side. Of the second impeller 52B, the suction side is disposed on the upper side, and the discharge side is disposed on the lower side. In other words, the first impeller 52A and the second impeller 52B are disposed back-to-back, with their back surfaces (discharge sides) facing each other.

[0122] As in the fourth embodiment, the liquefied gas discharge path 25 has an intake section 26, a discharge section 27, a first impeller arrangement section (first arrangement section) 28A, a second impeller arrangement section (second arrangement section) 28B, and a communication section 72, and extends from the lower end to the upper end of the casing 22.

[0123] The suction section 26 is provided at the lower end of the casing 22 and is connected to the center of the lower end of the lower first impeller mounting section 28A. A rolling bearing 57 and an inducer 58 are disposed within the suction section 26. The discharge section 27 is connected to a discharge portion 28f, which is the outer periphery of the lower end of the upper second impeller mounting section 28B, and extends upward, bypassing the second impeller mounting section 28B and the cooling flow path 31.

[0124] The first impeller mounting section 28A is provided for mounting the first impeller 52A. The first impeller mounting section 28A communicates with the upper end of the suction section 26 including the suction port 26a, and extends along the axis A. The first impeller mounting section 28A is provided with a partition wall 28a that separates adjacent closed impellers 53 of the impeller 52A.

[0125] The second impeller mounting portion 28B is provided for mounting the second impeller 52B. The second impeller mounting portion 28B is provided at a distance from the first impeller mounting portion 28A along the axis A. The second impeller mounting portion 28B communicates with the lower end of the discharge portion 27 including the discharge port 27a, and extends along the axis A. The second impeller mounting portion 28B is provided with a partition wall 28a that separates adjacent closed impellers 53 of the impeller 52B.

[0126] The communication portion 72 is connected to the upper end (discharge portion 28f) of the first impeller mounting portion 28A and the upper end (suction portion) of the second impeller mounting portion 28B. The communication portion 72 extends in the vertical direction, bypassing the second impeller mounting portion 28B.

[0127] The cooling flow passage 31, which communicates with the motor arrangement section 30, communicates with the upper end of the communication section 72, that is, with the liquefied gas delivery passage 25, downstream of the first impeller arrangement section 28A and upstream of the second impeller arrangement section 28B. The balance piston 35 shown in Figure 2 and the balance disk 78 shown in Figure 8 are not disposed in the inlet section 32 of the cooling flow passage 31. A portion of the liquefied gas delivered through the liquefied gas delivery passage 25 can flow into the cooling flow passage 31 due to the discharge pressure of the first impeller 52A.

[0128] In the pump 10 configured in this manner, the axial thrust from the first impeller 52A acts downward in Fig. 11, and the axial thrust from the second impeller 52B acts upward in Fig. 11. Moreover, because the first impeller 52A and the second impeller 52B are configured using the same number of multi-stage impellers, the axial thrusts from these are also roughly the same. As a result, the axial thrusts acting on the motor shaft 49 can be canceled out, and the pump 10 can be configured without using the balance piston 35 shown in Fig. 2 or the balance disk 78 shown in Fig. 8.

[0129] 12, the pump 10 of the ninth embodiment differs from the pump 10 of the eighth embodiment in that the liquefied gas delivery path 25 has a liquefied gas suction portion 26A by the first impeller 52A and a liquefied gas suction portion 26B by the second impeller 52B, which are separate, and the communication portion 72 shown in Fig. 11 is eliminated. However, the configuration in which a pair of impellers 52A, 52B are used and corresponding suction portions 26A, 26B are provided is also applicable to the pumps 10 of the other embodiments.

[0130] The liquefied gas delivery passage 25 includes a pair of suction portions 26A and 26B, one discharge portion 27, and a pair of impeller mounting portions 28A and 28B.

[0131] The first suction section 26A is provided at the lower end of the casing 22, and is connected to the center of the lower end of the lower first impeller mounting section 28A. A rolling bearing 57 and an inducer 58 are disposed within the first suction section 26A.

[0132] The second suction section 26B is provided in the casing 22 between the upper second impeller mounting section 28B and the cooling flow path 31, and extends in a radial direction perpendicular to the axis A. The second suction section 26B is connected to the upper center of the second impeller mounting section 28B and is also connected to the cooling flow path 31. An inducer 58 is disposed within the second suction section 26B.

[0133] The discharge section 27 is connected to the discharge portions 28f of each of the pair of impeller mounting sections 28A, 28B. Specifically, the upper end on the discharge side of the first impeller mounting section 28A and the lower end on the discharge side of the second impeller mounting section 28B are connected to the common discharge portion 28f. The discharge section 27 is connected to the outer periphery of this discharge portion 28f and extends upward, bypassing the second impeller mounting section 28B and the cooling flow path 31.

[0134] The cooling flow passage 31, which communicates with the motor mounting section 30, is also connected to the upper second suction section 26B. The balance piston 35 shown in FIG. 2 and the balance disk 78 shown in FIG. 8 are not disposed in the inlet section 32 of the cooling flow passage 31. A portion of the liquefied gas sucked through the second suction section 26B can flow into the cooling flow passage 31. However, to ensure the amount of liquefied gas that flows into the cooling flow passage 31, an axial flow impeller may be disposed in the inlet section 32 or the motor mounting section 30.

[0135] In the pump 10 of the eighth embodiment shown in FIG. 11 and the ninth embodiment shown in FIG. 12, the first impeller 52A and the second impeller 52B may be configured in a face-to-face arrangement with their front faces (suction sides) facing each other.

[0136] 13 , the pump 10 of the tenth embodiment differs from the pump 10 of the first embodiment in that the closed impeller 53 located at the lower end, which is the suction side end (first stage) of the impeller 52, is a double-suction type that can suck liquefied gas from both sides in the axial direction. However, the configuration in which the closed impeller 53 at the suction side end is a double-suction type can also be applied to the pumps 10 of the other embodiments.

[0137] The impeller 52 is composed of multiple closed impellers 53A in the second and subsequent stages from the bottom, and one closed impeller 53B in the first stage only. The closed impeller 53A is a single-suction type with the suction side located on the bottom, while the closed impeller 53B is a double-suction type with suction sides located on the top and bottom.

[0138] The suction section 26 of the liquefied gas delivery passage 25 extends radially inward from a suction port 26a located on the outer circumferential surface of the casing 22 and communicates with the outer circumferential portion of the lower end of the impeller arrangement section 28 in which the closed impeller 53B is arranged.

[0139] The impeller arrangement section 28 includes a plurality of annular partition walls 28a that separate the plurality of closed impellers 53A. In addition, a partition wall 28b having a shape different from the other partition walls 28a is provided between the first-stage closed impeller 53B and the second-stage closed impeller 53A in the impeller arrangement section 28. The partition wall 28b defines an involute passage that connects the portion where the first-stage closed impeller 53B is arranged with the portion where the second-stage closed impeller 53A is arranged.

[0140] In the pump 10 configured as above, the first-stage closed impeller 53B is of a double-suction type, so the flow rate per vane can be halved, thereby reducing the required suction head of the impeller 52.

[0141] 14 , the pump 10 of the eleventh embodiment differs from the pump 10 of the first embodiment in that the suction section 26 of the liquefied gas delivery passage 25 is modified to include a tandem impeller 52 that can suck in liquefied gas using two closed impellers 53. However, the configuration in which the impellers 52 are tandem is also applicable to the pumps 10 of the other embodiments.

[0142] The impeller 52 is of a single suction type with the suction side disposed on the lower side and is composed of a plurality of closed impellers 53 .

[0143] The suction section 26 of the liquefied gas discharge passage 25 extends radially inward from the suction port 26a located on the outer peripheral surface of the casing 22 and is connected to the lower outer peripheral portion of the impeller arrangement section 28 in which the closed impeller 53 located at the lower end is arranged.

[0144] The impeller arrangement section 28 includes a plurality of annular partition walls 28a that separate the plurality of closed impellers 53 from the second stage onward. Furthermore, a partition wall 28c having a different shape from the other partition walls 28a is provided between the lowermost closed impeller 53 and the second-stage closed impeller 53 in the impeller arrangement section 28. Furthermore, a flow dividing wall 28d is provided in the portion where the lowermost closed impeller 53 is arranged, facing the suction port 26a. The flow dividing wall 28d divides the liquefied gas drawn in from the suction section 26 into the side of the lowermost closed impeller 53 and the side of the second-stage closed impeller 53. Furthermore, the portion where the lowermost closed impeller 53 is arranged and the portion where the second-stage closed impeller 53 is arranged are connected via a communication section 28e.

[0145] The pump 10 configured as above uses a tandem impeller 52 that can suck liquefied gas with two closed impellers 53, so that the flow rate per vane can be halved, as in the tenth embodiment, and as a result, the required suction head of the impeller 52 can be reduced.

[0146] 12th Embodiment Referring to Fig. 15, a pump 10 according to a twelfth embodiment differs from the pump 10 according to the first embodiment in that the axis of the motor shaft 49, which includes the axis A of the barrel 12, is arranged to extend horizontally. The configuration of the pump unit 20 is the same as that of the first embodiment. That is, the pump unit 20 is configured as a horizontal-shaft multistage diffuser pump. However, the configuration in which the pump unit 20 is a horizontal-shaft multistage diffuser pump is also applicable to the pumps 10 according to the other embodiments.

[0147] The barrel 12 includes a cylindrical outer peripheral wall 13, a first closing wall 14 closing one end of the outer peripheral wall 13, and a second closing wall 15 closing the other end of the outer peripheral wall 13. The outer peripheral wall 13 is provided with a cylindrical intake portion 16 that protrudes radially outward. The second closing wall 15 is provided with a cylindrical delivery portion 17 that protrudes outward along the axis A. The outer end opening of the intake portion 16 forms an intake port 16a, and the outer end opening of the delivery portion 17 forms a delivery port 17a.

[0148] A support portion 85 is provided between the outer peripheral wall 13 and the casing 22 of the motor unit 20. The support portion 85 supports the underside of the casing 22, which is joined in a cantilever structure. In this embodiment, a support portion 85 is provided at each end of the casing 22. However, the number of support portions 85 may be one, or may be three or more, and can be changed as needed, as long as the configuration is such that the motor unit 20 can be supported in a stable state.

[0149] 16 , a pump 10 of the 13th embodiment, like the pump 10 of the 12th embodiment, includes a horizontal pump unit 20 in which the axis of the motor shaft 49, which includes the axis A of the barrel 12, extends horizontally. This pump 10 differs from the pump 10 of the 12th embodiment in that one end of the outer peripheral wall 13 of the barrel 12 is liquid-tightly closed by a casing 22 of the pump unit 20. However, the configuration in which one end of the outer peripheral wall 13 of the barrel 12 is liquid-tightly closed by a casing 22 is also applicable to the pumps 10 of the other embodiments.

[0150] The barrel 12 includes a cylindrical outer peripheral wall 13 and a first closing wall 14 that closes one end of the outer peripheral wall 13. The barrel 12 does not include the second closing wall 15 shown in Fig. 15. An annular flange portion 13a that protrudes inward is provided on the end of the outer peripheral wall 13 opposite the first closing wall 14. The flange portion 13a is capable of abutting against the outer peripheral surface of the casing 22 and also functions as a support portion that supports the pump unit 20.

[0151] The pump unit 20 differs from the twelfth embodiment only in that a flange portion 22a is provided at the end of the casing 22 where the discharge port 27a is provided. The flange portion 22a protrudes radially outward from the end of the casing 22 and is joined to the flange portion 13a of the barrel 12 in a liquid-tight manner.

[0152] A support portion 85 is provided between the outer peripheral wall 13 of the barrel 12 and the casing 22 of the motor unit 20. The support portion 85 is formed of an annular plate and supports the end of the casing 22 on the suction port 26a side. The support portion 85 is provided with a plurality of fluid passage holes within a range that ensures the strength to support the pump unit 20. This makes it possible to fill the barrel 12 with liquefied gas. However, the support portion 85 can be modified as needed as long as it is capable of supporting the casing 22. For example, the support portion 85 may be configured with a cylindrical holding portion that surrounds the casing 22 and a plurality of ribs that protrude radially from the holding portion.

[0153] The pump 10 of the twelfth and thirteenth embodiments configured as described above can achieve the same functions and effects as the first embodiment.

[0154] 17 , the pump 10 of the 14th embodiment differs from the first embodiment in that the liquefied gas is returned from the cooling passage 31 to the impeller arrangement portion 28 instead of flowing out from the cooling passage 31 into the barrel 12. However, the configuration in which the liquefied gas is returned from the cooling passage 31 to the impeller arrangement portion 28 can also be applied to the other embodiments.

[0155] Specifically, in the pump 10 of the fourteenth embodiment, the impeller 52, the superconducting motor 45, and the magnetic bearing 55 are arranged in this order from bottom to top along the axis A.

[0156] The cooling flow path 31 is composed of an inlet section 32, an outlet section 33, and a bearing arrangement section 34. The inlet section 32 communicates with the discharge portion 28f of the impeller arrangement section 28, and indirectly connects the motor arrangement section 30 to the inside of the barrel 12 via the liquefied gas delivery path 25. The outlet section 33 communicates with the bearing arrangement section 34 and opens to the inside of the barrel 12, and indirectly connects the motor arrangement section 30 to the inside of the barrel 12 via the bearing arrangement section 34.

[0157] A return pipe 87, which is an example of a return flow path, is connected to the outlet of the outflow section 33 to which the orifice 39 is attached. The return pipe 87 extends downward within the barrel 12 and is connected to the lower part of the impeller mounting section 28, more specifically, to a portion of the impeller 52 that is located radially outward of the lowest closed impeller 53. The return pipe 87, which is arranged in this manner, connects the motor mounting section 30 and the impeller mounting section 28. This makes it possible to increase the pressure at the outlet portion of the cooling flow path 31 in which the orifice 39 is disposed, compared to when liquefied gas is returned into the barrel 12 through the orifice 39. This makes it possible to maintain a higher pressure within the motor mounting section 30.

[0158] However, the return pipe 87 may be connected to a portion of the impeller mounting section 28 other than the lowest closed impeller 53. Furthermore, it is preferable that the closed impeller 53 located at the connection portion of the return pipe 87 adjusts the pressure in the cooling flow passage 31 including the motor mounting section 30 to an appropriate value by adjusting the diameter. Furthermore, the return passage is not limited to a configuration using a return pipe 87 separate from the casing 22, and may be configured to be provided in the casing 22, like the discharge section 27 of the liquefied gas delivery passage 25.

[0159] As with the first embodiment, this pump 10 can efficiently deliver liquefied gas while minimizing the overall size of the pump 10. Furthermore, since the pressure at the outlet of the cooling flow path 31 where the orifice 39 is disposed is high, evaporation of the liquefied gas within the cooling flow path 31 can be effectively suppressed.

[0160] 18 , the pump 10 of the 15th embodiment differs from the third embodiment in that it is provided with a liquid supply pipe (liquid supply path) 88 for supplying liquefied gas from the impeller mounting portion 28 to the motor mounting portion 30, and a return pipe (return path) 87 for returning liquefied gas from the motor mounting portion 30 to the impeller mounting portion 28. However, the configuration in which the liquid supply pipe 88 and the return pipe 87 are provided can also be applied to the other embodiments.

[0161] Specifically, in the pump 10 of the fifteenth embodiment, the superconducting motor 45, the impeller 52, and the magnetic bearings 55 are arranged in this order from bottom to top along the axis A. The impeller arrangement section 28 in which the impeller 52 is arranged has a plurality of partition walls 28a that individually partition the closed impellers 53 that make up the impeller 52. The motor arrangement section 30 that houses the motor body 46 of the superconducting motor 45 has an inlet section (first inlet section) 32 and an outlet section (first outlet section) 33, each of which has an outer end that opens to face the interior of the barrel 12 and an inner end that opens to face the interior of the motor arrangement section 30. The outlet section 33 is provided with an orifice 39 shown in FIG. 3 .

[0162] A liquid supply pipe 88, which is an example of a liquid supply path, is connected to a portion of the impeller mounting section 28 where the second-lowest closed impeller 53 is disposed. The liquid supply pipe 88 extends downward within the barrel 12 and is connected to the inlet section 32 of the motor mounting section 30. However, the liquid supply pipe 88 may be connected to a portion of the impeller mounting section 28 other than the portion where the lower-end closed impeller 53 is disposed. Furthermore, the liquid supply path is not limited to a configuration in which the liquid supply pipe 88 is separate from the casing 22, and may be configured to be provided in the casing 22, like the discharge section 27 of the liquefied gas delivery path 25.

[0163] A reflux pipe 87, which is an example of a reflux path, is connected to the outlet portion 33 of the motor arrangement portion 30. The reflux pipe 87 extends upward within the barrel 12 and is connected to a portion of the impeller arrangement portion 28 where the lower closed impeller 53 is arranged. However, it is sufficient that the reflux pipe 87 is connected to a portion of the impeller arrangement portion 28 below (on the suction side of) the connecting portion of the liquid supply pipe 88. Furthermore, the reflux path is not limited to a configuration in which the reflux pipe 87 is separate from the casing 22, and may be configured to be provided in the casing 22, like the discharge portion 27 of the liquefied gas delivery path 25.

[0164] In the pump 10 configured in this manner, a portion of the liquefied gas being discharged is supplied from the impeller mounting section 28 to the motor mounting section 30 via the liquid supply pipe 88 as the impeller 52 is rotated by the superconducting motor 45. The liquefied gas that has cooled the motor main body 46 is then returned from the motor mounting section 30 to the impeller mounting section 28 via the return pipe 87. This flow of liquefied gas is ensured by the pressure difference at the connecting portion, because the liquid supply pipe 88 is connected to the discharge side of the return pipe 87 in the impeller mounting section 28.

[0165] As with the first embodiment, this pump 10 can deliver liquefied gas with high efficiency while minimizing the overall size of the pump 10. Furthermore, because a portion of the liquefied gas being delivered is forcibly supplied by the liquid supply pipe 88 to the motor mounting section 30, which has the orifice 39 in the outlet 33, the pressure within the motor mounting section 30 can be increased, effectively preventing the liquefied gas from vaporizing.

[0166] Furthermore, the liquefied gas in the motor mounting section 30 is returned to the impeller mounting section 28 rather than flowing out into the low-pressure barrel 12, thereby suppressing BOG. ​​However, if there is no concern about BOG, the liquefied gas in the motor mounting section 30 may be allowed to flow into the barrel 12 without providing the return pipe 87. Furthermore, if the return pipe 87 is not used, the liquid supply pipe 88 may be connected to a portion of the impeller mounting section 28 where the lower-end closed impeller 53 is located.

[0167] 19 , a pump 10 according to a sixteenth embodiment differs from the first embodiment in that an orifice 39, which is an example of a pressure reducing device, is disposed outside the barrel 12. However, the configuration in which a pressure reducing device is disposed outside the barrel 12 is also applicable to the other embodiments.

[0168] A connecting pipe (connecting flow path) 90A, which penetrates the top wall 15 and leads out of the barrel 12, is connected to the outlet portion 33 of the cooling flow path 31. The tip of the connecting pipe 90A is connected to a sealed container 91. The sealed container 91 includes a container body 92 and a cover 93.

[0169] The container body 92 is a container with an open top, and is attached liquid-tight to the top wall 15. The container body 92 is provided with a through-hole 92a that penetrates in the vertical direction and into which a bolt 40 that constitutes the orifice 39 is screwed. The through-hole 92a communicates with the inside of the barrel 12 via a through-hole formed in the top wall 15. However, the container body 92 may be attached to the outer peripheral wall 13 of the barrel 12. Furthermore, the container body 92 may be configured so that the through-hole 92a and a through-hole in the barrel 12 are connected by a connecting pipe.

[0170] The cover 93 is detachably attached to the upper end of the container body 92 and liquid-tightly closes the opening of the container body 92. The cover 93 is provided with a connection hole 93a to which a connection pipe 90A is connected and which communicates with the inside of the container body 92.

[0171] In this pump 10, the orifice 39 is located outside the barrel 12. This allows the orifice 39 to be replaced during maintenance without disassembling the pump 10. This improves the maintainability of the pump 10. However, instead of the connecting pipe 90A, a connecting passage 90B composed of a first connecting passage 90a provided in the casing 22 and a second connecting passage 90b provided in the vessel body 92 may be used to connect the outlet 33 of the cooling passage 31 to the orifice 39 outside the barrel 12, as shown by the dashed-dotted line in FIG. 19 . The first connecting passage 90a and the second connecting passage 90b communicate with each other via a through-hole formed in the top wall 15. In this case, the outlet of the outlet 33 is closed, and the outlet 33 communicates with the inside of the barrel 12 via the connecting passage 90B and the through-hole 92a in the vessel body 92. This prevents the piping (connecting pipe 90A) from being extended outside the barrel 12. Furthermore, even when the connecting pipe 90A is used, if the tip of the connecting pipe 90A is connected to the second connecting passage 90b of the container body 92, the connecting pipe 90A can be prevented from being led out of the barrel 12. In this way, the structure connecting the outflow portion 33 of the cooling flow passage 31 and the orifice 39 outside the barrel 12 can be changed as necessary.

[0172] 20 , a pump 10 according to a seventeenth embodiment differs from the first embodiment in that a motor shaft 49 protrudes from the suction port 26 a into the barrel 12, and the tip of the motor shaft 49 is rotatably supported by a support portion 95. However, the configuration in which the tip of the motor shaft 49 is supported by a support portion 95 can also be applied to the other embodiments.

[0173] A bellmouth portion 22b is formed at the lower end of the casing 22, widening outward as it extends downward. The lower end opening of the bellmouth portion 22b forms the suction port 26a. The support portion 95 is container-shaped and open at the upper end, and is connected to the inner circumferential surface of the bellmouth portion 22b via a plurality of guide vanes 96 extending radially. A rolling bearing 57 that bears the radial load of the motor shaft 49 is disposed within the support portion 95. A through-hole 95a that penetrates radially through the support portion 95 is formed below the rolling bearing 57.

[0174] In this pump 10, the rolling bearing 57 that receives the radial load is disposed between the motor mounting portion 30 and the bearing mounting portion 34 in addition to the support portion 95. In other words, the motor shaft 49 is rotatably supported by one magnetic bearing (axial bearing) 55, one touchdown bearing 56, and two rolling bearings 57.

[0175] In this pump 10, when the number of closed impellers 53 that make up the impeller 52 is small, the length (shaft span) between adjacent support parts on the motor shaft 49 is also short, so that the pump can operate in a stable state when the natural frequency of all rotating bodies, including the impeller 52 and rotor 48, is higher than the operating frequency.

[0176] 21 , a pump 10 according to an eighteenth embodiment differs from the first embodiment in that a rolling bearing 57 that receives a radial load from the motor shaft 49 is provided between one of the plurality of closed impellers 53 that make up the impeller 52. However, the configuration in which a rolling bearing 57 is provided between the plurality of closed impellers 53 can also be applied to the other embodiments.

[0177] Specifically, the pump 10 is arranged such that the impeller 52, the superconducting motor 45, and the magnetic bearings 55 are arranged in this order from bottom to top along the axis A. Among these, the impeller arrangement section 28 in which the impeller 52 is arranged has a plurality of partition walls 28a that individually divide the closed impellers 53 that make up the impeller 52.

[0178] The rolling bearing 57 is attached to a partition wall 28a that separates the lowermost closed impeller 53 from the second-lowest closed impeller 53 in the impeller arrangement section 28. In other words, the partition wall 28a is provided in the space between adjacent closed impellers 53, and the rolling bearing 57 is arranged in the space between the lowermost closed impeller 53 and the second-lowest closed impeller 53. The partition wall 28a to which the rolling bearing 57 is attached has a communication hole 28g for ensuring the flow rate of the liquefied gas. However, the rolling bearing 57 may be arranged in a space other than the space between the lowermost closed impeller 53 and the second-lowest closed impeller 53, as long as it is between adjacent closed impellers 53. Furthermore, the rolling bearings 57 may be arranged in two or more spaces out of the multiple spaces formed by the multiple closed impellers 53.

[0179] In this type of pump 10, when the number of closed impellers 53 constituting the impeller 52 is large, the distance (shaft span) between the portions of the motor shaft 49 supported by bearings becomes long, and the natural frequency of all rotating bodies, including the impeller 52 and the rotor 48, becomes low. In contrast, in the pump 10 of this embodiment, a rolling bearing 57 is disposed in one of the spaces between the multiple closed impellers 53, and the distance between the portions of the motor shaft 49 supported by the rolling bearing 57 is shortened. Therefore, the natural frequency of the rotating bodies can be made higher than the operating frequency, and the pump 10 can be operated in a stable state.

[0180] 22 , the pump 10 of the 19th embodiment differs from the third embodiment in that the superconducting motor 45 is disposed above the impeller 52 and the magnetic bearing 55 is disposed below the impeller 52. However, the configuration in which the superconducting motor 45 and the magnetic bearing 55 are disposed in reverse is also applicable to the pumps 10 of the second, fourth, and fifteenth embodiments.

[0181] Specifically, the pump 10 is arranged along the axis A from bottom to top in the order of the magnetic bearing 55, the impeller 52, and the superconducting motor 45.

[0182] The liquefied gas delivery path 25 includes a suction section 26, a discharge section 27, and an impeller mounting section 28. The suction section 26 extends radially in the vertical middle section of the casing 22. The impeller mounting section 28 communicates with the suction section 26 and extends downward along the axis A. The discharge section 27 communicates with a discharge portion 28f located at the lowermost position of the impeller mounting section 28, and extends to the upper end of the casing 22, bypassing the impeller mounting section 28 and the motor mounting section 30.

[0183] The motor mounting section 30 is provided above the impeller mounting section 28. The interior of the motor mounting section 30 is in communication with the interior of the barrel 12 via a cooling flow path 31 having an inlet section (first inlet section) 32 and an outlet section (first outlet section) 33 formed by a plurality of through holes.

[0184] The bearing arrangement section 34 is provided below the impeller arrangement section 28 so as to be located on the opposite side to the motor arrangement section 30. The interior of the bearing arrangement section 34 is in communication with the interior of the barrel 12 via a cooling flow path 68 that has an inlet section (second inlet section) 69 in communication with the discharge section 28 f of the impeller arrangement section 28 and an outlet section (second outlet section) 70 that directly communicates with the interior of the barrel 12.

[0185] In this pump 10, as in the first embodiment, the overall size is kept down while the liquefied gas can be delivered with high efficiency, and the same functions and effects as those of the first embodiment can be obtained.

[0186] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0187] For example, the support of the motor shaft 49 of the superconducting motor 45 is not limited to the combination of the magnetic bearing 55 and the rolling bearing 57, but may be entirely made up of any of magnetic bearings, rolling bearings, and plain bearings. Also, a combination of a magnetic bearing and a plain bearing, or a combination of a rolling bearing and a plain bearing, may be used, and the combination of the types of bearings 55 and 57 can be changed as necessary.

[0188] In the second embodiment shown in FIG. 4, the third embodiment shown in FIG. 5, and the nineteenth embodiment shown in FIG. 22, the superconducting motor 45 may be configured so that the motor shaft 49 protrudes from the motor body 46 in only one direction (main portion 49a).

[0189] The pump unit 20 is not limited to a multi-stage diffuser pump, and may be any of a turbo-type centrifugal pump, a single-suction volute pump, a double-suction volute pump, a mixed-flow pump, a mixed-flow volute pump, a mixed-flow pump, and an axial pump, as long as it is housed within the barrel 12. It may also be a special type of volute pump or a cascade pump. In other words, the type of pump unit 20 can be changed as needed. Of course, the motor shaft 49 of the superconducting motor 45 may be a vertical shaft as in the first to eleventh and fourteenth to nineteenth embodiments, or a horizontal shaft as in the twelfth and thirteenth embodiments.

[0190] The impeller 52 used in the pump unit 20 is not limited to a multi-stage impeller, and may be configured as a single-stage impeller (i.e., one closed impeller 53). Furthermore, instead of the closed impeller 53, a semi-open impeller or an open impeller may be used, or an axial flow impeller or a mixed flow impeller may be used, and the type of impeller 52 can be changed as needed.

[0191] DESCRIPTION OF SYMBOLS 1 Hydrogen receiving equipment 2 Tank 3 Vaporizer 4 Gas turbine 10 Liquefied gas booster pump 12 Barrel (storage tank) 13 Outer wall 13a Flange portion 14 Bottom wall (first closure wall) 15 Top wall (second closure wall) 16 Intake portion 16a Intake port 17 Delivery portion 17a Delivery port 20 Pump unit 22 Casing 22a Flange portion 22b Bellmouth portion 25 Liquefied gas delivery path 26 Suction portion 26a Suction port 26b Communication hole 27 Discharge portion 27a Discharge port 28 Impeller arrangement portion 28A First impeller arrangement portion (first arrangement portion) 28B Second impeller arrangement portion (second arrangement portion) 28a to 28c Partition wall 28d Flow dividing wall 28e Communication section 28f Discharge section 28g Communication hole 30 Motor arrangement section 31 Cooling flow path (first cooling flow path) 32 Inlet section (first inlet section) 32a Expanding section 33 Outlet section (first outlet section) 33a First section 33b Second section 34 Bearing arrangement section 34a Recessed section 35 Balance piston (balancing device) 36 Fixed seat 37 Rotor 39 Orifice (pressure reducing device) 40 Bolt 45 Superconducting motor 46 Motor body 47 Stator 48 Rotor 49 Motor shaft 49a Main section 49b Auxiliary section 52 Impeller 52A First impeller 52B Second impeller 53 Closed impeller 53A Single suction closed impeller 53B Double suction closed impeller 53a Balance hole 53b Front shroud 53c Rear shroud 53d Blade 55 Magnetic bearing (axial bearing) 56 Touchdown bearing 57,DESCRIPTION OF SYMBOLS 57A to 57C Rolling bearing (radial bearing) 58 Inducer 60 Control unit 61 Distance measurement sensor 65 Axial flow impeller 66 Axial flow impeller arrangement unit 68 Cooling flow path (second cooling flow path) 69 Inlet portion (second inlet portion) 70 Outlet portion (second outlet portion) 72 Communication unit 74 Rotating shaft 75 Coupling 76 Coupling arrangement unit 78 Balance disk (balancing device) 78a Fixed disk 78b Rotating disk 80 Reduced pressure space unit 85 Support unit 87 Return pipe (return flow path) 88 Liquid supply pipe (liquid supply path) 90A Connecting pipe 90B Connecting flow path 90a First connecting path 90b Second connecting path 91 Sealed container 92 Container body 92a Through hole 93 Cover 93a Connecting hole 95 Support unit 95a Through hole 96 Guide vane A Axis (axial direction of motor shaft),

Claims

1. A storage tank having an intake port and a discharge port, and for storing liquefied gas taken in through the intake port; a casing disposed within the storage tank, having a liquefied gas delivery path including an intake port that opens to face the inside of the storage tank, a discharge port that communicates with the discharge port, and an impeller arrangement section formed between the intake port and the discharge port; an impeller disposed within the impeller arrangement section, for sucking the liquefied gas in the storage tank from the intake port through the liquefied gas delivery path by rotation and delivering it from the discharge port; and a superconducting motor having a motor body disposed within the casing and a motor shaft that protrudes from the motor body into the impeller arrangement section and for rotating the impeller, wherein the casing has: a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and is a space for arranging the motor body; a cooling flow path that spatially connects the storage tank and the motor arrangement section and cools the superconducting motor with the liquefied gas; the suction port of the liquefied gas delivery path is provided between the impeller arrangement section and the motor arrangement section; and the cooling flow path has a first inlet portion that communicates with the motor arrangement section and opens to face the inside of the storage tank, and a first outlet portion that communicates with the motor arrangement section on the upstream side of the impeller arrangement section of the liquefied gas delivery path.

2. A storage tank having an intake port and a discharge port, and storing liquefied gas taken in through the intake port; a casing arranged within the storage tank, having a liquefied gas delivery path including an intake port that opens to face the inside of the storage tank, a discharge port that communicates with the discharge port, and an impeller arrangement section formed between the intake port and the discharge port; an impeller arranged within the impeller arrangement section, which rotates to suck the liquefied gas in the storage tank from the intake port through the liquefied gas delivery path and deliver it from the discharge port; and a superconducting motor having a motor body arranged within the casing and a motor shaft that protrudes from the motor body toward the impeller arrangement section and rotates the impeller, wherein the casing has: a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and is a space in which the motor body is arranged; a cooling flow path that spatially connects the storage tank and the motor arrangement section and cools the superconducting motor with the liquefied gas; the suction port of the liquefied gas delivery path is provided between the impeller arrangement section and the motor arrangement section; and the cooling flow path has a first inlet portion that connects the motor arrangement section to the liquefied gas delivery path upstream of the impeller arrangement section, and a first outlet portion that connects to the motor arrangement section and is open to face the inside of the storage tank.

3. A storage tank having an intake port and a discharge port, and storing liquefied gas taken in through the intake port; a casing arranged within the storage tank, having a liquefied gas delivery path including an intake port that opens to face the inside of the storage tank, a discharge port that communicates with the discharge port, and an impeller arrangement section formed between the intake port and the discharge port; an impeller arranged within the impeller arrangement section, which rotates to suck the liquefied gas in the storage tank from the intake port through the liquefied gas delivery path and deliver it from the discharge port; a superconducting motor having a motor main body arranged within the casing and a motor shaft that protrudes from the motor main body into the impeller arrangement section and rotates the impeller; the casing has: a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and is a space in which the motor main body is arranged; a cooling flow path that spatially connects the storage tank and the motor placement section and cools the superconducting motor with the liquefied gas; the suction port of the liquefied gas delivery path is provided between the impeller placement section and the motor placement section; and the cooling flow path has a first inlet section and a first outlet section that communicate with the motor placement section and open to face the inside of the storage tank.

4. A storage tank having an intake port and a discharge port, and storing liquefied gas taken in through the intake port; a casing arranged within the storage tank, having a liquefied gas delivery path including an intake port that opens to face the inside of the storage tank, a discharge port that communicates with the discharge port, and an impeller arrangement section formed between the intake port and the discharge port; an impeller arranged within the impeller arrangement section, which rotates to draw the liquefied gas in the storage tank from the intake port through the liquefied gas delivery path and deliver it from the discharge port; a superconducting motor having a motor main body arranged within the casing and a motor shaft that protrudes from the motor main body into the impeller arrangement section and rotates the impeller; the casing has: a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and is a space in which the motor main body is arranged; a cooling flow path that spatially connects the storage tank and the motor arrangement section and cools the superconducting motor with the liquefied gas; the motor shaft protrudes in both directions from the motor body; the impeller arrangement section includes a first arrangement section and a second arrangement section that are spaced apart in the axial direction of the motor shaft; the impeller includes a first impeller arranged in the first arrangement section and a second impeller arranged in the second arrangement section; the motor arrangement section is provided between the first arrangement section and the second arrangement section; the cooling flow path has a first inlet section that communicates with the first arrangement section and connects the motor arrangement section to the inside of the storage tank via the liquefied gas delivery path, and a first outlet section that communicates with the motor arrangement section and the second arrangement section; the casing is provided with: a bearing arrangement section that is a space provided on the opposite side of the motor arrangement section from the second arrangement section and that accommodates bearings; a second inlet portion that communicates the interior of the liquefied gas delivery path with the interior of the bearing arrangement portion, and a second outlet portion that communicates the interior of the bearing arrangement portion with the interior of the storage tank.

5. A liquefied gas boost pump as claimed in any one of claims 1 to 3, wherein the casing is formed with a bearing arrangement section for arranging a bearing, the bearing arrangement section being a space provided on the opposite side of the impeller arrangement section from the motor arrangement section, a second inlet section connecting the inside of the liquefied gas delivery path with the inside of the bearing arrangement section, and a second outlet section connecting the inside of the bearing arrangement section with the inside of the storage tank.

6. A liquefied gas boost pump as described in claim 4, wherein a pressure reducing device is connected to the second outlet portion to make the pressure inside the bearing arrangement portion higher than the pressure inside the storage tank.

7. A liquefied gas boost pump as described in claim 5, wherein a pressure reducing device is connected to the second outlet portion to make the pressure inside the bearing arrangement portion higher than the pressure inside the storage tank.

8. A superconducting motor comprising: a storage tank having an intake port and a discharge port, and for storing liquefied gas taken in through the intake port; a casing disposed within the storage tank, and having a liquefied gas delivery path including an intake port that opens to face the inside of the storage tank, a discharge port that communicates with the discharge port, and an impeller arrangement section formed between the intake port and the discharge port; an impeller disposed within the impeller arrangement section, for sucking the liquefied gas in the storage tank from the intake port through the liquefied gas delivery path by rotation and delivering it from the discharge port; a motor body disposed within the casing; and a motor shaft that protrudes from the motor body into the impeller arrangement section and for rotating the impeller, wherein the casing has: a motor arrangement section that is adjacent to the impeller arrangement section in the axial direction of the motor shaft and is a space for arranging the motor body; a cooling flow path that spatially connects the inside of the storage tank and the inside of the motor arrangement section and cools the superconducting motor with the liquefied gas, wherein the cooling flow path has: an inlet portion that communicates with the impeller arrangement section and connects the motor arrangement section into the storage tank via the liquefied gas delivery path; and a return flow path that has one end connected to the motor arrangement section and the other end connected to the impeller arrangement section and that returns the liquefied gas directly from the motor arrangement section to the impeller arrangement section.

9. The liquefied gas booster pump according to claim 6, wherein the pressure reducing device is disposed outside the storage tank.

10. The liquefied gas boost pump according to claim 7, wherein the pressure reducing device is disposed outside the reservoir.

11. A liquefied gas boost pump as described in any one of claims 1 to 4 and 8, wherein the motor shaft protrudes from the suction port into the storage tank, the casing is provided with a support portion that supports the tip of the motor shaft, and a radial bearing that receives the radial load of the motor shaft is disposed in the support portion.

12. A liquefied gas boost pump as described in any one of claims 1 to 4 and 8, wherein the impeller is a multi-stage impeller in which multiple closed impellers are arranged with spaces between them in the axial direction of the motor shaft, and a radial bearing that bears the radial load of the motor shaft is arranged in at least one of the multiple spaces.

13. A liquefied gas boost pump as described in any one of claims 1 to 4 and 8, wherein the casing is provided with a radial bearing that receives a radial load from the motor shaft and an axial bearing that receives an axial load from the motor shaft, and the axial bearing is provided on the opposite side of the radial bearing from the motor body.

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