Steam turbine and method for assembling steam turbine

Abstract

A steam turbine according to one embodiment comprises: an inner casing; a first annular portion which is connected to the inner casing or is formed integrally with the inner casing, defines at least a portion of a steam inlet flow passage, and holds a first sealing device disposed on an outer peripheral surface of a rotor; a plurality of first stage stationary blades which are arranged at intervals in the circumferential direction of the rotor and which include an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring which is connected to the inner casing or is formed integrally with the inner casing and which holds at least the plurality of first stage stationary blades; a second annular portion which is attached to the inner shrouds of the plurality of first stage stationary blades; and a second sealing device which is provided between the first annular portion and the second annular portion.

Description

Steam turbine and method of assembling the steam turbine

[0001] This application claims priority to Japanese Patent Application No. 2023-126005, filed with the Japan Patent Office on August 2, 2023, the contents of which are incorporated herein by reference.

[0002] The steam turbine has a plurality of stator vanes arranged at intervals in the circumferential direction, each of which includes an airfoil, an outer shroud disposed radially outward of the rotor than the airfoil, and an inner shroud disposed radially inward of the rotor than the airfoil (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-152119

[0004] In the vane described in the above-mentioned patent document, the radially inner side of the inner shroud has a free-support structure, but because the pressure difference and temperature across the vane increase with the increase in temperature and pressure at the steam inlet, it is desirable to connect the inner shrouds of adjacent vanes in the circumferential direction to ensure strength, particularly for vanes near the first stage. In the vane described in the above-mentioned patent document, a ring engagement groove is provided on the radially inner side of the inner shroud of the vane, and an engagement protrusion of a seal ring extending circumferentially is fitted into this ring engagement groove. However, because there is a gap between the ring engagement groove and the engagement protrusion, it is not possible to connect the inner shrouds with the seal ring to ensure strength.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to improve the strength of a stator blade in a steam turbine.

[0006] (1) A steam turbine according to at least one embodiment of the present disclosure includes: an inner casing; a first annular portion coupled to the inner casing or formed integrally with the inner casing, defining at least a portion of a steam inlet flow passage, and holding a first sealing device arranged on an outer peripheral surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring coupled to the inner casing or formed integrally with the inner casing, holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second sealing device provided between the first annular portion and the second annular portion.

[0007] (2) A method for assembling a steam turbine according to at least one embodiment of the present disclosure is a method for assembling a steam turbine, the steam turbine comprising: an inner casing; a first annular portion formed integrally with the inner casing, defining at least a part of a steam inlet flow path, and holding a first sealing device arranged on an outer circumferential surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring separable from the inner casing and holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second sealing device provided between the first annular portion and the second annular portion, after the first step is performed, a second step of attaching the rotor to the first lower half and the second lower half; after the second step is performed, a third step of attaching a second upper half of the blade ring, having at least the plurality of first-stage stator vanes attached to the second lower half and the second annular portion attached to the inner shroud, to the second lower half; and after the third step is performed, a fourth step of attaching a first upper half of the inner casing, molded integrally with the first annular portion, to the first lower half.

[0008] (3) A method for assembling a steam turbine according to at least one embodiment of the present disclosure is a method for assembling a steam turbine, the steam turbine comprising: an inner casing; a first annular portion formed integrally with the inner casing, defining at least a part of a steam inlet flow path, and holding a first sealing device arranged on an outer peripheral surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring formed integrally with the inner casing and holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second sealing device provided between the first annular portion and the second annular portion, the method comprising: a first step of attaching the rotor to the blade ring, to which at least the plurality of first stage stator vanes are attached and to which the second annular portion is attached to the inner shroud, and to a lower half of the inner casing molded integrally with the first annular portion; and a second step of attaching, to the lower half portion after carrying out the first step, the blade ring having at least the plurality of first-stage stator vanes attached thereto and the second annular portion attached to the inner shroud, and an upper half portion of the inner casing molded integrally with the first annular portion.

[0009] (4) A method for assembling a steam turbine according to at least one embodiment of the present disclosure is a method for assembling a steam turbine, the steam turbine comprising: an inner casing; a first annular portion separable from the inner casing, defining at least a part of a steam inlet flow path, and holding a first sealing device disposed on an outer circumferential surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring separable from the inner casing and holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second sealing device provided between the first annular portion and the second annular portion, a second step of attaching a third lower half of the first annular portion to the first lower half and the second lower half after the first step is performed; a third step of attaching the rotor to the first lower half, the second lower half, and the third lower half after the second step is performed; a fourth step of attaching the third upper half of the first annular portion to the third lower half after the third step is performed; a fifth step of attaching a second upper half of the blade ring, to the second lower half after the fourth step is performed, the blade ring having at least the plurality of first stage stator vanes attached thereto and the second annular portion attached to the inner shroud; and a sixth step of attaching a first upper half of the inner casing to the first lower half after the fifth step is performed.

[0010] According to at least one embodiment of the present disclosure, the strength of a stator blade in a steam turbine can be improved.

[0011] 1 is a system schematic diagram of a steam turbine facility including a steam turbine according to some embodiments. FIG. 2 is a cross-sectional view showing an outline of the structure of a steam turbine including an annulus, in a steam turbine according to some embodiments of the present disclosure, where the high-pressure turbine has an annulus. FIG. 3 is a cross-sectional view showing an outline of part A in FIG. 2. FIG. 4 is a cross-sectional view showing an outline of the structure of a portion of a high-pressure turbine in which a first annulus, a blade ring, and an inner casing are separate components. FIG. 5 is a cross-sectional view showing an outline of the structure of a portion of a high-pressure turbine according to another example. FIG. 6 is a cross-sectional view showing an outline of the structure of a portion of a high-pressure turbine according to yet another example. FIG. 7 is a cross-sectional view showing an outline of the structure of a portion of the high-pressure turbine shown in FIG. 2. FIG. 8 is a schematic enlarged view of the vicinity of first-stage stator vanes according to some embodiments, showing another example of the second annulus. FIG. 9 is a schematic enlarged view of the vicinity of first-stage stator vanes according to some embodiments, showing yet another example of the second annulus. FIG. 10 is a flowchart showing an assembly procedure for a high-pressure turbine including an annulus and a forward stage blade ring that is a component different from the annulus shown in FIG. 2. 5 is a flowchart showing an assembly procedure for the high-pressure turbine shown in FIG. 4 in which the first annular portion, the blade ring, and the inner casing are each separate members.

[0012] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are merely illustrative examples. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0013] 1 is a system schematic diagram of a steam turbine facility including a steam turbine according to some embodiments. The steam turbine facility 1 has, as main components, a boiler 2, a high-pressure turbine 4, an intermediate-pressure turbine 8, a low-pressure turbine 10, a compost helical steam generator 11, and a generator 12. The high-pressure turbine 4, the intermediate-pressure turbine 8, and the low-pressure turbine 10 are connected by a rotor 13, and the rotor 13 is connected to the generator 12.

[0014] Main steam generated in the boiler 2 flows down the main steam pipe 3 and is led to the inlet of the high-pressure turbine 4. Exhaust steam discharged after driving the high-pressure turbine 4 flows down the low-temperature reheat pipe 5 from the high-pressure turbine 4 and is led to the reheater 6 of the boiler 2, where it is reheated. The steam heated in the reheater 6 flows down the high-temperature reheat pipe 7 and is led to the intermediate-pressure turbine 8, driving the intermediate-pressure turbine 8, and then flows down the main steam pipe 9 and is led to the low-pressure turbine 10. Exhaust steam discharged after driving the low-pressure turbine 10 is led to the condenser 11, where it is cooled and condensed, and then reintroduced to the boiler 2 as feedwater. As described above, the high-pressure turbine 4, intermediate-pressure turbine 8, and low-pressure turbine 10 are connected by the rotor 13, and rotational power is transmitted to the generator 12 via the rotor 13, where it is converted into electric power by the generator 12.

[0015] A main steam stop valve 14 and a main steam control valve 15 are provided in the main steam pipe 3, through which main steam flows from the boiler 2 to the high-pressure turbine 4, from upstream to downstream in the steam flow direction. In addition, a bypass pipe 16 is provided branching off from the main steam pipe 3 between the main steam stop valve 14 and the main steam control valve 15. The bypass pipe 16 branching off from the main steam pipe 3 is connected to an intermediate stage of the high-pressure turbine 4, so that a portion of the main steam flowing through the main steam pipe 3 bypasses a portion of the upstream stage of the high-pressure turbine 4 and is introduced from the intermediate stage into the high-pressure turbine 4. An overload valve 17 is provided in the bypass pipe 16, and the amount of bypass steam flowing through the bypass pipe 16 is controlled.

[0016] Figure 2 is a cross-sectional view showing an outline of the structure of a steam turbine 20 according to some embodiments of the present disclosure, in which the high-pressure turbine 4 described below has an annular body 43. The steam turbine 20 according to some embodiments is a center-to-high integrated steam turbine in which the high-pressure turbine 4 and the intermediate-pressure turbine 8 are integrally configured. Note that Figure 2 mainly shows the structure of the high-pressure turbine 4 of the integrated high-pressure turbine 4 and intermediate-pressure turbine 8. The high-pressure turbine 4 shown in Figure 2 includes an outer casing 41, an annular body 43, and a forward stage blade ring 45.

[0017] 2, the outer casing 41 is horizontally divided into an upper half 41U and a lower half 41L. In the following description, when there is no need to distinguish between the upper half 41U and the lower half 41L, they may be simply referred to as the outer casing 41.

[0018] The high-pressure turbine 4 shown in Fig. 2 has a plurality of turbine stages provided in the axial direction on the inner peripheral side of the outer casing 41, and a main steam flow path 21 through which main steam flows is formed. Each turbine stage is composed of a plurality of moving blades 18 fixed in the circumferential direction of the rotor 13, and stator vanes 19 fixed to an annular body 43 or a front stage blade ring 45, which will be described in detail later, so as to face the upstream side of the moving blades 18. In the following description, within the axial direction of the rotor 13 in the high-pressure turbine 4, the upstream side of the flow of main steam flowing in the main steam flow path 21 will also be referred to as the axial upstream side, and the downstream side of the flow of main steam flowing in the main steam flow path 21 will also be referred to as the axial downstream side. Furthermore, the circumferential direction of the rotor 13 will also be simply referred to as the circumferential direction, and the radial direction of the rotor 13 will also be simply referred to as the radial direction.

[0019] 2 has a plurality of turbine stages arranged in the axial direction on the inner peripheral side of the outer casing 41, and a main steam flow path 81 through which main steam flows is formed. Each turbine stage is composed of a plurality of rotor blades 83 fixed in the circumferential direction of the rotor 13, and stator blades 85 fixed to a blade ring 87 so as to face the upstream side of the rotor blades 83.

[0020] The steam turbine 20 according to some embodiments is provided with a plurality of nozzles. These nozzles include, for example, a first inlet nozzle 91 for supplying main steam Sin from the main steam pipe 3 to the high-pressure turbine 4, an outlet nozzle 94 for discharging exhaust steam Sout discharged by driving the high-pressure turbine 4 to the low-temperature reheat pipe 5, a third inlet nozzle 95 for supplying reheat steam Sr from the high-temperature reheat pipe 7 to the intermediate-pressure turbine 8, and the like.

[0021] (Annular body 43) In the high-pressure turbine 4 shown in Figure 2, the annular body 43 is a single member provided radially inside the outer casing 41, and includes a first annular portion 431, a rear stage stator vane holding region 433, and an inner casing region 435. In the high-pressure turbine 4 shown in Figure 2, the first annular portion 431 is provided between the high-pressure turbine 4 and the intermediate-pressure turbine 8, which are integrally provided. In the high-pressure turbine 4 shown in Figure 2, the first annular portion 431 includes an area where a sealing device 51 is disposed, which seals the gap between the outer peripheral surface 13a of the rotor 13 and the annular body 43. The sealing device 51 is, for example, a labyrinth seal having sealing fins. The first annular portion 431 in the high-pressure turbine 4 shown in Figure 2 is an area corresponding to a member called a dummy ring in a conventional steam turbine. The first annular portion 431 in the high-pressure turbine 4 shown in Figure 2 has an extension portion 440 that extends axially downstream of the area where the sealing device 51 is arranged, along the outer peripheral surface 13a of the rotor, radially inward of a first cavity 71 described later, and toward the axial downstream side.

[0022] In the high-pressure turbine 4 shown in Fig. 2, the rear stage stator vane holding region 433 is a region that holds the stator vanes 19 of the rear stage. The rear stage stator vane holding region 433 in the high-pressure turbine 4 shown in Fig. 2 is a region that corresponds to a member called a blade ring in a conventional steam turbine. The rear stage stator vane holding region 433 in the high-pressure turbine 4 shown in Fig. 2 is a region that corresponds to a blade ring that holds the stator vanes 19 of a stage downstream of a forward stage blade ring 45 described later, that is, a region that corresponds to a blade ring that is a rear stage blade ring relative to the forward stage blade ring 45.

[0023] In the high-pressure turbine 4 shown in Fig. 2, the inner casing region 435 is a region connecting the first annular portion 431 and the rear stage stator vane holding region 433. The inner casing region 435 in the high-pressure turbine 4 shown in Fig. 2 is a region corresponding to a member called an inner casing in a conventional steam turbine. That is, in the high-pressure turbine 4 shown in Fig. 2, the annular body 43 corresponds to a dummy ring, a rear stage blade ring, and an inner casing formed into a single member in a conventional steam turbine.

[0024] A recess 437 is provided in the inner peripheral portion 43i of the annular body 43 between the first annular portion 431 and the rear stage stator blade holding region 433. A front stage blade ring 45, which will be described in detail below, is arranged in the recess 437.

[0025] The recess 437 forms a first cavity 71, which will be described later. The first cavity 71 is connected to the first inlet nozzle 91.

[0026] 2, the annular body 43 is divided in a horizontal plane into an upper half 43U and a lower half 43L. In the following description, when there is no need to distinguish between the upper half 43U and the lower half 43L, they may be simply referred to as the annular body 43.

[0027] (Forward stage blade ring 45) Figure 3 is a cross-sectional view showing an outline of part A in Figure 2. In the high-pressure turbine 4 shown in Figure 2, the forward stage blade ring 45 is a member separate from the annular body 43, and is a blade ring attached to the annular body 43 to hold the stator vanes 19 of the forward stage. The forward stage blade ring 45 extends in the axial direction.

[0028] The forward stage blade ring 45 holds a plurality of stages of stator vanes 19, including a first stage stator vane 19A which is the stator vane 19 of the most upstream stage.

[0029] 2, the forward stage blade ring 45 is divided in the horizontal plane into a forward stage blade ring upper half 45U and a forward stage blade ring lower half 45L. In the following description, when there is no need to distinguish between the forward stage blade ring upper half 45U and the forward stage blade ring lower half 45L, they may be simply referred to as the forward stage blade ring 45.

[0030] (First cavity 71) In the high-pressure turbine 4 shown in Fig. 2 , the first cavity 71 is a cavity to which main steam Sin is supplied from the main steam pipe 3. The first cavity 71 is formed by the inner circumferential portion 43i of the annular body 43, the first annular portion 431, and the forward stage blade ring 45. Note that in the high-pressure turbine 4 having a second annular portion 200 shown in Figs. 5A and 5C described later, the first cavity 71 is formed by the inner circumferential portion 43i of the annular body 43, the first annular portion 431, the forward stage blade ring 45, and the second annular portion 200. Specifically, the first cavity 71 is defined by the back surface 451b of the forward stage blade ring 45, regions radially outward and axially upstream of the first cavity 71 on the inner circumferential surface 437i of the recessed portion 437 of the annular body 43, and a radially outer surface 442 described later of the extension portion 440. 5A and 5C , a flow passage forming region 205 (described later) of the second annular portion 200 (described later) of the second annular portion 200 (described later) of the first cavity 71 is defined as a part of the first cavity 71. The main steam Sin supplied to the first cavity 71 flows from the first cavity 71 toward the first stage stator blade 19A, which is the stator blade 19 of the most upstream stage, and flows into the main steam flow passage 21. That is, the first cavity 71 is a steam inlet flow passage 75 of the high-pressure turbine 4.

[0031] 4A is a cross-sectional view showing the outline of the structure of a part of a high-pressure turbine 4A in which a first annular portion 431A, a blade ring 433A, and an inner casing 435A are each separate components. The first annular portion 431A is a component known as a dummy ring in conventional steam turbines. The first annular portion 431A corresponds to the first annular portion 431 in the high-pressure turbine 4 shown in FIG. 2 described above, and has an extension portion 440 similar to the first annular portion 431.

[0032] In the high-pressure turbine 4A shown in FIG. 4A , the first annular portion 431A is divided in a horizontal plane into a first annular portion upper half 431AU and a first annular portion lower half (not shown) that is paired with the first annular portion upper half 431AU. In the following description, when it is not necessary to distinguish between the first annular portion upper half 431AU and the first annular portion lower half, they may be simply referred to as the first annular portion 431A. Similarly, the blade ring 433A is divided in a horizontal plane into a blade ring upper half 433AU and a blade ring lower half (not shown). In the following description, when it is not necessary to distinguish between the blade ring upper half 433AU and the blade ring lower half, they may be simply referred to as the blade ring 433A. The inner casing 435A is divided in a horizontal plane into an inner casing upper half 435AU and an inner casing lower half (not shown). In the following description, when there is no need to distinguish between the upper half 435AU and the lower half of the inner casing, they may be simply referred to as the inner casing 435A.

[0033] The steam turbine 20 according to some embodiments may include a high-pressure turbine 4A having the structure shown in Fig. 4A. That is, in the high-pressure turbine 4A, the first annular portion 431A, the blade ring 433A, and the inner casing 435A may each be separate components.

[0034] In the high-pressure turbine 4A, a relatively large thrust force acts on the first annular portion 431A, tending to move the first annular portion 431A axially upstream, due to the pressure of the main steam supplied to the high-pressure turbine 4A. Therefore, in order to ensure the strength of the fitting portion 431Aa of the first annular portion 431A that fits with the inner casing 435A, the size of the first annular portion 431A becomes relatively large. As a result, the size of the turbine, including the inner casing 435A and the outer casing 435A, becomes large.

[0035] In the high-pressure turbine 4 shown in Figure 2, as described above, the first annular portion 431, the rear stage stator vane holding region 433, and the inner casing region 435 are formed in the annular body 43, which is a single member. Therefore, unlike the conventional steam turbine, there is no fitting portion 431Aa of the first annular portion 431A in the steam turbine 4A having the structure shown in Figure 4A. Therefore, compared to the steam turbine 4A having the structure shown in Figure 4A, the annular body 43 can be made smaller than the inner casing 435A in the steam turbine 4A having the structure shown in Figure 4A. This allows the high-pressure turbine 4 and the steam turbine 20 shown in Figure 2 to be made smaller. In other words, the high-pressure turbine 4 shown in Figure 2 can supply higher-pressure steam while maintaining the same size as the outer casing of a conventional steam turbine.

[0036] Furthermore, in the high-pressure turbine 4 shown in Fig. 2, the front stage blade ring 45 may be formed integrally with the annular body 43. That is, in the high-pressure turbine 4 shown in Fig. 2, the annular body 43 may have a configuration similar to that in which the blade ring 433A and the inner casing 435A are formed integrally. For example, Fig. 4B is a cross-sectional view showing an outline of the structure of a part of a high-pressure turbine 4B including an inner casing 435B equivalent to the blade ring 433A and the inner casing 435A in Fig. 4A formed integrally. The high-pressure turbine 4B shown in Fig. 4B includes a first annular portion 431B that is a separate member from the inner casing 435B.

[0037] In the high-pressure turbine 4B shown in Fig. 4B , the inner casing 435B has a stator vane holding region 433B. The stator vane holding region 433B is an area corresponding to a member called a blade ring in a conventional steam turbine, and is an area that holds multiple stages of stator vanes 19. In the high-pressure turbine 4B shown in Fig. 4B , the inner casing 435B is divided by a horizontal plane into an inner casing upper half 435BU and an inner casing lower half (not shown). In the following description, when there is no need to distinguish between the inner casing upper half 435BU and the inner casing lower half, they may be simply referred to as the inner casing 435B.

[0038] In the high-pressure turbine 4B shown in FIG. 4B , the first annular portion 431B has a configuration similar to that of the first annular portion 431A in the high-pressure turbine 4A shown in FIG. 4A . That is, in the high-pressure turbine 4B shown in FIG. 4B , the first annular portion 431B has a fitting portion 431Ba that fits with the inner casing 435B. The first annular portion 431B is a member known as a dummy ring in conventional steam turbines. The first annular portion 431B corresponds to the first annular portion 431 in the high-pressure turbine 4 shown in FIG. 2 described above, and has an extension portion 440 similar to the first annular portion 431. In the high-pressure turbine 4B shown in FIG. 4B , the first annular portion 431B is divided in a horizontal plane into a first annular portion upper half 431BU and a first annular portion lower half (not shown). In the following description, when there is no need to distinguish between the first annular portion upper half 431BU and the first annular portion lower half, they may be simply referred to as the first annular portion 431B.

[0039] Also, for example, Fig. 4C is a cross-sectional view showing the outline of the structure of a part of a high-pressure turbine 4C including an inner casing 435C that corresponds to the integrally formed annular body 43 and front stage blade ring 45 in the high-pressure turbine 4 shown in Fig. 2. The inner casing 435C of the high-pressure turbine 4C shown in Fig. 4C corresponds to the integrally formed inner casing 435B and first annular portion 431B in the high-pressure turbine 4B shown in Fig. 4B.

[0040] In the high-pressure turbine 4C shown in Fig. 4C , the inner casing 435C has a first annular portion 431C similar to the first annular portion 431 in the high-pressure turbine 4 shown in Fig. 2 and a stator vane holding region 433C similar to the stator vane holding region 433B in the high-pressure turbine 4B shown in Fig. 4B . In the high-pressure turbine 4C shown in Fig. 4C , the inner casing 435C is divided by a horizontal plane into an inner casing upper half 435CU and an inner casing lower half (not shown). In the following description, when there is no need to distinguish between the inner casing upper half 435CU and the inner casing lower half, they may be simply referred to as the inner casing 435C.

[0041] FIG. 4D is a cross-sectional view showing the outline of the structure of a part of the high-pressure turbine 4 shown in FIG.

[0042] (Regarding the First-Stage Stator Vanes 19A) The following describes the first-stage stator vanes 19A according to some embodiments. Fig. 5A is a schematic enlarged view of the vicinity of the first-stage stator vane 19A according to some embodiments. Fig. 5B is a schematic enlarged view of the vicinity of the first-stage stator vane 19A according to some embodiments, showing another example of the second annular portion 200 described below. Fig. 5C is a schematic enlarged view of the vicinity of the first-stage stator vane 19A according to some embodiments, showing yet another example of the second annular portion 200 described below. The first-stage stator vane 19A according to some embodiments has an airfoil portion 191, an outer shroud 192 located radially outward from the airfoil portion 191, and an inner shroud 193 located radially inward from the airfoil portion 191.

[0043] Here, the blade ring grooves 455 into which the outer shrouds 192 are inserted will be described. As shown in Fig. 5A , the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C have blade ring grooves 455 into which the outer shrouds 192 of the multiple first stage stator vanes 19A are inserted, and groove portions 456 into which parts of caulking members 460, which will be described later, fit. The blade ring grooves 455 are recessed radially outward from the radially inner surface facing the main steam flow path 21 in the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C, and extend in the circumferential direction.

[0044] The groove 456 is recessed from the axially upstream side surface 455u of the blade ring groove 455 toward the axially upstream side and extends circumferentially. A region of the axially upstream side surface 455u of the blade ring groove 455 that is radially inward of the groove 456 is axially separated from each of the axially upstream side surfaces 192u of the outer shroud 192 inserted into the blade ring groove 455. Therefore, the groove 456, the side surface 455u, and each of the axially upstream side surfaces 192u of the outer shroud 192 inserted into the blade ring groove 455 form a storage space 457 having an L-shaped cross section perpendicular to the circumferential direction. A caulking member 460, as described below, is inserted into the storage space 457. The storage space 457 is open radially inward.

[0045] The caulking member 460 is a member for restricting movement of the multiple first-stage stator vanes 19A relative to the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C. The caulking member 460 is a ring-shaped member extending in the circumferential direction, and is formed of a metal that is softer than the first-stage stator vanes 19A, such as stainless steel. The cross-sectional shape of the caulking member 460 perpendicular to the circumferential direction is L-shaped so that it can be accommodated in the L-shaped storage space 457.

[0046] The caulking members 460 are inserted into the storage space 457 from the circumferential ends of the forward stage blade ring upper half 45U, the forward stage blade ring lower half 45L, the blade ring upper half 433AU, the blade ring lower half (not shown) of the blade ring 433A, the upper and lower halves of the stator vane holding area 433B, and the upper and lower halves of the stator vane holding area 433C. Then, the radially inner end of the caulking member 460 is struck from a radially inner opening of the storage space 457 using a tool such as a hammer, thereby plastically deforming the caulking member 460 within the storage space 457. As a result, the multiple outer shrouds 192 are crimped to the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C by the caulking members 460. Therefore, the outer shrouds 192 of the multiple first stage stator vanes 19A are constrained so as not to be able to move radially and axially relative to the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C.

[0047] Returning now to the description of the first-stage stator vanes 19A, each of the inner shrouds 193 of the multiple first-stage stator vanes 19A has an attachment portion 194 for attaching a second annular portion 200 (described later) to the inner shroud 193. The attachment portion 194 is, for example, an engagement groove 195 that is recessed radially outward from the radially inner surface of the inner shroud 193 and extends in the circumferential direction. The engagement groove 195 is formed, for example, so that the axial dimension of the engagement groove 195 is larger on the radially outer side than on the radially inner side. This makes it possible to restrict radially inward and axial movement of the second annular portion 200 relative to the inner shroud 193 with an engagement protrusion 201 of the second annular portion 200 (described later) inserted into the engagement groove 195.

[0048] (Regarding the second annular portion 200 and the extension portion 440) The second annular portion 200 according to some embodiments will be described below, along with the extension portion 440 of the first annular portion 431, 431A, 431B, 431C. As shown in Figures 5A, 5B, and 5C, the second annular portion 200 according to some embodiments is a member that protrudes axially upstream from a region radially inward of the inner shroud 193 of the first stage stator vane 19A and extends in the circumferential direction, and has an engaging protrusion 201 and a second radial opposing portion 203. The second annular portion 200 shown in Figures 5A and 5C also has a flow passage forming region 205 that defines a portion of the first cavity 71, and a second axial opposing portion 207. Note that the second annular portion 200 according to some embodiments is divided into at least two parts: a lower half of the second annular portion 200 attached to the forward stage blade ring lower half 45L, the lower half of the blade ring 433A, or the first stage stator vanes 19A held in the lower half of the stator vane holding area 433B or the stator vane holding area 433C, and an upper half of the second annular portion 200 attached to the forward stage blade ring upper half 45U, the blade ring upper half 433AU, or the first stage stator vanes 19A held in the upper half of the stator vane holding area 433B or the stator vane holding area 433C. In the second annular portion 200 according to some embodiments, the lower half and the upper half of the second annular portion 200 are further divided into a plurality of (for example, two) members in the circumferential direction.

[0049] (Engagement protrusion 201) The engagement protrusion 201 is a protrusion that protrudes radially outward from an axially downstream region of the second annular portion 200 and extends in the circumferential direction. The engagement protrusion 201 is a protrusion that can engage with the engagement groove 195 of the inner shroud 193, and is formed, for example, so that the axial dimension of the engagement protrusion 201 is larger on the radially outer side than on the radially inner side. In other words, the cross-sectional shape of the engagement protrusion 201 perpendicular to the circumferential direction is similar to the cross-sectional shape of the engagement groove 195 of the inner shroud 193 perpendicular to the circumferential direction. This makes it possible to restrict radially inward and axial movement of the second annular portion 200 relative to the inner shroud 193 when the engagement protrusion 201 is inserted into the engagement groove 195 of the inner shroud 193. That is, the engaging protrusions 201 extend in the circumferential direction so as to be inserted into the engaging grooves 195 of at least two or more inner shrouds 193 that are aligned in the circumferential direction, and restrict relative movement in the axial and radial directions between the circumferentially adjacent inner shrouds 193. Therefore, the strength of the first stage stator vane 19A is improved compared to a case in which the second annular portion 200 is not attached to the inner shroud 193.

[0050] 5A , 5B , and 5C , in the second annular portion 200 according to some embodiments, the radially second opposing portion 203 is a portion that radially faces the radially first opposing portion 441 of the extending portion 440 of the first annular portion 431, 431A, 431B, 431C. That is, the extending portion 440 of the first annular portion 431, 431A, 431B, 431C has the radially first opposing portion 441 that radially faces the radially second opposing portion 203 at the axially downstream end of the extending portion 440. The radially first opposing portion 441 of the extending portion 440 and the radially second opposing portion 203 face each other with a gap therebetween in the radial direction. A sealing device 52 is provided between the radial first opposing portion 441 and the radial second opposing portion 203 to seal the gap between the radial first opposing portion 441 and the radial second opposing portion 203. The sealing device 52 is, for example, a labyrinth seal having sealing fins.

[0051] 5A and 5B , the radially second opposing portions 203 are located radially inward of the radially first opposing portions 441 of the extending portion 440. In the second annular portion 200 shown in FIG. 5C , the radially second opposing portions 203 are located radially outward of the radially first opposing portions 441 of the extending portion 440.

[0052] 5A and 5C , the flow passage forming region 205 has a surface 205s that defines a portion of the first cavity 71, i.e., a portion of the steam inlet flow passage 75. The surface 205s is located between an axially downstream edge 442d of a radially outer surface 442 of the extension portion 440 of each of the first annular portions 431, 431A, 431B, and 431C and an axially upstream edge 193su of a radially outer surface 193s of the inner shroud 193. The radially outer surface 442 of the extension portion 440 defines a portion of the first cavity 71, i.e., a portion of the steam inlet flow passage 75. In the second annular portion 200 shown in FIG. 5C , the second radially opposing portion 203 is part of the flow passage forming region 205.

[0053] (Axial second opposing portion 207 and axial first opposing portion 443) The second annular portion 200 shown in Figures 5A and 5C has an axial second opposing portion 207 that extends radially inward from an axially upstream edge 205su of a surface 205s of the flow passage forming region 205 and extends in the circumferential direction. The first annular portions 431, 431A, 431B, and 431C shown in Figures 5A, 5B, and 5C have an axial first opposing portion 443 that extends radially inward from an axially downstream edge 442d of a radially outer surface 442 of the extension portion 440 and extends in the circumferential direction. The axial first opposing portion 443 and the axial second opposing portion 207 shown in Figures 5A and 5C face each other with a space between them in the axial direction. Therefore, when the high-pressure turbines 4, 4A, 4B, and 4C are operating, the first axial opposing portion 443 moves axially downstream and the second axial opposing portion 207 moves axially upstream, but the first axial opposing portion 443 and the second axial opposing portion 207 do not come into contact with each other.

[0054] 5B faces but is spaced apart from the axially upstream surface 193u of the inner shroud 193. Therefore, even if the first axially opposing part 443 moves axially downstream during operation of the high-pressure turbine 4, 4A, 4B, 4C and the surface 193u of the axially upstream side of the inner shroud 193 moves axially upstream, the first axially opposing part 443 and the surface 193u of the axially upstream side of the inner shroud 193 do not come into contact with each other.

[0055] 5A , in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the axial position of the axially downstream end 443 d of the first axially opposing portion 443 may be located axially upstream of the axial position of the axially upstream end 451 u of the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the stator vane holding area 433C. This prevents interference between the end 443 d of the first axially opposing portion 443 and the forward stage blade ring 45, the blade ring 433A, the stator vane holding area 433B, and the end 451 u of the inner region 451 of the stator vane holding area 433C during disassembly and assembly of the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, facilitating disassembly and assembly of the high-pressure turbines 4, 4A, 4B, and 4C.

[0056] The steam turbine 20 according to some embodiments described above has the following features. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes an inner casing 435A, 435B, 435C or an inner casing region 435 corresponding to the inner casing 435A, 435B, 435C. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes a first annular portion 431, 431A, 431B, 431C coupled to the inner casing 435A, 435B, 435C or formed integrally with the inner casing region 435, defining at least a portion of the steam inlet flow passage 75, and holding a sealing device 51 disposed on the outer circumferential surface 13a of the rotor 13. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes a plurality of first-stage stator vanes 19A arranged at intervals in the circumferential direction. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes a blade ring 433A, a forward stage blade ring 45, or a stator vane holding region 433B, 433C coupled to the inner casing 435A or the inner casing region 435 or formed integrally with the inner casing 435B, 435C and holding at least a plurality of first-stage stator vanes 19A. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes a second annular portion 200 attached to the inner shrouds 193 of the first-stage stator vanes 19A of the plurality of first-stage stator vanes 19A. The high-pressure turbine 4, 4A, 4B, 4C according to some embodiments includes a sealing device 52 provided between the first annular portion 431, 431A, 431B, 431C and the second annular portion 200.

[0057] According to the high-pressure turbines 4, 4A, 4B, and 4C of some embodiments, the strength of the first stage stator vanes 19A can be improved by the second annular portion 200. Furthermore, according to the high-pressure turbines 4, 4A, 4B, and 4C of some embodiments, the sealing device 52 is provided between the first annular portions 431, 431A, 431B, and 431C and the second annular portion 200, so that leakage of steam from between the first annular portions 431, 431A, 431B, and 431C and the second annular portion 200 can be reduced.

[0058] 5A and 5C , in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the second annular portion 200 may have a flow passage forming region 205 that defines a part of the steam inlet flow passage 75 downstream in the axial direction of the region defined by the first annular portions 431, 431A, 431B, and 431C of the steam inlet flow passage 75. This makes it possible to prevent the axially upstream surface 193u of the inner shroud 193, which is the axially upstream end of the inner shroud 193, from becoming too large in the axial direction, even if the axially upstream surface 193u and the first annular portions 431, 431A, 431B, and 431C become too large in the axial direction. This reduces the effect on the flow of steam caused by the axially upstream surface 193u becoming too large in the axial direction.

[0059] 5A, 5B, and 5C, in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the first annular portion 431, 431A, 431B, and 431C may have a radially first opposing portion 441 that faces the second annular portion 200 in the radial direction and is located radially inward of the blade ring 433A, the forward stage blade ring 45, or the stator vane retaining region 433B or 433C. The second annular portion 200 may have a radially second opposing portion 203 that faces the radially first opposing portion 441 in the radial direction. The sealing device 52 may seal a gap between the radially first opposing portion 441 and the radially second opposing portion 203. As a result, the first radial opposing portion 441 and the second radial opposing portion 203 overlap in the axial direction, and the sealing device 52 is disposed in this overlapping region to seal the gap between the first radial opposing portion 441 and the second radial opposing portion 203. This makes it possible to reduce steam leakage from the gap between the first annular portions 431, 431A, 431B, 431C and the second annular portion 200.

[0060] 5A , 5B , and 5C , in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the first radially opposing portion 441 and the second radially opposing portion 203 may be located upstream in the axial direction of the inner shroud 193. This eliminates the need for the first radially opposing portion 441 and the second radially opposing portion 203 to overlap with the inner shroud 193 in the radial direction, and therefore the diameter of the rotor 13 can be made larger than when the first radially opposing portion 441 and the second radially opposing portion 203 overlap with the inner shroud 193 in the radial direction, thereby ensuring the strength of the rotor 13.

[0061] 5A, 5B, and 5C, in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the second annular portion 200 may have an opposing surface 209 that radially faces the outer circumferential surface 13a of the rotor 13. The first radial opposing portion 441 and the second radial opposing portion 203 may be located radially outward of the opposing surface 209. This allows the diameter of the rotor 13 to be larger than when the first radial opposing portion 441 and the second radial opposing portion 203 are located radially inward of the opposing surface 209, thereby ensuring the strength of the rotor 13.

[0062] 5A and 5B , in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the second radially opposing portion 203 may be located radially inward of the first radially opposing portion 441. This makes it possible to easily assemble the high-pressure turbine 4, as will be described later, even if the inner casing region 435 and the first annular portion 431 are integrally formed, and even if the inner casing 435C and the first annular portion 431C are integrally formed.

[0063] In the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, as shown in Fig. 5C , the radially second opposing portion 203 may be located radially outward of the radially first opposing portion 441. This allows the steam turbine 4A to be easily assembled, as will be described later, when the inner casing 435A, the first annular portion 431A, and the blade ring 433A are configured to be separable.

[0064] 5A and 5C , in the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, the first annular portions 431, 431A, 431B, and 431C may have a first axially opposed portion 443 that faces the second annular portion 200 in the axial direction. The second annular portion 200 may have a second axially opposed portion 207 that faces and is spaced apart from the first axially opposed portion 443 in the axial direction. This allows the gap between the first axially opposed portion 443 and the second axially opposed portion 207 to absorb thermal expansion of the first annular portions 431, 431A, 431B, and 431C and the second annular portion 200.

[0065] In the high-pressure turbines 4, 4A, 4B, and 4C according to some embodiments, as shown in Figures 5A, 5B, and 5C, the second annular portion 200 may have an engagement protrusion 201 that protrudes radially outward and extends circumferentially. The inner shroud 193 may have an engagement groove 195 that is engageable with the engagement protrusion 201. When the engagement protrusion 201 engages with the engagement groove 195, the second annular portion 200 is restricted from moving in the radial and axial directions relative to the inner shroud 193. This restricts relative movement between the inner shroud 193 and the second annular portion 200 in the radial and axial directions, thereby improving the strength of the first-stage stator vane 19A.

[0066] In some embodiments of the high-pressure turbine 4, 4C, the first annular portion 431, 431C may be integrally formed with the inner casing region 435 or the inner casing 435C, as shown in Figures 2, 4C, and 4D. This allows the first annular portion 431, 431C to be made smaller than when the first annular portions 431A, 431B and the inner casings 435A, 435B are separate, as shown in Figures 4A and 4B, and therefore allows the high-pressure turbine 4, 4C to be made smaller. In other words, higher-pressure steam can be supplied while maintaining the same size as the outer casing 41A, 41C when the first annular portions 431A, 431B and the inner casings 435A, 435B are separate, as shown in Figures 4A and 4B.

[0067] In the high-pressure turbine 4, 4A according to some embodiments, as shown in Figures 2, 4A, and 4D, the forward stage blade ring 45 and the blade ring 433A may be separate members from the inner casing region 435 and the inner casing 435A, and may be coupled to the separate members, the inner casing region 435 and the inner casing 435A. That is, as shown in Figures 2, 4A, and 4D, in the high-pressure turbine 4, 4A, the forward stage blade ring 45 and the inner casing region 435 may be separate members, and the blade ring 433A and the inner casing 435A may be separate members.

[0068] In the high-pressure turbine 4 according to some embodiments, the forward stage blade ring 45 may be formed integrally with the inner casing region 435. That is, in the high-pressure turbine 4 shown in Figure 2, the forward stage blade ring 45 and the inner casing region 435 may be formed integrally like the inner casings 435B and 435C in the high-pressure turbines 4B and 4C shown in Figures 4B and 4C.

[0069] In the high-pressure turbine 4A according to some embodiments, as shown in Fig. 4A , the first annular portion 431A may be a separate member from the inner casing 435A and may be coupled to the inner casing 435A. The blade ring 433A may be a separate member from the inner casing 435A and coupled to the inner casing 435A. That is, as shown in Fig. 4A , in the high-pressure turbine 4A, the first annular portion 431A, the inner casing 435A, and the blade ring 433A may be separate members.

[0070] (Method of assembling high-pressure turbine) Fig. 6 is a flowchart showing the procedure for assembling the high-pressure turbine 4 shown in Fig. 2 and Fig. 4D, which includes the annular body 43 and the front stage blade ring 45 that is a member different from the annular body 43. Fig. 7 is a flowchart showing the procedure for assembling the high-pressure turbine 4C shown in Fig. 4C, in which the annular body 43 and the front stage blade ring 45 are integrally formed. Fig. 8 is a flowchart showing the procedure for assembling the high-pressure turbine 4A shown in Fig. 4A, in which the first annular portion 431A, the blade ring 433A, and the inner casing 435A are each separate members.

[0071] (Method of assembling high-pressure turbine 4) A method of assembling the high-pressure turbine 4 shown in Figures 2 and 4D, which includes the annular body 43 and the front stage blade ring 45, which is a different member from the annular body 43, includes a first step S11, a second step S12, a third step S13, and a fourth step S14, as shown in Figure 6. In the high-pressure turbine 4 assembled using the assembly procedure shown in Figure 6, the radial second opposing portion 203 is located radially inward of the radial first opposing portion 441, as shown in Figure 5A or 5B. In the high-pressure turbine 4 assembled using the assembly procedure shown in Figure 6, the axial position of the axially downstream end 443d of the axial first opposing portion 443 is located axially upstream of the axial position of the front stage blade ring 45 and the axially upstream end 451u of the inner region 451 of the blade ring 433A, as shown in Figure 5A.

[0072] (First Step S11) The first step S11 is a step of attaching a forward stage blade ring lower half 45L, in which a plurality of stator vanes 19, including a plurality of first-stage stator vanes 19A, are attached to an annular body lower half 43L molded integrally with the lower half of the first annular portion 431, and the lower half of the second annular portion 200 is attached to the inner shroud 193 of the first-stage stator vanes 19A. Prior to the execution of the first step S11, the annular body lower half 43L is pre-attached to the outer casing lower half 41L. Prior to the execution of the first step S11, a sealing device 52 is pre-attached to the radially first opposing portion 441 of the extending portion 440 of the first annular portion 431 in the annular body lower half 43L.

[0073] 5A , the axial position of the axially downstream end 443d of the axially first opposing portion 443 is located axially upstream of the axial position of the axially upstream end 451u of the inner region 451 of the forward stage blade ring 45. Therefore, when the forward stage blade ring lower half 45L is lowered vertically downward relative to the annular body lower half 43L in the first step S11, there is no interference between the end 443d of the axially first opposing portion 443 of the annular body lower half 43L and the end 451u of the inner region 451 of the forward stage blade ring lower half 45L.

[0074] In addition, when the lower half 45L of the forward stage blade ring is attached in the first step S11, the radial second opposing portion 203 of the lower half part of the second annular portion 200 attached to the lower half 45L of the forward stage blade ring is positioned radially inward relative to the radial first opposing portion 441, with the sealing device 52 sandwiched between them.

[0075] (Second Step S12) The second step S12 is a step of attaching the rotor 13, to which the plurality of blades 18 are attached, to the annular body lower half 43L and the forward stage blade ring lower half 45L after the first step S11 is performed.

[0076] (Third step S13) The third step S13 is a step of attaching a forward stage blade ring upper half 45U to the forward stage blade ring lower half 45L after the second step S12 is performed, in which a plurality of stator vanes 19 including a plurality of first stage stator vanes 19A are attached, and the upper half of the second annular portion 200 is attached to the inner shroud 193 of the first stage stator vanes 19A.

[0077] (Fourth Step S14) The fourth step S14 is a step of attaching the annular body upper half 43U, which is molded integrally with the upper half of the first annular portion 431, to the annular body lower half 43L after the third step S13 is performed. Note that, prior to the performance of the fourth step S14, the sealing device 52 is attached in advance to the radial first opposing portion 441 of the extending portion 440 of the first annular portion 431 in the annular body upper half 43U.

[0078] 5A , the axial position of the axially downstream end 443d of the axially first opposing portion 443 is located axially upstream of the axial position of the axially upstream end 451u of the inner region 451 of the forward stage blade ring 45. Therefore, when the annular body upper half 43U is lowered vertically downward relative to the annular body lower half 43L in the fourth step S14, there is no interference between the end 443d of the axially first opposing portion 443 of the annular body upper half 43U and the end 451u of the inner region 451 of the forward stage blade ring upper half 45U.

[0079] Furthermore, when the annular body upper half 43U is attached in the fourth step S14, the radial second opposing portion 203 of the upper half of the second annular portion 200 attached to the front stage blade ring upper half 45U is positioned radially inward of the radial first opposing portion 441, with the sealing device 52 sandwiched between them, as shown in Figure 5A or 5B.

[0080] In the assembly procedure for the high-pressure turbine 4 shown in Figure 2, which includes the annular body 43 and the front stage blade ring 45, which is a component different from the annular body 43, after the fourth step S14 is performed, the outer casing upper half 41U is attached to the outer casing lower half 41L.

[0081] According to the assembly procedure shown in FIG. 6, the high-pressure turbine 4 shown in FIG. 2 and including the annular body 43 and the forward stage blade ring 45 which is a member different from the annular body 43 can be easily assembled.

[0082] (Method of assembling high-pressure turbine 4C in which front stage blade ring 45 and annular body 43 are integrally formed) A method of assembling a high-pressure turbine 4C in which the front stage blade ring 45 and annular body 43 are integrally formed as shown in Fig. 4C includes a first step S21 and a second step S22 as shown in Fig. 7. In the high-pressure turbine 4C assembled using the assembly procedure shown in Fig. 7, the radial second opposing portion 203 is positioned radially inward of the radial first opposing portion 441 as shown in Fig. 5A or 5B.

[0083] (First Step S21) The first step S21 is a step of attaching the rotor 13, on which a plurality of blades 18 are attached, to the annular body lower half 43L. Here, in the high-pressure turbine 4C shown in FIG. 4C , the lower half of the inner casing 435C is integrally molded with the stator vane holding region 433C and the first annular portion 431C. The stator vane holding region 433C holds a plurality of stator vanes 19 including a plurality of first-stage stator vanes 19A, and the lower half of the second annular portion 200 is attached to the inner shroud 193 of the first-stage stator vanes 19A. Note that prior to carrying out the first step S21, the lower half of the inner casing 435C is attached to the lower half of the outer casing 41C in advance.

[0084] Furthermore, prior to performing the first step S21, when the first stage stator vanes 19A are attached to the stator vane holding region 433C in the lower half of the inner casing 435C, the outer shroud 192 is first inserted circumferentially into the blade ring groove 455 of the stator vane holding region 433C, and the caulking member 460 is also inserted circumferentially into the storage space 457. Then, a tool such as a hammer is used to strike the radially inner end of the caulking member 460 through a gap between the axially upstream surface 193u of the inner shroud 193 and the end 443d of the first axial opposing portion 443 of the extending portion 440 of the first annular portion 431, thereby plastically deforming the caulking member 460 within the storage space 457. After the outer shroud 192 is crimped to the stator vane holding region 433C by the caulking member 460 in this manner, the second annular portion 200 is attached to the inner shroud 193.

[0085] (Second Step S22) The second step S22 is a step of attaching an inner casing upper half 435CU to the lower half of the inner casing 435C after the first step S21 is performed. Here, in the high-pressure turbine 4C shown in Fig. 4C , the inner casing upper half 435CU is integrally molded with the stator vane holding region 433C and the first annular portion 431C. The stator vane holding region 433C holds a plurality of stator vanes 19 including a plurality of first-stage stator vanes 19A, and the upper half of the second annular portion 200 is attached to the inner shroud 193 of the first-stage stator vanes 19A.

[0086] Furthermore, prior to performing the second step S22, when the first stage stator vanes 19A are attached to the stator vane holding region 433C of the inner casing upper half 435CU, first, the outer shroud 192 is inserted circumferentially into the blade ring groove 455 of the stator vane holding region 433C, and the caulking member 460 is inserted circumferentially into the storage space 457. Then, a tool such as a hammer is used to strike the radially inner end of the caulking member 460 through a gap between the axially upstream surface 193u of the inner shroud 193 and the end 443d of the first axial opposing portion 443 of the extending portion 440 of the first annular portion 431, thereby plastically deforming the caulking member 460 within the storage space 457. After the outer shroud 192 is crimped to the stator vane holding region 433C by the caulking member 460 in this manner, the second annular portion 200 is attached to the inner shroud 193.

[0087] In the method of assembling the high-pressure turbine 4C in which the front stage blade ring 45 and the annular body 43 are integrally formed, after the second step S22 is performed, the upper half of the outer casing 41C is attached to the lower half of the outer casing 41C.

[0088] According to the assembly procedure shown in FIG. 7, the high-pressure turbine 4C in which the annular body 43 and the front stage blade ring 45 are integrally formed can be easily assembled.

[0089] (Method of assembling high-pressure turbine 4A) A method of assembling the high-pressure turbine 4A shown in Fig. 4A in which the first annular portion 431A, the blade ring 433A, and the inner casing 435A are separate members includes a first step S31, a second step S32, a third step S33, a fourth step S34, a fifth step S35, and a sixth step S36 as shown in Fig. 8. In the high-pressure turbine 4A assembled using the assembly procedure shown in Fig. 8, the radially second opposing portion 203 is positioned radially outward of the radially first opposing portion 441 as shown in Fig. 5C.

[0090] (First Step S31) The first step S31 is a step of attaching the lower half of the blade ring 433A to the lower half of the inner casing 435A. It is assumed that, prior to carrying out the first step S31, the lower half of the inner casing 435A has been attached to the lower half of the outer casing 41 in advance. It is also assumed that, prior to carrying out the first step S31, a plurality of stator vanes 19 including a plurality of first-stage stator vanes 19A have been attached to the lower half of the blade ring 433A, and the lower half of the second annular portion 200 has been attached to the inner shroud 193 of the first-stage stator vanes 19A.

[0091] (Second step S32) The second step S32 is a step of attaching the lower half of the first annular portion 431A to the lower half of the inner casing 435A and the lower half of the blade ring 433A after the first step S31 is performed. Note that, prior to the performance of the second step S32, the sealing device 52 is attached in advance to the radially first opposing portion 441 of the extending portion 440 in the lower half of the first annular portion 431A.

[0092] When the lower half of the first annular portion 431A is attached in the second step S32, the second radial opposing portion 203 of the lower half of the second annular portion 200 is positioned radially outward from the first radial opposing portion 441, sandwiching the sealing device 52 therebetween.

[0093] (Third step S33) The third step S33 is a step of attaching the rotor 13, to which a plurality of blades 18 are attached, to the lower half of the inner casing 435A, the lower half of the blade ring 433A, and the lower half of the first annular portion 431A after the second step S32 is performed.

[0094] (Fourth Step S34) The fourth step S34 is a step of attaching the first annular portion upper half 431AU to the lower half of the first annular portion 431A after the third step S33 is performed. Note that, prior to the fourth step S34, the sealing device 52 is attached to the first radial opposing portion 441 of the extending portion 440 of the first annular portion upper half 431AU.

[0095] (Fifth Step S35) The fifth step S35 is a step of attaching a blade ring upper half 433AU to the lower half of the blade ring 433A after the fourth step S34 is performed. Note that prior to the fifth step S35, a plurality of stator vanes 19 including a plurality of first-stage stator vanes 19A are attached to the blade ring upper half 433AU, and the upper half of the second annular portion 200 is attached to the inner shroud 193 of the first-stage stator vanes 19A.

[0096] When the upper half of the blade ring 433AU is attached in the fifth step S35, the second radial opposing portion 203 of the upper half of the second annular portion 200 attached to the upper half of the blade ring 433AU is positioned radially outward from the first radial opposing portion 441, sandwiching the sealing device 52, as shown in Figure 5C.

[0097] (Sixth Step S36) The sixth step S36 is a step of attaching the inner casing upper half 435AU to the lower half of the inner casing 435A after the fifth step S35 is performed. Note that, if the inner casing upper half 435AU is provided with the aft stage stator vane holding region 433, a plurality of stator vanes 19 are attached to the aft stage stator vane holding region 433 prior to the sixth step S36. Also, if the inner casing upper half 435AU is not provided with the aft stage stator vane holding region 433, a plurality of stator vanes 19 are attached to the upper half of the blade ring corresponding to the aft stage stator vane holding region 433, and then, prior to the sixth step S36, the upper half of the blade ring corresponding to the aft stage stator vane holding region 433 is attached to the lower half of the blade ring corresponding to the aft stage stator vane holding region 433.

[0098] In the method of assembling the high-pressure turbine 4A shown in FIG. 4A in which the first annular portion 431A, the blade ring 433A, and the inner casing 435A are each separate components, after performing the sixth step S36, the upper half of the outer casing 41A is attached to the lower half of the outer casing 41A.

[0099] According to the assembly procedure shown in FIG. 8, it is possible to easily assemble the high-pressure turbine 4A shown in FIG. 4A in which the first annular portion 431A, the blade ring 433A, and the inner casing 435A are each separate members.

[0100] The present disclosure is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and appropriate combinations of these embodiments. For example, the configurations of the high-pressure turbines 4, 4A, 4B, and 4C in the above-described embodiments can also be applied to the intermediate-pressure turbine 8 and the low-pressure turbine 10.

[0101] The contents of the above-described embodiments can be understood as follows, for example. (1) A steam turbine (high-pressure turbine 4, 4A, 4B, 4C) according to at least one embodiment of the present disclosure includes an inner casing (an inner casing 435A, 435B, 435C or an inner casing region 435 corresponding to the inner casing 435A, 435B, 435C). The steam turbine (high-pressure turbine 4, 4A, 4B, 4C) according to at least one embodiment of the present disclosure includes a first annular portion 431, 431A, 431B, 431C that is coupled to the inner casing (the inner casing 435A, 435B) or is formed integrally with the inner casing (the inner casing 435C or the inner casing region 435), defines at least a portion of the steam inlet flow path 75, and holds a first seal device (seal device 51) that is disposed on an outer circumferential surface 13 a of the rotor 13. A steam turbine (high-pressure turbine 4, 4A, 4B, 4C) according to at least one embodiment of the present disclosure includes a plurality of first-stage stator vanes 19A arranged at intervals in the circumferential direction of the rotor 13, and having an airfoil portion 191 and an inner shroud 193 positioned radially inward of the airfoil portion 191. The steam turbine (high-pressure turbine 4, 4A, 4B, 4C) according to at least one embodiment of the present disclosure includes a blade ring (blade ring 433A, forward stage blade ring 45, or stator vane holding region 433B, 433C) coupled to an inner casing (inner casing 435A or inner casing region 435) or formed integrally with the inner casing (inner casing 435B, 435C) and holding at least a plurality of first-stage stator vanes 19A. A steam turbine (high-pressure turbine 4, 4A) according to at least one embodiment of the present disclosure includes a second annular portion 200 attached to inner shrouds 193 of a plurality of first-stage stator vanes 19A. A steam turbine (high-pressure turbine 4, 4A, 4B, 4C) according to at least one embodiment of the present disclosure includes a second sealing device (sealing device 52) provided between the first annular portion 431, 431A, 431B, 431C and the second annular portion 200.

[0102] According to the above configuration (1), the strength of the first stage stator vane 19A can be improved by the second annular portion 200. Furthermore, according to the above configuration (1), the second sealing device (sealing device 52) is provided between the first annular portions 431, 431A, 431B, 431C and the second annular portion 200, so that leakage of steam from between the first annular portions 431, 431A, 431B, 431C and the second annular portion 200 can be reduced.

[0103] (2) In some embodiments, in the configuration of (1) above, the second annular portion 200 may have a flow path forming region 205 that defines a portion of the steam inlet flow path 75 downstream in the axial direction of the rotor 13 from the region defined by the first annular portions 431, 431A, 431B, and 431C.

[0104] According to the configuration (2) above, even if the axial distance between the axially upstream end portion of the inner shroud 193 (the axially upstream surface 193u of the inner shroud 193) and the first annular portions 431, 431A, 431B, 431C is larger than necessary, the passage forming region 205 can prevent the distance from becoming too large. This can reduce the effect on the flow of steam caused by the distance becoming larger than necessary.

[0105] (3) In some embodiments, in the configuration described in (1) or (2) above, the first annular portion 431, 431A, 431B, 431C may have a radially first opposing portion 441 that faces the second annular portion 200 in the radial direction of the rotor 13, on a radially inner side of the rotor 13 than the blade ring (the blade ring 433A, the forward stage blade ring 45, or the stator vane retaining region 433B, 433C). The second annular portion 200 may have a radially second opposing portion 203 that faces the radially first opposing portion 441 in the radial direction. The second seal device (seal device 52) may seal a gap between the radially first opposing portion 441 and the radially second opposing portion 203.

[0106] According to the configuration (3) above, the first radial opposing portion 441 and the second radial opposing portion 203 overlap in the axial direction, and the second sealing device (sealing device 52) is disposed in this overlapping region to seal the gap between the first radial opposing portion 441 and the second radial opposing portion 203. This makes it possible to reduce steam leakage from the gap between the first annular portions 431, 431A, 431B, 431C and the second annular portion 200.

[0107] (4) In some embodiments, in the configuration of (3) above, the first radially opposed portion 441 and the second radially opposed portion 203 may be located upstream of the inner shroud 193 in the axial direction.

[0108] According to the configuration (4) above, the first radial opposing portion 441 and the second radial opposing portion 203 do not need to overlap radially with the inner shroud 193, so the diameter of the rotor 13 can be made larger than when the first radial opposing portion 441 and the second radial opposing portion 203 overlap radially with the inner shroud 193, and the strength of the rotor 13 can be ensured.

[0109] (5) In some embodiments, in the configuration of (4) above, the second annular portion 200 may have an opposing surface 209 that radially faces the outer circumferential surface 13 a of the rotor 13. The first radial opposing portion 441 and the second radial opposing portion 203 may be located radially outward of the rotor with respect to the opposing surface 209.

[0110] According to the configuration (5) above, the diameter of the rotor 13 can be made larger than when the radial first opposing portion 441 and the radial second opposing portion 203 are positioned radially inward from the opposing surface 209, thereby ensuring the strength of the rotor 13.

[0111] (6) In some embodiments, in any of the configurations (3) to (5) above, the second radially opposing portion 203 may be located radially inward of the rotor 13 relative to the first radially opposing portion 441 .

[0112] According to the configuration (6) above, even if the inner casing (inner casing region 435, inner casing 435C) and the first annular portion (first annular portion 431, 431C) are integrally formed, the steam turbine (high-pressure turbine 4, 4C) can be easily assembled.

[0113] (7) In some embodiments, in any of the configurations (3) to (5) above, the second radial opposing portion 203 may be located radially outward of the rotor 13 than the first radial opposing portion 441.

[0114] According to the configuration of (7) above, the radially second opposing portion 203 may be located radially outward of the rotor 13 relative to the radially first opposing portion 441. Furthermore, according to the configuration of (7) above, when the inner casing 435A, the first annular portion 431A, and the blade ring 433A are configured to be separable, the steam turbine 4A can be easily assembled.

[0115] (8) In some embodiments, in any of the configurations (1) to (7) above, the first annular portion 431, 431A, 431B, 431C may have a first axial facing portion 443 that faces the second annular portion 200 in the axial direction of the rotor 13. The second annular portion 200 may have a second axial facing portion 207 that faces the first axial facing portion 443 and is spaced apart in the axial direction.

[0116] According to the configuration (8) above, the gap between the first axial opposing portion 443 and the second axial opposing portion 207 can absorb thermal expansion of the first annular portions 431 , 431A, 431B, 431C and the second annular portion 200 .

[0117] (9) In some embodiments, in any of the configurations (1) to (8) above, the second annular portion 200 may have a protrusion (engagement protrusion 201) that protrudes radially outward from the rotor 13 and extends in the circumferential direction. The inner shroud 193 may have a recess (engagement groove 195) that can engage with the protrusion (engagement protrusion 201). When the protrusion (engagement protrusion 201) engages with the recess (engagement groove 195), the second annular portion 200 may restrict radial and axial movement of the rotor 13 relative to the inner shroud 193.

[0118] According to the configuration (9) above, the relative movement between the inner shroud 193 and the second annular portion 200 in the radial and axial directions is restricted, so that the strength of the first stage stator vane 19A can be improved.

[0119] (10) In some embodiments, in any of the configurations (1) to (9) above, the first annular portion 431, 431C may be formed integrally with the inner casing (inner casing region 435, inner casing 435C).

[0120] According to the configuration of (10) above, the first annular portions 431A, 431B and the inner casings 435A, 435B can be made smaller, and the steam turbine (high-pressure turbine 4, 4C) can be made smaller than when the first annular portions 431A, 431B and the inner casings 435A, 435B are separate. In other words, according to the configuration of (10) above, higher-pressure steam can be supplied while maintaining the same physical size as the physical size of the outer casing 41A when the first annular portions 431A, 431B and the inner casings 435A, 435B are separate.

[0121] (11) In some embodiments, in the configuration of (10) above, the blade ring (the forward stage blade ring 45 and the blade ring 433A) may be a separate member from the inner casing (the inner casing region 435 and the inner casing 435A) and may be connected to the inner casing (the inner casing region 435 and the inner casing 435A).

[0122] According to the configuration of (11) above, the blade ring (the forward stage blade ring 45 and the blade ring 433A) and the inner casing (the inner casing region 435 and the inner casing 435A) may be separate bodies.

[0123] (12) In some embodiments, in the configuration of (10) above, the blade ring (forward stage blade ring 45) may be formed integrally with the inner casing (inner casing region 435).

[0124] According to the configuration of (12) above, the blade ring (forward stage blade ring 45) and the inner casing (inner casing region 435) may be formed integrally.

[0125] (13) In some embodiments, in any of the configurations described in (1) to (9) above, the first annular portion 431A may be a separate member from the inner casing 435A and may be coupled to the inner casing 435A. The blade ring 433A may be a separate member from the inner casing 435A and may be coupled to the inner casing 435A.

[0126] According to the configuration of (13) above, the first annular portion 431A, the blade ring 433A, and the inner casing 435A may be separate bodies.

[0127] (14) In a method of assembling a steam turbine (high-pressure turbine 4) according to at least one embodiment of the present disclosure, the steam turbine (high-pressure turbine 4) includes an inner casing (inner casing region 435). The steam turbine (high-pressure turbine 4) includes a first annular portion 431 that is integrally formed with the inner casing (inner casing region 435), defines at least a portion of the steam inlet flow path 75, and holds a first sealing device (sealing device 51) that is arranged on the outer circumferential surface 13a of the rotor 13. The steam turbine (high-pressure turbine 4) includes a plurality of first-stage stator vanes 19A that are arranged at intervals in the circumferential direction of the rotor 13 and have airfoil portions 191 and inner shrouds 193 that are located radially inward of the airfoil portions 191. The steam turbine (high-pressure turbine 4) includes a blade ring (forward stage blade ring 45) that is separable from the inner casing (inner casing region 435) and holds at least a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4) includes a second annular portion 200 attached to an inner shroud 193 of a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4) includes a second sealing device (sealing device 52) provided between a first annular portion 431 and the second annular portion 200. A method of assembling a steam turbine (high-pressure turbine 4) according to at least one embodiment of the present disclosure includes a first step S11 of attaching a second lower half (forward stage blade ring lower half 45L) of a blade ring (forward stage blade ring 45) to a first lower half (annular body lower half 43L) of an inner casing (inner casing region 435) integrally molded with the first annular portion 431, the blade ring having at least a plurality of first-stage stator vanes 19A attached thereto and the second annular portion 200 attached to the inner shroud 193. A method of assembling a steam turbine (high-pressure turbine 4) according to at least one embodiment of the present disclosure includes, after performing a first step S11, a second step S12 of attaching a rotor 13 to the first lower half (annular body lower half 43L) and the second lower half (forward stage blade ring lower half 45L). A method of assembling a steam turbine (high-pressure turbine 4) according to at least one embodiment of the present disclosure includes, after performing a first step S12, a third step S13 of attaching a second upper half (forward stage blade ring upper half 45U) of a blade ring (forward stage blade ring 45) having at least a plurality of first-stage stator vanes 19A attached to the second lower half (forward stage blade ring lower half 45L) and having a second annular portion 200 attached to an inner shroud 193.A method for assembling a steam turbine (high-pressure turbine 4) according to at least one embodiment of the present disclosure includes, after performing the third step S13, a fourth step S14 of attaching a first upper half (annular body upper half 43U) of an inner casing (inner casing region 435) molded integrally with the first annular portion 431 to the first lower half (annular body lower half 43L).

[0128] According to the method (14) above, the steam turbine (high-pressure turbine 4) can be easily assembled.

[0129] (15) In a method of assembling a steam turbine (high-pressure turbine 4C) according to at least one embodiment of the present disclosure, the steam turbine (high-pressure turbine 4C) includes an inner casing (inner casing 435C). The steam turbine (high-pressure turbine 4C) includes a first annular portion 431C formed integrally with the inner casing (inner casing 435C), defining at least a portion of the steam inlet flow path 75, and holding a first sealing device (sealing device 51) disposed on an outer circumferential surface 13a of the rotor 13. The steam turbine (high-pressure turbine 4C) includes a plurality of first-stage stator vanes 19A arranged at intervals in the circumferential direction of the rotor 13, and having airfoil portions 191 and an inner shroud 193 positioned radially inward of the airfoil portions 191. The steam turbine (high-pressure turbine 4C) includes a blade ring (stator vane holding region 433C) formed integrally with the inner casing (inner casing 435C) and holding at least a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4C) includes a second annular portion 200 attached to an inner shroud 193 of a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4C) includes a second sealing device (sealing device 52) provided between the first annular portion 431C and the second annular portion 200. A method of assembling a steam turbine (high-pressure turbine 4C) according to at least one embodiment of the present disclosure includes a first step S21 of attaching a rotor 13 to a blade ring (vane retaining region 433C) to which at least a plurality of first-stage stator vanes 19A are attached and to which the second annular portion 200 is attached to the inner shroud 193, and to a lower half (annular body lower half portion 43L) of an inner casing (inner casing 435C) molded integrally with the first annular portion 431C. A method of assembling a steam turbine (high-pressure turbine 4C) according to at least one embodiment of the present disclosure includes a second step S22 of attaching, after performing the first step S21, a blade ring (vane holding region 433C) having at least a plurality of first-stage stator vanes 19A attached to its lower half (annular body lower half 43L) and having a second annular portion 200 attached to the inner shroud 193, and an upper half (inner casing upper half 435CU) of an inner casing (inner casing 435C) molded integrally with the first annular portion 431C.

[0130] According to the method (15) above, the steam turbine (high-pressure turbine 4C) can be easily assembled.

[0131] (16) In a method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure, the steam turbine (high-pressure turbine 4A) includes an inner casing 435A. The steam turbine (high-pressure turbine 4A) includes a first annular portion 431A that is separable from the inner casing 435A, defines at least a portion of the steam inlet flow path 75, and holds a first sealing device (sealing device 51) that is disposed on an outer circumferential surface 13a of the rotor 13. The steam turbine (high-pressure turbine 4A) includes a plurality of first-stage stator vanes 19A that are arranged at intervals in the circumferential direction of the rotor 13 and have airfoil portions 191 and an inner shroud 193 that is positioned radially inward of the airfoil portions 191. The steam turbine (high-pressure turbine 4A) includes a blade ring 433A that is separable from the inner casing 435A and the first annular portion 431A, and holds at least a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4A) includes a second annular portion 200 attached to an inner shroud 193 of a plurality of first-stage stator vanes 19A. The steam turbine (high-pressure turbine 4A) includes a second sealing device (sealing device 52) provided between the first annular portion 431A and the second annular portion 200. A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes a first step S31 of attaching a second lower half (the lower half of the blade ring 433A) of a blade ring 433A, in which at least a plurality of first-stage stator vanes 19A are attached to a first lower half (the lower half of the inner casing 435A) of an inner casing 435A, and the second annular portion 200 is attached to the inner shroud 193. A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes, after performing a first step S31, a second step S32 of attaching a third lower half (the lower half of the first annular portion 431A) of the first annular portion 431A to the first lower half (the lower half of the inner casing 435A) and the second lower half (the lower half of the blade ring 433A). A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes, after performing a second step S32, a third step S33 of attaching the rotor 13 to the first lower half (the lower half of the inner casing 435A), the second lower half (the lower half of the blade ring 433A), and the third lower half (the lower half of the first annular portion 431A).A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes, after performing the third step S33, a fourth step S34 of attaching a third upper half (first annular portion upper half 431AU) of the first annular portion 431A to the third lower half (lower half of the first annular portion 431A). A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes, after performing the fourth step S34, a fifth step S35 of attaching a second upper half (blade ring upper half 433AU) of the blade ring 433A, the blade ring 433A having at least a plurality of first-stage stator vanes 19A attached to the second lower half (lower half of the blade ring 433A) and the second annular portion 200 attached to the inner shroud 193. A method of assembling a steam turbine (high-pressure turbine 4A) according to at least one embodiment of the present disclosure includes a sixth step S36 of attaching the first upper half (inner casing upper half 435AU) of the inner casing 435A to the first lower half (lower half of the inner casing 435A) after performing the fifth step S35.

[0132] According to the method (16) above, the steam turbine (high-pressure turbine 4A) can be easily assembled.

[0133] REFERENCE SIGNS LIST 1 Steam turbine equipment 2 Boiler 4, 4A, 4B, 4C High-pressure turbine 13 Rotor 13a Outer peripheral surface 18 Rotor blade 19 Stator vane 19A First stage stator vane 43 Annular body 43L Annular body lower half 43U Annular body upper half 45 Forward stage blade ring 45L Forward stage blade ring lower half 45U Forward stage blade ring upper half 51, 52 Sealing device 75 Steam inlet flow passage 191 Airfoil portion 192 Outer shroud 193 Inner shroud 200 Second annular portion 205 Flow passage forming region 207 Axial second opposing portion 209 Opposing surface 431, 431A, 431B, 431C First annular portion 431AU First annular portion upper half 433 Blade ring 433AU Blade ring upper half 435 Inner compartment area 435A, B, C Inner compartment 435AU Inner compartment upper half 441 Radial first opposing part 443 Axial first opposing part

Claims

1. A steam turbine comprising: an inner casing; a first annular portion coupled to or formed integrally with the inner casing, defining at least a portion of a steam inlet passage, and holding a first sealing device arranged on an outer peripheral surface of a rotor; a plurality of first stage stator vanes arranged at intervals around the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring coupled to or formed integrally with the inner casing, holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second sealing device provided between the first annular portion and the second annular portion.

2. A steam turbine as described in claim 1, wherein the second annular portion has a passage forming region that defines a part of the steam inlet passage downstream in the axial direction of the rotor from the region defined by the first annular portion.

3. A steam turbine as described in claim 1 or 2, wherein the first annular portion has a radial first opposing portion that faces the second annular portion in the radial direction of the rotor, radially inward of the rotor than the blade ring, the second annular portion has a radial second opposing portion that faces the radial first opposing portion in the radial direction, and the second seal device seals a gap between the radial first opposing portion and the radial second opposing portion.

4. The steam turbine according to claim 3, wherein the first radially opposed portion and the second radially opposed portion are located upstream of the inner shroud in the axial direction.

5. A steam turbine as described in claim 4, wherein the second annular portion has an opposing surface that faces an outer peripheral surface of the rotor in the radial direction, and the first radial opposing portion and the second radial opposing portion are located radially outward of the rotor than the opposing surfaces.

6. The steam turbine according to claim 3, wherein the radially second opposing portion is located radially inward of the rotor relative to the radially first opposing portion.

7. The steam turbine according to claim 3, wherein the radially second opposing portion is located radially outward of the rotor relative to the radially first opposing portion.

8. A steam turbine as described in claim 1 or 2, wherein the first annular portion has a first axial opposing portion that faces the second annular portion in the axial direction of the rotor, and the second annular portion has a second axial opposing portion that faces the first axial opposing portion while being spaced apart in the axial direction.

9. A steam turbine as described in claim 1 or 2, wherein the second annular portion has a protrusion that protrudes radially outward from the rotor and extends in the circumferential direction, the inner shroud has a recess that can engage with the protrusion, and when the protrusion and the recess engage with each other, the second annular portion restricts radial and axial movement of the rotor relative to the inner shroud.

10. The steam turbine according to claim 1 or 2, wherein the first annular portion is formed integrally with the inner casing.

11. The steam turbine according to claim 10, wherein the blade ring is a separate member from the inner casing and is connected to the inner casing.

12. The steam turbine according to claim 10, wherein the blade ring is integrally formed with the inner casing.

13. A steam turbine as described in claim 1 or 2, wherein the first annular portion is a separate member from the inner casing and is connected to the inner casing, and the blade ring is a separate member from the inner casing and is connected to the inner casing.

14. A method for assembling a steam turbine, comprising: an inner casing; a first annular portion formed integrally with the inner casing, defining at least a portion of a steam inlet flow passage, and holding a first seal device arranged on an outer circumferential surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring separable from the inner casing and holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second seal device provided between the first annular portion and the second annular portion, the method comprising the steps of: a first step of attaching a second lower half of the blade ring, to a first lower half of the inner casing molded integrally with the first annular portion, the blade ring having at least the plurality of first stage stator vanes attached thereto, and the second annular portion attached to the inner shroud; a second step of attaching the rotor to the first lower half and the second lower half after the first step is performed; a third step of attaching a second upper half of the blade ring, having at least the plurality of first stage stator vanes attached to the second lower half and the second annular portion attached to the inner shroud, to the second lower half after the second step is performed; and a fourth step of attaching a first upper half of the inner casing molded integrally with the first annular portion to the first lower half after the third step is performed.

15. A method for assembling a steam turbine, comprising: an inner casing; a first annular portion formed integrally with the inner casing, defining at least a portion of a steam inlet passage, and holding a first seal device arranged on an outer circumferential surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring formed integrally with the inner casing and holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second seal device provided between the first annular portion and the second annular portion, the method comprising the steps of: a first step of attaching the rotor to the blade ring to which at least the plurality of first stage stator vanes are attached and to which the second annular portion is attached to the inner shroud, and to a lower half of the inner casing molded integrally with the first annular portion; a second step of attaching, after carrying out the first step, the blade ring having at least the plurality of first stage vanes attached to the lower half and the second annular portion attached to the inner shroud, and an upper half of the inner casing molded integrally with the first annular portion.

16. A method for assembling a steam turbine, comprising: an inner casing; a first annular portion separable from the inner casing, defining at least a portion of a steam inlet passage, and holding a first seal device disposed on an outer circumferential surface of a rotor; a plurality of first stage stator vanes arranged at intervals in the circumferential direction of the rotor, each having an airfoil portion and an inner shroud positioned radially inward of the airfoil portion; a blade ring separable from the inner casing and the first annular portion, holding at least the plurality of first stage stator vanes; a second annular portion attached to the inner shroud of the plurality of first stage stator vanes; and a second seal device provided between the first annular portion and the second annular portion, the method comprising the steps of: a first step of attaching a second lower half of the blade ring, to a first lower half of the inner casing, the blade ring having at least the plurality of first stage stator vanes attached thereto, and the second annular portion attached to the inner shroud; a second step of attaching a third lower half of the first annular portion to the first lower half and the second lower half after performing the first step; a third step of attaching the rotor to the first lower half, the second lower half, and the third lower half after performing the second step; a fourth step of attaching the third upper half of the first annular portion to the third lower half after performing the third step; a fifth step of attaching a second upper half of the blade ring, having at least the plurality of first stage vanes attached to the second lower half and the second annular portion attached to the inner shroud, to the second lower half after performing the fourth step; and a sixth step of attaching a first upper half of the inner casing to the first lower half after performing the fifth step.

Images