Liquefied gas pumps and methods for operating liquefied gas pumps.

Abstract

The present invention provides a liquefied gas pump and a method for operating the liquefied gas pump that can suppress wear of the thrust bearing during startup and shutdown. [Solution] The liquefied gas pump comprises a rotating shaft that can rotate around its axis, an impeller integrally mounted on the rotating shaft and capable of pumping liquefied gas by rotating together with the rotating shaft, an electric motor that rotates the rotating shaft around its axis, a bearing device that supports the rotating shaft so that it can rotate around its axis, a liquefied gas supply source that can supply liquefied gas to the bearing device at a first pressure, and a switching unit that can switch between a state in which the bearing device is in communication with a second pressure space lower than the first pressure and a state in which it is not in communication with the second pressure space.

Description

Technical Field

[0001] The present disclosure relates to a liquefied gas pump and a method for operating a liquefied gas pump.

Background Art

[0002] As a pump for boosting the pressure of a liquid, there is a vertical rotary pump. For example, Patent Document 1 discloses a technique for simplifying the structure, improving the reliability, and enhancing the efficiency of a pump for liquefied gas used in a low-temperature environment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a hydrostatic sliding bearing is used as a thrust bearing in a pump whose rotating shaft extends in the vertical direction, contrivance is required at the time of starting and stopping the pump. That is, when the hydrostatic pressure is supplied to the hydrostatic sliding bearing from the impeller, the hydrostatic pressure is not supplied at the time of starting and stopping. Therefore, at the location where the rotating shaft is supported in the vertical direction, the hydrostatic pressure is not stably supplied and friction occurs. As a result, the thrust bearing may be worn out.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a liquefied gas pump and a method for operating a liquefied gas pump that can suppress wear of a thrust bearing at the time of starting and stopping.

Means for Solving the Problems

[0006] To solve the above problems, the liquefied gas pump according to this disclosure comprises: a rotating shaft rotatable about an axis; an impeller integrally provided with the rotating shaft and capable of pumping liquefied gas by rotating together with the rotating shaft; an electric motor that rotates the rotating shaft about the axis; a bearing device that supports the rotating shaft so as to be rotatable about the axis; a liquefied gas supply source capable of supplying the liquefied gas to the bearing device at a first pressure; and a switching unit capable of switching the bearing device between a state in which it is in communication with a space at a second pressure lower than the first pressure and a state in which it is not in communication with the space at the second pressure.

[0007] The method for operating a liquefied gas pump according to the present disclosure is a method for operating a liquefied gas pump, the liquefied gas pump comprising: a rotating shaft rotatable around an axis; an impeller integrally provided with the rotating shaft and capable of pumping liquefied gas by rotating together with the rotating shaft; an electric motor for rotationally driving the rotating shaft around the axis; a bearing device for supporting the rotating shaft so as to be rotatable around the axis; a liquefied gas supply source capable of supplying the liquefied gas to the bearing device at a first pressure; and a switching unit capable of switching the bearing device between a state in which it is in communication with a space at a second pressure lower than the first pressure and a state in which it is not in communication with the space at the second pressure, the method for operating the liquefied gas pump comprising: a pre-cooling step of supplying the liquefied gas to the flow path of the liquefied gas pump at the first pressure; a startup communication step after the pre-cooling step of connecting the bearing device to the space at the second pressure; and a drive step after the startup communication step of rotationally driving the rotating shaft around the axis. [Effects of the Invention]

[0008] According to the liquefied gas pump and operating method of the liquefied gas pump described herein, wear of the thrust bearing during starting and stopping can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the overall liquefied gas pump according to an embodiment of the present disclosure. [Figure 2]This is an enlarged view of a key part showing the flow of liquefied gas in a liquefied gas pump according to an embodiment of this disclosure. [Figure 3] This is a cross-sectional view showing the flow of liquefied gas near the thrust bearing of a liquefied gas pump according to an embodiment of the present disclosure. [Figure 4] This flowchart shows an example of an operating method for a liquefied gas pump according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0010] <Embodiment> The embodiments relating to this disclosure will be described in detail below with reference to the drawings.

[0011] <Liquefied gas pump> First, the liquefied gas pump 1 will be explained with reference to Figures 1 to 3. As shown in Figure 1, the liquefied gas pump 1 is positioned so as to be suspended inside the sump 50. The liquefied gas pump 1 is a device for pressurizing liquefied gas as a fluid. In this embodiment, the liquefied gas pump 1 for pressurizing liquid hydrogen will be described. Note that the fluid is not limited to liquid hydrogen, but may be other liquids or gases. For example, liquefied natural gas (LNG) is one example.

[0012] The sump 50 is capable of storing liquid. In this embodiment, the sump 50 is capable of storing liquid hydrogen. The sump 50 is a vacuum-insulated container. That is, the sump 50 is an insulated structure with a bottomed cylindrical shape. A liquid storage chamber 53 is formed inside the sump 50. The liquid storage chamber 53 is capable of storing liquid hydrogen. The sump 50 has an outer peripheral flange 51 provided on its upper vertical side. The sump 50 is installed on a stand (not shown). The sump 50 has an upper flange provided on its upper vertical side. The upper flange is provided vertically above the outer peripheral flange 51. The upper flange and the outer peripheral flange 51 are arranged in contact with each other. The upper flange and the outer peripheral flange 51 are connected, for example, via bolts. The upper flange is positioned to maintain the airtightness of the sump 50. The upper flange can also be installed in a manner that suspends the liquefied gas pump 1.

[0013] The sump 50 has a supply pipe 60 and a gas discharge pipe 61 connected to its side. The supply pipe 60 is a pipe that allows liquid hydrogen to be supplied to the liquid storage chamber 53 from an external source. The gas discharge pipe 61 is a pipe that allows vaporized hydrogen from the liquid storage chamber 53 to be discharged to the outside of the sump 50. The gas discharge pipe 61 is located vertically above the supply pipe 60. The gas discharge pipe 61 may also be capable of discharging liquid hydrogen to the outside of the sump 50, as well as vaporized hydrogen.

[0014] The liquefied gas pump 1 comprises a liquefied gas supply source 2, an external sump 3, a communication channel 4, a switching unit 5, and a pump body 6. The liquefied gas supply source 2 is capable of circulating liquefied gas. The liquefied gas supply source 2 of this embodiment is capable of circulating liquid hydrogen. The liquefied gas supply source 2 is capable of supplying liquid hydrogen to the bearing device 40 at a first pressure. The first pressure is an arbitrarily determined pressure value. The first pressure is, for example, the pressure inside the liquefied gas pump 1, i.e., the internal pressure. As shown in Figure 2, the liquefied gas supply source 2 of this embodiment is provided separately from the supply pipe 60. However, it is not limited to this, and for example, a branch from the supply pipe 60 may be provided as the liquefied gas supply source 2. The liquefied gas supply source 2 is in communication with the supply passage 80 (described later). That is, the liquefied gas supply source 2 is capable of supplying liquid hydrogen to the bearing device 40 through the supply passage 80.

[0015] The external sump 3 is separate from the sump 50 and is located outside the sump 50. The interior of the external sump 3 is a space 3A with a second pressure. The second pressure is a pressure value lower than the first pressure. The second pressure is also an arbitrarily determined pressure value. In this embodiment, the second pressure is atmospheric pressure, but is not limited to this. For example, the second pressure may be set to atmospheric pressure or lower by evacuating the external sump 3. Furthermore, the external sump 3 is capable of communicating with the bearing device 40, which will be described later. That is, the space 3A with the second pressure is capable of communicating with the bearing device 40. The external sump 3 and the bearing device 40 are capable of communicating with each other via a communication channel 4.

[0016] The communication passage 4 is provided to connect the external sump 3 and the bearing device 40. The communication passage 4 is a pipe through which liquid hydrogen can flow. The communication passage 4 has a communication passage 4A that communicates with the thrust bearing 44, and communication passages 4B and 4C that communicate with the radial bearing 41. However, the communication passage 4 is not limited to this configuration. The communication passage 4 may also be capable of handling gas. Furthermore, the communication passage 4 may be provided to communicate with locations other than the bearing device 40 of the pump body 6.

[0017] The switching unit 5 is capable of switching the external sample 3 and the bearing device 40 between a communicating state and a non-communicating state. In other words, the switching unit 5 is capable of switching the bearing device 40 between a state of communicating with the second-pressure space 3A and a state of not communicating with the second-pressure space 3A. The switching unit 5 is provided so as to be sandwiched by the communication flow path 4. Further, the switching unit 5 is disposed outside the sample 50. However, the position where the switching unit 5 is disposed is not limited thereto. For example, the switching unit 5 may be provided so as to connect the external sample 3 and the communication flow path 4. Also, for example, the switching unit 5 may be provided inside the sample 50.

[0018] The pump body is disposed inside the sample 50. The pump body includes a casing 10, a rotating shaft 20, an electric motor 30, an inducer 24, an impeller 25, a bearing device 40, and a supply passage 80. In the following, when simply referred to as a flow path, it refers to the portion of the liquefied gas pump 1 through which liquid hydrogen flows.

[0019] <Casing> The casing 10 forms the outer shell of the liquefied gas pump 1. The casing 10 has a hollow shape. The casing 10 may be composed of one member or may be composed of a plurality of members assembled integrally. The casing 10 is capable of accommodating the electric motor 30, the inducer 24, the impeller 25, and the bearing device 40 therein. The upper end portion of the casing 10 is connected to the upper flange and is suspended and supported inside the sample 50. The casing 10 has a cylindrical shape centered on an axis О extending along the vertical direction, but is not limited thereto. Also, both the sample 50 and the casing 10 extend centered on the axis О, but the centers of the sample 50 and the casing 10 may be offset.

[0020] The casing 10 is provided with a suction part 11 at the lower end. The suction part 11 is formed to communicate with the liquid storage chamber 53. The suction part 11 allows the liquid hydrogen stored in the liquid storage chamber 53 to flow through. Also, the casing 10 is provided with a discharge part 12 at the upper end. The discharge part 12 is connected to a discharge pipe 62 extending to the outside of the sump 50. Note that the suction part 11 may be directly connected to a pipe extended from a supply pipe 60 or the like. That is, the liquid hydrogen may be directly introduced from the pipe to the suction part 11 without being temporarily stored in the liquid storage chamber 53.

[0021] <Rotating shaft> The rotating shaft 20 is a rod-shaped member extending along the axis О. The rotating shaft 20 and the casing 10 are arranged concentrically about the axis О. The rotating shaft 20 is supported by a bearing device 40 so as to be rotatable about the axis О with respect to the casing 10. Hereinafter, the radial direction of the rotating shaft 20 will be simply referred to as the radial direction, and the circumferential direction of the rotating shaft 20 will be simply referred to as the circumferential direction. Also, the direction in which the axis О extends will be referred to as the axial direction. The rotating shaft 20 has an inducer 24, an impeller 25, and a rotor 36 of a motor 30 fixed thereto. Also, the rotating shaft 20 has a rotating shaft body 21 and a thrust collar 22.

[0022] The rotating shaft body 21 is a rod-shaped member extending along the axis О. The rotating shaft body 21 is connected and fixed to the thrust collar 22. The thrust collar 22 is fixed to the outer peripheral portion of the rotating shaft body 21. The thrust collar 22 is in a state of being fixed to the rotating shaft body 21 and is formed in a disc shape so as to increase the diameter of the rotating shaft body 21 in the radial direction. In other words, the thrust collar 22 is provided so as to project from the rotating shaft body 21 toward the outer peripheral side. The thrust collar 22 is rotatable integrally with the rotating shaft body 21. Also, the thrust collar 22 is movable integrally with the rotating shaft body 21 in the axial direction. The thrust collar 22 has an upper surface 22A facing upward and a lower surface 22B facing downward in the axial direction. Note that the rotating shaft body 21 and the thrust collar 22 may be integrally molded or may be separately molded and connected.

[0023] <Bearing device> The bearing device 40 is a component for supporting the rotating shaft 20 so that it can rotate around axis O relative to the casing 10. The bearing device 40 is fixedly installed inside the casing 10. The bearing device 40 is configured to be able to receive liquid hydrogen at a first pressure. The bearing device 40 is also configured to be able to communicate with a second pressure space 3A. The bearing device 40 includes a radial bearing 41 and a thrust bearing 44.

[0024] The radial bearing 41 is positioned to withstand the radial load of the rotating shaft 20. That is, the radial bearing 41 is positioned concentrically with the rotating shaft 20 and is provided to cover the rotating shaft 20 from its outer circumferential surface. Multiple radial bearings 41 are provided. In this embodiment, a first radial bearing 42 and a second radial bearing 43 are provided. The first radial bearing 42 is positioned vertically above the casing 10. The second radial bearing 43 is positioned vertically below the casing 10. The radial bearing 41 in this embodiment is a sliding bearing, but the type is not limited. For example, the radial bearing 41 may be a rolling bearing. Also, the first radial bearing 42 and the second radial bearing 43 may be bearings of the same type, or they may be bearings of different types.

[0025] The thrust bearing 44 is positioned to withstand the axial load of the rotating shaft 20. The thrust bearing 44 is provided to clamp the thrust collar 22 in the axial direction. The thrust bearing 44 is a hydrostatic bearing. The thrust bearing 44 is provided to support the thrust collar 22 in the axial direction via fluid pressure. The thrust bearing 44 is provided to contact the lower surface 22B of the thrust collar 22 when the liquefied gas pump 1 is stopped. Furthermore, as shown in Figure 2, the thrust bearing 44 is capable of supplying liquid hydrogen from the liquefied gas supply source 2 at a first pressure. Figure 3 shows a cross-sectional view of the main part of the thrust bearing 44. The thrust bearing 44 has an upper bearing body 45 and a lower bearing body 46. The upper bearing body 45 and the lower bearing body 46 are ring-shaped. The upper bearing body 45 and the lower bearing body 46 are fixed to the casing 10.

[0026] The upper bearing body 45 is positioned opposite the upper surface 22A of the thrust collar 22 with a gap in the axial direction. The upper bearing body 45 has an upper pocket 45A, an upper manifold 45B, and an upper connecting passage 45C. The upper pocket 45A is formed in a position opposite the upper surface 22A of the thrust collar 22. The upper pocket 45A is formed such that the upper bearing body 45 is recessed upward in the axial direction. Multiple upper pockets 45A are provided at intervals in the circumferential direction. Liquid hydrogen is allowed to flow through the upper pocket 45A.

[0027] The upper manifold 45B is formed axially on the opposite side of the thrust collar 22 from the upper pocket 45A. The upper manifold 45B is formed such that the upper bearing body 45 protrudes upward in the axial direction. The upper manifold 45B has an annular shape along the circumferential direction. Liquid hydrogen is allowed to flow through the upper manifold 45B. The upper pocket 45A and the upper manifold 45B are connected by an upper connecting passage 45C. Liquid hydrogen is allowed to flow through the upper connecting passage 45C.

[0028] The lower bearing body 46 is positioned opposite the lower surface 22B of the thrust collar 22 with a gap in the axial direction. The lower bearing body 46 has a lower pocket 46A, a lower manifold 46B, and a lower connecting passage 46C. The lower pocket 46A is formed in a position opposite the lower surface 22B of the thrust collar 22. The lower pocket 46A is formed such that the lower bearing body 46 is recessed downward in the axial direction. Multiple lower pockets 46A are provided at intervals in the circumferential direction. Liquid hydrogen is allowed to flow through the lower pocket 46A.

[0029] The lower manifold 46B is formed axially on the opposite side of the thrust collar 22 from the lower pocket 46A. The lower manifold 46B is formed such that the lower bearing body 46 protrudes downward in the axial direction. The lower manifold 46B has an annular shape along the circumferential direction. Liquid hydrogen is allowed to flow through the lower manifold 46B. The lower pocket 46A and the lower manifold 46B are connected by a lower connecting passage 46C. Liquid hydrogen is allowed to flow through the lower connecting passage 46C.

[0030] Furthermore, the thrust bearing 44 is positioned vertically above the first radial bearing 42 and the second radial bearing 43. However, the position of the thrust bearing 44 is not limited to this. The thrust bearing 44 may be positioned between the first radial bearing 42 and the second radial bearing 43, or vertically below the first radial bearing 42 and the second radial bearing 43.

[0031] <Supply passage> The supply passage 80 is provided to connect the liquefied gas supply source 2 and the bearing device 40. The supply passage 80 is a pipe through which liquid hydrogen can flow. The supply passage 80 is connected to the bearing device 40 as follows: The supply passage 80 has a first supply passage 81, a second supply passage 82, a third supply passage 83, and a fourth supply passage 84. The first supply passage 81 is provided to communicate with the upper bearing body 45, specifically the upper manifold 45B. The second supply passage 82 is provided to communicate with the lower bearing body 46, specifically the lower manifold 46B. The third supply passage 83 is provided to communicate with the first radial bearing 42. The fourth supply passage 84 is provided to communicate with the second radial bearing 43.

[0032] The supply passage 80 may also be a passage formed in the casing 10. In other words, the supply passage 80 is not limited to a pipe. Furthermore, the supply piping may be provided to communicate not only with the liquefied gas supply source 2 and the bearing device 40, but also with other parts. In this embodiment, the supply passage 80 is provided to communicate with the second stage impeller 27 (described later).

[0033] <Inducer and Impeller> The inducer 24 and impeller 25 are configured to pump liquid hydrogen under pressure as the rotating shaft 20 rotates. The inducer 24 and impeller 25 are fixed to the rotating shaft 20 and are integrally mounted. The inducer 24 and impeller 25 are configured to rotate integrally with the rotating shaft 20. Furthermore, the inducer 24 and impeller 25 are configured to move integrally with the rotating shaft 20 in the axial direction. Multiple impellers 25 are provided and are spaced apart in the axial direction. The impeller 25 consists of a first-stage impeller 26, a second-stage impeller 27, and a third-stage impeller 28. Note that the number of impeller blades 25 is not limited to three. The number of impeller blades 25 may be two or fewer, or four or more.

[0034] The inducer 24 is located at the lower end of the rotating shaft 20. The first stage impeller 26 is provided integrally with the inducer 24. Specifically, the first stage impeller 26 is positioned axially above the inducer 24. The inducer 24 and the first stage impeller 26 are located in the suction section 11 of the casing 10. The second stage impeller 27 and the third stage impeller 28 are positioned axially above the first stage impeller 26. Specifically, the second stage impeller 27 and the third stage impeller 28 are positioned axially above the first stage impeller 26, sandwiching the second radial bearing 43. Note that the inducer 24 is not required.

[0035] <Electric motor> The electric motor 30 is a component for rotating the rotating shaft 20 around its axis. The electric motor 30 is installed inside the casing 10. The electric motor 30 has a rotor 36 and a stator 31.

[0036] The rotor 36 is a component that receives power to rotate the rotating shaft 20 around its axis and rotates the rotating shaft 20. The rotor 36 is integrally fixed to the rotating shaft 20. Specifically, the rotor 36 is fixed to the outer circumferential surface of the rotating shaft 20. The rotor 36 has a rotor core 38 and permanent magnets.

[0037] The rotor core 38 is arranged concentrically with the rotating shaft 20. The rotor core 38 is provided inside the stator 31, with a clearance between it and the stator 31. The rotor core 38 has an overall cylindrical shape that extends in the axial direction. The rotor core 38 is fixedly provided on the outer circumferential surface of the rotating shaft body 21. The rotor core 38 is made of multiple layers of electromagnetic steel sheets stacked in the axial direction. Multiple permanent magnets are provided inside the rotor core 38, spaced apart in the circumferential direction. In addition, the rotor core 38 may have a support member provided on its outer circumferential surface.

[0038] The stator 31 is fixed to the inner circumferential surface of the casing 10. The stator 31 is arranged concentrically with the rotating shaft 20 and the rotor 36. The stator 31 is cylindrical in shape. The stator 31 is arranged to surround the rotating shaft 20 and the rotor 36 from the radial outside. In other words, the stator 31 is facing the rotor 36 with a radial gap between them. The stator 31 has a stator core 32 and a coil 35.

[0039] The stator core 32 has a yoke and teeth. The yoke is cylindrical with an axis O. The yoke is fixed to the inner surface of the casing 10 with its outer surface fixed thereto. The teeth are provided so as to protrude from the inner surface of the yoke. Multiple teeth are formed, spaced apart from each other in the circumferential direction. Multiple coils 35 are provided, corresponding to each tooth. The coils 35 are wound around each tooth. Therefore, multiple coils 35 are provided, spaced apart in the circumferential direction.

[0040] <How to operate a liquefied gas pump> The operating method S1 of the liquefied gas pump in this embodiment will be explained according to the flowchart shown in Figure 4. The liquefied gas pump operating method S1 is a method for starting and stopping the liquefied gas pump 1. The liquefied gas pump operating method S1 includes a preparation step S11, a pre-cooling step S12, a start-up communication step S13, a drive step S14, a decommunication step S15, a drive stop step S16, and a stop-down communication step S17.

[0041] First, preparation step S11 is performed. In preparation step S11, the liquefied gas pump 1 described earlier is prepared. Also, the switching unit 5 is checked to confirm that the external sump 3 and the bearing device 40 are not in communication.

[0042] After performing the preparation step S11, the pre-cooling step S12 is performed. In the pre-cooling step S12, liquid hydrogen is supplied to the flow path of the liquefied gas pump 1 at a first pressure. The liquefied gas pump 1 is cooled by the liquid hydrogen. As a result of the pre-cooling step S12, the internal pressure inside the liquefied gas pump 1 is set to the first pressure.

[0043] After the pre-cooling process S12 is performed, the startup communication process S13 is performed. In the startup communication process S13, the switching unit 5 is operated to connect the external sump 3 and the bearing device 40. That is, in the startup communication process S13, the bearing device 40 is connected to the second pressure space 3A. Then, the liquid hydrogen at the first pressure flows toward the second pressure space 3A. Specifically, the liquid hydrogen supplied to the bearing device 40 from the liquefied gas supply source 2 flows toward the second pressure space 3A. Figure 3 shows the flow of liquid hydrogen in the thrust bearing 44 when the bearing device 40 is connected to the second pressure space 3A. After the liquid hydrogen flows through the upper bearing body 45 and the lower bearing body 46, it spreads radially between the upper bearing body 45 and the lower bearing body 46 and the thrust collar 22. The liquid hydrogen that has spread radially flows to the external sump 3 through the communication channel 4. In this way, by connecting the bearing device 40 to the second pressure space 3A, fluid pressure is applied to the bearing device 40, and the bearing device 40 functions as a sliding bearing.

[0044] After the startup communication process S13 is performed, the drive process S14 is performed. In the drive process S14, the electric motor 30 is driven to rotate the rotating shaft 20 around axis O. When the rotating shaft 20 rotates, the inducer 24 and impeller 25 fixed to the rotating shaft body 21 rotate, thereby operating the liquefied gas pump 1.

[0045] When the liquefied gas pump 1 is activated, the liquid hydrogen in the liquid storage chamber 53 is drawn into the suction section 11 by the inducer 24. The drawn-in liquid hydrogen is pressurized by one stage by the first-stage impeller 26. The pressurized liquid hydrogen is supplied to the second-stage impeller 27 through the flow path 70 provided in the casing 10. The liquid hydrogen is pressurized by two stages by the second-stage impeller 27. The pressurized liquid hydrogen is supplied to the third-stage impeller 28 through the flow path 71 provided in the casing 10. The liquid hydrogen is pressurized by three stages by the third-stage impeller 28. The pressurized liquid hydrogen is supplied to the discharge section 12 through the flow path 72 provided in the casing 10. The liquid hydrogen supplied to the discharge section 12 is discharged to the outside of the sump 50 from the discharge pipe 62. Furthermore, it is preferable that multiple flow paths 70, 71, and 72 are provided on the radially outer side of the impeller 25, spaced apart in the circumferential direction. In addition, other paths through which liquid hydrogen flows may be provided besides the above-mentioned flow paths 70, 71, and 72.

[0046] Furthermore, the distribution paths 70, 71, and 72 in this embodiment may be branched as appropriate. Distribution path 71 in this embodiment is provided to communicate with the supply path. That is, two-stage pressurized liquid hydrogen can be supplied to the bearing device 40. However, other branches may be provided as well.

[0047] When the liquefied gas pump 1 is started and the rotating shaft 20 reaches a predetermined rotational speed, the impeller 25 can pressurize the liquid hydrogen to a predetermined pressure. In this state, liquid hydrogen is also supplied to the bearing device 40, stabilizing the position of the rotating shaft 20 in both the axial and radial directions. Liquid hydrogen is supplied to the thrust bearing 44, and the thrust collar 22 is held in a position where it does not come into contact with the thrust bearing 44 in the axial direction via fluid pressure. In other words, by supplying high-pressure liquid hydrogen to the thrust bearing 44, the axial load on the rotating shaft 20 is absorbed by the thrust bearing 44.

[0048] After the drive process S14 is performed, the decommunication process S15 is performed. In the decommunication process S15, the switching unit 5 is operated to decommunicate the external sump 3 and the bearing device 40. That is, in the decommunication process S15, the bearing device 40 is decommunicated with the second pressure space 3A. The decommunication process S15 is performed after the rotating shaft 20 has reached a predetermined rotational speed. Even when the bearing device 40 is decommunicated with the second pressure space 3A, the bearing device 40 is supplied with two-stage pressurized liquid hydrogen. Therefore, even when the bearing device 40 is decommunicated with the second pressure space 3A, the bearing device 40 functions as a sliding bearing.

[0049] After the decommunication process S15 is performed, the drive stop process S16 is performed. In the drive stop process S16, the electric motor 30 is stopped, and the drive that rotates the rotating shaft 20 around axis O is stopped. When the drive of the electric motor 30 is stopped, the rotating shaft 20 is no longer subjected to an external force for rotation. Immediately after the electric motor 30 is stopped, the rotating shaft 20 continues to rotate around axis O due to inertia.

[0050] After the drive stop process S16 is performed, the stop communication process S17 is performed. In the stop communication process S17, the switching unit 5 is operated to connect the external sump 3 and the bearing device 40. That is, in the stop communication process S17, the bearing device 40 is connected to the second pressure space 3A. The stop communication process S17 is performed after the drive of the electric motor 30 is stopped, while the rotating shaft 20 continues to rotate. When the drive of the electric motor 30 is stopped, the rotational speed of the rotating shaft 20 gradually decreases and the rotation stops. As the rotational speed of the rotating shaft 20 decreases, the amount of liquid hydrogen supplied to the bearing device 40 by the impeller 25 also decreases. The stop communication process S17 is performed before the thrust collar 22 and the thrust bearing 44 come into contact in the axial direction. By connecting the bearing device 40 to the second pressure space 3A, liquid hydrogen is allowed to flow toward the second pressure space 3A. In other words, liquid hydrogen flows in the same manner as in the startup communication process S13, and the bearing device 40 functions as a sliding bearing even when the rotation of the rotating shaft 20 has completely stopped. When the rotation of the rotating shaft 20 has completely stopped, the liquefied gas pump 1 stops.

[0051] <Effects and Effects> As described above, the liquefied gas pump 1 is configured by the switching unit 5 to connect the bearing device 40 to the second pressure space 3A. The second pressure is lower than the first pressure. Therefore, liquid hydrogen is drawn in and circulated from the liquefied gas supply source 2, which is at the first pressure, to the second pressure space 3A. In other words, by creating a differential pressure so that it passes through the bearing device 40, static pressure is supplied to the bearing device 40. Therefore, by connecting the bearing device 40 to the second pressure space 3A, the bearing device 40 is supplied with static pressure and functions as a sliding bearing. That is, even when the rotating shaft 20 is not rotating around axis O, it is possible to supply static pressure to the bearing device 40. Since the liquefied gas pump 1 can be started and stopped while the thrust bearing 44 is functioning as a sliding bearing, friction between the thrust bearing 44 and the thrust collar 22 due to the rotation of the rotating shaft 20 can be suppressed. Similarly, friction between the radial bearing 41 and the rotating shaft 20 can also be suppressed. Therefore, according to the liquefied gas pump 1 of this embodiment, wear of the bearing device 40 and the rotating shaft 20 during starting and stopping can be suppressed.

[0052] According to the operating method S1 of this embodiment of the liquefied gas pump, the liquefied gas pump 1 is brought to a first pressure by supplying liquid hydrogen in the pre-cooling process S12. In the startup communication process S13, the bearing device 40 is brought into communication with the second pressure space 3A. The second pressure is lower than the first pressure. Therefore, liquefied gas flows from the first pressure space to the second pressure space 3A. Consequently, static pressure is supplied to the bearing device 40 as described above. With static pressure supplied to the bearing device 40, the thrust collar 22 connected to the rotating shaft 20 is separated from the thrust bearing 44. After the startup communication process S13, the drive process S14 is executed to rotate the rotating shaft 20 around the axis O. This makes it possible to suppress friction between the thrust bearing 44 and the thrust collar 22 when the liquefied gas pump 1 is started. Similarly, friction between the radial bearing 41 and the rotating shaft 20 can also be suppressed. Therefore, according to the operating method S1 of the liquefied gas pump of this embodiment, wear of the bearing device 40 and the rotating shaft 20 during startup can be suppressed.

[0053] Furthermore, according to the operating method S1 of the liquefied gas pump of this embodiment, in the non-communication process S15, the bearing device 40 is made non-communicating with the second pressure space 3A. That is, while the liquefied gas pump 1 is running, the bearing device 40 is made non-communicating with the second pressure space 3A. When the liquefied gas pump 1 is running, pressurized liquid hydrogen is supplied to the bearing device 40. Therefore, even without providing a differential pressure to the bearing device 40, the bearing device 40 functions as a sliding bearing. Thus, by making the bearing device 40 non-communicating with the second pressure space 3A while the liquefied gas pump 1 is running, leakage of liquid hydrogen into the second pressure space 3A can be suppressed.

[0054] Furthermore, according to the operating method S1 of the liquefied gas pump of this embodiment, the drive of the rotating shaft 20 is stopped in the drive stop step S16. In the stop communication step S17, the bearing device 40 is connected to the second pressure space 3A. Therefore, even if the drive of the rotating shaft 20 is stopped, liquefied gas flows from the bearing device 40 to the second pressure space 3A. That is, even if the rotational drive of the rotating shaft 20 is stopped, static pressure is supplied to the bearing device 40. Therefore, the rotation of the rotating shaft 20 is stopped while the thrust collar 22 remains axially separated from the thrust bearing 44. Thus, friction between the thrust bearing 44 and the thrust collar 22 when the liquefied gas pump 1 is stopped can be suppressed. Similarly, friction between the radial bearing 41 and the rotating shaft 20 can also be suppressed. Therefore, according to the operating method S1 of the liquefied gas pump of this embodiment, wear of the bearing device 40 and the rotating shaft 20 when stopped can be suppressed.

[0055] Furthermore, according to the liquefied gas pump 1 and the operating method S1 of this embodiment, wear of the bearing device 40 and the rotating shaft 20 can be suppressed, which also leads to improved maintainability of the liquefied gas pump 1.

[0056] Furthermore, the liquefied gas pump 1 and its operating method S1 are applicable to a variety of fluids. In addition, the liquefied gas pump 1 of this embodiment can pressurize liquid hydrogen. That is, the liquefied gas pump 1 and its operating method S1 of this embodiment are applicable to liquid hydrogen, which is at an even lower temperature than LNG.

[0057] <Other Embodiments> Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0058] For example, the communication passage 4 according to the embodiment may be provided separately in each of the bearing devices 40. Also, the radial bearing 41 does not need to be provided with communication passages 4B and 4C.

[0059] Furthermore, the bearing device 40 does not have to be configured solely to allow liquid hydrogen to be supplied at internal pressure by the liquefied gas supply source 2. In other words, the bearing device 40 may also be able to receive liquid hydrogen from sources other than the liquefied gas supply source 2. The liquid hydrogen supplied from sources other than the liquefied gas supply source 2 may be pressurized, for example, rather than at internal pressure.

[0060] Furthermore, the non-communication process S15 may be performed before the rotating shaft 20 reaches a predetermined rotational speed. If the bearing device 40 is supplied with fluid pressure sufficient for it to function as a sliding bearing, the non-communication process S15 may be performed before the rotating shaft 20 reaches a predetermined rotational speed.

[0061] Alternatively, the stop-time communication process S17 may be performed before the drive stop process S16. That is, while the rotating shaft 20 is being driven by the electric motor 30 to rotate, the switching unit 5 may be operated to connect the external sump 3 and the bearing device 40. This makes it possible to more reliably connect the bearing device 40 to the second pressure space 3A before the thrust bearing 44 and the thrust collar 22 come into contact.

[0062] <Note> The liquefied gas pump 1 and the operating method S1 of the liquefied gas pump described in each embodiment can be understood, for example, as follows.

[0063] (1) The liquefied gas pump 1 according to the first embodiment comprises a rotating shaft 20 that can rotate around an axis O, an impeller 25 integrally provided with the rotating shaft 20 and capable of pumping liquefied gas by rotating together with the rotating shaft 20, an electric motor 30 that rotates the rotating shaft 20 around the axis O, a bearing device 40 that supports the rotating shaft 20 so as to be rotatable around the axis O, a liquefied gas supply source 2 that can supply the liquefied gas to the bearing device 40 at a first pressure, and a switching unit 5 that can switch between a state in which the bearing device 40 is in communication with a space 3A at a second pressure lower than the first pressure and a state in which it is not in communication with the space 3A at the second pressure.

[0064] According to the above configuration, the switching unit 5 connects the bearing device 40 to the second pressure space 3A. The second pressure is lower than the first pressure. As a result, liquefied gas is drawn into the second pressure space 3A, and liquefied gas flows from the first pressure liquefied gas supply source 2 to the second pressure space 3A. Therefore, even when the rotating shaft 20 is not rotating around axis O, it is possible to supply static pressure to the bearing device 40. In this way, wear of the bearing device 40 during starting and stopping can be suppressed.

[0065] (2) The liquefied gas pump 1 relating to the second aspect is the liquefied gas pump 1 of (1), wherein the liquefied gas is liquid hydrogen.

[0066] (3) The third mode of operation S1 of the liquefied gas pump is a method of operating the liquefied gas pump 1, wherein the liquefied gas pump 1 comprises a rotating shaft 20 rotatable around axis O, an impeller 25 integrally provided on the rotating shaft 20 and capable of pumping liquefied gas by rotating together with the rotating shaft 20, an electric motor 30 that rotates the rotating shaft 20 around axis O, a bearing device 40 that supports the rotating shaft 20 so as to be rotatable around axis O, a liquefied gas supply source 2 capable of supplying the liquefied gas to the bearing device 40 at a first pressure, and the bearing device 40 A method for operating a liquefied gas pump S1, comprising a switching unit 5 capable of switching between a state in which the bearing device 40 is in communication with a space 3A at a second pressure lower than the first pressure and a state in which it is not in communication with the space 3A at the second pressure, includes a pre-cooling step S12 in which the liquefied gas is supplied to the flow path of the liquefied gas pump 1 at the first pressure; a startup communication step S13 in which the bearing device 40 is connected to the space 3A at the second pressure after the pre-cooling step S12; and a drive step S14 in which the rotating shaft 20 is rotated around the axis O after the startup communication step S13.

[0067] According to the above configuration, in the pre-cooling process S12, the liquefied gas pump 1 is brought to the first pressure. In the startup communication process S13, the bearing device 40 is brought into communication with the second pressure space 3A. The second pressure is lower than the first pressure. Therefore, liquefied gas flows from the first pressure space to the second pressure space 3A. Consequently, static pressure is supplied to the bearing device 40, and the bearing device 40 functions as a sliding bearing. After the startup communication process S13, by rotating the rotating shaft 20 around the axis O, wear of the bearing device 40 during the startup of the liquefied gas pump 1 can be suppressed.

[0068] (4) The fourth mode of operation S1 of the liquefied gas pump is the liquefied gas pump operation S1 of (3), further comprising a decommunication step S15 after the drive step S14, which causes the bearing device 40 to be decommunicated with the second pressure space 3A.

[0069] According to the above configuration, in the non-communication process S15, the bearing device 40 is made non-communicating with the second pressure space 3A. That is, while the liquefied gas pump 1 is running, the bearing device 40 is made non-communicating with the second pressure space 3A. Therefore, leakage of liquefied gas into the second pressure space 3A can be suppressed.

[0070] (5) A fifth method of operating a liquefied gas pump S1 is the method of operating a liquefied gas pump S1 of (3) or (4), further comprising, after the non-communication step S15, a drive stop step S16 for stopping the drive of the rotating shaft 20, and after the drive stop step S16, a stop-time communication step S17 for connecting the bearing device 40 to the second pressure space 3A.

[0071] According to the above configuration, the drive of the rotating shaft 20 is stopped in the drive stop process S16. In the stop communication process S17, the bearing device 40 is connected to the second pressure space 3A. Therefore, even when the drive of the rotating shaft 20 is stopped, liquefied gas flows from the bearing device 40 to the second pressure space 3A. That is, even when the drive of the rotating shaft 20 is stopped, static pressure is supplied to the bearing device 40. Therefore, the rotation of the rotating shaft 20 is stopped while the thrust collar 22 remains separated from the thrust bearing 44. Thus, wear of the thrust bearing 44 when the liquefied gas pump 1 is stopped can be suppressed. [Explanation of Symbols]

[0072] 1. Liquefied gas pump 2. Liquefied gas supply source 3 External Sump 3A Second pressure space 4, 4A, 4B, 4C communication channel 5. Switching section 6. Pump body 10 Casing 11 Suction part 12 Discharge part 20 Rotation axis 21 Rotating shaft body 22 Thrust Color 22A Top 22B Bottom 24 Inducers 25 Impeller 26 First stage impeller 27 Second stage impeller 28 Third stage impeller 30 Electric motor 31 stata 32 stator cores 35 coils 36 Rotor 38 Rotor Cores 40 Bearing device 41 Radial bearing 42 First radial bearing 43 Second radial bearing 44 Thrust bearing 45 Upper bearing body 45A Upper pocket 45B Upper Manifold 45C Upper communication passage 46 Lower bearing body 46A Lower pocket 46B Lower Manifold 46C Lower communication passage 80 Supply passage 81 First supply passage 82 Second supply passage 83 Third supply passage 84 Fourth supply passage 50 Sump 51 Outer flange 53 Liquid storage chamber 60 Supply pipe 61 Gas discharge pipe 62 Discharge pipe О axis S1 Operating method of liquefied gas pump S11 Preparation process S12 Pre-cooling process S13 Communication process at startup S14 Drive process S15 Non-communicating process S16 Drive stop process S17 Communication process at stop

Claims

1. A rotating shaft that can rotate around its axis, An impeller is integrally mounted on the aforementioned rotating shaft and rotates together with the aforementioned rotating shaft to pump liquefied gas under pressure, An electric motor that rotates the aforementioned rotating shaft around the aforementioned axis, A bearing device that supports the aforementioned rotating shaft so that it can rotate around the axis, The bearing device is provided with a liquefied gas supply source capable of supplying the liquefied gas at a first pressure, A switching unit capable of switching between a state in which the bearing device is in communication with a space having a second pressure lower than the first pressure and a state in which it is not in communication with the space having the second pressure, A liquefied gas pump equipped with [a specific feature].

2. The liquefied gas pump according to claim 1, wherein the liquefied gas is liquid hydrogen.

3. A method for operating a liquefied gas pump, The aforementioned liquefied gas pump is A rotating shaft that can rotate around its axis, An impeller is integrally mounted on the aforementioned rotating shaft and rotates together with the aforementioned rotating shaft to pump liquefied gas under pressure, An electric motor that rotates the aforementioned rotating shaft around the aforementioned axis, A bearing device that supports the aforementioned rotating shaft so that it can rotate around the axis, The bearing device is provided with a liquefied gas supply source capable of supplying the liquefied gas at a first pressure, A switching unit capable of switching between a state in which the bearing device is in communication with a space having a second pressure lower than the first pressure and a state in which it is not in communication with the space having the second pressure, In a method for operating the liquefied gas pump, comprising the following: A pre-cooling step in which the liquefied gas is supplied to the flow path of the liquefied gas pump at the first pressure, After the pre-cooling step, there is a startup communication step in which the bearing device is connected to the second pressure space, After the initial communication step, a drive step is performed to rotate the rotating shaft around the axis, A method for operating a liquefied gas pump, including [specific details omitted].

4. The method for operating a liquefied gas pump according to claim 3, further comprising a decommunication step of disconnecting the bearing device from the second pressure space after the driving step.

5. After the aforementioned decommunication step, a drive stop step is performed to stop the drive of the rotating shaft, The method for operating a liquefied gas pump according to claim 4, further comprising a stop-time communication step of connecting the bearing device to the second pressure space after the drive stop step.

Images