JP2013019285A - Steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine capable of sufficiently cooling a component by reliably introducing cooling steam to the component to be cooled.SOLUTION: This steam turbine 10 comprises: a casing 20; a stationary blade 23 arranged at an inner circumferential side of the casing 20; a turbine rotor 30 comprising a blade wheel obtained by forming a blade groove along a turbine rotor axial direction over a circumferential direction; and a moving blade 40 having a blade root part partially implanted in the blade groove. The moving blade 40 includes a protruding end formed at a portion of an edge surface at an upstream side of the blade root part and protruding upstream of an edge surface at an upstream side of the blade wheel. Cooling steam flowing into a trough-like cooling steam guide part 60 formed of the protruding end of each of the moving blades 40 adjacent in the circumferential direction and having both ends and a lower part opened is guided to a cooling steam flow path 50 formed between an outer circumferential edge surface of the blade wheel and the blade root part of each of the moving blades 40 adjacent in the circumferential direction.

Description

  Embodiments of the present invention relate to a steam turbine.

  From the viewpoint of improving the efficiency of steam turbines, steam turbines using mainstream steam having a temperature of about 600 ° C. are currently in practical use. In order to further improve the efficiency of the steam turbine, the temperature of the mainstream steam is considered to be about 700 to 750 ° C., and development is being promoted.

  In such a steam turbine, since the mainstream steam is high temperature, some components need to be made of a heat-resistant alloy. For example, in a part where a large stress is generated such as a blade implantation part, it is necessary to provide a cooling structure capable of cooling efficiently in addition to being made of a heat resistant alloy in order to improve durability. For this reason, techniques for efficiently cooling high-temperature components have been studied.

Japanese Patent Laid-Open No. 11-200801

  In a conventional steam turbine cooling structure having an axial insertion blade root type moving blade, the cooling steam is implanted between the inner ring of the diaphragm and the turbine rotor, and the shank portion of the moving blade and the moving blade. It passes through a cooling steam passage which is a groove formed between the leading end of the rotor disk and flows into the turbine stage in the downstream stage. At this time, a part of the cooling steam does not pass through the cooling steam passage and flows into the steam flow path through which the main steam flows.

  For example, if the pressure balance of the flow field through which the cooling steam flows changes, the flow rate of the cooling steam flowing into the cooling steam passage may be lower than the set flow rate, and the flow rate of the cooling steam flowing into the steam flow path may increase. is there. For this reason, the rotor blades and the turbine rotor cannot be sufficiently cooled, and the amount of cooling steam flowing into the steam channel increases, resulting in a decrease in turbine efficiency.

  The problem to be solved by the present invention is to provide a steam turbine capable of sufficiently cooling a component by reliably introducing cooling steam into the component to be cooled.

  The steam turbine according to the embodiment includes a casing, a plurality of stationary blades supported between a diaphragm outer ring and a diaphragm inner ring provided on the inner circumferential side of the casing along the circumferential direction, and the turbine rotor axial direction. A turbine rotor having an impeller formed by forming a plurality of blade grooves in the circumferential direction, a blade root portion and a blade effective portion in order along the blade height direction, each blade groove having a part of the blade root portion And a plurality of moving blades arranged alternately with the stationary blades in the axial direction of the turbine rotor. The moving blade includes a projecting end portion that is formed on at least a part of an upstream end surface of the blade root portion and projects upstream from an upstream end surface of the impeller.

  The protruding end portions of the rotor blades adjacent to each other in the circumferential direction form a bowl-shaped cooling steam guiding portion that is open at both ends and below. The cooling steam that has flowed into the cooling steam guide part enters a cooling steam flow path formed by a gap formed between the outer peripheral end face of the impeller and each blade root part of the moving blade adjacent in the circumferential direction. Be guided.

It is a figure which shows the cross section (meridian cross section) containing the central axis of a turbine rotor of the steam turbine of 1st Embodiment. It is a perspective view of the moving blade of the steam turbine of a 1st embodiment. It is a side view of the moving blade of the steam turbine of a 1st embodiment. It is a perspective view which shows the state by which the moving blade of the steam turbine of 1st Embodiment was implanted by the blade groove | channel. It is a top view when the state where the rotor blade of the steam turbine of a 1st embodiment is implanted in the blade slot is seen from the upstream of the turbine rotor axial direction. It is the figure which expanded a part of cross section (meridian cross section) including the central axis of the turbine rotor of the steam turbine of 1st Embodiment, and has shown the cross section equivalent to the AA cross section of FIG. In the steam turbine according to the first embodiment, the state in which the moving blades having different positions on the inner peripheral end surface of the protruding end portion of the adjacent moving blades are implanted in the blade groove is viewed from the upstream side in the turbine rotor axial direction. It is a top view at the time. It is a figure which shows the cross section (meridian cross section) containing the central axis of a turbine rotor of the steam turbine of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a cross section (meridian cross section) including a central axis of a turbine rotor 30 of the steam turbine 10 of the first embodiment. FIG. 2 is a perspective view of the moving blade 40 of the steam turbine 10 according to the first embodiment. FIG. 3 is a side view of the moving blade 40 of the steam turbine 10 according to the first embodiment. FIG. 4 is a perspective view showing a state in which the moving blade 40 of the steam turbine 10 according to the first embodiment is implanted in the blade groove.

  FIG. 5 is a plan view of the state in which the rotor blades 40 of the steam turbine 10 according to the first embodiment are implanted in the blade grooves when viewed from the upstream side in the turbine rotor axial direction. FIG. 6 is an enlarged view of a part of the cross section (meridian cross section) including the central axis of the turbine rotor 30 of the steam turbine 10 of the first embodiment, and corresponds to a cross section taken along the line AA of FIG. Is shown.

  In the following description, the same components are denoted by the same reference numerals, and redundant description is omitted or simplified. In the following, an intermediate pressure turbine will be described as an example of the steam turbine 10, but the configuration of the present embodiment is also applied to a high pressure turbine to which high-temperature and high-pressure steam is supplied, and also to an ultra-high pressure turbine. Can do.

  As shown in FIG. 1, the steam turbine 10 includes a casing 20, and a turbine rotor 30 is provided through the casing 20. The casing 20 may be a single-layer casing or a double-structure casing including an inner casing and an outer casing provided outside the casing.

  The rotor disk 31 of the turbine rotor 30 includes an impeller 33 configured by forming a plurality of blade grooves 32 along the turbine rotor axial direction in the circumferential direction (see FIGS. 4 and 5).

  A blade root 41 of the moving blade 40 is planted in the blade groove 32 between the blade wheels 33. For example, as shown in FIGS. 2 to 5, the moving blade 40 includes a blade root portion 41, a blade effective portion 42, and a shroud 43 in order along the blade height direction. The rotor blade 40 is a so-called axial insertion blade root type rotor blade that is inserted into the concave blade groove 32 of the impeller 33 in the axial direction of the turbine rotor 30.

  The blade root portion 41 includes an implanted portion 44 that is inserted into the blade groove 32 of the turbine rotor 30, and a shank portion 45 that is formed between the implanted portion 44 and the blade effective portion 42.

  The implantation portion 44 has a fitting uneven shape of an axial insertion blade root portion shape, and the uneven shape corresponds to the shape of the blade groove 32 of the turbine rotor 30. This fitting uneven shape prevents the moving blade 40 from coming off in the radial direction of the turbine rotor 30.

  Further, a projection (not shown) is provided at the downstream end of the impeller 33 so as to protrude to the blade groove 32 side and prevent the implanted portion 44 of the moving blade 40 from coming out downstream. Therefore, even when a downstream load is applied to the moving blade 40, the moving blade 40 does not escape from the blade groove 32.

  As shown in FIGS. 2 to 5, the moving blade 40 is located upstream of the upstream end surface 33 a of the impeller 33 when the moving blade 40 is implanted in a part of the upstream end surface of the blade root portion 41. A projecting end 46 projecting to the side is provided. The protruding end 46 is formed on at least a part of the implantation part 44 on the shank part 45 side and at least a part of the shank part 45. 2 to 5 show an example in which a protruding end portion 46 is provided on a part of the implantation portion 44 on the shank portion 45 side and the entire shank portion 45.

  Here, as shown in FIG. 5, in a state where the moving blade 40 is implanted in the blade groove 32, the outer peripheral end surface 33 b of the impeller 33 and each blade root portion 41 of the moving blade 40 adjacent in the circumferential direction. A gap portion penetrating in the turbine rotor axial direction is formed. This gap is a so-called balance groove and functions as a cooling steam flow path 50 for cooling steam.

  Further, the protruding end portions 46 of the rotor blades 40 adjacent to each other in the circumferential direction come into contact with each other, thereby forming a bowl-shaped cooling steam guiding portion 60 that is open at both ends in the turbine rotor axial direction and below. The cooling steam guiding unit 60 communicates with the cooling steam channel 50.

  Since the cooling steam guiding portion 60 is configured to protrude upstream from the upstream end face 33a of the impeller 33, for example, to guide the cooling steam flowing from the front or from the lower side to the cooling steam channel 50. The flow path is configured. As a result, an appropriate amount of cooling steam can be caused to flow through the cooling steam channel 50, and the moving blade 40 and the impeller 33 can be accurately cooled.

  Here, as shown in FIG. 5, the radial position R1 at the center of the circumferential width of the inner peripheral end face 46a of the protruding end 46 is the radial position R2 at the center of the circumferential width of the outer peripheral end face 33b of the impeller 33. It is preferable to be configured so as to be radially inward from the radial position R2 at the center of the circumferential width of the outer peripheral end surface 33b of the impeller 33.

  For example, as shown in FIG. 5, when the engagement step portions 47 a, 47 b, 47 c of the implantation portion 44 are provided in three steps, the protruding end portion 46 is extended to the engagement step portion 47 a, to the engagement step portion 47 b, or You may comprise to the engagement step part 47c (namely, to the inner peripheral end of the implantation part 44).

  On the other hand, the radial position R3 at the center of the circumferential width on the outer peripheral end face 46b of the protruding end 46 is radially outward from the radial position R4 at the center of the circumferential width of the outer peripheral end face 50a of the cooling steam channel 50. Configured as follows. 2 to 6 show an example in which the outer peripheral end surface 46b of the protruding end portion 46 is the outer peripheral end surface of the shank portion 45.

  As shown in FIGS. 4 and 5, the implanted portion 44 of the moving blade 40 is inserted into each blade groove 32 from the upstream side in the turbine rotor axial direction to constitute a moving blade cascade. The rotor blade cascade is formed in a plurality of stages in the axial direction of the turbine rotor 30.

  The rotor blade 40 having the protruding end 46 as described above is preferably provided in a turbine stage that is exposed to high-temperature steam in the turbine stage, for example, from the upstream to the third stage. The rotor blade 40 including the protruding end 46 is preferably formed in a turbine stage where the inlet steam temperature of the turbine stage, that is, the inlet steam temperature of the stationary blade 23 is, for example, 600 to 750 ° C.

  Further, as shown in FIGS. 1 and 6, a diaphragm outer ring 21 and a diaphragm inner ring 22 are provided along the circumferential direction inside the casing 20. A plurality of stationary blades 23 are supported in the circumferential direction between the diaphragm outer ring 21 and the diaphragm inner ring 22 to form a stationary blade cascade. The stationary blade cascade is arranged in a plurality of stages alternately with the moving blade cascade in the axial direction of the turbine rotor 30 to form a plurality of turbine stages including the stationary blade cascade and the moving blade cascade.

  A labyrinth seal 24 is provided on the inner periphery of the diaphragm inner ring 22 to suppress the leakage of steam from between the diaphragm inner ring 22 and the turbine rotor 30.

  Further, as shown in FIGS. 1 and 6, the diaphragm inner ring 22 is formed with a cooling steam jetting hole 70 that has an opening facing the cooling steam channel 50 and jets cooling steam. A plurality of cooling steam ejection holes 70 are formed in the circumferential direction of the diaphragm inner ring 22 at a position facing the cooling steam channel 50.

  A cooling steam introduction flow path 71 that guides the cooling steam to the cooling steam ejection hole 70 is formed through the stationary blade 23 supported by the diaphragm inner ring 22, the diaphragm outer ring 21 that supports the stationary blade 23, and the casing 20. Yes. The cooling steam introduction flow path 71 is configured by, for example, combining a pipe or a through hole. A cooling steam supply pipe (not shown) for supplying cooling steam is connected to the cooling steam introduction channel 71.

  As the cooling steam, steam extracted from another steam turbine, steam exhausted from another steam turbine, steam extracted from a boiler, or the like can be used. When the steam turbine 10 is an intermediate pressure turbine, for example, steam extracted from a high-pressure turbine can be used as the cooling steam. When the steam turbine 10 is a high-pressure turbine, for example, steam extracted from a boiler can be used as the cooling steam.

  Note that the temperature of the cooling steam is preferably set to a temperature that does not generate a large thermal stress in the components such as the moving blade 40 and the turbine rotor 30 to be cooled. The temperature of the cooling steam can be changed according to the specification of the steam turbine that supplies the cooling steam, and can be set to about 400 ° C., for example.

  The supply pressure of the cooling steam is set such that the pressure of the cooling steam ejected from the cooling steam ejection hole 70 is higher than the pressure in the steam flow path 25. That is, the supply pressure of the cooling steam is set to such an extent that the cooling steam can be reliably ejected from the cooling steam ejection hole 70 to the steam flow path 25. Note that such a cooling steam introduction mechanism for introducing the cooling steam is provided in the turbine stage in which the moving blade 40 including the protruding end portion 46 is disposed.

  Further, as shown in FIG. 1, a plurality of gland labyrinth seals 26 are provided along the circumferential direction on the inner periphery of the casing 20 on the outer side (left side in FIG. 1) from the position where the first stage moving blade 40 is provided. Is provided. Furthermore, a plurality of rows of gland labyrinth seals 26 provided in the circumferential direction are provided along the turbine rotor axial direction to prevent leakage of steam between the casing 20 and the turbine rotor 30 to the outside. Yes.

  Further, the steam turbine 10 is provided with a steam inlet pipe 27 so as to communicate the casing 20. Steam from the outside is introduced into the steam turbine 10 by the steam inlet pipe 27 and introduced into the steam flow path 25 as main steam.

  Next, the operation of the steam turbine 10 having the cooling structure as described above will be described.

  As shown in FIG. 1, the steam introduced from the steam inlet pipe 27 into the steam turbine 10 is guided to the first stage stationary blade 23 and ejected toward the first stage moving blade 40. The steam flows through the steam flow path 25 including the stationary blade 23 and the moving blade 40, and rotates the turbine rotor 30 while performing expansion work. The steam that has passed through the final stage moving blade 40 is exhausted to the outside of the steam turbine 10 through an exhaust passage (not shown).

  The cooling steam introduced from the cooling steam supply pipe (not shown) into the cooling steam ejection hole 70 via the cooling steam introduction channel 71 is ejected toward the opposing cooling steam channel 50. The sprayed cooling steam is suppressed from being diffused by the cooling steam guide 60 and guided to the cooling steam channel 50.

  The cooling steam guided to the cooling steam channel 50 flows into the downstream turbine stage while cooling the rotor blades 40, the impeller 33, and the like. A part of the cooling steam flowing into the downstream turbine stage flows downstream between the labyrinth seal 24 and the turbine rotor 30 and flows along the surface of the rotor disk 31. Then, it is guided by the cooling steam guide 60 and flows into the cooling steam flow path 50.

  At this time, the cooling steam guiding portion 60 projects upstream from the upstream end surface 33 a of the impeller 33, that is, projects upstream from the upstream end surface of the rotor disk 31. The cooling steam that flows along the surface is easily guided into the cooling steam guide 60.

  Even in the downstream turbine stage, when the moving blade 40 having the projecting end portion 46 is arranged, the cooling steam ejection hole as described above can be used in addition to the cooling steam flowing from the upstream turbine stage. The cooling steam ejected from 70 is guided to the cooling steam flow path 50 via the cooling steam guiding section 60.

  The cooling steam flows into the steam flow path 25 after passing through the most downstream turbine stage in which the rotor blade 40 including the protruding end 46 is disposed.

  Thus, the turbine rotor 30 and the moving blade 40 can be cooled by the cooling steam.

  As described above, according to the steam turbine 10 of the first embodiment, it is possible to suppress the inflow of the supplied cooling steam into the steam flow path 25 and reliably introduce the cooling steam to the component to be cooled. Can do. Therefore, the component to be cooled can be accurately and efficiently cooled.

  In addition, the structure of the protrusion end part 46 of the moving blade 40 in the steam turbine 10 of 1st Embodiment is not restricted to an above-described structure. FIG. 7 shows a state in which the moving blades 40 in the positions of the inner peripheral end surfaces 46a of the protruding end portions 46 of the adjacent moving blades 40 are implanted in the blade grooves in the steam turbine 10 of the first embodiment. It is a top view when it sees from the upstream of a rotor axial direction.

  In the rotor blades 40 adjacent to each other in the circumferential direction, the radial position at the center of the circumferential width of the inner peripheral end face 46a of the projecting end 46 between the one rotor blade 40 and the other adjacent rotor blade 40 is different. You may comprise.

  Specifically, as shown in FIG. 7, the radial position R <b> 1 at the center of the circumferential width of the inner peripheral end surface 46 a of the protruding end 46 of one adjacent rotor blade 40 has been described with reference to FIG. 5. Constructed in the same way as That is, the radial position R1 is the same as the radial position R2 at the center of the circumferential width of the outer peripheral end surface 33b of the impeller 33, or from the radial position R2 at the center of the circumferential width of the outer peripheral end surface 33b of the impeller 33. Is also configured to be radially inward.

  On the other hand, the radial position R5 at the center of the circumferential width of the inner peripheral end face 46a of the protruding end 46 of the other rotor blade 40 is the same as the radial position R2 at the center of the circumferential width of the outer peripheral end face 33b of the impeller 33. Alternatively, it is configured to be radially outward from the position and the same as the radial position R4 at the center of the circumferential width of the outer peripheral end face 50a of the cooling steam channel 50, or radially inward from the position. Is done. FIG. 7 shows an example in which the radial position R5 is located between the radial position R2 and the radial position R4.

  As described above, the radial position at the center of the circumferential width of the inner circumferential end surface 46a of the projecting end portion 46 of the rotor blade 40 is configured to be alternately different in the circumferential direction, so that cooling having a circumferential speed component is achieved. Steam can be more reliably introduced into the cooling steam guide 60 and guided to the cooling steam channel 50. As a result, an appropriate amount of cooling steam can be caused to flow through the cooling steam channel 50, and the moving blade 40 and the impeller 33 can be accurately cooled.

(Second Embodiment)
The steam turbine 11 of the second embodiment is the same as the configuration of the steam turbine 10 of the first embodiment except for a cooling steam supply structure for supplying cooling steam. That is, in the steam turbine 11 of the second embodiment, the cooling steam ejection hole 70 formed in the diaphragm inner ring 22, the stationary blade 23, the diaphragm outer ring 21, and the like included in the steam turbine 10 of the first embodiment. The cooling steam introduction flow path 71 formed through the casing 20 is not configured. Here, the configuration of the cooling steam supply structure will be mainly described.

  FIG. 8 is a view showing a cross section (meridian cross section) including the central axis of the turbine rotor 30 of the steam turbine 11 according to the second embodiment.

  As shown in FIG. 8, on the inner peripheral surface of the casing 20 between the ground labyrinth seals 26 provided on the inner periphery of the casing 20 on the outer side (left side in FIG. 8) than the position where the first stage moving blade 40 is provided. A concave groove 80 is formed in the circumferential direction. A ground labyrinth seal 26 is provided on the outer side (left side in FIG. 8) and the inner side (right side in FIG. 8) than the groove part 80 to suppress the leakage of cooling steam introduced into the groove part 80 to the surroundings. ing.

  The casing 20 is formed with a communication hole 82 that communicates with a cooling steam supply pipe 81 that supplies cooling steam and guides the cooling steam to the groove 80. The communication hole 82 functions as a cooling steam introduction channel. In addition, in order to supply cooling steam equally to the groove part 80 over the circumferential direction, it is preferable that the communicating hole 82 is formed in multiple places in the circumferential direction.

  Here, the supplied cooling steam is the same as the cooling steam described in the first embodiment. The supply pressure of the cooling steam is such that the cooling steam ejected from the communication hole 82 to the groove 80 passes between the ground labyrinth seal 26 and the turbine rotor 30 and flows out to the first stage blade 40 side. It is set to the extent that can be.

  Next, the flow of the cooling steam will be described with reference to FIG.

  The cooling steam ejected from the communication hole 82 to the groove 80 flows between the ground labyrinth seal 26 and the turbine rotor 30 and flows out to the first stage rotor blade 40 side while cooling the surface of the turbine rotor 30. . The cooling steam that has flowed out to the first stage moving blade 40 side flows on the rotor disk 31 side downstream of the surface of the turbine rotor 30.

  The cooling steam that has reached the rotor disk 31 flows along the surface of the rotor disk 31, is guided by the cooling steam guide 60, and flows into the cooling steam flow path 50.

  The cooling steam guided to the cooling steam channel 50 flows into the downstream turbine stage while cooling the rotor blades 40, the impeller 33, and the like. A part of the cooling steam flowing into the downstream turbine stage flows downstream between the labyrinth seal 24 and the turbine rotor 30 and flows along the surface of the rotor disk 31. Then, as described above, it is guided by the cooling steam guiding section 60 and flows into the cooling steam channel 50.

  The cooling steam guiding portion 60 projects upstream from the upstream end surface 33 a of the impeller 33, that is, projects upstream from the upstream end surface of the rotor disk 31. The cooling steam flowing in this way is easily guided into the cooling steam guide 60.

  The cooling steam flows into the steam flow path 25 after passing through the most downstream turbine stage in which the rotor blade 40 including the protruding end 46 is disposed.

  Thus, the turbine rotor 30 and the moving blade 40 can be cooled by the cooling steam.

  As described above, according to the steam turbine 11 of the second embodiment, it is possible to suppress the inflow of the supplied cooling steam into the steam flow path 25 and reliably introduce the cooling steam to the component to be cooled. Can do. Therefore, the component to be cooled can be accurately and efficiently cooled.

  According to the embodiment described above, it is possible to reliably introduce the cooling steam to the component to be cooled and sufficiently cool the component.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10,11 ... Steam turbine, 20 ... Casing, 21 ... Diaphragm outer ring, 22 ... Diaphragm inner ring, 23 ... Stator blade, 24 ... Labyrinth seal, 25 ... Steam flow path, 26 ... Grand labyrinth seal, 27 ... Steam inlet pipe, 30 ... turbine rotor, 31 ... rotor disk, 32 ... blade groove, 33 ... impeller, 33a ... end face, 33b, 50a ... outer peripheral end face, 40 ... moving blade, 41 ... blade root part, 42 ... blade effective part, 43 ... shroud, 44 ... Implanted part, 45 ... Shank part, 46 ... Projection end part, 46a ... Inner peripheral end face, 46b ... Outer peripheral end face, 47a, 47b, 47c ... Engagement step part, 50 ... Cooling steam flow path, 60 ... Cooling steam Guide part 70 ... Cooling steam ejection hole 71 ... Cooling steam introduction flow path 80 ... Groove part 81 ... Cooling steam supply pipe 82 ... Communication hole.

Claims (9)

A casing,
A plurality of stationary blades supported between a diaphragm outer ring and a diaphragm inner ring provided along the circumferential direction on the inner peripheral side of the casing;
A turbine rotor provided with an impeller formed by forming a plurality of blade grooves along the turbine rotor axial direction in the circumferential direction;
A blade root portion and a blade effective portion are provided in order along the blade height direction, a part of the blade root portion is implanted in each blade groove, and alternately disposed with the stationary blades in the axial direction of the turbine rotor. A steam turbine comprising a plurality of blades,
The blade is
Formed on at least a part of the upstream end surface of the blade root portion, and provided with a projecting end portion projecting upstream from the upstream end surface of the impeller,
The protruding end portions of the rotor blades adjacent to each other in the circumferential direction form a bowl-shaped cooling steam guide portion that is open at both ends and below, and the cooling steam flowing into the cooling steam guide portion is supplied to the impeller. A steam turbine characterized in that the steam turbine is guided to a cooling steam flow path composed of a gap formed by an outer peripheral end face and each blade root of each of the blades adjacent in the circumferential direction.   The radial position at the center of the circumferential width of the inner peripheral end face of the protruding end is the same as the radial position at the center of the circumferential width of the outer peripheral end face of the impeller, or radially inward of the position. The steam turbine according to claim 1. Among the blades adjacent in the circumferential direction, the radial position at the center of the circumferential width of the inner circumferential end surface of the protruding end portion of one of the blades,
It is the same as the radial position at the center of the circumferential width on the outer peripheral end face of the impeller, or is radially inward from the position,
The radial position at the center of the circumferential width on the inner peripheral end face of the protruding end of the other moving blade is:
Same as the radial position at the center of the circumferential width on the outer peripheral end surface of the impeller,
Or a radial outer side of the position and a radial position at a center of a circumferential width on an outer peripheral end face of the cooling steam channel, or a radial inner side of the position. The steam turbine according to claim 1.   The radial position at the center of the circumferential width of the outer peripheral end surface of the protruding end portion is radially outward from the radial position at the center of the circumferential width of the outer peripheral end surface of the cooling steam channel. Item 4. The steam turbine according to any one of Items 1 to 3.   The steam turbine according to any one of claims 1 to 4, wherein the cooling steam passage penetrates in a turbine rotor axial direction.   The diaphragm inner ring disposed on the upstream side of the moving blade has an opening facing the cooling steam flow path, and a cooling steam ejection hole for ejecting cooling steam is formed therein. The steam turbine according to any one of 1 to 5.   A cooling steam introduction flow path that guides cooling steam to the cooling steam ejection hole is formed through the stationary blade supported by the diaphragm inner ring, the diaphragm outer ring that supports the stationary blade, and the casing. The steam turbine according to claim 6.   The steam turbine according to any one of claims 1 to 5, further comprising a cooling steam introduction flow path for introducing cooling steam to the surface of the turbine rotor on the outer side of the rotor blade at the most upstream stage. . The inner wall of the casing facing the turbine rotor on the outer side of the rotor blade at the most upstream stage is provided with a seal member that prevents leakage of steam along the circumferential direction and a plurality of stages in the axial direction of the turbine rotor,
The steam turbine according to claim 8, further comprising an outlet opening of the cooling steam introduction flow path on an inner wall of the casing between the seal members in a turbine rotor axial direction.

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