Steam turbine and method for modifying steam turbine

Abstract

A steam turbine according to at least one embodiment of the present disclosure comprises: a rotor; an outer casing; an inner casing that houses the rotor, is accommodated in the outer casing, and supported by a support part of the outer casing such that movement in the axial direction of the rotor relative to the outer casing is restricted; and a partition member that is an annular member disposed between the outer casing and the inner casing at a position different from the support part in the axial direction, fixed to the outer casing, and extending in the circumferential direction of the rotor, has a first opposing part facing the inner casing in the radial direction of the rotor while allowing movement relative to the inner casing in the axial direction, and partitions a space between the outer casing and the inner casing into one side and the other side in the axial direction of the rotor.

Description

Steam turbine and method for modifying a steam turbine

[0001] This application claims priority to Japanese Patent Application No. 2024-008747, filed with the Japan Patent Office on January 24, 2024, the contents of which are incorporated herein by reference.

[0002] For example, in industrial steam turbines for power plants, the inner casing is supported on the outer casing by having portions that protrude radially outward from the inner casing supported inside the outer casing at multiple locations with different axial positions (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2001-193414

[0004] For example, in the steam turbine described in Patent Document 1, the most axially downstream portion of the portions protruding radially outward from the inner casing also serves as a partition wall separating the space between the outer casing and the inner casing from the steam exhaust section. Therefore, this partition wall receives a thrust force acting axially downstream due to a pressure difference between the space between the outer casing and the inner casing and the steam exhaust section, resulting in a thrust force acting axially downstream on the inner casing. Furthermore, the inner casing may also be subjected to a thrust force acting axially downstream from steam passing through the stator vane stage, or, depending on design conditions, may also be subjected to a thrust force acting axially upstream. Because of this axial thrust force acting on the inner casing, a support portion in the outer casing must have sufficient strength to support the inner casing while restricting axial movement of the inner casing relative to the outer casing. Therefore, the support portion tends to be large in size.

[0005] Furthermore, if the load on the support portion increases due to changes in the internal structure of an existing steam turbine, the strength of the support portion may become insufficient.

[0006] In consideration of the above circumstances, at least one embodiment of the present disclosure has an object to reduce a load on a support portion of an outer casing that supports an inner casing in a steam turbine.

[0007] (1) A steam turbine according to at least one embodiment of the present disclosure comprises: a rotor; an outer casing; an inner casing that houses the rotor, is housed in the outer casing, and is supported by a support portion of the outer casing so that axial movement of the rotor relative to the outer casing is restricted; and a partition member that is an annular member that is arranged between the outer casing and the inner casing at different positions in the axial direction and is fixed to the outer casing, extending in the circumferential direction of the rotor, has a first opposing portion that faces the inner casing in the radial direction of the rotor while allowing relative movement with the inner casing in the axial direction, and divides the space between the outer casing and the inner casing into one side and the other side in the axial direction of the rotor.

[0008] (2) A method for modifying a steam turbine according to at least one embodiment of the present disclosure is a method for modifying a steam turbine, comprising: a step of installing an inner casing in an outer casing of an existing steam turbine; and a step of fixing a partition member, which is an annular member extending in a circumferential direction of a rotor and divides a space between the outer casing and the inner casing into one side and the other side in the axial direction of the rotor, to the outer casing so as to be positioned between the outer casing and the inner casing, wherein in the step of fixing the partition member to the outer casing, a first opposing portion of the partition member is fixed to the outer casing so as to face the inner casing in the radial direction of the rotor while allowing relative movement with the inner casing in the axial direction.

[0009] According to at least one embodiment of the present disclosure, it is possible to reduce the load on a support portion of an outer casing that supports an inner casing in a steam turbine.

[0010] Fig. 2 is a system schematic diagram of a combined cycle power plant including a steam turbine according to an embodiment; Fig. 3 is a cross-sectional view showing an outline of the structure of an intermediate-pressure turbine according to an embodiment; Fig. 4 is a cross-sectional view of the vicinity of a support part of an outer casing; Fig. 5 is an enlarged view of part A in Fig. 2; Fig. 6 is a diagram for explaining the flow of steam flowing from a steam flow path into a communication hole; Fig. 7 is a flowchart showing the steps of a method for modifying a steam turbine according to some embodiments;

[0011] 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.

[0012] FIG. 1 is a system schematic diagram of a combined cycle power plant (hereinafter referred to as a power plant) equipped with a steam turbine according to one embodiment. The power plant 1 has, as main equipment, a heat recovery steam generator 2, a steam turbine 3, a compost helium condenser 11, a generator 12, and a gas turbine (not shown). The steam turbine 3 includes a high-pressure turbine 4, an intermediate-pressure turbine 8, and a low-pressure turbine 10. 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. The power plant 1 may be a single-shaft type in which the gas turbine and the steam turbine 3 share a common rotating shaft, or a multi-shaft type in which the gas turbine and the steam turbine 3 have independent rotating shafts. Note that FIG. 1 shows a single-shaft power plant 1.

[0013] Exhaust gas discharged from the turbine of the gas turbine is introduced into the heat recovery steam generator 2, where it is used as a heat source for generating steam and then discharged. Superheated steam generated in the heat recovery steam generator 2 is introduced into the inlet of the high-pressure turbine 4. Exhaust steam discharged after driving the high-pressure turbine 4 is introduced from the high-pressure turbine 4 to a reheater (not shown) of the heat recovery steam generator 2 and reheated. The reheated steam heated in the reheater is introduced into the intermediate-pressure turbine 8, drives the intermediate-pressure turbine 8, and then flows down the main steam pipe 9 to the low-pressure turbine 10. Exhaust steam discharged after driving the low-pressure turbine 10 is introduced into the condenser 11, where it is cooled and condensed, and then reintroduced into the heat recovery steam generator 2 as feedwater. As described above, the high-pressure turbine 4, the intermediate-pressure turbine 8, and the low-pressure turbine 10 are connected by the rotor 13, and rotational power is transmitted to the generator 12 via the rotor 13, where the rotational power is converted into electric power by the generator 12.

[0014] FIG. 2 is a cross-sectional view showing an outline of the structure of the intermediate-pressure turbine 8 of the steam turbine 3 according to an embodiment of the present disclosure, and mainly shows the upper half of the intermediate-pressure turbine 8. FIG. 3 is a cross-sectional view of the vicinity of the support portion 410 of the outer casing 41, and is a view of a portion of the outer casing lower half 41L and the inner casing lower half 43L as viewed from above. FIG. 4 is an enlarged view of portion A in FIG. 2. As shown in FIG. 2, the intermediate-pressure turbine 8 according to some embodiments includes an outer casing 41, an inner casing 43, and a forward stage blade ring 45. The configuration of the intermediate-pressure turbine 8 according to some embodiments will be described below, but the high-pressure turbine 4 may also have the configuration described below.

[0015] 2, in the intermediate-pressure turbine 8 according to some embodiments, the outer casing 41 is divided horizontally into an outer casing upper half 41U and an outer casing lower half 41L (see FIG. 3). In the following description, when there is no need to distinguish between the outer casing upper half 41U and the outer casing lower half 41L, they may be simply referred to as the outer casing 41.

[0016] As shown in Figure 2, in some embodiments of the intermediate-pressure turbine 8, multiple turbine stages are provided axially on the inner peripheral side of the outer casing 41, and a steam flow path 21 through which reheated steam flows is formed. The turbine stage is composed of a rotor blade row 18R in which multiple rotor blades 18 are arranged circumferentially around the rotor 13, and a stator blade row 19R in which multiple stator blades 19 are arranged circumferentially in an inner casing 43 or a forward stage blade ring 45, which will be described in detail later, facing the upstream side of the rotor blade row 18R. Note that when there is no particular distinction between the rotor blade row 18R and the stator blade row 19R or when the rotor blade row 18R and the stator blade row 19R are referred to collectively, they will be referred to as a blade row 17R. In the following description, the axial direction of the rotor 13, i.e., the direction in which the central axis AX of the rotor 13 extends, will also be simply referred to as the axial direction, and within the axial direction, the upstream side of the steam flow in the steam flow path 21 will be referred to as the axial upstream side, and the downstream side of the steam flow will be referred to as the axial downstream side. In the following description, the radial direction of the rotor 13 will also be simply referred to as the radial direction, and the circumferential direction of the rotor 13 will also be simply referred to as the circumferential direction.

[0017] In some embodiments, the intermediate-pressure turbine 8 is provided with an inlet nozzle 91 for supplying reheat steam and a steam exhaust section 92 for discharging exhaust steam discharged by driving the intermediate-pressure turbine 8 in the outer casing 41.

[0018] (Support Portion 410) As shown in Fig. 3, the outer casing lower half 41L is formed with support portions 410 that protrude horizontally from the inner circumferential surface 41i of the outer casing lower half 41L toward the radially inward direction. The support portions 410 are protrusions that protrude horizontally toward the radially inward direction from the inner circumferential surface 41i on one and the other horizontal sides of the rotor 13 near the horizontal dividing plane of the outer casing lower half 41L. As will be described later, the support portions 410 are configured to mainly bear thrust forces from the inner casing 43 toward the axial downstream side and to restrict relative axial movement between the outer casing 41 and the inner casing 43. The support portions 410 are provided at a position relatively upstream in the axial direction of the outer casing lower half 41L.

[0019] (Inner casing 43) In the intermediate-pressure turbine 8 shown in FIG. 2 , the inner casing 43 is a single member provided radially inward of the outer casing 41, and includes a seal area 431, a rear stage stator vane holding area 432, and an inner casing area 433. In the intermediate-pressure turbine 8 shown in FIG. 2 , the seal area 431 is provided axially upstream of the inlet cavity 71 to which steam is supplied from the inlet nozzle 91. In the intermediate-pressure turbine 8 shown in FIG. 2 , the seal area 431 is an area where a seal device 51 is disposed, which seals the gap between the outer peripheral surface 13 a of the rotor 13 and the inner casing 43. The seal device 51 is, for example, a labyrinth seal having seal fins. In the intermediate-pressure turbine 8 shown in FIG. 2 , the seal device 51 is also referred to as a second seal device 51 to distinguish it from a first seal device 30, which will be described later.

[0020]

[0023] In the intermediate-pressure turbine 8 shown in Fig. 2, the rear stage stator vane holding region 432 is a region that holds the rear stage stator vanes 19. In the intermediate-pressure turbine 8 shown in Fig. 2, the inner casing region 433 is a region that connects the seal region 431 and the rear stage stator vane holding region 432. That is, in the intermediate-pressure turbine 8 shown in Fig. 2, the inner casing 43 is integrally formed with the seal region 431 in which the second seal device 51 that seals the gap with the outer circumferential surface 13a of the rotor 13 is disposed, the rear stage stator vane holding region 432 that holds the rear stage stator vanes 19, and the inner casing region 433 that connects the seal region 431 and the rear stage stator vane holding region 432. In the intermediate-pressure turbine 8 shown in Fig. 2, the inner casing 43 corresponds to a dummy ring, a blade ring, and an inner casing in a conventional steam turbine, which are formed as a single member.

[0021] 2 , a recess 434 is provided in the inner peripheral portion 43i of the inner casing 43 between the seal region 431 and the rear stage stator vane holding region 432. A front stage blade ring 45, which will be described later, is arranged in an area downstream in the axial direction of the recess 434.

[0022] Within the recess 434, a region on the axially upstream side of the forward stage blade ring 45 forms an inlet cavity 71. The inlet cavity 71 is connected to an inlet nozzle 91. Reheated steam supplied from the inlet nozzle 91 to the inlet cavity 71 flows from the inlet cavity 71 toward the first stator vane 19A, which is the stator vane 19 of the most upstream stage, and flows into the steam flow path 21.

[0023] In the intermediate-pressure turbine 8 shown in Fig. 2, the inner casing 43 is divided by a horizontal dividing plane into an upper half 43U and a lower half 43L (see Fig. 3). The upper half 43U and the lower half 43L are connected by a plurality of connecting bolts (not shown). 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 inner casing 43.

[0024] (Fitting Portion 440) As shown in FIG. 3 , the inner casing lower half 43L is provided with a fitting portion 440 that fits with the support portion 410 of the outer casing lower half 41L. The fitting portion 440 has protrusions 441 that protrude horizontally radially outward from the outer peripheral surface 43o of the inner casing lower half 43L on one and the other horizontal sides of the rotor 13 near the horizontal dividing plane of the inner casing lower half 43L. The protrusions 441 are formed with grooves 443 that are horizontally recessed radially inward from their radially outer ends and extend vertically. When the support portions 410 of the outer casing lower half 41L are fitted into the grooves 443, the axially upstream and downstream wall portions of the grooves 443 face the axially opposite the support portions 410 of the outer casing lower half 41L. This restricts relative axial movement between the outer casing 41 and the inner casing 43.

[0025] (Communication Hole 435) In the intermediate-pressure turbine 8 shown in Fig. 2 , the inner casing 43 has a communication hole 435 that communicates the steam flow path 21 in the rear stage of the blade row 17R with the space S between the outer casing 41 and the inner casing 43. An opening end 435a of the communication hole 435 facing the space S between the outer casing 41 and the inner casing 43 faces a space Su, which is axially upstream of a partition member 47 described later, within the space S between the outer casing 41 and the inner casing 43. For example, in the intermediate-pressure turbine 8 shown in Fig. 2 , the opening end 435b of the communication hole 435 facing the steam flow path 21 is provided so as to face the steam flow path 21 between, for example, the stator vane row 19RL of the final stage of the turbine stages and the rotor blade row 18R that faces the stator vane row 19RL of the final stage on the axial upstream side. A plurality of communication holes 435 are provided at intervals in the circumferential direction. 2 , for example, a plurality of communication holes 435 are provided at intervals in the circumferential direction in each of the inner casing upper half 43U and the inner casing lower half 43L. The communication holes 435 may have a shape such as a round hole or a rectangular hole when viewed from the extending direction of the communication holes 435, or may have a slit-like shape. This allows steam with a relatively reduced temperature flowing through the steam flow path 21 in the rear stage of the blade row 17R to be guided to the upstream space Su, thereby cooling the wall portion 41w of the outer casing 41 whose inner circumferential surface 41i faces the space Su.

[0026] (Second opposing portion 436) In the intermediate-pressure turbine 8 shown in FIG. 2 , the inner casing 43 has a second opposing portion 436 that radially opposes a first opposing portion 471 of the partition member 47, which will be described later. The second opposing portion 436 is provided in a region of the inner casing 43 that is relatively downstream in the axial direction. In the intermediate-pressure turbine 8 shown in FIG. 2 , the second opposing portion 436 is provided on an annular protruding portion 437 that protrudes radially outward from the outer peripheral surface 43o of the inner casing 43 and extends in the circumferential direction. That is, in the intermediate-pressure turbine 8 shown in FIG. 2 , the annular protruding portion 437 has the second opposing portion 436 that extends in the circumferential direction at its radially outer end. Note that it is not essential to provide the annular protruding portion 437 on the inner casing 43. If the inner casing 43 does not have an annular protruding portion 437, the second opposing portion 436 is provided on the outer peripheral surface 43o of the inner casing 43. The second opposing portion 436 will be described in detail later together with the first seal device 30 described below.

[0027] (Partition member 47) The intermediate-pressure turbine 8 shown in Figure 2 includes a partition member 47, which is an annular member that is disposed between the outer casing 41 and the inner casing 43 at a position axially different from the support portion 410 (see Figure 3) of the outer casing lower half portion 41L, is fixed to the outer casing 41, and extends in the circumferential direction. The partition member 47 divides the space S between the outer casing 41 and the inner casing 43 into one side (space Su) and the other side (space Sd) in the axial direction. In the intermediate-pressure turbine 8 shown in Figure 2, the inner casing 43 is provided with an annular protruding portion 437, and therefore the partition member 47, together with the annular protruding portion 437, divides the space S between the outer casing 41 and the inner casing 43 into one side (space Su) and the other side (space Sd) in the axial direction. The partition member 47 has a first opposing portion 471 (see FIG. 4 ) that faces the inner casing 43 in the radial direction while allowing relative movement with respect to the inner casing 43 in the axial direction.

[0028] The partition member 47 is, for example, a plurality of partially annular members divided in the circumferential direction. As shown in Fig. 2, a radially outer end portion 47o of each of the plurality of partition members 47 is attached and fixed to the mounting portion 41a of the outer casing 41. As will be described later, in the case where the intermediate-pressure turbine 8 shown in Fig. 2 is obtained by modifying an existing intermediate-pressure turbine 8, each of the plurality of partition members 47 may be attached and fixed to the mounting portion 41a of the outer casing 41 originally provided on the existing intermediate-pressure turbine 8.

[0029] (Forward Stage Blade Ring 45) In the high-pressure turbine 4 shown in FIG. 2 , the forward stage blade ring 45 is a member separate from the inner casing 43, and is attached to the inner casing 43 in an area downstream of the recess 434 in the axial direction, to hold the stator vanes 19 of the forward stage.

[0030] The forward stage blade ring 45 holds the stator vanes 19 of multiple stages, including the first stator vane 19A, which is the stator vane 19 of the most upstream stage.

[0031] 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 (not shown). 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, they may be simply referred to as the forward stage blade ring 45.

[0032] (First sealing device 30) The intermediate-pressure turbine 8 shown in FIG. 2 includes a first sealing device 30 that is disposed between the first opposing portion 471 and the second opposing portion 436 and seals the gap between the first opposing portion 471 and the second opposing portion 436. The first sealing device 30 may include at least two types of sealing devices that are different in structure. The intermediate-pressure turbine 8 shown in FIG. 2 includes two types of sealing devices that are different in structure. The at least two types of sealing devices may be disposed at different positions in the axial direction. In the following description, of the two types of sealing devices that are different in structure for the first sealing device 30 as shown in FIG. 4, the sealing device on the upstream side in the axial direction will be referred to as the upstream first sealing device 31, and the sealing device on the downstream side in the axial direction will be referred to as the downstream first sealing device 32.

[0033] (Upstream-Side First Sealing Device 31) As shown in FIG. 4 , in the intermediate-pressure turbine 8, the upstream-side first sealing device 31 includes a first sealing member 311 and a first biasing member 316. The first sealing member 311 is a member having a partial ring shape extending in the circumferential direction, and its radially inner circumferential surface has a curved surface 312 that is convex radially inward when viewed from the circumferential direction. A plurality of first sealing members 311 are provided in the circumferential direction. The first biasing member 316 is, for example, a spring, provided radially outward of the first sealing member 311 and configured to bias the first sealing member 311 radially inward. In the upstream-side first sealing device 31 having such a configuration, the curved surface 312 contacts an upstream outer peripheral surface 436u, which is the radially outer surface of the second opposing portion 436, while allowing relative axial movement with the second opposing portion 436, thereby sealing a gap between the curved surface 312 and the upstream outer peripheral surface 436u. In addition, since the first sealing member 311 of the upstream first sealing device 31 is biased radially inward by the first biasing member 316, the gap between the curved surface 312 and the upstream outer peripheral surface 436u is sealed while allowing relative radial movement between the first opposing portion 471 and the second opposing portion 436.

[0034] (Downstream-Side First Seal Device 32) As shown in FIG. 4 , in the intermediate-pressure turbine 8, the downstream-side first seal device 32 includes a second seal member 321 and a second biasing member 326. The second seal member 321 is a member having a partial ring shape extending in the circumferential direction, and a plurality of circumferentially extending seal fins 322 are formed at intervals in the axial direction, protruding radially inward from a radially inner inner circumferential surface 321i. The second biasing member 326 is, for example, a spring, provided radially outward of the second seal member 321 and configured to bias the second seal member 321 radially inward. The seal fin 322 faces a downstream outer peripheral surface 436d, which is the radially outer surface of the second opposing portion 436, at its radially inner tip end, while allowing relative axial movement with the second opposing portion 463.

[0035] The second opposing portions 436 have a plurality of ridges 438 formed at axially offset positions from the seal fins 322 and spaced apart in the axial direction. The ridges 438 protrude radially outward from the downstream outer peripheral surface 436d and extend circumferentially. The ridges 438 contact the inner peripheral surface 321i of the second seal member 321 while allowing relative axial movement with the second seal member 321. Furthermore, because the second seal member 321 is biased radially inward by the second biasing member 326, the downstream first seal device 32 seals the gap between the inner peripheral surface 321i of the second seal member 321 and the downstream outer peripheral surface 436d while allowing relative radial movement between the first opposing portions 471 and the second opposing portions 436.

[0036] In the downstream first sealing device 32 having such a configuration, the gap between the radially inner tip of the sealing fin 322 and the downstream outer peripheral surface 436d of the second opposing portion 436 is sealed, and the gap between the radially outer end of the protrusion 438 of the second opposing portion 436 and the inner peripheral surface 321i of the second sealing member 321 is sealed.

[0037] (Discharge piping 81) The intermediate-pressure turbine 8 shown in FIG. 2 includes a discharge piping 81 for discharging steam, which has flowed into the upstream space Su through the communication hole 435, to a space Sd downstream of the partition member 47 in the axial direction. The space Sd downstream of the partition member 47 in the axial direction is a space that communicates with the space in the steam exhaust section 92. In the intermediate-pressure turbine 8 shown in FIG. 2, the discharge piping 81 is entirely disposed in the space S between the outer casing 41 and the inner casing 43. At least a portion of the discharge piping 81 may be located in a region radially outside the outer casing 41. A plurality of discharge pipings 81 are provided at intervals in the circumferential direction. In the intermediate-pressure turbine 8 shown in FIG. 2, for example, two discharge pipings 81 are provided in each of the inner casing upper half 43U and the inner casing lower half 43L at intervals in the circumferential direction.

[0038] An axially upstream end 81u of the discharge pipe 81 is connected to a cavity 73 formed in a seal region 431 of the inner casing 43. The cavity 73 is an empty space extending in the circumferential direction in the seal region 431 of the inner casing 43. The cavity 73 is separated from a space S between the outer casing 41 and the inner casing 43 by a second seal device 51 arranged between the space S and a space between the cavity 73 and the outer peripheral surface 13a of the rotor 13.

[0039] An axially downstream end 81d of the discharge pipe 81 is connected to the space Sd axially downstream of the partition member 47. In the intermediate-pressure turbine 8 shown in Fig. 2 , the axially downstream end 81d of the discharge pipe 81 axially penetrates the annular protruding portion 437 of the inner casing 43 and is connected to the space Sd axially downstream of the partition member 47. Note that the axially downstream end 81d of the discharge pipe 81 may also penetrate the partition member 47 in the axial direction and be connected to the space Sd axially downstream of the partition member 47.

[0040] 2 receives reheated steam heated by a reheater (not shown) of the heat recovery steam generator 2 from an inlet nozzle 91 into a steam flow path 21. The reheated steam supplied to the steam flow path 21 drives the intermediate-pressure turbine 8 by passing through the steam flow path 21, and is then discharged from a steam exhaust section 92 into the main steam pipe 9.

[0041] 5 is a diagram illustrating the flow of steam flowing from the steam flow path 21 into the communication hole 435. A portion of the steam with a relatively reduced temperature flowing through the steam flow path 21 in the rear stage of the blade row 17R flows into the communication hole 435 from an open end 435b of the communication hole 435 facing the steam flow path 21, as shown by arrow a in FIG. 5 , and then flows through the communication hole 435 into a space Su axially upstream of the partition member 47, as shown by arrow b. The steam with a relatively reduced temperature that has flowed into the space Su flows axially upstream within the space Su, as shown by arrow c, while cooling the outer casing 41 from the inside, then changes direction of flow radially inward as shown by arrow d, and flows into a cavity 73 formed in a seal region 431 of the inner casing 43 through a small gap between the second seal device 51 and the outer circumferential surface 13a of the rotor 13, as shown by arrow e.

[0042] The steam that has flowed into the cavity 73 flows from the cavity 73 into the discharge pipe 81 and flows in the discharge pipe 81 from the axially upstream end 81u to the axially downstream end 81d as shown by arrow f. The steam that has flowed in the discharge pipe 81 is discharged from the axially downstream end 81d to a space Sd downstream of the partition member 47 in the axial direction as shown by arrow g.

[0043] Furthermore, since the gap between the first opposing portion 471 and the second opposing portion 436 is sealed by the first sealing device 30, steam that flows into the space Su axially upstream of the partition member 47 from the communication hole 435 is prevented from leaking from the gap into the space Sd axially downstream of the partition member 47.

[0044] In the intermediate-pressure turbine 8 described above, by providing the partition member 47 having the first opposing portion 471, the second opposing portion 436, which is a portion of the inner casing 43 radially opposing the first opposing portion 471, can be positioned relatively radially inward. Therefore, when the space S between the inner casing 43 and the outer casing 41 is partitioned into a space on one side (e.g., space Su) and a space on the other side (e.g., space Sd) in the axial direction by the portion (the second opposing portion 436) radially opposing the first opposing portion 471, the thrust force that the portion receives due to the pressure difference between the space on one side (e.g., space Su) and the space on the other side (e.g., space Sd) can be reduced. This reduces the thrust force acting on the inner casing 43, thereby reducing the load on the support portion 410 of the outer casing 41.

[0045] In the intermediate-pressure turbine 8 described above, the inner casing 43 has an annular protruding portion 437 that protrudes radially outward and extends circumferentially, and has a second opposing portion 436 that faces the first opposing portion 471 in the radial direction. This allows the first opposing portion 471 and the second opposing portion 436 to share the thrust force caused by the pressure difference between the space on one side (e.g., space Su) and the space on the other side (e.g., space Sd), thereby reducing the burden on the support portion 410 that fixes the first opposing portion 471 to the outer casing 41. This reduces the need to make the support portion 410 larger.

[0046] The above-mentioned intermediate-pressure turbine 8 is equipped with a first sealing device 30, so that the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436 due to the pressure difference between the space on one side (e.g., space Su) and the space on the other side (e.g., space Sd) can be reduced.

[0047] In the intermediate-pressure turbine 8 described above, the first sealing device 30 includes a first sealing member 311 and a second sealing member 321 as sealing members each having a partial ring shape extending in the circumferential direction, and a first biasing member 316 and a second biasing member 326 as biasing members that bias the sealing members (the first sealing member 311 and the second sealing member 321) radially inward. This allows relative movement in the radial direction between the first opposing portion 471 and the second opposing portion 436, thereby allowing relative movement in the radial direction between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal expansion in the radial direction between the outer casing 41 and the inner casing 43.

[0048] In the above-described intermediate-pressure turbine 8, the first sealing device 30 includes at least two types of sealing devices having different structures, namely, an upstream first sealing device 31 and a downstream first sealing device 32. The upstream first sealing device 31 and the downstream first sealing device 32 are arranged at different axial positions. This further reduces the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436 due to the pressure difference between the one space (e.g., space Su) and the other space (e.g., space Sd). Furthermore, according to the above-described intermediate-pressure turbine 8, by providing at least two types of sealing devices (the upstream first sealing device 31 and the downstream first sealing device 32) having different structures, even if a malfunction occurs in one sealing device, the other sealing devices can reduce the amount of steam leaking, thereby improving the reliability of the first sealing device 30. The axial positions of the upstream first sealing device 31 and the downstream first sealing device 32 may be interchanged. That is, a sealing device having a structure similar to the above-described upstream first sealing device 31 may be provided axially downstream of a sealing device having a structure similar to the above-described downstream first sealing device 32.

[0049] The intermediate-pressure turbine 8 described above is provided with the upstream first seal device 31, and relative movement in the axial and radial directions is permitted between the first opposing portion 471 and the second opposing portion 436, so relative movement in the axial and radial directions is permitted between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal elongation in the axial and radial directions between the outer casing 41 and the inner casing 43.

[0050] The intermediate-pressure turbine 8 described above is provided with the downstream first seal device 32, and relative movement in the axial and radial directions is permitted between the first opposing portion 471 and the second opposing portion 436, so relative movement in the axial and radial directions is permitted between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal elongation in the axial and radial directions between the outer casing 41 and the inner casing 43.

[0051] In the above-described intermediate-pressure turbine 8, the first seal member 311 and the second seal member 321 are disposed at different positions in the axial direction. As a result, by providing the first seal member 311 and the second seal member 321, which are two types of seal members with different structures, even if a malfunction occurs in one seal member, the other seal member can reduce the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436, thereby improving the reliability of the first seal device 30.

[0052] According to the above-mentioned intermediate pressure turbine 8, since it is equipped with an exhaust pipe 81, steam that flows into the upstream space Su through the communication hole 435 can be discharged to the space Sd downstream in the axial direction from the partition member 47.

[0053] In the above-described intermediate-pressure turbine 8, the discharge pipe 81 is arranged in the space S between the outer casing 41 and the inner casing 43, so there is no need to provide a through hole in the outer casing 41 to pass the discharge pipe 81 through, thereby reducing the cost of providing a through hole in the outer casing 41.

[0054] In the intermediate-pressure turbine 8 described above, the inner casing 43 is integrally formed with a seal region 431, a rear stage stator vane holding region 432, and an inner casing region 433. For example, in the case of a conventional steam turbine in which the seal region 431 and the inner casing region 433 are separate, a relatively large thrust force acts between the members constituting the seal region 431 and the members constituting the inner casing region 433, so it is necessary to ensure the strength of the fitting portion between these two members, and the size of the fitting portion becomes relatively large. Similarly, in the case of a conventional steam turbine in which the rear stage stator vane holding region 432 and the inner casing region 433 are separate, a relatively large thrust force acts between the members constituting the rear stage stator vane holding region 432 and the members constituting the inner casing region 433, so it is necessary to ensure the strength of the fitting portion between these two members, and the size of the fitting portion becomes relatively large. According to the above-described intermediate-pressure turbine 8, the seal area 431, the rear stage stator vane holding area 432, and the inner casing area 433 are formed in the inner casing 43, which is a single member. Therefore, compared to, for example, the conventional steam turbine described above, it is possible to reduce the size of the area between the inner casing area 433 and the seal area 431, and the size of the area between the inner casing area 433 and the rear stage stator vane holding area 432. This allows the intermediate-pressure turbine 8, which is a steam turbine according to some embodiments, to be downsized. In other words, according to the above-described intermediate-pressure turbine 8, it is possible to supply higher-pressure steam while maintaining a size equivalent to that of the outer casing of a conventional steam turbine.

[0055] (Method for modifying a steam turbine) A method for modifying a steam turbine will be described below. In the following description, a case will be described in which an existing intermediate-pressure turbine is modified into the intermediate-pressure turbine 8 according to some embodiments described above. FIG. 6 is a flowchart showing the steps of the method for modifying a steam turbine according to some embodiments. The method for modifying a steam turbine according to some embodiments includes step S10 of removing components housed in the outer casing 41, step S20 of installing the inner casing 43, and step S30 of fixing the partition member 47 to the outer casing.

[0056] (Step S10 of Removing Components Housed in Outer Casing 41) Step S10 of removing components housed in outer casing 41 is a step of removing components housed in outer casing 41 of an existing steam turbine. In step S10 of removing components housed in outer casing 41, of the components housed in outer casing 41 of the existing steam turbine, components that will not be reused, components that will be reused after repair or modification, components that need to be removed temporarily for modification, etc. are removed from the outer casing 41 of the existing steam turbine.

[0057] In some embodiments of the method for modifying a steam turbine, after performing step S10 of removing components housed in the outer casing 41, either step S20 of installing the inner casing 43 or step S30 of fixing the partition member 47 to the outer casing may be performed first.

[0058] (Step S20 of Installing the Inner Casing 43) Step S20 of installing the inner casing 43 is a step of installing the inner casing 43 in the outer casing 41 of an existing steam turbine (intermediate-pressure turbine 8). Step S20 of installing the inner casing 43 is a step of installing the above-mentioned inner casing 43 in the outer casing 41 after step S10 of removing components housed in the outer casing 41 has been performed. Note that, for example, when the above-mentioned exhaust piping 81 is to be disposed in its entirety in the space S between the outer casing 41 and the inner casing 43, it is preferable that the above-mentioned exhaust piping 81 be previously attached to the inner casing 43 that is installed in the outer casing 41 in step S20 of installing the inner casing 43.

[0059] In step S20 of installing the inner casing 43, when the inner casing lower half 43L is installed in the outer casing lower half 41L, the support portions 410 of the outer casing lower half 41L are fitted into the groove portions 443 of the fitting portions 440 of the inner casing lower half 43L. In the method for modifying a steam turbine according to some embodiments, the support portions 410 of the outer casing lower half 41L are the support portions 410 of the existing outer casing lower half 41L. In step S20 of installing the inner casing 43, after the inner casing lower half 43L is installed in the outer casing lower half 41L, a new rotor 13 is installed and then the inner casing upper half 43U is installed.

[0060] (Step S30 of fixing the partition member 47 to the outer casing) Step S30 of fixing the partition member 47 to the outer casing is a step of fixing the partition member 47 to the outer casing 41 so as to be disposed between the outer casing 41 and the inner casing 43. In step S30 of fixing the partition member 47 to the outer casing, the partition member 47 is fixed to the outer casing 41 so that the first opposing portion 471 of the partition member 47 faces the inner casing 43 in the radial direction while allowing relative movement with the inner casing 43 in the axial direction. In step S30 of fixing the partition member 47 to the outer casing, the radially outer end portion 47o of each of the multiple partition members 47 is attached to the mounting portion 41a of the outer casing 41. In the steam turbine modification method according to some embodiments, the mounting portion 41a of the outer casing 41 is the mounting portion 41a of the existing outer casing 41. In addition, in step S30 of fixing the partition member 47 to the outer casing, the first seal device 30 is positioned so that the first seal device 30 is located between the first opposing portion 471 and the second opposing portion 436.

[0061] According to some embodiments of the steam turbine retrofitting method, by providing a partition member 47 having a first opposing portion 471, the second opposing portion 436, which is a portion of the inner casing 43 radially opposing the first opposing portion 471, can be positioned relatively radially inward. Therefore, when the space S between the inner casing 43 and the outer casing 41 is partitioned into a space on one side (e.g., space Su) and a space on the other side (e.g., space Sd) in the axial direction by the portion (the second opposing portion 436) radially opposing the first opposing portion 471, the thrust force that the portion receives due to the pressure difference between the space on one side (e.g., space Su) and the space on the other side (e.g., space Sd) can be reduced. This reduces the thrust force acting on the inner casing 43, thereby reducing the load on the support portion 410 of the outer casing 41. Therefore, it is not necessary to reinforce the existing support portion 410 of the outer casing 41.

[0062] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0063] The contents described in each of the above embodiments can be understood, for example, as follows: (1) A steam turbine 3 (intermediate-pressure turbine 8) according to at least one embodiment of the present disclosure includes a rotor 13 and an outer casing 41. The steam turbine 3 (intermediate-pressure turbine 8) according to at least one embodiment of the present disclosure includes an inner casing 43 that houses the rotor 13, is housed in the outer casing 41, and is supported by a support portion 410 of the outer casing 41 so that axial movement of the rotor 13 relative to the outer casing 41 is restricted. The steam turbine 3 (intermediate-pressure turbine 8) according to at least one embodiment of the present disclosure is provided with a partition member 47 which is an annular member arranged between the outer casing 41 and the inner casing 43 at a different axial position from the support portion 410, fixed to the outer casing 41, extending in the circumferential direction of the rotor 13, has a first opposing portion 471 which faces the inner casing 43 in the radial direction of the rotor 13 while allowing relative movement with the inner casing 43 in the axial direction, and divides the space S between the outer casing 41 and the inner casing 43 into one side (space Su) and the other side (space Sd) in the axial direction of the rotor 13.

[0064] According to the configuration (1) described above, by providing the partition member 47 having the first opposing portion 471, the position of the portion (second opposing portion 436) of the inner casing 43 that faces the first opposing portion 471 in the radial direction can be set relatively radially inward. Therefore, when the space S between the inner casing 43 and the outer casing 41 is partitioned into a space (space Su) on one side in the axial direction and a space (space Sd) on the other side across the portion (second opposing portion 436) that faces the first opposing portion 471 in the radial direction, the thrust force that the portion receives due to the pressure difference between the space Su on the one side and the space Sd on the other side can be reduced. This reduces the thrust force acting on the inner casing 43, thereby reducing the load on the support portion 410 of the outer casing 41.

[0065] (2) In some embodiments, in the configuration of (1) above, the inner casing 43 may have an annular protruding portion 437 that protrudes radially outward and extends circumferentially, and has a second opposing portion 436 that radially opposes the first opposing portion 471.

[0066] According to the configuration (2) above, the thrust force received due to the pressure difference between the space on one side (space Su) and the space on the other side (space Sd) can be shared by the first opposing portion 471 and the second opposing portion 436, thereby reducing the burden on the support portion 410, which is a portion that fixes the first opposing portion 471 to the outer casing 41. Therefore, the need to make the support portion 410 larger can be reduced.

[0067] (3) In some embodiments, the configuration of (2) above may include a first sealing device 30 that is disposed between the first opposing portion 471 and the second opposing portion 436 and seals the gap between the first opposing portion 471 and the second opposing portion 436.

[0068] According to the configuration (3) above, the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436 can be reduced due to the pressure difference between the space on one side (space Su) and the space on the other side (space Sd).

[0069] (4) In some embodiments, in the configuration of (3) above, the first sealing device 30 may include sealing members (first sealing member 311, second sealing member 321) that are members having a partial ring shape extending circumferentially, and biasing members (first biasing member 316, second biasing member 326) that bias the sealing members (first sealing member 311, second sealing member 321) radially inward.

[0070] According to the configuration (4) above, relative radial movement between the first opposing portion 471 and the second opposing portion 436 is permitted, thereby permitting relative radial movement between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal expansion between the outer casing 41 and the inner casing 43 in the radial direction.

[0071] (5) In some embodiments, in the configuration of (3) or (4) above, the first seal device 30 may include at least two types of seal devices (the upstream first seal device 31 and the downstream first seal device 32) having different structures. The at least two types of seal devices (the upstream first seal device 31 and the downstream first seal device 32) may be arranged at different positions in the axial direction.

[0072] According to the configuration of (5) above, it is possible to further reduce the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436 due to the pressure difference between the space on one side (space Su) and the space on the other side (space Sd). Furthermore, according to the configuration of (5) above, by providing at least two types of sealing devices (the upstream first sealing device 31 and the downstream first sealing device 32) with different structures, even if a malfunction occurs in one sealing device, the amount of steam leaking as described above can be reduced by the other sealing device, thereby improving the reliability of the first sealing device 30.

[0073] (6) In some embodiments, in the configuration of (4) above, the seal member (first seal member 311) may be the first seal member 311 whose radially inner circumferential surface is a curved surface 312 that is convex radially inward when viewed from the circumferential direction. The curved surface 312 may contact the radially outer surface of the second opposing portion 436 while allowing relative axial movement with respect to the second opposing portion 436.

[0074] According to the configuration (6) above, relative movement in the axial direction and the radial direction is permitted between the first opposing portion 471 and the second opposing portion 436, and therefore relative movement in the axial direction and the radial direction is permitted between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal elongation in the axial direction and the radial direction between the outer casing 41 and the inner casing 43.

[0075] (7) In some embodiments, in the configuration described in (4) above, the seal member (second seal member 321) may include a plurality of circumferentially extending seal fins 322 that protrude radially inward from a radially inner inner circumferential surface 321i. The seal fins 322 may be arranged at their radially inner tips to face a radially outer surface (downstream outer circumferential surface 436d) of the second opposing portion 436 while allowing relative axial movement with the second opposing portion 436. The second opposing portion 436 may include a plurality of ridges 438 that protrude radially outward and extend circumferentially at positions offset from the seal fins 322 and spaced apart in the axial direction. The ridges 438 may contact the inner circumferential surface 321i of the second seal member 321 while allowing relative axial movement with the second opposing portion 321.

[0076] According to the configuration of (7) above, relative movement in the axial direction and the radial direction is permitted between the first opposing portion 471 and the second opposing portion 436, and therefore relative movement in the axial direction and the radial direction is permitted between the outer casing 41 and the inner casing 43. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal elongation in the axial direction and the radial direction between the outer casing 41 and the inner casing 43.

[0077] (8) In some embodiments, in the configuration described in (4) above, the seal members (first seal member 311, second seal member 321) may include: a first seal member 311 having a radially inner circumferential surface that is a curved surface 312 that is convex radially inward when viewed circumferentially; and a second seal member 321 having a plurality of circumferentially extending seal fins 322 that protrude radially inward from the radially inner circumferential surface 321i and are formed at intervals in the axial direction. The first seal member 311 and the second seal member 321 may be disposed at different positions in the axial direction. The curved surface 312 may contact a radially outer surface of the second opposing portion 436 while allowing relative axial movement with the second opposing portion 436. The seal fin 322 may face a radially outer surface (downstream outer peripheral surface 436d) of the second opposing portion 436 at its radially inner tip while allowing relative axial movement with the second opposing portion 436. The second opposing portion 436 may have a plurality of ridges 438 formed at intervals in the axial direction at positions axially offset from the seal fins 322, protruding radially outward and extending circumferentially. The ridges 438 may contact an inner circumferential surface 321i of the second seal member 321 while allowing relative axial movement with the second seal member 321.

[0078] According to the configuration (8) above, relative movement between the first opposing portion 471 and the second opposing portion 436 in the axial and radial directions is permitted, and therefore relative movement between the outer casing 41 and the inner casing 43 in the axial and radial directions is permitted. This makes it possible to reduce thermal stress acting on the outer casing 41 and the inner casing 43 even if there is a difference in thermal elongation between the outer casing 41 and the inner casing 43 in the axial and radial directions. Furthermore, according to the configuration (8) above, the first seal member 311 and the second seal member 321 can further reduce the amount of steam leaking through the gap between the first opposing portion 471 and the second opposing portion 436 due to the pressure difference between the space on one side (space Su) and the space on the other side (space Sd). Furthermore, according to the configuration (8) above, by providing two types of sealing members with different structures, the first sealing member 311 and the second sealing member 321, even if a malfunction occurs in one sealing member, the amount of steam leaking as described above can be reduced by the other sealing member, thereby improving the reliability of the first sealing device 30.

[0079] (9) In some embodiments, in any of the configurations (1) to (8) above, the inner casing 43 may have a communication hole 435 that communicates the steam flow path 21 in a rear stage of the blade row 17R with the space S between the outer casing 41 and the inner casing 43. An opening end 435a of the communication hole 435 facing the space S between the outer casing 41 and the inner casing 43 may face a space Su within the space S between the outer casing 41 and the inner casing 43 that is upstream of the partition member 47 in the axial direction.

[0080] According to the configuration (9) above, steam with a relatively low temperature flowing through the steam flow path 21 in the rear stage of the blade row 17R can be guided to the upstream space Su, thereby cooling the wall portion 41w of the outer casing 41 whose inner surface 41i faces the space Su.

[0081] (10) In some embodiments, in the configuration of (9) above, it is preferable to provide an exhaust pipe 81 for exhausting steam that has flowed into the upstream space Su through the communication hole 435 to the space Sd downstream in the axial direction of the partition member 47.

[0082] According to the configuration (10) above, the steam that has flowed into the upstream space Su via the communication hole 435 can be discharged to the space Sd downstream of the partition member 47 in the axial direction.

[0083] (11) In some embodiments, in the configuration of (10) above, the exhaust pipe 81 may be arranged in the space S between the outer casing 41 and the inner casing 43.

[0084] According to the configuration (11) above, it is not necessary to provide a through hole in the outer casing 41 for passing the exhaust pipe 81 therethrough, so the cost of providing a through hole in the outer casing 41 can be reduced.

[0085] (12) In some embodiments, in any of the configurations (1) to (11) above, the inner casing 43 may be integrally formed with a sealing area 431 in which a second sealing device 51 that seals the gap with the outer peripheral surface 13a of the rotor 13 is arranged, a rear stage stator vane holding area 432 that holds the rear stage stator vanes 19, and an inner casing area 433 that connects the sealing area 431 and the rear stage stator vane holding area 432.

[0086] For example, in the case of a conventional steam turbine in which the seal region 431 and the inner casing region 433 are separate, a relatively large thrust force acts between the members constituting the seal region 431 and the members constituting the inner casing region 433, so it is necessary to ensure the strength of the fitting portion between these two members, and the size of the fitting portion becomes relatively large. Similarly, in the case of a conventional steam turbine in which the rear stage stator vane holding region 432 and the inner casing region 433 are separate, a relatively large thrust force acts between the members constituting the rear stage stator vane holding region 432 and the members constituting the inner casing region 433, so it is necessary to ensure the strength of the fitting portion between these two members, and the size of the fitting portion becomes relatively large. According to the configuration of (12) above, the seal region 431, the rear stage stator vane holding region 432, and the inner casing region 433 are formed in the inner casing 43, which is a single member. Therefore, compared to, for example, the conventional steam turbine described above, it is possible to reduce the size of the region between the inner casing region 433 and the seal region 431 and the region between the inner casing region 433 and the rear stage stator vane holding region 432. This allows the steam turbine (intermediate-pressure turbine 8) according to some embodiments to be downsized. In other words, according to the configuration of (12) above, it is possible to supply higher-pressure steam while maintaining the same physical size as the outer casing of a conventional steam turbine.

[0087] (13) A method for modifying a steam turbine according to at least one embodiment of the present disclosure is a method for modifying a steam turbine, and includes: a step S20 of installing an inner casing 43 in an outer casing 41 of an existing steam turbine (intermediate-pressure turbine 8); and a step S30 of fixing a partition member 47, which is an annular member extending in the circumferential direction of the rotor 13 and partitions a space S between the outer casing 41 and the inner casing 43 into one side (space Su) and another side (space Sd) in the axial direction of the rotor 13, to the outer casing 41 so as to be disposed between the outer casing 41 and the inner casing 43. In the step S30 of fixing to the outer casing 41, the partition member 47 is fixed to the outer casing 41 so that a first opposing portion 471 of the partition member 47 faces the inner casing 43 in the radial direction of the rotor 13 while allowing relative movement with respect to the inner casing 43 in the axial direction.

[0088] According to the method (13), by providing the partition member 47 having the first opposing portion 471, the second opposing portion 436, which is a portion of the inner casing 43 radially opposing the first opposing portion 471, can be positioned relatively radially inward. Therefore, when the space S between the inner casing 43 and the outer casing 41 is partitioned into a space on one side (space Su) and a space on the other side (space Sd) in the axial direction by the portion (second opposing portion 436) radially opposing the first opposing portion 471, the thrust force that the portion receives due to the pressure difference between the space on one side (space Su) and the space on the other side (space Sd) can be reduced. This reduces the thrust force acting on the inner casing 43, thereby reducing the burden on the support portion 410 of the outer casing 41. Therefore, it is not necessary to reinforce the existing support portion 410 of the outer casing 41.

[0089] DESCRIPTION OF SYMBOLS 1 Combined cycle power plant (power plant) 2 Heat recovery steam generator 3 Steam turbine 4 High-pressure turbine 8 Intermediate-pressure turbine 10 Low-pressure turbine 13 Rotor 13a Outer peripheral surface 17R Blade row 19 Stator vane 19A First stator vane 19R Stator vane row 21 Steam flow path 30 First sealing device 31 Upstream-side first sealing device 32 Downstream-side first sealing device 41 Outer casing 41a Mounting portion 41i Inner peripheral surface 43 Inner casing 43i Inner peripheral portion 43o Outer peripheral surface 45 Forward stage blade ring 47 Partition member 51 Sealing device (second sealing device) 71 Inlet cavity 73 Cavity 81 Discharge piping 91 Inlet pipe stub 92 Steam exhaust portion 311 First sealing member 312 Curved surface 316 First biasing member 321 Second seal member 321i Inner peripheral surface 326 Second biasing member 410 Support portion 431 Sealing area 432 Rear stage stator vane holding area 433 Inner casing area 435 Communication hole 436 Second opposing portion 436d Downstream outer peripheral surface 436u Upstream outer peripheral surface 437 Annular protrusion 438 Ridge 440 Fitting portion 441 Protrusion 443 Groove portion 471 First opposing portion

Claims

1. A steam turbine comprising: a rotor; an outer casing; an inner casing that houses the rotor, is housed in the outer casing, and is supported by a support portion of the outer casing so that axial movement of the rotor with respect to the outer casing is restricted; and an annular member that is disposed between the outer casing and the inner casing at a position different from the support portion in the axial direction, is fixed to the outer casing, extends in the circumferential direction of the rotor, has a first opposing portion that faces the inner casing in the radial direction while allowing relative movement of the inner casing in the axial direction, and serves as a partition member that partitions the space between the outer casing and the inner casing into one side and the other side in the axial direction of the rotor.

2. The steam turbine according to claim 1, wherein the inner casing has an annular protruding portion that protrudes radially outward and extends in the circumferential direction, and has a second opposing portion that faces the first opposing portion in the radial direction.

3. The steam turbine according to claim 2, further comprising a first sealing device that is disposed between the first opposing portion and the second opposing portion and seals a gap between the first opposing portion and the second opposing portion.

4. The steam turbine according to claim 3, wherein the first sealing device includes a sealing member that is a member having a partially annular shape extending in the circumferential direction, and a biasing member that biases the sealing member radially inward.

5. The steam turbine according to claim 3 or 4, wherein the first sealing device includes at least two types of sealing devices having different structures, and the at least two types of sealing devices are disposed at different positions from each other in the axial direction.

6. The steam turbine according to claim 4, wherein the sealing member is a first sealing member having a curved surface whose inner peripheral surface on the radially inner side is convex radially inward when viewed from the circumferential direction, and the curved surface contacts the radially outer surface of the second opposing portion while allowing relative movement of the second opposing portion in the axial direction.

7. The seal member is a second seal member in which a plurality of seal fins protruding radially inward from the inner peripheral surface on the radially inner side and extending in the circumferential direction are formed at intervals in the axial direction. The seal fins face the radially outer surface and the radially inner tip of the second opposing portion while allowing relative movement in the axial direction with respect to the second opposing portion. The second opposing portion is formed in a plurality at intervals in the axial direction at a position shifted in the axial direction from the seal fins, has ridges protruding radially outward and extending in the circumferential direction, and the ridges come into contact with the inner peripheral surface of the second seal member while allowing relative movement in the axial direction with respect to the second seal member. The steam turbine according to claim 4.

8. The seal member includes a first seal member in which the inner peripheral surface on the radially inner side is a curved surface that is convex radially inward when viewed in the circumferential direction, and a second seal member in which a plurality of seal fins protruding radially inward from the inner peripheral surface on the radially inner side and extending in the circumferential direction are formed at intervals in the axial direction. The first seal member and the second seal member are arranged at different positions in the axial direction. The curved surface comes into contact with the radially outer surface of the second opposing portion while allowing relative movement in the axial direction with respect to the second opposing portion. The seal fins face the radially outer surface and the radially inner tip of the second opposing portion while allowing relative movement in the axial direction with respect to the second opposing portion. The second opposing portion is formed in a plurality at intervals in the axial direction at a position shifted in the axial direction from the seal fins, has ridges protruding radially outward and extending in the circumferential direction, and the ridges come into contact with the inner peripheral surface of the second seal member while allowing relative movement in the axial direction with respect to the second seal member. The steam turbine according to claim 4.

9. The inner casing has a communication hole that communicates a steam flow path in a rear stage of the blade row with a space between the outer casing and the inner casing. An opening end of the communication hole facing the space between the outer casing and the inner casing faces a space on the upstream side in the axial direction of the partition member within the space between the outer casing and the inner casing. The steam turbine according to any one of claims 1 to 4.

10. A steam turbine according to claim 9, further comprising a discharge pipe for discharging the steam that has flowed into the upstream space through the communication hole into the space on the downstream side of the partition member in the axial direction.

11. The steam turbine according to claim 10, wherein the discharge pipe is disposed in the space between the outer casing chamber and the inner casing chamber.

12. The steam turbine according to any one of claims 1 to 4, wherein the inner casing chamber is integrally formed with a seal region where a second sealing device for sealing a gap with the outer peripheral surface of the rotor is disposed, a rear-stage stator blade holding region for holding the rear-stage stator blades, and an inner casing chamber region connecting the seal region and the rear-stage stator blade holding region.

13. A method for retrofitting a steam turbine, comprising the steps of: installing an inner casing chamber in an outer casing chamber of an existing steam turbine; and fixing a partition member, which is an annular member extending in the circumferential direction of the rotor and partitions the space between the outer casing chamber and the inner casing chamber into one side and the other side in the axial direction of the rotor, to the outer casing chamber so as to be disposed between the outer casing chamber and the inner casing chamber. In the step of fixing to the outer casing chamber, the partition member is fixed to the outer casing chamber such that a first opposing portion of the partition member faces the inner casing chamber in the radial direction while allowing relative movement of the inner casing chamber in the axial direction.

Images