Pump and discharge method for low-temperature fluid in pump

Abstract

The present invention relates to a pump and a discharge method for a low-temperature fluid in the pump. The present invention comprises: a tank that stores the low-temperature fluid; a casing that has a hollow shape and is arranged in the interior of the tank; a rotating shaft that is arranged in the interior of the casing in the vertical direction; an impeller that is provided to the rotating shaft; and a drain pipe that is arranged in the interior of the tank with one end thereof being supported by an upper part of the tank and the other end thereof extending to the bottom of the tank, and the drain pipe opening to the interior of the tank.

Description

Pump and Method for Discharging Cryogenic Fluid in Pump

[0001] The present disclosure relates to a pump and a method for discharging cryogenic fluid in a pump.

[0002] As a pump for pressurizing liquid, for example, there is a technique described in Patent Document 1.

[0003] Japanese Unexamined Patent Application Publication No. 2005-105897

[0004] The pump pressurizes liquid hydrogen stored in a sump into high-pressure liquid hydrogen, and discharges the high-pressure liquid hydrogen to the outside. During maintenance, the pump needs to discharge all the liquid stored in the sump to the outside. A conventional pump is provided with a hermetically sealed connection portion at the lower end of the sump, and discharges liquid remaining in the sump to the outside from the hermetically sealed connection portion. However, if a maintenance liquid discharge portion is provided at the lower end of the sump, there is a concern about external leakage of liquid during operation of the pump. Further, if the liquid stored in the sump is a cryogenic fluid, external heat is transferred to the sump through the liquid discharge portion, which may increase the temperature of the liquid and cause it to vaporize.

[0005] The present disclosure solves the above-mentioned problems, and an object thereof is to provide a pump and a method for discharging cryogenic fluid in the pump, which can suppress leakage of the cryogenic fluid stored inside and suppress a state change of the cryogenic fluid.

[0006] The pump according to the present disclosure for achieving the above object comprises: a tank that stores a cryogenic fluid; a casing having a hollow shape and disposed inside the tank; a rotating shaft disposed along a vertical direction inside the casing; an impeller provided on the rotating shaft; and a drain pipe disposed inside the tank, with one end supported on an upper portion of the tank, the other end extending to a bottom portion of the tank, and opening into the inside of the tank.

[0007] Furthermore, the method for discharging cryogenic fluid in a pump according to the present disclosure comprises a tank for storing cryogenic fluid, a casing having a hollow shape and disposed inside the tank, a rotating shaft disposed vertically inside the casing, and an impeller provided on the rotating shaft, and includes the steps of: rotating the rotating shaft to discharge high-pressure cryogenic fluid pressurized by the impeller to the outside; stopping the rotation of the rotating shaft when it becomes impossible to draw cryogenic fluid into the casing; and discharging the cryogenic fluid remaining in the tank to the outside using a drain pipe disposed inside the tank, with one end supported at the top of the tank and the other end extending to the bottom of the tank and opening into the inside of the tank.

[0008] According to the pump and method for discharging cryogenic fluid in the pump described herein, leakage of cryogenic fluid stored inside can be suppressed, and changes in the state of the cryogenic fluid can be suppressed.

[0009] Figure 1 is a longitudinal cross-sectional view of the pump according to the first embodiment. Figure 2 is a longitudinal cross-sectional view of the lower part of the pump according to the second embodiment. Figure 3 is a schematic diagram showing the tip of the drain piping. Figure 4 is a lower cross-sectional view of the pump according to the first modified example. Figure 5 is a lower cross-sectional view of the pump according to the second modified example. Figure 6 is a cross-sectional view taken along the line VI-VI in Figure 5. Figure 7 is a longitudinal cross-sectional view of the lower part of the pump according to the third embodiment.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] [First Embodiment] <Pump> Figure 1 is a longitudinal cross-sectional view showing the pump of the first embodiment.

[0012] Pump 30 is a turbopump. Pump 30 has a drive unit 31 and a pump body 32, and the drive unit 31 has a drive motor 33. The pump body 32 is a device for pressurizing (increasing the pressure of) a cryogenic liquid (liquid hydrogen in this embodiment) as a fluid. Note that the cryogenic liquid is not limited to liquid hydrogen, but can be, for example, liquid nitrogen, liquid oxygen, liquefied carbon dioxide, liquefied natural gas, liquefied propane gas, etc.

[0013] The pump 30 includes a tank 41, a casing 51, a rotating shaft 52, and impellers 53A, 53B, and 53C.

[0014] The tank 41 is a container for storing liquid and is also a vacuum-insulated container. The tank 41 has a flange portion (lid portion) 42 on its upper part and is installed on a stand (not shown). The flange portion 42 is positioned on top of the tank 41 with the pump body 32 suspended, and is installed in an airtight manner. The tank 41 is an insulated structure with a bottomed cylindrical shape, and an internal liquid storage chamber 43 is formed.

[0015] Tank 41 has a supply pipe 44 and a gas discharge pipe 45 connected to its side. The supply pipe 44 is a pipe for supplying liquid from an external source to the liquid storage chamber 43 of tank 41. The supply pipe 44 is located on the bottom 41a side of tank 41. The gas discharge pipe 45 is a pipe for discharging vaporized components from the liquid storage chamber 43 to the outside. The gas discharge pipe 45 is located above the supply pipe 44.

[0016] The pump body 32 is located inside the tank 41. The pump body 32 comprises a casing 51, a rotating shaft 52, a plurality of impellers 53A, 53B, 53C, a plurality of radial bearings 54, 55, and a thrust bearing 56.

[0017] The casing 51 has a hollow shape. The casing 51 may be made from a single component or from multiple components assembled together. The casing 51 is placed inside the tank 41 and is suspended and supported by its upper end being connected to the flange portion 42. The casing 51 has a cylindrical shape centered on an axis O along the vertical direction, but is not limited to a cylindrical shape. Furthermore, the axis O is the center of the tank 41 and the casing 51, but the center of the tank 41 and the center of the casing 51 may be offset from each other.

[0018] The casing 51 has a suction section 61 at its lower end and a discharge section 62 at its upper end. The suction section 61 opens toward the liquid stored in the liquid storage chamber 43 of the tank 41. The discharge section 62 is connected to a discharge pipe 63. The suction section 61 may also be directly connected to a supply pipe 44 or piping extended from another supply pipe. In other words, the liquid may be introduced directly from the piping to the suction section 61 without first storing it in the liquid storage chamber 43 of the tank 41.

[0019] The rotating shaft 52 is arranged vertically inside the casing 51. The rotating shaft 52 has a cylindrical shape with axis O as its center. The casing 51 and the rotating shaft 52 are arranged concentrically with axis O as their center. Impellers 53A, 53B, and 53C are provided on the rotating shaft 52. Multiple impellers (three in this embodiment) are arranged at intervals along the axial direction of the rotating shaft 52. Impeller 53A is fixed to the lower end of the rotating shaft 52, and an inducer 64 is integrally provided with it. However, the inducer 64 does not have to be provided at the lower end of the rotating shaft 52. Impeller 53A and inducer 64 are located in the suction portion 61 of the casing 51. Impellers 53B and 53C are fixed to the rotating shaft 52 vertically above impeller 53A.

[0020] The impellers 53A, 53B, 53C and the inducer 64 are integrally mounted on the rotating shaft 52. The impellers 53A, 53B, 53C and the inducer 64 are rotatable integrally with the rotating shaft 52 and are also movable integrally in the axial direction. However, the number of impellers 53A, 53B, and 53C is not limited to three; it may be two or fewer, or four or more.

[0021] As the rotating shaft 52 rotates, the impellers 53A, 53B, 53C and the inducer 64 rotate together. As a result, the liquid in the liquid storage chamber 43 is drawn into the suction section 61 by the inducer 64 and pressurized by one stage by the impeller 53A. The pressurized liquid is then supplied to the impeller 53B through a passage 65 provided in the casing 51. Here, the liquid is pressurized by two stages by the impeller 53B. The pressurized liquid is then supplied to the impeller 53C through a passage 66 provided in the casing 51. Here, the liquid is pressurized by three stages by the impeller 53C.

[0022] The liquid, pressurized in three stages by the impeller 53C, is supplied to the discharge section 62 through a passage 67 provided in the casing 51 and discharged from the discharge pipe 63. Preferably, multiple passages 65, 66, and 67 are provided on the outside of the impellers 53A, 53B, and 53C, spaced apart in the circumferential direction.

[0023] The radial bearings 54 and 55 rotatably support the rotating shaft 52 relative to the casing 51. Multiple radial bearings 54 and 55 are provided (two in this embodiment). The radial bearing 54 is located at the upper vertical part of the casing 51, and the radial bearing 55 is located at the lower vertical part of the casing 51. Note that the number of radial bearings 54 and 55 is not limited to two; three or more may be provided. The radial bearings 54 and 55 withstand loads in a direction perpendicular to the rotating shaft 52 (radial direction of the rotating shaft 52). It is preferable to use rolling bearings (ball bearings) for the radial bearings 54 and 55, but they are not limited to rolling bearings (ball bearings).

[0024] The thrust bearing 56 rotatably supports the rotating shaft 52 relative to the casing 51. The thrust bearing 56 is positioned in the upper vertical part of the casing 51. Specifically, the thrust bearing 56 is positioned vertically above the multiple radial bearings 54 and 55. However, the position of the thrust bearing 56 is not limited to above the multiple radial bearings 54 and 55, but may be between the multiple radial bearings 54 and 55 or below the multiple radial bearings 54 and 55. The thrust bearing 56 receives the axial load of the rotating shaft 52.

[0025] Furthermore, the casing 51 houses the drive motor 33, which constitutes the drive unit 31. The drive motor 33 is positioned between the impeller 53C and the radial bearing 54. The drive motor 33 has a stator 33a and a rotor 33b. The stator 33a is fixed to the inner circumference of the casing 51. The stator 33a is cylindrical and has a stator core and stator coils. The rotor 33b is fixed to the outer circumference of the rotating shaft 52. The rotor 33b is cylindrical and has a rotor core (for example, a permanent magnet or laminated steel plate). In the drive motor 33, the stator 33a fixed to the casing 51 and the rotor 33b fixed to the rotating shaft 52 face each other radially with a gap between them.

[0026] <Liquid Hydrogen Discharge Device> The pump 30 includes a tank 41, a casing 51, a rotating shaft 52, and impellers 53A, 53B, and 53C, in addition to a liquid hydrogen discharge device 70.

[0027] The liquid hydrogen discharge device 70 includes a drain pipe 71 and a pressurized pipe 72. The drain pipe 71 discharges the liquid hydrogen remaining in the tank 41 to the outside. One end of the drain pipe 71 is supported on the upper part of the tank 41, and the other end extends to the bottom 41a of the tank 41. That is, as described above, the tank 41 is a bottomed cylindrical heat-insulating structure, and is provided with a flange portion (lid portion) 42 that closes the top. The flange portion 42 is not a heat-insulating structure, but it may be a heat-insulating structure. The upper end of the drain pipe 71 is fixed by penetrating the flange portion 42 in the thickness direction, and the lower end extends to the vicinity of the bottom surface of the tank 41. In this case, it is preferable that the lower end of the drain pipe 71 is open, and that the opening faces the bottom surface of the tank 41 with a small gap between them.

[0028] A drain valve 73 is provided outside the tank 41 for the drain pipe 71. The drain valve 73 can open and close the flow path of the drain pipe 71. One end of the drain pipe 71 is open to the atmosphere outside the tank 41, and when the drain valve 73 is opened, the liquid storage chamber 43 of the tank 41 communicates with the atmosphere. Alternatively, one end of the drain pipe 71 may not be open to the atmosphere, and the liquid storage chamber 43 may be connected to a liquid hydrogen supply source via a supply pipe 44.

[0029] The pressurized piping 72 pressurizes the inside of the tank 41 (liquid storage chamber 43) by supplying gas from outside to inside the tank 41. One end of the pressurized piping 72 is supported on the upper part of the tank 41, and the other end is positioned inside the tank 41. That is, the upper end of the pressurized piping 72 is fixed by penetrating the flange portion 42 in the thickness direction, and the lower end is located on the upper part of the tank 41, that is, in the gas phase above the liquid hydrogen level.

[0030] The pressurized piping 72 has a pressurizing source 74 connected to one end outside the casing, and a pressurizing valve 75 provided in the middle. The pressurizing source 74 can supply fluid to the pressurized piping 72 to pressurize the inside of the tank 41. The pressurizing valve 75 can open and close the flow path of the pressurized piping 72. When the pressurizing valve 75 is opened, the liquid storage chamber 43 of the tank 41 communicates with the pressurizing source 74. Preferably, the fluid supplied by the pressurizing source 74 is a gas obtained by heating a low-temperature fluid (liquid hydrogen) of the same type as the low-temperature fluid stored in the tank 41. That is, it is preferable that the pressurizing source 74 is connected to the liquid hydrogen supply source mentioned above, heats the liquid hydrogen to produce hydrogen gas, and supplies the hydrogen gas to the pressurized piping 72.

[0031] <Pump Operation> As shown in Figure 2, when the drive unit 31 (drive motor 33) is driven, the rotating shaft 52 rotates, and the impellers 53A, 53B, 53C and inducer 64 fixed to the rotating shaft 52 rotate, causing the pump body 32 to operate. When the pump body 32 operates, the liquid in the liquid storage chamber 43 is drawn into the suction section 61 by the inducer 64 and pressurized by one stage by the impeller 53A. The liquid pressurized by one stage is supplied to the impeller 53B through the passage 65 and pressurized by two stages. The liquid pressurized by two stages is supplied to the impeller 53C through the passage 66 and pressurized by three stages. The liquid pressurized by three stages is supplied to the discharge section 62 through the passage 67 and discharged from the discharge pipe 63.

[0032] <Pump Maintenance> During maintenance, the pump 30 needs to discharge all the liquid hydrogen stored in the liquid storage chamber 43 of the tank 41 to the outside. In this case, the casing 51 has its suction port 61 located at the bottom of the tank 41. Therefore, if the liquid level of the liquid hydrogen stored in the liquid storage chamber 43 falls below the suction port 61 at the lower end of the casing 51, the pump 30 will be unable to pressurize and discharge the liquid hydrogen stored in the liquid storage chamber 43 to the outside. In this case, the inability of the pump 30 to discharge the liquid hydrogen can be detected by detecting the flow rate and pressure of the liquid hydrogen discharged from the discharge port 62. At this time, the operation of the pump 30 is stopped, and then the liquid hydrogen discharge device 70 discharges the liquid hydrogen from the liquid storage chamber 43 to the outside.

[0033] After stopping the operation of the pump 30, the pressure valve 75 is opened first. Then, the pressurizing source 74 supplies hydrogen gas, which is generated by heating liquid hydrogen, to the liquid storage chamber 43 of the tank 41 through the pressurizing pipe 72. The liquid storage chamber 43 of the tank 41 is pressurized by the hydrogen gas supplied from the pressurizing pipe 72, and the pressure rises. In addition, liquid hydrogen is stored at the bottom 41a of the tank 41, and the pressure of this liquid hydrogen increases due to the hydrogen gas supplied from the pressurizing pipe 72.

[0034] Next, the drain valve 73 is opened. The liquid storage chamber 43 of the tank 41 is under pressurized hydrogen, and when the drain valve 73 opens the flow path of the drain pipe 71, the hydrogen in the liquid storage chamber 43 is pushed out into the drain pipe 71 and discharged to the outside through the drain pipe 71. At this time, any unvaporized liquid hydrogen is also discharged to the outside through the drain pipe 71. Once all the remaining liquid hydrogen in the liquid storage chamber 43 of the tank 41 has been discharged, the drain valve 73 and the pressure valve 75 are closed. After that, for example, an inert gas at room temperature (for example, nitrogen gas) may be supplied to the liquid storage chamber 43 of the tank 41 using the pressure pipe 72 and discharged to the outside using the drain pipe 71 to raise the temperature of the tank 41 to room temperature.

[0035] Once liquid hydrogen is discharged from the liquid storage chamber 43 of tank 41 and the temperature of tank 41 rises to room temperature, maintenance work is performed on pump 30.

[0036] In the first embodiment, the pump 30 has one end of the drain pipe 71 supported on the top of the tank 41, and the other end extending to the bottom 41a of the tank 41. When the pump 30 is operating, the drain pipe 71 is closed off by the drain valve 73, but external heat is easily transferred through the drain pipe 71 to the liquid hydrogen in the liquid storage chamber 43 of the tank 41. However, since the drain pipe 71 is supported on the top of the tank 41 and part of it is located in a space filled with hydrogen gas, sufficient cooling is achieved, making it difficult for external heat to be transferred to the liquid hydrogen in the liquid storage chamber 43, and thus suppressing the temperature rise of the liquid hydrogen.

[0037] [Second Embodiment] Figure 3 is a vertical cross-sectional view showing the lower part of the pump in the second embodiment, and Figure 4 is a schematic diagram showing the tip of the drain piping. Components having the same function as in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0038] <Liquid Hydrogen Discharge Device> As shown in Figure 3, the pump 30A comprises a tank 41, a rotating shaft 52, impellers 53A, 53B, and 53C (see Figure 2 for all), and a liquid hydrogen discharge device 70A.

[0039] The liquid hydrogen discharge device 70A includes a drain pipe 71A and a pressurized pipe 72. The pressurized pipe 72 is the same as in the first embodiment.

[0040] The drain pipe 71A discharges any liquid hydrogen remaining in the tank 41 to the outside. One end of the drain pipe 71A is supported at the top of the tank 41, and the other end extends to the bottom 41a of the tank 41. That is, the upper end of the drain pipe 71A is fixed by penetrating the flange portion 42 in the thickness direction, and the lower end extends to the vicinity of the bottom surface of the tank 41.

[0041] The drain pipe 71A is positioned so that its lower end is curved and follows the bottom surface of the tank 41. That is, the tank 41 has a curved shape where the bottom portion 41a is convex downward in the vertical direction. Therefore, the position of the center (axis O) of the bottom portion 41a of the tank 41 is the lowest position of the liquid storage chamber 43. It is preferable that the drain pipe 71A is positioned so that its lower end is curved and follows the bottom surface of the tank 41, and that its lower end is located at the lowest position of the bottom surface of the bottom portion 41a.

[0042] As shown in FIGS. 3 and 4, the drain pipe 71A includes a straight portion 81, a curved portion 82, and an opening 83. The straight portion 81 is arranged inside the tank 41 along the vertical direction. The curved portion 82 is connected to the lower end of the straight portion 81. In the curved portion 82, the opening 83 is formed at the distal end along the bottom surface of the bottom portion 41a. The opening 83 has an opening surface inclined with respect to the axial direction of the drain pipe 71A. That is, although the drain pipe 71A (the straight portion 81 and the curved portion 82) is a cylindrical pipe, by cutting the distal end obliquely, the opening surface of the opening 83 becomes elliptical.

[0043] Note that, similarly to the drain pipe 71, the drain pipe 71A is provided with a drain valve 73 (see FIG. 2) outside the tank 41.

[0044] Therefore, when the pressure increasing valve 75 (see FIG. 2) is opened after the operation of the pump 30A is stopped, heated hydrogen gas is supplied to the liquid storage chamber 43 of the tank 41 through the pressure increasing pipe 72. In the tank 41, the pressure of the liquid storage chamber 43 is increased by the hydrogen gas supplied from the pressure increasing pipe 72, so that the pressure inside the tank 41 rises. Further, liquid hydrogen is stored in the bottom portion 41a of the tank 41, and the pressure of this liquid hydrogen is increased by the hydrogen gas supplied from the pressure increasing pipe 72.

[0045] Here, when the drain valve 73 (see FIG. 2) is opened, the hydrogen in the liquid storage chamber 43 of the tank 41 is pushed out into the drain pipe 71A and discharged to the outside through the drain pipe 71A. At this time, since the opening 83 of the drain pipe 71A is located on the bottom surface of the bottom portion 41a of the tank 41, all the liquid hydrogen remaining in the bottom portion 41a of the liquid storage chamber 43 of the tank 41 can be discharged to the outside without any residue. When all the liquid hydrogen remaining in the liquid storage chamber 43 of the tank 41 is discharged, the drain valve 73 and the pressure increasing valve 75 are closed.

[0046] <First Modification> FIG. 5 is a lower cross-sectional view illustrating the pump according to the first modification.

[0047] As shown in FIG. 5, the pump 30B of the first modification includes a tank 41, a rotating shaft 52, impellers 53A, 53B, 53C (all see FIG. 2), and a liquid hydrogen discharge device 70B.

[0048] The liquid hydrogen discharge device 70B includes a drain pipe 71B and a pressurizing pipe 72. The pressurizing pipe 72 is the same as that in the first embodiment.

[0049] The drain pipe 71B discharges liquid hydrogen remaining in the tank 41 to the outside. One end of the drain pipe 71B is supported at an upper portion of the tank 41, and the other end extends to a bottom portion 41a of the tank 41. That is, an upper end of the drain pipe 71B penetrates through a flange portion 42 in a thickness direction and is fixed thereto, and a lower end thereof extends to a vicinity of a bottom surface of the tank 41.

[0050] The drain pipe 71B is arranged such that a lower end thereof is curved and extends along the bottom surface of the tank 41. The drain pipe 71B includes a straight portion 81, a curved portion 82, an opening 83, and a spiral portion 84. The straight portion 81 is arranged inside the tank 41 along a vertical direction. The spiral portion 84 is connected to a lower end of the straight portion 81, and is arranged to swirl around the drive unit 31 and the pump main body 32. The spiral portion 84 is arranged above a liquid level of liquid hydrogen in the liquid storage chamber 43. The curved portion 82 is connected to a lower end of the spiral portion 84. The curved portion 82 has the opening 83 formed at a tip end portion along the bottom surface of the bottom portion 41a. The opening 83 has an opening surface inclined with respect to an axial direction of the drain pipe 71B.

[0051] Note that the spiral portion 84 is not limited to the configuration described above. The spiral portion 84 may be arranged not only to make one turn around the drive unit 31 and the pump main body 32, but also to make a plurality of turns therearound. Further, the spiral portion 84 may be arranged to swirl around a position of the straight portion 81 without swirling around the drive unit 31 and the pump main body 32.

[0052] The drain pipe 71B has a spiral section 84 between a straight section 81 and a curved section 82, and the spiral section 84 is positioned above the liquid level of liquid hydrogen in the liquid storage chamber 43. When the pump 30B is operating, the flow path of the drain pipe 71B is closed by the drain valve 73 (see Figure 2), but external heat is easily transferred through the drain pipe 71B to the liquid hydrogen in the liquid storage chamber 43 of the tank 41. However, since the straight section 81 and the spiral section 84 of the drain pipe 71B are positioned in a space filled with hydrogen gas, sufficient cooling is achieved, making it difficult for external heat to be transferred to the liquid hydrogen in the liquid storage chamber 43, and thus suppressing the temperature rise of the liquid hydrogen.

[0053] <Second Modification> Figure 6 is a lower cross-sectional view of the pump in the second modification, and Figure 7 is a cross-sectional view taken along line VII-VII in Figure 6.

[0054] As shown in Figures 6 and 7, the second modified pump 30C comprises a tank 41, a rotating shaft 52, impellers 53A, 53B, and 53C (see Figure 2), and a liquid hydrogen discharge device 70C.

[0055] The liquid hydrogen discharge device 70C includes a drain pipe 71A, a pressurized pipe 72, and a guide member 91. The drain pipe 71A and the pressurized pipe 72 are the same as in the second embodiment.

[0056] The guide member 91 has a horizontal plate 92 and a plurality of guide plates 93. The horizontal plate 92 is disc-shaped, and its outer diameter is slightly smaller than the inner diameter of the cylindrical part of the tank 41. The horizontal plate 92 is positioned slightly above the bottom surface of the bottom 41a of the tank 41, and its outer circumference contacts the inner circumference of the bottom 41a. The plurality of guide plates 93 are connected to the lower surface of the horizontal plate 92 at circumferential intervals. The plurality of guide plates 93 are arranged radially from the center (axis O) of the tank 41, along the radial direction of the tank 41. However, the plurality of guide plates 93 are not positioned at the center (axis O) of the horizontal plate 92. The guide plates 93 are roughly triangular in shape, and their lower surfaces are in close contact with the bottom surface of the bottom 41a.

[0057] The guide member 91 has multiple notches 94 provided in the horizontal plate 92. The notches 94 in the horizontal plate 92 allow the inside of the tank 41 to communicate between the upper and lower parts of the horizontal plate 92. The lower end of the drain pipe 71A penetrates the horizontal plate 92.

[0058] When the pump 30C stops, the liquid hydrogen remaining in the liquid storage chamber 43 of the tank 41 collects at the center of the bottom 41a along the multiple guide plates 93 of the guide member 91. Therefore, the drain pipe 71C can take in the liquid hydrogen collected at the center of the bottom 41a through the opening 83 and discharge it completely to the outside.

[0059] [Third Embodiment] Figure 8 is a longitudinal cross-sectional view showing the lower part of the pump according to the third embodiment. Note that components having the same function as those in the second embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0060] <Liquid Hydrogen Discharge Device> As shown in Figure 8, the pump 30D comprises a tank 41, a rotating shaft 52, impellers 53A, 53B, and 53C (see Figure 2 for all), and a liquid hydrogen discharge device 70D.

[0061] The liquid hydrogen discharge device 70D includes a drain pipe 71D and a pressurized pipe 72D.

[0062] The drain pipe 71D discharges any liquid hydrogen remaining in the tank 41 to the outside. One end of the drain pipe 71D is supported on the top of the tank 41, and the other end extends to the bottom 41a of the tank 41. That is, the upper end of the drain pipe 71D is bent horizontally and fixed through the upper part of the tank 41 in the thickness direction, and the lower end extends to the vicinity of the bottom surface of the tank 41. The lower end of the drain pipe 71D is curved and positioned to follow the bottom surface of the tank 41.

[0063] The pressurized pipe 72D pressurizes the inside of the tank 41 by supplying gas from outside to inside the tank 41. One end of the pressurized pipe 72D is supported on the upper part of the tank 41, and the other end is positioned inside the tank 41. That is, the pressurized pipe 72D is fixed by penetrating the upper part of the tank 41 in the thickness direction, and its end is located in the upper part of the tank 41, i.e., in the gas phase above the liquid hydrogen level.

[0064] [Effects of this embodiment] The pump according to the first embodiment comprises a tank 41 for storing liquid hydrogen (low-temperature fluid), a casing 51 having a hollow shape and arranged inside the tank 41, a rotating shaft 52 arranged vertically inside the casing 51, impellers 53A, 53B, 53C provided on the rotating shaft 52, and drain pipes 71, 71A, 71B, 71D arranged inside the tank 41, one end of which is supported on the upper part of the tank 41 and the other end extends to the bottom 41a of the tank 41 and opens into the inside of the tank 41.

[0065] According to the pump of the first embodiment, when pumps 30, 30A, 30B, 30C, and 30D are in operation, external heat is transferred to the drain pipes 71, 71A, 71B, and 71D. However, since the drain pipes 71, 71A, 71B, and 71D extend from the top to the bottom 41a of the tank 41, a portion of them is cooled by the hydrogen gas inside the tank 41. This makes it difficult for external heat to be transferred to the liquid hydrogen in the liquid storage chamber 43, thereby suppressing the temperature rise of the liquid hydrogen. As a result, leakage of the fluid hydrogen stored inside the tank 41 can be suppressed, and changes in the state of the liquid hydrogen can be suppressed.

[0066] The pump according to the second embodiment is the same as the pump according to the first embodiment, further comprising a tank 41 which is a bottomed cylindrical insulated structure, a flange portion (lid portion) 42 which closes the top of the tank 41, and drain pipes 71, 71A, and 71B which are supported with one end passing through the flange portion 42b. As a result, by making the tank 41 an insulated structure, the liquid hydrogen stored in the tank 41 can be maintained at an appropriate temperature, and by supporting the upper ends of the drain pipes 71, 71A, and 71B with the flange portion 42, there is no need to provide support holes or the like in the insulated structure of the tank 41, and a decrease in the cooling function of the tank 41 can be suppressed.

[0067] The pump according to the third embodiment is the pump according to the first or second embodiment, further comprising drain pipes 71A, 71B, 71C, and 71D, the other ends of which are curved and arranged to follow the bottom surface of the tank 41. This allows the liquid hydrogen at the bottom 41a of the tank 41 to be completely discharged to the outside by the drain pipes 71A, 71B, 71C, and 71D.

[0068] The pump according to the fourth embodiment is the pump according to the third embodiment, further comprising a straight section 81 arranged vertically inside the tank 41, a curved section 82 connected to the lower end of the straight section 81, and an opening 83 located at the tip of the curved section 82, which forms an opening surface inclined with respect to the axial direction. This allows the lower ends of the drain pipes 71A, 71B, 71C, and 71D to be appropriately positioned along the bottom 41a of the tank 41.

[0069] The pump according to the fifth embodiment is a pump according to any one of the first to fourth embodiments, and furthermore, the drain pipes 71, 71A, 71B, 71C, and 71D are provided with drain valves 73 that open and close the flow path outside the tank 41. As a result, when the pumps 30, 30A, 30B, 30C, and 30D are in operation, the drain valves 73 can be closed to suppress heat transfer from the outside to the inside of the tank 41, and leakage of liquid hydrogen from inside the tank 41 to the outside can be suppressed.

[0070] The pump according to the sixth embodiment is a pump according to any one of the first to fifth embodiments, and further has pressurizing pipes 72, 72D that are supported on the top of the tank 41 and capable of supplying gas from outside the tank 41 to the inside to pressurize it. As a result, by supplying gas to the inside of the tank 41 via the pressurizing pipes 72, 72D to pressurize it, liquid hydrogen or hydrogen gas inside the tank 41 can be efficiently discharged from the drain pipes 71, 71A, 71B, 71C, 71D.

[0071] The pump according to the seventh embodiment is the same as the pump according to the sixth embodiment, and further, the pressurized piping 72 supplies a gas, which is the same type of liquid hydrogen as that stored in the tank 41, heated into the tank 41. This allows for efficient use of liquid hydrogen, and the hydrogen gas discharged to the outside of the tank 41 can be collected and reused.

[0072] The pump according to the eighth embodiment is a pump according to any one of the first to seventh embodiments, and furthermore, the tank 41 has a curved shape in which the bottom surface is convex downward in the vertical direction. This allows the liquid hydrogen remaining in the tank 41 to be collected at the center of the bottom 41a, and the liquid hydrogen can be properly discharged by the drain pipes 71, 71A, 71B, 71C, and 71D.

[0073] The pump according to the ninth embodiment is a pump according to any one of the first to seventh embodiments, further comprising a tank 41 which is a bottomed cylindrical heat-insulating structure, a flange portion (lid portion) 42 which closes the top of the tank 41, and a drain pipe 71D which is supported with one end passing through the upper part of the tank 41. This allows one end of the drain pipe 71D to extend to the side of the tank 41, and a space can be secured above the tank 41.

[0074] A method for discharging cryogenic fluid in a booster pump according to the tenth embodiment includes a tank 41 for storing liquid hydrogen (cryogenic fluid), a step of rotating a rotating shaft 52 to discharge high-pressure liquid hydrogen pressurized by impellers 53A, 53B, and 53C to the outside, a step of stopping the rotation of the rotating shaft 52 when it becomes impossible to draw liquid hydrogen into the casing 51, and a step of discharging the fluid hydrogen remaining in the tank 41 to the outside using drain pipes 71, 71A, 71B, 71C, and 71D which are arranged inside the tank 41, with one end supported at the top of the tank 41 and the other end extending to the bottom 41a of the tank 41 and opening into the inside of the tank 41. This makes it possible to appropriately discharge the fluid hydrogen remaining in the tank 41, suppress leakage of fluid hydrogen stored inside the tank 41, and suppress changes in the state of liquid hydrogen.

[0075] 30, 30A, 30B, 30C, 30D Pump 31 Drive unit 32 Pump body 33 Drive motor 41 Tank 42 Flange section (lid section) 43 Liquid storage chamber 44 Supply pipe 45 Gas discharge pipe 51 Casing 52 Rotating shaft 53A, 53B, 53C Impeller 54, 55 Radial bearing 56 Thrust bearing 61 Intake section 62 Discharge section 63 Discharge pipe 64 Inducer 65, 66, 67 Passage 70, 70A, 70B, 70C, 70D Liquid hydrogen discharge device 71, 71A, 71B, 71C, 71D Drain piping 72, 72D Pressurized piping 73 Drain valve 74 Pressurized source 75 Pressurized valve 81 Straight section 82 Curved section 83 Opening 84 Spiral section 91 Guide member

Claims

1. A pump comprising: a tank for storing a cryogenic fluid; a casing having a hollow shape and disposed inside the tank; a rotating shaft disposed vertically inside the casing; an impeller provided on the rotating shaft; and a drain pipe disposed inside the tank, with one end supported at the top of the tank and the other end extending to the bottom of the tank and opening into the inside of the tank.

2. The pump according to claim 1, wherein the tank is a bottomed cylindrical insulated structure, is provided with a lid that closes the top of the tank, and the drain pipe is supported with one end passing through the lid.

3. The pump according to claim 1 or claim 2, wherein the other end of the drain pipe is curved and arranged to follow the bottom surface of the casing.

4. The pump according to claim 3, wherein the drain pipe has a straight section arranged vertically inside the tank, a curved section connected to the lower end of the straight section, and an opening located at the tip of the curved section that forms an opening surface inclined with respect to the axial direction.

5. The pump according to claim 1, wherein the drain piping is provided with a drain valve outside the tank for opening and closing the flow path.

6. The pump according to claim 1, further comprising a pressurizing pipe supported on the top of the tank and capable of supplying gas from the outside to the inside of the tank to pressurize it.

7. The pump according to claim 6, wherein the pressurized piping supplies a gas obtained by heating a cryogenic fluid of the same type as the cryogenic fluid stored in the tank into the interior of the casing.

8. The pump according to claim 1, wherein the tank has a curved shape with its bottom surface convex downward in the vertical direction.

9. The pump according to claim 1, wherein the tank is a bottomed cylindrical insulated structure, is provided with a lid that closes the top of the tank, and one end of the drain pipe is supported by passing through the upper part of the tank.

10. A method for discharging cryogenic fluid in a pump comprising: a tank for storing cryogenic fluid; a casing having a hollow shape and disposed inside the tank; a rotating shaft disposed vertically inside the casing; and an impeller provided on the rotating shaft, the method comprising: rotating the rotating shaft to discharge high-pressure cryogenic fluid pressurized by the impeller to the outside; stopping the rotation of the rotating shaft when it becomes impossible to draw cryogenic fluid into the casing; and discharging the cryogenic fluid remaining in the tank to the outside using a drain pipe disposed inside the tank, with one end supported at the top of the tank and the other end extending to the bottom of the tank and opening into the inside of the tank.

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