Centrifugal turbomachine

Abstract

A centrifugal turbomachine (1) according to one embodiment includes: a pair of impellers (2A, 2C) in which back surfaces (21) thereof face each other; a shaft (3) interposed between the impellers (2A, 2C); and a fluid bearing (7) that supports the shaft (3) in a non-contact state. The fluid bearing (7) includes a bearing pad (71) in which a plurality of pockets arranged in a circumferential direction are formed on an inner peripheral surface. The centrifugal turbomachine (1) further includes a seal component (8) interposed between the fluid bearing (7) and the high-pressure-side impeller (2A) of the impellers (2A, 2C). The seal component (8) forms a chamber with the bearing pad (71), and the bearing pad (71) is provided with at least one through-hole that penetrates the bearing pad (71) in the axial direction of the shaft (3).

Description

Title of Invention: CENTRIFUGAL TURBOMACHINE Technical Field

[0001] The present disclosure relates to a multistage centrifugal turbomachine. Background Art

[0002] Conventionally, multistage centrifugal turbomachines for a working fluid that is a liquid, such as radial turbines and centrifugal pumps, have been known. In such a centrifugal turbomachine, bladed wheels are mounted to a rotating shaft.

[0003] For example, Patent Literature 1 discloses an oilfield pump in which bladed wheels facing in the same direction are mounted to a rotating shaft, and the rotating shaft is supported, in a non-contact state, by fluid bearings that are located alternately with the bladed wheels. In Patent Literature 1, the fluid bearings are referred to as “hydrostatic bearings”.

[0004] Each fluid bearing includes an annular bearing pad that includes an inner peripheral surface facing an outer peripheral surface of the rotating shaft, and the inner peripheral surface of the bearing pad includes pockets that are located in a circumferential direction. That is, the inner peripheral surface of the bearing pad includes: a pair of axial lands that are positioned on both sides of the pockets in the axial direction of the rotating shaft; and circumferential lands positioned between the pockets.

[0005] In the oilfield pump of Patent Literature 1, target oil is led from one of adjacent bladed wheels to another through a passage, and the target oil is fed from the passage to the pockets of the fluid bearing. Citation List Patent Literature

[0006] PTL 1: Japanese Laid-Open Patent Application Publication No. 2020-197142 Summary of Invention Technical Problem

[0007] The oilfield pump of Patent Literature 1 is a low-pressure centrifugal turbomachine. In contrast, in a high-pressure centrifugal turbomachine, a back-to-back structure in which the facing direction of some bladed wheels is opposite to that of other bladed wheels may be adopted to reduce a thrust load exerted on the rotating shaft.

[0008] In the back-to-back structure, in a case where a fluid bearing is located between the bladed wheels whose back surfaces face each other, at one of the axial lands, a sufficient differential pressure cannot be obtained between an inflow end on the pocket side and an outflow end on the side opposite the pocket side, and high bearing performance cannot be obtained.

[0009] In view of the above, an object of the present disclosure is to provide a centrifugal turbomachine that makes it possible to obtain high bearing performance in a back-to-back structure. Solution to Problem

[0010] The present disclosure provides a multistage centrifugal turbomachine for a working fluid that is a liquid, the centrifugal turbomachine including: a pair of bladed wheels whose back surfaces face each other; a shaft located between the pair of bladed wheels; a fluid bearing that is supplied with the working fluid and that supports the shaft in a non-contact state, the fluid bearing including a bearing pad whose inner peripheral surface includes pockets that are located in a circumferential direction; and a seal located between a higher-pressure-side bladed wheel of the pair of bladed wheels and the fluid bearing, the seal forming a chamber between the seal and the bearing pad. The bearing pad includes at least one through-hole that extends through the bearing pad in an axial direction of the shaft. Advantageous Effects of Invention

[0011] The present disclosure provides a centrifugal turbomachine that makes it possible to obtain high bearing performance in a back-to-back structure. Brief Description of Drawings

[0012] [FIG. 1] FIG. 1 shows a schematic configuration of a centrifugal turbomachine that is a radial turbine according to Embodiment 1. [FIG. 2] FIG. 2 is a sectional view of the radial turbine. [FIG. 3] FIG. 3 is a sectional view taken along line III-III of FIG. 2. [FIG. 4] FIG. 4 is a sectional view taken along line IV-IV of FIG. 3. [FIG. 5] FIG. 5 shows a variation of the centrifugal turbomachine, corresponding to FIG. 4. [FIG. 6] FIG. 6 shows a schematic configuration of a centrifugal turbomachine that is a centrifugal pump according to Embodiment 2. [FIG. 7] FIG. 7 is a sectional view of the centrifugal pump. Description of Embodiments

[0013] <Embodiment 1> FIG. 1 shows a multistage centrifugal turbomachine 1 for a working fluid that is a liquid, according to Embodiment 1. The working fluid is not particularly limited to a specific type of fluid. For example, the working fluid may be cryogenic liquid hydrogen, LNG (Liquefied Natural Gas), liquid nitrogen, or liquid oxygen, or may be room-temperature oil.

[0014] In the present embodiment, the centrifugal turbomachine 1 is a radial turbine 1A, which absorbs power from a high-pressure working fluid and includes three bladed wheels. Alternatively, the number of bladed wheels included in the centrifugal turbomachine 1 may be two, or may be four or more.

[0015] The three bladed wheels are, specifically, a first bladed wheel 2A, a second bladed wheel 2B, and a third bladed wheel 2C. The first bladed wheel 2A, the second bladed wheel 2B, and the third bladed wheel 2C are mounted to a rotating shaft 12, and the rotating shaft 12 is coupled to a shaft of a power absorber 11. The power absorber 11 is, for example, a power generator, a blower, an oil pump, or an oil brake.

[0016] In the present embodiment, the second bladed wheel 2B is positioned closest to the power absorber 11; the third bladed wheel 2C is positioned farthest from the power absorber 11; and the first bladed wheel 2A is positioned between the second bladed wheel 2B and the third bladed wheel 2C. However, the positions of the first bladed wheel 2A, the second bladed wheel 2B, and the third bladed wheel 2C are not limited to these positions, and are suitably changeable.

[0017] The centrifugal turbomachine 1 includes: an inflow line 1a, through which the high- pressure working fluid is supplied to the first bladed wheel 2A; a first intermediate line 1b, which leads the working fluid whose pressure has been reduced by the first bladed wheel 2A to the second bladed wheel 2B; a second intermediate line 1c, which leads the working fluid whose pressure has been reduced by the second bladed wheel 2B to the third bladed wheel 2C; and an outflow line 1d, through which the working fluid whose pressure has been reduced by the third bladed wheel 2C is discharged.

[0018] The centrifugal turbomachine 1 adopts a back-to-back structure in which the first bladed wheel 2A and the second bladed wheel 2B face in the same direction, while the third bladed wheel 2C faces in a direction opposite to that of the first bladed wheel 2A and the second bladed wheel 2B. That is, the first bladed wheel 2A and the third bladed wheel 2C are a pair of bladed wheels whose back surfaces 21 face each other. Since the first bladed wheel 2A is positioned upstream of the third bladed wheel 2C, the first bladed wheel 2A is a bladed wheel on the higher-pressure side than the third bladed wheel 2C, and the third bladed wheel 2C is a bladed wheel on the lower-pressure side than the first bladed wheel 2A.

[0019] The centrifugal turbomachine 1 further includes: a fluid bearing 7, which supports, in a non-contact state, a shaft 3 located between the first bladed wheel 2A and the third bladed wheel 2C; and a branch line 1e, which is branched off from the inflow line 1a and connects to the fluid bearing 7. That is, the high-pressure working fluid supplied to the first bladed wheel 2A is also supplied to the fluid bearing 7 through the branch line 1e.

[0020] Next, with reference to FIG. 2, a specific structure of the radial turbine 1A, which is the centrifugal turbomachine 1, is described. The radial turbine 1A includes: a housing 4 surrounding the first bladed wheel 2A, the second bladed wheel 2B, and the third bladed wheel 2C; and a casing 5 accommodating the housing 4.

[0021] The rotating shaft 12 penetrates the second bladed wheel 2B, the first bladed wheel 2A, and the third bladed wheel 2C. A lock nut 13, which serves to hold the second bladed wheel 2B, the first bladed wheel 2A, and the third bladed wheel 2C, is fixed to the distal end of the rotating shaft 12.

[0022] In the present embodiment, a cylindrical portion 31, which protrudes from the back surface 21 of the third bladed wheel 2C along the rotating shaft 12, is integrated with the third bladed wheel 2C, and a cylindrical portion 32, which protrudes from the back surface 21 of the first bladed wheel 2A along the rotating shaft 12, is integrated with the first bladed wheel 2A. The distal end surfaces of the respective cylindrical portions 31 and 32 are in contact with each other, and these cylindrical portions 31 and 32 form the aforementioned shaft 3. Alternatively, the rotating shaft 12 may be exposed between the third bladed wheel 2C and the first bladed wheel 2A, and a part of the rotating shaft 12 may serve as the shaft 3.

[0023] Further, in the present embodiment, a cylindrical portion 33, which protrudes from a back surface 21 of the second bladed wheel 2B along the rotating shaft 12, is integrated with the second bladed wheel 2B. The distal end surface of the cylindrical portion 33 is in contact with the front-side end surface of the first bladed wheel 2A.

[0024] Each of the first bladed wheel 2A, the second bladed wheel 2B, and the third bladed wheel 2C includes: a hub including a concave curved surface that guides a radial flow into an axial flow; and blades protruding from the concave curved surface. Between the blades, there is a bent passage that is open both in the radial direction and the axial direction. In each bladed wheel, the side toward which the axial opening of the bent passage is open is the front side, and the side opposite thereto is the back side. That is, the back surface 21 is a surface facing the side opposite the axial opening of the bent passage.

[0025] The housing 4 includes, at positions corresponding to the first bladed wheel 2A, the second bladed wheel 2B, and the third bladed wheel 2C, respectively, convex curved surfaces facing the concave curved surfaces of the respective bladed wheels. The housing 4 further includes: a spiral inflow chamber 41 positioned around the first bladed wheel 2A; a spiral first relay chamber 42 positioned around the front side of the second bladed wheel 2B; a spiral second relay chamber 43 positioned around the third bladed wheel 2C; and an outflow opening 44 positioned on the front side of the third bladed wheel 2C.

[0026] The housing 4 further includes: an inflow passage 4a, which leads the working fluid from the inflow chamber 41 to the first bladed wheel 2A; an intermediate passage 4b, which leads the working fluid from the first bladed wheel 2A to the second bladed wheel 2B; an intermediate passage 4c, which leads the working fluid from the second bladed wheel 2B to the first relay chamber 42; and an intermediate passage 4d, which leads the working fluid from the second relay chamber 43 to the third bladed wheel 2C.

[0027] The inflow passage 4a extends radially inward from the inflow chamber 41. The inflow passage 4a includes nozzle vanes 61. The intermediate passage 4b includes: a first curved portion that is curved by 90 degrees from the front side of the first bladed wheel 2A; a first radially extending portion that extends radially outward from the first curved portion; a second curved portion that is curved by 180 degrees from the first radially extending portion; and a second radially extending portion that extends radially inward from the second curved portion. The second radially extending portion includes nozzle vanes 62.

[0028] The intermediate passage 4c includes: a curved portion that is curved by 90 degrees from the front side of the second bladed wheel 2B; and a radially extending portion that extends radially outward from the curved portion. The intermediate passage 4d extends radially inward from the second relay chamber 43. The intermediate passage 4d includes nozzle vanes 63.

[0029] The casing 5 includes: a cylindrical portion 5a extending in the axial direction of the rotating shaft 12; and a closing portion 5b, which closes one opening of the cylindrical portion 5a. The outer peripheral surface of the housing 4 is in contact with the cylindrical portion 5a, and the end surface of the housing 4 on the third bladed wheel 2C side is in contact with the closing portion 5b.

[0030] The casing 5 further includes: an inflow port 51 extending in the direction in which the spiral inflow chamber 41 extends; a first relay port 52 extending in the direction in which the spiral first relay chamber 42 extends; a second relay port 53 extending in the direction in which the spiral second relay chamber 43 extends; and an outflow port 54 continuous with the outflow opening 44. The inflow port 51, the first relay port 52, and the second relay port 53 are formed by respective tubular portions each protruding from the cylindrical portion 5a, and the outflow port 54 is formed by a tubular portion protruding from the closing portion 5b. The first relay port 52 and the second relay port 53 are connected to each other by a pipe 14.

[0031] The inflow line 1a in FIG. 1 is formed by the inflow port 51, the inflow chamber 41, and the inflow passage 4a, and the first intermediate line 1b is formed by the intermediate passage 4b. The second intermediate line 1c is formed by the intermediate passage 4c, the first relay chamber 42, the first relay port 52, the pipe 14, the second relay port 53, and the intermediate passage 4d. The outflow line 1d is formed by the outflow opening 44 and the outflow port 54.

[0032] The housing 4 includes a cylindrical supporting surface 45 between the third bladed wheel 2C and the first bladed wheel 2A, and the cylindrical supporting surface 45 has a greater diameter than that of the outer peripheral surface of the shaft 3. The supporting surface 45 forms a bearing chamber 46 together with the back surface 21 of the third bladed wheel 2C, the back surface 21 of the first bladed wheel 2A, and the outer peripheral surface of the shaft 3. In the present embodiment, the diameter of the supporting surface 45 is about the same as the diameter of the third bladed wheel 2C and the first bladed wheel 2A. However, the diameter of the supporting surface 45 is suitably changeable.

[0033] The fluid bearing 7 is located within the bearing chamber 46. Further, a seal 8 positioned between the fluid bearing 7 and the first bladed wheel 2A is also located within the bearing chamber 46.

[0034] The fluid bearing 7 includes an annular bearing pad 71, which is penetrated by the shaft 3. The bearing pad 71 is fixed to the supporting surface 45 of the housing 4.

[0035] As shown in FIG. 3, the bearing pad 71 includes an inner peripheral surface 72 facing the outer peripheral surface of the shaft 3. The diameter of the inner peripheral surface 72 of the bearing pad 71 is slightly greater than the diameter of the outer peripheral surface of the shaft 3, and there is a narrow gap between the outer peripheral surface of the shaft 3 and the inner peripheral surface 72 of the bearing pad 71.

[0036] The inner peripheral surface 72 of the bearing pad 71 includes pockets 73, which are located in a circumferential direction. In the present embodiment, the number of pockets 73 is four. However, the number of pockets 73 is not limited to four, but is suitably changeable.

[0037] As shown in FIG. 4, the inner peripheral surface 72 of the bearing pad 71 includes a pair of axial lands 74, which are positioned on both sides of the pockets 73 in the axial direction of the shaft 3. As shown in FIG. 3, the inner peripheral surface 72 includes circumferential lands 75, each of which is located between pockets 73. Each axial land 74 is a continuous region extending in the circumferential direction.

[0038] The bearing pad 71 includes the same number of lubrication passages 76 as the number of pockets 73. Each of the lubrication passages 76 extends from a corresponding one of the pockets 73 to the outer peripheral surface of the bearing pad 71. Each lubrication passage 76 includes a restrictor 77. The restrictor 77 may be an orifice or a capillary restrictor.

[0039] As shown in FIG. 2, the supporting surface 45 of the housing 4 includes an annular groove 47 at a position corresponding to the lubrication passages 76 of the bearing pad 71. The annular groove 47 is recessed radially outward. The housing 4 and the casing 5 include a supply passage 16 extending from the annular groove 47 to the outer peripheral surface of the cylindrical portion 5a of the casing 5. A supply pipe 15, through which the inflow port 51 and the supply passage 16 communicate with each other, is connected to the casing 5. The supply pipe 15, the supply passage 16, and the annular groove 47 form the branch line 1e.

[0040] In FIG. 1, the restrictors 77 are illustrated on the branch line 1e. In reality, the restrictors 77 are positioned within the fluid bearing 7 as described above. Further, although valves are located on the inflow line 1a and the branch line 1e as shown in FIG. 1, the illustration of these valves is omitted in FIG. 2.

[0041] As shown in FIG. 4, the seal 8 located within the bearing chamber 46 is fixed to the supporting surface 45 of the housing 4, and seals a narrow gap between the seal 8 and the outer peripheral surface of the shaft 3. The seal 8 serves, for example, as a gap seal, a labyrinth seal, or a hole-pattern seal.

[0042] The seal 8 forms a chamber 9 between the seal 8 and the bearing pad 71. In the present embodiment, a rib 81 protruding from the seal 8 toward the bearing pad 71 along the supporting surface 45 is integrated with the seal 8, and the chamber 9 is secured by the rib 81.

[0043] The bearing pad 71 includes at least one through-hole 78, which extends through the bearing pad 71 in the axial direction of the shaft 3. In the present embodiment, as shown in FIG. 3, the number of through-holes 78 is eight. However, the number of through-holes 78 is not limited to eight, but is suitably changeable.

[0044] A space facing the back surface 21 of the first bladed wheel 2A communicates with the inflow passage 4a through a gap between the first bladed wheel 2A and the housing 4, the gap being located around the first bladed wheel 2A. Accordingly, the pressure in the space is high pressure. A space facing the back surface 21 of the third bladed wheel 2C communicates with the intermediate passage 4d through a gap between the third bladed wheel 2C and the housing 4, the gap being located around the third bladed wheel 2C. Accordingly, the pressure in the space is the pressure that has been reduced by the second bladed wheel 2B.

[0045] If the seal 8 is absent, the pressure on one side of the fluid bearing 7 in the axial direction of the shaft 3 is high pressure, and the pressure on the other side of the fluid bearing 7 in the axial direction of the shaft 3 is the pressure that has been reduced by the second bladed wheel 2B. In this respect, in the present embodiment, the seal 8 is located between the fluid bearing 7 and the first bladed wheel 2A, and the bearing pad 71 includes the through-holes 78. Accordingly, the pressures on both sides of the fluid bearing 7 in the axial direction of the shaft 3 are substantially equal to each other. This makes it possible to secure, at both of the pair of axial lands 74 of the bearing pad 71, a sufficient differential pressure between an inflow end on the pocket 73 side and an outflow end on the side opposite the pocket 73 side. In other words, at each axial land 74, a pressure gradient between the inflow end and the outflow end is large. As a result, high stiffness and high damping performance of the fluid bearing 7 are achieved, which makes it possible to obtain high bearing performance.

[0046] <Variations> As shown in FIG. 5, within the bearing chamber 46, the seal 8 may be located as a first seal 8, and a second seal 82 may also be located between the fluid bearing 7 and the third bladed wheel 2C.

[0047] The second seal 82 is fixed to the supporting surface 45 of the housing 4, and seals a narrow gap between the second seal 82 and the outer peripheral surface of the shaft 3. The second seal 82 serves, for example, as a gap seal, a labyrinth seal, or a hole-pattern seal. The second seal 82 forms a chamber 91 between the second seal 82 and the bearing pad 71.

[0048] As shown in FIG. 4, in a case where a space between the third bladed wheel 2C on the lower-pressure side and the fluid bearing 7 is an open space, there is a risk that cavitation may occur in the working fluid that has leaked out through a narrow gap between the shaft 3 and the axial land 74, depending on the pressure in the open space. In this respect, by locating the second seal 82 between the third bladed wheel 2C and the fluid bearing 7, the pressures on both sides of the fluid bearing 7 are kept relatively high, which makes it possible to prevent the occurrence of such cavitation.

[0049] The variation shown in FIG. 5 is applicable also to the centrifugal turbomachine 1 according to Embodiment 2 described below.

[0050] <Embodiment 2> FIG. 6 shows the centrifugal turbomachine 1 according to Embodiment 2. In the present embodiment, the same components as those described in Embodiment 1 are denoted by the same reference signs as those used in Embodiment 1, and repeating the same descriptions will be avoided.

[0051] In the present embodiment, the centrifugal turbomachine 1 is a centrifugal pump 1B, which performs work on a working fluid to increase the pressure of the working fluid. In the present embodiment, the centrifugal turbomachine 1 includes three bladed wheels. Alternatively, the number of bladed wheels may be two, or may be four or more

[0052] The three bladed wheels are a first bladed wheel 2D, a second bladed wheel 2E, and a third bladed wheel 2F. The first bladed wheel 2D, the second bladed wheel 2E, and the third bladed wheel 2F are mounted to the rotating shaft 12, and the rotating shaft 12 is coupled to an input shaft of an electric motor 17.

[0053] In the present embodiment, the second bladed wheel 2E is positioned closest to the electric motor 17; the first bladed wheel 2D is positioned farthest from the electric motor 17; and the third bladed wheel 2F is positioned between the second bladed wheel 2E and the first bladed wheel 2D. However, the positions of the first bladed wheel 2D, the second bladed wheel 2E, and the third bladed wheel 2F are not limited to these positions, and are suitably changeable.

[0054] The centrifugal turbomachine 1 includes: an inflow line 1f, through which a low- pressure working fluid is supplied to the first bladed wheel 2D; a first intermediate line 1g, which leads the working fluid whose pressure has been increased by the first bladed wheel 2D to the second bladed wheel 2E; a second intermediate line 1h, which leads the working fluid whose pressure has been increased by the second bladed wheel 2E to the third bladed wheel 2F; and an outflow line 1i, through which the working fluid whose pressure has been increased by the third bladed wheel 2F is discharged.

[0055] The centrifugal turbomachine 1 adopts a back-to-back structure in which the second bladed wheel 2E and the third bladed wheel 2F face in the same direction, while the first bladed wheel 2D faces in a direction opposite to that of the second bladed wheel 2E and the third bladed wheel 2F. That is, the first bladed wheel 2D and the third bladed wheel 2F are a pair of bladed wheels whose back surfaces 21 face each other. Since the first bladed wheel 2D is positioned upstream of the third bladed wheel 2F, the first bladed wheel 2D is a bladed wheel on the lower-pressure side than the third bladed wheel 2F, and the third bladed wheel 2F is a bladed wheel on the higher-pressure side than the first bladed wheel 2D.

[0056] The centrifugal turbomachine 1 further includes: the fluid bearing 7, which supports, in a non-contact state, the shaft 3 located between the first bladed wheel 2D and the third bladed wheel 2F; and a branch line 1j, which is branched off from the outflow line 1i and connects to the fluid bearing 7. That is, the fluid whose pressure has been increased by the third bladed wheel 2F, i.e., high-pressure working fluid, is supplied to the fluid bearing 7 through the branch line 1j.

[0057] Next, with reference to FIG. 7, a specific structure of the centrifugal pump 1B, which is the centrifugal turbomachine 1, is described. The centrifugal pump 1B includes: a housing 4A surrounding the first bladed wheel 2D, the second bladed wheel 2E, and the third bladed wheel 2F; and a casing 5A accommodating the housing 4A.

[0058] The rotating shaft 12 penetrates the second bladed wheel 2E, the third bladed wheel 2F, and the first bladed wheel 2D. The lock nut 13, which serves to hold the second bladed wheel 2E, the third bladed wheel 2F, and the first bladed wheel 2D, is fixed to the distal end of the rotating shaft 12.

[0059] In the present embodiment, the cylindrical portion 31, which protrudes from the back surface 21 of the first bladed wheel 2D along the rotating shaft 12, is integrated with the first bladed wheel 2D, and the cylindrical portion 32, which protrudes from the back surface 21 of the third bladed wheel 2F along the rotating shaft 12, is integrated with the first bladed wheel 2A. The distal end surfaces of the respective cylindrical portions 31 and 32 are in contact with each other, and these cylindrical portions 31 and 32 form the aforementioned shaft 3. Alternatively, the rotating shaft 12 may be exposed between the first bladed wheel 2D and the third bladed wheel 2F, and a part of the rotating shaft 12 may serve as the shaft 3.

[0060] Further, in the present embodiment, the cylindrical portion 33, which protrudes from the back surface 21 of the second bladed wheel 2E along the rotating shaft 12, is integrated with the second bladed wheel 2E. The distal end surface of the cylindrical portion 33 is in contact with the front-side end surface of the third bladed wheel 2F.

[0061] Each of the first bladed wheel 2D, the second bladed wheel 2E, and the third bladed wheel 2F includes: a hub including a concave curved surface that guides an axial flow into a radial flow; and blades protruding from the concave curved surface. Between the blades, there is a bent passage that is open both in the radial direction and the axial direction. In each bladed wheel, the side toward which the axial opening of the bent passage is open is the front side, and the side opposite thereto is the back side. That is, the back surface 21 is a surface facing the side opposite the axial opening of the bent passage.

[0062] The housing 4A includes, at positions corresponding to the first bladed wheel 2D, the second bladed wheel 2E, and the third bladed wheel 2F, respectively, convex curved surfaces facing the concave curved surfaces of the respective bladed wheels. The housing 4A further includes: an inflow opening 49a positioned on the front side of the first bladed wheel 2D; a spiral first relay chamber 49b positioned around the first bladed wheel 2D; a spiral second relay chamber 49c positioned around the front side of the second bladed wheel 2E; and a spiral outflow chamber 49d positioned around the third bladed wheel 2F.

[0063] The housing 4A further includes: an intermediate passage 4e, which leads the working fluid from the first bladed wheel 2D to the first relay chamber 49b; an intermediate passage 4f, which leads the working fluid from the second relay chamber 49c to the second bladed wheel 2E; an intermediate passage 4g, which leads the working fluid from the second bladed wheel 2E to the third bladed wheel 2F; and an outflow passage 4h, which leads the working fluid from the third bladed wheel 2F to the outflow chamber 49d.

[0064] The intermediate passage 4e extends radially outward from the first bladed wheel 2D. The intermediate passage 4e includes diffuser vanes 64. The intermediate passage 4f includes: a radially extending portion that extends radially inward from the second relay chamber 49c; and a curved portion that is curved by 90 degrees from the radially extending portion toward the front side of the second bladed wheel 2B.

[0065] The intermediate passage 4g includes: a first radially extending portion that extends radially outward from the second bladed wheel 2E; a first curved portion that is curved by 180 degrees from the first radially extending portion; a second radially extending portion that extends radially inward from the first curved portion; and a second curved portion that is curved by 90 degrees from the second radially extending portion toward the front side of the third bladed wheel 2F. The first radially extending portion includes diffuser vanes 65. The outflow passage 4h extends radially outward from the third bladed wheel 2F. The outflow passage 4h includes diffuser vanes 66.

[0066] The casing 5A includes: the cylindrical portion 5a extending in the axial direction of the rotating shaft 12; and the closing portion 5b, which closes one opening of the cylindrical portion 5a. The outer peripheral surface of the housing 4A is in contact with the cylindrical portion 5a, and the end surface of the housing 4A on the first bladed wheel 2D side is in contact with the closing portion 5b.

[0067] The casing 5A further includes: an inflow port 55 continuous with the inflow opening 49a; a first relay port 56 extending in the direction in which the spiral first relay chamber 49b extends; a second relay port 57 extending in the direction in which the spiral second relay chamber 49c extends; and an outflow port 58 extending in the direction in which the spiral outflow chamber 49d extends. The inflow port 55 is formed by a tubular portion protruding from the closing portion 5b, and the first relay port 56, the second relay port 57, and the outflow port 58 are formed by respective tubular portions each protruding from the cylindrical portion 5a. The first relay port 56 and the second relay port 57 are connected to each other by the pipe 14.

[0068] The inflow line 1f shown in FIG. 6 is formed by the inflow port 55 and the inflow opening 49a. The first intermediate line 1g is formed by the intermediate passage 4e, the first relay chamber 49b, the first relay port 56, the pipe 14, the second relay port 57, and the intermediate passage 4f. The second intermediate line 1h is formed by the intermediate passage 4g. The outflow line 1d is formed by the outflow passage 4h, the outflow chamber 49d, and the outflow port 58.

[0069] Similar to Embodiment 1, the housing 4A includes the supporting surface 45, which forms the bearing chamber 46 together with the back surface 21 of the third bladed wheel 2C, the back surface 21 of the first bladed wheel 2A, and the outer peripheral surface of the shaft 3. The fluid bearing 7 and the seal 8 are located within the bearing chamber 46. The seal 8 is located between the fluid bearing 7 and the third bladed wheel 2F. A sectional view taken along line III-III of FIG. 7 in Embodiment 2 would be the same as the sectional view taken along line III-III in Embodiment 1.

[0070] The supporting surface 45 of the housing 4A includes the annular groove 47 at a position corresponding to the lubrication passages 76 of the bearing pad 71. The annular groove 47 is recessed radially outward. The housing 4A and the casing 5A include the supply passage 16 extending from the annular groove 47 to the outer peripheral surface of the cylindrical portion 5a of the casing 5A. The supply pipe 15, through which the outflow port 58 and the supply passage 16 communicate with each other, is connected to the casing 5A. The supply pipe 15, the supply passage 16, and the annular groove 47 form the branch line 1j.

[0071] The restrictors 77, which are included in the respective lubrication passages 76 of the bearing pad 71, are illustrated on the branch line 1j in FIG. 6. However, in reality, the restrictors 77 are positioned within the fluid bearing 7 as described in Embodiment 1. Further, although valves are located on the outflow line 1i and the branch line 1j as shown in FIG. 6, the illustration of these valves is omitted in FIG. 2.

[0072] As shown in FIG. 3 and FIG. 4, similar to Embodiment 1, the chamber 9 is located between the bearing pad 71 of the fluid bearing 7 and the seal 8, and the bearing pad 71 includes at least one through-hole 78. Accordingly, the same advantageous effects as those of Embodiment 1 can be obtained. In the present embodiment, the pressure in a space facing the back surface 21 of the third bladed wheel 2F is high pressure, while the pressure in a space facing the back surface 21 of the first bladed wheel 2D is low pressure.

[0073] <Other Embodiments> The present disclosure is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the present disclosure.

[0074] <Summary> The present disclosure provides, as a first aspect, a multistage centrifugal turbomachine for a working fluid that is a liquid, the centrifugal turbomachine including: a pair of bladed wheels whose back surfaces face each other; a shaft located between the pair of bladed wheels; a fluid bearing that is supplied with the working fluid and that supports the shaft in a non-contact state, the fluid bearing including a bearing pad whose inner peripheral surface includes pockets that are located in a circumferential direction; and a seal located between a higher-pressure-side bladed wheel of the pair of bladed wheels and the fluid bearing, the seal forming a chamber between the seal and the bearing pad. The bearing pad includes at least one through-hole that extends through the bearing pad in an axial direction of the shaft.

[0075] According to the above configuration, pressures on both sides of the fluid bearing in the axial direction of the shaft are substantially equal to each other. This makes it possible to secure, at both of a pair of axial lands positioned on both sides of each pocket, a sufficient differential pressure between an inflow end on the pocket side and an outflow end on the side opposite the pocket side. As a result, high stiffness and high damping performance of the fluid bearing are achieved, which makes it possible to obtain high bearing performance.

[0076] As a second aspect, in the first aspect, for example, the centrifugal turbomachine may be a radial turbine, and the centrifugal turbomachine may further include: an inflow line through which the working fluid is supplied to the higher-pressure-side bladed wheel of the pair of bladed wheels; and a branch line that is branched off from the inflow line and that connects to the fluid bearing.

[0077] As a third aspect, in the first aspect, for example, the centrifugal turbomachine may be a centrifugal pump, and the centrifugal turbomachine may further include: an outflow line through which the working fluid whose pressure has been increased by the higher-pressure-side bladed wheel of the pair of bladed wheels is discharged; and a branch line that is branched off from the outflow line and that connects to the fluid bearing.

[0078] As a fourth aspect, in any of the first to third aspects, for example, the centrifugal turbomachine may further include a housing including a cylindrical supporting surface that forms a bearing chamber together with the back surfaces of the pair of bladed wheels and an outer peripheral surface of the shaft, wherein the seal may be fixed to the supporting surface, and may seal a gap between the seal and the outer peripheral surface of the shaft.

[0079] As a fifth aspect, in any of the first to fourth aspects, the seal may be a first seal, and the centrifugal turbomachine may further include a second seal located between a lower-pressure-side bladed wheel of the pair of bladed wheels and the fluid bearing, the second seal forming a chamber between the second seal and the bearing pad. In a case where a space between the lower-pressure-side bladed wheel and the fluid bearing is an open space, there is a risk that cavitation may occur in the working fluid that has leaked out through a narrow gap between the shaft and an axial land, depending on the pressure in the open space. In this respect, by locating the second seal between the lower-pressure-side bladed wheel and the fluid bearing, the pressures on both sides of the fluid bearing are kept relatively high, which makes it possible to prevent the occurrence of such cavitation.

[0080] As a sixth aspect, in any of the first to fifth aspects, for example, the working fluid may be liquid hydrogen, LNG, liquid nitrogen, or liquid oxygen.

Claims

1. A multistage centrifugal turbomachine for a working fluid that is a liquid, thecentrifugal turbomachine including:a pair of bladed wheels whose back surfaces face each other;a shaft located between the pair of bladed wheels;a fluid bearing that is supplied with the working fluid and that supports the shaft in a non-contact state, the fluid bearing including a bearing pad whose inner peripheral surface includes pockets that are located in a circumferential direction; anda seal located between a higher-pressure-side bladed wheel of the pair of bladed wheels and the fluid bearing, the seal forming a chamber between the seal and the bearing pad, whereinthe bearing pad includes at least one through-hole that extends through the bearing pad in an axial direction of the shaft.

2. The centrifugal turbomachine according to claim 1, whereinthe centrifugal turbomachine is a radial turbine,the centrifugal turbomachine further including:an inflow line through which the working fluid is supplied to the higher-pressureside bladed wheel of the pair of bladed wheels; anda branch line that is branched off from the inflow line and that connects to the fluid bearing.

3. The centrifugal turbomachine according to claim 1, whereinthe centrifugal turbomachine is a centrifugal pump,the centrifugal turbomachine further including:an outflow line through which the working fluid whose pressure has been increased by the higher-pressure-side bladed wheel of the pair of bladed wheels is discharged; anda branch line that is branched off from the outflow line and that connects to the fluid bearing.

4. The centrifugal turbomachine according to any one of claims 1 to 3, further including a housing including a cylindrical supporting surface that forms a bearing chamber together with the back surfaces of the pair of bladed wheels and an outer peripheral surface ofthe shaft, whereinthe seal is fixed to the supporting surface, and seals a gap between the seal and the outer peripheral surface of the shaft.

5. The centrifugal turbomachine according to any one of claims 1 to 3, whereinthe seal is a first seal,the centrifugal turbomachine further including a second seal located between a lower-pressure-side bladed wheel of the pair of bladed wheels and the fluid bearing, the second seal forming a chamber between the second seal and the bearing pad.

6. The centrifugal turbomachine according to any one of claims 1 to 3, whereinthe working fluid is liquid hydrogen, LNG, liquid nitrogen, or liquid oxygen.

Images