Centrifugal turbo machine

Abstract

To provide a centrifugal turbo machine that can obtain high bearing performance in a back-to-back structure.SOLUTION: A centrifugal turbo machine 1 according to an embodiment comprises a pair of impellers 2A and 2C where back surfaces 21 are opposed to each other, a shaft part 3 interposed between the impellers 2A and 2C, and a fluid bearing 7 supporting the shaft part 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 in an inner peripheral surface. The centrifugal turbo machine 1 also includes a seal component 8 interposed between the impeller 2A on a high-pressure side out of the impellers 2A and 2C and the fluid bearing 7. The seal component 8 forms a chamber between itself and the bearing pad 71. The bearing pad 71 is provided with at least one through hole penetrating the bearing pad 71 in an axial direction of the shaft part 3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to multi-stage centrifugal turbomachines. [Background technology]

[0002] 2. Description of the Related Art Conventionally, multi-stage centrifugal turbomachines for liquid working fluids, such as radial turbines and centrifugal pumps, have been known. In such centrifugal turbomachines, multiple impellers are attached to a rotating shaft.

[0003] For example, Patent Document 1 discloses an oil field pump in which multiple impellers are attached to a rotating shaft in the same direction, and the rotating shaft is supported in a non-contact state by multiple fluid bearings arranged alternately with the impellers. In Patent Document 1, the fluid bearings are referred to as "hydrostatic bearings."

[0004] Each hydrodynamic bearing includes an annular bearing pad having an inner peripheral surface facing the outer peripheral surface of the rotating shaft, and a plurality of pockets arranged in the circumferential direction on the inner peripheral surface of the bearing pad. That is, the inner peripheral surface of the bearing pad includes a pair of axial lands located on either side of the pocket in the axial direction of the rotating shaft, and a plurality of circumferential lands between the pockets.

[0005] In the oil field pump of Patent Document 1, the target oil is guided from one of the adjacent impellers to the other through a flow path, and is supplied from the flow path to the pockets of the fluid bearing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-197142 Summary of the Invention [Problem to be solved by the invention]

[0007] The oil field pump in Patent Document 1 is a low-pressure centrifugal turbomachine. In contrast, high-pressure centrifugal turbomachines often employ a back-to-back structure in which some impellers are oriented in the opposite direction to the other impellers in order to reduce the thrust load acting on the rotating shaft.

[0008] In a back-to-back structure, when a fluid bearing is placed between impellers with their backs facing each other, a sufficient pressure difference cannot be obtained between the inlet end on the pocket side and the outlet end on the opposite side of the pocket in one of the axial land portions, and high bearing performance cannot be obtained.

[0009] Therefore, an object of the present disclosure is to provide a centrifugal turbomachine that can obtain high bearing performance in a back-to-back structure. [Means for solving the problem]

[0010] The present disclosure provides a multi-stage centrifugal turbomachine for a liquid working fluid, comprising: a pair of impellers with their backs facing each other; a shaft portion interposed between the pair of impellers; a fluid bearing that is supplied with the working fluid and supports the shaft portion in a non-contact state, the fluid bearing including a bearing pad having a plurality of pockets arranged circumferentially on its inner surface; and a sealing component that is interposed between the high-pressure side impeller of the pair of impellers and the fluid bearing and forms a chamber between the bearing pad and the sealing component, wherein the bearing pad has at least one through-hole that passes through the bearing pad in the axial direction of the shaft portion. [Effects of the Invention]

[0011] According to the present disclosure, a centrifugal turbomachine capable of achieving high bearing performance in a back-to-back configuration is provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a centrifugal turbomachine, which is a radial turbine, according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the radial turbine. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a view corresponding to FIG. 4 of a modified centrifugal turbomachine. [Figure 6] FIG. 10 is a schematic configuration diagram of a centrifugal turbomachine, which is a centrifugal pump, according to a second embodiment. [Figure 7] FIG. 2 is a cross-sectional view of the centrifugal pump. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment 1 shows a multi-stage centrifugal turbomachine 1 for use with a liquid working fluid according to a first embodiment. The working fluid is not particularly limited. For example, the working fluid may be cryogenic liquid hydrogen, LNG (Liquefied Natural Gas), liquid nitrogen, liquid oxygen, or the like, or may be room temperature oil, or the like.

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

[0015] The three impellers are a first impeller 2A, a second impeller 2B, and a third impeller 2C. The first impeller 2A, the second impeller 2B, and the third impeller 2C are attached to a rotating shaft 12, which is connected to the shaft of a power absorber 11. The power absorber 11 is, for example, a generator, a blower, an oil pump, an oil brake, or the like.

[0016] In this embodiment, the second impeller 2B is located closest to the power absorber 11, the third impeller 2C is located farthest from the power absorber 11, and the first impeller 2A is located between the second impeller 2B and the third impeller 2C. However, the positions of the first impeller 2A, second impeller 2B, and third impeller 2C are not limited to this and can be changed as appropriate.

[0017] The centrifugal turbomachine 1 includes an inlet line 1a that supplies high-pressure working fluid to the first impeller 2A, a first intermediate line 1b that guides the working fluid depressurized by the first impeller 2A to the second impeller 2B, a second intermediate line 1c that guides the working fluid depressurized by the second impeller 2B to the third impeller 2C, and an outlet line 1d that discharges the working fluid depressurized by the third impeller 2C.

[0018] The centrifugal turbomachine 1 employs a back-to-back structure, with the first impeller 2A and the second impeller 2B facing in the same direction, while the third impeller 2C faces in the opposite direction to the first impeller 2A and the second impeller 2B. In other words, the first impeller 2A and the third impeller 2C form a pair of impellers with their back surfaces 21 facing each other. As the first impeller 2A is located upstream of the third impeller 2C, the first impeller 2A is on the higher pressure side than the third impeller 2C, and the third impeller 2C is on the lower pressure side than the first impeller 2A.

[0019] The centrifugal turbomachine 1 also includes a fluid bearing 7 that supports the shaft portion 3 interposed between the first impeller 2A and the third impeller 2C in a non-contact manner, and a branch line 1e that branches off from the inlet line 1a and leads to the fluid bearing 7. In other words, the high-pressure working fluid supplied to the first impeller 2A is also supplied to the fluid bearing 7 through the branch line 1e.

[0020] Next, a specific structure of a radial turbine 1A, which is a centrifugal turbomachine 1, will be described with reference to Fig. 2. The radial turbine 1A includes a housing 4 that surrounds the first impeller 2A, second impeller 2B, and third impeller 2C described above, and a casing 5 that accommodates the housing 4.

[0021] The above-mentioned rotating shaft 12 passes through the second impeller 2B, the first impeller 2A, and the third impeller 2C, and a lock nut 13 is fixed to the tip of the rotating shaft 12 to hold the second impeller 2B, the first impeller 2A, and the third impeller 2C.

[0022] In this embodiment, a cylindrical portion 31 protruding from the back surface 21 of the third impeller 2C along the rotary shaft 12 is provided integrally with the third impeller 2C, and a cylindrical portion 32 protruding from the back surface 21 of the first impeller 2A along the rotary shaft 12 is provided integrally with the first impeller 2A. The tip surfaces of the cylindrical portions 31, 32 abut against each other, and these cylindrical portions 31, 32 form the above-mentioned shaft portion 3. However, the rotary shaft 12 may be exposed between the third impeller 2C and the first impeller 2A, and the shaft portion 3 may be formed from a part of the rotary shaft 12.

[0023] In this embodiment, a cylindrical portion 33 is integrally formed on the second impeller 2B, protruding from the rear surface 21 of the second impeller 2B along the rotation shaft 12. The tip surface of the cylindrical portion 33 abuts against the front end surface of the first impeller 2A.

[0024] Each of the first impeller 2A, the second impeller 2B, and the third impeller 2C includes a hub with a concave curved surface that guides radial flow to axial flow, and multiple blades protruding from the concave curved surface. Between the blades, curved flow passages that open in the radial and axial directions are formed. In each impeller, the front side is the direction in which the axial openings of the curved flow passages open, and the back side is the side opposite the direction in which the axial openings of the curved flow passages open. In other words, the back side 21 mentioned above is the surface facing away from the axial openings of the curved flow passages.

[0025] The housing 4 has convex curved surfaces at positions corresponding to the first impeller 2A, second impeller 2B, and third impeller 2C that face the concave curved surfaces of the impellers. The housing 4 also includes a spiral inlet chamber 41 located around the first impeller 2A, a spiral first relay chamber 42 located around the front side of the second impeller 2B, a spiral second relay chamber 43 located around the third impeller 2C, and an outlet opening 44 located on the front side of the third impeller 2C.

[0026] Furthermore, the housing 4 includes an inlet flow path 4a that guides the working fluid from the inlet chamber 41 to the first impeller 2A, an intermediate flow path 4b that guides the working fluid from the first impeller 2A to the second impeller 2B, an intermediate flow path 4c that guides the working fluid from the second impeller 2B to the first relay chamber 42, and an intermediate flow path 4d that guides the working fluid from the second relay chamber 43 to the third impeller 2C.

[0027] The inlet flow passage 4a extends radially inward from the inlet chamber 41 and is provided with a plurality of nozzle vanes 61. The intermediate flow passage 4b ​​includes a first curved portion that curves 90 degrees from the front side of the first impeller 2A, a first radially extending portion that extends radially outward from the first curved portion, a second curved portion that curves 180 degrees from the first radially extending portion, and a second radially extending portion that extends radially inward from the second curved portion. A plurality of nozzle vanes 62 is provided in the second radially extending portion.

[0028] The intermediate flow passage 4c includes a curved portion that curves 90 degrees from the front side of the second impeller 2B and a radially extending portion that extends radially outward from the curved portion. The intermediate flow passage 4d extends radially inward from the second relay chamber 43 and is provided with a plurality of nozzle vanes 63.

[0029] The casing 5 includes a cylindrical portion 5a extending in the axial direction of the rotary shaft 12 and a closing portion 5b that closes one opening of the cylindrical portion 5a. The outer peripheral surface of the housing 4 abuts against the cylindrical portion 5a, and the end face of the housing 4 on the third impeller 2C side abuts against the closing portion 5b.

[0030] Furthermore, the casing 5 includes an inlet port 51 extending in the extension direction of the spiral inlet chamber 41, a first relay port 52 extending in the extension direction of the spiral first relay chamber 42, a second relay port 53 extending in the extension direction of the spiral second relay chamber 43, and an outlet port 54 continuous with the outlet opening 44. The inlet port 51, the first relay port 52, the second relay port 53, and the outlet port 54 are each formed by a tubular portion extending from the cylindrical portion 5a. The first relay port 52 and the second relay port 53 are connected by piping 14.

[0031] 1, the inlet line 1a is composed of an inlet port 51, an inlet chamber 41, and an inlet flow path 4a, the first intermediate line 1b is composed of an intermediate flow path 4b, the second intermediate line 1c is composed of an intermediate flow path 4c, a first relay chamber 42, a first relay port 52, a pipe 14, a second relay port 53, and an intermediate flow path 4d, and the outlet line 1d is composed of an outlet opening 44 and an outlet port 54.

[0032] The housing 4 includes a cylindrical support surface 45 between the third impeller 2C and the first impeller 2A, the diameter of which is larger than the outer circumferential surface of the shaft portion 3. The support surface 45 forms a bearing chamber 46 together with the back surface 21 of the third impeller 2C, the back surface 21 of the first impeller 2A, and the outer circumferential surface of the shaft portion 3. In this embodiment, the diameter of the support surface 45 is approximately the same as the diameters of the third impeller 2C and the first impeller 2A, but the diameter of the support surface 45 can be changed as appropriate.

[0033] The above-mentioned fluid bearing 7 is disposed in a bearing chamber 46. Also disposed in the bearing chamber 46 is a seal component 8 interposed between the fluid bearing 7 and the first impeller 2A.

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

[0035] 3, the bearing pad 71 has an inner peripheral surface 72 that faces the outer peripheral surface of the shaft portion 3. The diameter of the inner peripheral surface 72 of the bearing pad 71 is slightly larger than the diameter of the outer peripheral surface of the shaft portion 3, and a narrow gap is formed between the outer peripheral surface of the shaft portion 3 and the inner peripheral surface 72 of the bearing pad 71.

[0036] A plurality of pockets 73 are formed in the circumferential direction on the inner peripheral surface 72 of the bearing pad 71. In this embodiment, the number of pockets 73 is four, but the number of pockets 73 is not limited to this and can be changed as appropriate.

[0037] The inner peripheral surface 72 of the bearing pad 71 includes a pair of axial lands 74 located on both sides of a pocket 73 in the axial direction of the shaft portion 3 as shown in Fig. 4, and also includes a plurality of circumferential lands 75 between the pockets 73 as shown in Fig. 3. Each axial land 74 is a continuous area in the circumferential direction.

[0038] The bearing pad 71 is provided with lubrication passages 76, the number of which is equal to the number of pockets 73. Each lubrication passage 76 extends from the corresponding pocket 73 to the outer circumferential surface of the bearing pad 71. Each lubrication passage 76 is provided with a restriction 77. The restriction 77 may be an orifice or a capillary restriction.

[0039] 2, an annular groove 47 recessed radially outward is formed in the support surface 45 of the housing 4 at a position corresponding to the lubrication passage 76 of the bearing pad 71. The housing 4 and the casing 5 are also provided with a supply passage 16 extending from the annular groove 47 to the outer circumferential surface of the cylindrical portion 5a of the casing 5. The casing 5 is further connected to a supply pipe 15 that connects the inlet port 51 and the supply passage 16. The supply pipe 15, the supply passage 16, and the annular groove 47 form the branch line 1e described above.

[0040] Although the orifice 77 is depicted in the branch line 1e in Fig. 1, the actual position of the orifice 77 is within the fluid bearing 7, as described above. Also, although valves are provided in the inlet line 1a and the branch line 1e in Fig. 1, these valves are omitted in Fig. 2.

[0041] 4, the seal component 8 disposed in the bearing chamber 46 is fixed to the support surface 45 of the housing 4 and seals the narrow gap formed between the seal component 8 and the outer circumferential surface of the shaft portion 3. The seal provided by the seal component 8 is, for example, a gap seal, a labyrinth seal, or a hole pattern seal.

[0042] The seal component 8 forms a chamber 9 between itself and the bearing pad 71. In this embodiment, a rib 81 that protrudes from the seal component 8 toward the bearing pad 71 along the support surface 45 is provided integrally with the seal component 8, and the chamber 9 is secured by the rib 81.

[0043] The bearing pad 71 is provided with at least one through hole 78 that passes through the bearing pad 71 in the axial direction of the shaft portion 3. In this embodiment, the number of through holes 78 is eight as shown in Fig. 3, but the number of through holes 78 is not limited to this and can be changed as appropriate.

[0044] The space facing the back surface 21 of the first impeller 2A is at high pressure because it communicates with the inlet flow passage 4a through a gap formed between the first impeller 2A and the housing 4. The space facing the back surface 21 of the third impeller 2C is at the pressure after being reduced by the second impeller 2B because it communicates with the intermediate flow passage 4d through a gap formed between the third impeller 2C and the housing 4.

[0045] Without the seal component 8, the pressure on one side of the hydrodynamic bearing 7 in the axial direction of the shaft portion 3 would be high, and the pressure on the other side would be the pressure after pressure reduction by the second impeller 2B. In contrast, in this embodiment, the seal component 8 is disposed between the hydrodynamic bearing 7 and the first impeller 2A, and the bearing pad 71 is provided with a through-hole 78, so the pressure on both sides of the hydrodynamic bearing 7 in the axial direction of the shaft portion 3 is approximately equal. As a result, a sufficient pressure difference can be ensured between the inlet end on the pocket 73 side and the outlet end on the opposite side from the pocket 73 at each of the pair of axial land portions 74 of the bearing pad 71. In other words, the pressure gradient between the inlet end and the outlet end at each axial land portion 74 is large. As a result, the rigidity and damping performance of the hydrodynamic bearing 7 are improved, resulting in high bearing performance.

[0046] <Modification> As shown in FIG. 5, a seal component 8 may be arranged in the bearing chamber 46 as a first seal component 8, and a second seal component 82 may be arranged between the fluid bearing 7 and the third impeller 2C.

[0047] The second seal component 82 is fixed to the support surface 45 of the housing 4 and seals a narrow gap formed between the second seal component 82 and the outer circumferential surface of the shaft portion 3. The seal provided by the second seal component 82 may be, for example, a gap seal, a labyrinth seal, or a hole pattern seal. In addition, the second seal component 82 forms a chamber 91 between itself and the bearing pad 71.

[0048] 4, if there is an open space between the third impeller 2C on the low-pressure side and the fluid bearing 7, the pressure in the open space may cause cavitation in the working fluid leaking through the narrow gap between the shaft portion 3 and the axial land portion 74. In contrast, if a second seal component 82 is disposed between the third impeller 2C and the fluid bearing 7, the pressure on both sides of the fluid bearing 7 is kept relatively high, thereby preventing the occurrence of such cavitation.

[0049] The modified example shown in FIG. 5 can also be applied to a centrifugal turbomachine 1 according to a second embodiment, which will be described later.

[0050] Second Embodiment 6 shows a centrifugal turbomachine 1 according to a second embodiment. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0051] In this embodiment, the centrifugal turbomachine 1 is a centrifugal pump 1B that applies work to a working fluid to increase its pressure. In this embodiment, the centrifugal turbomachine 1 includes three impellers, but the number of impellers may be two or four or more.

[0052] The three impellers are a first impeller 2D, a second impeller 2E, and a third impeller 2F. The first impeller 2D, the second impeller 2E, and the third impeller 2F are attached to a rotating shaft 12, and the rotating shaft 12 is connected to the input shaft of an electric motor 17.

[0053] In this embodiment, the second impeller 2E is located closest to the electric motor 17, the first impeller 2D is located farthest from the electric motor 17, and the third impeller 2F is located between the second impeller 2E and the first impeller 2D. However, the positions of the first impeller 2D, second impeller 2E, and third impeller 2F are not limited to this and can be changed as appropriate.

[0054] The centrifugal turbomachine 1 includes an inlet line 1f that supplies low-pressure working fluid to the first impeller 2D, a first intermediate line 1g that guides the working fluid pressurized by the first impeller 2D to the second impeller 2E, a second intermediate line 1h that guides the working fluid pressurized by the second impeller 2E to the third impeller 2F, and an outlet line 1i that discharges the working fluid pressurized by the third impeller 2F.

[0055] The centrifugal turbomachine 1 employs a back-to-back structure, in which the second impeller 2E and the third impeller 2F face in the same direction, while the first impeller 2D faces in the opposite direction to the second impeller 2E and the third impeller 2F. In other words, the first impeller 2D and the third impeller 2F form a pair of impellers with their back surfaces 21 facing each other. As the first impeller 2D is located upstream of the third impeller 2F, the first impeller 2D is an impeller on the lower pressure side than the third impeller 2F, and the third impeller 2F is an impeller on the higher pressure side than the first impeller 2D.

[0056] The centrifugal turbomachine 1 also includes a fluid bearing 7 that supports the shaft portion 3 interposed between the first impeller 2D and the third impeller 2F in a non-contact manner, and a branch line 1j that branches off from the above-mentioned outflow line 1i and leads to the fluid bearing 7. In other words, the high-pressure working fluid pressurized by the third impeller 2F is supplied to the fluid bearing 7 through the branch line 1j.

[0057] 7, a specific structure of a centrifugal pump 1B, which is a centrifugal turbomachine 1, will be described. The centrifugal pump 1B includes a housing 4A that surrounds the first impeller 2D, second impeller 2E, and third impeller 2F described above, and a casing 5A that accommodates the housing 4A.

[0058] The above-mentioned rotating shaft 12 passes through the second impeller 2E, the third impeller 2F, and the first impeller 2D, and a lock nut 13 is fixed to the tip of the rotating shaft 12 to hold the second impeller 2E, the third impeller 2F, and the first impeller 2D.

[0059] In this embodiment, a cylindrical portion 31 protruding from the back surface 21 of the first impeller 2D along the rotary shaft 12 is provided integrally with the first impeller 2D, and a cylindrical portion 32 protruding from the back surface 21 of the third impeller 2F along the rotary shaft 12 is provided integrally with the first impeller 2A. The tip surfaces of the cylindrical portions 31, 32 abut against each other, and these cylindrical portions 31, 32 form the above-mentioned shaft portion 3. However, the rotary shaft 12 may be exposed between the first impeller 2D and the third impeller 2F, and the shaft portion 3 may be formed from a part of the rotary shaft 12.

[0060] In this embodiment, a cylindrical portion 33 is integrally formed on the second impeller 2E and protrudes from the rear surface 21 of the second impeller 2E along the rotation shaft 12. The tip surface of the cylindrical portion 33 abuts against the front end surface of the third impeller 2F.

[0061] Each of the first impeller 2D, the second impeller 2E, and the third impeller 2F includes a hub with a concave curved surface that guides axial flow into radial flow, and multiple blades protruding from the concave curved surface. Between the blades, curved flow passages that open in the radial and axial directions are formed. In each impeller, the front side is the direction in which the axial openings of the curved flow passages open, and the back side is the side opposite the direction in which the axial openings of the curved flow passages open. In other words, the back side 21 mentioned above is the surface facing away from the axial openings of the curved flow passages.

[0062] The housing 4A has convex curved surfaces at positions corresponding to the first impeller 2D, the second impeller 2E, and the third impeller 2F, which face the concave curved surfaces of the impellers. The housing 4A also includes an inlet opening 49a located on the front side of the first impeller 2D, a spiral first relay chamber 49b located around the first impeller 2D, a spiral second relay chamber 49c located around the front side of the second impeller 2E, and a spiral outlet chamber 49d located around the third impeller 2F.

[0063] Furthermore, the housing 4A includes an intermediate flow path 4e that guides the working fluid from the first impeller 2D to the first relay chamber 49b, an intermediate flow path 4f that guides the working fluid from the second relay chamber 49c to the second impeller 2E, an intermediate flow path 4g that guides the working fluid from the second impeller 2E to the third impeller 2F, and an outlet flow path 4h that guides the working fluid from the third impeller 2F to the outlet chamber 49d.

[0064] The intermediate flow passage 4e extends radially outward from the first impeller 2D, and is provided with a plurality of diffuser vanes 64. The intermediate flow passage 4f includes a radially extending portion that extends radially inward from the second relay chamber 49c, and a curved portion that curves 90 degrees from the radially extending portion toward the front side of the second impeller 2B.

[0065] The intermediate flow passage 4g includes a first radially extending portion extending radially outward from the second impeller 2E, a first curved portion bending 180 degrees from the first radially extending portion, a second radially extending portion extending radially inward from the first curved portion, and a second curved portion bending 90 degrees from the second radially extending portion toward the front side of the third impeller 2F. A plurality of diffuser vanes 65 are provided in the first radially extending portion. The outlet flow passage 4h extends radially outward from the third impeller 2F, and a plurality of diffuser vanes 66 are provided in the outlet flow passage 4h.

[0066] The casing 5A includes a cylindrical portion 5a extending in the axial direction of the rotary shaft 12 and a closing portion 5b that closes one opening of the cylindrical portion 5a. The outer peripheral surface of the housing 4A abuts against the cylindrical portion 5a, and the end face of the housing 4A on the first impeller 2D side abuts against the closing portion 5b.

[0067] Furthermore, casing 5A includes an inlet port 55 continuous with inlet opening 49a, a first relay port 56 extending in the extension direction of spiral-shaped first relay chamber 49b, a second relay port 57 extending in the extension direction of spiral-shaped second relay chamber 49c, and an outlet port 58 extending in the extension direction of spiral-shaped outlet chamber 49d. Inlet port 55, first relay port 56, second relay port 57, and outlet port 58 are each formed by a tubular portion extending from cylindrical portion 5a. First relay port 56 and second relay port 57 are connected by piping 14.

[0068] 6, the inlet line 1f is composed of the inlet port 55 and the inlet opening 49a, the first intermediate line 1g is composed of the intermediate flow path 4e, the first relay chamber 49b, the first relay port 56, the piping 14, the second relay port 57, and the intermediate flow path 4f, the second intermediate line 1h is composed of the intermediate flow path 4g, and the outlet line 1d is composed of the outlet flow path 4h, the outlet chamber 49d, and the outlet port 58.

[0069] As in the first embodiment, the housing 4A includes a support surface 45 that forms a bearing chamber 46 together with the back surface 21 of the third impeller 2C, the back surface 21 of the first impeller 2A, and the outer circumferential surface of the shaft portion 3, and the fluid dynamic bearing 7 and the seal component 8 are disposed within the bearing chamber 46. The seal component 8 is interposed between the fluid dynamic bearing 7 and the third impeller 2F. Note that the cross-sectional view taken along line III-III in Figure 7 is the same as that of the first embodiment.

[0070] An annular groove 47 recessed radially outward is formed in the support surface 45 of the housing 4A at a position corresponding to the lubrication passage 76 of the bearing pad 71. The housing 4A and the casing 5A are also provided with a supply passage 16 extending from the annular groove 47 to the outer circumferential surface of the cylindrical portion 5a of the casing 5A. A supply pipe 15 is connected to the casing 5A, connecting the outlet port 58 with the supply passage 16. The supply pipe 15, the supply passage 16, and the annular groove 47 form the branch line 1j described above.

[0071] 6, the throttles 77 provided in each lubrication flow path 76 of the bearing pad 71 are depicted on the branch line 1j, but the actual position of the throttles 77 is inside the fluid bearing 7, as explained in the first embodiment. Also, in FIG. 6, valves are provided in the outflow line 1i and the branch line 1j, but these valves are omitted in FIG. 2.

[0072] 3 and 4, similar to the first embodiment, a chamber 9 is formed between the bearing pad 71 of the fluid bearing 7 and the seal component 8, and the bearing pad 71 is provided with at least one through-hole 78. Therefore, the same effects as those of the first embodiment can be obtained. In this embodiment, the space facing the back surface 21 of the third impeller 2F is at high pressure, while the space facing the back surface 21 of the first impeller 2D is at low pressure.

[0073] <Other embodiments> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0074] <Summary> In a first aspect, the present disclosure provides a multi-stage centrifugal turbomachine for a liquid working fluid, comprising: a pair of impellers with their backs facing each other; a shaft portion interposed between the pair of impellers; a fluid bearing that is supplied with the working fluid and supports the shaft portion in a non-contact state, the fluid bearing including a bearing pad having a plurality of pockets arranged circumferentially on its inner surface; and a sealing component that is interposed between the high-pressure side impeller of the pair of impellers and the fluid bearing and forms a chamber between the bearing pad and the sealing component, wherein the bearing pad has at least one through-hole that passes through the bearing pad in the axial direction of the shaft portion.

[0075] With the above configuration, the pressure on both sides of the hydrodynamic bearing in the axial direction of the shaft portion is approximately equal, so that a sufficient pressure difference can be ensured between the inlet end on the pocket side and the outlet end on the opposite side of the pocket in each of the pair of axial lands located on both sides of the pocket, thereby improving the rigidity and damping performance of the hydrodynamic bearing and achieving high bearing performance.

[0076] As a second aspect, in the first aspect, for example, the centrifugal turbomachine may be a radial turbine, and may further include an inlet line that supplies the working fluid to the impeller on the higher pressure side of the pair of impellers, and a branch line that branches off from the inlet line and leads to the fluid bearing.

[0077] As a third aspect, in the first aspect, for example, the centrifugal turbomachine may be a centrifugal pump, and may further include an outlet line for discharging the working fluid pressurized by the higher-pressure impeller of the pair of impellers, and a branch line branching from the outlet line and leading 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 support surface that forms a bearing chamber together with the back surfaces of the pair of impellers and the outer peripheral surface of the shaft portion, and the seal component may be fixed to the support surface to seal between the seal component and the outer peripheral surface of the shaft portion.

[0079] As a fifth aspect, in any of the first to fourth aspects, the seal component may be a first seal component, and the centrifugal turbomachine may further include a second seal component interposed between the low-pressure impeller of the pair of impellers and the hydrodynamic bearing and forming a chamber between the bearing pad. If there is an open space between the low-pressure impeller and the hydrodynamic bearing, the pressure in the open space may cause cavitation in the working fluid leaking through a narrow gap between the shaft portion and the axial land portion. In contrast, if a second seal component is disposed between the low-pressure impeller and the hydrodynamic bearing, the pressure on both sides of the hydrodynamic bearing is maintained at a relatively high level, thereby preventing 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. [Explanation of symbols]

[0081] 1. Centrifugal turbomachinery 1A Radial Turbine 1B centrifugal pump 1a Inlet line 1e Branch Line 1i Outflow line 1j Branch line 2A,2B,2C,2D,2E,2F Impeller 21 Back 3 Shaft section 4. Housing 44 Support surface 45 Bearing chamber 7. Fluid bearings 71 Bearing pad 72 Inner surface 73 Pocket 74 Axial land 75 Circumferential land 78 through holes 8 Seal parts, first seal part 82 Second seal part 9,91 Chamber

Claims

1. 1. A multi-stage centrifugal turbomachine for a liquid working fluid, comprising: a pair of impellers whose back surfaces face each other; a shaft portion interposed between the pair of impellers; a fluid bearing that is supplied with the working fluid and supports the shaft portion in a non-contact state, the fluid bearing including a bearing pad having a plurality of pockets formed on an inner peripheral surface thereof and arranged in a circumferential direction; a seal component that is interposed between the high-pressure side impeller of the pair of impellers and the fluid bearing and forms a chamber between the impeller and the bearing pad; The centrifugal turbomachine, wherein the bearing pad is provided with at least one through hole passing through the bearing pad in the axial direction of the shaft portion.

2. the centrifugal turbomachine is a radial turbine; an inlet line that supplies the working fluid to the impeller on the high-pressure side of the pair of impellers; The centrifugal turbomachine according to claim 1 , further comprising: a branch line branching from the inlet line and leading to the hydrodynamic bearing.

3. the centrifugal turbomachine is a centrifugal pump; an outflow line for discharging the working fluid pressurized by the impeller on the higher pressure side of the pair of impellers; The centrifugal turbomachine according to claim 1 , further comprising: a branch line branching from the outflow line and leading to the hydrodynamic bearing.

4. a housing including a cylindrical support surface that forms a bearing chamber together with the rear surfaces of the pair of impellers and the outer circumferential surface of the shaft portion; The centrifugal turbomachine according to claim 1 , wherein the seal part is fixed to the support surface and seals between the seal part and an outer circumferential surface of the shaft portion.

5. the sealing component is a first sealing component, 4. The centrifugal turbomachine according to claim 1, further comprising a second seal component interposed between the low-pressure side impeller of the pair of impellers and the fluid bearing, and forming a chamber between the bearing pad and the second seal component.

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

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