Pump device

Abstract

This pump device according to the present disclosure comprises: a rotating shaft that extends from an axis and is rotatable about the axis; a casing that covers the rotating shaft from the outer peripheral side; an impeller that is provided integrally with the rotating shaft in the casing and that rotates together with the rotating shaft to pressure-feed a low-temperature fluid from one side to the other side in the axial direction; an electric motor that is provided on the other side in the axial direction with respect to the impeller in the casing and that includes a stator fitted to the inner peripheral surface of the casing and a rotor that is integrally fixed to the rotating shaft inside the stator; and a plurality of discharge flow path pipes that are provided outside the casing at an interval from the casing in the radial direction, and at intervals in the circumferential direction with respect to each other, and that cause the low-temperature fluid pressure-fed by the impeller to flow to the other side in the axial direction so as to bypass the electric motor.

Description

Pump equipment

[0001] This application claims priority to Japanese Patent Application No. 2024-124737, filed on July 31, 2024, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 discloses a pump for pumping a low-temperature, low-viscosity fluid. This pump includes a pump unit that increases the pressure of the fluid and a motor unit that drives the pump unit.

[0003] Japanese Patent Application Laid-Open No. 2005-105897

[0004] When fluid flows out of the pump discharge nozzle in one direction, the flow becomes uneven in the circumferential direction, which is known to increase the radial thrust acting on the pump's rotating shaft.

[0005] The present disclosure provides a pump device that can appropriately hold the stator of an electric motor while suppressing radial thrust.

[0006] In order to solve the above problems, the pump device of the present disclosure includes a rotating shaft extending around an axis and rotatable around the axis, a casing covering the rotating shaft from an outer periphery, an impeller provided integrally with the rotating shaft within the casing and rotating together with the rotating shaft to pump a low-temperature fluid from one side to the other in the axial direction, a stator provided within the casing on the other side in the axial direction of the impeller and fitted to the inner circumferential surface of the casing, and an electric motor having a rotor fixed integrally to the rotating shaft inside the stator, and a plurality of discharge flow path pipes provided outside the casing at radial intervals from the casing and at circumferential intervals from each other, and which circulate the low-temperature fluid pumped by the impeller to the other side in the axial direction so as to bypass the electric motor.

[0007] According to the pump device of the present disclosure, the stator of the electric motor can be appropriately held while suppressing radial thrust.

[0008] Fig. 1 is a schematic configuration diagram of a pump device according to an embodiment of the present disclosure; Fig. 2 is a plan view of a confluent flow path according to an embodiment of the present disclosure as viewed from above; Fig. 3 is a side view of a cryogenic fluid pump and a plurality of discharge flow path pipes according to an embodiment of the present disclosure as viewed from the radial outside; Fig. 4 is a diagram showing both ends of the discharge flow path pipe according to an embodiment of the present disclosure; Fig. 5 is a side view of a cryogenic fluid pump and a plurality of discharge flow path pipes according to a modified example of the present disclosure as viewed from the radial outside;

[0009] (Configuration of Pump Device) A pump device 1 according to an embodiment of the present disclosure will be described below with reference to FIGS. 1 to 4. The pump device 1 is a device that pressurizes a cryogenic fluid L. In this embodiment, the cryogenic fluid L is liquefied hydrogen. The cryogenic fluid L pressurized by the pump device 1 is not limited to liquid hydrogen, and may be other liquids or gases. For example, the cryogenic fluid L may be a liquefied gas other than liquid hydrogen, such as natural gas (LNG) or liquefied petroleum gas (LPG). As shown in FIG. 1, the pump device 1 includes a sump 10, a cryogenic fluid pump 20, and a discharge flow path 60.

[0010] (Sump) The sump 10 stores the cryogenic fluid L (liquid hydrogen in this embodiment). The sump 10 is a vacuum insulated container. That is, the sump 10 is a thermally insulated structure having a cylindrical shape with a bottom. The sump 10 is installed on a stand (not shown). The sump 10 has a sump body 11, an outer peripheral flange 12, an upper flange 13, and a mounting wall 14. The sump body 11 is formed in a cylindrical shape with a bottom that opens upward. A liquid storage chamber 15 is formed inside the sump body 11. The liquid storage chamber 15 stores the cryogenic fluid L. A supply pipe 2 and a gas discharge pipe 3 are connected to the side of the sump body 11. The supply pipe 2 is a pipe that can supply the cryogenic fluid L from an external supply source into the liquid storage chamber 15. The gas discharge pipe 3 is a pipe capable of discharging the gas component of the low-temperature fluid L vaporized in the liquid storage chamber 15 to the outside of the sump 10. The gas discharge pipe 3 is provided vertically above the supply pipe 2. The gas discharge pipe 3 may also be capable of discharging the liquid component of the low-temperature fluid L to the outside of the sump 10.

[0011] The outer peripheral flange 12 is provided on the upper side of the sump body 11 and protrudes from the outer peripheral surface of the sump body 11. The upper flange 13 is attached to the upper part of the sump body 11. It closes the opening of the sump body 11. The upper flange 13 is attached to contact the outer peripheral flange 12 from above, maintaining airtightness inside the liquid storage chamber 15. The mounting wall portion 14 is attached to the underside of the upper flange 13. The mounting wall portion 14 is a flat member extending horizontally.

[0012] (Cryogenic Fluid Pump) The cryogenic fluid pump 20 is a device that pressurizes the cryogenic fluid L (liquid hydrogen in this embodiment) to a target pressure and pumps it out. The cryogenic fluid pump 20 is disposed in the sump 10. The cryogenic fluid pump 20 includes a rotating shaft 21, a casing 30, a bearing device 40, an impeller 4, and an inducer 5.

[0013] (Rotation shaft) The rotation shaft 21 extends about an axis O. In the following, an embodiment will be described taking as an example a case where the axis O extends vertically, with one side of the axis O being downward and the other side of the axis O being upward. In addition, the circumferential direction about this axis O will be simply referred to as the circumferential direction, and the radial direction about this axis O will be simply referred to as the radial direction. The rotation shaft 21 is provided so as to be rotatable around this axis O.

[0014] (Casing) The casing 30 covers the rotating shaft 21 from the outside. The casing 30 forms the outer shell of the cryogenic fluid pump 20. The casing 30 has a hollow shape. The casing 30 is suspended from the upper flange 13 via the mounting wall 14. The casing 30 has a cylindrical shape centered on the axis O, but is not limited to this. Furthermore, although the sump 10 and the casing 30 both extend around the axis O, the centers of the sump 10 and the casing 30 may be offset from each other. The casing 30 accommodates each component of the cryogenic fluid pump 20, such as the rotating shaft 21, the bearing device 40, the electric motor 50, the impeller 4, and the inducer 5. The casing 30 may be composed of a single member or may be composed of multiple members assembled together. The casing 30 of this embodiment has a double-shell structure. That is, the casing 30 has an outer casing 31 and an inner casing 32 .

[0015] (External Casing) The external casing 31 is formed in a simple cylindrical shape centered on the axis O. The external casing 31 includes a motor casing 33, a pump casing 34, and a flange portion 35. The motor casing 33 is formed in a cylindrical shape with a bottom that opens downward. The pump casing 34 is disposed below the motor casing 33. The pump casing 34 is formed in a cylindrical shape with a bottom that opens upward. The flange portion 35 includes an upper flange 35a provided at the lower end of the motor casing 33 and a lower flange 35b provided at the upper end of the pump casing 34. The upper flange 35a protrudes radially outward from the outer peripheral surface of the motor casing 33. The upper flange 35a is formed integrally with the motor casing 33. The lower flange 35b protrudes radially outward from the outer peripheral surface of the pump casing 34. The lower flange 35b is formed integrally with the pump casing 34. The lower flange 35b contacts the upper flange 35a and is fixed to the upper flange 35a by, for example, bolts (not shown). The flange portion 35 firmly assembles the motor casing 33 and the pump casing 34 together.

[0016] A suction section 36 is provided at the lower end of the pump casing 34. The suction section 36 opens downward. The cryogenic fluid L stored in the liquid storage chamber 15 of the sump 10 is drawn into the casing 30 through the suction section 36. Note that the suction section 36 may be directly connected to a pipe extending from a supply pipe or another supply pipe. In other words, the cryogenic fluid L may be introduced directly into the suction section 36 from a pipe without first being stored in the liquid storage chamber 15 of the sump 10.

[0017] (Internal Casing) The internal casing 32 is covered from the outer periphery by the external casing 31. More specifically, the internal casing 32 is housed in a pump casing 34 that constitutes the external casing 31. The internal casing 32 houses the impeller 4. A pre-discharge chamber 37 is formed between the internal casing 32 and the external casing 31. The pre-discharge chamber 37 is filled with the low-temperature fluid L pressurized by the impeller 4. In this embodiment, the pre-discharge chamber 37 is supplied with the low-temperature fluid L compressed in the final stage of the multiple impellers 4. The low-temperature fluid L temporarily stored in the pre-discharge chamber 37 is discharged to the outside of the casing 30 through a discharge flow path piping 62, which will be described later.

[0018] (Bearing Device) The bearing device 40 is a device that supports the rotating shaft 21 so that the rotating shaft 21 can rotate about the axis O. The bearing device 40 includes a radial bearing 41, a thrust disk 42, and a thrust bearing 43.

[0019] (Radial Bearing) The radial bearing 41 is arranged to receive a radial load from the rotating shaft 21. That is, the radial bearing 41 is arranged concentrically with the rotating shaft 21 and is arranged to cover the outer circumferential surface of the rotating shaft 21. A plurality of radial bearings 41 are provided. In this embodiment, an upper radial bearing 41a and a lower radial bearing 41b are provided. The upper radial bearing 41a is arranged vertically above the casing 30. The upper radial bearing 41a supports the upper part of the rotating shaft 21 rotatably around the axis O. The lower radial bearing 41b is arranged vertically below the casing 30. The lower radial bearing 41b supports the lower part of the rotating shaft 21 rotatably around the axis O. The type of the radial bearing 41 is not limited. For example, the radial bearing 41 may be a rolling bearing, a sliding bearing, or a magnetic bearing. Furthermore, the upper radial bearing 41a and the lower radial bearing 41b may be of the same type or may be of different types.

[0020] (Thrust Disk) The thrust disk 42 is fixed to the outer periphery of the rotating shaft 21. The thrust disk 42 is circular and is provided so as to expand the diameter of the rotating shaft 21 in the radial direction while fixed to the rotating shaft 21. The thrust disk 42 is rotatable integrally with the rotating shaft 21. The thrust disk 42 is also movable integrally with the rotating shaft 21 in the direction of the axis O.

[0021] (Thrust Bearing) The thrust bearing 43 is arranged to sandwich the thrust disk 42 in the direction of the axis O. The thrust bearing 43 in this embodiment is a hydrostatic bearing. The thrust bearing 43 is, for example, a non-contact bearing. For example, the thrust bearing 43 may be a magnetic bearing. However, the thrust bearing 43 is not limited to a non-contact bearing. Furthermore, the thrust bearing 43 is arranged vertically above the upper radial bearing 41 a and the lower radial bearing 41 b. However, the position where the thrust bearing 43 is arranged is not limited to this. The thrust bearing 43 may be arranged between the upper radial bearing 41 a and the lower radial bearing 41 b, or vertically below the upper radial bearing 41 a and the lower radial bearing 41 b.

[0022] (Electric Motor) The electric motor 50 drives the rotating shaft 21 to rotate around the axis O. The electric motor 50 is provided between the upper radial bearing 41a and the lower radial bearing 41b. The electric motor 50 has a stator 51 and a rotor 52. The stator 51 is fitted to the inner circumferential surface of the casing 30. The stator 51 is cylindrical and has a stator core and a stator coil. The rotor 52 is fixed integrally to the rotating shaft 21 inside the stator 51. The rotor 52 is cylindrical and has a rotor 52 core (e.g., a permanent magnet or laminated steel plate). The stator 51 fixed to the casing 30 and the rotor 52 fixed to the rotating shaft 21 face each other in the radial direction with a gap between them.

[0023] (Impeller) A plurality of impellers 4 are provided within the casing 30 on one side (lower) of the electric motor 50 in the direction of the axis O. In other words, the electric motor 50 is provided within the casing 30 on the other side (upper) of the impellers 4 in the direction of the axis O. The impellers 4 are provided integrally with the rotary shaft 21 within the casing 30 and rotate together with the rotary shaft 21 to pump the cryogenic fluid L from one side to the other side (upper to lower) in the direction of the axis O. A plurality of impellers 4 are provided lined up vertically. The plurality of impellers 4 includes a pair of impellers 4 mounted back to back. In addition, in this embodiment, the lower radial bearing 41b is provided between two adjacent impellers 4. Note that, although the present embodiment has been described with respect to a case where multiple stages of impellers 4 are provided, this is not limiting. The number of impellers 4 can be changed as appropriate, and only one impeller 4 may be provided. In this embodiment, the plurality of impellers 4 are housed in an inner casing 32. The plurality of impellers 4 are held by the inner casing 32 so that their positions do not fluctuate.

[0024] (Inducer) The inducer 5 is provided below the lower radial bearing 41b and the multiple impellers 4. The inducer 5 is disposed in the suction section 36 of the casing 30. The inducer 5 rotates integrally with the rotating shaft 21. The rotation of the inducer 5 causes the cryogenic fluid L to be sucked into the casing 30.

[0025] 1 to 4, the configuration of the discharge flow path 60 will be described. The discharge flow path 60 is a flow path that discharges the cryogenic fluid L pressurized by the impeller 4 to the outside of the pump device 1. The discharge flow path 60 includes a connection flow path 61, a discharge flow path piping 62, a merging flow path 63, and a discharge pipe 64.

[0026] (Connection Flow Channel) The connection flow channels 61 connect the pre-discharge chamber 37 and the discharge flow channel piping 62, which will be described later. The same number of connection flow channels 61 as the discharge flow channels 60 are provided. The connection flow channels 61 are provided at intervals in the circumferential direction. In this embodiment, the connection flow channels 61 are formed inside the casing 30. The connection flow channels 61 extend from the pre-discharge chamber 37 toward the other side (upward) in the direction of the axis O. The connection flow channels 61 are inclined so as to be positioned radially outward as they move from one side to the other side (from bottom to top) in the direction of the axis O. When viewed from above, the multiple connection flow channels 61 extend radially outward from the axis O.

[0027] (Discharge Flow Channel Piping) The discharge flow channel piping 62 allows the low-temperature fluid L pumped by the impeller 4 to circumvent the electric motor 50 and flow to the other side (upward) in the direction of the axis O. A plurality of discharge flow channel pipings 62 are provided outside the casing 30 at intervals in the radial direction from the casing 30 and at intervals in the circumferential direction from one another. In this embodiment, the plurality of discharge flow channel pipings 62 are arranged at equal intervals in the circumferential direction, but this is not limited thereto. The circumferential intervals between the discharge flow channel pipings 62 may differ from one another. Furthermore, the discharge flow channel piping 62 in this embodiment extends parallel to the direction of the axis O. In other words, the discharge flow channel piping 62 extends perpendicular to a horizontal plane.

[0028] As shown in FIG. 4 , one end of the discharge flow path piping 62 in the axial direction O (the lower end of the discharge flow path piping 62) is attached to the upper flange 35a of the casing 30. A plurality of first mounting grooves 68 are formed in the upper surface of the upper flange 35a. The first mounting grooves 68 are grooves that open upward. The number of first mounting grooves 68 is the same as the number of discharge flow path piping 62. The plurality of first mounting grooves 68 are provided at equal intervals in the circumferential direction. The end of the discharge flow path piping 62 is inserted into the first mounting grooves 68. The first mounting grooves 68 communicate with the connection flow path 61. The other end of the discharge flow path piping 62 in the axial direction O (the upper end of the discharge flow path piping 62) is attached to the mounting wall 14 of the sump 10. A plurality of second mounting grooves 69 are formed in the lower surface of the mounting wall 14. The second mounting grooves 69 are grooves that open downward. The number of second mounting grooves 69 is the same as the number of discharge flow path piping 62. The plurality of second mounting grooves 69 are provided at equal intervals in the circumferential direction. An end of the discharge flow path piping 62 is inserted into the second mounting grooves 69. The lower end of the discharge flow path piping 62 is mounted in the first mounting groove 68 with a gap in the axial direction O, and the upper end of the discharge flow path piping 62 is mounted in the second mounting groove 69 with a gap in the axial direction O. This allows the discharge flow path piping 62 to slide in the axial direction O.

[0029] (Confluence Flow Channel) The convergence flow channel 63 connects the other ends of the multiple discharge flow channel pipes 62 in the axial line O direction and collects the cryogenic fluid L discharged from each discharge flow channel pipe 62 toward the axial line O. The convergence flow channel 63 has a first flow channel 65, a second flow channel 66, and a third flow channel 67. A plurality of first flow channels 65 are provided in the mounting wall portion 14. The number of first flow channels 65 is the same as the number of discharge pipes. The first flow channels 65 extend from each second mounting groove 69 to the other side (upward) in the axial line O direction. A plurality of first flow channels 65 are provided in the circumferential direction. The second flow channels 66 are formed in the lower surface of the upper flange 13. The second flow channels 66 extend radially inward from each first flow channel 65 toward the axial line O. The third flow channel 67 is formed in the lower surface of the upper flange 13. The third flow channel 67 is formed in a circular shape centered on the axial line O. From another perspective, the second flow paths 66 extend radially outward from the outer circumferential edge of the third flow path 67. The second flow paths 66 connect the third flow path 67 and the first flow paths 65.

[0030] (Discharge Pipe) The discharge pipe 64 extends from the center of the third flow path 67 to the other side (upward) in the direction of the axis O. The discharge pipe 64 discharges the low-temperature fluid L collected by the merging flow path 63 to the outside.

[0031] (Operation of Pump) Next, operation of the pump device 1 will be described. As shown in Fig. 1, when the electric motor 50 is driven, the rotary shaft 21 is driven to rotate, and the impeller 4 and inducer 5 fixed to the rotary shaft 21 rotate. At this time, the radial bearing 41 receives a load on the rotary shaft 21 in a direction perpendicular to the rotary shaft 21 (radial direction). Furthermore, the thrust bearing 43 receives a load on the rotary shaft 21 in the direction of the axis O.

[0032] The cryogenic liquid in the liquid storage chamber 15 is sucked into the suction section 36 by the inducer 5 and is pressurized in stages by the multiple impellers 4. The pressurized cryogenic fluid L is temporarily stored in the pre-discharge chamber 37 between the outer casing 31 and the inner casing 32. The cryogenic fluid L in the pre-discharge chamber 37 is then uniformly distributed in the circumferential direction by the multiple discharge flow path pipes 62 and sent from one side (lower) to the other side (upper) in the direction of the axis O. The cryogenic fluid L is collected at the axis O by the confluence flow path 63 and discharged to the outside of the pump device 1 through the discharge pipe 64.

[0033] (Operations and Effects) The pump device 1 configured as described above can achieve the following operations and effects. In this embodiment, the pump device 1 includes a casing 30, an impeller 4, an electric motor 50, and a discharge flow path piping 62. The casing 30 extends about an axis O and covers the rotating shaft 21, which is rotatable about the axis O. The impeller 4 is provided integrally with the rotating shaft 21 within the casing 30. The impeller 4 rotates together with the rotating shaft 21 to pump the cryogenic fluid L from one side to the other side in the direction of the axis O. The electric motor 50 includes a stator 51 and a rotor 52. The stator 51 is fitted to the inner peripheral surface of the casing 30. The rotor 52 is fixed integrally with the rotating shaft 21 inside the stator 51. A plurality of discharge flow path pipings 62 are provided outside the casing 30 at intervals radially from the casing 30 and at intervals circumferentially from each other. The discharge flow path pipe 62 allows the low-temperature fluid L pressure-fed by the impeller 4 to circulate to the other side in the direction of the axis O so as to bypass the electric motor 50 .

[0034] According to the above configuration, the cryogenic fluid L pumped by the impeller 4 is not discharged to only one location in the circumferential direction, but is discharged via multiple discharge flow path pipes 62. This reduces the radial thrust acting on the rotating shaft. Furthermore, because the discharge flow path pipes 62 are provided at a distance from the casing 30 in the radial direction, the casing 30 is not cooled. This prevents the casing 30 from contracting and applying a compressive load to the stator 51 fitted within the casing 30. Therefore, according to this embodiment, the pump device 1 can appropriately hold the stator 51 of the electric motor 50 while suppressing radial thrust.

[0035] In this embodiment, the pump device 1 includes a confluence flow path 63 that connects the other ends of the plurality of discharge flow path pipes 62 in the direction of the axis O. The confluence flow path 63 collects the cryogenic fluid L discharged from each discharge flow path pipe 62 toward the axis O.

[0036] This suppresses the circumferential deviation of the low-temperature fluid L, and further reduces the radial thrust.

[0037] In this embodiment, the plurality of discharge flow path pipes 62 are arranged at equal intervals in the circumferential direction.

[0038] This further suppresses the circumferential deviation of the low temperature fluid L. Therefore, the radial thrust is further reduced.

[0039] In this embodiment, the discharge flow path pipe 62 is provided so as to be slidable in the axial direction O.

[0040] This allows for a change in the length of the discharge flow path pipe 62 in the direction of the axis O due to thermal contraction, thereby improving the strength of the pump device 1 against thermal changes.

[0041] In this embodiment, the casing 30 has an inner casing 32 and an outer casing 31. The inner casing 32 houses the impeller 4. The outer casing 31 covers the outer periphery of the inner casing 32 and forms a pre-discharge chamber 37 between the outer casing 31 and the inner casing 32. The pre-discharge chamber 37 is filled with the low-temperature fluid L pressurized by the impeller 4.

[0042] Typically, in the case of a single-wall casing, internal pressure tends to open the mating surfaces of the casing. To withstand this pressure and prevent the cryogenic fluid from leaking to the outside or through the surfaces separating the impeller stages, bolts must be evenly arranged around the casing. As the pressure inside the casing increases, the size and number of bolts increase, making it impossible to arrange the bolts properly. In contrast, with the above-described configuration, the cryogenic fluid L pressurized by the impeller 4 is confined in the pre-discharge chamber 37 between the outer casing 31 and the inner casing 32. In this embodiment, the pre-discharge chamber 37 is filled with the cryogenic fluid L pressurized by the final-stage impeller 4. As a result, the pressure of the cryogenic fluid L pressurized by the impeller 4 acts on the inner casing 32 as external pressure (shown by arrow F in FIG. 1 ). This increases the adhesion between the mating surfaces of the inner casing 32 and the surfaces separating the impeller stages, improving sealing performance. Therefore, the number of bolts required to prevent the cryogenic fluid L from leaking due to opening of the mating surfaces of the inner casing 32 or the partition surfaces of each stage of the impeller 4 can be reduced, and the bolt size can be made smaller. Furthermore, the outer casing 31 is formed in a simple cylindrical shape. Therefore, it can withstand the pressure of the cryogenic fluid L filled in the pre-discharge chamber 37. In this way, the casing 30 of this embodiment can withstand pressures that a single-body casing cannot be designed to withstand.

[0043] In this embodiment, the cryogenic fluid L is liquid hydrogen.

[0044] When the cryogenic fluid L is liquid hydrogen, the pump device 1 can appropriately hold the stator 51 of the electric motor 50 while suitably suppressing radial thrust.

[0045] (Other Embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like are also included within the scope of the gist of the present disclosure. Note that in the above embodiment, the discharge flow path piping 62 extends parallel to the axis O. That is, the discharge flow path piping 62 extends perpendicular to the horizontal plane, but this is not limited thereto. For example, as shown in FIG. 5 , the discharge flow path piping 62 may be inclined relative to the axis O so as to be twisted in the rotation direction of the rotating shaft 21. That is, the discharge flow path piping 62 is inclined in the circumferential direction relative to the axis O.

[0046] This reduces pressure loss of the cryogenic fluid L that occurs when the cryogenic fluid L flows through the discharge flow path piping 62. Furthermore, the discharge flow path piping 62 can be installed so as to avoid obstacles, thereby improving layout flexibility. Note that, in the illustrated example, the multiple discharge flow path piping 62 are all inclined at the same inclination angle with respect to the axis O, but the inclination angles of the discharge flow path piping 62 with respect to the axis O may be different from one another.

[0047] <Additional Notes> The pump device 1 described in each embodiment can be understood, for example, as follows.

[0048] (1) The pump device 1 according to the first aspect includes a rotary shaft 21 that extends around an axis O and is rotatable around the axis O; a casing 30 that covers the rotary shaft 21 from the outer periphery; an impeller 4 that is integral with the rotary shaft 21 within the casing 30 and rotates together with the rotary shaft 21 to pump a cryogenic fluid L from one side in the direction of the axis O to the other side; and a pump 4 that is provided on the other side of the impeller 4 in the direction of the axis O within the casing 30. The impeller 4 is provided with a plurality of discharge flow path pipes 62 arranged outside the casing 30 at intervals radially from the casing 30 and at intervals circumferentially from each other, and which allow the low-temperature fluid L pressurized by the impeller 4 to circulate to the other side in the direction of the axis O so as to bypass the motor 50.

[0049] According to the above configuration, the low-temperature fluid L pumped by the impeller 4 is not discharged to only one location in the circumferential direction, but is discharged via multiple discharge flow path pipes 62. This reduces radial thrust. Furthermore, because the discharge flow path pipes 62 are provided at a distance from the casing 30 radially outward, the casing 30 is not cooled. This prevents the casing 30 from contracting and applying a compressive load to the stator 51 fitted within the casing 30. Therefore, according to this aspect, the pump device 1 can appropriately hold the stator 51 of the electric motor 50 while suppressing radial thrust.

[0050] (2) The pump device 1 of the second aspect may be the pump device 1 of (1), and may be provided with a confluence flow path 63 that connects the other ends of the plurality of discharge flow path pipes 62 in the direction of the axis O and collects the low-temperature fluid L discharged from each of the discharge flow path pipes 62 on the axis O.

[0051] This suppresses the circumferential deviation of the low-temperature fluid L, and further reduces the radial thrust.

[0052] (3) The pump device 1 of a third aspect is the pump device 1 of (1) or (2), and the discharge flow path piping 62 may be inclined so as to twist in the rotation direction of the rotating shaft 21 relative to the axis O.

[0053] This reduces the pressure loss of the low-temperature fluid L that occurs when the low-temperature fluid L flows through the discharge flow path piping 62.

[0054] (4) The pump device 1 of the fourth aspect may be any one of the pump devices 1 (1) to (3), in which the discharge flow path piping 62 is arranged to be slidable in the direction of the axis O.

[0055] This allows the length of the discharge flow path pipe 62 to change in the direction of the axis O due to thermal contraction.

[0056] (5) The pump device 1 of the fifth aspect may be any one of the pump devices 1 (1) to (4), in which the casing 30 has an inner casing 32 that houses the impeller 4, and an outer casing 31 that covers the inner casing 32 from the outer periphery and forms a discharge pre-chamber 37 between the inner casing 32 and the outer casing 31 that is filled with the low-temperature fluid L pressurized by the impeller 4.

[0057] According to the above configuration, the low-temperature fluid L pressurized by the impeller 4 is confined in the pre-discharge chamber 37 between the outer casing 31 and the inner casing 32. As a result, the pressure of the low-temperature fluid L pressurized by the impeller 4 acts as external pressure on the inner casing 32. This increases the adhesion force of the mating surfaces of the inner casing 32 and the surfaces separating the stages of the impeller 4, improving sealing performance.

[0058] (6) The pump device 1 of a sixth aspect is the pump device 1 of any one of (1) to (5), in which the cryogenic fluid L may be liquid hydrogen.

[0059] When the cryogenic fluid L is liquid hydrogen, the pump device 1 can appropriately hold the stator 51 of the electric motor 50 while suitably suppressing radial thrust.

[0060] According to the pump device of the present disclosure, the stator of the electric motor can be appropriately held while suppressing radial thrust.

[0061] REFERENCE SIGNS LIST 1 Pump device 2 Supply pipe 3 Gas discharge pipe 4 Impeller 5 Inducer 10 Sump 11 Sump body 12 Peripheral flange 13 Upper flange 14 Mounting wall portion 15 Liquid storage chamber 20 Cryogenic fluid pump 21 Rotating shaft 30 Casing 31 Outer casing 32 Inner casing 33 Motor casing 34 Pump casing 35 Flange portion 35a Upper flange 35b Lower flange 36 Suction portion 37 Pre-discharge chamber 40 Bearing device 41 Radial bearing 41a Upper radial bearing 41b Lower radial bearing 42 Thrust disk 43 Thrust bearing 50 Electric motor 51 Stator 52 Rotor 60 Discharge flow path 61 Connecting flow path 62 Discharge flow path piping 62a End 62b End 63 Merging flow path 64 Discharge pipe 65 First flow path 66 Second flow path 67 Third flow path 68 First mounting groove 69 Second mounting groove L Cryogenic fluid O Axis

Claims

1. A pump device comprising: a rotating shaft extending about an axis and rotatable about said axis; a casing covering the rotating shaft from an outer peripheral side; an impeller provided within said casing integrally with said rotating shaft and rotating together with said rotating shaft to pump a cryogenic fluid from one side to the other in the axial direction; an electric motor provided within said casing on the other side in the axial direction of said impeller and having a stator fitted to the inner peripheral surface of said casing and a rotor fixed integrally to said rotating shaft inside said stator; and a plurality of discharge flow path pipes provided outside said casing at intervals radially from said casing and at intervals circumferentially from each other, for circumferentially distributing the cryogenic fluid pumped by said impeller to the other side in the axial direction so as to bypass said electric motor.

2. The pump device according to claim 1, further comprising a confluence flow path that connects the other axial ends of the plurality of discharge flow path pipes and collects the cryogenic fluid discharged from each of the discharge flow path pipes along the axis.

3. The pump device according to claim 1 or 2, wherein the discharge flow path piping is inclined so as to be twisted in the rotation direction of the rotary shaft relative to the axis.

4. The pump device according to claim 1 or 2, wherein the discharge flow path pipe is provided so as to be slidable in the axial direction.

5. A pump device as described in claim 1 or 2, wherein the casing comprises: an inner casing that houses the impeller; and an outer casing that covers the inner casing from the outer periphery and forms a discharge pre-chamber between the inner casing and the outer casing that is filled with the low-temperature fluid pressurized by the impeller.

6. A pump device according to claim 1 or 2, wherein the cryogenic fluid is liquid hydrogen.

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