Steam turbine

Abstract

Steam turbine (1A, 1B, 1C), comprising: a rotor shaft (21) which rotates about an axis (O); several rotor blade rows (31) arranged at intervals in an axial direction (Da) along the axis (O), wherein the rotor blade rows (31) are attached to a section of the rotor shaft (21) located on an outside (Dro) in a radial direction (Dr); a housing (10) arranged to cover the rotor shaft (21) and the several rotor blade rows (31); and Stator blade rows (41) arranged at intervals in the axial direction (Da) and each arranged on a first side (Dau) in the axial direction (Da) with respect to the multiple rotor blade rows (31), wherein the stator blade rows (41) are attached to a section of the housing (10) located on an inside (Dri) in the radial direction (Dr), where each stator blade row (41) contains: several stator blades (42) arranged at intervals in a circumferential direction (Dc) and each extending in the radial direction (Dr), an outer ring (43, 43B, 43C) which has a ring-shaped form and which is arranged closer to the outer surface (Dro) in the radial direction (Dr) than the several stator blades (42), an inner ring (44) which has a ring-shaped form and which is arranged in the radial direction (Dr) closer to an inner side (Dri) than the several stator blades (42), a concave section (61) formed on an inner circumferential surface (43f) of the ring, which faces the inner side (Dri) in the radial direction (Dr) of the outer ring (43, 43B, 43C), and which is recessed in the radial direction (Dr) between stator blades (42) that are adjacent to each other in the circumferential direction (Dc), towards the outer side (Dro), and a discharge section (71) which is open in the concave section (61) and which discharges liquid droplets accumulated in the concave section (61) to the outside, the stator blade (42) contains: a pressure surface (42a) which is formed such that it faces one side in the circumferential direction (Dc) and which is formed such that it is curved in a concave shape, and a suction surface (42b) which is formed such that it faces the other side in the circumferential direction (Dc) and which is formed such that it is curved in a convex shape, and the concave section (61) on one side near a suction surface (42b) is formed by one of two stator blades (42) which is arranged on one side in the circumferential direction (Dc), wherein the two stator blades (42) are adjacent to each other in the circumferential direction (Dc), and wherein the steam turbine (1A, 1B, 1C) further comprises a convex section (62) projecting in the radial direction (Dr) towards the inside (Dri) and which, with respect to the concave section (61), is formed on one side near a pressure surface (42a) by one of the two stator blades (42) which is arranged on the other side in the circumferential direction (Dc), wherein the two stator blades (42) are adjacent to each other in the circumferential direction (Dc).

Description

Technical area

[0001] The present disclosure relates to a steam turbine. State of the art

[0002] A steam turbine has several rows of compression stages within a casing. Steam flowing from an upstream to a downstream side through these rows of compression stages expands as it moves downstream, causing a decrease in pressure and temperature. In particular, in some cases, the moisture content of the steam increases near the last row of compression stages, causing it to condense into liquid droplets. This increase in steam moisture reduces the efficiency of the steam turbine. Furthermore, in cases where the moisture in the steam condenses into liquid droplets, erosion can occur, where liquid droplets scattered by a stator blade corrode a last row of rotor blades.

[0003] In this regard, for example, PTL 1 discloses a configuration in which an inner circumferential surface of a membrane outer ring provided in a housing is equipped with a suction section for recovering liquid droplets (water droplets or a water film) from the inner circumferential surface of the membrane outer ring. In this configuration, the suction section communicates with a hollow section formed in the membrane outer ring from a suction side of a stator blade to a pressure side of an adjacent stator blade. According to such a configuration, liquid droplets adhering to a blade surface of a stator blade in a last row of stator blades or to an inner wall surface of the membrane outer ring are drawn in through the suction section, thus preventing the liquid droplets from reaching a tip of a rotor blade on a downstream side and making the occurrence of erosion less likely.

[0004] PTL 2 discloses a system in a steam turbine for removing water droplets from the flow path of a steam turbine, which may include a groove for collecting water droplets and a plurality of holes for moisture removal that originate in the groove. The groove may extend circumferentially around an outer side wall of the steam turbine, be positioned axially upstream and in close proximity to the leading edge of a nozzle, and may have a gradual slope at a leading edge and a steep wall at a trailing edge. The holes for moisture removal may form a channel through the outer side wall through which the water droplets collected in the groove can flow.

[0005] PTL 3 discloses that in the moisture separation device of a steam turbine, which is designed such that drain extraction holes, which are connected to the low-pressure side of a condenser and the like, are provided on the outer circumferential wall surface of a steam channel on a stationary blade and the drain is extracted in the steam channel to separate the steam and the drain from each other, wherein the outer circumferential side end part of the stationary blade is supported on the outer circumferential wall and a drain guide groove is provided between the rear of the stationary blade and the outer circumferential wall.

[0006] PTL 4 discloses means for removing moisture from steam in steam turbines. Citation listPatent literature [PTL 1] JP 2019- 35 384 A [PTL 2] US 2008 / 0 050 221 A1 [PTL 3] JP H06- 123 202 A [PTL 4] US 2 111 878 A Summary of the invention: Technical problem

[0007] However, it is always preferable to suppress the occurrence of erosion more effectively.

[0008] The present disclosure was made to solve the problems described above, and one of its tasks is to provide a steam turbine with which it is possible to suppress the occurrence of erosion more effectively. Solution to the problem

[0009] According to one aspect of the present disclosure for solving the problem described above, a steam turbine is provided according to independent claims 1 and 5. Advantageous modifications are found in dependent claims 2 to 4, 6 and 7. Advantageous effects of the invention

[0010] According to the steam turbine of the present disclosure, it is possible to suppress the occurrence of erosion more effectively. Brief description of the drawings Fig. Figure 1 is a schematic view showing a schematic configuration of a steam turbine according to an embodiment of the present disclosure. Fig. Figure 2 is a cross-sectional view showing a last row of stator blades and a last row of rotor blades of the steam turbine in a first embodiment of the present disclosure. Fig. Figure 3 is a perspective view showing a section of the last stator blade row in the first embodiment of the present disclosure. Fig. Figure 4 is a view showing the cross-sectional shape of a stator blade that forms the last row of stator blades in the first embodiment of the present disclosure. Fig. Figure 5 is a cross-sectional view showing the last row of stator blades in the first embodiment of the present disclosure, viewed in an axial direction, and is a cross-sectional view along line AA in Fig. 2, as seen along arrows. Fig. Figure 6 is a view showing an outer ring of the last stator blade row in the first embodiment of the present disclosure, viewed from an inside in a radial direction, and is a cross-sectional view along line BB in Fig. 2, seen along arrows. Fig. Figure 7 is a view showing an outer ring of a last stator blade row in a second embodiment of the present disclosure, viewed from an inside in a radial direction. Fig. Figure 8 is a cross-sectional view showing the last row of stator blades in the second embodiment of the present disclosure, viewed in an axial direction. Fig. Figure 9 is a cross-sectional view showing a last row of stator blades in a modification example of the second embodiment of the present disclosure, viewed in an axial direction. Fig. Figure 10 is a view showing an outer ring of a last stator blade row in a third embodiment of the present disclosure, viewed from an inside in a radial direction. Description of embodiments<Erste Ausführungsform> (Configuration of steam turbine)

[0011] As in Fig. As shown in Figure 1, a steam turbine 1A of the present embodiment comprises a rotor 20 which rotates about an axis O, and a housing 10.

[0012] It should be noted that, for the sake of simplicity, in the following description, a direction in which the axis O extends is simply referred to as an axial direction Da, a radial direction of a wave core section 22 (which will be described later) based on the axis O is simply referred to as a radial direction Dr, and a circumferential direction of the wave core section 22 extending around the axis O is simply referred to as a circumferential direction Dc. (Rotor configuration)

[0013] The rotor 20 contains a rotor shaft 21 and rotor blade rows 31.

[0014] The rotor shaft 21 is arranged so that it is rotatable about the axis O. The rotor shaft 21 contains the shaft core section 22 and several disk sections 23. The shaft core section 22 has a column shape about the axis O and extends in the axial direction Da. The several disk sections 23 are arranged at intervals in the axial direction Da. Each of the disk sections 23 is arranged so that it extends from the shaft core section 22 to an outer surface Dro in the radial direction Dr. (rotor blade array configuration)

[0015] The rotor blade rows 31 are attached to a section of the rotor shaft 21 located on the outer surface Dro in the radial direction Dr. The rotor blade rows 31 are attached to the outer circumferences of the disk sections 23, which are outer circumferential sections of the rotor shaft 21. Several of the rotor blade rows 31 are arranged at intervals along the axial direction Da of the rotor shaft 21. In the present embodiment, for example, four rotor blade rows 31 are arranged. Therefore, in the present embodiment, the rotor blade rows 31 are referred to as a first to fourth stage of rotor blade rows 31.

[0016] As in Fig. As shown in Figure 2, each of the rotor blade rows 31 contains several rotor blades 32 arranged in the circumferential direction Dc, a cover 34, and a platform 35. Each of the rotor blades 32 extends in the radial direction Dr. The cover 34 is arranged radially closer to the outer side Dro than the rotor blades 32. The platform 35 is arranged radially closer to an inner side Dri than the rotor blades 32. Steam S flows through an annular space between the cover 34 and the platform 35 at the rotor blades 32. (Configuration of case)

[0017] As in Fig. As shown in Figure 1, the housing 10 is designed to cover the rotor 20. Stator blade rows 41 are attached to a section of the housing 10 located on the inside Dri in the radial direction Dr. Several of the stator blade rows 41 are arranged at intervals along the axial direction Da. In the present embodiment, the number of stator blade rows 41 is four, which is equal to the number of rotor blade rows 31. The stator blade rows 41 are arranged so that they are adjacent to the multiple rotor blade rows 31, while on a first side Dau in the axial direction Da. The first side Dau in the axial direction Da is an upstream side in the direction in which the steam S flows in the housing 10. That is, the steam S flows from the first side Dau to a second side Dad in the axial direction Da inside the housing 10. (Configuration of stator blade array)

[0018] As in Fig. 2 and Fig. As shown in Figure 3, each of the stator blade rows 41 mainly contains stator blades 42, an outer ring 43, and an inner ring 44. Several of the stator blades 42 are arranged at intervals in the circumferential direction Dc. The outer ring 43 has an annular shape and is arranged in the radial direction Dr closer to the outer surface Dro than the several stator blades 42. The inner ring 44 has an annular shape and is arranged in the radial direction Dr closer to the inner surface Dri than the several stator blades 42. The steam S flows in an annular space between the outer ring 43 and the inner ring 44. (Configuration of stator blade)

[0019] An inner end 42s of each of the stator blades 42, located on the inside Dri in the radial direction Dr, is attached to the inner ring 44. An outer end 42t of each of the stator blades 42, located on the outside Dro in the radial direction Dr, is attached to the outer ring 43.

[0020] As in Fig. As shown in section 4, the stator blade 42 has a blade cross-sectional shape in a cross-sectional view, viewed in the radial direction Dr (a direction perpendicular to the paper surface of Fig. 4) over a region from an edge section 48 of the first side to an edge section 49 of the second side, wherein the edge section 48 of the first side is located on the first side Dau in the axial direction Da and the edge section 49 of the second side is located on the second side Dad in the axial direction Da. The stator blade 42 includes a pressure surface 42a facing one side Dc1 in the circumferential direction Dc, and a suction surface 42b facing the other side Dc2 in the circumferential direction Dc. The stator blade 42 is formed by a pressure side element 45 and a suction side element 46. The pressure side element 45 forms the pressure surface 42a of the stator blade 42. The pressure side element 45 is shaped such that it is curved in a concave form, such that the pressure side element 45 is recessed in the circumferential direction Dc towards the other side Dc2. The suction side element 46 forms the suction surface 42b of the stator blade 42.The suction side element 46 is formed in a convex shape such that it projects in the circumferential direction Dc towards the other side Dc2. The pressure side element 45 and the suction side element 46 are each obtained by bending a metal plate-like component into a predetermined shape. The stator blade 42 is formed by combining the pressure side element 45 and the suction side element 46 and welding them together. Accordingly, a cavity section 47 is formed within the stator blade 42, that is, between the pressure side element 45 and the suction side element 46.

[0021] As in Fig. As shown in Figure 2, for example, the edge section 49 of the second side of the stator blade 42 can contain a convex section 49a of the second side, a concave section 49b of the second side and a blade end extension section 49c.

[0022] The convex section 49a of the second side is formed on the inner side Dri in the radial direction Dr with respect to an intermediate position 42m between the outer end 42t and the inner end 42s of the stator blade 42. The convex section 49a of the second side is formed such that it is curved in a convex shape, projecting in the axial direction Da towards the second side Dad. Furthermore, in particular, the convex section 49a of the second side is formed such that it is closer in the axial direction Da to the second side Dad than to the inner end 42s and the intermediate position 42m.

[0023] For example, the intermediate position 42m can be the middle of a space between both ends of the edge section 49 of the second side of the stator blade 42 in the radial direction Dr.

[0024] The concave section 49b of the second side is formed continuously on the outer side Dro in the radial direction Dr with respect to the intermediate position 42m. The concave section 49b of the second side is formed such that it is recessed and curved in the axial direction Da towards the first side Dau. The concave section 49b of the second side is formed such that it is curved in a concave shape such that the concave section 49b of the second side is recessed in such a way that, in the axial direction Da, it is closer to the first side Dau than the intermediate position 42m and the outer end 42t.

[0025] The blade tip extension section 49c is formed continuously on the outer side Dro in the radial direction Dr with respect to the concave section 49b of the second side. The blade tip extension section 49c extends such that it projects from the concave section 49b of the second side to the second side Dad in the axial direction Da and is connected to the outer ring 43.

[0026] Accordingly, edge segment 49 on the second side has an S-shaped form when viewed in the circumferential direction Dc.

[0027] For example, the edge section 48 of the first side of the stator blade 42 can contain a concave section 48a of the first side and a convex section 48b of the first side and can be formed in an S-like shape.

[0028] For example, the edge section 49 on the second side can have an S-shaped form over a region from the outer end 42t to the inner end 42s of the stator blade 42.

[0029] The concave section 48a of the first side is formed on a section of the stator blade 42 located on the inside Dri in the radial direction Dr. The concave section 48a of the first side is formed such that it is curved in a concave shape, such that the concave section 48a of the first side is recessed in the axial direction Da towards the second side Dad.

[0030] The convex section 48b of the first side is formed continuously on the outside Dro in the radial direction Dr with respect to the concave section 48a of the first side.

[0031] The convex section 48b of the first side is formed in such a way that it is curved in a convex shape such that the convex section 48b of the first side projects in the axial direction Da towards the first side Dau.

[0032] For example, the stator blade 42 contains a communication hole 50.

[0033] In the radial direction Dr, the communication hole 50 is formed at a position that is closer to the outside Dro in the radial direction Dr than the intermediate position 42m.

[0034] The communication hole 50 is formed such that an outer surface of the pressure side element 45 of the stator blade 42 and the cavity section 47 communicate with each other.

[0035] For example, the communication hole 50 can be a slot that extends continuously in the radial direction Dr.

[0036] For example, instead of a slot, the communication hole 50 can be one or more holes through which the outer surface of the pressure side element 45 of the stator blade 42 and the cavity section 47 communicate with each other.

[0037] For example, in the radial direction Dr, the communication hole 50 can only be formed at a position that is closer to the outside Dro in the radial direction Dr than the intermediate position 42m, where the position is on the outer surface of the pressure side element 45 of the stator blade 42.

[0038] For example, the communication hole 50 can only be formed at a position that is closer to the edge section 49 of the second side than to the edge section 48 of the first side, with the position being on the outer surface of the pressure side element 45 of the stator blade 42. (Outer ring configuration)

[0039] As in Fig. 5 and Fig. As shown in Figure 6, a concave section 61, a convex section 62 and a discharge section 71 are formed on the outer ring 43.

[0040] The concave section 61 is formed on an inner circumferential surface 43f of the outer ring 43, with the inner circumferential surface 43f facing the inner side Dri in the radial direction Dr. The concave section 61 is formed between the stator blades 42 that are adjacent to each other in the circumferential direction Dc. The concave section 61 is formed on one side near the suction surface 42b of one of two stator blades 42 that are arranged on one side Dc1 in the circumferential direction Dc, with the two stator blades 42 being adjacent to each other in the circumferential direction Dc. The concave section 61 is formed in a concave shape that is recessed in the radial direction Dr towards the outer side Dro.

[0041] For example, the concave section 61 can extend in the axial direction Da.

[0042] For example, the concave section 61 can extend in a direction that extends along the inner circumferential surface 43f of the ring and along the suction surface 42b of the stator blade 42.

[0043] The convex section 62 is formed on one side near the pressure surface 42a, relative to the concave section 61, by one of two stator blades 42, which are arranged on the other side Dc2 in the circumferential direction Dc, with the two stator blades 42 being adjacent to each other in the circumferential direction Dc. The convex section 62 is formed in a convex shape that projects in the radial direction Dr towards the inner side Dri.

[0044] For example, the convex section 62 can extend in the axial direction Da.

[0045] For example, the convex section 62 can extend in a direction that extends along the inner circumferential surface 43f of the ring and along the pressure surface 42a of the stator blade 42.

[0046] The convex section 62 can, for example, be easily formed on the inner circumferential surface 43f of the outer ring 43 by welding overlay.

[0047] The discharge section 71 is formed within the concave section 61. The discharge section 71 is a slot or one or more holes open in the concave section 61. A slot or hole forming the discharge section 71 is connected to a condenser or the like, located outside the steam turbine 1A. Through the discharge section 71, liquid droplets flowing into the concave section 61, or a liquid film formed by liquid droplets (the liquid droplets or liquid film can be referred to as a drain), are discharged to the condenser on the outside. (Operation and effect)

[0048] According to the steam turbine 1A, as described above, the concave section 61, which is recessed in the radial direction Dr towards the outer side Dro, is formed on the inner circumferential surface 43f of the outer ring 43 at a position between the stator blades 42 that are adjacent to each other in the circumferential direction Dc. Accordingly, liquid droplets flowing from the first side Dau in the axial direction Da within the casing 10 and adhering to the inner circumferential surface 43f of the outer ring 43 are collected in the concave section 61, containing the liquid droplets in the steam S. The collected liquid droplets are discharged to the outside through the discharge section 71. Therefore, the amount of liquid droplets reaching the rotor blade row 31, located on the second side Dad in the axial direction Da, can be reduced. Consequently, the occurrence of erosion can be made less likely.

[0049] In steam turbine 1A, as described above, a stream of steam S in the stator blade row 41 comes into contact with the pressure surface 42a of the stator blade 42, which is positioned on the other side Dc2 in the circumferential direction Dc. Therefore, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure on one side near the pressure surface 42a of the stator blade 42, which is positioned on the other side Dc2 in the circumferential direction Dc, is high, and the pressure on one side near the suction surface 42b of the stator blade 42, which is positioned on one side Dc1 in the circumferential direction Dc, is low.In this respect, the concave section 61 is formed on the side near the suction surface 42b of the stator blade 42, which is arranged on one side Dc1 in the circumferential direction Dc, such that the size of the flow path of the steam S between the inner ring 44 and the outer ring 43 in the radial direction Dr is increased in the section where the concave section 61 is formed. That is, the cross-sectional area of ​​the flow path of the steam S between the inner ring 44 and the outer ring 43 is increased in the section where the concave section 61 is formed. As a result, the flow velocity of the steam S is reduced and the pressure of the steam S is increased in the section where the concave section 61 is formed.Accordingly, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure on one side near the suction surface 42b of the stator blade 42 that is positioned on one side Dc1 in the circumferential direction Dc is increased, and thus a pressure difference in the circumferential direction Dc between the stator blade 42 on one side Dc1 and the stator blade 42 on the other side Dc2, which are adjacent to each other in the circumferential direction Dc, is reduced. As a result, a cross-flow Fb (see . Fig. 6), which is a current of vapor S flowing in the circumferential direction Dc and is caused by a pressure difference between stator blades 42 adjacent to each other in the circumferential direction Dc, is suppressed. Therefore, the turbulence of the liquid droplets caused by the crossflow Fb is improved, and the amount of liquid droplets reaching the rotor blade row 31 on the second side Dad in the axial direction Da can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0050] The steam turbine 1A, as described above, includes the convex section 62, which is formed on the side near the pressure surface 42a of the stator blade 42, which is arranged on the other side Dc2 in the circumferential direction Dc. In the section where the convex section 62 is formed, the size of the steam flow path S between the inner ring 44 and the outer ring 43 is reduced in the radial direction Dr. That is, the cross-sectional area of ​​the steam flow path S between the inner ring 44 and the outer ring 43 is reduced in the section where the convex section 62 is formed. As a result, the flow velocity of the steam S is increased and the pressure of the steam S is reduced in the section where the convex section 62 is formed.Accordingly, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure on one side near the pressure surface 42a of the stator blade 42 positioned on the other side Dc2 in the circumferential direction Dc is reduced, and thus the pressure difference in the circumferential direction Dc between the stator blade 42 on one side Dc1 and the stator blade 42 on the other side Dc2, which are adjacent to each other in the circumferential direction Dc, is reduced (equalized). As a result, the crossflow Fb, which is a flow of the steam S flowing in the circumferential direction Dc and is caused by a pressure difference between stator blades 42 adjacent to each other in the circumferential direction Dc, can be further suppressed.Therefore, the stirring up of liquid droplets caused by the crossflow Fb is improved, and the amount of liquid droplets reaching the rotor blade row 31 on the second side Dad in the axial direction Da can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0051] In steam turbine 1A, as described above, the concave section 49b of the second side of the edge section 49 of the second side of the stator blade 42 is recessed in the axial direction Da towards the first side Dau. Therefore, a large distance S1 is created between the concave section 49b of the second side and the rotor blade 32 of a last rotor blade row 31F in the axial direction Da. Accordingly, due to the effect of a centrifugal force caused by an eddy current flowing out of the stator blade 42, liquid droplets flow from the stator blade 42 to the second side in the axial direction Da and flow in the radial direction Dr to the outside Dro via a steam stream defined by virtual lines L1 in Fig. Figure 2 shows that the amount of liquid droplets reaching a terminal section 32a of the rotor blade 32, located on the first side Dau in the axial direction Da, can be suppressed. Consequently, the occurrence of erosion can be made less likely.

[0052] Furthermore, the convex section 49a of the second side of the edge section 49 of the second side of the stator blade 42 projects towards the second side Dad in the axial direction Da. Therefore, the distance S2 between the convex section 49a of the second side and the last rotor blade row 31F can be reduced compared to the distance S1 at the concave section 49b of the second side. As a result, a decrease in turbine power can be suppressed. Since the distance S2 between the convex section 49a of the second side and the rotor blade 32 of the last rotor blade row 31F is reduced, an increase in bearing clearance and a decrease in shaft vibration reliability can also be suppressed.Since the convex section 49a of the second side is formed on the inside Dri in the radial direction Dr, the circumferential velocity of a steam flow S is small compared to the outside Dro in the radial direction Dr, and thus erosion is unlikely to occur. Consequently, the occurrence of erosion can be suppressed more effectively. The steam turbine 1A, as described above, further includes the blade tip extension section 49c, which is formed continuously on the outside Dro in the radial direction Dr with respect to the concave section 49b of the second side and extends towards the second side Dad in the axial direction Da.

[0053] Accordingly, due to the effect of a centrifugal force caused by an eddy current flowing out of the stator blade 42, liquid droplets flowing radially towards the outer surface Dro are prevented from accumulating on the concave section 49b on the second side. Therefore, the liquid droplets are easily guided from the blade tip extension section 49c to the outer ring 43. Since the liquid droplets are guided to the outer ring 43 in this way, the amount of liquid droplets reaching the end section 32a of the rotor blade 32 on the first side Dau in the axial direction Da can be more effectively suppressed.

[0054] According to the steam turbine 1A, as described above, the edge section 48 of the first side contains the concave section 48a of the first side and the convex section 48b of the first side and has an S-like shape.

[0055] Accordingly, the blade surface length of the stator blade 42 is prevented from being locally large at a time when the edge section 48 of the first side and the edge section 49 of the second side are connected in the axial direction Da, compared to a case in which the edge section 48 of the first side of the stator blade 42 is formed in a linear shape extending along the radial direction Dr. In particular, the length of a flow path from the concave section 48a of the first side to the convex section 49a of the second side and the length of a flow path from the convex section 48b of the first side to the concave section 49b of the second side along the axial direction Da are prevented from differing significantly from each other.Accordingly, it can be prevented that a friction loss generated between the liquid droplets and a surface of the stator blade 42 differs significantly in parts in the radial direction Dr.

[0056] Furthermore, in steam turbine 1A, at least some of the liquid droplets at the cavity section 47 in the stator blade 42 can be recovered through the communication hole 50. Accordingly, the amount of liquid droplets reaching the end section 32a of the rotor blade 32, located on the first side Dau in the axial direction Da, can be more effectively suppressed. Therefore, it is possible to achieve a more significant effect, effectively suppressing the occurrence of erosion while simultaneously preventing a decrease in turbine power and shaft vibration reliability.

[0057] Furthermore, in steam turbine 1A, the communication hole 50 is located closer to the outer surface Dro in the radial direction Dr than the intermediate position 42m. Therefore, the processing area of ​​the communication hole 50 can be reduced.

[0058] Furthermore, in steam turbine 1A, the communication hole 50 is located closer to the outer surface Dro in the radial direction Dr than the intermediate position 42m. Therefore, the cavity section 47 of the stator blade 42 can be made smaller relative to the position of the communication hole 50. Consequently, liquid droplets are easily discharged into the cavity section 47.

[0059] Furthermore, in steam turbine 1A, the communication hole 50 is formed only at one position, which is closer to the edge section 49 of the second side than to the edge section 48 of the first side, with the position being located on the outer surface of the pressure-side element 45 of the stator blade 42. Therefore, the edge section 49 of the second side of the stator blade 42 can have a heat-blocking structure. (Second embodiment)

[0060] Next, a second embodiment of the steam turbine according to the present disclosure is described. The steam turbine in the second embodiment differs from the steam turbine of the first embodiment only in that a first groove 63 is provided in the concave section 61. Therefore, in the description of the second embodiment, the same parts as those of the first embodiment are described with the same reference numerals, and repetitive descriptions are omitted. That is, the description of the configuration of each part of the steam turbine, which has the same configuration as that of the first embodiment, is omitted.

[0061] As in Fig. 7 and Fig. As shown in Figure 8, an outer ring 43B of a steam turbine 1B of the present embodiment includes the concave section 61, the convex section 62, the first groove 63 and the discharge section 71.

[0062] The first groove 63 is formed in the concave section 61. The first groove 63 is formed such that it extends radially from the concave section 61 towards the outer surface Dro in the radial direction Dr. The first groove 63 extends axially Da. The first groove 63 extends in such a way that it intersects the pressure surface 42a of the stator blade 42, which is positioned on the other side Dc2 in the circumferential direction Dc, and the suction surface 42b of the stator blade 42, which is positioned on one side Dc1 in the circumferential direction Dc.

[0063] For example, the first groove 63 can extend in a direction that extends along the inner circumferential surface 43f of the ring and along the pressure surface 42a of the stator blade 42.

[0064] For example, the first groove 63 can extend in a direction in which the concave section 61 extends.

[0065] The discharge section 71 is formed in the first groove 63. The discharge section 71 is a slot or a hole that is open in the first groove 63. The discharge section 71 is connected to a condenser or the like, which is located outside the steam turbine 1B. Through the discharge section 71, liquid droplets flowing from the inside of the concave section 61 into the first groove 63, or a liquid film formed by liquid droplets, are discharged to the condenser on the outside. (Operation and effect)

[0066] According to the steam turbine 1B, as described above, the occurrence of erosion, as in the first embodiment, can be suppressed more effectively.

[0067] Furthermore, in the steam turbine 1B, liquid droplets entering the concave section 61 can be efficiently recovered via the first groove 63 and discharged to the outside through the discharge section 71.

[0068] Furthermore, according to the steam turbine 1B, as described above, the first groove 63 extends in the axial direction Da. Accordingly, liquid droplets moved by the transverse flow Fb in the circumferential direction Dc along the annular inner circumferential surface 43f can be efficiently collected at the first groove 63, the transverse flow Fb being caused by a pressure difference between stator blades 42 that are adjacent to each other in the circumferential direction Dc. (Modification example of the second embodiment)

[0069] As in Fig. As shown in Figure 9, the stator blade row 41 of the steam turbine 1B, as described above, can consist of several stator blade row segments 41S into which the stator blade row 41 is subdivided in the circumferential direction Dc. Each of the stator blade row segments 41S integrally contains a ring segment 43S, which is one of several segments into which the outer ring 43 is subdivided in the circumferential direction Dc, an inner ring segment 44S, which is one of several segments into which the inner ring 44 is subdivided in the circumferential direction Dc, and the stator blade 42. The stator blade row segments 41S are bonded together by being caused to butt against each other in the circumferential direction Dc.

[0070] In such a configuration, the discharge section 71 and the first groove 63 are formed at a connection between the ring segments 43S that are adjacent to each other in the circumferential direction Dc. In this case, a notch 43k is formed on one of the ring segments 43S that is positioned on one side Dc1 in the circumferential direction Dc, and on the other ring segment 43S that is positioned on the other side Dc2 in the circumferential direction Dc. The discharge section 71 and the first groove 63 are formed when the notches 43k of the ring segments 43S abut each other in the circumferential direction Dc.

[0071] Since the discharge section 71 and the first groove 63 are formed at the connection between the ring segments 43S as described above, the discharge section 71 or the first groove 63 can be easily formed when the ring segments 43S are connected to each other at the assembly time of the stator blade row 41. (Third embodiment)

[0072] Next, a third embodiment of the steam turbine according to the present disclosure is described. The steam turbine in the third embodiment differs from the steam turbine of the second embodiment only in that a second groove 65 and a second discharge section 73 are provided. Therefore, in the description of the third embodiment, the same parts as those of the second embodiment are described with the same reference numerals, and any repetitive description is omitted. That is, the description will focus on the differences between the second and third embodiments, and the description of the same configuration as in the first and second embodiments is omitted.

[0073] As in Fig.As shown in Figure 10, an outer ring 43C of a steam turbine 1C of the present embodiment includes the concave section 61, the convex section 62, the first groove 63, the discharge section 71, the second groove 65 and the second discharge section 73.

[0074] The second groove 65 is formed on the first side Dau in the axial direction Da with respect to the several stator blades 42 that form the stator blade row 41 on the inner circumferential surface 43f of the ring. The second groove 65 extends continuously in the circumferential direction Dc. The second groove 65 is formed such that it is recessed in the radial direction Dr towards the outer surface Dro.

[0075] The second discharge section 73 is open in the second groove 65. The second discharge section 73 is a slot or a hole that is open in the second groove 65. The second discharge section 73 is connected to a condenser or the like, which is located outside the steam turbine 1C. Through the second discharge section 73, liquid droplets flowing into the second groove 65, or a liquid film formed by liquid droplets, are discharged to the condenser on the outside. (Operation and effect)

[0076] According to the steam turbine 1C, as described above, the occurrence of erosion, as in the first embodiment and the second embodiment, can be suppressed more effectively.

[0077] Furthermore, in the steam turbine 1C, liquid droplets contained in the steam S can be collected at the second groove 65 and discharged to the outside through the second discharge section 73, the second groove 65 being formed on the first side Dau in the axial direction Da with respect to the stator blades 42 of the stator blade row 41. Accordingly, it is possible to reduce the amount of liquid droplets that reach a position closer to the second side Dad than the second groove 65 in the axial direction Da. (Other embodiments)

[0078] It should be noted that the present disclosure is not limited to the embodiments described above and the design can be modified without deviating from the core of the present disclosure.

[0079] For example, in the embodiments described above, the convex section 49a of the second side and the concave section 49b of the second side of the edge section 49 of the second side are formed such that they are curved. However, their specific shapes are not limited. For example, the convex section 49a of the second side and the concave section 49b of the second side can be curved with a constant curvature, and the curvatures of the convex section 49a of the second side and the concave section 49b of the second side can differ partially from each other.

[0080] Furthermore, although edge segment 48 of the first side and edge segment 49 of the second side each have an S-like shape, the present disclosure is not limited to this. Edge segment 48 of the first side and edge segment 49 of the second side could, for example, be linear.

[0081] In addition, for example, the configuration of each part of the steam turbines 1A, 1B and 1C can be appropriately changed, in addition to the number of stages of the rotor blade rows 31 and the stator blade rows 41. <anhang>

[0082] The steam turbines 1A, 1B and 1C described in the embodiments are understood, for example, as follows.

[0083] (1) The steam turbines 1A, 1B and 1C according to a first aspect comprise: the rotor shaft 21 rotating about the axis O; the multiple rotor blade rows 31 arranged at intervals in the axial direction Da along the axis O, the rotor blade rows 31 being attached to a section of the rotor shaft 21 located on the outside Dro in the radial direction Dr; the casing 10 arranged to cover the rotor shaft 21 and the multiple rotor blade rows 31; and the stator blade rows 41 arranged at intervals in the axial direction Da and each being arranged on the first side Dau in the axial direction Da with respect to the multiple rotor blade rows 31, the stator blade rows 41 being attached to a section of the casing 10 located on the inside Dri in the radial direction Dr. The stator blade row 41 contains the several stator blades 42,the outer rings 43, 43B and 43C, which are arranged at intervals in the circumferential direction Dc and each of which extends in the radial direction Dr, have an annular shape and are arranged in the radial direction Dr closer to the outer surface Dro than the multiple stator blades 42, the inner ring 44, which has an annular shape and is arranged in the radial direction Dr closer to the inner surface Dri than the multiple stator blades 42, the concave section 61, which is formed on the inner circumferential surface 43f of the ring, which faces the inner surface Dri in the radial direction Dr of the outer rings 43, 43B and 43C, and which is recessed in the radial direction Dr between stator blades 42 that are adjacent to each other in the circumferential direction Dc towards the outer surface Dro, and the discharge section 71, which is open in the concave section 61 and through which in the concave Section 61: Accumulated liquid droplets are released to the outside.

[0084] Examples from delivery section 71 include a slot and a hole.

[0085] In the case of steam turbines 1A, 1B, and 1C, the concave section 61, which is recessed in the radial direction Dr towards the outer surface Dro, is formed on the inner circumferential surface 43f of the outer rings 43, 43B, and 43C at a position between the stator blades 42, which are adjacent to each other in the circumferential direction Dc. Accordingly, liquid droplets flowing from the first side Dau in the axial direction Da within the casing 10 and adhering to the inner circumferential surface 43f of the outer rings 43, 43B, and 43C are collected in the concave section 61, with the liquid droplets being contained in the steam S. The collected liquid droplets are discharged to the outside through the discharge section 71. Therefore, the amount of liquid droplets reaching rotor blade row 31, located on the second side Dad in the axial direction Da, can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0086] (2) The steam turbines 1A, 1B and 1C according to a second aspect are the steam turbines 1A, 1B and 1C of (1), wherein the stator blade 42 comprises the pressure surface 42a, which is formed such that it faces one side Dc1 in the circumferential direction Dc and is formed such that it is curved in a concave shape, and the suction surface 42b, which is formed such that it faces the other side Dc2 in the circumferential direction Dc and is formed such that it is curved in a convex shape, and the concave section 61 is formed on one side near the suction surface 42b by one of two stator blades 42, which is arranged on one side Dc1 in the circumferential direction Dc, the two stator blades 42 being adjacent to each other in the circumferential direction Dc.

[0087] In such a configuration, a stream of steam S in the stator blade row 41 comes into contact with the pressure surface 42a of the stator blade 42, which is positioned on the other side Dc2 in the circumferential direction Dc. Therefore, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure on one side near the pressure surface 42a of the stator blade 42, which is positioned on the other side Dc2 in the circumferential direction Dc, is high, and the pressure on one side near the suction surface 42b of the stator blade 42, which is positioned on one side Dc1 in the circumferential direction Dc, is low.In this respect, the concave section 61 is formed on the side near the suction surface 42b of the stator blade 42, which is arranged on one side Dc1 in the circumferential direction Dc, such that the size of the flow path of the steam S between the inner ring 44 and the outer rings 43, 43B and 43C in the radial direction Dr is increased in the section where the concave section 61 is formed. That is, the cross-sectional area of ​​the flow path of the steam S between the inner ring 44 and the outer rings 43, 43B and 43C is increased in the section where the concave section 61 is formed. As a result, the flow velocity of the steam S is reduced and the pressure of the steam S is increased in the section where the concave section 61 is formed.Accordingly, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure is increased on one side near the suction surface 42b of the stator blade 42 that is positioned on one side Dc1 in the circumferential direction Dc, and thus the pressure difference in the circumferential direction Dc between the stator blade 42 on one side Dc1 and the stator blade 42 on the other side Dc2, which are adjacent to each other in the circumferential direction Dc, is reduced. As a result, the crossflow Fb, which is a flow of the steam S flowing in the circumferential direction Dc and is caused by a pressure difference between stator blades 42 that are adjacent to each other in the circumferential direction Dc, can be further suppressed.Therefore, the stirring up of liquid droplets caused by the crossflow Fb is improved, and the amount of liquid droplets reaching the rotor blade row 31 on the second side Dad in the axial direction Da can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0088] (3) The steam turbines 1A, 1B and 1C according to a third aspect are the steam turbines 1A, 1B and 1C of (1) or (2), which further comprise the convex section 62, which projects radially Dr towards the inside Dri and which, with respect to the concave section 61, is formed on one side near the pressure surface 42a by one of the two stator blades 42, which is arranged on the other side Dc2 in the circumferential direction Dc, wherein the two stator blades 42 are adjacent to each other in the circumferential direction Dc.

[0089] According to this configuration, the size of the steam flow path S between the inner ring 44 and the outer rings 43, 43B, and 43C is reduced in the radial direction Dr at the section where the convex section 62 is formed, specifically when the convex section 62 is located on the side near the pressure surface 42a of the stator blade 42, which is arranged on the other side Dc2 in the circumferential direction Dc. That is, the cross-sectional area of ​​the steam flow path S between the inner ring 44 and the outer rings 43, 43B, and 43C is reduced at the section where the convex section 62 is formed. Consequently, the flow velocity of the steam S is increased, and the pressure of the steam S is reduced at the section where the convex section 62 is formed.Accordingly, between two stator blades 42 that are adjacent to each other in the circumferential direction Dc, the pressure on one side near the pressure surface 42a of the stator blade 42 positioned on the other side Dc2 in the circumferential direction Dc is reduced, and thus the pressure difference in the circumferential direction Dc between the stator blade 42 on one side Dc1 and the stator blade 42 on the other side Dc2, which are adjacent to each other in the circumferential direction Dc, is reduced. As a result, the crossflow Fb, which is a flow of the steam S flowing in the circumferential direction Dc and is caused by a pressure difference between stator blades 42 adjacent to each other in the circumferential direction Dc, can be further suppressed.Therefore, the stirring up of liquid droplets caused by the crossflow Fb is improved, and the amount of liquid droplets reaching the rotor blade row 31 on the second side Dad in the axial direction Da can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0090] (4) The steam turbines 1B and 1C according to a fourth aspect are the steam turbines 1B and 1C of one of (1) to (3), wherein the first groove 63, which is recessed in the radial direction Dr towards the outside Dro, is formed in the concave section 61 and the discharge section 71 is open in the first groove 63.

[0091] Accordingly, liquid droplets entering the concave section 61 can be efficiently recovered via the first groove 63 and discharged to the outside through the discharge section 71.

[0092] (5) The steam turbines 1B and 1C according to a fifth aspect are the steam turbines 1B and 1C of (4), wherein the first slot 63 extends in the axial direction Da.

[0093] Accordingly, liquid droplets moved by the transverse flow Fb in the circumferential direction Dc along the inner circumferential surface of the ring 43f can be efficiently collected at the first groove 63, the transverse flow Fb being caused by a pressure difference between stator blades 42 that are adjacent to each other in the circumferential direction Dc.

[0094] (6) The steam turbine 1B according to a sixth aspect is the steam turbine 1B of (4) or (5), wherein the outer ring 43C consists of the several ring segments 43S into which the outer ring 43C is divided in the circumferential direction Dc, and the first groove 63 is formed at a connection between the ring segments 43S which are adjacent to each other in the circumferential direction Dc.

[0095] Since the first groove 63 is formed at the connection between the ring segments 43S as described above, the first groove 63 can be easily formed when the ring segments 43S are connected to each other at the time of assembly of the stator blade row 41.

[0096] (7) The steam turbine 1C according to a seventh aspect is the steam turbine 1C of one of (1) to (6), which further comprises the second groove 65, which is formed on the first side Dau in the axial direction Da with respect to the stator blade 42 on the annular inner circumferential surface 43f and which is recessed in the radial direction Dr towards the outside Dro, and the second discharge section 73, which is open in the second groove 65 and is discharged to the outside by the liquid droplets that enter the second groove 65.

[0097] Accordingly, liquid droplets contained in the vapor S can be collected at the second groove 65 and discharged to the outside through the second discharge section 73, the second groove 65 being formed on the first side Dau in the axial direction Da with respect to the stator blades 42 of the stator blade row 41. This makes it possible to reduce the amount of liquid droplets that reach a position closer to the second side Dad than the second groove 65 in the axial direction Da.

[0098] (8) The steam turbines 1A, 1B and 1C according to an eighth aspect are the steam turbines 1A, 1B and 1C of a from (1) to (7), wherein on a last stator blade row 41F, which is arranged such that it is closest to the second side Dad in the axial direction Da among the several stator blade rows 41, the edge section 49 of the second side of the stator blade 42, which is located on the second side Dad in the axial direction Da, has an S-like shape, which forms the convex section 49a of the second side, which is on the inside Dri in the radial direction Dr with respect to the intermediate position 42m between the outer end 42t of the stator blade 42 on the outside Dro in the radial direction Dr and the inner end 42s of the stator blade 42 on the inside Dri in the radial direction Dr, and which projects while in the axial direction Da to the second The side Dad is curved towards, and the concave section 49b of the second side,which is formed on the outside Dro in the radial direction Dr with respect to the intermediate position 42m and which is recessed, while in the axial direction Da it is curved towards the first side Dau.

[0099] Accordingly, the concave section 49b of the second side of the edge section 49 of the second side of the stator blade 42 is recessed in the axial direction Da towards the first side Dau. Therefore, a distance S1 between the concave section 49b of the second side and the rotor blade 32 of a last rotor blade row 31F is increased in the axial direction Da. Consequently, due to the effect of a centrifugal force caused by an eddy current flowing out of the stator blade 42, liquid droplets flow from the stator blade 42 to the second side in the axial direction Da and flow in the radial direction Dr to the outer surface Dro via a vapor stream. Therefore, the amount of liquid droplets reaching an end section 32a of the rotor blade 32, located on the first side Dau in the axial direction Da, can be suppressed. As a result, the occurrence of erosion can be made less likely.

[0100] Furthermore, the convex section 49a of the second side of the edge section 49 of the second side of the stator blade 42 projects towards the second side Dad in the axial direction Da. Therefore, the distance S2 between the convex section 49a of the second side and the rotor blades 32 of the last row can be reduced compared to the distance S1 at the concave section 49b of the second side. As a result, a decrease in turbine power can be suppressed. In addition, an increase in bearing clearance and a decrease in shaft vibration reliability can be suppressed. Industrial applicability

[0101] According to the steam turbine described above, the occurrence of erosion can be suppressed more effectively. Reference symbol list 1A, 1B, 1C Steam turbine 10 housings 20 Rotor 21 Rotor shaft 22 Wave core section 23 disc sections 31 rotor blade rows 31F last rotor blade row 32 Rotor blade 32a End section 34 Cover 35 platform 41 Stator blade row 41F last stator blade row 41S Stator blade row segment 42 Stator blade 42a Printing area 42b Suction surface 42m intermediate position 42s inner end 42t outer end 43, 43B, 43C Outer ring 43S Ring Segment 43f Ring inner circumferential surface 43k notch 44 inner ring 44S inner ring segment 45 Print page element 46 Suction side element 47 Cavity section 48 Edge section from first side 48a concave section from first side 48b convex section from first side 49 Edge section from second side 49a convex section of second side 49b concave section of second side 49c Blade tip extension section 50 communication gaps 61 concave section 62 convex section 63 first groove 65 second groove 71 Submission section 73 second submission section Since axial direction Dad's second side First page DC circumferential direction DC1 one side DC2 the other side Dr. Radial direction Three inside Dro outer Fb crossflow L1 virtual line O axis S steam< / anhang>

Claims

[1] Steam turbine (1A, 1B, 1C), comprising: a rotor shaft (21) rotating about an axis (O); a plurality of rotor blade rows (31) arranged at intervals in an axial direction (Da) along the axis (O), the rotor blade rows (31) being fixed to a portion of the rotor shaft (21) located on an outer side (Dro) in a radial direction (Dr); a housing (10) arranged to cover the rotor shaft (21) and the plurality of rotor blade rows (31); and Stator blade rows (41) arranged at intervals in the axial direction (Da) and each arranged on a first side (Dau) in the axial direction (Da) with respect to the plurality of rotor blade rows (31), wherein the stator blade rows (41) are attached to a portion of the housing (10) located on an inner side (Dri) in the radial direction (Dr), wherein each stator blade row (41) contains: a plurality of stator blades (42) arranged at intervals in a circumferential direction (Dc) and each extending in the radial direction (Dr), an outer ring (43, 43B, 43C) which has an annular shape and which is arranged closer to the outer side (Dro) in the radial direction (Dr) than the plurality of stator blades (42), an inner ring (44) having an annular shape and arranged closer to an inner side (Dri) in the radial direction (Dr) than the plurality of stator blades (42), a concave portion (61) formed on a ring inner peripheral surface (43f) facing the inner side (Dri) in the radial direction (Dr) in the outer ring (43, 43B, 43C) and recessed in the radial direction (Dr) between stator blades (42) adjacent to each other in the circumferential direction (Dc) toward the outer side (Dro), and a discharge section (71) which is open in the concave section (61) and which discharges liquid droplets accumulated in the concave section (61) to the outside, wherein the stator blade (42) contains: a pressure surface (42a) formed to face one side in the circumferential direction (Dc) and formed to be curved in a concave shape, and a suction surface (42b) formed to face the other side in the circumferential direction (Dc) and formed to be curved in a convex shape, and the concave portion (61) is formed on a side near a suction surface (42b) of one of two stator blades (42) arranged on one side in the circumferential direction (Dc), the two stator blades (42) being adjacent to each other in the circumferential direction (Dc), and wherein the steam turbine (1A, 1B, 1C) further comprises a convex portion (62) which projects in the radial direction (Dr) toward the inner side (Dri) and which, with respect to the concave portion (61), is formed on one side near a thrust surface (42a) of one of the two stator blades (42) which is arranged on the other side in the circumferential direction (Dc), the two stator blades (42) being adjacent to each other in the circumferential direction (Dc). [2] Steam turbine (1A, 1B, 1C) according to claim 1, wherein a first groove (63) recessed in the radial direction (Dr) towards the outside (Dro) is formed in the concave portion (61), and the discharge section (71) is open in the first groove (63). [3] Steam turbine (1A, 1B, 1C) according to claim 2, wherein the first groove (63) extends in the axial direction (Da). [4] Steam turbine (1A, 1B, 1C) according to claim 2 or 3, wherein the outer ring (43, 43B, 43C) consists of a plurality of ring segments (43S) into which the outer ring (43, 43B, 43C) is divided in the circumferential direction (Dc), and the first groove (63) is formed at a connection between the ring segments (43S) which are adjacent to each other in the circumferential direction (Dc). [5] Steam turbine (1A, 1B, 1C), comprising: a rotor shaft (21) rotating about an axis (O); a plurality of rotor blade rows (31) arranged at intervals in an axial direction (Da) along the axis (O), the rotor blade rows (31) being fixed to a portion of the rotor shaft (21) located on an outer side (Dro) in a radial direction (Dr); a housing (10) arranged to cover the rotor shaft (21) and the plurality of rotor blade rows (31); and Stator blade rows (41) arranged at intervals in the axial direction (Da) and each arranged on a first side (Dau) in the axial direction (Da) with respect to the plurality of rotor blade rows (31), wherein the stator blade rows (41) are attached to a portion of the housing (10) located on an inner side (Dri) in the radial direction (Dr), wherein each stator blade row (41) contains: a plurality of stator blades (42) arranged at intervals in a circumferential direction (Dc) and each extending in the radial direction (Dr), an outer ring (43, 43B, 43C) which has an annular shape and which is arranged closer to the outer side (Dro) in the radial direction (Dr) than the plurality of stator blades (42), an inner ring (44) having an annular shape and arranged closer to an inner side (Dri) in the radial direction (Dr) than the plurality of stator blades (42), a concave portion (61) formed on a ring inner peripheral surface (43f) facing the inner side (Dri) in the radial direction (Dr) in the outer ring (43, 43B, 43C) and recessed in the radial direction (Dr) between stator blades (42) adjacent to each other in the circumferential direction (Dc) toward the outer side (Dro), and a discharge section (71) which is open in the concave section (61) and which discharges liquid droplets accumulated in the concave section (61) to the outside, wherein a first groove (63) recessed in the radial direction (Dr) towards the outside (Dro) is formed in the concave portion (61), wherein the discharge section (71) is open in the first groove (63), wherein the outer ring (43, 43B, 43C) consists of a plurality of ring segments (43S) into which the outer ring (43, 43B, 43C) is divided in the circumferential direction (Dc), and wherein the first groove (63) is formed at a joint between the ring segments (43S) which are adjacent to each other in the circumferential direction (Dc). [6] Steam turbine (1A, 1B, 1C) according to one of claims 1 to 5, further comprising: a second groove (65) formed on the first side (Dau) in the axial direction (Da) with respect to the stator blade (42) on the ring inner peripheral surface (43f) and recessed in the radial direction (Dr) toward the outer side (Dro); and a second discharge portion (73) open in the second groove (65) and discharging liquid droplets entering the second groove (65) to the outside. [7] Steam turbine (1A, 1B, 1C) according to one of claims 1 to 6, wherein, at a last stator blade row (41F) arranged to be closest to a second side (Dad) in the axial direction (Da) among the plurality of stator blade rows (41), a second-side edge portion (49) of the stator blade (42) located on the second side (Dad) in the axial direction (Da) has an S-like shape including a second-side convex portion (49a) formed on the inner side (Dri) in the radial direction (Dr) with respect to an intermediate position (42m) between an outer end (42t) of the stator blade (42) on the outer side (Dro) in the radial direction (Dr) and an inner end (42s) of the stator blade (42) on the inner side (Dri) in the radial direction (Dr), and which protrudes, while being curved in the axial direction (Da) towards the second side (Dad), and a concave portion (49b) of the second side (Dad),which is formed on the outer side (Dro) in the radial direction (Dr) with respect to the intermediate position (42m) and which is recessed while being curved in the axial direction (Da) towards the first side (Dau).

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