Pump device

Abstract

The invention relates to a pump device for boosting liquid hydrogen, in particular to a pump device having a thrust balancing mechanism for counteracting axial thrust applied to an impeller. A pump device is provided with: a rotating shaft (1); a plurality of impellers (2a-2h) fixed to the rotating shaft (1); bearings (5, 6) that rotatably support the rotating shaft (1); a pump housing (7) that houses the plurality of impellers (2a-2h); and a first thrust balancing mechanism (20) and a second thrust balancing mechanism (40) that cancel out the self weight of the rotating body, which is provided with the rotating shaft (1) and the plurality of impellers (2a-2h), and the axial thrust acting on the plurality of impellers (2a-2h).

Description

Technical Field

[0001] The present invention relates to a pump device for increasing the pressure of liquid hydrogen, and more particularly to a pump device having a thrust balancing mechanism for offsetting an axial thrust applied to an impeller. Background Art

[0002] Hydrogen is expected to be an energy source that does not release carbon dioxide, which is a cause of global warming. Examples of hydrogen as an energy source include fuel cells and turbine power generation. Hydrogen is in a gaseous state at room temperature, so in order to store and transport it, hydrogen is cooled and liquefied.

[0003] After being temporarily stored in a storage tank, liquid hydrogen is transported to power plants and factories through a pump device. The pump device is a device used to pressurize liquid hydrogen and transport it to the destination. Usually, a vertical centrifugal pump device is used for this purpose. This type of pump device has a rotating shaft extending in a vertical direction, an impeller fixed to the rotating shaft, and a bearing that rotatably supports the rotating shaft.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-16750

[0007] Patent Document 2: Japanese Patent Application Publication No. 2011-047301 Summary of the invention

[0008] During the operation of the pump device, the pressure on the suction side and the pressure on the discharge side act on the impeller. A shaft thrust equivalent to the difference between the pressure on the suction side and the pressure on the discharge side acts on the rotating shaft, and the shaft thrust is borne by the bearings supporting the rotating shaft. The bearings are immersed in liquid hydrogen and lubricated by liquid hydrogen. However, the viscosity of liquid hydrogen is very low, so the bearings are easily worn. In particular, for vertical pumps, not only the above-mentioned shaft thrust but also the deadweight of the rotating body (including the rotating shaft and the impeller) is applied to the bearings, so the bearings are easily worn, and as a result, the life of the bearings is shortened.

[0009] Therefore, as disclosed in Patent Document 1, in order to offset the above-mentioned shaft thrust applied to the bearing, the pump device may have a thrust balance mechanism. The thrust balance mechanism has a high-pressure chamber filled with a high-pressure fluid and a low-pressure chamber filled with a low-pressure fluid, and is configured to generate an upward force by the pressure difference between the high-pressure fluid and the low-pressure fluid, and the upward force offsets the above-mentioned shaft thrust and the deadweight of the rotating body. Therefore, it is expected that the thrust balance mechanism will set the load applied to the bearing to substantially zero.

[0010] However, compared with other liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG), liquid hydrogen has a lower density and is difficult to be made high-pressure by the rotation of the impeller. Therefore, the upward force caused by the difference between the pressure in the high-pressure chamber and the pressure in the low-pressure chamber cannot be increased. As a result, the upward force generated by the thrust balance mechanism will not be large enough to offset the shaft thrust and the weight of the rotating body, and a large load will be applied to the bearing.

[0011] In addition, liquid hydrogen is easier to vaporize than other liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG). Therefore, when liquid hydrogen moves from the high-pressure chamber to the low-pressure chamber of the thrust balance mechanism, some of the liquid hydrogen may vaporize as the pressure of the liquid hydrogen decreases, forming bubbles. If such bubbles are sucked into the impeller, there is a concern that the pump device will not be able to achieve the pump performance it wants to achieve. In addition, the pump device may sometimes vibrate due to the suction of bubbles.

[0012] Therefore, the present invention provides a pump device that can reduce the load applied to a bearing during a normal operation to substantially zero and prevent the gasification of liquid hydrogen.

[0013] In one embodiment, a pump device is provided for pressurizing liquid hydrogen, wherein the pump device comprises: a rotating shaft; a plurality of impellers fixed to the rotating shaft; a bearing for rotatably supporting the rotating shaft; a pump casing for accommodating the plurality of impellers; and a first thrust balancing mechanism and a second thrust balancing mechanism for offsetting the deadweight of the rotating body and the axial thrust acting on the plurality of impellers, wherein the rotating body includes the rotating shaft and the plurality of impellers, and the second thrust balancing mechanism comprises: a wall structure having a low-pressure chamber and a high-pressure chamber inside; and a partition wall arranged in the wall structure and between the low-pressure chamber and the high-pressure chamber, and the pump device comprises: an intermediate connecting pipeline for connecting the discharge side of an intermediate-stage impeller or a final-stage impeller among the plurality of impellers with the high-pressure chamber; and a reflux pipeline for connecting the discharge side of an intake-side impeller located upstream of the intermediate-stage impeller or the final-stage impeller with the low-pressure chamber.

[0014] In one embodiment, the pump device further includes a check valve that is mounted on the return line and allows only the flow of liquid hydrogen from the low-pressure chamber toward the suction-side impeller.

[0015] In one embodiment, the pump device further comprises: an upstream connecting pipe, which connects the discharge side of the upstream impeller located between the intermediate stage impeller or the final stage impeller and the suction side impeller with the high pressure chamber; and a check valve installed in the upstream connecting pipe, which only allows the flow of liquid hydrogen from the upstream impeller to the high pressure chamber.

[0016] In one embodiment, the first thrust balancing mechanism is arranged on the discharge side of the plurality of impellers, and the second thrust balancing mechanism is arranged on the suction side of the plurality of impellers.

[0017] In one embodiment, the pump device further comprises: an intake container having an intake port for the liquid hydrogen and surrounding the pump housing; and a gas release pipe extending from the wall structure to an upper area within the intake container, wherein the lower end opening of the gas release pipe is located above the low-pressure chamber and opposite to the outer peripheral surface of the rotating shaft.

[0018] In one embodiment, the wall structure has an inner peripheral surface parallel to the axial direction of the rotating shaft, the partition wall has an outer peripheral surface parallel to the axial direction of the rotating shaft, and the entire outer peripheral surface of the partition wall is surrounded by the inner peripheral surface of the wall structure with a gap therebetween.

[0019] In one embodiment, the second thrust balance mechanism further includes a balance chamber located between the low-pressure chamber and the high-pressure chamber, and a variable gap whose size varies depending on the axial position of the rotating shaft is formed between the partition wall and the wall structure.

[0020] In one embodiment, the first thrust balance mechanism and the second thrust balance mechanism are arranged on the discharge side of the plurality of impellers.

[0021] In one embodiment, the first thrust balancing mechanism comprises: a first wall structure having a first low-pressure chamber, a first balance chamber and a first high-pressure chamber therein; and the first partition wall arranged in the first wall structure and between the first low-pressure chamber and the first balance chamber, wherein a variable gap whose size varies with the axial position of the rotating shaft is formed between the first partition wall and the rotating body, wherein the rotating body includes the rotating shaft and the plurality of impellers.

[0022] In one embodiment, the first thrust balancing mechanism comprises: a first wall structure having a first low-pressure chamber and a first high-pressure chamber therein; and a first partition wall arranged in the first wall structure and between the first low-pressure chamber and the first high-pressure chamber, wherein a radial gap of a size that does not vary according to the axial position of the rotating shaft is formed between an outer peripheral surface of the first partition wall and an inner peripheral surface of the first wall structure.

[0023] In one embodiment, a pump device is provided for increasing the pressure of liquid hydrogen, wherein the pump device comprises: a rotating shaft; a plurality of impellers fixed to the rotating shaft; a bearing for rotatably supporting the rotating shaft; a pump housing for accommodating the plurality of impellers; an intake container having an intake port for the liquid hydrogen and surrounding the pump housing; a gas release pipeline; and a thrust balancing mechanism for offsetting the deadweight of the rotating body and the axial thrust acting on the plurality of impellers, wherein the rotating body includes the rotating shaft and the plurality of impellers, and the thrust balancing mechanism comprises: a wall structure having a low-pressure chamber and a high-pressure chamber therein; and a partition wall arranged in the wall structure and between the low-pressure chamber and the high-pressure chamber, the gas release pipeline extending from the wall structure to an upper area in the intake container, and the lower end of the gas release pipeline being connected to the low-pressure chamber.

[0024] Effects of the Invention

[0025] According to the present invention, a force sufficient to offset the rotating body (including the rotating shaft and the impeller) and the shaft thrust can be generated by the first thrust balancing mechanism and the second thrust balancing mechanism. Therefore, the load applied to the bearing supporting the rotating shaft can be substantially set to 0. In addition, according to the present invention, the low-pressure chamber of the second thrust balancing mechanism is connected to the discharge side of the suction side impeller through a return line, so that the generation of bubbles can be prevented when the liquid hydrogen moves from the high-pressure chamber to the low-pressure chamber. Therefore, bubbles will not be sucked into the impeller, the pump device can exert its desired pump performance, and vibration caused by the suction of bubbles can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a cross-sectional view showing one embodiment of the pump device.

[0027] Figure 2 It is an enlarged cross-sectional view showing one embodiment of the first thrust balancing mechanism.

[0028] Figure 3 This is an enlarged cross-sectional view of the first thrust balance mechanism when the downward shaft thrust increases.

[0029] Figure 4 It is an enlarged cross-sectional view showing one embodiment of the second thrust balancing mechanism.

[0030] Figure 5 It is an enlarged cross-sectional view showing another embodiment of the pump device.

[0031] Figure 6 It is an enlarged cross-sectional view showing still another embodiment of the pump device.

[0032] Figure 7 It is an enlarged cross-sectional view showing still another embodiment of the pump device.

[0033] Figure 8 It is an enlarged cross-sectional view showing another embodiment of the second thrust balancing mechanism.

[0034] Fig. 9 It is an enlarged cross-sectional view showing another embodiment of the first thrust balancing mechanism.

[0035] Fig.10 It is an enlarged cross-sectional view showing still another embodiment of the first thrust balance mechanism.

[0036] Fig.11 It is an enlarged cross-sectional view showing still another embodiment of the first thrust balance mechanism.

[0037] Fig.12 It is an enlarged cross-sectional view showing still another embodiment of the first thrust balance mechanism.

[0038] Fig.13 It is an enlarged cross-sectional view showing still another embodiment of the first thrust balance mechanism.

[0039] Fig.14 It is an enlarged cross-sectional view showing still another embodiment of the first thrust balance mechanism.

[0040] Fig.15 It is a cross-sectional view showing still another embodiment of the pump device.

[0041] Fig.16 Yes means Fig.15 An enlarged cross-sectional view of one embodiment of the second thrust balancing mechanism shown.

[0042] Fig.17 It is an enlarged cross-sectional view showing still another embodiment of the pump device.

[0043] Fig.18 Yes means Fig.17 An enlarged cross-sectional view of one embodiment of the second thrust balancing mechanism shown.

[0044] Fig.19 It is an enlarged cross-sectional view showing still another embodiment of the pump device.

[0045] Fig. 20 It is an enlarged cross-sectional view showing still another embodiment of the pump device. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0047] Figure 1 2 is a cross-sectional view showing an embodiment of a pump device. The pump device of this embodiment described below is a centrifugal pump device used for increasing the pressure of liquid hydrogen.

[0048] like Figure 1 As shown, the pump device has a rotating shaft 1, a plurality of impellers 2a to 2h fixed to the rotating shaft 1, bearings 5 ​​and 6 for rotatably supporting the rotating shaft 1, and a pump housing 7 for accommodating the impellers 2a to 2h. The rotating shaft 1 extends in a vertical direction, and the plurality of impellers 2a to 2h are fixed to the rotating shaft 1. A pump device having a rotating shaft 1 extending in a vertical direction is also called a vertical pump device. The plurality of impellers 2a to 2h face the same direction (downward in this embodiment) and are arranged in series along the rotating shaft 1. The number of impellers 2a to 2h is not limited to this embodiment.

[0049] The pump device further includes a motor 10 connected to the rotating shaft 1 . The motor 10 includes a motor rotor 10A fixed to the rotating shaft 1 , a motor stator 10B surrounding the motor rotor 10A, and a motor housing 10C accommodating the motor stator 10B. The motor housing 10C is fixed to the pump case 7 .

[0050] The motor 10 is configured to rotate the rotating shaft 1 and the impellers 2a to 2h as a whole. In the present embodiment, the motor 10 is an immersed motor that can be in contact with liquid hydrogen. That is, during the operation of the pump device, the motor rotor 10A and the motor stator 10B are immersed in liquid hydrogen and cooled by the liquid hydrogen. In one embodiment, at least one of the motor rotor 10A and the motor stator 10B may also have a sealed structure that does not allow liquid to flow in.

[0051] The pump device has an intake container 12 that surrounds the pump housing 7 and the motor 10. The intake container 12 is arranged longitudinally. The intake container 12 has an intake port 15 for liquid hydrogen. The intake port 15 is provided on the side of the intake container 12. In one embodiment, the intake port 15 may also be provided on the upper surface or the bottom surface of the intake container 12. Liquid hydrogen is introduced into the intake container 12 through the intake port 15. During the operation of the pump device, the interior of the intake container 12 is filled with liquid hydrogen. Therefore, the pump housing 7 and the motor 10 are immersed in liquid hydrogen as a whole.

[0052] The bearings 5 ​​and 6 are arranged on the upper side and the lower side of the motor 10. In the present embodiment, the bearings 5 ​​and 6 use ball bearings that can support both radial loads and axial loads. In one embodiment, the bearings 5 ​​and 6 may also be sliding bearings. During the operation of the pump device, the bearings 5 ​​and 6 are immersed in liquid hydrogen and are lubricated and cooled by the liquid hydrogen.

[0053] The pump housing 7 has an inlet 7a for liquid hydrogen. When the motor 10 rotates the impellers 2a to 2h, the liquid hydrogen sucked into the container 12 flows into the pump housing 7 through the inlet 7a. The liquid hydrogen is pressurized in the pump housing 7 as the impellers 2a to 2h rotate. The pressurized liquid hydrogen passes through the discharge flow path 16 and the outlet 17 and is discharged from the pump device. The discharge flow path 16 is formed in the pump housing 7 and the motor housing 10C, and the outlet 17 is formed in the motor housing 10C. A portion of the pressurized liquid hydrogen contacts the bearings 5, 6 and the motor 10 as described above.

[0054] The pump device further has a first thrust balance mechanism 20 and a second thrust balance mechanism 40 for offsetting the deadweight of the rotating body and the axial thrust acting on the plurality of impellers 2a to 2h, wherein the rotating body includes at least a rotating shaft 1 and a plurality of impellers 2a to 2h. The first thrust balance mechanism 20 is arranged on the discharge side of the plurality of impellers 2a to 2h. More specifically, the first thrust balance mechanism 20 is arranged between the final stage impeller 2h and the motor 10. A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h flows in the first thrust balance mechanism 20, further contacts the bearings 5, 6 and the motor 10, and cools the bearings 5, 6 and the motor 10. The liquid hydrogen passes through the connecting pipe 21 and returns to the low-pressure side of the pump housing 7.

[0055] One end of the communication line 21 is connected to the motor housing 10C of the electric motor 10 and communicates with the inside of the motor housing 10C. The other end of the communication line 21 is connected to the pump housing 7 and communicates with the low-pressure side area in the pump housing 7. More specifically, the other end of the communication line 21 communicates with the inside of the pump housing 7 at a position between the first-stage impeller 2a and the final-stage impeller 2h. Therefore, the communication line 21 communicates with the discharge side of any one of the impellers 2a to 2h.

[0056] The connection position of the communication conduit 21 and the pump housing 7 is appropriately determined based on the self-weight of the rotating body (including the rotating shaft 1 and the impellers 2a to 2h) and other factors. In the present embodiment, if the plurality of impellers 2a to 2h are divided into impellers 2a to 2d of a low-pressure side group including the first-stage impeller 2a and impellers 2e to 2h of a high-pressure side group including the final-stage impeller 2h, the communication conduit 21 is connected to the inside of the pump housing 7 at the position of the low-pressure side group.

[0057] The liquid hydrogen in the motor housing 10C passes through the connecting pipe 21 and returns to the pump housing 7. Therefore, the pressure of the liquid hydrogen in the motor housing 10C is substantially the same as the pressure on the low-pressure side of the pump housing 7. In the present embodiment, the connecting pipe 21 is connected to the inside of the pump housing 7 at the position of the second-stage impeller 2b (that is, connected to the discharge side of the impeller 2b), but the connecting pipe 21 may be connected to the inside of the pump housing 7 at the position of other-stage impellers.

[0058] In one embodiment, the communication line 21 may be connected to the interior of the suction container 12 instead of being connected to the pump housing 7. In this case, the pressure of the liquid hydrogen in the motor housing 10C is substantially the same as the pressure on the suction side of the impeller 2a (that is, the pressure before being boosted by the impellers 2a to 2h).

[0059] Figure 2 FIG. 2 is an enlarged view of the first thrust balancing mechanism 20. Figure 2 As shown, the first thrust balancing mechanism 20 includes: a first wall structure 26 having a first low-pressure chamber 23, a first balancing chamber 24, and a first high-pressure chamber 25 therein; and a first partition wall 30 disposed in the first wall structure 26 and disposed between the first low-pressure chamber 23 and the first balancing chamber 24. The names of the first low-pressure chamber 23 and the first high-pressure chamber 25 mean that the pressure in the first low-pressure chamber 23 is lower than the pressure in the first high-pressure chamber 25, and do not mean that the pressure in the first low-pressure chamber 23 is below a specific pressure and the pressure in the first high-pressure chamber 25 is above a specific pressure.

[0060] The first low-pressure chamber 23, the first balance chamber 24, and the first high-pressure chamber 25 are located on the back side of the final-stage impeller 2h. The first partition wall 30 is disposed between the first low-pressure chamber 23 and the first balance chamber 24. The bearing 5 is disposed in the first low-pressure chamber 23. The first high-pressure chamber 25 and the first balance chamber 24 face the back side of the final-stage impeller 2h. An axial gap C1 is formed between the first partition wall 30 and the rotating body (including the rotating shaft 1 and the impellers 2a to 2h).

[0061] In the present embodiment, the first partition wall 30 is fixed to the first wall structure 26. The first partition wall 30 has a stationary surface 31 inclined relative to the axial direction of the rotating shaft 1, and has a movable surface 32 parallel to the stationary surface 31 on the back side of the final stage impeller 2h as a part of the rotating body. In the present embodiment, the stationary surface 31 and the movable surface 32 are perpendicular to the axial direction of the rotating shaft 1. In one embodiment, the stationary surface 31 and the movable surface 32 may not be perpendicular to the axial direction of the rotating shaft 1 as long as they are inclined relative to the axial direction of the rotating shaft 1.

[0062] A variable gap C1 whose size changes with the movement of the rotary shaft 1 in the axial direction is formed between the stationary surface 31 of the first partition wall 30 and the movable surface 32 of the final-stage impeller 2 h. Figure 2 The first thrust balance mechanism 20 shown is a variable gap type in which the size of the axial gap C1 varies according to the axial position of the rotating shaft 1. Such a variable gap type is also called a variable flow type.

[0063] In one embodiment, the first partition wall 30 is fixed to a rotating body (e.g., the rotating shaft 1 or the final stage impeller 2h), and the first partition wall 30 may also be configured to rotate integrally with the rotating shaft 1. In this case, the first partition wall 30 has a movable surface inclined relative to the axial direction of the rotating shaft 1, and the first wall structure 26 has a stationary surface parallel to the movable surface. Between the movable surface of the first partition wall 30 and the stationary surface of the first wall structure 26, an axial variable gap whose size changes with the axial movement of the rotating shaft 1 is formed.

[0064] exist Figure 2 In the embodiment shown, a portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h including the final-stage impeller 2h flows to the front surface of the final-stage impeller 2h and the first high-pressure chamber 25. The liquid hydrogen in the first high-pressure chamber 25 further flows into the first balance chamber 24. If the rotating shaft 1 and the impellers 2a to 2h move upward, the axial gap C1 between the first partition wall 30 and the final-stage impeller 2h becomes smaller. As a result, the pressure in the first balance chamber 24 rises. A downward force equivalent to the difference between the pressure of the liquid hydrogen in the first balance chamber 24 and the first high-pressure chamber 25 and the pressure applied to the front surface of the final-stage impeller 2h acts on the final-stage impeller 2h.

[0065] On the other hand, if the rotating shaft 1 and the impellers 2a to 2h move downward, Figure 3 As shown, the axial gap C1 becomes larger, and as a result, the pressure in the first balance chamber 24 decreases. An upward force corresponding to the difference between the pressure of the liquid hydrogen in the first balance chamber 24 and the first high-pressure chamber 25 and the pressure applied to the front surface of the final-stage impeller 2h acts on the final-stage impeller 2h. In this way, the first thrust balance mechanism 20 can generate an upward force that resists the dead weight of the rotating body (including at least the rotating shaft 1 and the plurality of impellers 2a to 2h) and the downward axial thrust acting on the plurality of impellers 2a to 2h.

[0066] Liquid hydrogen has a very low density compared to other liquids such as water. Therefore, the upward force generated by the first thrust balance mechanism 20 may not be able to offset the deadweight of the rotating body and the downward axial thrust.

[0067] Therefore, if Figure 1 As shown in FIG. 1 , the pump device of this embodiment further includes a second thrust balance mechanism 40 in addition to the first thrust balance mechanism 20. Figure 1 In the illustrated embodiment, the second thrust balance mechanism 40 is disposed on the suction side of all the impellers 2a to 2h (that is, below the impellers 2a to 2h). Furthermore, the second thrust balance mechanism 40 is disposed outside the pump housing 7. More specifically, the second thrust balance mechanism 40 is disposed below the inlet 7a of the pump housing 7.

[0068] The second thrust balance mechanism 40 is connected to the inside of the pump casing 7 through the intermediate communication conduit 41 and the return conduit 80. One ends of the intermediate communication conduit 41 and the return conduit 80 are connected to the second thrust balance mechanism 40. The other ends of the intermediate communication conduit 41 and the return conduit 80 are connected to the pump casing 7 and communicate with the inside of the pump casing 7. More specifically, the other end of the intermediate communication conduit 41 is connected to the pump casing 7 at a position on the discharge side of the intermediate stage impeller 2d among the plurality of impellers 2a to 2h, and communicates with the inside of the pump casing 7. The other end of the return conduit 80 is connected to the pump casing 7 at a position between the suction side of the intermediate stage impeller 2d and the discharge side of the first stage impeller 2a as the suction side impeller, and communicates with the inside of the pump casing 7. In the present embodiment, the other end of the return conduit 80 is connected to the discharge side of the first stage impeller 2a as the suction side impeller located upstream of the intermediate stage impeller 2d.

[0069] The second thrust balancing mechanism 40 is surrounded by the suction container 12, and the second thrust balancing mechanism 40 is immersed in the liquid hydrogen in the suction container 12. In this embodiment, the entire second thrust balancing mechanism 40 is surrounded by the suction container 12, but in one embodiment, a portion of the second thrust balancing mechanism 40 may be surrounded by the suction container 12, and the other portion may be located outside the suction container 12.

[0070] Figure 4 FIG. 4 is an enlarged cross-sectional view showing an embodiment of the second thrust balancing mechanism 40. Figure 4 As shown, the second thrust balance mechanism 40 has a second wall structure 46 having a second low-pressure chamber 43 and a second high-pressure chamber 45 therein, and a second partition wall 50 disposed in the second wall structure 46 and disposed between the second low-pressure chamber 43 and the second high-pressure chamber 45. The second partition wall 50 is connected to the rotating shaft 1. The second high-pressure chamber 45 is located below the second low-pressure chamber 43. The names of the second low-pressure chamber 43 and the second high-pressure chamber 45 mean that the pressure in the second low-pressure chamber 43 is lower than the pressure in the second high-pressure chamber 45, and do not mean that the pressure in the second low-pressure chamber 43 is below a specific pressure and the pressure in the second high-pressure chamber 45 is above a specific pressure.

[0071] One end of the intermediate communication conduit 41 is connected to the second wall structure 46 and communicates with the second high-pressure chamber 45. The other end of the intermediate communication conduit 41 is communicated with the discharge side of one of the multiple impellers 2a to 2h. More specifically, the other end of the intermediate communication conduit 41 is connected to the pump casing 7 at the position of the discharge side of one of the multiple impellers 2a to 2h, and communicates with the interior of the pump casing 7. In this embodiment, the second high-pressure chamber 45 is communicated with the discharge side of the intermediate stage impeller 2d through the intermediate communication conduit 41. That is, the other end of the intermediate communication conduit 41 is communicated with the interior of the pump casing 7 at the position of the discharge side of the impeller 2d. In one embodiment, the other end of the intermediate communication conduit 41 can also be connected to the discharge side of the other stage impellers as an intermediate stage impeller.

[0072] One end of the return line 80 is connected to the second wall structure 46 and communicates with the second low-pressure chamber 43. The other end of the return line 80 is connected to the pump housing 7 at the discharge side of the first-stage impeller 2a, which is the suction-side impeller located upstream of the intermediate-stage impeller 2d, and communicates with the inside of the pump housing 7. Therefore, the return line 80 allows the discharge side of the first-stage impeller 2a, which is the suction-side impeller, to communicate with the second low-pressure chamber 43. In one embodiment, the suction-side impeller may be an impeller other than the first-stage impeller 2a (for example, the second-stage impeller 2b) as long as it is located upstream of the intermediate-stage impeller 2d.

[0073] The second partition wall 50 has a piston shape and is fixed to the lower end of the rotating shaft 1. The second partition wall 50 rotates integrally with the rotating shaft 1 in the second wall structure 46 and can move in the axial direction integrally with the rotating shaft 1. The second wall structure 46 has an inner peripheral surface 52 parallel to the axial direction of the rotating shaft 1, and the second partition wall 50 has an outer peripheral surface 53 parallel to the axial direction of the rotating shaft 1. The entire outer peripheral surface 53 of the second partition wall 50 is surrounded by the inner peripheral surface 52 of the second wall structure 46 via a gap C2. The second partition wall 50 can move in the axial direction in the second wall structure 46 along with the axial movement of the rotating shaft 1.

[0074] There is a radial gap C2 between the outer peripheral surface 53 of the second partition wall 50 and the inner peripheral surface 52 of the second wall structure 46. The size of the radial gap C2 is fixed regardless of the axial position of the rotating shaft 1. The second thrust balance mechanism 40 of this embodiment is a fixed gap type in which the size of the radial gap C2 does not change regardless of the axial position of the rotating shaft 1. This fixed gap type is also called a fixed flow type.

[0075] The liquid hydrogen filling the second high-pressure chamber 45 passes through the radial gap C2 and moves to the second low-pressure chamber 43. The liquid hydrogen flows from the second low-pressure chamber 43 into the pump housing 7 through the return line 80. In order to control the flow rate of the liquid hydrogen passing through the radial gap C2, a groove (axial groove, spiral groove, circumferential groove, etc.) may be provided on at least one of the inner peripheral surface 52 and the outer peripheral surface 53.

[0076] The pressure in the second low-pressure chamber 43 is substantially equal to the pressure on the discharge side of the impeller 2a. Therefore, the second partition wall 50 receives an upward force equivalent to the difference between the pressure in the second high-pressure chamber 45 and the pressure in the second low-pressure chamber 43. This upward force is a force generated by the second thrust balance mechanism 40, and is a force resisting the deadweight of the rotating body (including at least the rotating shaft 1 and the impellers 2a to 2h) and the axial thrust acting on the impellers 2a to 2h. The upward force generated by the second thrust balance mechanism 40 is determined by the difference between the pressure in the second high-pressure chamber 45 and the pressure in the second low-pressure chamber 43, and does not change according to the axial position of the rotating shaft 1.

[0077] The combination of the upward force generated by the first thrust balance mechanism 20 and the upward force generated by the second thrust balance mechanism 40 can offset the deadweight of the rotating body (including at least the rotating shaft 1 and the impellers 2a to 2h) and the axial thrust acting on the impellers 2a to 2h. Therefore, the axial thrust acting on the bearings 5 ​​and 6 is substantially zero, and the life of the bearings 5 ​​and 6 is extended.

[0078] The return line 80 connects the discharge side of the first-stage impeller 2a, which is the suction-side impeller, to the second low-pressure chamber 43. Therefore, during the operation of the pump device, the pressure in the second low-pressure chamber 43 is substantially the same as the discharge side of the first-stage impeller 2a. In other words, the pressure in the second low-pressure chamber 43 is substantially the same as the pressure boosted by the first-stage impeller 2a. When liquid hydrogen moves from the second high-pressure chamber 45 to the second low-pressure chamber 43 through the radial gap C2, the pressure of the liquid hydrogen decreases, but the pressure in the second low-pressure chamber 43 is substantially the same as the pressure boosted by the first-stage impeller 2a, so the liquid hydrogen is difficult to gasify. The liquid hydrogen returned to the pump housing 7 from the second low-pressure chamber 43 through the return line 80 does not contain bubbles, so the pump device can exert its intended pump performance and can prevent vibration caused by the suction of bubbles.

[0079] When the liquid hydrogen that fills the second high-pressure chamber 45 moves to the second low-pressure chamber 43 through the gap C2, the liquid hydrogen forms a liquid film in the gap C2. The liquid film functions as a bearing that supports the rotating body including the rotating shaft 1 and the multiple impellers 2a~2h, and thus helps to improve the stability of the rotating body. In particular, the bearing function of the second thrust balance mechanism 40 is beneficial to a multi-stage pump device having multiple impellers. In other words, the axial length of the multi-stage pump device having multiple impellers becomes longer, and the vortex elements increase, thereby sometimes causing the stability of the rotating body including the multiple impellers to become a problem. The liquid film formed in the gap C2 can improve the stability of such a rotating body.

[0080] The density of liquid hydrogen is about one sixth of that of liquefied natural gas. When the pump device processes such liquid hydrogen, it is difficult to generate sufficient upward force for supporting the rotating body only by the first thrust balance mechanism 20. According to the present embodiment, the first thrust balance mechanism 20 and the second thrust balance mechanism 40 can generate an upward force of a sufficient size for supporting the deadweight of the rotating body and the axial thrust. In particular, by appropriately setting the connection position of the intermediate connecting pipe 41 and the pump housing 7, the second thrust balance mechanism 40 can generate the optimal upward force.

[0081] The second thrust balance mechanism 40 forms a circulation of liquid hydrogen completely independent of the first thrust balance mechanism 20. That is, the pressure in the second high-pressure chamber 45 of the second thrust balance mechanism 40 is equivalent to the pressure on the discharge side of the intermediate stage impeller among the plurality of impellers 2a to 2h. The pressure in the second high-pressure chamber 45 changes according to the connection position of the intermediate communication conduit 41 and the pump housing 7. Therefore, the appropriate connection position of the intermediate communication conduit 41 and the pump housing 7 is determined based on the upward force required to offset the self-weight of the rotating body and the axial thrust acting on the impellers 2a to 2h.

[0082] like Figure 4 As shown in FIG. 1 , a sliding bearing 55 may be provided above the second thrust balancing mechanism 40. Figure 4 In the illustrated embodiment, the sliding bearing 55 is located above the second thrust balance mechanism 40 and below the impellers 2a to 2h.

[0083] In this embodiment, the intermediate communication conduit 41 is communicated with the discharge side of the impeller 2d as an example of the intermediate stage impeller, but in order to generate the necessary upward force, the intermediate communication conduit 41 may be communicated with the discharge side of other impellers (for example, the third stage impeller 2c, the fourth stage impeller 2e, or the final stage impeller 2h) as the intermediate stage impeller. The return conduit 80 is communicated with the discharge side of the first stage impeller 2a as the suction side impeller located upstream of the intermediate stage impeller 2d, but in one embodiment, the return conduit 80 may be communicated with the discharge side of other impellers (for example, the second stage impeller 2b) located upstream of the intermediate stage impeller 2d.

[0084] Figure 5 FIG. 1 is an enlarged cross-sectional view showing another embodiment of the pump device. The structure and operation of this embodiment not specifically described are similar to those of the reference Figures 1 to 4 The embodiments described are the same, so the repeated description is omitted. Figure 5 As shown, in this embodiment, the pump device further includes a check valve 85 attached to the return line 80. The check valve 85 is configured to allow only the flow of liquid hydrogen from the second low-pressure chamber 43 toward the discharge side of the first-stage impeller 2a.

[0085] The check valve 85 functions when the pump device is started. That is, the check valve 85 prevents liquid hydrogen from flowing from the discharge side of the first-stage impeller 2a, which is the suction-side impeller, to the second low-pressure chamber 43 immediately after the pump device is started and the pressure in the second high-pressure chamber 45 is low. Therefore, the check valve 85 can prevent the second thrust balance mechanism 40 from generating a temporary downward axial thrust immediately after the pump device is started.

[0086] Figure 6 FIG. 1 is an enlarged cross-sectional view showing another embodiment of the pump device. The structure and operation of this embodiment not specifically described are similar to those of FIG. Figure 5 The embodiments described are the same, so the repeated description is omitted. Figure 6 As shown, the pump device further includes an upstream communication conduit 90 that connects the discharge side of the second-stage impeller 2b, which is an upstream impeller, with the second high-pressure chamber 45, and a check valve 91 installed in the upstream communication conduit 90. The check valve 91 is configured to allow only the flow of liquid hydrogen from the discharge side of the impeller 2b toward the second high-pressure chamber 45.

[0087] One end of the upstream communication conduit 90 is connected to the pump housing 7 at the discharge side of the second-stage impeller 2b as the upstream impeller, and is communicated with the inside of the pump housing 7. The upstream impeller is an impeller located between the first-stage impeller 2a as the suction-side impeller and the impeller 2d as the intermediate-stage impeller. In the present embodiment, the upstream impeller is the second-stage impeller 2b, but it may be another impeller (for example, the third-stage impeller 2c) as long as it is located between the suction-side impeller and the intermediate-stage impeller. The other end of the upstream communication conduit 90 is connected to the second wall structure 46, and is communicated with the second high-pressure chamber 45.

[0088] The upstream connecting conduit 90 functions when the pump device is started. That is, immediately after the pump device is started, the first thrust balance mechanism 20 and the second thrust balance mechanism 40 cannot generate sufficient upward force. The liquid hydrogen is first pressurized by the rotation of the first-stage impeller 2a, and then pressurized by the rotation of the second-stage impeller 2b. A portion of the pressurized liquid hydrogen passes through the upstream connecting conduit 90 and flows into the second high-pressure chamber 45. Therefore, a pressure difference is generated between the second low-pressure chamber 43 and the second high-pressure chamber 45, and the pressure difference causes an upward force to be generated.

[0089] Thus, according to the present embodiment, the second thrust balance mechanism 40 can generate an upward force from the early operation stage before the normal operation of the pump device. Figure 1 ) load is reduced, which can extend the life of bearings 5 ​​and 6.

[0090] If the liquid hydrogen is pressurized by the rotation of the intermediate-stage impeller 2d, a portion of the pressurized liquid hydrogen passes through the intermediate communication pipe 41 and flows into the second high-pressure chamber 45. The pressure in the second high-pressure chamber 45 is higher than the pressure on the discharge side of the second-stage impeller 2b, so the check valve 91 is operated to prevent the liquid hydrogen from flowing back from the second high-pressure chamber 45 to the second-stage impeller 2b.

[0091] exist Figure 6 In the illustrated embodiment, the intermediate communication pipeline 41 and the upstream communication pipeline 90 are two independent pipelines that do not intersect each other, but in one embodiment, the intermediate communication pipeline 41 may be combined with a portion of the upstream communication pipeline 90 to form a collective pipeline.

[0092] exist Figures 4 to 6 In the embodiment shown, the intermediate communication conduit 41 extending to the second high pressure chamber 45 is arranged outside the pump housing 7 and the second wall structure 46. In one embodiment, as Figure 7 As shown, the intermediate communication pipe 41 can also extend through the interior of the rotating shaft 1. Figure 7 In the illustrated embodiment, one end of the intermediate communication conduit 41 communicates with the discharge side of the intermediate-stage impeller 2 d , and the other end of the intermediate communication conduit 41 communicates with the second high-pressure chamber 45 .

[0093] according to Figure 7 In the structure shown, a part of the liquid hydrogen pressurized by the rotation of the impellers 2a to 2d flows into the second high-pressure chamber 45 through the intermediate communication conduit 41 in the rotating shaft 1. An additional pipe as the intermediate communication conduit 41 is unnecessary.

[0094] Figure 8 FIG. 4 is an enlarged cross-sectional view showing another embodiment of the second thrust balancing mechanism 40. The structure of this embodiment which is not particularly described is different from the structure of the second thrust balancing mechanism 40. Figure 4The structure shown in FIG. 1 is the same as that shown in FIG. 1 , so the repeated description is omitted. Figure 8 As shown, the second thrust balance mechanism 40 further includes a second balance chamber 44 located between the second low-pressure chamber 43 and the second high-pressure chamber 45. The second partition wall 50 includes a movable surface 57 inclined relative to the axial direction of the rotating shaft 1, and the second wall structure 46 includes a stationary surface 58 parallel to the movable surface 57. In this embodiment, the movable surface 57 and the stationary surface 58 are perpendicular to the axial direction of the rotating shaft 1. In one embodiment, the movable surface 57 and the stationary surface 58 may not be perpendicular to the axial direction of the rotating shaft 1 as long as they are inclined relative to the axial direction of the rotating shaft 1.

[0095] The movable surface 57 is located above the stationary surface 58. The second partition wall 50 can move in the axial direction together with the rotating shaft 1, so the size of the axial gap C3 between the movable surface 57 and the stationary surface 58 changes with the axial movement of the rotating shaft 1 and the second partition wall 50. In other words, the axial gap C3 is a variable gap whose size changes with the axial position of the rotating shaft 1. This variable gap type is also called a variable flow type.

[0096] The liquid hydrogen flowing into the second high-pressure chamber 45 through the intermediate connecting pipe 41 flows into the second balance chamber 44, filling the second balance chamber 44. Furthermore, the liquid hydrogen in the second balance chamber 44 moves from the axial gap C3 to the second low-pressure chamber 43. When the rotating shaft 1 moves downward, the axial gap C3 becomes smaller and the pressure in the second balance chamber 44 rises. As a result, the second thrust balance mechanism 40 generates a larger upward force, and the rotating shaft 1 rises. When the rotating shaft 1 moves upward, the axial gap C3 becomes larger, and the pressure in the second balance chamber 44 decreases. As a result, the force generated by the second thrust balance mechanism 40 decreases, and the rotating shaft 1 moves downward. In this way, the second thrust balance mechanism 40 can generate an upward force that changes with the axial movement of the rotating shaft 1. According to this embodiment, when the liquid hydrogen filling the second high-pressure chamber 45 moves to the second low-pressure chamber 43, the liquid hydrogen forms a liquid film in the gap between the second partition wall 50 and the second wall structure 46. This liquid film functions as a bearing for supporting a rotating body including the rotating shaft 1 and the plurality of impellers 2a to 2h, and thus contributes to improving the stability of the rotating body.

[0097] Reference Figures 5 to 7 The described embodiments may also be applied to Figure 8 Description of the embodiment.

[0098] Figure 8 The second thrust balance mechanism 40 shown is a variable gap type having an axial gap C3 whose size varies according to the axial position of the rotating shaft 1. When such a variable gap type second thrust balance mechanism 40 is adopted, the first thrust balance mechanism 20 may also be a reference Fig. 9The fixed gap type is described below.

[0099] Fig. 9 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balancing mechanism 20. Fig. 9 As shown, the first thrust balance mechanism 20 includes a first wall structure 26 having a first low-pressure chamber 23 and a first high-pressure chamber 25 therein, and a first partition wall 30 disposed in the first wall structure 26 and disposed between the first low-pressure chamber 23 and the first high-pressure chamber 25. The first high-pressure chamber 25 is located below the first low-pressure chamber 23. The structure of this embodiment and the reference numerals not specifically described are as follows: Figures 1 to 3 The described implementation modes are the same, so repeated descriptions thereof are omitted.

[0100] The first low-pressure chamber 23 is communicated with the low-pressure side of the pump housing 7 through the communication line 21 (see Figure 1 ). Therefore, the pressure in the first low-pressure chamber 23 is substantially the same as the pressure on the low-pressure side of the pump housing 7. In one embodiment, the communication line 21 may be connected to the interior of the suction container 12 instead of being connected to the pump housing 7. In this case, the pressure in the first low-pressure chamber 23 is substantially the same as the pressure on the suction side of the impeller 2a (that is, the pressure before being boosted by the impellers 2a to 2h).

[0101] The first high-pressure chamber 25 is located on the discharge side of the final-stage impeller 2h. The first partition wall 30 has a piston shape and is fixed to the rotating shaft 1. The first partition wall 30 rotates integrally with the rotating shaft 1 in the first wall structure 26 and can move axially integrally with the rotating shaft 1. The first wall structure 26 has an inner peripheral surface 61 parallel to the axial direction of the rotating shaft 1, and the first partition wall 30 has an outer peripheral surface 62 parallel to the axial direction of the rotating shaft 1. The entire outer peripheral surface 62 of the first partition wall 30 is surrounded by the inner peripheral surface 61 of the first wall structure 26 with a gap C4. Therefore, the first partition wall 30 can move axially in the first wall structure 26 along with the axial movement of the rotating shaft 1.

[0102] There is a radial gap C4 between the outer peripheral surface 62 of the first partition wall 30 and the inner peripheral surface 61 of the first wall structure 26. The size of the radial gap C4 is fixed regardless of the axial position of the rotating shaft 1. The first thrust balance mechanism 20 of the present embodiment is a fixed gap type in which the size of the radial gap C4 does not change depending on the axial position of the rotating shaft 1. This fixed gap type is also called a fixed flow type.

[0103] A portion of the liquid hydrogen pressurized by the rotation of the impellers 2a to 2h flows into the first high-pressure chamber 25. The liquid hydrogen filling the first high-pressure chamber 25 passes through the gap C4 between the outer peripheral surface 62 of the first partition wall 30 and the inner peripheral surface 61 of the first wall structure 26 and moves to the first low-pressure chamber 23. The pressure in the first low-pressure chamber 23 is substantially equal to the pressure in the pump housing 7 at the connection position between the communication pipe 21 and the pump housing 7. Therefore, the first partition wall 30 receives an upward force equivalent to the difference between the pressure in the first high-pressure chamber 25 and the pressure in the first low-pressure chamber 23.

[0104] The liquid hydrogen in the first low-pressure chamber 23 passes through the bearing 5 and further flows into the motor 10 (see Figure 1 ) in the inner chamber. The liquid hydrogen contacts the bearing 6 and passes through the connecting pipe 21 to return to the low-pressure side of the pump housing 7 (refer to Figure 1 In one embodiment, liquid hydrogen may also be returned to the intake container 12 .

[0105] Fig.10 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balance mechanism 20. The structure of this embodiment and the reference Figures 1 to 3 The embodiments described are the same, so the repeated description is omitted. Fig.10 As shown, the first thrust balance mechanism 20 includes a first wall structure 26 having a first low-pressure chamber 23 and a first high-pressure chamber 25 therein, and a first fixed-side partition wall 30A and a first rotating-side partition wall 30B disposed in the first wall structure 26 and disposed between the first low-pressure chamber 23 and the first high-pressure chamber 25. The first fixed-side partition wall 30A is fixed to the first wall structure 26, and the first rotating-side partition wall 30B is fixed to the rotating shaft 1. Therefore, the first fixed-side partition wall 30A is a stationary component, and the first rotating-side partition wall 30B is a rotating component.

[0106] The first fixed side partition wall 30A is located below the first rotating side partition wall 30B. The first balance chamber 24 is located between the first fixed side partition wall 30A and the first rotating side partition wall 30B. The first fixed side partition wall 30A is located between the first balance chamber 24 and the first high pressure chamber 25, and the first rotating side partition wall 30B is located between the first balance chamber 24 and the first low pressure chamber 23.

[0107] The first fixed side partition wall 30A has a stationary surface 31, and has a movable surface 32 on the back side of the final stage impeller 2h as a part of the rotating body, which is parallel to the stationary surface 31. Between the stationary surface 31 of the first fixed side partition wall 30A and the movable surface 32 of the final stage impeller 2h, a variable gap (variable flow rate) C5 whose size changes with the axial movement of the rotating shaft 1 is formed.

[0108] The first rotating side partition wall 30B has a piston shape and is fixed to the rotating shaft 1. The first rotating side partition wall 30B rotates integrally with the rotating shaft 1 in the first wall structure 26 and can move axially integrally with the rotating shaft 1. The first wall structure 26 has an inner peripheral surface 33 parallel to the axial direction of the rotating shaft 1, and the first rotating side partition wall 30B has an outer peripheral surface 34 parallel to the axial direction of the rotating shaft 1. The entire outer peripheral surface 34 of the first rotating side partition wall 30B is surrounded by the inner peripheral surface 33 of the first wall structure 26 via a gap C6. The first rotating side partition wall 30B can move axially in the first wall structure 26 along with the axial movement of the rotating shaft 1.

[0109] The size of the radial gap C6 formed between the outer peripheral surface 34 of the first rotating side partition wall 30B and the inner peripheral surface 33 of the first wall structure 26 is constant regardless of the axial position of the rotating shaft 1. Therefore, the gap C6 is a fixed gap (fixed flow rate).

[0110] A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h flows into the first high-pressure chamber 25. The liquid hydrogen in the first high-pressure chamber 25 further flows into the first balance chamber 24 through the gap C5 (variable flow rate). The liquid hydrogen in the first balance chamber 24 flows into the first low-pressure chamber 23 through the gap C6 (fixed flow rate). The pressure of the liquid hydrogen decreases as the liquid hydrogen passes through the gap C6. The pressure of the liquid hydrogen in the first balance chamber 24 changes with the size of the gap C5, and as a result, the upward force generated by the first thrust balance mechanism 20 changes.

[0111] Fig.11 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balance mechanism 20. The structure of this embodiment and the reference Fig.10 The embodiments described are the same, so the repeated description is omitted. Fig.11 As shown, the first fixed side partition wall 30A is located above the first rotating side partition wall 30B. The first balance chamber 24 is located between the first fixed side partition wall 30A and the first rotating side partition wall 30B. The first rotating side partition wall 30B is located between the first balance chamber 24 and the first high pressure chamber 25, and the first fixed side partition wall 30A is located between the first balance chamber 24 and the first low pressure chamber 23.

[0112] The first fixed side partition wall 30A has a stationary surface 31, and the first rotating side partition wall 30B has a movable surface 32 parallel to the stationary surface 31. A variable gap (variable flow rate) C5 whose size changes with the axial movement of the rotating shaft 1 is formed between the stationary surface 31 of the first fixed side partition wall 30A and the movable surface 32 of the first rotating side partition wall 30B.

[0113] The entire outer peripheral surface 34 of the first rotating side partition wall 30B is surrounded by the inner peripheral surface 33 of the first wall structure 26 via a gap C6. The first rotating side partition wall 30B can move axially in the first wall structure 26 along with the axial movement of the rotating shaft 1. The size of the radial gap C6 formed between the outer peripheral surface 34 of the first rotating side partition wall 30B and the inner peripheral surface 33 of the first wall structure 26 is fixed regardless of the axial position of the rotating shaft 1. Therefore, the gap C6 is a fixed gap (fixed flow rate).

[0114] A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h flows into the first high-pressure chamber 25. The liquid hydrogen in the first high-pressure chamber 25 further flows into the first balance chamber 24 through the gap C6 (fixed flow rate). The pressure of the liquid hydrogen decreases as the liquid hydrogen passes through the gap C6. The liquid hydrogen in the first balance chamber 24 flows into the first low-pressure chamber 23 through the gap C5 (variable flow rate). The pressure of the liquid hydrogen in the first balance chamber 24 changes with the size of the gap C5, and as a result, the upward force generated by the first thrust balance mechanism 20 changes.

[0115] Fig.12 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balance mechanism 20. The structure of this embodiment and the reference Figures 1 to 3 The embodiments described are the same, so the repeated description is omitted. Fig.12 As shown, the first thrust balance mechanism 20 has a first wall structure 26 having a first low-pressure chamber 23 and a first high-pressure chamber 25 inside, and a first partition wall 30 disposed in the first wall structure 26 and disposed between the first low-pressure chamber 23 and the first high-pressure chamber 25. The first partition wall 30 is integrally formed on the back side of the final stage impeller 2h. Therefore, the first partition wall 30 can rotate integrally with the rotating shaft 1 and move integrally with the rotating shaft 1 in the axial direction. In one embodiment, the first partition wall 30 can also be a component independent of the impeller 2h.

[0116] The first wall structure 26 has a stationary surface 31, and the first partition wall 30 has a movable surface 32 parallel to the stationary surface 31. Between the stationary surface 31 of the first wall structure 26 and the movable surface 32 of the first partition wall 30, a variable gap (variable flow rate) C5 whose size changes with the axial movement of the rotating shaft 1 is formed.

[0117] The first wall structure 26 has an inner peripheral surface 33 parallel to the axial direction of the rotating shaft 1, and the first partition wall 30 has an outer peripheral surface 34 parallel to the axial direction of the rotating shaft 1. The entire outer peripheral surface 34 of the first partition wall 30 is surrounded by the inner peripheral surface 33 of the first wall structure 26 via a gap C6. The size of the radial gap C6 formed between the outer peripheral surface 34 of the first partition wall 30 and the inner peripheral surface 33 of the first wall structure 26 is fixed regardless of the axial position of the rotating shaft 1. Therefore, the gap C6 is a fixed gap (fixed flow rate).

[0118] The first balancing chamber 24 is formed by the first partition wall 30 and the first wall structure 26, and is located between the gap C6 (fixed flow) and the gap C5 (variable flow). The gap C6 is located between the first high-pressure chamber 25 and the first balancing chamber 24, and the gap C5 is located between the first balancing chamber 24 and the first low-pressure chamber 23.

[0119] A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h flows into the first high-pressure chamber 25. The liquid hydrogen in the first high-pressure chamber 25 further flows into the first balance chamber 24 through the gap C6 (fixed flow rate). The pressure of the liquid hydrogen decreases as the liquid hydrogen passes through the gap C6. The liquid hydrogen in the first balance chamber 24 flows into the first low-pressure chamber 23 through the gap C5 (variable flow rate). The pressure of the liquid hydrogen in the first balance chamber 24 changes with the size of the gap C5, and as a result, the upward force generated by the first thrust balance mechanism 20 changes.

[0120] exist Fig.12 In the illustrated embodiment, a variable gap (variable flow rate) C5 whose size changes with the axial movement of the rotary shaft 1 is provided on the back side of the final-stage impeller 2h.

[0121] Fig.13 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balance mechanism 20. The structure of this embodiment and the reference Figures 1 to 3 The embodiments described are the same, so the repeated description is omitted. Fig.13 As shown, the pump device has a first wear ring 35 located on the outer periphery of the final stage impeller 2h and a second wear ring 36 located on the back side of the impeller 2h. The outer periphery of the first wear ring 35 faces the inner periphery of an expansion block 37 arranged radially outward of the impeller 2h.

[0122] The first wear-resistant ring 35 may be integrated with the impeller 2h, or may be a separate component from the impeller 2h. The outer peripheral surface of the second wear-resistant ring 36 faces the inner peripheral surface of the first wall structure 26. The second wear-resistant ring 36 may be a separate component from the impeller 2h, or may be integrated with the impeller 2h.

[0123] A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h flows into the first high-pressure chamber 25 through the small gap between the first wear-resistant ring 35 and the expansion block 37. The liquid hydrogen in the first high-pressure chamber 25 further flows into the first balance chamber 24 through the small gap between the second wear-resistant ring 36 and the first wall structure 26. The pressure of the liquid hydrogen decreases as the liquid hydrogen passes through the gap between the first wear-resistant ring 35 and the expansion block 37 and the gap between the second wear-resistant ring 36 and the first wall structure 26. As a result, the pressure acting on the back side of the final-stage impeller 2h decreases, and the downward shaft thrust decreases. The liquid hydrogen in the first balance chamber 24 flows into the first low-pressure chamber 23 through the gap C1 (variable flow rate). The pressure of the liquid hydrogen in the first balance chamber 24 changes with the size of the gap C1, and as a result, the upward force generated by the first thrust balance mechanism 20 changes.

[0124] exist Fig.13 In the embodiment shown, two layers of wear-resistant rings 35 and 36 are provided, but only one layer of wear-resistant rings may be provided, or more than three layers of wear-resistant rings may be provided. The larger the diameter of the wear-resistant ring, the smaller the pressure acting on the back side of the impeller 2h, and the downward shaft thrust can be reduced. The position of the wear-resistant ring is not limited to the position of this embodiment, and may also be provided at other positions. In addition, on the basis of the final stage impeller 2h, the wear-resistant ring 35 may also be provided on other impellers.

[0125] Fig.14 FIG. 2 is an enlarged cross-sectional view showing another embodiment of the first thrust balance mechanism 20. The structure of this embodiment and the reference Fig.11 The embodiments described are the same, so the repeated description is omitted. Fig.14 As shown, the pump device has an auxiliary impeller 39 disposed between the final stage impeller 2h and the first thrust balance mechanism 20. The auxiliary impeller 39 is located on the upstream side of the first fixed side partition wall 30A and the first rotating side partition wall 30B. In other words, the auxiliary impeller 39 is located between the final stage impeller 2h and the first partition walls 30A, 30B. The auxiliary impeller 39 is fixed to the rotating shaft 1 and rotates integrally with the rotating shaft 1. The liquid inlet of the auxiliary impeller 39 faces the back side of the final stage impeller 2h.

[0126] A portion of the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h is further pressurized by the rotation of the auxiliary impeller 39 and discharged to the first high-pressure chamber 25. The pressurized liquid hydrogen flows into the first balance chamber 24 through the gap C6 (fixed flow rate). The pressure of the liquid hydrogen decreases as the liquid hydrogen passes through the gap C6. The liquid hydrogen in the first balance chamber 24 flows into the first low-pressure chamber 23 through the gap C5 (variable flow rate). The pressure of the liquid hydrogen in the first balance chamber 24 changes with the size of the gap C5, and as a result, the upward force generated by the first thrust balance mechanism 20 changes.

[0127] according to Fig.14 In the embodiment shown, the liquid hydrogen pressurized by the rotation of the plurality of impellers 2a to 2h is further pressurized by the rotation of the auxiliary impeller 39. Therefore, the difference in pressure acting on the front side and the back side of the first rotating side partition wall 30B becomes larger, and the first thrust balance mechanism 20 can generate a larger upward force.

[0128] Next, refer to Fig.15 The configuration and operation of this embodiment not specifically described are similar to those of the reference embodiment. Figures 1 to 4 The described implementation modes are the same, and therefore, repeated descriptions thereof will be omitted.

[0129] like Fig.15 As shown, the first thrust balancing mechanism 20 and the second thrust balancing mechanism 40 are arranged on the discharge side of the plurality of impellers 2a to 2h. More specifically, the first thrust balancing mechanism 20 is located on the discharge side of the final stage impeller 2h, and the second thrust balancing mechanism 40 is arranged at a position higher than the first thrust balancing mechanism 20. The first thrust balancing mechanism 20 is located between the plurality of impellers 2a to 2h and the second thrust balancing mechanism 40. In the present embodiment, the motor 10 is located between the first thrust balancing mechanism 20 and the second thrust balancing mechanism 40, but the second thrust balancing mechanism 40 may also be located between the first thrust balancing mechanism 20 and the motor 10.

[0130] The second high pressure chamber 45 of the second thrust balance mechanism 40 is communicated with the discharge side of the intermediate stage impeller 2d among the plurality of impellers 2a to 2h through the intermediate communication conduit 41. The second low pressure chamber 43 is communicated with the discharge side of the first stage impeller 2a, which is the suction side impeller located upstream of the intermediate stage impeller 2d, through the return conduit 80.

[0131] Fig.16 Yes means Fig.15 FIG. 4 is an enlarged cross-sectional view of the second thrust balancing mechanism 40. Fig.16 As shown, the second thrust balance mechanism 40 is arranged in the motor housing 10C. The second thrust balance mechanism 40 has a second wall structure 46 having a second low-pressure chamber 43 and a second high-pressure chamber 45 therein, and a second partition wall 50 arranged in the second wall structure 46 and arranged between the second low-pressure chamber 43 and the second high-pressure chamber 45. The second high-pressure chamber 45 is located below the second low-pressure chamber 43.

[0132] The second partition wall 50 has a piston shape and is fixed to the upper end of the rotating shaft 1. The second partition wall 50 can rotate integrally with the rotating shaft 1 in the second wall structure 46 and can move integrally with the rotating shaft 1 in the axial direction. The second wall structure 46 has an inner peripheral surface 52 parallel to the axial direction of the rotating shaft 1, and the second partition wall 50 has an outer peripheral surface 53 parallel to the axial direction of the rotating shaft 1. The entire outer peripheral surface 53 of the second partition wall 50 is surrounded by the inner peripheral surface 52 of the second wall structure 46 via a gap C2. Therefore, the second partition wall 50 can move axially in the second wall structure 46 along with the axial movement of the rotating shaft 1.

[0133] A radial gap C2 is provided between the outer peripheral surface 53 of the second partition wall 50 and the inner peripheral surface 52 of the second wall structure 46. The size of the radial gap C2 is fixed regardless of the axial position of the rotating shaft 1. The second thrust balance mechanism 40 of the present embodiment is a fixed gap type in which the size of the radial gap C2 is constant regardless of the axial position of the rotating shaft 1.

[0134] In order to seal the gap between the rotating shaft 1 and the second wall structure 46 forming the second high-pressure chamber 45, the wear ring 75 is fixed to the second wall structure 46. A small gap (not shown) is formed between the rotating shaft 1 and the wear ring 75, and the wear ring 75 minimizes the communication of the fluid between the motor housing 10C and the second high-pressure chamber 45. Therefore, the pressure in the second high-pressure chamber 45 is substantially equal to the pressure on the discharge side of the intermediate-stage impeller 2d.

[0135] In one embodiment, Fig.15 as well as Fig.16 The second thrust balancing mechanism 40 shown may be Figure 8 In this case, the first thrust balance mechanism 20 may also be a variable gap type. Fig. 9 Fixed gap type shown. Figures 5 to 7 The described embodiments can also be applied to Fig.15 as well as Fig.16 Description of the embodiment.

[0136] In one embodiment, it is also possible to have a reference Figures 4 to 8 The second thrust balance mechanism 40 on the lower side of the description and the reference Fig.15 as well as Fig.16 Both sides of the second thrust balance mechanism 40 on the upper side are described.

[0137] Fig.17 2 is a cross-sectional view showing another embodiment of the pump device. The structure and operation of this embodiment not specifically described are similar to those of the reference Figures 1 to 4 The embodiments described are the same, so the repeated description is omitted. Fig.17As shown, the pump device further includes a gas release line 95 extending from the second thrust balance mechanism 40 to the upper region in the suction container 12 .

[0138] The gas release line 95 is arranged outside the pump housing 7 and the motor 10, and the entire gas release line 95 is arranged in the suction container 12. The gas release line 95 extends upward from the second thrust balance mechanism 40 along the pump housing 7 and the motor 10. The upper end opening 95a of the gas release line 95 is located in the suction container 12, and is located at a position higher than the suction port 15 of the suction container 12.

[0139] Fig.18 Yes means Fig.17 FIG. 4 is an enlarged cross-sectional view of an embodiment of the second thrust balancing mechanism 40. Fig.18 As shown, the lower portion of the gas release line 95 is connected to the second wall structure 46. More specifically, the lower portion of the gas release line 95 extends inside the second wall structure 46, and further penetrates the sliding bearing 55 in its radial direction. The lower end opening 95b of the gas release line 95 is located above the second low-pressure chamber 43, and is located below the inlet 7a of the liquid hydrogen of the pump housing 7. The lower end opening 95b of the gas release line 95 is opposite to the outer peripheral surface of the rotating shaft 1. More specifically, the lower end opening 95b of the gas release line 95 is connected to the gap between the outer peripheral surface of the rotating shaft 1 and the inner peripheral surface of the sliding bearing 55. In one embodiment, there is also a case where the sliding bearing 55 is not provided. In this embodiment, the lower end opening 95b of the gas release line 95 is connected to the gap between the outer peripheral surface of the rotating shaft 1 and the inner peripheral surface of the second wall structure 46.

[0140] The gas release line 95 is provided for the following reasons. A portion of the liquid hydrogen in the second low-pressure chamber 43 passes through the gap between the outer peripheral surface of the rotating shaft 1 and the inner peripheral surface of the sliding bearing 55 and is discharged into the liquid hydrogen inlet 7a. When the liquid hydrogen flows through the gap between the outer peripheral surface of the rotating shaft 1 and the inner peripheral surface of the sliding bearing 55, the pressure of the liquid hydrogen decreases and a portion of the liquid hydrogen gasifies, sometimes generating bubbles. If such bubbles are sucked into the impellers 2a to 2h, there is a concern that the pump device may not be able to achieve the desired pump performance.

[0141] therefore, Fig.18 The pump device of the embodiment shown has a gas release line 95 having a lower end opening 95b facing the outer peripheral surface of the rotating shaft 1 at an upper position of the second low-pressure chamber 43. The gas release line 95 extends from the second wall structure 46 to the upper area in the suction container 12. Bubbles generated in the gap between the outer peripheral surface of the rotating shaft 1 and the inner peripheral surface of the sliding bearing 55 pass through the gas release line 95 and move to the upper area in the suction container 12. Therefore, the impellers 2a to 2h do not suck in bubbles, and the pump performance is ensured.

[0142] like Fig.17 As shown, the upper end opening 95a of the gas release line 95 is located higher than the suction port 15 of the suction container 12. This is to prevent the bubbles released from the gas release line 95 from being transported to the inlet 7a of the pump housing 7 through the liquid hydrogen introduced from the suction port 15 of the suction container 12.

[0143] Fig.19 FIG. 1 is a cross-sectional view showing another embodiment of a pump device having a gas release line 95. The structure and operation of this embodiment not specifically described are similar to those of the reference Fig.17 as well as Fig.18 The embodiments described are the same, so the repeated description is omitted. Fig.19 As shown, the lower end 95b of the gas release conduit 95 is connected to the second low-pressure chamber 43. More specifically, the lower end 95b of the gas release conduit 95 is connected to the upper wall 46a of the second wall structure 46. The gas release conduit 95 extends upward from the second low-pressure chamber 43. The bubbles generated in the second low-pressure chamber 43 pass through the gas release conduit 95 and are transferred to the upper area in the suction container 12. Therefore, the impellers 2a to 2h do not suck in the bubbles, and the pump performance is ensured.

[0144] In one embodiment, Figures 17 to 19 The second thrust balancing mechanism 40 shown may also be Figure 8 In this case, the first thrust balance mechanism 20 may also be a variable gap type. Fig. 9 Fixed gap type shown.

[0145] Reference Figures 17 to 19 The described embodiments can also be used with reference to Figure 6 For example, Fig. 20 As shown, the pump device further includes an upstream communication line 90 that connects the discharge side of the second-stage impeller 2b as the upstream impeller with the second high-pressure chamber 45, and a check valve 91 installed in the upstream communication line 90 and allowing only the flow of liquid hydrogen toward the second high-pressure chamber 45. Fig. 20 The illustrated embodiment can ensure the pump performance during the steady operation of the pump device and reduce the load on the bearings 5 ​​and 6 during the start-up of the pump device.

[0146] The above-mentioned embodiments may also be appropriately combined. Figure 5 , Figure 6 , Figure 7 The described embodiments can also be used with reference to Fig.17 , Fig.18 , Fig.19 , Fig. 20 The described embodiments may be combined as appropriate.

[0147] According to the above-mentioned embodiments, even for liquid hydrogen having a low density, the first thrust balance mechanism 20 and the second thrust balance mechanism 40 can generate an upward force that cancels out the deadweight of the rotating body and the axial thrust. As a result, the load on the bearings 5 ​​and 6 supporting the rotating shaft 1 becomes substantially zero, which can reduce damage to the bearings 5 ​​and 6, resulting in a longer life.

[0148] The purpose of recording the above-mentioned embodiments is to enable people with common knowledge in the technical field to which the present invention belongs to implement. As long as a person skilled in the art can certainly obtain various variations of the above-mentioned embodiments, the technical idea of ​​the present invention can also be applied to other embodiments. Therefore, the present invention is not relative to the recorded embodiments, and can be interpreted within the maximum scope determined by the technical idea defined by the technical solution.

[0149] Industrial Applicability

[0150] The present invention can be used in a pump device for increasing the pressure of liquid hydrogen, and in particular, can be used in a pump device having a thrust balancing mechanism for offsetting the axial thrust applied to an impeller.

[0151] Description of Reference Numerals

[0152] 1 Rotation axis

[0153] 2a~2h impeller

[0154] 5.6 Bearings

[0155] 7 Pump housing

[0156] Entrance 7a

[0157] 10 Electric Motor

[0158] 10A motor rotor

[0159] 10B motor stator

[0160] 10C motor housing

[0161] 12 suction containers

[0162] 15 suction port

[0163] 16Discharge flow path

[0164] 17Exit

[0165] 201st thrust balance mechanism

[0166] 21 connecting pipeline

[0167] 23 Low-pressure room 1

[0168] 24Balance Room 1

[0169] 25 No.1 High Voltage Chamber

[0170] 26 1st wall structure

[0171] 30 Next Door

[0172] 30A 1st fixed side bulkhead

[0173] 30B 1st rotating side partition

[0174] 31Stationary surface

[0175] 32 movable surfaces

[0176] 35 No.1 wear ring

[0177] 36 2nd wear ring

[0178] 37 expansion block

[0179] 39 Auxiliary impeller

[0180] 40 Second thrust balance mechanism

[0181] 41 Intermediate connecting pipeline

[0182] 43 Second Low-pressure Room

[0183] 44 Balance Room 2

[0184] 45 No.2 High Pressure Chamber

[0185] 46 2nd wall structure

[0186] 50 Next Door

[0187] 52 Inner Surface

[0188] 53 Outer Surface

[0189] 55 Sliding bearing

[0190] 57 Movable Surface

[0191] 58 stationary surface

[0192] 61 Inner Surface

[0193] 62 Outer Surface

[0194] 71 through holes

[0195] 75 wear ring

[0196] 80 return line

[0197] 85 Check Valve

[0198] 90 Upstream connecting pipe

[0199] 91 Check Valve

[0200] 95 Gas release pipeline

[0201] C1, C2, C3, C4, C5, C6 gaps.

Claims

1. A pump device for increasing the pressure of liquid hydrogen, wherein: The pump device comprises: Axis of rotation; a plurality of impellers fixed to the rotating shaft; A bearing for rotatably supporting the rotating shaft; a pump housing for accommodating a plurality of said impellers; and a first thrust balancing mechanism and a second thrust balancing mechanism for offsetting the deadweight of a rotating body and the shaft thrust acting on the plurality of impellers, wherein the rotating body includes the rotating shaft and the plurality of impellers, The second thrust balancing mechanism comprises: A wall structure having a low pressure chamber and a high pressure chamber therein; and a partition wall disposed in the wall structure and between the low-pressure chamber and the high-pressure chamber, The pump device comprises: an intermediate communication pipeline that connects the discharge side of an intermediate stage impeller or a final stage impeller among the plurality of impellers with the high pressure chamber; and A return line connects the discharge side of a suction-side impeller located upstream of the intermediate-stage impeller or the final-stage impeller to the low-pressure chamber.

2. The pump device according to claim 1, wherein: A check valve is further provided, which is installed in the return line and allows only the flow of liquid hydrogen from the low-pressure chamber toward the suction-side impeller.

3. The pump device according to claim 1, wherein: Further having: an upstream communication pipeline that connects the discharge side of the upstream impeller located between the intermediate-stage impeller or the final-stage impeller and the suction-side impeller with the high-pressure chamber; and A check valve is installed in the upstream communication pipeline to only allow liquid hydrogen to flow from the upstream impeller to the high-pressure chamber.

4. The pump device according to claim 1, wherein: The first thrust balancing mechanism is arranged on the discharge side of the plurality of impellers. The second thrust balancing mechanism is arranged on the suction side of the plurality of impellers.

5. The pump device according to claim 4, wherein: The pump device further comprises: a suction container having a suction port for the liquid hydrogen and surrounding the pump housing; and a gas release conduit extending from the wall structure to an upper region within the suction container, The lower end opening of the gas release conduit is located above the low-pressure chamber and faces the outer peripheral surface of the rotating shaft.

6. The pump device according to claim 1, wherein: The wall structure has an inner peripheral surface parallel to the axial direction of the rotating shaft. The partition wall has an outer peripheral surface parallel to the axial direction of the rotating shaft, The entire outer peripheral surface of the partition wall is surrounded by the inner peripheral surface of the wall structure via a gap.

7. The pump device of claim 1, wherein: The second thrust balance mechanism further includes a balance chamber located between the low-pressure chamber and the high-pressure chamber. A variable gap whose size varies depending on the axial position of the rotating shaft is formed between the partition wall and the wall structure.

8. The pump device of claim 1, wherein: The first thrust balancing mechanism and the second thrust balancing mechanism are arranged on the discharge side of the plurality of impellers.

9. The pump device of claim 1, wherein: The first thrust balancing mechanism comprises: a first wall structure having a first low-pressure chamber, a first balance chamber and a first high-pressure chamber therein; and the first partition wall arranged in the first wall structure and between the first low-pressure chamber and the first balance chamber, wherein a variable gap whose size varies with the axial position of the rotating shaft is formed between the first partition wall and the rotating body, wherein the rotating body comprises the rotating shaft and the plurality of impellers.

10. The pump device of claim 1, wherein: The first thrust balancing mechanism comprises: a first wall structure having a first low-pressure chamber and a first high-pressure chamber therein; and a first partition wall arranged in the first wall structure and between the first low-pressure chamber and the first high-pressure chamber, wherein a radial gap of a size which does not vary according to the axial position of the rotating shaft is formed between an outer peripheral surface of the first partition wall and an inner peripheral surface of the first wall structure.

11. A pump device for increasing the pressure of liquid hydrogen, wherein: The pump device comprises: Axis of rotation; a plurality of impellers fixed to the rotating shaft; A bearing for rotatably supporting the rotating shaft; a pump housing for accommodating a plurality of said impellers; a suction container having a suction port for the liquid hydrogen and surrounding the pump housing; Gas release lines; and a thrust balancing mechanism for canceling out the deadweight of a rotating body and the shaft thrust acting on the plurality of impellers, wherein the rotating body includes the rotating shaft and the plurality of impellers, The thrust balancing mechanism comprises: A wall structure having a low pressure chamber and a high pressure chamber therein; and a partition wall disposed in the wall structure and between the low-pressure chamber and the high-pressure chamber, The gas release conduit extends from the wall structure to an upper area within the suction container, The lower end of the gas release pipeline is communicated with the low-pressure chamber.

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