Stationary blade segment and steam turbine including the same

Abstract

To efficiently discharge drainage in a steam flow passage to the outside of the steam flow passage.SOLUTION: A stationary blade segment includes a blade ring and a stationary blade row held by the blade ring. The blade ring includes a blade groove into which at least part of an outer shroud of each of a plurality of stationary blades of the stationary blade row enters. The outer shroud of each of the plurality of stationary blades of the stationary blade row includes a drainage reservoir groove recessed from a front surface of the outer shroud to an axial downstream side and extending in the circumferential direction. A drainage transfer gap that extends from an edge of an inner peripheral surface of the blade ring to the drainage reservoir groove and that can guide drainage in a steam flow passage to the drainage reservoir groove is formed between an upstream side groove side surface of the blade ring and the front surface of the outer shroud. A minimum gap in the axial direction of the drainage transfer gap is narrower than 1 / 2 of groove depth in the axial direction of the drainage reservoir groove.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a stator vane segment having a plurality of stator vanes, and a steam turbine including the stator vane segment. [Background technology]

[0002] A steam turbine includes a rotor, a plurality of rows of stator blades, and a blade ring (or casing) that holds the plurality of rows of stator blades.

[0003] The rotor has a rotor shaft rotatable about its axis, and a plurality of rotor blade rows attached to the rotor shaft and aligned in the axial direction along which the axis extends. The rotor blade rows are aligned in the axial direction. The stator blade rows are also aligned in the axial direction. Each of the stator blade rows is disposed axially upstream of one of the rotor blade rows. Each of the rotor blade rows has a plurality of rotor blades aligned in the circumferential direction relative to the axis. Each of the stator blade rows has a plurality of stator blades aligned in the circumferential direction.

[0004] If steam drain exists in the steam flow path inside a steam turbine, this drain causes wet loss, so for example, the steam turbine disclosed in Patent Document 1 below has a structure for discharging this drain.

[0005] The outer shroud for each of the plurality of stator vanes (or the outer ring of the plurality of stator vanes) has a gas path surface facing radially inward relative to the axis, a front surface facing upstream relative to the axis, a rear surface facing downstream relative to the axis, an outer surface facing radially outward relative to the axis, and a first drain catcher recessed from the front surface toward the downstream side of the axis.

[0006] The blade ring (or casing) has an inner circumferential surface, an outer circumferential surface, blade grooves recessed radially outward from the inner circumferential surface and extending circumferentially, into which at least a portion of the outer shrouds (or outer rings of the plurality of stator vanes) for each of the plurality of stator vanes is inserted, a second drain catcher, and a drain discharge passage. The blade groove has an upstream groove side surface facing the axial downstream side and facing the front surface of the outer shroud, a downstream groove side surface facing the axial upstream side and facing the rear surface of the outer shroud, and a groove bottom surface facing radially inward and facing the outer peripheral surface of the outer shroud. The second drain catcher is recessed axially upstream from the upstream groove side surface. The drain discharge passage extends radially outward from the second drain catcher.

[0007] A drain recovery space is formed between the upstream groove side surface of the blade groove and the front surface of the outer shroud, radially inward of the radially outer edge of the second drain catcher, into which drain droplets in the steam flow path can flow in. The axial spacing of this drain recovery space is wider than the axial groove depth of the first drain catcher. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-031723 Summary of the Invention [Problem to be solved by the invention]

[0009] In a steam turbine, it is desirable to discharge as much of the drainage in the steam flow path as possible to the outside of the steam flow path, thereby suppressing wet loss due to the drainage.

[0010] Therefore, an object of the present disclosure is to provide a technology that can efficiently discharge drainage in a steam flow path to the outside of the steam flow path and suppress wet loss due to the drainage. [Means for solving the problem]

[0011] In order to achieve the above object, a stator vane segment according to one aspect of the disclosure comprises: The turbine comprises a blade ring having an annular cross section perpendicular to the axis and forming a steam flow path on its inner circumferential side through which steam can flow, and a stator vane row held by the blade ring. The stator vane row has a plurality of stator vanes arranged in a circumferential direction about the axis. Each of the plurality of stator vanes has a blade body extending in a radial direction about the axis, and an outer shroud provided on the radially outer side of the blade body in the radial direction between the radially inner side and the radially outer side. The outer shroud has a gas path surface facing the radially inner side, a counter-gas path surface facing the radially outer side, a front surface facing the axial upstream side and an axial downstream side in the axial direction in which the axis extends, and a rear surface facing the axial downstream side. The blade ring has an inner circumferential surface facing radially inward, an outer circumferential surface facing radially outward, blade grooves recessed radially outward from the inner circumferential surface and extending in the circumferential direction, with at least a portion of the outer shroud for each of the plurality of stator vanes inserted therein, and a drain discharge flow passage. The blade grooves have an upstream groove side facing the axial downstream side and opposing the front surface of each of the plurality of stator vanes, a downstream groove side facing the axial upstream side and opposing the rear surface of each of the plurality of stator vanes, and a groove bottom surface facing radially inward and opposing the anti-gas path surface of each of the plurality of stator vanes. Only one of the blade ring and the outer shroud for each of the plurality of stator vanes has a drain collection groove recessed in a surface facing the other member in the axial direction from the other member side to the one member side in the axial direction and extending in the circumferential direction. A drain transfer gap is formed between the upstream groove side surface of the blade ring and the front surface of the outer shroud of each of the plurality of stator vanes, extending in the radial direction from the edge of the inner circumferential surface of the blade ring to the drain accumulation groove and capable of guiding drain in the steam flow path to the drain accumulation groove. The drain discharge passage is connected to the drain accumulation groove and is configured to be able to discharge drain in the drain accumulation groove to the outer circumferential side of the blade ring. The minimum gap in the axial direction in the drain transfer gap is narrower than 1 / 2 the groove depth of the drain accumulation groove in the axial direction.

[0012] In this aspect, the drain located axially upstream of the stator blade row in the steam flow path flows into the drain accumulation groove through the drain transfer gap, and the drain in the drain accumulation groove is discharged to the outer periphery of the blade ring through the drain discharge flow path.

[0013] In the technology described in Patent Document 1, explained in the "Background Art" section, as mentioned above, the outer shroud of the stator vane has a first drain catcher recessed axially downstream from the front surface of the outer shroud. The blade ring also has a blade groove into which the outer shroud fits, a second drain catcher recessed axially upstream from the upstream groove side surface of the blade groove, and a drain discharge flow passage extending radially outward from the second drain catcher. A drain collection space into which drain droplets from the steam flow passage can flow is formed between the upstream groove side surface of the blade groove and the front surface of the outer shroud, radially inward of the radially outer edge of the second drain catcher. The axial spacing of this drain collection space is wider than the axial groove depth of the first drain catcher.

[0014] In the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively large drain droplets, the drain droplets are blown radially outward by centrifugal force and flow into the drain collection space, and then discharged to the outer periphery of the blade ring via the first drain catcher, the second drain catcher, and the drain discharge passage. However, in the technology described in Patent Document 1, the axial spacing of the drain collection space is wider than the axial groove depth of the first drain catcher, so there is essentially no pressure difference between the pressure in the steam flow path and the pressure in the first drain catcher. Therefore, in the technology described in Patent Document 1, a suction force due to the pressure difference does not substantially act on the drain in the steam flow path from the first drain catcher side. Therefore, in the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively small drain droplets, even if centrifugal force acts on the drain droplets, the centrifugal force is so small that the drain droplets may not reach the first drain catcher. Furthermore, there is a risk that the drain adhering to the inner peripheral surface of the blade ring will not reach the first drain catcher.

[0015] In this embodiment, the minimum axial gap of the drain transfer gap is narrower than half the axial depth of the drain sump groove. This ensures a pressure difference between the pressure in the steam flow path and the pressure in the drain sump groove. That is, if the outer peripheral side of the blade ring is under negative pressure, the pressure in the drain sump groove is clearly lower than the pressure in the steam flow path. Therefore, in this embodiment, a suction force due to the pressure difference acts on the drain in the steam flow path from the drain sump groove side, making it easier for the drain in the steam flow path to flow into the drain sump groove. Therefore, in this embodiment, even if some of the drain adhering to the blades in the steam flow path breaks down into relatively small drain droplets, the suction force due to the pressure difference can guide these drain droplets into the drain sump groove. Furthermore, in this embodiment, the drain adhering to the inner peripheral surface of the blade ring can also be guided into the drain sump groove by the suction force due to the pressure difference.

[0016] Therefore, in this aspect, the drain in the steam flow path can be efficiently discharged to the outside of the steam flow path, and wet loss due to the drain can be suppressed.

[0017] In order to achieve the above object, a steam turbine according to one aspect of the disclosure includes: The turbine includes the stator vane segment according to the above aspect, and a rotor rotatable about the axis on the inner peripheral side of the blade ring. [Effects of the Invention]

[0018] According to one aspect of the present disclosure, the drain in the steam flow path can be efficiently discharged to the outside of the steam flow path, thereby suppressing wet loss due to the drain. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an overall cross-sectional view of a steam turbine in an embodiment according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the blade ring and its surroundings in the first embodiment according to the present disclosure. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4]FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 3 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 4 is a cross-sectional view taken along a plane perpendicular to the axis of a vane segment in a modified example of the first embodiment according to the present disclosure. [Figure 7] FIG. 10 is a cross-sectional view of the blade ring and its surroundings in a second embodiment according to the present disclosure. [Figure 8] FIG. 8 is an enlarged view of a portion IIX in FIG. 7. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. [Figure 10] FIG. 4 is a cross-sectional view of the blade ring and its surroundings in a modified example of the first embodiment according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments and various modifications of the present disclosure will be described with reference to the drawings.

[0021] "Steam turbine embodiment" An embodiment of a steam turbine including a stator vane segment according to the present disclosure will be described in detail with reference to FIGS.

[0022] The steam turbine in this embodiment is a two-flow steam turbine, as shown in FIG. 1 . This steam turbine includes a first steam turbine section ST1 and a second steam turbine section ST2. Each of the first steam turbine section ST1 and the second steam turbine section ST2 includes a rotor 10 rotating about an axis Ar, a casing 20 covering the rotor 10, three blade rings 30 arranged in the casing 20, one or more stator vane rows 50 held by each blade ring 30, a bearing 15, and a steam inlet pipe 16. The rotor 10 of the first steam turbine section ST1 and the rotor 10 of the second steam turbine section ST2 are located on the same axis Ar and are connected to each other so as to be rotatable together. For convenience of the following explanation, the direction in which the axis Ar extends is referred to as the axial direction Da. Furthermore, one of the two sides of the axial direction Da is referred to as a first side Da1, and the other is referred to as a second side Da2.

[0023] The first steam turbine section ST1 and the second steam turbine section ST2 share a steam inlet pipe 16. In the first steam turbine section ST1, components other than the steam inlet pipe 16 are arranged on a first side Da1 in the axial direction Da with respect to the steam inlet pipe 16. In the first steam turbine section ST1, the second side Da2 forms the axial upstream side Dau, and the first side Da1 forms the axial downstream side Dad. In the second steam turbine section ST2, components other than the steam inlet pipe 16 are arranged on the second side Da2 with respect to the steam inlet pipe 16. In the second steam turbine section ST2, the first side Da1 forms the axial upstream side Dau, and the second side Da2 forms the axial downstream side Dad. The first steam turbine section ST1 and the second steam turbine section ST2 have the same shape and structure. However, the axial upstream side Dau in the second steam turbine section ST2 is on the opposite side in the axial direction Da from the axial upstream side Dau in the first steam turbine section ST1.

[0024] Each rotor 10 in the first steam turbine section ST1 and the second steam turbine section ST2 has a rotor shaft 11 extending in an axial direction Da about the axis Ar, and a plurality of rotor blade rows 12 fixed to the outer periphery of the rotor shaft 11 and arranged in the axial direction Da. The number of the rotor blade rows 12 is, for example, seven. A bearing 15 that rotatably supports the rotor shaft 11 is provided on the axial downstream side Dad of the rotor shaft 11. Each rotor blade row 12 has a plurality of rotor blades arranged in a circumferential direction Dc about the axis Ar. The rotor blades have a blade-shaped cross section perpendicular to a radial direction Dr about the axis Ar, and have blade bodies extending in the radial direction Dr. A plurality of stator blade rows 50 are arranged in the axial direction Da. One of the plurality of stator blade rows 50 is arranged at a position Dau on the axial upstream side of each rotor blade row 12. Therefore, the number of the plurality of stator blade rows 50 matches the number of the plurality of moving blade rows. Therefore, when the number of the plurality of moving blade rows is 7, the number of the plurality of stator blade rows is also 7. Each stator blade row 50 has a plurality of stator blades arranged in the circumferential direction Dc.

[0025] As shown in FIG. 2 , the stator blade 51 has a blade body 52, an inner shroud 54, and an outer shroud 57. The blade body 52 has a blade-shaped cross section perpendicular to the radial direction Dr, and extends in the radial direction Dr. The inner shroud 54 is provided at the end of the radially inner side Dri of the blade body 52. ​​The outer shroud 57 is provided at the end of the radially outer side Dro of the blade body 52. ​​A part of the steam flow path 17 through which steam S flows is formed between the inner shroud 54 and the outer shroud 57. Therefore, the blade body 52 is disposed within this steam flow path 17.

[0026] Each of the three blade rings 30 has a cylindrical shape centered on the axis Ar. As shown in FIG. 1 , the three blade rings 30 are aligned in the axial direction Da. As shown in FIG. 2 , the first blade ring 30a, which is the blade ring 30 located furthest upstream along the axis Dau, is fitted with a first stage stator blade row 50a, a second stage stator blade row 50b, a third stage stator blade row 50c, a fourth stage stator blade row 50d, and a fifth stage stator blade row 50e, among the multiple stator blade rows 50. As shown in FIG. 1 , the second blade ring 30b, which is adjacent to the axial downstream side Dad of the first blade ring 30a, is fitted with the sixth stage stator blade row 50. The third blade ring 30c, which is adjacent to the axial downstream side Dad of the second blade ring 30b, is fitted with the seventh stage stator blade row 50.

[0027] As shown in Fig. 1, each of the casings 20 in the first steam turbine section ST1 and the second steam turbine section ST2 has an inner casing 21, an exhaust casing 22, and a diffuser 23. The inner casing 21 is cylindrical and has an axis Ar as its center. Three blade rings 30 are attached to the inner peripheral side of the inner casing 21.

[0028] The diffuser 23 is annular with respect to the axis Ar and defines a diffuser space 23s that gradually widens radially outward Dro toward the axial downstream side Dad. Steam S that has passed through the seventh stage rotor blade row 12, which is the final stage rotor blade row, flows into the diffuser space 23s.

[0029] The exhaust casing 22 has an exhaust port 27. This exhaust port 27 opens radially outward Dro from the interior and vertically downward. A condenser C that converts the steam S back into water is connected to this exhaust port 27. The exhaust casing 22 forms an exhaust space 22s through which the steam S flows after passing through the diffuser space 23s. This exhaust space 22s extends around the outer periphery of the diffuser 23 in the circumferential direction Dc relative to the axis Ar, and guides the steam S that flows in from the diffuser space 23s to the exhaust port 27.

[0030] The exhaust casing 22 of the first steam turbine section ST1 and the exhaust casing 22 of the second steam turbine section ST2 are connected to each other and integrated together.

[0031] The steam inlet pipe 16 has a cylindrical shape centered on a pipe axis Ap. The pipe axis Ap passes through an intermediate position in the axial direction Da between the first stage stator vane row 50a of the first steam turbine section ST1 and the first stage stator vane row 50a of the second steam turbine section ST2, and extends vertically. The steam inlet pipe 16 is disposed above the axis Ar. The steam inlet pipe 16 guides steam S from the outside into the inner casing 21 of the first steam turbine section ST1 and the inner casing 21 of the second steam turbine section ST2.

[0032] 2, each of the three blade rings 30 including the first blade ring 30a has an inner circumferential surface 31i facing the radially inward direction Dri, an outer circumferential surface 31o facing the radially outward direction Dro, and a blade groove 32 into which the outer shroud 57 of the stator vane row 50 held by the blade ring 30 fits. Each of the three blade rings 30 forms the aforementioned steam flow passage 17 on the inner circumferential side through which steam can flow. The blade groove 32 is recessed from the inner circumferential surface 31i of the blade ring 30 toward the radially outward direction Dro and extends in the circumferential direction Dc. The first blade ring 30a has, as blade grooves 32, a first stage blade groove 32a into which the outer shroud 57 of the first stage stator blade row 50a fits, a second stage blade groove 32b into which the outer shroud 57 of the second stage stator blade row 50b fits, a third stage blade groove 32c into which the outer shroud 57 of the third stage stator blade row 50c fits, a fourth stage blade groove 32d into which the outer shroud 57 of the fourth stage stator blade row 50d fits, and a fifth stage blade groove 32e into which the outer shroud 57 of the fifth stage stator blade row 50e fits. Furthermore, this first blade ring 30a has a drain discharge flow passage 35 that discharges steam drain from the radially inner side Dri to the radially outer side Dro.

[0033] As shown in Figures 3 and 4, each of the blade bodies 52 of each of the multiple stator blades 51 in each stator blade row 50 has a leading edge 52f located at the axially most upstream side Dau of the blade body 52, a trailing edge 52r located at the axially most downstream side Dad of the blade body 52, and a pressure surface 52p and a suction surface 52n connecting the leading edge 52f and the trailing edge 52r. The pressure surface 52p is a concave surface facing the circumferential first side Dc1 of the circumferential first side Dc1 and the circumferential second side Dc2 in the circumferential direction Dc and recessed toward the circumferential second side Dc2. The suction surface 52n is a convex surface facing the circumferential second side Dc2 and protruding toward the circumferential second side Dc2. The suction surface 52n is back-to-back with the pressure surface 52p.

[0034] Each of the outer shrouds 57 of the multiple stator blades 51 in each stator blade row 50 has a gas path surface 58p facing the radially inner side Dri, a counter gas path surface 58pa facing the radially outer side Dro and back-to-back with the gas path surface 58p, a front surface 58f facing the axial upstream side Dau, a rear surface 58r facing the axial downstream side Dad, a first side surface 58a facing the circumferential first side Dc1, and a second side surface 58b facing the circumferential second side Dc2.

[0035] The outer shrouds 57 of each of the plurality of stator vanes 51 in each of the second stage stator vane row 50b, the third stage stator vane row 50c, the fourth stage stator vane row 50d, and the fifth stage stator vane row 50e further have drain grooves 59. These drain grooves 59 are recessed from a front surface 58f of the outer shroud 57 downstream of the axis and extend in the circumferential direction Dc. The drain grooves 59 of each of the plurality of stator vanes 51 are aligned in the circumferential direction Dc so as to be connected to one another.

[0036] Each of the inner shrouds 54 of the multiple stator blades 51 in each stator blade row 50 has a gas path surface 55p facing the radially inner side Dri, a counter gas path surface 55pa facing the radially outer side Dro and back-to-back with the gas path surface 55p, a front surface 55f facing the axial upstream side Dau, a rear surface 55r facing the axial downstream side Dad, a first side surface 55a facing the circumferential first side Dc1, and a second side surface 55b facing the circumferential second side Dc2.

[0037] Each of the blade grooves 32 of the three blade rings 30 has an upstream groove side surface 33u facing the axial downstream side Dad, a downstream groove side surface 33d facing the axial upstream side Dau, and a groove bottom surface 33b facing the radially inward side Dri. The upstream groove side surface 33u of the blade groove 32 faces a front surface 58f of the outer shroud 57 of each of the multiple stator vanes 51 in the axial direction Da. The downstream groove side surface 33d of the blade groove 32 faces a rear surface 58r of the outer shroud 57 of each of the multiple stator vanes 51 in the axial direction Da. The groove bottom surface 33b of the blade groove 32 faces a counter-gas path surface 58pa of the outer shroud 57 of each of the multiple stator vanes 51 in the radial direction Dr.

[0038] A drain transfer gap 60 is formed between the upstream groove side surface 33u of the third-stage blade groove 32c and front surfaces 58f of the multiple outer shrouds 57 fitted into this third-stage blade groove 32c, which is capable of guiding drain in the steam flow path 17 to the drain accumulation grooves 59 of the multiple outer shrouds 57 fitted into this third-stage blade groove 32c. This drain transfer gap 60 has a minimum gap portion 61 extending from an edge of the radially inner Dri of the drain accumulation groove 59 toward the radially inner Dri, and a drain introduction gap 62 extending from the edge of the radially inner Dri of the minimum gap portion 61 toward the radially inner Dri to the edge of the inner circumferential surface 31i of the blade ring 30.

[0039] The gap in the axial direction Da at the minimum gap portion 61 is a minimum gap Gmin that indicates the smallest value in the axial direction Da at the drain transfer gap 60. This minimum gap Gmin is narrower than ½ of the groove depth d in the axial direction Da of the drain accumulation groove 59. Specifically, in this embodiment, this minimum gap Gmin is 2 mm or less.

[0040] The spacing in the axial direction Da of the drain introduction gap 62 gradually increases toward the radially inner side Dri. Therefore, within the upstream groove side surface 33u of the third-stage blade groove 32c, the drain introduction groove side surface 33ug, which defines the drain introduction gap 62, is inclined with respect to the radial direction Dr so as to move toward the axial upstream side Dau as it moves toward the radially inner side Dri. In other words, the drain introduction groove side surface 33ug is inclined with respect to the radial direction Dr so as to gradually move toward the axial downstream side Dad as it moves toward the radially outer side Dro. The spacing in the axial direction Da at the edge of the radially inner side Dri of the drain introduction gap 62 is a maximum gap representing the maximum value of the axial direction Da of the drain transfer gap 60. This maximum spacing is narrower than the groove depth d of the drain accumulation groove 59 in the axial direction Da.

[0041] At a position Dro radially outward of the drainage groove 59, the distance in the axial direction Da between the upstream groove side surface 33u of the third-stage blade groove 32c and front surfaces 58f of the outer shrouds 57 fitted into this third-stage blade groove 32c is narrower than the minimum gap Gmin. The upstream groove side surface 33u of the third-stage blade groove 32c and the front surfaces 58f of the outer shrouds 57 fitted into this third-stage blade groove 32c are in contact with each other. Therefore, the outer shrouds 57 fitted into the third-stage blade groove 32c cannot move in the axial direction Da relative to the third-stage blade groove 32c.

[0042] The outer shroud 57 of at least one of the plurality of stator vanes 51 included in the third-stage stator vane row 50c has a stator vane discharge passage 59p. Here, at least one of the stator vanes 51 is a drain discharge stator vane 51D. The stator vane discharge passage 59p extends from the drain accumulation groove 59 in the outer shroud 57 of the drain discharge stator vane 51D to an opposite-gas path surface 58pa of the outer shroud 57 of the drain discharge stator vane 51D and opens at the opposite-gas path surface 58pa.

[0043] 2, a drain transfer gap 60 is also formed between the upstream groove side surface 33u of the second-stage blade groove 32b and the front surfaces 58f of the plurality of outer shrouds 57 fitted into this second-stage blade groove 32b, which is capable of guiding drain in the steam flow path 17 to the drain accumulation grooves 59 of the plurality of outer shrouds 57 fitted into the second-stage blade groove 32b. The outer shroud 57 of the drain discharge vane 51D, which is at least one vane 51 among the plurality of vanes 51 included in the second-stage stator vane row 50b, also has a vane discharge flow path 59p.

[0044] Furthermore, a drain transfer gap 60 is also formed between the upstream groove side surface 33u of the fourth-stage blade groove 32d and front surfaces 58f of the plurality of outer shrouds 57 fitted into this fourth-stage blade groove 32d, which is capable of guiding drain in the steam flow passage 17 to the drain accumulation grooves 59 of the plurality of outer shrouds 57 fitted into the fourth-stage blade groove 32d. The outer shroud 57 of the drain discharge vane 51D, which is at least one vane 51 among the plurality of vanes 51 included in the fourth-stage stator vane row 50d, also has a vane discharge flow passage 59p.

[0045] Furthermore, a drain transfer gap 60 is also formed between the upstream groove side surface 33u of the fifth-stage blade groove 32e and the front surfaces 58f of the plurality of outer shrouds 57 fitted into this fifth-stage blade groove 32e, which is capable of guiding drain in the steam flow passage 17 to the drain accumulation grooves 59 of the plurality of outer shrouds 57 fitted into the fifth-stage blade groove 32e. The outer shroud 57 of the drain discharge vane 51D, which is at least one vane 51 among the plurality of vanes 51 included in the fifth-stage stator vane row 50e, also has a vane discharge flow passage 59p.

[0046] The drain discharge passage 35 of the first blade ring 30a has a second stage inner passage 37b, a third stage inner passage 37c, a fourth stage inner passage 37d, a fifth stage inner passage 37e, an inter-row collecting passage 38, and an outer discharge passage 39.

[0047] The second-stage inner flow passage 37b communicates with the stator vane discharge passage 59p of the drain discharge stator vane 51D in the second-stage stator vane row 50b and extends radially outward from the stator vane discharge passage 59p Dro. The third-stage inner flow passage 37c communicates with the stator vane discharge passage 59p of the drain discharge stator vane 51D in the third-stage stator vane row 50c and extends radially outward from the stator vane discharge passage 59p Dro. The fourth-stage inner flow passage 37d communicates with the stator vane discharge passage 59p of the drain discharge stator vane 51D in the fourth-stage stator vane row 50d and extends radially outward from the stator vane discharge passage 59p Dro. The fifth-stage inner flow passage 37e communicates with the stator vane discharge passage 59p of the drain stator vane 51D in the fifth-stage stator vane row 50e and extends from this stator vane discharge passage 59p in the radially outward direction Dro. The interrow collecting passage 38 extends in a direction having a radial direction Dr component and communicates with the second-stage inner flow passage 37b, the third-stage inner flow passage 37c, the fourth-stage inner flow passage 37d, and the fifth-stage inner flow passage 37e. The outer discharge passage 39 communicates with the interrow collecting passage 38 and opens at the outer peripheral surface 31o of the blade ring 30.

[0048] In this embodiment, as shown in FIG. 5 , the number of second-stage inner flow passages 37b communicating with the stator vane discharge flow passages 59p of the drain discharge stator vanes 51D of the second-stage stator vane row 50b, the number of third-stage inner flow passages 37c communicating with the stator vane discharge flow passages 59p of the drain discharge stator vanes 51D of the third-stage stator vane row 50c, the number of fourth-stage inner flow passages 37d communicating with the stator vane discharge flow passages 59p of the drain discharge stator vanes 51D of the fourth-stage stator vane row 50d, and the number of fifth-stage inner flow passages 37e communicating with the stator vane discharge flow passages 59p of the drain discharge stator vanes 51D of the fifth-stage stator vane row 50e are all six. For this reason, in this embodiment, the number of drain discharge vanes 51D in the second stage stator vane row 50b, the number of drain discharge vanes 51D in the third stage stator vane row 50c, the number of drain discharge vanes 51D in the fourth stage stator vane row 50d, and the number of drain discharge vanes 51D in the fifth stage stator vane row 50e are each six.

[0049] Of the six drain discharge stator vanes 51D that each stage stator vane row 50 has, three of them are above the axis Ar. Of the six drain discharge stator vanes 51D that each stage stator vane row 50 has, the remaining three of them are below the axis Ar. In this relationship, of the six second-stage inner flow passages 37b, three of the second-stage inner flow passages 37b are above the axis Ar, and the remaining three of the second-stage inner flow passages 37b are below the axis Ar. Of the six third-stage inner flow passages 37c, three of the third-stage inner flow passages 37c are above the axis Ar, and the remaining three of the third-stage inner flow passages 37c are below the axis Ar. Of the six fourth-stage inner flow passages 37d, three fourth-stage inner flow passages 37d are above the axis Ar, and the remaining three fourth-stage inner flow passages 37d are below the axis Ar. Of the six fifth-stage inner flow passages 37e, three fifth-stage inner flow passages 37e are above the axis Ar, and the remaining three fifth-stage inner flow passages 37e are below the axis Ar.

[0050] The stator vane segment VS in this embodiment has the above-described first blade ring 30a and a plurality of stator vane rows 50 held by this first blade ring 30a.

[0051] In this embodiment, the first stator vane row 50 is the third-stage stator vane row 50c, and the second stator vane row 50 is the fourth-stage stator vane row 50d. Therefore, in this embodiment, the first blade groove 32 is the third-stage blade groove 32c, and the second blade groove 32 is the fourth-stage blade groove 32d. However, the first stator vane row 50 and the second stator vane row 50 may be composed of any two of the stator vane rows 50 from the first-stage stator vane row 50a to the fifth-stage stator vane row 50e in this embodiment. That is, for example, in this embodiment, the first stator vane row 50 may be the second-stage stator vane row 50b and the second stator vane row 50 may be the third-stage stator vane row 50c, or the first stator vane row 50 may be the fourth-stage stator vane row 50d and the second stator vane row 50 may be the fifth-stage stator vane row 50e.

[0052] 3 , in the steam flow passage 17, a portion of the drain water on the axial upstream side Dau of the third-stage stator vane row 50c flows into drain accumulation grooves 59 of the outer shrouds 57 of the plurality of stator vanes 51 of the third-stage stator vane row 50c through a drain transfer gap 60 between the third-stage blade groove 32c and the outer shrouds 57 of the plurality of stator vanes 51 of the third-stage stator vane row 50c. The drain water in the drain accumulation grooves 59 is discharged to the outer periphery of the blade ring 30 through a drain discharge flow passage 35.

[0053] In the technology described in Patent Document 1, explained in the "Background Art" section, as mentioned above, the outer shroud of the stator vane has a first drain catcher recessed from the front surface of the outer shroud toward the axial downstream side Dad. The blade ring also has a blade groove into which the outer shroud fits, a second drain catcher recessed from the upstream groove side surface of the blade groove toward the axial upstream side Dau, and a drain discharge flow path extending from the second drain catcher to the radially outer side Dro. A drain collection space into which drain droplets from the steam flow path can flow is formed between the upstream groove side surface of the blade groove and the front surface of the outer shroud, radially inward Dri of the edge of the radially outer side Dro of the second drain catcher. The distance in the axial direction Da of this drain collection space is wider than the groove depth in the axial direction Da of the first drain catcher.

[0054] In the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively large drain droplets, the drain droplets are blown radially outward by centrifugal force, flow into the drain collection space, and then discharged to the outer periphery of the blade ring via the first drain catcher, the second drain catcher, and the drain discharge passage. However, in the technology described in Patent Document 1, the spacing in the axial direction Da between the drain collection spaces is wider than the groove depth in the axial direction Da of the first drain catcher, so there is essentially no pressure difference between the pressure in the steam flow path and the pressure in the first drain catcher. Therefore, in the technology described in Patent Document 1, a suction force due to the pressure difference does not substantially act on the drain in the steam flow path from the first drain catcher side. Therefore, in the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively small drain droplets, even if centrifugal force acts on the drain droplets, the centrifugal force is so small that the drain droplets may not reach the first drain catcher. Furthermore, there is a risk that the drain adhering to the inner peripheral surface of the blade ring will not reach the first drain catcher.

[0055] In this embodiment, the minimum gap Gmin in the axial direction Da of the drain transfer gap 60 is narrower than half the groove depth d of the drain reservoir groove 59 in the axial direction Da. Therefore, a pressure difference is reliably generated between the pressure in the steam flow path 17 and the pressure in the drain reservoir groove 59. That is, if the outer peripheral side of the blade ring 30 is under negative pressure, the pressure in the drain reservoir groove 59 will be clearly lower than the pressure in the steam flow path 17. Therefore, in this embodiment, a suction force due to the pressure difference acts on the drain in the steam flow path 17 from the drain reservoir groove 59 side, making it easier for the drain in the steam flow path 17 to flow into the drain reservoir groove 59. Therefore, in this embodiment, even if some of the drain adhering to the rotor blades in the steam flow path 17 breaks down into relatively small drain droplets, the suction force due to the pressure difference can guide these drain droplets into the drain reservoir groove 59. Furthermore, in this embodiment, drainage water adhering to the inner circumferential surface 31i of the blade ring 30 can also be guided into the drainage groove 59 by the suction force caused by the pressure difference.

[0056] Furthermore, in the present embodiment, the spacing of the drain introduction gap 62 radially inward Dri of the minimum gap 61 in the drain transfer gap 60 is wider than the spacing of the minimum gap 61, and further, the spacing gradually widens toward the radially inward Dri. For this reason, in the present embodiment, the drain Dau axially upstream of the third stage stator blade row 50c in the steam flow path 17 can be easily guided to the minimum gap 61 in the drain transfer gap 60.

[0057] Therefore, in this embodiment, the drain in the steam flow path 17 can be efficiently discharged to the outside of the steam flow path 17, and the wet loss due to the drain can be suppressed.

[0058] In particular, in this embodiment, the minimum gap Gmin is 2 mm or less, and the ratio of the dimension of the minimum gap portion 61 in the radial direction Dr to the minimum gap Gmin is 1 or more, so it is possible to reliably generate a pressure difference between the pressure in the steam flow path 17 and the pressure in the drain accumulation groove 59. Therefore, in this embodiment, the drain in the steam flow path 17 can be discharged to the outside of the steam flow path 17 extremely efficiently.

[0059] Moreover, in this embodiment, there is a high possibility that the minimum gap Gmin of the drain transfer gap 60 will be filled with drain. When part of the drain transfer gap 60 is filled with drain in this way, this drain makes it difficult for the steam in the steam flow path 17 to be discharged to the outer periphery of the blade ring 30. Therefore, in this embodiment, it is possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0060] The drain in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator vanes 51 in the third-stage stator vane row 50c flows into the stator vane discharge passage 59p of the drain discharge stator vane 51D, which is at least one of the plurality of stator vanes 51 in the third-stage stator vane row 50c. Therefore, in this embodiment, the drain in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator vanes 51 in the third-stage stator vane row 50c joins together in the stator vane discharge passage 59p of the drain discharge stator vane 51D, increasing the drain flow rate in this stator vane discharge passage 59p. Therefore, the drain in this stator vane discharge passage 59p makes it difficult for the steam in the steam passage 17 to be discharged to the outer periphery of the blade ring 30. Therefore, in this embodiment, from this perspective as well, it is possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30. The drain in the stator vane discharge passage 59p of the drain discharge stator vane 51D flows into the inner passage 37 that is connected to the stator vane discharge passage 59p in the drain discharge passage 35 formed in the blade ring 30, and is then discharged to the outer periphery of the blade ring 30 via the inter-row collecting passage 38 of the drain discharge passage 35 and the outer discharge passage 39.

[0061] In this embodiment, as described above, the outer shrouds 57 for each of the plurality of stator vanes 51 in each of the second stage stator vane row 50b, the fourth stage stator vane row 50d, and the fifth stage stator vane row 50e also have drain accumulation grooves 59, similar to the outer shrouds 57 for each of the plurality of stator vanes 51 in the third stage stator vane row 50c described above. Moreover, the drain accumulation grooves 59 in each of the second stage stator vane row 50b, the fourth stage stator vane row 50d, and the fifth stage stator vane row 50e are connected to drain transfer gaps 60 that can guide steam in the steam flow passages 17 to these drain accumulation grooves 59. For this reason, in this embodiment, within the steam flow path 17, a portion of the drain Dau on the axial upstream side of the second stage stator blade row 50b, a portion of the drain Dau on the axial upstream side of the fourth stage stator blade row 50d, and a portion of the drain Dau on the axial upstream side of the fifth stage stator blade row 50e can also be extremely efficiently discharged outside the steam flow path 17.

[0062] The drain in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator vanes 51 in the second-stage stator vane row 50b flows into a stator vane discharge passage 59p of a drain discharge stator vane 51D, which is at least one of the plurality of stator vanes 51 in the second-stage stator vane row 50b. The drain in this stator vane discharge passage 59p flows into a second-stage inner passage 37b that communicates with this stator vane discharge passage 59p in a drain discharge passage 35 formed in the blade ring 30, and is then discharged to the outer periphery of the blade ring 30 via the interrow collecting passage 38 of the drain discharge passage 35 and the outer discharge passage 39.

[0063] The drain in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator vanes 51 in the fourth-stage stator vane row 50d flows into a stator vane discharge passage 59p of a drain discharge stator vane 51D, which is at least one of the plurality of stator vanes 51 in the fourth-stage stator vane row 50d. The drain in this stator vane discharge passage 59p flows into a fourth-stage inner passage 37d that communicates with this stator vane discharge passage 59p through a drain discharge passage 35 formed in the blade ring 30, and is then discharged to the outer periphery of the blade ring 30 via the interrow collecting passage 38 of the drain discharge passage 35 and the outer discharge passage 39.

[0064] The drain in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator vanes 51 in the fifth-stage stator vane row 50e flows into a stator vane discharge passage 59p of a drain discharge stator vane 51D, which is at least one of the plurality of stator vanes 51 in the fifth-stage stator vane row 50e. The drain in this stator vane discharge passage 59p flows into a fifth-stage inner passage 37e that is connected to this stator vane discharge passage 59p in a drain discharge passage 35 formed in the blade ring 30, and is then discharged to the outer periphery of the blade ring 30 via the interrow collecting passage 38 of the drain discharge passage 35 and the outer discharge passage 39.

[0065] As described above, in this embodiment, the drains in the drain reservoir grooves 59 of the outer shrouds 57 of each of the plurality of stator blades 51 in each of the second stage stator blade row 50b, the third stage stator blade row 50c, the fourth stage stator blade row 50d, and the fifth stage stator blade row 50e all join together in the interrow collecting passage 38, increasing the drain flow rate in this interrow collecting passage 38. For this reason, the drain in this interrow collecting passage 38 makes it difficult for the steam in the steam passage 17 to be discharged to the outer periphery of the blade ring 30. Therefore, from this perspective as well, this embodiment can suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0066] In this embodiment, the stator vane discharge passages 59p of the drain discharge stator vanes 51D included in each of the second stage stator vane row 50b, the third stage stator vane row 50c, the fourth stage stator vane row 50d, and the fifth stage stator vane row 50e all extend from the center position in the circumferential direction Dc of the drain accumulation groove 59 in the outer shroud 57 of the drain discharge stator vane 51D to the opposite gas path surface 58pa of the outer shroud 57 of the drain discharge stator vane 51D. However, as shown in Fig. 6, the stator vane discharge passages 59p of the drain discharge stator vane 51D may extend radially outward Dro from the end of the drain accumulation groove 59 in the outer shroud 57 of the drain discharge stator vane 51D in the circumferential direction Dc to the opposite gas path surface 58pa of the outer shroud 57 of the drain discharge stator vane 51D. In this case, the outer shroud 57 of the drain discharge stator vane 51D has a stator vane discharge groove 59g that is recessed from one of a first side surface 58a and a second side surface 58b of the outer shroud 57 to the other side surface and extends radially outwardly Dro from the drain accumulation groove 59 in the outer shroud 57 to the anti-gas path surface 58pa. In this case, the stator vane discharge flow path 59p is defined by a plane including the plane that forms the stator vane discharge groove 59g.

[0067] In this embodiment, the stator vane discharge passages 59p of the drain discharge stator vanes 51D of each of the second stage stator vane row 50b, the third stage stator vane row 50c, the fourth stage stator vane row 50d, and the fifth stage stator vane row 50e all open at the anti-gas path surface 58pa of the outer shroud 57 of the drain discharge stator vane 51D. However, the stator vane discharge passages 59p of the drain discharge stator vane 51D may open at the front surface 58f or the rear surface 58r of the outer shroud 57 of the drain discharge stator vane 51D. In this case, the inner passage 37 of the blade ring 30 is formed to communicate with the stator vane discharge passages 59p.

[0068] "Second embodiment of stationary vane segment" A second embodiment of the stator vane segment will be described with reference to FIGS.

[0069] In the stator vane segment VS in the first embodiment, of the blade ring 30 and the outer shroud 57 of the stator vane 51, the outer shroud 57 has the drain reservoir groove 59. However, the blade ring 30 may have the drain reservoir groove 34. In the stator vane segment VS in the present embodiment, the blade ring 30 has the drain reservoir groove 34.

[0070] The stator vane segment VS in this embodiment also has a first blade ring 30a shown in FIG. 1 and a plurality of stator vane rows 50 held by this first blade ring 30a.

[0071] As shown in FIG. 7, the plurality of stator blade rows 50 include a first stage stator blade row 50a, a second stage stator blade row 50b, a third stage stator blade row 50c, a fourth stage stator blade row 50d, and a fifth stage stator blade row 50e.

[0072] Similar to the first blade ring 30a in the first embodiment, the first blade ring 30a has an inner circumferential surface 31i, an outer circumferential surface 31o, and a plurality of blade grooves 32. The blade grooves 32 are recessed from the inner circumferential surface 31i of the blade ring 30 toward the radially outward side Dro and extend in the circumferential direction Dc. The plurality of blade grooves 32 include a first stage blade groove 32a into which the outer shroud 57 of the first stage stator blade row 50a fits, a second stage blade groove 32b into which the outer shroud 57 of the second stage stator blade row 50b fits, a third stage blade groove 32c into which the outer shroud 57 of the third stage stator blade row 50c fits, a fourth stage blade groove 32d into which the outer shroud 57 of the fourth stage stator blade row 50d fits, and a fifth stage blade groove 32e into which the outer shroud 57 of the fifth stage stator blade row 50e fits. This first blade ring 30a also has a drain discharge flow passage 35 that discharges drain of steam from the radially inner side Dri to the radially outer side Dro.

[0073] Furthermore, the first blade ring 30a has a plurality of drain reservoir grooves 34. The plurality of drain reservoir grooves 34 include a drain reservoir groove 34 facing the second stage blade groove 32b, a drain reservoir groove 34 facing the third stage blade groove 32c, a drain reservoir groove 34 facing the fourth stage blade groove 32d, and a drain reservoir groove 34 facing the fifth stage blade groove 32e.

[0074] As shown in FIGS. 8 and 9, each drainage groove 34 is recessed from the upstream groove side surface 33u of the blade groove 32 toward the axial upstream side Dau, and forms an annular shape centered on the axis Ar.

[0075] A drain transfer gap 60 capable of guiding drain in the steam flow passage 17 to the drain accumulation groove 34 facing the second stage blade groove 32b is formed between the upstream groove side surface 33u of the second stage blade groove 32b and front surfaces 58f of the plurality of outer shrouds 57 fitted into this second stage blade groove 32b. A drain transfer gap 60 capable of guiding drain in the steam flow passage 17 to the drain accumulation groove 34 facing the third stage blade groove 32c is formed between the upstream groove side surface 33u of the third stage blade groove 32c and front surfaces 58f of the plurality of outer shrouds 57 fitted into this third stage blade groove 32c. A drain transfer gap 60 capable of guiding drain in the steam flow passage 17 to the drain accumulation groove 34 facing the fourth stage blade groove 32d is formed between the upstream groove side surface 33u of the fourth stage blade groove 32d and front surfaces 58f of the plurality of outer shrouds 57 fitted into this fourth stage blade groove 32d. A drain transfer gap 60 capable of guiding drain in the steam flow passage 17 to the drain accumulation groove 34 facing the fifth stage blade groove 32e is formed between the upstream groove side surface 33u of the fifth stage blade groove 32e and front surfaces 58f of the plurality of outer shrouds 57 fitted into this fifth stage blade groove 32e.

[0076] Each drain transfer gap 60 has a minimum gap portion 61 extending radially inward from the edge of the radially inner Dri of the drain accumulation groove 34, and a drain introduction gap portion 62 extending radially inward from the edge of the radially inner Dri of the minimum gap portion 61 to the edge of the inner circumferential surface 31i of the blade ring 30.

[0077] As in the first embodiment, the gap in the axial direction Da at the minimum gap portion 61 is a minimum gap Gmin that indicates the minimum value in the axial direction Da at the drain transfer gap 60. This minimum gap Gmin is narrower than ½ of the groove depth d in the axial direction Da of the drain accumulation groove 34. Specifically, in this embodiment, this minimum gap Gmin is 2 mm or less.

[0078] As in the first embodiment, the spacing in the axial direction Da of the drain introduction gap 62 gradually increases toward the radially inner side Dri. The spacing in the axial direction Da at the edge of the radially inner side Dri of the drain introduction gap 62 is a maximum gap that indicates the maximum value of the axial direction Da of the drain transfer gap 60. This maximum spacing is narrower than the groove depth d of the drain accumulation groove 34 in the axial direction Da.

[0079] At a position Dro radially outward of the drainage groove 34, the distance in the axial direction Da between the upstream groove side surface 33u of the blade groove 32 and the front surfaces 58f of the outer shrouds 57 fitted into this blade groove 32 is narrower than the minimum gap Gmin. The upstream groove side surface 33u of the blade groove 32 and the front surfaces 58f of the outer shrouds 57 fitted into this blade groove 32 are in contact with each other. Therefore, the outer shrouds 57 fitted into the blade groove 32 cannot move in the axial direction Da relative to the blade groove 32.

[0080] The drain discharge passage 35 of the first blade ring 30a in this embodiment also has a second stage inner passage 37b, a third stage inner passage 37c, a fourth stage inner passage 37d, a fifth stage inner passage 37e, an inter-row collecting passage 38, and an outer discharge passage 39.

[0081] The second-stage inner flow passage 37b communicates with the drain collection groove 34 facing the second-stage blade groove 32b and extends from this drain collection groove 34 to the radially outward direction Dro. The third-stage inner flow passage 37c communicates with the drain collection groove 34 facing the third-stage blade groove 32c and extends from this drain collection groove 34 to the radially outward direction Dro. The fourth-stage inner flow passage 37d communicates with the drain collection groove 34 facing the fourth-stage blade groove 32d and extends from this drain collection groove 34 to the radially outward direction Dro. The fifth-stage inner flow passage 37e communicates with the drain collection groove 34 facing the fifth-stage blade groove 32e and extends from this drain collection groove 34 to the radially outward direction Dro. The inter-row collecting passage 38 extends in a direction having a component in the radial direction Dr, and is connected to the second stage inner passage 37 b, the third stage inner passage 37 c, the fourth stage inner passage 37 d, and the fifth stage inner passage 37 e. The outer discharge passage 39 is connected to the inter-row collecting passage 38, and opens at the outer peripheral surface 31 o of the blade ring 30.

[0082] In this embodiment, the number of second-stage inner flow passages 37b, the number of third-stage inner flow passages 37c, the number of fourth-stage inner flow passages 37d, and the number of fifth-stage inner flow passages 37e are all six, as in the first embodiment.

[0083] As described above, like the stator vane segments VS in the first embodiment, the stator vane segments VS in this embodiment also have drain accumulation grooves 34 and drain transfer gaps 60 that connect the drain accumulation grooves 34 to the steam flow path 17. Therefore, like the first embodiment, this embodiment also makes it possible to efficiently discharge the drain in the steam flow path 17 to the outside of the steam flow path 17, thereby suppressing wet loss due to the drain. Furthermore, this embodiment also makes it possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0084] "Other Modifications" The drain discharge passage 35 of the blade ring 30 in the above embodiment has a plurality of inner passages 37 for each of the plurality of stator blade rows 50, as well as an inter-row collecting passage 38 and an outer discharge passage 39. However, the drain discharge passage 35 of the blade ring 30 may have only a plurality of discharge passages 36 for each of the plurality of stator blade rows 50, as shown in Fig. 10 . Each of the plurality of discharge passages 36 for each of the plurality of stator blade rows 50 communicates with any one of the drain accumulation grooves 59,34 for each of the plurality of stator blade rows 50 and opens at the outer peripheral surface 31o of the blade ring 30. The number of the plurality of discharge passages 36 is six, the same as the number of the plurality of inner passages 37 for each of the plurality of stator blade rows 50 in the above embodiment.

[0085] The number of the plurality of discharge passages 36 for each of the plurality of stator blade rows 50 in the modified example shown in Fig. 10 and the number of the plurality of inner passages 37 for each of the plurality of stator blade rows 50 in the above embodiment do not need to be six. The drain in the annular drain collection grooves 59, 34 flows in a direction having a vertically downward component within the drain collection grooves 59, 34. For this reason, for example, the number of discharge passages 36 or the number of inner passages 37 above the axis Ar may be two, and the number of discharge passages 36 or the number of inner passages 37 below the axis Ar may be three, or the number of discharge passages 36 or the number of inner passages 37 above the axis Ar may be zero, and the number of discharge passages 36 or the number of inner passages 37 below the axis Ar may be two or one.

[0086] Moreover, the steam turbine in the above embodiment has a plurality of blade rings 30. However, the number of blade rings 30 may be one.

[0087] The first blade ring 30a in the above embodiment holds five stator blade rows 50. However, the blade ring 30 may hold one or more stator blade rows 50.

[0088] The present disclosure is not limited to the embodiments described above, and various additions, modifications, substitutions, partial deletions, etc. are possible within the scope of the conceptual idea and spirit of the present invention as derived from the content defined in the claims and their equivalents.

[0089] "Addendum" The vane segments VS in the above-described embodiment and modified examples can be understood, for example, as follows.

[0090] (1) The stator vane segment VS in the first embodiment is The turbine turbine includes a blade ring 30 having an annular cross section perpendicular to the axis Ar and forming a steam flow path 17 on the inner peripheral side through which steam can flow, and a stator vane row 50 held by the blade ring 30. The stator vane row 50 has a plurality of stator vanes 51 arranged in a circumferential direction Dc about the axis Ar. Each of the plurality of stator vanes 51 has a blade body 52 extending in a radial direction Dr about the axis Ar, and an outer shroud 57 provided on the radially outer side Dro of the radially inner side Dri and radially outer side Dro of the blade body 52 in the radial direction Dr. The outer shroud 57 has a gas path surface 58p facing the radially inside Dri, a counter-gas path surface 58pa facing the radially outside Dro, a front surface 58f facing the axial upstream side Dau of the axial upstream side Dau and the axial downstream side Dad in the axial direction Da in which the axis Ar extends, and a rear surface 58r facing the axial downstream side Dad. The blade ring 30 has an inner circumferential surface 31i facing the radially inside Dri, an outer circumferential surface 31o facing the radially outside Dro, blade grooves 32 recessed from the inner circumferential surface 31i toward the radially outside Dro and extending in the circumferential direction Dc, into which at least a portion of the outer shroud 57 for each of the plurality of stator vanes 51 fits, and a drain discharge flow path 35. The blade groove 32 has an upstream groove side surface 33u facing the axial downstream side Dad and facing the front surface 58f of each of the plurality of stator vanes 51, a downstream groove side surface 33d facing the axial upstream side Dau and facing the rear surface 58r of each of the plurality of stator vanes 51, and a groove bottom surface 33b facing the radially inward side Dri and facing the anti-gas path surface 58pa of each of the plurality of stator vanes 51. Only one of the blade ring 30 and the outer shroud 57 of each of the plurality of stator vanes 51 has drain accumulation grooves 59, 34 that are recessed from a surface facing the other member in the axial direction Da from the side of the other member to the side of the one member in the axial direction Da and extend in the circumferential direction Dc. A drain transfer gap 60 is formed between the upstream groove side surface 33u of the blade ring 30 and the front surface 58f of the outer shroud 57 of each of the plurality of stator blades 51, extending in the radial direction Dr from the edge of the inner surface 31i of the blade ring 30 to the drain accumulation grooves 59, 34, and capable of guiding drain in the steam flow path 17 to the drain accumulation grooves 59, 34.The drain discharge passage 35 communicates with the drain retention grooves 59, 34 and is configured to be able to discharge the drain in the drain retention grooves 59, 34 to the outer periphery of the blade ring 30. The minimum gap Gmin in the axial direction Da in the drain transfer gap 60 is narrower than ½ of the groove depth d of the drain retention grooves 59, 34 in the axial direction Da.

[0091] In this embodiment, the drain water on the axially upstream side Dau of the stator blade row 50 in the steam flow passage 17 flows into the drain accumulation grooves 59, 34 through the drain transfer gap 60. The drain water in the drain accumulation grooves 59, 34 is discharged to the outer periphery side of the blade ring 30 through the drain discharge passage 35.

[0092] In the technology described in Patent Document 1, explained in the "Background Art" section, as mentioned above, the outer shroud of the stator vane has a first drain catcher recessed from the front surface of the outer shroud toward the axial downstream side Dad. The blade ring also has a blade groove into which the outer shroud fits, a second drain catcher recessed from the upstream groove side surface of the blade groove toward the axial upstream side Dau, and a drain discharge flow path extending from the second drain catcher to the radially outer side Dro. A drain collection space into which drain droplets from the steam flow path can flow is formed between the upstream groove side surface of the blade groove and the front surface of the outer shroud, radially inward Dri of the edge of the radially outer side Dro of the second drain catcher. The distance in the axial direction Da of this drain collection space is wider than the groove depth in the axial direction Da of the first drain catcher.

[0093] In the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively large drain droplets, the drain droplets are blown radially outward by centrifugal force, flow into the drain collection space, and then discharged to the outer periphery of the blade ring via the first drain catcher, the second drain catcher, and the drain discharge passage. However, in the technology described in Patent Document 1, the spacing in the axial direction Da between the drain collection spaces is wider than the groove depth in the axial direction Da of the first drain catcher, so there is essentially no pressure difference between the pressure in the steam flow path and the pressure in the first drain catcher. Therefore, in the technology described in Patent Document 1, a suction force due to the pressure difference does not substantially act on the drain in the steam flow path from the first drain catcher side. Therefore, in the technology described in Patent Document 1, when some of the drain adhering to the rotor blades in the steam flow path turns into relatively small drain droplets, even if centrifugal force acts on the drain droplets, the centrifugal force is so small that the drain droplets may not reach the first drain catcher. Furthermore, there is a risk that the drain adhering to the inner peripheral surface of the blade ring will not reach the first drain catcher.

[0094] In this embodiment, the minimum gap Gmin in the axial direction Da of the drain transfer gap 60 is narrower than half the groove depth d of the drain reservoir grooves 59, 34 in the axial direction Da. Therefore, a pressure difference is reliably generated between the pressure in the steam flow path 17 and the pressure in the drain reservoir grooves 59, 34. That is, if the outer peripheral side of the blade ring 30 is under negative pressure, the pressure in the drain reservoir grooves 59, 34 will be clearly lower than the pressure in the steam flow path 17. Therefore, in this embodiment, a suction force due to the pressure difference acts on the drain in the steam flow path 17 from the drain reservoir grooves 59, 34 side, making it easier for the drain in the steam flow path 17 to flow into the drain reservoir grooves 59, 34. Therefore, in this embodiment, even if some of the drain adhering to the rotor blades in the steam flow path 17 breaks down into relatively small drain droplets, the suction force due to the pressure difference can guide these drain droplets into the drain reservoir grooves 59, 34. Furthermore, in this embodiment, drainage adhering to the inner circumferential surface 31i of the blade ring 30 can also be guided into the drainage grooves 59, 34 by the suction force caused by the pressure difference.

[0095] Therefore, in this embodiment, the drain in the steam flow path 17 can be efficiently discharged to the outside of the steam flow path 17, and the wet loss due to the drain can be suppressed.

[0096] (2) The stationary vane segment VS in the second embodiment is In the vane segment VS in the first aspect, the minimum gap Gmin is 2 mm or less.

[0097] If the minimum gap Gmin of the drain transfer gap 60 is 2 mm or less, the pressure difference between the pressure in the steam flow path 17 and the pressure in the drain collection grooves 59, 34 becomes large, and the suction force due to the pressure difference acting on the drain in the steam flow path 17 from the drain collection grooves 59, 34 side becomes large. Therefore, in this embodiment, the drain in the steam flow path 17 can be discharged to the outside of the steam flow path 17 extremely efficiently.

[0098] Moreover, in this embodiment, there is a high possibility that the minimum gap Gmin of the drain transfer gap 60 will be filled with drain. When part of the drain transfer gap 60 is filled with drain in this way, this drain makes it difficult for the steam in the steam flow path 17 to be discharged to the outer periphery of the blade ring 30. Therefore, in this embodiment, it is possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0099] (3) The stationary vane segment VS in the third embodiment is In the vane segment VS of the first aspect or the second aspect, the drain transfer gap 60 has a minimum gap portion 61 and a drain introduction gap portion 62 extending from an edge of the radially inner side Dri of the minimum gap portion 61 to an edge of the inner circumferential surface 31i of the blade ring 30. The gap in the axial direction Da at the minimum gap portion 61 is the minimum gap Gmin. The gap in the axial direction Da at the drain introduction gap portion 62 is wider than the minimum gap Gmin.

[0100] In this embodiment, the drain in the steam flow passage 17 can be easily guided into the smallest gap portion 61 in the drain transfer gap 60.

[0101] (4) The stator vane segment VS in the fourth aspect is In the vane segment VS in the third aspect, the ratio of the dimension of the minimum gap portion 61 in the radial direction Dr to the minimum gap Gmin is 1 or more.

[0102] In this embodiment, since the dimension of the minimum gap portion 61 in the radial direction Dr is equal to or greater than a predetermined value, a pressure difference can be reliably generated between the pressure in the steam flow passage 17 and the pressure in the drain accumulation grooves 59, .

[0103] (5) The stator vane segment VS in the fifth aspect is In the vane segment VS in any one of the first to fourth embodiments, at the radially outer side Dro of the drainage grooves 59, 34, the axial distance Da between the upstream groove side surface 33u of the blade ring 30 and the front surface 58f of the outer shroud 57 of each of the plurality of vanes 51 is narrower than the minimum gap Gmin.

[0104] (6) The stator vane segment VS in the sixth aspect is In the stator vane segment VS according to any one of the first to fifth aspects, the one member is the outer shroud 57 for each of the plurality of stator vanes 51, and the other member is the blade ring 30. The outer shroud 57 for each of the plurality of stator vanes 51 has the drain reservoir groove 59. The drain reservoir groove 59 is recessed from the front face 58f of the outer shroud 57 for each of the plurality of stator vanes 51 toward the axial downstream side Dad and extends in the circumferential direction Dc. The drain reservoir grooves 59 for each of the plurality of stator vanes 51 are aligned in the circumferential direction Dc so as to be connected to each other. At least one stator vane 51 of the plurality of stator vanes 51 forms a drain discharge stator vane 51D. The outer shroud 57 of the drain discharge stator vane 51D has a stator vane discharge flow path 59p. The stator vane discharge flow passage 59p extends from the drain accumulation groove 59 in the outer shroud 57 of the drain discharge stator vane 51D to any one of the front surface 58f, the rear surface 58r, and the anti-gas path surface 58pa of the outer shroud 57 of the drain discharge stator vane 51D, opens at the one surface, and is connected to the drain discharge flow passage 35 of the blade ring 30.

[0105] In this embodiment, the drain in the drain reservoir grooves 59 of each of the multiple stator vanes 51 in the stator vane row 50 joins together in the stator vane discharge passage 59p of the drain discharge stator vane 51D, increasing the drain flow rate in this stator vane discharge passage 59p. Therefore, the drain in this stator vane discharge passage 59p makes it difficult for the steam in the steam passage 17 to be discharged to the outer periphery of the blade ring 30. Therefore, in this embodiment, it is possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0106] (7) The stationary vane segment VS in the seventh aspect is In the vane segment VS according to the sixth aspect, the outer shroud 57 of each of the plurality of vanes 51 has a pair of side surfaces 58a, 58b facing back to back in the circumferential direction Dc. The outer shroud 57 of the drain discharge vane 51D has a vane discharge groove 59g that is recessed from one of the pair of side surfaces 58a, 58b in the outer shroud 57 of the drain discharge vane 51D to the other side surface and extends from the drain accumulation grooves 59,34 in the outer shroud 57 of the drain discharge vane 51D to the opposite-gas path surface 58pa toward the radially outer side Dro. The vane discharge flow path 59p is defined by a plane including a surface that forms the vane discharge groove 59g.

[0107] In this embodiment, the stator vane discharge passage 59p can be easily formed in the outer shroud 57.

[0108] (8) In the eighth aspect, the stator vane segment VS is In the stator vane segment VS according to any one of the first to fifth aspects, the one member is the blade ring 30, and the other member is the outer shroud 57 for each of the plurality of stator vanes 51. The drain reservoir groove 34 is recessed from the upstream groove side surface 33u of the blade ring 30 toward the axis upstream side Dau, extends in the circumferential direction Dc, and is annular about the axis Ar.

[0109] (9) In the ninth aspect, the stator vane segment VS is In any one of the first to eighth aspects, the stator vane segment VS includes a second stator vane row 50 in addition to the first stator vane row 50 that is the stator vane row 50. The second stator vane row 50 has a plurality of second stator vanes 51 lined up in the circumferential direction Dc. Each of the plurality of second stator vanes 51 has a blade body 52 extending in the radial direction Dr and an outer shroud 57 provided on the radially outer side Dro of the blade body 52. ​​The outer shroud 57 of each of the plurality of second stator vanes 51 has a gas path surface 58p facing the radially inner side Dri, a counter-gas path surface 58pa facing the radially outer side Dro, a front surface 58f facing the axial upstream side Dau, and a rear surface 58r facing the axial downstream side Dad. The blade ring 30 has a second blade groove 32 into which at least a portion of the outer shroud 57 of each of the plurality of second stator vanes 51 is inserted. The second blade groove 32 is spaced apart in the axial direction Da from the first blade groove 32, which is the blade groove 32 into which at least a portion of the outer shroud 57 of each of the plurality of first stator vanes 51, which are the plurality of stator vanes 51 included in the first stator vane row 50, is inserted. The second blade groove 32 has a second upstream groove side surface 33u facing the axial downstream side Dad and facing the front surface 58f of each of the plurality of second stator vanes 51, a second downstream groove side surface 33d facing the axial upstream side Dau and facing the rear surface 58r of each of the plurality of second stator vanes 51, and a second groove bottom surface 33b facing the radially inward side Dri and facing the anti-gas path surface 58pa of each of the plurality of second stator vanes 51. Only one of the blade ring 30 and the outer shroud 57 of each of the plurality of second stator vanes 51 has second drain reservoir grooves 59, 34 that are recessed from a surface facing the other member in the axial direction Da from the side of the other member to the side of the one member in the axial direction Da and extend in the circumferential direction Dc. A second drain transfer gap 60 is formed between the second upstream groove side surface 33u of the blade ring 30 and the front surface 58f of the outer shroud 57 of each of the plurality of second stator vanes 51, the second drain transfer gap 60 extending in the radial direction Dr from an edge of the inner circumferential surface 31i of the blade ring 30 to the second drain reservoir grooves 59, 34.The drain discharge passage 35 communicates with the second drain retention grooves 59, 34 and is configured to be able to discharge the drain in the second drain retention grooves 59, 34 to the outer periphery of the blade ring 30. The minimum gap Gmin in the axial direction Da of the second drain transfer gap 60 is narrower than ½ of the groove depth d of the second drain retention grooves 59, 34 in the axial direction Da.

[0110] In this embodiment, the drain Dau on the axial upstream side of the first stator blade row 50 and the drain Dau on the axial upstream side of the second stator blade row 50 in the steam flow path 17 can be efficiently discharged outside the steam flow path 17.

[0111] (10) In the tenth aspect, the stator vane segment VS is In the stator vane segment VS according to the ninth aspect, the drain reservoir grooves 59,34 included in only the one of the blade ring 30 and the outer shroud 57 of each of the plurality of first stator vanes 51 included in the first stator vane row 50 form first drain reservoir grooves 59,34. The drain discharge passage 35 includes a first inner passage 37 that communicates with the first drain reservoir grooves 59,34 and extends in a direction having a component of the radial direction Dr, a second inner passage 37 that communicates with the second drain reservoir grooves 59,34 and extends in a direction having a component of the radial direction Dr, an interrow collecting passage 38 that extends in the direction having a component of the radial direction Dr and communicates with the first inner passage 37 and the second inner passage 37, and an outer discharge passage 39 that communicates with the interrow collecting passage 38 and opens at the outer circumferential surface 31o of the blade ring 30.

[0112] In this embodiment, the flow path through which the drain from the first drain grooves 59, 34 flows and the flow path through which the drain from the second drain grooves 59, 34 flows are partially integrated in the drain discharge flow path 35, thereby simplifying the drain discharge flow path 35. Furthermore, in this embodiment, the drain from the first drain grooves 59, 34 and the drain from the second drain grooves 59, 34 join together in the interrow collecting flow path 38 in the drain discharge flow path 35, increasing the drain flow rate in this interrow collecting flow path 38. Therefore, in this embodiment, the drain in this interrow collecting flow path 38 makes it difficult for steam in the steam flow path 17 to be discharged to the outer periphery of the blade ring 30. Therefore, in this embodiment, it is possible to suppress a decrease in steam turbine efficiency caused by steam that is effective for moving the rotor blades being wasted and discharged to the outer periphery of the blade ring 30.

[0113] (11) In the eleventh aspect, the stator vane segment VS is In the stator vane segment VS according to the ninth aspect, the drain reservoir grooves 59, 34 included in only one of the blade ring 30 and the outer shroud 57 of each of the plurality of first stator vanes 51 included in the first stator vane row 50 form first drain reservoir grooves 59, 34. The drain discharge passage 35 includes a first discharge passage 36 that communicates with the first drain reservoir grooves 59, 34 and opens at the outer peripheral surface 31o of the blade ring 30, and a second discharge passage 36 that communicates with the second drain reservoir grooves 59, 34 and opens at the outer peripheral surface 31o of the blade ring 30.

[0114] The steam turbines in the above-described embodiments and modifications can be understood, for example, as follows. (12) In a twelfth aspect, the steam turbine comprises: The turbine blade assembly includes a stator vane segment VS according to any one of the first to eleventh aspects, and a rotor 10 rotatable around the axis Ar on the inner circumferential side of the blade ring 30. [Explanation of symbols]

[0115] 10: Rotor 11: Rotor shaft 12: Moving blade row 15: Bearing 16: Steam inlet pipe 17: Steam flow path 20: Casing 21: Inner casing 22: Exhaust casing 22s: Exhaust space 23: Diffuser 23s: Diffuser space 27: Exhaust port 30: Wing ring 30a: First blade ring (or simply blade ring) 30b:Second wing ring 30c: Third wing ring 31i: Inner surface 31o: Outer surface 32: Wing groove 32a, 32xa: First stage blade groove 32b: Second stage blade groove 32c: Third stage blade groove (or first blade groove) 32d: Fourth stage blade groove (or second blade groove) 32e: Fifth stage wing groove 33u: Upstream ditch side 33ug: Side of drain inlet groove 33d: Downstream ditch side 33b: Groove bottom surface 34: Drain groove 35: Drain discharge flow path 36: Discharge flow path 37: Inner flow channel 37b: Second stage inner flow path 37c: Third stage inner channel 37d: Fourth stage inner channel 37e: Fifth stage inner channel 38: Inter-row collective flow path 39:Outer discharge channel 50: Stator blade row 50a: First stage stationary blade row 50b: Second stage stator blade row 50c: Third stage stator blade row (or first stator blade row) 50d: Fourth stage stator blade row (or second stator blade row) 50e: Fifth stage stator blade row 51: Static wing 51D: Drain discharge vane 52: Wing body 52f: leading edge 52r: trailing edge 52p: Positive pressure side 52n: Negative pressure side 54: Inner shroud 55p: Gas pass surface 55pa: Anti-gas pass surface 55f:Front 55r: Rear 55a: First side 55b:Second side 57: Outer shroud 58p: Gaspath surface 58pa: Anti-gas pass surface 58f:Front 58r: Rear 58a: First side 58b:Second side 59: Drain groove 59p: Stator blade exhaust passage 59g: Stator blade discharge groove 60: Drain transfer gap 61: Minimum gap 62: Drain introduction gap d: Groove depth Gmin: Minimum gap C: Condenser ST1: First steam turbine section ST2: Second steam turbine section VS: Stator vane segment Ar: Axis line Ap: tube axis Da: Axial direction Dau: Axis upstream side Dad: Downstream of the axis Dc: Circumferential direction Dc1: First side in circumferential direction Dc2: Second side in circumferential direction Dr: Radial direction Dri: Radial inner direction Dro: Radial outer side

Claims

1. a blade ring having an annular cross section perpendicular to the axis and forming a steam flow path on its inner circumferential side through which steam can flow; a stator blade row held by the blade ring; Equipped with The stator blade row has a plurality of stator blades arranged in a circumferential direction with respect to the axis, each of the plurality of stator vanes includes a blade body extending in a radial direction relative to the axis, and an outer shroud provided on the radially outer side of a radially inner side and a radially outer side of the blade body in the radial direction, the outer shroud has a gas path surface facing radially inward, a counter-gas path surface facing radially outward, a front surface facing the upstream side of the axis and a rear surface facing the downstream side of the axis, the front surface facing the upstream side of the axis and a rear surface facing the downstream side of the axis, the blade ring has an inner circumferential surface facing radially inward, an outer circumferential surface facing radially outward, blade grooves recessed from the inner circumferential surface radially outward and extending in the circumferential direction, into which at least a portion of the outer shroud for each of the plurality of stator vanes is inserted, and a drain discharge flow path, the blade groove has an upstream groove side surface facing the axial downstream side and opposing the front surface of each of the plurality of stator blades, a downstream groove side surface facing the axial upstream side and opposing the rear surface of each of the plurality of stator blades, and a groove bottom surface facing the radially inward side and opposing the anti-gas path surface of each of the plurality of stator blades, only one of the blade ring and the outer shroud for each of the plurality of stator vanes has a drain collection groove recessed from a surface facing the other member in the axial direction from a side of the other member to a side of the one member in the axial direction and extending in the circumferential direction, a drain transfer gap is formed between the upstream groove side surface of the blade ring and the front surface of the outer shroud of each of the plurality of stator vanes, the drain transfer gap extending in the radial direction from an edge of the inner circumferential surface of the blade ring to the drain accumulation groove and capable of guiding drain in the steam flow path to the drain accumulation groove; the drain discharge flow path communicates with the drain retention groove and is configured to be able to discharge the drain in the drain retention groove to the outer circumferential side of the blade ring, the minimum gap in the axial direction of the drain transfer gap is narrower than half the groove depth in the axial direction of the drain accumulation groove; Stator vane segment.

2. 2. The vane segment of claim 1, The minimum gap is 2 mm or less. Stator vane segment.

3. The vane segment according to claim 1 or 2, the drain transfer gap has a minimum gap portion and a drain introduction gap portion extending from the radially inner edge of the minimum gap portion to an edge of the inner circumferential surface of the blade ring, the axial gap at the minimum gap portion is the minimum gap, The axial gap in the drain introduction gap portion is wider than the minimum gap. Stator vane segment.

4. 4. The vane segment according to claim 3, a ratio of the radial dimension of the minimum gap portion to the minimum gap is 1 or more; Stator vane segment.

5. The vane segment according to claim 1 or 2, a distance in the axial direction between the upstream groove side surface of the blade ring and the front surface of the outer shroud for each of the plurality of stator vanes, at a position radially outward of the drain accumulation groove, is narrower than the minimum gap; Stator vane segment.

6. The vane segment according to claim 1 or 2, the one member is the outer shroud for each of the plurality of stator vanes, the other member is the blade ring, the outer shroud for each of the plurality of stator vanes has the drain collection groove, the drain retention groove is recessed from the front surface of the outer shroud for each of the plurality of stator vanes toward a downstream side of the axis and extends in the circumferential direction, the drain grooves for each of the plurality of stator blades are aligned in the circumferential direction so as to be connected to one another, At least one of the plurality of stator vanes serves as a drain discharge stator vane, the outer shroud of the drain discharge vane has a vane discharge flow passage, the stator vane discharge flow passage extends from the drain accumulation groove in the outer shroud of the drain discharge stator vane to any one of the front surface, the rear surface, and the anti-gas path surface of the outer shroud of the drain discharge stator vane, opens at the one surface, and communicates with the drain discharge flow passage of the blade ring. Stator vane segment.

7. 7. The vane segment of claim 6, The outer shroud for each of the plurality of stator vanes has a pair of side surfaces facing the circumferential direction and facing back to back, the outer shroud of the drain discharge stator vane has a stator vane discharge groove that is recessed from one side surface of the pair of side surfaces of the outer shroud of the drain discharge stator vane to the other side surface and extends radially outward from the drain accumulation groove in the outer shroud of the drain discharge stator vane to the opposite-gas path surface, the stator vane discharge passage is defined by a surface including a surface that forms the stator vane discharge groove; Stator vane segment.

8. The vane segment according to claim 1 or 2, the one member is the blade ring, the other member is the outer shroud for each of the plurality of stator vanes, the drainage groove is recessed from the upstream groove side surface of the blade ring toward the upstream side of the axis, extends in the circumferential direction, and is annular about the axis. Stator vane segment.

9. The vane segment according to claim 1 or 2, In addition to the first stator blade row, a second stator blade row is provided, the second stator blade row has a plurality of second stator blades aligned in the circumferential direction, each of the plurality of second stator vanes includes a blade body extending in the radial direction and an outer shroud provided on the radially outer side of the blade body; the outer shroud for each of the plurality of second stator vanes has a gas path surface facing radially inward, a counter-gas path surface facing radially outward, a front surface facing the axial upstream side, and a rear surface facing the axial downstream side, the blade ring has a second blade groove into which at least a portion of the outer shroud of each of the plurality of second stator vanes is inserted, the second blade groove is spaced apart in the axial direction from the first blade groove, which is the blade groove into which at least a portion of the outer shroud of each of the first stator vanes that are the plurality of stator vanes included in the first stator vane row is inserted, the second blade groove has a second upstream groove side surface facing the axial downstream side and opposing the front surface of each of the second stator vanes, a second downstream groove side surface facing the axial upstream side and opposing the rear surface of each of the second stator vanes, and a second groove bottom surface facing the radially inward side and opposing the anti-gas path surface of each of the second stator vanes, only one of the blade ring and the outer shroud for each of the plurality of second stator vanes has a second drain accumulation groove recessed from a surface facing the other member in the axial direction from a side of the other member to a side of the one member in the axial direction and extending in the circumferential direction, a second drain transfer gap is formed between the second upstream groove side surface of the blade ring and the front surface of the outer shroud of each of the plurality of second stator vanes, the second drain transfer gap extending in the radial direction from an edge of the inner circumferential surface of the blade ring to the second drain retention groove and capable of guiding drain in the steam flow path to the second drain retention groove; the drain discharge passage communicates with the second drain retention groove and is configured to be able to discharge drain in the second drain retention groove to an outer circumferential side of the blade ring, the minimum gap in the axial direction of the second drain transfer gap is narrower than half the groove depth in the axial direction of the second drain accumulation groove; Stator vane segment.

10. 10. The vane segment of claim 9, the drain reservoir groove included in only one of the blade ring and the outer shroud of each of the plurality of first stator blades in the first stator blade row forms a first drain reservoir groove, the drain discharge passage includes: a first inner passage communicating with the first drain retention groove and extending in a direction having a radial component; a second inner passage communicating with the second drain retention groove and extending in a direction having a radial component; an interrow collecting passage extending in the direction having a radial component and communicating with the first inner passage and the second inner passage; and an outer discharge passage communicating with the interrow collecting passage and opening at the outer peripheral surface of the blade ring. Stator vane segment.

11. 10. The vane segment of claim 9, the drain reservoir groove included in only one of the blade ring and the outer shroud of each of the plurality of first stator blades in the first stator blade row forms a first drain reservoir groove, the drain discharge flow path includes a first discharge flow path that communicates with the first drain retention groove and opens at an outer peripheral surface of the blade ring, and a second discharge flow path that communicates with the second drain retention groove and opens at an outer peripheral surface of the blade ring. Stator vane segment.

12. The vane segment according to claim 1 or 2; a rotor rotatable about the axis on the inner circumferential side of the blade ring; A steam turbine comprising:

Images