Stator blade segment and steam turbine having the same

Abstract

A stationary vane segment has an outer vane ring extending in a circumferential direction, a stationary vane extending radially inward from the outer vane ring, and a seal member. The stationary vane has a cavity formed in an inner portion thereof and communicating with a surface thereof. The outer vane ring has a vane ring main body and two vane ring protrusions. The two vane ring protrusions project radially outward from a gas passage surface of the vane ring main body and oppose each other at intervals in an axial direction, and a drain recovery space is formed between the two vane ring protrusions in common with a housing. The vane ring main body has a vane surface drain recovery passage that communicates the cavity with the drain recovery space. One of the two vane ring protrusions has a seal surface. The seal member is disposed between a portion of the housing and the seal surface of the one vane ring protrusion and is in contact with the seal surface.

Description

TECHNICAL FIELD

[0001] The present application relates to a vane segment and a steam turbine provided with the vane segment.

[0002] This application claims priority based on Japanese Patent Application No. 2020-136665 filed on August 13, 2020 in Japan, and the contents thereof are incorporated herein. BACKGROUND

[0003] A steam turbine generally has a rotor that rotates around an axis, a plurality of vane segments, and a casing that covers an outer periphery of the rotor and the plurality of vane segments. The rotor has a rotor shaft that is long in an axial direction in which the axis extends, and a plurality of blade rows that are installed to an outer periphery of the rotor shaft. The plurality of vane segments are arranged in the casing in the axial direction. The vane segment has one or more vane rows, an inner shroud that is installed to a radially inner side of the one or more vane rows, and an outer shroud that is installed to a radially outer side of the one or more vane rows. The vane row is composed of a plurality of vanes that are arranged in a circumferential direction. The plurality of vane rows are respectively arranged on an upstream side of the axis with respect to any of the plurality of blade rows.

[0004] A dryness of steam that flows into the casing gradually decreases as the steam flows in a steam flow path toward a downstream side of the axis. Therefore, sometimes, steam drain adheres to surfaces of the plurality of vanes that constitute a vane row on a downstream side of the axis among the plurality of vane rows. A part of the steam drain flows toward the downstream side of the axis, and sometimes collides with surfaces of the plurality of blades that constitute a blade row present on the downstream side of the axis of the vane row, and damages the blades. Therefore, for example, a steam turbine described in Patent Literature 1 has a drain recovery mechanism that recovers the steam drain.

[0005] The vane described in Patent Literature 1 has a cavity formed in an inside of the vane, and a vane face drain passage that connects a surface of the vane and the cavity. The outer shroud and the casing commonly form a space in which the steam drain that flows into the cavity of the vane is stored, with respect to each other. The steam drain stored in the space is discharged to the outside of the casing. The drain recovery mechanism is composed of the cavity, the vane face drain passage, and the space.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent No. 6163299 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] As described in the above patent document 1, when the outer blade ring and the casing collectively form a space for storing steam drainages as with the steam turbine, if the sealability of the gap between the outer blade ring and the casing is low, the amount of leakage of steam and steam drainages from the gap becomes large. In this case, in order to recover most of the steam drainages adhering to the blade surfaces of the stator blades, it is necessary to cause most of the steam to flow into the space together with the steam drainages, and the recovery efficiency of the steam drainages decreases.

[0011] Therefore, an object of the present application is to provide a technology capable of improving the recovery efficiency of steam drainages.

[0012] Means for solving technical problems

[0013] A stator blade segment as a means for achieving the object has an outer blade ring extending in a circumferential direction with respect to an axis, a plurality of stator blades extending from the outer blade ring toward a radially inner side with respect to the axis and arranged in the circumferential direction, and a sealing member that is a member different from the outer blade ring. The plurality of stator blades each has a cavity formed in an inside thereof and a blade surface drainage passage that connects a surface thereof and the cavity. The outer blade ring has a blade ring main body and two blade ring protrusions. The blade ring main body has a gas passage surface extending in the circumferential direction and facing the radially inner side, a reverse gas passage surface extending in the circumferential direction and having a back-to-back relationship with the gas passage surface, and a blade surface drainage recovery passage. The two blade ring protrusions protrude from the reverse gas passage surface toward a radially outer side with respect to the axis and extend in the circumferential direction, and are spaced apart from each other in an axis direction in which the axis extends, and collectively form a drainage recovery space with a casing present on an outer circumferential side of the blade ring main body between the two blade ring protrusions. The blade surface drainage recovery passage extends from the cavity toward the radially outer side and opens at a position between the two blade ring protrusions in the reverse gas passage surface. One of the two blade ring protrusions has a sealing surface. The sealing member is disposed between a part of the casing and the sealing surface of the one blade ring protrusion and is in contact with the sealing surface.

[0014] In the present mode, steam drainage attached to the blade surface of the stationary blade flows into the drainage recovery space through the blade surface drainage passage and the cavity. In the present mode, the seal member is arranged between a part of the casing and a seal surface of one blade ring protrusion, so the sealability between the casing and one blade ring protrusion is improved. Therefore, even if there is a pressure difference between the drainage recovery space and the space adjacent to the drainage recovery space which are formed by the casing and the outer blade ring, the pressure difference can be maintained, and the outflow of steam from one of the two adjacent spaces to the other space can be suppressed. Therefore, in the present mode, the discharge of steam which is not drainage can be suppressed, and the steam drainage is guided into the drainage recovery space.

[0015] A steam turbine as one mode for achieving the object includes the stationary blade segment of the one mode, and a casing covering the outer peripheral side of the stationary blade segment. The casing has a casing main body separated from the stationary blade segment toward the radially outer side, and extending along the circumferential direction and covering the outer peripheral side of the stationary blade segment, at least one casing protrusion, and a drainage discharge passage. The drainage discharge passage extends from the drainage recovery space toward the radially outer side and opens on the outer peripheral surface of the casing main body. The at least one casing protrusion protrudes from the casing main body toward the radially inner side and extends along the circumferential direction so as to form the drainage recovery space with the outer blade ring between the two blade ring protrusions more radially outward than the anti-gas passage surface. A part of the at least one casing protrusion overlaps the one of the two blade ring protrusions and the other of the two blade ring protrusions in a position in the radial direction with respect to the axis and is located more axially downstream than the other of the two blade ring protrusions in a position on the axially downstream side of the two sides of the axis. The part of the at least one casing protrusion has a casing other-side seal surface toward the axially upstream side. The other of the two blade ring protrusions has a blade ring other-side seal surface toward the axially downstream side and contactable with the casing other-side seal surface. Another part of the at least one casing protrusion has a casing one-side seal surface contactable with the seal member. The one of the two blade ring protrusions has a blade ring one-side seal surface opposite the casing one-side seal surface at a separation interval and serving as the seal surface. The seal member is arranged between the casing one-side seal surface and the blade ring one-side seal surface.

[0016] The stationary blade segment receives a force toward the downstream side of the axis from steam flowing in the steam flow path in the driving of the steam turbine. Therefore, the stationary blade segment wants to relatively move toward the downstream side of the axis with respect to the casing. Therefore, the blade ring other side seal surface moves toward the downstream side of the axis in contact with the casing other side seal surface. Therefore, in the present mode, the sealability between the portion of the at least one casing protrusion and the other blade ring protrusion is high, and leakage of steam from between the portion of the at least one casing protrusion and the other blade ring protrusion can be suppressed.

[0017] The seal member is arranged between the casing one side seal surface of the other portion of the at least one casing protrusion and the blade ring one side seal surface of the one blade ring protrusion. Therefore, in the present mode, even if the one blade ring protrusion moves toward the downstream side of the axis with respect to the other portion of the at least one casing protrusion due to the driving of the steam turbine, the sealability between the other portion of the at least one casing protrusion and the one blade ring protrusion is high, and leakage of steam from between the other portion of the at least one casing protrusion and the one blade ring protrusion can be suppressed.

[0018] Therefore, in the present mode, even if a pressure difference exists between the drain water recovery space commonly formed by the casing and the outer blade ring and the space adjacent to the drain water recovery space, the pressure difference can be maintained, and leakage of steam from one of the two adjacent spaces to the other can be suppressed.

[0019] Inventive Effects

[0020] In one mode of the present application, the recovery efficiency of steam drain water can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a cross-sectional view of a steam turbine in one embodiment of the present application.

[0022] Figure 2 is a main part cross-sectional view of an inner casing and a stationary blade segment in a first embodiment of the present application.

[0023] Figure 3 is a main part cross-sectional view of an inner casing and a stationary blade segment in a second embodiment of the present application.

[0024] Figure 4 is a main part cross-sectional view of an inner casing and a stationary blade segment in a first modified example of the first embodiment of the present application.

[0025] Figure 5 is a main part cross-sectional view of an inner casing and a stationary blade segment in a second modified example of the first embodiment of the present application. DETAILED DESCRIPTION

[0026] Hereinafter, an embodiment of a stationary blade segment and a steam turbine provided with the stationary blade segment according to the present application will be described.

[0027] "Embodiment of a steam turbine"

[0028] Reference Figure 1 A steam turbine according to the present embodiment will be described.

[0029] The steam turbine according to the present embodiment is a two split-flow exhaust type steam turbine. Therefore, the steam turbine ST is provided with a first steam turbine section 10a and a second steam turbine section 10b. The first steam turbine section 10a and the second steam turbine section 10b are each provided with a rotor 11 that rotates around an axis Ar, a casing 20 that covers the rotor 11, a plurality of stationary blade segments 17 fixed to the casing 20, and a steam inlet pipe 19. Hereinafter, a direction in which the axis Ar extends will be referred to as an axial direction Da, a circumferential direction around the axis Ar will be referred to as a circumferential direction Dc, and a direction perpendicular to the axis Ar will be referred to as a radial direction Dr. Furthermore, on the radial direction Dr, the side of the axis Ar will be referred to as a radially inner side Dri, and the side opposite thereto will be referred to as a radially outer side Dro.

[0030] The steam inlet pipe 19 is shared by the first steam turbine section 10a and the second steam turbine section 10b. In the first steam turbine section 10a, components other than the steam inlet pipe 19 are arranged on one side of the steam inlet pipe 19 in the axial direction Da. Also, in the second steam turbine section 10b, components other than the steam inlet pipe 19 are arranged on the other side of the steam inlet pipe 19 in the axial direction Da. In each of the steam turbine sections 10a and 10b, on the aforementioned axial direction Da, the side of the steam inlet pipe 19 will be referred to as an axial upstream side Dau, and the side opposite thereto will be referred to as an axial downstream side Dad.

[0031] The structure of the first steam turbine section 10a is substantially the same as that of the second steam turbine section 10b. Therefore, the first steam turbine section 10a will mainly be described hereinafter.

[0032] The rotor 11 has a rotor shaft 12 that extends in the axial direction Da around the axis Ar, and a plurality of blade rows 13 mounted to the rotor shaft 12. The rotor 11 is supported by a bearing 18 so as to be rotatable around the axis Ar. The plurality of blade rows 13 are arranged in the axial direction Da. Each of the blade rows 13 is composed of a plurality of blades arranged in the circumferential direction Dc. The rotor 11 of the first steam turbine section 10a and the rotor 11 of the second steam turbine section 10b are located on the same axis Ar, are connected to each other, and rotate integrally around the axis Ar.

[0033] The casing 20 has an inner casing (or simply, casing) 30, an outer casing 21, and a drain casing 23. The inner casing 30 forms a substantially conical space with the axis Ar as the center. A plurality of vane segments 17 are arranged along the axis direction Da on the inner peripheral side of the inner casing 30. The inner casing 30 is formed of, for example, SS400 which is one of steel materials, and the vane segments 17 are formed of, for example, SC450 which is one of carbon steel castings and has higher corrosion resistance against steam than the inner casing 30.

[0034] The vane segments 17 have one or more vane rows 17s, an inner vane ring 17i installed on the radially inner side Dri of the one or more vane rows 17s, and an outer vane ring 17o installed on the radially outer side Dro of the one or more vane rows 17s. The vane segments 17 on the most upstream side Dau of the axis among the plurality of vane segments 17 have a plurality of vane rows 17s. On the other hand, the vane segments 17 on the most downstream side Dad of the axis have one vane row 17s. The vane row 17s is composed of a plurality of vanes arranged in the circumferential direction Dc. The plurality of vane rows 17s are respectively arranged on the upstream side Dau of the axis of any one of the plurality of blade rows 13. The inner vane ring 17i and the outer vane ring 17o each extend in the circumferential direction Dc. The outer vane ring 17o is installed on the inner casing 30.

[0035] The outer casing 21 is cylindrical with the axis Ar as the center. The inner casing 30 is arranged on the inner peripheral side of the outer casing 21. The inner peripheral side of the outer casing 21 and the outer peripheral side of the inner casing 30 form a casing inner space 21s. A drain discharge passage 22 that discharges steam stored in the casing inner space 21s to a drain space 23s described later is formed in the outer casing 21 at a position directly below the axis Ar.

[0036] The drain casing 23 has a diffuser 24, a link ring 25, a downstream end plate 26d, an upstream end plate 26u, and a side peripheral plate 27.

[0037] The diffuser 24 is annular with respect to the axis Ar, and forms a diffuser space 24s that gradually expands toward the radially outer side Dro as it goes toward the axis downstream side Dad. Steam that flows out from the last stage blade row 13f of the rotor 11 flows into the diffuser space 24s. In addition, the last stage blade row 13f is a blade row 13 that is disposed at a position closest to the axis downstream side Dad among the plurality of blade rows 13. The diffuser 24 has an outer diffuser (or steam guide, vane) 24o that defines the edge of the radially outer side Dro of the diffuser space 24s, and an inner diffuser (or bearing cone) 24i that defines the edge of the radially inner side Dri of the diffuser space 24s. The outer diffuser 24o is annular in cross section perpendicular to the axis Ar, and expands gradually toward the radially outer side Dro as it goes toward the axis downstream side Dad. The inner diffuser 24i is also annular in cross section perpendicular to the axis Ar, and also expands gradually toward the radially outer side Dro as it goes toward the axis downstream side Dad.

[0038] The link ring 25 is annular with the axis Ar as the center. The link ring 25 covers the outer peripheral side of the last stage blade row 13f. The link ring 25 is attached to the outer casing 21. The axis upstream side Dau end of the outer diffuser 24o is connected to the link ring 25. Also, the axis downstream side Dad end of the outer diffuser 24o is connected to the axis downstream side Dad end of the outer casing 21. The inner diffuser 24i is connected to the downstream side end plate 26d.

[0039] The exhaust casing 23 has an exhaust port 28. The exhaust port 28 opens from the inside toward the radially outer side Dro, that is, the vertically downward direction. A condenser Co that causes steam to be restored to water is connected to the exhaust port 28. Thus, the steam turbine ST of the present embodiment is a down exhaust type condensing steam turbine. The downstream side end plate 26d, the upstream side end plate 26u, and the side peripheral plate 27 of the exhaust casing 23 form an exhaust space 23s that communicates with the diffuser space 24s. The exhaust space 23s extends along the circumferential direction Dc with respect to the axis Ar in the outer periphery of the diffuser 24, and guides steam that flows in from the diffuser space 24s to the exhaust port 28.

[0040] The downstream side end plate 26d extends from the edge of the radially outer side Dro of the inner diffuser 24i toward the radially outer side Dro, and defines the edge of the axis downstream side Dad of the exhaust space 23s. The downstream side end plate 26d is substantially perpendicular with respect to the axis Ar. The portion of the downstream side end plate 26d that is closer to the upper side than the axis Ar is substantially semicircular in shape when viewed from the axis direction Da. On the other hand, the portion of the downstream side end plate 26d that is closer to the lower side than the axis Ar is substantially rectangular in shape when viewed from the axis direction Da. The lower edge of the downstream side end plate 26d forms a portion of the edge of the exhaust port 28.

[0041] The upstream side end plate 26u is disposed at a position further upstream in the axial direction Dau than the diffuser 24. The upstream side end plate 26u extends from the outer casing 21 to the radially outer side Dro and defines the edge of the axial upstream side Dau of the exhaust space 23s. The upstream side end plate 26u is substantially perpendicular with respect to the axis Ar. Therefore, the upstream side end plate 26u is opposed to the downstream side end plate 26d with a space in the axial direction Da. The lower edge of the upstream side end plate 26u forms a part of the edge of the exhaust port 28.

[0042] The side peripheral plate 27 is connected to the edge of the radially outer side Dro of the downstream side end plate 26d and the edge of the radially outer side Dro of the upstream side end plate 26u, and extends in the axial direction Da and in the circumferential direction Dc centered on the axis Ar and defines the edge portion of the radially outer side Dro of the exhaust space 23s. The side peripheral plate 27 is a semi-cylindrical shape with the upper side formed as a semi-cylinder. The lower edge of the side peripheral plate 27 forms a part of the edge of the exhaust port 28.

[0043] The exhaust casing 23 of the first steam turbine portion 10a and the exhaust casing 23 of the second steam turbine portion 10b are connected to each other and integrated.

[0044] Steam flows into the steam flow passage FP of the first steam turbine portion 10a and the steam flow passage FP of the second steam turbine portion 10b from the steam inlet pipe 19. Here, the vertical cross-sectional shape of the steam flow passage FP of each steam turbine portion 10a, 10b with respect to the axis Ar is annular and long in the axial direction Da. The inner peripheral edge of the steam flow passage FP is defined by the rotor shaft 12, the inner blade ring 17i, and the like. Also, the outer peripheral edge of the steam flow passage FP is defined by the outer blade ring 17o, the link ring 25, and the like.

[0045] The steam flowing into the steam flow passage FP of each steam turbine portion 10a, 10b imparts a rotational force around the axis Ar to the plurality of moving blades present in the steam flow passage FP and rotates the rotor 11. The steam that rotates the rotor 11 is discharged from the exhaust port 28 into the condenser Co through the diffuser space 24s and the exhaust space 23s. The steam discharged into the condenser Co is cooled by heat exchange with the cooling medium and thereby recovered as liquid water.

[0046] However, the dryness of the steam flowing into the steam flow path FP gradually decreases as it flows in the steam flow path FP toward the axial downstream side Dad. Therefore, sometimes steam drain adheres to the surfaces of the plurality of vanes of the vane row 17s of the vane row 17s on the axial downstream side Dad among the plurality of vane rows 17s. A part of this steam drain flows as water droplets toward the axial downstream side Dad, and sometimes collides with the surfaces of the plurality of vanes of the vane row 13 of the blade row 13 present on the axial downstream side Dad of the vane row 17s to damage the vanes. Therefore, the steam turbine ST of the present embodiment is provided with a mechanism that recovers the steam drain. This mechanism is assembled in the last stage vane segment 60 on the axial downstream side Dad among the plurality of vane segments 17 and the inner side casing 30. Hereinafter, the mechanism will be described in detail.

[0047] "First Embodiment of Inner Side Casing and Vane Segment"

[0048] With regard to the inner side casing and the last stage vane segment of the present embodiment, mainly referring to Figure 2 , the description will be made.

[0049] As described using Figure 1 , the last stage vane segment 60 of the present embodiment has one vane row 17s, an inner side vane ring 17i installed on the radial inner side Dri of the one vane row 17s, and an outer side vane ring 70 (17o) installed on the radial outer side Dro of the one vane row 17s. As shown in Figure 2 , the last stage vane segment 60 also has a seal member 50.

[0050] The plurality of vanes 61 constituting the vane row 17s in the last stage vane segment 60 each extend along the radial direction Dr, and the cross-sectional shape perpendicular to the radial direction Dr is vane-shaped. The vane 61 has a cavity 62 formed in the inside thereof and a vane face drain passage 63 that connects a vane face serving as a surface thereof and the cavity 62.

[0051] The outer side vane ring 70 has a vane ring main body 71 and two vane ring protrusions 80. The vane ring main body 71 has a gas passage face 72 that extends along the circumferential direction Dc and faces the radial inner side Dri, a counter gas passage face 73 that extends along the circumferential direction Dc and has a back-to-back relationship with the gas passage face 72, a vane ring rear end face 74 that faces the axial downstream side Dad, a vane face drain recovery passage 75, a gas passage face drain recovery passage 76, and a drain groove 77. The vane ring rear end face 74 of the vane ring main body 71 is spaced apart in the axial direction Da and opposes the link ring 25 in the axial direction Da.

[0052] Two vane ring protrusions 80 protrude from the gas passage surface 73 of the vane ring main body 71 to the radially outer side Dro and extend in the circumferential direction Dc, and are opposed to each other at intervals in the axial direction Da. Here, the vane ring protrusion 80 on the upstream side of the axis Dau among the two vane ring protrusions 80 is referred to as an upstream-side vane ring protrusion (the other vane ring protrusion) 80u, and the vane ring protrusion 80 on the downstream side of the axis Dad among the two vane ring protrusions 80 is referred to as a downstream-side vane ring protrusion (one vane ring protrusion) 80d. The outer-side vane ring 70 and the inner-side casing 30 collectively form a first drain recovery space (or simply referred to as a drain recovery space) 41 between the two vane ring protrusions 80 in the axial direction Da. Also, the outer-side vane ring 70 and the inner-side casing 30 collectively form a second drain recovery space 42 at a portion further on the downstream side of the axis Dad than the downstream-side vane ring protrusion 80d. The space between the two vane ring protrusions 80 in the gas passage surface 73 of the vane ring main body 71 forms an inner-side first space demarcation surface 41i that demarcates the inner circumferential side edge of the first drain recovery space 41. Also, the portion of the gas passage surface 73 of the vane ring main body 71 further on the downstream side of the axis Dad than the downstream-side vane ring protrusion 80d forms an inner-side second space demarcation surface 42i that demarcates the inner circumferential side edge of the second drain recovery space 42.

[0053] The vane surface drain recovery passage 75 of the vane ring main body 71 extends from the cavity 62 of the stator vane 61 toward the radially outer side Dro and opens on the inner-side first space demarcation surface 41i. That is, the vane surface drain recovery passage 75 communicates the cavity 62 of the stator vane 61 with the first drain recovery space 41. The gas passage surface drain recovery passage 76 extends from a position in the gas passage surface 72 further on the upstream side of the axis Dau than the stator vane 61 toward the radially outer side Dro and opens on the inner-side first space demarcation surface 41i. That is, the gas passage surface drain recovery passage 76 communicates the steam flow path FP present on the radially inner side Dri of the vane ring main body 71 with the first drain recovery space 41. The drain groove 77 is a groove that is recessed from the gas passage surface 73 toward the radially inner side Dri and extends in the circumferential direction Dc at a position in the gas passage surface 73 further on the upstream side of the axis Dau than the upstream-side vane ring protrusion 80u.

[0054] The upstream-side vane ring protrusion 80u has a vane ring upstream-side seal face 82u facing toward the axis downstream side Dad and an upstream-side first space defining face 41u. The upstream-side first space defining face 41u is located more radially inward Dri than the vane ring upstream-side seal face 82u and on the axis downstream side Dad. Thus, the vane ring upstream-side seal face 82u has a step in the axis direction Da with respect to the upstream-side first space defining face 41u. The downstream-side vane ring protrusion 80d has a vane ring downstream-side facing face 81d facing toward the axis upstream side Dau and a downstream-side first space defining face 41d and an upstream-side second space defining face 42u facing toward the axis downstream side Dad. The downstream-side first space defining face 41d is located more radially inward Dri than the vane ring downstream-side facing face 81d and on the axis upstream side Dau. Thus, the vane ring downstream-side facing face 81d has a step in the axis direction Da with respect to the downstream-side first space defining face 41d. The downstream-side vane ring protrusion 80d also has a seal groove 83. The seal groove 83 is recessed from the vane ring downstream-side facing face 81d toward the axis downstream side Dad and extends in the circumferential direction Dc. A bottom face of the seal groove 83 forms a vane ring downstream-side seal face (or simply, a seal face) 82d extending in the circumferential direction Dc facing toward the axis upstream side Dau.

[0055] The inner side casing 30 has a casing main body 31 extending in the circumferential direction Dc centered on the axis and covering outer circumferential sides of the plurality of vane segments 17, a plurality of casing protrusions 33 protruding from the casing main body 31 toward the radially inner side Dri and extending in the circumferential direction Dc, a first drain discharge passage 45, and a second drain discharge passage 46. The plurality of casing protrusions 33 are arranged in the axis direction Da at intervals from each other. The casing protrusion 33 most on the axis downstream side Dad among the plurality of casing protrusions 33 forms a final stage protrusion 33f.

[0056] A portion of the face of the casing main body 31 facing toward the radially inner side Dri more on the axis downstream side Dad than the final stage protrusion 33f forms an outer side second space defining face 42o. A face of the casing main body 31 facing toward the axis downstream side Dad forms a casing rear end face 32. The casing rear end face 32 opposes the link ring 25 in the axis direction Da. The second drain discharge passage 46 is a groove recessed from the casing rear end face 32 toward the axis upstream side Dau and extending in the radial direction Dr. The second drain discharge passage 46 opens on a portion of the face of the casing main body 31 facing toward the radially inner side Dri, that is, the outer side second space defining face 42o, and also opens on a face of the casing main body 31 facing toward the radially outer side Dro.

[0057] The final stage protrusion 33f has a protrusion base 33b and an entry portion 33i. The protrusion base 33b protrudes from the casing main body 31 toward the radially inner side Dri. The entry portion 33i protrudes from the protrusion base 33b toward the radially inner side Dri and enters between the two vane ring protrusions 80.

[0058] The face of the entry portion 33i toward the axis upstream side Dau forms a housing upstream side seal face 35u that opposes the vane ring upstream side seal face 82u of the upstream side vane ring boss portion 80u in the axis direction Da. The housing upstream side seal face 35u is located more on the axis downstream side Dad than the face of the boss base portion 33b toward the axis upstream side Dau. Therefore, the housing upstream side seal face 35u has a step in the axis direction Da with respect to the face of the boss base portion 33b toward the axis upstream side Dau. The face of the entry portion 33i toward the axis downstream side Dad forms a housing downstream side opposing face 34d that opposes the vane ring downstream side opposing face 81d of the downstream side vane ring boss portion 80d in the axis direction Da. The portion of the housing downstream side opposing face 34d that opposes the vane ring downstream side seal face 82d, which is the bottom face of the seal groove 83, in the axis direction Da forms a housing downstream side seal face 35d. The face of the boss base portion 33b toward the axis downstream side Dad forms an upstream side second space demarcation face 42u. The housing downstream side opposing face 34d is located more on the axis upstream side Dau than the upstream side second space demarcation face 42u of the boss base portion 33b. Therefore, the housing downstream side opposing face 34d has a step in the axis direction Da with respect to the upstream side second space demarcation face 42u. The face of the entry portion 33i toward the radial inner side Dri forms an outer side first space demarcation face 41o. The first drain discharge passage 45 penetrates the final stage boss portion 33f and the housing main body 31 in the radial direction Dr. Therefore, the first drain discharge passage 45 opens on the outer side first space demarcation face 41o of the entry portion 33i and on the face of the housing main body 31 toward the radial outer side Dro.

[0059] The first drain recovery space 41 is an annular space demarcated by the inner side first space demarcation face 41i, the outer side first space demarcation face 41o, the upstream side first space demarcation face 41u, and the downstream side first space demarcation face 41d. Also, the second drain recovery space 42 is an annular space demarcated by the inner side second space demarcation face 42i, the outer side second space demarcation face 42o, and the upstream side second space demarcation face 42u. The steam turbine of the present embodiment also has a third drain recovery space 43. The third drain recovery space 43 is a space surrounded by the outer side vane ring 70 of the upstream side vane blade segment 60u, which is the vane blade segment 17 adjacent to the axis upstream side Dau of the final stage vane blade segment 60, the upstream side vane ring boss portion 80u of the outer side vane ring 70 of the final stage vane blade segment 60, the portion of the vane ring main body 71 of the outer side vane ring 70 of the final stage vane blade segment 60 that is more on the axis upstream side Dau than the upstream side vane ring boss portion 80u, and the inner side housing 30. In addition, the drain groove 77 demarcates a portion of the edge of the third drain recovery space 43.

[0060] The seal member 50 enters the seal groove 83 of the outer vane ring 70. The seal member 50 contacts the vane ring downstream side seal surface 82d and the case downstream side seal surface 35d, which are the bottom surfaces of the seal groove 83. The seal member 50 is a different member from the outer vane ring 70 and the inner case 30. That is, the seal member 50 can be separate from the outer vane ring 70 or the inner case 30.

[0061] A small amount of steam drain is sometimes contained in the steam between the outer vane ring 70 of the upstream stator vane segment 60u adjacent to the axis upstream side Dau of the last stage stator vane segment 60 and the inner vane ring 17i. Steam drain is sometimes attached to the gas passage surface 72 of the outer vane ring 70 of the upstream stator vane segment 60u. Also, steam drain is sometimes attached to the vane surfaces of the plurality of moving vanes that constitute the moving vane row 13 located more axially downstream side Dad than the stator vane row 17s of the upstream stator vane segment 60u and more axially upstream side Dau than the stator vane row 17s of the last stage stator vane segment 60. A portion of these steam drains flows into the third drain recovery space 43 along with the steam from between the outer vane ring 70 of the upstream stator vane segment 60u and the outer vane ring 70 of the last stage stator vane segment 60. The steam drain that flows into the third drain recovery space 43 is stored in the drain groove 77 formed in the outer vane ring 70 of the last stage stator vane segment 60. The steam drain stored in the drain groove 77 located more upward than the axis Ar flows downward within the drain groove 77. Then, the steam drain flows into the case inner space 21s between the inner case 30 and the outer case 21 from the third drain discharge passage 47 (refer to Figure 1 ) formed in the inner case 30 directly below the axis Ar. The steam drain that flows into the case inner space 21s is discharged to the exhaust space 23s through the drain discharge passage 22 (refer to Figure 1 ) formed in the outer case 21. The discharged steam drain within the exhaust space 23s flows into the condenser Co through the exhaust port 28 along with the steam flowing therein.

[0062] Steam drain is sometimes attached to the vane surfaces of the plurality of stator vanes 61 that constitute the stator vane row 17s of the last stage stator vane segment 60. This steam drain flows into the cavity 62 formed inside the stator vane 61 through the plurality of vane surface drain passages 63 formed in the vane surfaces of the stator vane 61. The steam drain that flows into the cavity 62 flows into the first drain recovery space 41 through the vane surface drain recovery passage 75 of the outer vane ring 70.

[0063] Sometimes, steam drain adheres to the gas passage surface 72 in the outer blade ring 70 of the last stage vane segment 60. The steam drain present in a position more upstream in the axis Dau than the stationary vane 61 is drained into the first drain recovery space 41 through the gas passage surface drain recovery passage 76 formed in the outer blade ring 70.

[0064] The steam drain drained into the first drain recovery space 41 is drained into the casing inner space 21s between the inner casing 30 and the outer casing 21 through the first drain discharge passage 45 formed in the inner casing 30. The steam drain drained into the casing inner space 21s is discharged to the exhaust space 23s through the drain discharge passage 22 formed in the outer casing 21 as well as the steam drain drained into the third drain recovery space 43. The discharged steam drain in the exhaust space 23s is drained into the condenser Co through the exhaust port 28 together with the steam flowing therein.

[0065] The steam drain adhering to the area in the gas passage surface 72 in the outer blade ring 70 of the last stage vane segment 60 more downstream in the axis Dad than the gas passage surface drain recovery passage 76 is drained into the second drain recovery space 42 through the blade ring back surface 74 of the outer blade ring 70 and the connecting ring 25. The steam drain drained into the second drain recovery space 42 is drained into the casing inner space 21s between the inner casing 30 and the outer casing 21 through the second drain discharge passage 46 formed in the inner casing 30. The steam drain drained into the casing inner space 21s is discharged to the exhaust space 23s through the drain discharge passage 22 formed in the outer casing 21 as well as the steam drain drained into the third drain recovery space 43 or the first drain recovery space 41. The discharged steam drain in the exhaust space 23s is drained into the condenser Co through the exhaust port 28 together with the steam flowing therein.

[0066] The last stage vane segment 60 receives a force toward the axis downstream side Dad from the steam flowing in the steam flow path FP in the driving of the steam turbine ST. Therefore, the last stage vane segment 60 desires to relatively move toward the axis downstream side Dad with respect to the inner casing 30. Therefore, the blade ring upstream side seal surface 82u moves toward the axis downstream side Dad with respect to the casing upstream side seal surface 35u to contact the casing upstream side seal surface 35u. Also, the blade ring upstream side seal surface 82u has a difference in the axis direction Da with respect to the upstream side first space demarcation surface 41u, and the gap of the blade ring upstream side seal surface 82u and the casing upstream side seal surface 35u does not directly face the first drain recovery space 41.

[0067] Therefore, in the present embodiment, the sealability between the last stage protrusion 33f and the upstream side vane ring protrusion 80u in the steam turbine ST drive is high, and leakage of steam from between the last stage protrusion 33f and the upstream side vane ring protrusion 80u can be suppressed. In other words, even if a pressure difference exists between the first drain recovery space 41 and the third drain recovery space 43 located on the upstream side DaU of the axis of the first drain recovery space 41, the pressure difference can be maintained.

[0068] If the steam turbine ST is driven, the vane ring downstream side facing surface 81d moves toward the downstream side Dad of the axis relative to the casing downstream side facing surface 34d, and the vane ring downstream side facing surface 81d moves away from the casing downstream side facing surface 34d. However, the seal member 50 that enters the seal groove 83 maintains contact between the vane ring downstream side seal surface 82d that is the bottom surface of the seal groove 83 and the casing downstream side seal surface 35d that is a portion of the casing downstream side facing surface 34d. Also, the vane ring downstream side facing surface 81d has a difference in height in the axis direction Da relative to the downstream side first space demarcation surface 41d, and the gap between the vane ring downstream side facing surface 81d and the casing downstream side facing surface 34d does not directly face the first drain recovery space 41.

[0069] Therefore, in the present embodiment, the sealability between the last stage protrusion 33f and the downstream side vane ring protrusion 80d in the steam turbine ST drive is high, and leakage of steam from between the last stage protrusion 33f and the downstream side vane ring protrusion 80d can be suppressed. In other words, even if a pressure difference exists between the first drain recovery space 41 and the second drain recovery space 42 located on the downstream side Dad of the axis of the first drain recovery space 41, the pressure difference can be maintained.

[0070] However, the third drain recovery space 43, the first drain recovery space 41, and the second drain recovery space 42 are arranged in the above order from the upstream side DaU of the axis toward the downstream side Dad of the axis. Therefore, the pressure of the steam flowing into the third drain recovery space 43 is higher than the pressure of the steam flowing into the first drain recovery space 41. Also, the pressure of the steam flowing into the first drain recovery space 41 is higher than the pressure of the steam flowing into the second drain recovery space 42.

[0071] In the present embodiment, as described above, because the sealability between the last stage protrusion 33f and the upstream side vane ring protrusion 80u is high, even if a pressure difference exists between the first drain recovery space 41 and the third drain recovery space 43 located on the upstream side DaU of the axis of the first drain recovery space 41, the pressure difference can be maintained. Therefore, in the present embodiment, the pressure in the third drain recovery space 43 can be maintained at a pressure that is higher than the pressure in the first drain space.

[0072] Also, in the present embodiment, as described above, since the sealability between the final-stage convex portion 33f and the downstream-side vane ring convex portion 80d is high, even if there is a pressure difference between the first drain recovery space 41 and the second drain recovery space 42 located on the downstream side Dad of the axis of the first drain recovery space 41, the pressure difference can be maintained. Therefore, in the present embodiment, the pressure in the first drain recovery space 41 can be maintained at a higher pressure than the pressure in the second drain recovery space 42.

[0073] Suppose that the sealability between the final-stage convex portion 33f and the upstream-side vane ring convex portion 80u is low and the pressure in the third drain recovery space 43 cannot be maintained at a higher pressure than the pressure in the first drain space. In this case, compared to the case where the sealability between the final-stage convex portion 33f and the upstream-side vane ring convex portion 80u is high, the pressure in the third drain recovery space 43 becomes lower and the pressure in the first drain recovery space 41 becomes higher. Therefore, in this case, a large amount of steam that does not become drain flows into the third drain recovery space 43 and is wasted and consumed, and the amount of steam drain that flows into the first drain recovery space 41 decreases. If the flow rate of steam that flows into each of the drain recovery spaces 43, 41 is increased in order to increase the amount of steam drain that flows into the first drain recovery space 41, the flow rate of steam that is wasted and consumed increases.

[0074] On the other hand, as described above, in the present embodiment, since the sealability between the final-stage convex portion 33f and the upstream-side vane ring convex portion 80u is high, the discharge of steam that does not become drain can be suppressed, and steam drain is introduced into the third drain recovery space 43 and the first drain recovery space 41.

[0075] Also, suppose that the sealability between the final-stage convex portion 33f and the downstream-side vane ring convex portion 80d is low and the pressure in the first drain recovery space 41 cannot be maintained at a higher pressure than the pressure in the second drain recovery space 42. In this case, compared to the case where the sealability between the final-stage convex portion 33f and the downstream-side vane ring convex portion 80d is high, the pressure in the first drain recovery space 41 becomes lower and the pressure in the second drain recovery space 42 becomes higher. Therefore, in this case, a large amount of steam that does not become drain flows into the first drain recovery space 41 and is wasted and consumed, and the amount of steam drain that flows into the second drain recovery space 42 decreases. If the flow rate of steam that flows into each of the drain recovery spaces 41, 42 is increased in order to increase the amount of steam drain that flows into the second drain recovery space 42, the flow rate of steam that is wasted and consumed increases.

[0076] On the other hand, as described above, in this embodiment, since the sealing between the final stage protrusion 33f and the downstream side blade ring protrusion 80d is high, the discharge of steam that has not become drainage can be suppressed, and the steam drainage can be introduced into the first drainage recovery space 41 and the second drainage recovery space 42.

[0077] Therefore, in this embodiment, the recovery efficiency of steam drainage to the third drainage recovery space 43, the first drainage recovery space 41, and the second drainage recovery space 42 can be improved.

[0078] "Second Embodiment of Inner Shell and Stationary Blade Segment"

[0079] Regarding the inner shell and stationary blade segment of this embodiment, please refer to... Figure 3 Please provide an explanation.

[0080] If used Figure 1 As described above, the final stage stationary blade segment 60a of this embodiment also has a stationary blade row 17s, an inner blade ring 17i mounted on the radially inner side Dri of the stationary blade row 17s, and an outer blade ring 70a (17o) mounted on the radially outer side Dro of the stationary blade row 17s. Figure 3 As shown, the final stage stationary blade segment 60a also further has a sealing component 50.

[0081] The multiple stationary blades 61 constituting the stationary blade row 17s in the final stage stationary blade segment 60a, like the stationary blades 61 in the first embodiment, all have cavities 62 and blade surface drainage channels 63.

[0082] The outer blade ring 70a has a blade ring body 71 and two blade ring protrusions 80a. The blade ring body 71, similar to that in the first embodiment, has a gas passage surface 72 that extends circumferentially Dc and faces radially inward Dri, a reverse gas passage surface 73 that extends circumferentially Dc and has a back-to-back relationship with the gas passage surface 72, a blade ring rear end face 74 facing downstream of the axis Dad, a blade surface drainage recovery channel 75, a gas passage surface drainage recovery channel 76, and a drainage groove 77.

[0083] The two vane ring protrusions 80a project from the gas passage surface 73 of the vane ring main body 71 to the radial outer side Dro and extend in the circumferential direction Dc, and are spaced apart from each other in the axial direction Da, similarly to the first embodiment. The outer vane ring 70a forms the first drainage recovery space 41 in cooperation with the inner casing 30 between the two vane ring protrusions 80a in the axial direction Da. Also, the outer vane ring 70a forms the second drainage recovery space 42 in cooperation with the inner casing 30 at a portion on the axial downstream side Dad further than the downstream-side vane ring protrusion 80da. The inner-side first space demarcation surface 41i demarcating the inner circumferential side edge of the first drainage recovery space 41 is formed in the gas passage surface 73 of the vane ring main body 71 between the two vane ring protrusions 80a. Also, the inner-side second space demarcation surface 42i demarcating the inner circumferential side edge of the second drainage recovery space 42 is formed in the gas passage surface 73 of the vane ring main body 71 at a portion on the axial downstream side Dad further than the downstream-side vane ring protrusion 80da.

[0084] The upstream-side vane ring protrusion 80ua of the two vane ring protrusions 80a has a vane ring upstream-side opposing surface 81ua facing the axial upstream side Dau and an upstream-side first space demarcation surface 41u facing the axial downstream side Dad. The upstream-side vane ring protrusion 80ua also has a seal groove 83a. The seal groove 83a is recessed from the vane ring upstream-side opposing surface 81ua toward the axial downstream side Dad and extends in the circumferential direction Dc. The bottom surface of the seal groove 83a forms a vane ring upstream-side seal surface 82ua extending in the circumferential direction Dc toward the axial upstream side Dau. The downstream-side vane ring protrusion 80da of the two vane ring protrusions 80a has a vane ring downstream-side seal surface 82da facing the axial downstream side Dad and a downstream-side first space demarcation surface 41d facing the axial upstream side Dau.

[0085] The inner casing 30a has a casing main body 31 extending in the circumferential direction Dc with the axis as the center and covering the outer circumferential side of the plurality of stator vane segments 17, a plurality of casing protrusions 33 projecting from the casing main body 31 to the radial inner side Dri and extending in the circumferential direction Dc, a first drainage discharge passage 45a, and a second drainage discharge passage 46, similarly to the first embodiment. The plurality of casing protrusions 33 are arranged in the axial direction Da at intervals from each other. However, in the present embodiment, the casing protrusion 33 on the axial downstream side Dad furthest and the casing protrusion 33 adjacent to the casing protrusion 33 form a final-stage protrusion 33fa. The casing protrusion 33 on the axial upstream side Dau of the two casing protrusions 33 constituting the final-stage protrusion 33fa forms a final-stage upstream-side protrusion 33ua, and the casing protrusion 33 on the axial downstream side Dad forms a final-stage downstream-side protrusion 33da.

[0086] The outer side first space demarcation surface 41o is formed in the face of the housing main body 31 facing the radial inner side Dri between the last stage upstream side protrusion 33ua and the last stage downstream side protrusion 33da. Also, the outer side second space demarcation surface 42o is formed in the portion of the face of the housing main body 31 facing the axial downstream side Dad more than the last stage downstream side protrusion 33da. The face of the housing main body 31 facing the axial downstream side Dad forms a housing rear end surface 32. This housing rear end surface 32, like the first embodiment, opposes the link ring 25 in the axial direction Da. The second drain discharge passage 46, like the first embodiment, is a groove recessed from the housing rear end surface 32 toward the axial upstream side Dau and extending in the radial direction Dr.

[0087] The last stage upstream side protrusion 33ua has a housing upstream side opposing surface 34ua facing the axial downstream side Dad and an upstream side first space demarcation surface 41u. The housing upstream side opposing surface 34ua opposes the vane ring upstream side opposing surface 81ua in the axial direction Da. The portion of the housing upstream side opposing surface 34ua opposing the vane ring upstream side sealing surface 82ua forms a housing upstream side sealing surface 35ua. The upstream side first space demarcation surface 41u is located more radially outward Dro and axially downstream Dad than the housing upstream side opposing surface 34ua. The last stage downstream side protrusion 33da has a housing downstream side sealing surface 35da facing the axial upstream side Dau and a downstream side first space demarcation surface 41d and an upstream side second space demarcation surface 42u facing the axial downstream side Dad. The housing downstream side sealing surface 35da and the vane ring downstream side sealing surface 82da oppose each other in the axial direction Da in a contactable manner. The downstream side first space opposing surface is located more radially outward Dro and axially upstream Dau than the housing downstream side sealing surface 35da.

[0088] The first drain discharge passage 45a penetrates the housing main body 31 in the radial direction Dr between the last stage upstream side protrusion 33ua and the last stage downstream side protrusion 33da. Therefore, the first drain discharge passage 45a opens on the outer side first space demarcation surface 41o and on the face of the housing main body 31 facing the radial outward side Dro.

[0089] The first drain recovery space 41 is an annular space delimited by the inner first space delimiting surface 41i, the outer first space delimiting surface 41o, the upstream first space delimiting surface 41u, and the downstream first space delimiting surface 41d. Also, the second drain recovery space 42 is an annular space delimited by the inner second space delimiting surface 42i, the outer second space delimiting surface 42o, and the upstream second space delimiting surface 42u. The steam turbine ST of the present embodiment also has a third drain recovery space 43. This third drain recovery space 43 is, like the first embodiment, a space surrounded by the outer blade ring 70 of the upstream vane segment 60u that is adjacent to the axis upstream side Dau of the last stage vane segment 60a, the upstream blade ring protrusion 80ua of the outer blade ring 70a of the last stage vane segment 60a, the portion of the blade ring main body 71 of the outer blade ring 70a of the last stage vane segment 60a that is further upstream of the axis Dau than the upstream blade ring protrusion 80ua, and the inner casing 30a.

[0090] The seal member 50 enters the seal groove 83a of the outer blade ring 70a. This seal member 50 contacts the blade ring upstream seal surface 82ua that is the bottom surface of the seal groove 83a and the casing upstream seal surface 35ua. The seal member 50, like the first embodiment, is a member that is different from the outer blade ring 70a and the inner casing 30a.

[0091] In the present embodiment, like the first embodiment, the steam and the steam drain within the steam flow path FP flow from between the outer blade ring 70 of the upstream vane segment 60u and the outer blade ring 70a of the last stage vane segment 60a into the third drain recovery space 43. The steam drain that flows into this third drain recovery space 43 is stored in the drain groove 77 formed in the outer blade ring 70a of the last stage vane segment 60a. The steam drain that is stored in the drain groove 77 at a position that is further upward of the axis Ar flows downward within the drain groove 77. Then, this steam drain flows from the third drain discharge passage 47 (refer to FIG. 6) that is formed in the inner casing 30a at a position directly below the axis Ar into the casing inner space 21s between the inner casing 30a and the outer casing 21. The steam drain that flows into the casing inner space 21s is discharged to the exhaust space 23s through the drain discharge passage 22 formed in the outer casing 21. The discharged steam drain within the exhaust space 23s flows into the condenser Co through the exhaust port 28 together with the steam flowing therein. Figure 1

[0092] ​The steam drainage adhering to the blade surfaces of the plurality of stationary vanes 61 constituting the stationary vane row 17s of the last stage stationary vane segment 60a also flows into the cavity 62 formed in the interior of the stationary vane 61 through the plurality of blade surface drainage passages 63 formed in the stationary vane 61 in the present embodiment as in the first embodiment. The steam drainage flowing into the cavity 62 flows into the first drainage recovery space 41 through the blade surface drainage recovery passage 75 of the outer vane ring 70a.

[0093] Steam drainage adhering to the gas passage surface 72 in the outer vane ring 70a of the last stage stationary vane segment 60a sometimes exists. The steam drainage existing at a position further upstream in the axial direction Dau than the stationary vane 61 flows into the first drainage recovery space 41 through the gas passage surface drainage recovery passage 76 formed in the outer vane ring 70a as in the first embodiment.

[0094] The steam drainage flowing into the first drainage recovery space 41 flows into the space 21s between the inner casing 30a and the outer casing 21 through the first drainage discharge passage 45a formed in the inner casing 30a as in the first embodiment. The steam drainage flowing into the space 21s is discharged to the exhaust space 23s through the drainage discharge passage 22 (refer to Figure 1 ) formed in the outer casing 21. The discharged steam drainage in the exhaust space 23s flows into the condenser Co through the exhaust port 28 together with steam flowing therein as in the first embodiment.

[0095] The steam drainage adhering to the region of the gas passage surface 72 in the outer vane ring 70a of the last stage stationary vane segment 60a further downstream in the axial direction Dad than the gas passage surface drainage recovery passage 76 flows into the second drainage recovery space 42 between the vane ring rear surface 74 of the outer vane ring 70a and the link ring 25 as in the first embodiment. The steam drainage flowing into the second drainage recovery space 42 flows into the space 21s between the inner casing 30a and the outer casing 21 through the second drainage discharge passage 46 formed in the inner casing 30a. The steam drainage flowing into the space 21s is discharged to the exhaust space 23s through the drainage discharge passage 22 formed in the outer casing 21 as in the steam drainage flowing into the third drainage recovery space 43 or the first drainage recovery space 41. The discharged steam drainage in the exhaust space 23s flows into the condenser Co through the exhaust port 28 together with steam flowing therein.

[0096] In the present embodiment, the last-stage vane segment 60a also receives a force from the steam flowing in the steam flow passage FP toward the axial downstream side Dad in the driving of the steam turbine ST as in the first embodiment. Therefore, the last-stage vane segment 60a tends to relatively move toward the axial downstream side Dad with respect to the inner side casing 30a. Therefore, the vane ring downstream side seal surface 82da moves toward the axial downstream side Dad in contact with the casing downstream side seal surface 35da with respect to the casing downstream side seal surface 35da. Therefore, the sealability between the last-stage downstream side protrusion 33da and the downstream side vane ring protrusion 80da in the driving of the steam turbine ST is high, and the steam leakage from between the last-stage downstream side protrusion 33da and the downstream side vane ring protrusion 80da can be suppressed. In other words, even if a pressure difference exists between the first drain recovery space 41 and the second drain recovery space 42 located on the axial downstream side Dad of the first drain recovery space 41, the pressure difference can be maintained.

[0097] Also, if the steam turbine ST is driven, the vane ring upstream side facing surface 81 ua moves toward the axial downstream side Dad with respect to the casing upstream side facing surface 34 ua, and the vane ring upstream side facing surface 81 ua moves away from the casing upstream side facing surface 34 ua. However, the seal member 50 entering into the seal groove 83a maintains contact of the vane ring upstream side seal surface 82 ua, which is the bottom surface of the seal groove 83a, with the casing upstream side seal surface 35 ua, which is a part of the casing upstream side facing surface 34 ua. Therefore, the sealability between the last-stage upstream side protrusion 33 ua and the upstream side vane ring protrusion 80 ua in the driving of the steam turbine ST is high, and the steam leakage from between the last-stage upstream side protrusion 33 ua and the upstream side vane ring protrusion 80 ua can be suppressed. In other words, even if a pressure difference exists between the first drain recovery space 41 and the third drain recovery space 43 located on the axial upstream side Dau of the first drain recovery space 41, the pressure difference can be maintained.

[0098] However, the third drain recovery space 43, the first drain recovery space 41, and the second drain recovery space 42 are arranged in the above order from the axial upstream side Dau toward the axial downstream side Dad as in the first embodiment. Therefore, the pressure of the steam flowing into the third drain recovery space 43 is higher than the pressure of the steam flowing into the first drain recovery space 41. Also, the pressure of the steam flowing into the first drain recovery space 41 is higher than the pressure of the steam flowing into the second drain recovery space 42.

[0099] In this embodiment, as described above, due to the high sealing between the upstream protrusion 33ua of the final stage and the upstream blade ring protrusion 80ua, the pressure difference can be maintained even if there is a pressure difference between the first drainage recovery space 41 and the third drainage recovery space 43 located on the upstream side Dau of the first drainage recovery space 41. Therefore, in this embodiment, the pressure in the third drainage recovery space 43 can be maintained at a higher pressure than the pressure in the first drainage recovery space 41.

[0100] Furthermore, in this embodiment, as described above, due to the high sealing between the downstream side protrusion 33da and the downstream side blade ring protrusion 80da, even if there is a pressure difference between the first drainage recovery space 41 and the second drainage recovery space 42 located downstream of the axis of the first drainage recovery space 41, this pressure difference can be maintained. Therefore, in this embodiment, the pressure in the first drainage recovery space 41 can be maintained at a higher pressure than the pressure in the second drainage recovery space 42.

[0101] Therefore, in this embodiment, similar to the first embodiment, the recovery efficiency of steam drainage to the third drainage recovery space 43, the first drainage recovery space 41, and the second drainage recovery space 42 can be improved.

[0102] "A first variation of the first embodiment"

[0103] In the first embodiment, a sealing member 50 is disposed within a sealing groove 83 in which the opposing surface 81d of the blade ring downstream of the blade ring, which is recessed towards the downstream side Dad of the axis, extends from the downstream blade ring protrusion 80d toward the upstream side Dau of the axis. However, as Figure 4 As shown, a sealing member 50 may also be disposed within a sealing groove 83b that is recessed radially inward toward Dri from the downstream blade ring opposing surface 81db of the downstream blade ring protrusion 80d toward the radially outward Dro. In this case, the bottom surface of the sealing groove 83b forms a downstream blade ring sealing surface 82db that extends circumferentially toward the radially outward Dro. Furthermore, a downstream housing opposing surface 34db is formed on the surface of the convex base 33b of the final stage protrusion 33f at a position further downstream of the axis than the entry portion 33i on the Dad side, toward the radially inward Dri. In addition, a downstream housing opposing surface 35db is formed on the portion of the downstream housing opposing surface 34db that is radially opposite the downstream blade ring sealing surface 82db in the radial Dr direction.

[0104] As explained above, the present modification is a modification of the first embodiment. However, in the second embodiment as well, it is possible to make a modification in the same manner as the present modification. That is, in the second embodiment, it is possible to arrange the seal member 50 in the seal groove recessed toward the radial inner side Dri on the vane ring upstream side facing the radial outer side Dro from the vane ring upstream side protrusion 80u. In this case, the groove bottom surface of the seal groove forms a vane ring upstream side seal surface extending along the circumferential direction Dc toward the radial outer side Dro. Also, the face of the last stage upstream side protrusion 33ua toward the radial inner side Dri forms a case upstream side facing surface. Further, the portion of this case upstream side facing surface facing the vane ring upstream side seal surface in the radial direction Dr forms a case upstream side seal surface.

[0105] "Second Modification of the First Embodiment"

[0106] In the first embodiment, the seal groove 83 is formed in the downstream side vane ring protrusion 80d. However, as shown in Figure 5 the drawing, it is also possible to form the seal groove 83c in the last stage protrusion 33f. In this case, the seal groove 83c is recessed from the case downstream side facing surface 34d of the last stage protrusion 33f toward the axis upstream side Dau. The groove bottom surface of this seal groove 83c forms a case downstream side seal surface 35d. Also, the portion of the vane ring downstream side facing surface 81d of the downstream side vane ring protrusion 80d facing the case downstream side seal surface 35d forms a vane ring downstream side seal surface 82d.

[0107] As explained above, the present second modification is a modification of the first embodiment. However, in the second embodiment or the first modification of the first embodiment as well, it is possible to make a modification in the same manner as the present second modification. That is, it is possible to form a seal groove in the last stage protrusion.

[0108] "Other Modifications"

[0109] The steam turbines of the above embodiments and each modification are all two split flow exhaust type steam turbines. However, the steam turbine need not be a two split flow exhaust type, and can be a single flow exhaust type.

[0110] "Supplementary Note"

[0111] The vane blade segment 60, 60a in the above embodiments can be grasped, for example, as follows.

[0112] (1) In the first aspect, the stator vane segment 60, 60a in the first aspect includes: an outer vane ring 70, 70a extending in a circumferential direction Dc with respect to the axis Ar; a plurality of stator vanes 61 extending from the outer vane ring 70, 70a toward a radially inner side Dri with respect to the axis Ar and arranged in the circumferential direction Dc; and a seal member 50 formed of a different member from the outer vane ring 70, 70a. The plurality of stator vanes 61 each has: a cavity 62 formed in an interior thereof; and a vane face drain passage 63 that communicates a surface thereof with the cavity 62. The outer vane ring 70, 70a has a vane ring main body 71 and two vane ring protrusions 80, 80a. The vane ring main body 71 has: a gas passage face 72 that extends in the circumferential direction Dc and faces the radially inner side Dri; an inverse gas passage face 73 that extends in the circumferential direction Dc and has a back-to-back relationship with the gas passage face 72; and a vane face drain recovery passage 75. The two vane ring protrusions 80, 80a protrude from the inverse gas passage face 73 toward a radially outer side Dro with respect to the axis Ar and extend in the circumferential direction Dc, and are spaced apart from each other in an axis direction Da in which the axis Ar extends, and a drain recovery space 41 is formed between the two vane ring protrusions 80, 80a in cooperation with a housing 30, 30a present on an outer peripheral side of the vane ring main body 71. The vane face drain recovery passage 75 extends from the cavity 62 toward the radially outer side Dro and opens at a position between the two vane ring protrusions 80, 80a in the inverse gas passage face 73. One of the two vane ring protrusions 80, 80a has a seal face 82d, 82ua, 82db. The seal member 50 is disposed between a portion of the housing 30 and the seal face 82d, 82ua, 82db of the one vane ring protrusion 80, 80a and is in contact with the seal face 82d, 82ua, 82db.

[0113] In the present aspect, vapor drain attached to a vane face of the stator vane 61 flows into the drain recovery space 41 through the vane face drain passage 63 and the cavity 62. In the present aspect, the seal member 50 is disposed between a portion of the housing 30, 30a and the seal face 82d, 82ua, 82db of the one vane ring protrusion 80, 80a, and thus the sealability between the housing 30, 30a and the one vane ring protrusion 80, 80a is improved. Therefore, even if there is a pressure difference between the drain recovery space 41 commonly formed by the housing 30, 30a and the outer vane ring 70, 70a and a space adjacent to the drain recovery space 41, the pressure difference can be maintained, and the outflow of vapor from one of the two adjacent spaces to the other space can be suppressed. Therefore, in the present aspect, the discharge of vapor that is not drain can be suppressed, and the vapor drain can be introduced into the drain recovery space 41.

[0114] (2) In the second mode, the vane segment 60, 60a has the vane ring body 71 with a gas passage face drain recovery passage 76 extending from the gas passage face 72 toward the radially outer side Dro and opening at a position between the two vane ring protrusions 80, 80a in the reverse gas passage face 73.

[0115] In this mode, it is possible to recover the steam drain attached to the gas passage face 72 of the vane ring body 71.

[0116] (3) In the third mode, the vane segment 60, 60a has the vane ring body 71 with a drain groove 77 recessed from the reverse gas passage face 73 toward the radially inner side Dri and extending along the circumferential direction Dc at a position further upstream of the axis upstream side Dau than the upstream side vane ring protrusion 80u, 80ua of one of the two sides in the axis direction Da, i.e., the axis upstream side Dau.

[0117] In this mode, it is possible to recover the steam drain from further upstream of the axis upstream side Dau than the vane segment 60, 60a by the drain groove 77.

[0118] (4) The steam turbine ST in the fourth mode has the stationary vane segment 60, 60a of any one of the first through third modes, and the casing 30, 30a covering the outer peripheral side of the stationary vane segment 60, 60a. The casing 30, 30a has a casing main body 31 separated from the stationary vane segment 60, 60a toward the radial outer side Dro and extending along the circumferential direction Dc and covering the outer peripheral side of the stationary vane segment 60, 60a, at least one casing protrusion 33f, 33fa, and a drain discharge passage 45, 45a. The drain discharge passage 45, 45a extends from the drain recovery space 41 toward the radial outer side Dro and opens on the outer peripheral surface of the casing main body 31. The at least one casing protrusion 33f, 33fa protrudes from the casing main body 31 toward the radial inner side Dri and extends along the circumferential direction Dc so as to form the drain recovery space 41 in common with the outer side vane ring 70 between the anti-gas passage surface 73 on the radial outer side Dro and the two vane ring protrusions 80, 80a. A portion of the at least one casing protrusion 33f, 33fa overlaps the one vane ring protrusion 80, 80a and the other vane ring protrusion 80, 80a in the position in the radial direction Dr with respect to the axis Ar and is located on the axis downstream side Dad of the two sides in the axis direction Da, i.e., the axis upstream side Dau and the other axis downstream side Dad. The portion of the at least one casing protrusion 33f, 33fa has a casing other side sealing surface 35u, 35da toward the axis upstream side Dau. The other vane ring protrusion 80, 80a has a vane ring other side sealing surface 82u, 82da toward the axis downstream side Dad and contactable with the casing other side sealing surface 35u, 35da. Another portion of the at least one casing protrusion 33f, 33fa has a casing one side sealing surface 35d, 35ua contactable with the sealing member 50. The one vane ring protrusion 80, 80a has a vane ring one side sealing surface 82d, 82ua, 82db opposed to the casing one side sealing surface 35d, 35ua at a spacing and as the sealing surface 82d, 82ua, 82db. The sealing member 50 is disposed between the casing one side sealing surface 35d, 35ua and the vane ring one side sealing surface 82d, 82ua, 82db.

[0119] The stationary vane segment 60, 60a receives a force toward the axis downstream side Dad from steam flowing in the steam flow passage FP in driving of the steam turbine ST. Therefore, the stationary vane segment 60, 60a tends to relatively move toward the axis downstream side Dad with respect to the casing 30, 30a.

[0120] Therefore, the other-side seal surface 82u, 82da of the vane ring is moved to the downstream side Dad of the axis relative to the other-side seal surface 35u, 35da of the casing and comes into contact with the other-side seal surface 35u, 35da of the casing. Therefore, in the present embodiment, the sealability between the portion of the at least one casing protrusion 33f, 33fa and the other vane ring protrusion 80, 80a is high, and leakage of steam from between the portion of the at least one casing protrusion 33f, 33fa and the other vane ring protrusion 80, 80a can be suppressed.

[0121] The seal member 50 is arranged between the casing-side seal surface 35d, 35ua of the other portion of the at least one casing protrusion 33f, 33fa and the vane ring-side seal surface 82d, 82ua, 82db of the one vane ring protrusion 80, 80a. Therefore, in the present embodiment, even if the one vane ring protrusion 80, 80a is moved to the downstream side Dad of the axis relative to the other portion of the at least one casing protrusion 33f, 33fa due to driving of the steam turbine ST, the sealability between the other portion of the at least one casing protrusion 33f, 33fa and the one vane ring protrusion 80, 80a is high, and leakage of steam from between the other portion of the at least one casing protrusion 33f, 33fa and the one vane ring protrusion 80, 80a can be suppressed.

[0122] Therefore, in the present embodiment, even if a pressure difference exists between the drain recovery space 41 formed by the casing 30, 30a and the outer vane ring 70, 70a in common and the space adjacent to the drain recovery space 41, the pressure difference can be maintained, and outflow of steam from one of the two adjacent spaces to the other can be suppressed.

[0123] (5) In the fifth mode, the steam turbine ST is in the fourth mode of the steam turbine ST, the upstream-side vane ring protrusion 80u of the two vane ring protrusions 80 located on the upstream side Dau of the axis line forms the other vane ring protrusion 80. The upstream-side vane ring protrusion 80u has a vane ring upstream-side seal face 82u as the vane ring other-side seal face 82u, which extends along the circumferential direction Dc toward the axis line downstream side Dad. The downstream-side vane ring protrusion 80d of the two vane ring protrusions 80 located at a position further on the axis line downstream side Dad than the upstream-side vane ring protrusion 80u forms the one vane ring protrusion 80. The downstream-side vane ring protrusion 80d has a vane ring downstream-side seal face 82d as the vane ring one-side seal face 82d, which extends along the circumferential direction Dc toward the axis line upstream side Dau or which extends along the circumferential direction Dc toward the radial direction outer side Dro. At least a portion of the at least one casing protrusion 33f enters between the two vane ring protrusions 80. The at least one casing protrusion 33f has an outer side space defining face 41o, a casing downstream-side seal face 35d as the casing one-side seal face 35d, and a casing upstream-side seal face 35u as the casing other-side seal face 35u. The outer side space defining face 41o and the inner side space defining face 41i between the two vane ring protrusions 80 in the reverse gas passage face 73 are spaced apart and opposed in the radial direction Dr with respect to the axis line Ar. The casing upstream-side seal face 35u is opposed to the vane ring upstream-side seal face 82u in a manner capable of contacting the vane ring upstream-side seal face 82u. The casing downstream-side seal face 35d is spaced apart and opposed to the vane ring downstream-side seal face 82d. The seal member 50 is disposed between the casing downstream-side seal face 35d and the vane ring downstream-side seal face 82d.

[0124] In the present mode, if the upstream-side vane ring protrusion 80u moves toward the axis line downstream side Dad with respect to the at least one casing protrusion 33f due to driving of the steam turbine ST, the vane ring upstream-side seal face 82u moves toward the axis line downstream side Dad with respect to the casing upstream-side seal face 35u and comes into contact with the casing upstream-side seal face 35u. Therefore, in the present mode, the sealability between the at least one casing protrusion 33f and the upstream-side vane ring protrusion 80u in driving of the steam turbine ST is high, and leakage of steam from between the at least one casing protrusion 33f and the upstream-side vane ring protrusion 80u can be suppressed.

[0125] The seal member 50 is disposed between the casing downstream-side seal face 35d of the at least one casing protrusion 33f and the vane ring downstream-side seal face 82d of the downstream-side vane ring protrusion 80d.

[0126] Therefore, in the present embodiment, even if the downstream-side blade ring protrusion 80d is moved toward the axis downstream side Dad with respect to the at least one housing protrusion 33f due to driving of the steam turbine ST, the sealing property between the at least one housing protrusion 33f and the downstream-side blade ring protrusion 80d is high, and leakage of steam from between the at least one housing protrusion 33f and the downstream-side blade ring protrusion 80d can be suppressed.

[0127] (6) In the steam turbine ST of the sixth aspect, in the steam turbine ST of the fifth aspect, the at least one portion of the at least one housing protrusion 33f forms an entry portion 33i that enters between the two blade ring protrusions 80. The entry portion 33i has a face toward the radial inner side Dri, the housing upstream-side sealing face 35u toward the axis upstream side Dau, and a housing downstream-side facing face 34d toward the axis downstream side Dad. The face of the entry portion 33i toward the radial inner side Dri forms the outer side space delimiting face 41o. The housing downstream-side facing face 34d of the entry portion 33i faces the blade ring downstream-side facing face 81d, which is a portion of the face of the downstream-side blade ring protrusion 80d toward the axis upstream side Dau, in the axis direction Da. The distance in the axis direction Da between the housing upstream-side sealing face 35u and the blade ring upstream-side sealing face 82u is smaller than the distance in the axis direction Da between the housing downstream-side facing face 34d and the blade ring downstream-side facing face 81d, or is 0.

[0128] (7) In the steam turbine ST of the seventh aspect, in the steam turbine ST of the sixth aspect, the upstream-side blade ring protrusion 80u has an upstream-side space delimiting face 41u that is located at a position closer to the radial inner side Dri than the blade ring upstream-side sealing face 82u, and delimits an edge of the axis upstream side Dau of the drain recovery space 41 toward the axis downstream side Dad. The downstream-side blade ring protrusion 80d has a downstream-side space delimiting face 41d that is located at a position closer to the radial inner side Dri than the blade ring downstream-side facing face 81d, and delimits an edge of the axis downstream side Dad of the drain recovery space 41 toward the axis upstream side Dau. The upstream-side space delimiting face 41u is located at a position closer to the axis downstream side Dad than the blade ring upstream-side sealing face 82u. The downstream-side space delimiting face 41d is located at a position closer to the axis upstream side Dau than the blade ring downstream-side facing face 81d.

[0129] In the present embodiment, the vane ring upstream side seal surface 82u is present at a difference in height in the axial direction Da with respect to the upstream side space defining surface 41u, and the gap between the vane ring upstream side seal surface 82u and the housing upstream side seal surface 35u does not directly face the drain recovery space 41. Therefore, in the present embodiment, the sealability between the at least one housing protrusion 33f and the upstream side vane ring protrusion 80u can be improved. Also, in the present embodiment, the vane ring downstream side facing surface 81d is present at a difference in height in the axial direction Da with respect to the downstream side space defining surface 41d, and the gap between the vane ring downstream side facing surface 81d and the housing downstream side facing surface 34d does not directly face the drain recovery space 41. Therefore, in the present embodiment, the sealability between the at least one housing protrusion 33f and the downstream side vane ring protrusion 80d can be improved.

[0130] (8) The steam turbine ST in the eighth aspect is the steam turbine ST in the sixth aspect or the seventh aspect, wherein the downstream side vane ring protrusion 80d has a seal groove 83 recessed from the vane ring downstream side facing surface 81d toward the axial downstream side Dad and extending along the circumferential direction Dc for entry of the seal member 50. A bottom surface of the seal groove 83 forms the vane ring downstream side seal surface 82d extending along the circumferential direction Dc toward the axial upstream side Dau.

[0131] (9) In the ninth aspect, the steam turbine ST in the fourth aspect, of the two blade ring bosses 80a, an upstream side blade ring boss 80ua on the upstream side Dau of the axis forms the one blade ring boss 80a. The upstream side blade ring boss 80ua has a blade ring upstream side seal face 82ua as the blade ring one side seal face 82ua, which extends along the circumferential direction Dc toward the radial direction outer side Dro or toward the axis upstream side Dau. Of the two blade ring bosses 80a, a downstream side blade ring boss 80da on the downstream side Dad of the axis forms the other blade ring boss 80a. The downstream side blade ring boss 80da has a blade ring downstream side seal face 82da as the blade ring other side seal face 82da, which extends along the circumferential direction Dc toward the axis downstream side Dad. The at least one housing boss 33fa has two housing bosses 33ua, 33da which are spaced apart from each other in the axis direction Da. The portion of the housing main body 31 between the two housing bosses 33ua, 33da in the face toward the radial direction inner side Dri forms an outer side space demarcation face 41o which is spaced apart from the inner side space demarcation face 41i between the two blade ring bosses 80a in the gas passage face 73 in the radial direction Dr with respect to the axis Ar. Of the two housing bosses 33ua, 33da, the upstream side housing boss 33ua on the axis upstream side Dau has a housing upstream side seal face 35ua as the housing one side seal face 35ua, which is spaced apart from the blade ring upstream side seal face 82ua. Of the two housing bosses 33ua, 33da, the downstream side housing boss 33da on the axis downstream side Dad has a housing downstream side seal face 35da as the housing other side seal face 35da, which is opposed to the blade ring downstream side seal face 82da toward the axis upstream side Dau in a manner so as to be able to contact the blade ring downstream side seal face 82da. The seal member 50 is disposed between the housing upstream side seal face 35ua and the blade ring upstream side seal face 82ua.

[0132] The stationary blade segment 60a receives a force toward the axial downstream side Dad from steam flowing in the steam flow passage FP in driving of the steam turbine ST. Therefore, the stationary blade segment 60a desires to relatively move toward the axial downstream side Dad with respect to the casing 30a. Therefore, the blade ring downstream side seal surface 82da of the downstream side blade ring protrusion 80da moves toward the axial downstream side Dad in contact with the casing downstream side seal surface 35da of the downstream side casing protrusion 33da. Therefore, in the present embodiment, the sealability between the downstream side casing protrusion 33da and the downstream side blade ring protrusion 80da in driving of the steam turbine ST is high, and leakage of steam from between the downstream side casing protrusion 33da and the downstream side blade ring protrusion 80da can be suppressed.

[0133] The seal member 50 is arranged between the casing upstream side seal surface 35ua of the upstream side casing protrusion 33ua and the blade ring upstream side seal surface 82ua of the upstream side blade ring protrusion 80ua.

[0134] Therefore, in the present embodiment, even if the upstream side blade ring protrusion 80ua moves toward the axial downstream side Dad with respect to the upstream side casing protrusion 33ua due to driving of the steam turbine ST, the sealability between the upstream side casing protrusion 33ua and the upstream side blade ring protrusion 80ua is high, and leakage of steam from between the upstream side casing protrusion 33ua and the upstream side blade ring protrusion 80ua can be suppressed.

[0135] (10) In the steam turbine ST of any one of the fourth to ninth embodiments, the outer side blade ring 70, 70a and the casing 30, 30a are configured to form, in addition to the drainage recovery space 41, i.e., the first drainage recovery space 41, between the two blade ring protrusions 80, 80a in common with each other, a second drainage recovery space 42 adjacent to the axial downstream side Dad of the first drainage recovery space 41 via the downstream side blade ring protrusion 80d, 80da of the two blade ring protrusions 80, 80a located on the axial downstream side Dad between the casing main body 31 and the counter gas passage surface 73. The casing main body 31 has a second drainage discharge passage 46 extending from the second drainage recovery space 42 toward the radial outside Dro and opening on an outer peripheral surface of the casing main body 31.

[0136] In the present embodiment, a part of the steam drain attached to the gas passage surface 72 of the outer vane ring 70 flows into the second drain recovery space 42 from between the rear end surface 74 of the outer vane ring 70, 70a and the member present on the downstream side Dad of the axis of the outer vane ring 70. In the present embodiment, since the sealability between the downstream vane ring protrusion 80d, 80da and the at least one housing protrusion 33f, 33fa is high, even if a pressure difference exists between the first drain recovery space 41 and the second drain recovery space 42, the pressure difference can be maintained, and the outflow of steam from one of the adjacent two spaces 41, 42 to the other can be suppressed. Therefore, in the present embodiment, the discharge of steam that does not become drain can be suppressed, and the steam drain is introduced into the first drain recovery space 41 and the second drain recovery space 42.

[0137] (11) In the steam turbine ST of the eleventh aspect, in any one of the fourth to tenth aspects, the vane segment 60, 60a is formed of a material having high corrosion resistance to steam as compared with the housing 30, 30a.

[0138] In the present embodiment, corrosion of the vane segment 60, 60a caused by steam can be suppressed.

[0139] Industrial Applicability

[0140] In one embodiment of the present application, the recovery efficiency of steam drain can be improved.

[0141] Explanation of Symbols

[0142] 10a - first steam turbine section, 10b - second steam turbine section, 11 - rotor, 12 - rotor shaft, 13 - row of moving blades, 13f - row of final stage moving blades, 17 - stationary blade segment, 17s - row of stationary blades, 17i - inner blade ring, 17o - outer blade ring, 18 - bearing, 19 - steam inlet pipe, 20 - casing, 21 - outer casing, 21s - inner space of casing, 22 - drain discharge passage, 23 - exhaust casing, 23s - exhaust space, 24 - diffuser, 24s - diffuser space, 24o - outer diffuser, 24i - inner diffuser, 25 - connecting ring, 26d - lower side end plate, 26u - upper side end plate, 27 - side peripheral plate, 28 - exhaust port, 30, 30a - inner casing (or simply casing), 31 - casing main body, 32 - casing rear end surface, 33 - casing convex portion, 33f, 33fa - final stage convex portion, 33b - convex base portion, 33i - entry portion, 33ua - final stage upper side convex portion (or upper side casing convex portion), 33da - final stage lower side convex portion (or lower side casing convex portion), 34ua - casing upper side facing surface, 34d, 34db - casing lower side facing surface, 35u - casing upper side sealing surface (or another side sealing surface of casing), 35ua - casing upper side sealing surface (or one side sealing surface of casing, or sealing surface), 35d - casing lower side sealing surface (or one side sealing surface of casing, or sealing surface), 35da, 35db - casing lower side sealing surface (or another side sealing surface of casing), 41 - first drain recovery space (or simply drain recovery space), 41u - upper side first space defining surface, 41d - lower side first space defining surface, 41i - inner side first space defining surface, 41o - outer side first space defining surface, 42 - second drain recovery space, 42u - upper side second space defining surface, 42i - inner side second space defining surface, 42o - outer side second space defining surface, 43 - third drain recovery space, 45, 45a - first drain discharge passage (or drain discharge passage), 46 - second drain discharge passage, 47 - third drain discharge passage, 50 - sealing member, 60, 60a - final stage stationary blade segment, 60u - upper side stationary blade segment, 61 - stationary blade, 62 - cavity, 63 - blade face drain passage, 70, 70a - outer blade ring, 71 - blade ring main body, 72 - gas passage surface, 73 - reverse gas passage surface, 74 - blade ring rear end surface, 75 - blade face drain recovery passage, 76 - gas passage surface drain recovery passage, 77 - drain groove, 80, 80a - blade ring convex portion, 80u - upper side blade ring convex portion (another blade ring convex portion), 80ua - upper side blade ring convex portion (one blade ring convex portion), 80d - lower side blade ring convex portion (one blade ring convex portion), 80da - lower side blade ring convex portion (another blade ring convex portion), 81ua - blade ring upper side facing surface, 81d, 81db - blade ring lower side facing surface, 82u - blade ring upper side sealing surface,82ua - blade ring upstream side seal face (or simply seal face), 82d, 82db - blade ring downstream side seal face (or simply seal face), 82da - blade ring downstream side seal face, 83, 83a, 83b, 83c - seal groove, Co - condenser, FP - steam flow path, ST - steam turbine, Ar - axial line, Da - axial direction, Dau - upstream side of axial line, Dad - downstream side of axial line, Dc - circumferential direction, Dr - radial direction, Dri - radially inner side, Dro - radially outer side.

Claims

1. A stator vane segment, comprising: an outer vane ring extending in a circumferential direction with respect to an axis; and a seal member that is a member different from the outer vane ring, the plurality of stator vanes each having a cavity formed in an interior thereof and a vane face drain passage that communicates a surface thereof with the cavity, the outer vane ring having a vane ring main body and two vane ring protrusions, the vane ring main body having a gas passage face that extends in the circumferential direction and faces the radially inner side, an inverse gas passage face that extends in the circumferential direction and has a back-to-back relationship with the gas passage face, and a vane face drain recovery passage, the two vane ring protrusions protruding from the inverse gas passage face toward a radially outer side with respect to the axis and extending in the circumferential direction, and being spaced apart from each other in an axis direction in which the axis extends, and forming a drain recovery space in cooperation with a casing present on an outer circumferential side of the vane ring main body between the two vane ring protrusions, the vane face drain recovery passage extending from the cavity toward the radially outer side and opening at a position between the two vane ring protrusions in the inverse gas passage face, one of the two vane ring protrusions having a seal face, the seal member being disposed between a portion of the casing and the seal face of the one vane ring protrusion and being in contact with the seal face, only a portion of one casing protrusion protruding from a casing main body of the casing toward the radially inner side and extending in the circumferential direction, the only portion of the one casing protrusion entering between the two vane ring protrusions, so that the two vane ring protrusions form the drain recovery space in cooperation with the casing between the two vane ring protrusions.

2. The stator vane segment according to claim 1, wherein the vane ring main body has a gas passage face drain recovery passage that extends from the gas passage face toward the radially outer side and opens at a position between the two vane ring protrusions in the inverse gas passage face. Multiple stationary blades extend radially inward from the outer blades relative to the axis and are arranged along the circumferential direction; 3. The stator vane segment according to claim 1 or 2, wherein the vane ring main body has a drain groove at a position more upstream of an axis upstream side than an upstream side vane ring protrusion of the two vane ring protrusions that is on one of two sides in the axis direction, the drain groove being recessed from the inverse gas passage face toward the radially inner side and extending in the circumferential direction.

4. A steam turbine, comprising: an outer vane ring having a vane ring main body and two vane ring protrusions, the vane ring main body having a gas passage face that extends in the circumferential direction and faces the radially inner side, an inverse gas passage face that extends in the circumferential direction and has a back-to-back relationship with the gas passage face, and a vane face drain recovery passage, and a plurality of stator vanes each having a cavity formed in an interior thereof and a vane face drain passage that communicates a surface thereof with the cavity. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A stationary vane segment includes: an outer vane ring extending in a circumferential direction with respect to an axis; a plurality of stationary vanes extending from the outer vane ring to a radially inner side with respect to the axis and arranged in the circumferential direction; and a seal member that is a member different from the outer vane ring, the plurality of stationary vanes each having: a cavity formed in an inside thereof. ​ ​ and a vane surface drain recovery passage, the two vane ring protrusions protruding from the back gas passage surface toward a radially outer side with respect to the axis and extending along the circumferential direction, and being spaced apart from each other in the axis direction in which the axis extends, and forming a drain recovery space between the two vane ring protrusions in common with a case present on an outer peripheral side of the vane ring main body, the vane surface drain recovery passage extending from the cavity toward the radially outer side and opening at a position between the two vane ring protrusions in the back gas passage surface, one of the two vane ring protrusions having a seal surface, the seal member being disposed between a portion of the case and the seal surface of the one vane ring protrusion and being in contact with the seal surface; and the case covering an outer peripheral side of the stator vane segment, the case having a case main body separated from the stator vane segment toward the radially outer side and extending along the circumferential direction and covering an outer peripheral side of the stator vane segment, at least one case protrusion, and a drain discharge passage, the drain discharge passage extending from the drain recovery space toward the radially outer side and opening on an outer peripheral surface of the case main body, the at least one case protrusion protruding from the case main body toward the radially inner side and extending along the circumferential direction so as to form the drain recovery space between the two vane ring protrusions more radially outward than the back gas passage surface, a portion of the at least one case protrusion overlapping a position of the one of the two vane ring protrusions and the other of the two vane ring protrusions in the radial direction with respect to the axis and being located at a position on one of two sides of the axis direction, an upstream side of the axis and a downstream side of the axis, which is more upstream of the axis than the other vane ring protrusion, the portion of the at least one case protrusion having a case other side seal surface toward the upstream side of the axis, the other vane ring protrusion having a vane ring other side seal surface toward the downstream side of the axis and capable of being in contact with the case other side seal surface, another portion of the at least one case protrusion having a case one side seal surface in contact with the seal member, the one vane ring protrusion having a vane ring one side seal surface spaced apart from and opposing the case one side seal surface as the seal surface, the seal member being disposed between the case one side seal surface and the vane ring one side seal surface.

5. The steam turbine according to claim 4, wherein an upstream side vane ring protrusion of the two vane ring protrusions located on the upstream side of the axis forms the other vane ring protrusion, the upstream side vane ring protrusion has a vane ring upstream side seal surface as the vane ring other side seal surface, the vane ring upstream side seal surface extending along the circumferential direction toward the downstream side of the axis, a downstream side vane ring protrusion of the two vane ring protrusions located more downstream of the axis than the upstream side vane ring protrusion forms the one vane ring protrusion, the downstream-side vane ring protrusion has a vane ring downstream-side seal surface as a vane ring one-side seal surface, the vane ring downstream-side seal surface extending in the circumferential direction toward the axis upstream side or extending in the circumferential direction toward the radial direction outer side, at least a portion of the at least one housing protrusion enters between the two vane ring protrusions, the at least one housing protrusion has an outer side space defining surface, a housing downstream-side seal surface as a housing one-side seal surface, and a housing upstream-side seal surface as a housing other-side seal surface, the outer side space defining surface and an inner side space defining surface, which is a portion of the anti-gas passage surface between the two vane ring protrusions, are diametrically opposed in the radial direction with respect to the axis, the housing upstream-side seal surface is opposed to the vane ring upstream-side seal surface in a manner capable of being in contact with the vane ring upstream-side seal surface, the housing downstream-side seal surface is diametrically opposed to the vane ring downstream-side seal surface, the seal member is disposed between the housing downstream-side seal surface and the vane ring downstream-side seal surface.

6. The steam turbine according to claim 5, wherein the at least a portion of the at least one housing protrusion forms an entry portion that enters between the two vane ring protrusions, the entry portion has a face toward the radial direction inner side, the housing upstream-side seal surface toward the axis upstream side, and a housing downstream-side opposed surface toward the axis downstream side, the face toward the radial direction inner side of the entry portion forms the outer side space defining surface, the housing downstream-side opposed surface of the entry portion is opposed in the axis direction to a portion of the face toward the axis upstream side in the downstream-side vane ring protrusion, that is, a vane ring downstream-side opposed surface, the distance in the axis direction between the housing upstream-side seal surface and the vane ring upstream-side seal surface is smaller than the distance in the axis direction between the housing downstream-side opposed surface and the vane ring downstream-side opposed surface, or is 0.

7. The steam turbine according to claim 6, wherein the upstream-side vane ring protrusion has an upstream-side space defining surface that is located more on the radial direction inner side than the vane ring upstream-side seal surface and that defines an edge of the axis upstream side of the drain water recovery space toward the axis downstream side, the downstream-side vane ring protrusion has a downstream-side space defining surface that is located more on the radial direction inner side than the vane ring downstream-side opposed surface and that defines an edge of the axis downstream side of the drain water recovery space toward the axis upstream side, the upstream-side space defining surface is located more on the axis downstream side than the vane ring upstream-side seal surface, the downstream-side space defining surface is located more on the axis upstream side than the vane ring downstream-side opposed surface.

8. The steam turbine according to claim 6, wherein the downstream-side vane ring protrusion has a seal groove recessed from the vane ring downstream-side opposed surface toward the axis downstream side and extending in the circumferential direction for the seal member to enter, A bottom surface of the seal groove forms the vane ring downstream side seal surface extending in the circumferential direction toward the upstream side of the axis.

9. The steam turbine according to claim 7, wherein The downstream side vane ring boss has a seal groove recessed from the vane ring downstream side opposite surface toward the downstream side of the axis and extending in the circumferential direction for entry of the seal member, A bottom surface of the seal groove forms the vane ring downstream side seal surface extending in the circumferential direction toward the upstream side of the axis.

10. The steam turbine according to any one of claims 4 to 9, wherein The outer side vane ring and the casing are configured to form, in addition to the two vane ring bosses, a second drain recovery space adjacent to the downstream side of the axis of the first drain recovery space between the casing main body and the reverse gas passage surface via the downstream side vane ring boss of the two vane ring bosses located on the downstream side of the axis, The casing main body has a second drain discharge passage extending from the second drain recovery space toward the radial outer side and opening on an outer peripheral surface of the casing main body.

11. The steam turbine according to any one of claims 4 to 9, wherein The stator vane segment is formed of a material having high corrosion resistance to steam as compared to the casing.

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