JP5783570B2 - Turbine - Google Patents

Description

  The present invention relates to a turbine used in, for example, a power plant, a chemical plant, a gas plant, a steel mill, a ship, and the like.

  As is well known, as a kind of steam turbine, a casing, a shaft (rotor) rotatably provided inside the casing, a plurality of stationary blades fixedly disposed on the inner peripheral portion of the casing, and the plurality of these Some have a plurality of moving blades radially provided on the shaft body on the downstream side of the stationary blade. In the case of an impulse turbine among such steam turbines, the pressure energy of steam is converted into velocity energy by a stationary blade, and this velocity energy is converted into rotational energy (mechanical energy) by the blade. In the case of a reaction turbine, pressure energy is also converted into velocity energy in the rotor blade, and is converted into rotational energy (mechanical energy) by reaction force from which steam is ejected.

  In this type of steam turbine, a radial gap is formed between the tip of the rotor blade and a casing that surrounds the rotor blade to form a steam flow path, and the tip of the stationary blade and the shaft body are formed. Usually, a radial gap is also formed between them. However, the leaked steam that passes through the gap between the blade tip and the casing downstream does not impart a rotational force to the blade. In addition, the leaked steam that passes through the gap between the tip of the stationary blade and the shaft downstream does not convert the pressure energy into velocity energy by the stationary blade, and therefore gives little rotational force to the downstream blade. . Therefore, in order to improve the performance of the steam turbine, it is important to reduce the flow rate (leakage flow rate) of the leaked steam passing through the gap.

Conventionally, as in Patent Document 1, for example, a plurality of step portions whose height gradually increases from the upstream side in the axial direction toward the downstream side are provided at the tip of the moving blade, and the casing is directed toward each step portion. There has been proposed a turbine having a structure in which a plurality of extending seal fins are provided and a minute gap is formed between each step portion and each seal fin. The minute gap is formed in a ring shape when viewed from the axial direction.
In this turbine, the steam that has entered the gap from the upstream side collides with the step surface of the step portion, thereby generating a main vortex on the upstream side of the step surface, and the downstream side of the step surface (near the upstream side of the minute gap). ) Causes peeling vortices. And the reduction | decrease of the leakage flow which passes along a micro clearance gap is achieved by the peeling eddy which arises in the upstream vicinity of a micro clearance gap. That is, the flow rate of leakage steam (leakage flow rate) passing through the gap between the tip of the rotor blade and the casing is reduced.

Japanese Patent Laying-Open No. 2011-080452 (FIG. 6)

However, when a plurality of step portions and seal fins are arranged in the axial direction as in the conventional turbine described above, a plurality of minute gaps between the step portions and the seal fins are also arranged in the axial direction. Of these, the minute gap arranged on the downstream side in the axial direction is positioned on the radially outer side than the minute gap arranged on the upstream side by the step portion.
For this reason, when the number of step portions and seal fins arranged in the axial direction is increased, the diameter of the ring-shaped minute gap arranged on the downstream side increases, and the area of the minute gap increases accordingly. . In other words, the average diameter dimension (clearance average diameter) of the plurality of minute gaps formed in a ring shape increases as the number of steps and seal fins arranged increases. As a result, there is a possibility that there is a limit in reducing the leakage flow rate passing through the gap between the blade tip and the casing and improving the performance of the turbine.

Further, as in the conventional case, when a plurality of step portions are arranged at the tip of the moving blade or the stationary blade, the weight of the step portion becomes heavier as the number of step portions increases, that is, The tip of the moving blade or stationary blade becomes heavy. In this case, the bending stress applied to the moving blade and the stationary blade by gravity increases. Furthermore, in the case of a moving blade, the tensile stress applied to the moving blade increases as the shaft rotates.
When designing the shape of rotor blades and stationary blades, the above stress must also be taken into account, but as the stress increases, the constraints on the shape of the rotor blades and stationary blades due to the stress increase. It becomes difficult to design the shape of a moving blade or a stationary blade for improving performance. In other words, there is a problem that the design freedom of the shape of the moving blades and the stationary blades is low, and it is difficult to improve the performance of the turbine.

  In addition, when a plurality of step portions are arranged at the tip of the moving blade or stationary blade, the length of the moving blade or stationary blade extending outward in the radial direction increases as the number of arranged step portions increases. The interior diameter of the car will increase. That is, there is also a problem that it is difficult to design the passenger compartment in a compact manner.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a turbine capable of improving performance and achieving a compact design of a passenger compartment.

  In order to solve this problem, a turbine according to the present invention includes a blade and a structure that is provided at a tip end side of the blade via a gap and that rotates relative to the blade, and further includes the blade. Adjacent to a plurality of seal fins that are provided on the front end of the structure and the structure so as to alternately extend in the direction of the rotation axis of the structure toward the other side and define a minute gap with the other side. Between the seal fins, the tip for the blade or the structure defining the minute gap together with the seal fin on the downstream side in the rotation axis direction is formed by being recessed in the radial direction of the rotation axis And a recess.

In the turbine, a cavity surrounded by the tip of the blade, the structure, and two seal fins adjacent to each other in the rotation axis direction is formed. Further, the cavity is expanded in the radial direction of the rotating shaft by the expansion recess.
Further, in the turbine described above, since two adjacent seal fins extend in opposite directions, the two minute gaps defined by the two seal fins are positioned so as to be shifted from each other in the radial direction of the rotating shaft. ing.

  In the turbine, when three or more seal fins are arranged, a plurality of the cavities described above are arranged in the rotation axis direction. In addition, three or more minute gaps are defined, but the plurality of minute gaps are arranged in a staggered manner in the direction of the rotation axis.

  In the turbine configured as described above, when fluid flows into the cavity from the upstream side in the rotation axis direction through the minute gap (upstream minute gap), it collides with the downstream seal fin (downstream seal fin). It flows so as to return to the upstream side while turning. That is, a main vortex that rotates in the first rotation direction (for example, counterclockwise) is generated in the cavity. The central axis of the main vortex is displaced in the direction of depression of the expansion recess (in the radial direction of the rotating shaft) as compared with the case where no expansion recess is formed. It is positioned so as to approach the radial position of the gap. As a result, in the vicinity of the upstream side of the downstream minute gap in the cavity, the flow velocity in the radial direction of the rotating shaft due to the main vortex increases, and the leakage flow flowing out of the cavity from the downstream minute gap can be reduced. That is, the contraction effect by the main vortex can be exhibited.

Further, as described above, if a plurality of cavities are arranged in the rotation axis direction, the above-described contraction effect can be obtained for each cavity, so that the leakage flow rate through the gap between the tip of the blade and the structure is sufficiently reduced. It becomes possible.
When a plurality of cavities are arranged, as described above, a plurality of minute gaps are arranged in a staggered manner, so that another main vortex that rotates in the first rotation direction is generated on the downstream side of the cavity. In the cavity, a main vortex that rotates in a direction opposite to the first rotation direction (second rotation direction) is generated.

  In the turbine, as described above, even if a plurality of cavities are arranged in the rotation axis direction, a plurality of minute gaps are arranged in a staggered manner in the rotation axis direction. As in the conventional configuration using the step portion, it is possible to prevent the diameter of the ring-shaped minute gap from becoming large, and to reduce the area of the ring-shaped minute gap as viewed from the axial direction. In other words, it becomes possible to keep the average diameter of the plurality of minute gaps small. As a result, it is possible to reduce the leakage flow through the minute gap and improve the contraction effect by the main vortex.

  Furthermore, in the turbine described above, even if a plurality of cavities are arranged in the rotation axis direction, only the seal fins and the expansion recesses are arranged alternately at the tip of the blade. That is, even if the number of cavities is increased, it is not necessary to increase the thickness of the blade tip as in the conventional configuration using the step portion. Stress applied to the blade can be reduced by weight. Therefore, the degree of freedom in design of the blade shape is improved, and the design of the blade shape for improving the performance of the turbine is facilitated.

  When the structure is a casing, even if the number of cavities increases, the thickness of the blade tip does not increase as in the conventional configuration using the step portion. That is, since the radial dimension of the blade does not become long, the casing interior diameter of the casing can be suppressed to be compact.

  In the turbine, the position of the downstream edge of the expansion recess in the rotational axis direction and the position of the seal fin formed on the downstream side of the expansion recess in the rotational axis direction are It is good to agree.

According to the turbine, there is no step (in the direction of the rotation axis) between the downstream seal fin forming the same cavity and the recess for expansion, and therefore, in the vicinity of the upstream side of the minute gap on the downstream side of the cavity, It is possible to suppress the occurrence of turbulence in the flow of the main vortex generated in That is, the contracted flow effect by the main vortex can be further improved.
In addition, according to the turbine, it is possible to set the dimension of the cavity in the direction of the rotation axis to be shorter than the conventional configuration in which the separation vortex is generated using the step portion, as much as the above-described step is eliminated. . Therefore, when the length of the blade in the rotation axis direction is constant, the number of cavities (number of seal fins) that can be arranged in the rotation axis direction can be set larger than in the conventional configuration, and the tip of the blade It is possible to further reduce the leakage flow rate in the gap between the structure and the structure.

  Further, in the turbine, the extension length of the seal fin extending in the radial direction and the depth dimension of the expansion recess formed on the upstream side in the rotation axis direction of the seal fin coincide with each other. It is preferable.

  In this case, since the radial center position of the cavity coincides with the radial position of the downstream minute gap of the cavity, the radial position of the central axis of the main vortex generated in the cavity is set to the downstream minute gap. It is possible to match the position closer to the radial direction. In particular, when the central direction of the main vortex and the radial direction of the downstream minute gap coincide, the radial flow velocity of the rotating shaft by the main vortex is maximized in the vicinity of the upstream side of the downstream minute gap. Leakage flow that flows out can be efficiently reduced. In other words, the contraction effect by the main vortex can be maximized.

  Further, in the turbine, the blade is surrounded by the tip of the blade, the structure, and the two seal fins adjacent to each other in the rotation axis direction, and is expanded by the expansion recess between the two seal fins. It is preferable that a cavity to be formed is formed, and the dimension in the rotation axis direction and the dimension in the radial direction of the cavity are equal.

  That is, in the turbine, the aspect ratio of the cavity is 1. In this case, the energy of the main vortex generated in the cavity is larger than that in the case where the aspect ratio of the cavity is larger or smaller than 1, and accordingly, the upstream side of the downstream minute gap in the cavity. In the vicinity, the flow velocity in the radial direction of the rotating shaft due to the main vortex also increases. Therefore, it is possible to further reduce the leakage flow that flows out of the cavity from the downstream minute gap and obtain a large contraction effect.

  In the turbine, the inner corner of the recess between the bottom of the extension recess and the edge of the extension recess in the rotation axis direction, one of the tip of the blade or the structure, and the one It is preferable that an inclined surface is formed at at least one corner of the fin corner of the seal fin extending from the portion facing the upstream side of the rotation axis.

In the turbine, it is more preferable that the inclined surface is formed in a curved surface shape.
In addition, the said inclined surface has shown the surface inclined in both the said rotating shaft direction and radial direction. Moreover, the said corner | angular part of a recessed part and the said fin corner | angular part can comprise the corner | angular part of the cavity mentioned above.

  According to the turbine described above, since the inclined surface is formed at the corners of the recesses and the corners of the fins forming the corners of the cavity, the cavity shape approaches the shape of the main vortex generated in the cavity. It is possible to reduce the energy loss of the main vortex at. If the inclined surface is formed in a curved surface, the shape of the cavity further approaches the shape of the main vortex, so that the energy loss of the main vortex can be suppressed particularly small. For this reason, the flow velocity in the radial direction of the rotating shaft generated by the main vortex can be increased in the vicinity of the upstream side of the downstream minute gap. Therefore, it is possible to further reduce the leakage flow flowing out of the cavity from the downstream minute gap and further improve the contraction effect by the main vortex.

According to the present invention, even if the number of seal fins and expansion recesses (cavities) is increased, the area of the ring-shaped minute gap can be kept small, so that it passes through the gap between the tip of the blade and the structure. Therefore, it is possible to easily reduce the leakage flow rate and improve the performance of the turbine associated therewith.
In addition, even if the number of seal fins and expansion recesses (cavities) is increased, the stress applied to the blades can be reduced by suppressing the increase in the weight of the tip part of the blades. The performance can be easily improved.
Furthermore, when the structure is a casing, the radial dimension of the blade does not increase even if the number of arrangements of seal fins and recesses (cavities) is increased. It becomes possible to suppress.

It is a schematic structure sectional view showing the steam turbine concerning the present invention. It is a figure which shows 1st embodiment of this invention, Comprising: It is an expanded sectional view which shows the principal part I in FIG. It is operation | movement explanatory drawing of the steam turbine which concerns on 1st embodiment of this invention. It is a figure which shows 2nd embodiment of this invention, Comprising: It is an expanded sectional view which shows the principal part I in FIG. It is operation | movement explanatory drawing of the steam turbine which concerns on 2nd embodiment of this invention.

[First embodiment]
The first embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the steam turbine 1 according to the present embodiment includes a casing (structure) 10, an adjustment valve 20 that adjusts the amount and pressure of steam (fluid) S flowing into the casing 10, and a casing 10. A shaft body (rotor) 30 that is rotatably provided inward and transmits power to a machine such as a generator (not shown), a stationary blade 40 held by the casing 10, and a moving blade ( Blade) 50 and a bearing portion 60 that supports the shaft body 30 so as to be rotatable about the axis.

The casing 10 is formed so as to hermetically seal the inner space thereof, and a main body portion 11 that defines a flow path of the steam S, and a ring-shaped partition plate that is firmly fixed to the inner wall surface of the main body portion 11. And an outer ring 12.
A plurality of regulating valves 20 are attached to the inside of the main body 11 of the casing 10. The regulating valve chamber 21 into which the steam S flows from a boiler (not shown), the valve body 22, the valve seat 23, and the steam chamber 24. It has. In the regulating valve 20, the steam passage is opened when the valve body 22 is separated from the valve seat 23, so that the steam S flows into the internal space of the casing 10 through the steam chamber 24.

The shaft body 30 includes a shaft body 31 and a plurality of disks 32 extending radially outward from the outer periphery of the shaft body 31. The shaft body 30 transmits rotational energy to a machine such as a generator (not shown).
Further, the bearing portion 60 includes a journal bearing device 61 and a thrust bearing device 62, and supports the shaft body 30 inserted into the main body portion 11 of the casing 10 so as to be rotatable outside the main body portion 11.

A large number of the stationary blades 40 are radially arranged so as to surround the shaft body 30 to form an annular stationary blade group, and are respectively held by the partition plate outer ring 12 described above. That is, each stationary blade 40 extends radially inward from the partition plate outer ring 12.
The leading end of the stationary blade 40 in the extending direction is configured by a hub shroud 41. The hub shroud 41 is formed in a ring shape so as to connect a plurality of stationary blades 40 forming the same annular stationary blade group. The shaft body 30 is inserted through the hub shroud 41, but the hub shroud 41 is disposed between the shaft body 30 and a radial gap.
The annular stator blade group composed of a plurality of stator blades 40 is formed at six intervals in the rotational axis direction of the casing 10 and the shaft body 30 (hereinafter referred to as the axial direction). Is converted into velocity energy and guided to the moving blade 50 adjacent to the downstream side in the axial direction.

The rotor blade 50 is firmly attached to the outer peripheral portion of the disk 32 constituting the shaft body 30 and extends radially outward from the shaft body 30. A large number of the moving blades 50 are arranged radially on the downstream side of each annular stationary blade group to constitute the annular moving blade group.
The above-described annular stationary blade group and the above-described annular moving blade group are set in one stage. That is, the steam turbine 1 is configured in six stages. Among these, the tip part of the moving blade 50 in the final stage is a tip shroud 51 extending in the circumferential direction.

As shown in FIG. 2, the tip shroud 51 that forms the tip of the moving blade 50 is disposed to face the partition plate outer ring 12 of the casing 10 with a radial gap therebetween.
In the present embodiment, the chip shroud 51 is formed in a rectangular cross section. And the outer peripheral surface 51b of this chip | tip shroud 51 is formed so that it may be parallel to an axial direction. Further, the upstream end face (hereinafter referred to as upstream end face 51c) and the downstream end face (hereinafter referred to as downstream end face 51d) of the tip shroud 51 are formed to be parallel to the radial direction. Yes.

On the other hand, the partition plate outer ring 12 is formed with an annular groove 12 a extending in the circumferential direction at a portion corresponding to the chip shroud 51.
In the present embodiment, the annular groove 12a is formed to be recessed radially outward from the inner peripheral surface of the partition plate outer ring 12, and has a rectangular cross section. And the groove bottom surface 12b of this annular groove 12a is formed so as to be parallel to the axial direction, the inner surface on the upstream side in the axial direction of the annular groove 12a (hereinafter referred to as the upstream inner surface 12c), and the downstream side The inner surface (denoted as the downstream inner surface 12d) is formed so as to be parallel to the radial direction.

  The above-described tip shroud 51 is accommodated in the annular groove 12a. In this accommodated state, the outer peripheral surface 51b of the chip shroud 51 faces the groove bottom surface 12b of the annular groove 12a. Further, the upstream end surface 51c of the tip shroud 51 faces the upstream inner surface 12c of the annular groove 12a, and the downstream end surface 51d of the tip shroud 51 faces the downstream inner surface 12d of the annular groove 12a.

The chip shroud 51 and the annular groove 12a configured as described above have a plurality of (four in the illustrated example) seal fins extending in the radial direction toward the other side so as to be alternately arranged in the axial direction. 15 and 55 are provided. A minute gap H is defined between the seal fins 15 and 55 and the counterpart side. The minute gap H is formed in a ring shape when viewed from the axial direction.
Specifically, two seal fins 55 (hereinafter also referred to as blade-side seal fins 55) provided on the tip shroud 51 extend from the outer peripheral surface 51b of the tip shroud 51 toward the groove bottom surface 12b of the annular groove 12a. I'm out. A minute gap H (H2, H4) is defined between the tip in the extending direction of the blade-side seal fin 55 and the groove bottom surface 12b.

On the other hand, the two seal fins 15 (hereinafter also referred to as structure-side seal fins 15) provided in the annular groove 12a are also connected to the outer periphery of the chip shroud 51 from the groove bottom surface 12b of the annular groove 12a, as in the case of the blade-side seal fin 55. It extends toward the surface 51b. A minute gap H (H1, H3) is defined between the tip in the extending direction of the structure-side seal fin 15 and the outer peripheral surface 51b of the tip shroud 51.
The blade side seal fins 55 and the structure side seal fins 15 are alternately arranged in the axial direction.

  In the present embodiment, the extension lengths L of all the seal fins 15 and 55 are set to be equal, and the plurality of seal fins 15 and 55 are arranged at equal intervals in the axial direction. Further, the structure-side seal fin 15 (first structure-side seal fin 15A) is arranged on the most upstream side in the axial direction, and the blade-side seal fin 55 (fourth blade-side seal fin 55D) is arranged on the most downstream side in the axial direction. Is arranged. The first structure-side seal fin 15A is disposed downstream of the axial position of the upstream end surface 51c of the tip shroud 51, and the fourth blade-side seal fin 55D is the shaft of the downstream end surface 51d of the tip shroud 51. It is arranged upstream from the directional position.

  Since the two adjacent seal fins 15 and 55 extend in opposite directions as described above, two minute gaps H (H1 and H3) defined by the two adjacent seal fins 15 and 55 are provided. , H (H2, H4) are offset from each other in the radial direction. In the present embodiment, four minute gaps H (H1 to H4) are defined corresponding to the number of seal fins 15 and 55, and these four minute gaps H (H1 to H4) They are arranged in a staggered pattern in the direction. In particular, in this embodiment, since the extension lengths L of all the seal fins 15 and 55 are equal, the two minute gaps H1 defined between the structure-side seal fin 15 and the outer peripheral surface 51b of the chip shroud 51. , H3 are arranged at the same radial position. Further, two minute gaps H2 and H4 defined between the blade-side seal fin 55 and the groove bottom surface 12b of the annular groove 12a are arranged at the same radial position.

By providing the plurality of seal fins 15 and 55 in this way, a plurality of cavities C are arranged in the axial direction between the chip shroud 51 and the partition plate outer ring 12.
More specifically, the cavity C formed on the most upstream side in the axial direction (hereinafter referred to as the most upstream cavity C1) is formed with respect to the upstream inner surface 12c and the upstream inner surface 12c of the annular groove 12a. The first structure-side seal fin 15A and the upstream end surface 51c of the tip shroud 51 facing each other on the downstream side in the axial direction are surrounded by the groove bottom surface 12b of the annular groove 12a.
Further, the remaining cavities C (hereinafter referred to as gap cavities C2 to C4) that are sequentially arranged on the downstream side in the axial direction from the most upstream cavity C1 are the outer peripheral surface 51b of the chip shroud 51 and the groove bottom surface of the annular groove 12a. 12b and two seal fins 15 and 55 adjacent to each other in the axial direction.

  Further, the chip shroud 51 and the annular groove 12a are formed with recesses for expansion 17 and 57 that are recessed in the radial direction between two seal fins 15 and 55 adjacent in the axial direction. The recesses 17 and 57 for expansion are formed in the tip shroud 51 or the annular groove 12a that defines the minute gap H together with the seal fins 15 and 55 positioned on the downstream side in the axial direction of the two adjacent seal fins 15 and 55. Is set to The expansion recesses 17 and 57 are formed in a rectangular cross section, and expand the gap cavities C2 to C4 described above in the radial direction.

Specifically, in the annular groove 12a, the first structure side seal fin 15A and the second blade side seal fin 55B, and the third structure side seal fin 15C and the fourth blade side seal are adjacent to each other. An expansion recess 17 (hereinafter also referred to as a structure-side recess 17) that is recessed radially outward from the groove bottom surface 12b is formed between the fin 55D. Each structure-side recess 17 extends the first gap cavity C2 and the third gap cavity C4 outward in the radial direction.
On the other hand, the tip shroud 51 includes an expansion recess 57 (hereinafter, also referred to as a blade side recess 57) that is recessed from the outer peripheral surface 51b of the tip shroud 51 between the second blade side seal fin 55B and the third structure side seal fin 15C. Are described). The blade-side recess 57 extends the second gap cavity C3 radially inward.

Further, the end edge on the downstream side in the axial direction of each of the above-described expansion recesses 17 and 57 (hereinafter referred to as downstream end edges 18d and 58d) is a seal fin formed on the downstream side of each of the expansion recesses 17 and 57. 15 and 55 (hereinafter also referred to as downstream seal fins 55B, 15C, and 55D) and the axial position coincide with each other. As a result, there is no axial step between the downstream seal fins 55B, 15C, 55D and the expansion recesses 17, 57 that form the same gap cavity C2 to C4.
In this embodiment, since each of the expansion recesses 17 and 57 is formed in a rectangular cross section, the shafts of the expansion recesses 17 and 57 extending in the radial direction from the downstream end edges 18d and 58d of the expansion recesses 17 and 57 are provided. The inner surface on the downstream side in the direction (hereinafter referred to as the downstream inner surfaces 19d and 59d) is parallel to the radial direction. Therefore, the downstream inner side surfaces 19d, 59d of the expansion recesses 17, 57 and the surface of the downstream seal fins 55B, 15C, 55D facing the upstream side in the axial direction form the same plane.

  The depth dimension D (D2 to D4) of each of the expansion recesses 17 and 57 is the extension length L of the downstream seal fins 55B, 15C and 55D formed on the downstream side of each of the expansion recesses 17 and 57. It matches. Thereby, the radial center positions of the gap cavities C2 to C4 coincide with the radial directions of the minute gaps H2 to H4 forming the downstream side of the gap cavities C2 to C4.

  Further, in the present embodiment, the axially upstream edge of each of the expansion recesses 17 and 57 (hereinafter referred to as upstream edge 18c and 58c) is formed on the upstream side of each of the expansion recesses 17 and 57. The seal fins 15 and 55 (hereinafter referred to as upstream seal fins 15A, 55B, and 15C) coincide with the positions in the axial direction. In particular, in this embodiment, since the expansion recesses 17 and 57 are formed in a rectangular cross section, the expansion recesses 17 and 57 extending in the radial direction from the upstream end edges 18c and 58c of the expansion recesses 17 and 57 are formed. The inner surface on the upstream side in the axial direction (hereinafter referred to as the upstream inner surfaces 19c and 59c) is parallel to the radial direction. Therefore, the upstream inner side surfaces 19c, 59c of the expansion recesses 17, 57 and the surface of the upstream seal fins 15A, 55B, 15C facing the downstream side in the axial direction form the same plane.

As described above, the relative positions of the seal fins 15 and 55 and the expansion recesses 17 and 57 are set, so that the interval between the two adjacent seal fins 15 and 55 and the two seal fins 15 and 55 are set. The axial dimensions of the expansion recesses 17 and 57 formed between the two are equal to each other. That is, the gap cavities C2 to C4 expanded by the expansion recesses 17 and 57 are each formed in a rectangular cross section.
Furthermore, in this embodiment, the dimension in the axial direction and the dimension in the radial direction of the gap cavities C2 to C4 are equal to each other. For this reason, the gap cavities C2 to C4 of the present embodiment are each formed in a square cross section. In other words, the aspect ratio of each gap cavity C2 to C4 is set to 1.

In order to sufficiently exhibit the effects described later in the steam turbine 1 configured as described above, the relative positional relationship between the seal fins 15 and 55 and the expansion recesses 17 and 57, various dimensions, In consideration of the shape of each cavity C, the size of each minute gap H, etc., the amount of thermal elongation of the casing 10 and the moving blade 50 accompanying the change in the operating state of the steam turbine 1, the amount of centrifugal elongation of the moving blade 50, etc. It is preferably set.
That is, the relative positional relationship and various dimensions between the seal fins 15 and 55 and the expansion recesses 17 and 57 described above, the shape of each cavity C, the dimension of each minute gap H, and the like are set during the operation of the steam turbine 1. In particular, it is more desirable to set it optimally during rated operation. For example, the axial relative positions of the downstream end edges 18d, 58d of the expansion recesses 17, 57 and the downstream seal fins 55B, 15C, 55D located downstream of the expansion recesses 17, 57 are as follows: It is preferable that they coincide with each other during operation, and most preferably coincide with each other during rated operation.

Next, operation | movement of the steam turbine 1 of the structure mentioned above is demonstrated.
First, when the regulating valve 20 (see FIG. 1) is opened, the steam S flows into the internal space of the casing 10 from a boiler (not shown).

  The steam S flowing into the internal space of the casing 10 sequentially passes through the annular stator blade group and the annular rotor blade group in each stage. At this time, pressure energy is converted into velocity energy by the stationary blade 40, and most of the steam S passing through the stationary blade 40 flows between the moving blades 50 constituting the same stage. The velocity energy of S is converted into rotational energy, and rotation is imparted to the shaft body 30. On the other hand, after a part (for example, several%) of the steam S flows out from the stationary blade 40, as shown in FIG. 3, in the annular groove 12 a (the tip of the moving blade 50 and the partition plate outer ring of the casing 10). 12 is a so-called leaked steam that flows into the gap 12.

  Here, the steam S flowing into the annular groove 12a first flows into the uppermost stream cavity C1, collides with the upstream end face 51c of the chip shroud 51, and returns to the upstream side while rotating in the uppermost stream cavity C1. Flowing into. As a result, a main vortex MV1 that rotates counterclockwise (first rotation direction) is generated in the most upstream cavity C1.

At that time, in particular, at the corner (edge) between the upstream end surface 51c and the outer peripheral surface 51b of the chip shroud 51, a part of the flow is separated from the main vortex MV1, so that the outer peripheral surface 51b of the chip shroud 51 is In the vicinity of the corner portion, a separation vortex SV1 that rotates in the clockwise direction (second rotation direction) opposite to the main vortex MV1 is generated.
The separation vortex SV1 is located in the vicinity of the upstream side of the first minute gap H1 between the first structure-side seal fin 15A and the tip shroud 51. In particular, since the downflow toward the radially inner side of the separation vortex SV1 occurs immediately before the first minute gap H1, it flows from the most upstream cavity C1 through the first minute gap H1 into the downstream first gap cavity C2. The contraction effect for reducing the leaking flow is obtained by the separation vortex SV1.

  Then, when the steam S passes through the first minute gap H1 from the most upstream cavity C1 and flows into the first gap cavity C2, it collides with the downstream seal fin 55B that forms the downstream side of the first gap cavity C2. , Flowing around to return to the upstream side. As a result, a main vortex MV2 that rotates in the same first direction (counterclockwise) as the main vortex MV1 generated in the most upstream cavity C1 is generated in the first gap cavity C2.

The central axis A2 of the main vortex MV2 generated in this way is displaced in the direction of depression of the expansion recess 17 (outside in the radial direction) as compared with the case where the expansion recess 17 is not formed, so the first gap cavity C2 It is located so as to approach the radial position of the second minute gap H2 on the downstream side.
Thereby, in the vicinity of the upstream side of the second minute gap H2 in the first gap cavity C2, the flow velocity on the outer side in the radial direction by the main vortex MV2 becomes larger than in the case where the expansion recess 17 is not formed. That is, the velocity component on the radially outer side of the velocity vector of the main vortex MV2 in the vicinity of the upstream side of the second minute gap H2 increases, passes through the second minute gap H2 from the first gap cavity C2, and passes through the second gap on the downstream side. The leakage flow flowing out into the cavity C3 can be reduced. In other words, the contraction effect by the main vortex MV2 in the first gap cavity C2 can be exhibited.

  In particular, in the present embodiment, since the center position in the radial direction of the first gap cavity C2 coincides with the radial position of the second minute gap H2, the center axis A2 of the main vortex MV2 generated in the first gap cavity C2 Can be made closer to the radial position of the second minute gap H2 and matched.

Furthermore, in the present embodiment, since no step in the axial direction is generated between the downstream seal fin 55B that forms the downstream side of the first gap cavity C2 and the expansion recess 17, the vicinity of the upstream side of the second minute gap H2 , The occurrence of turbulence in the flow of the main vortex MV2 generated in the first gap cavity C2 is suppressed. In other words, in the first gap cavity C2, in the vicinity of the upstream side of the second minute gap H2, the flow toward the radially outer side can be suppressed from being weakened.
From the above, in the present embodiment, in the vicinity of the upstream side of the second minute gap H2, the flow velocity on the radially outer side due to the main vortex is maximized, passes through the second minute gap H2 from the first gap cavity C2, and passes through the second gap. The leakage flow flowing out into the cavity C3 can be efficiently reduced. In other words, the contraction effect by the main vortex MV2 in the first gap cavity C2 can be maximized.

  Further, when the vapor S flows from the first gap cavity C2 to the second gap cavity C3 through the second minute gap H2, the downstream of the second gap cavity C3 as in the case of the first gap cavity C2. It collides with the downstream seal fin 15C forming the side and flows so as to return to the upstream side while rotating. That is, the main vortex MV3 is also generated in the second gap cavity C3. However, since the second gap cavity C3 is formed in the radial direction opposite to the first gap cavity C2, the main vortex MV3 generated in the second gap cavity C3 is the main vortex MV2 generated in the first gap cavity C2. Rotate in the second rotation direction (clockwise) opposite to the first rotation direction.

  Further, when the steam S flows from the second gap cavity C3 through the third minute gap H3 on the downstream side into the third gap cavity C4, it collides with the downstream seal fin 55D that forms the downstream side of the third gap cavity C4. Then, it flows so as to return to the upstream side while turning. That is, the main vortex MV4 is also generated in the third gap cavity C4. However, the main vortex MV4 generated in the third gap cavity C4 rotates in the first rotation direction (counterclockwise) opposite to the second rotation direction of the main vortex MV3 generated in the second gap cavity C3.

The main vortices MV3 and MV4 generated in the second gap cavity C3 and the third gap cavity C4 exhibit the same contraction effect as that of the main vortex MV2 in the first gap cavity C2 described above. For example, the radial positions of the central axes A3 and A4 of the main vortices MV3 and MV4 generated in the second and third gap cavities C3 and C4 are also brought closer to the radial positions of the third and fourth minute gaps H3 and H4, respectively. Since they can be matched, the leakage flow flowing out of the second and third gap cavities C3 and C4 from the second and third gap cavities C3 and C4 through the third and fourth minute gaps H3 and H4 is efficiently generated. Can be reduced.
Therefore, in the present embodiment, by arranging a plurality of gap cavities C2 to C4 that can obtain a contraction effect, the leakage flow rate that passes through the gap between the tip of the moving blade 50 and the outer ring 12 of the partition plate of the casing 10 is reduced. It can be sufficiently reduced.

As described above, according to the steam turbine 1 of the present embodiment, even if a plurality of gap cavities C2 to C4 formed by two adjacent seal fins 15 and 55 are arranged in the axial direction, a plurality of minute gaps H are provided. Are arranged in a zigzag pattern in the axial direction, so that even if the number of gap cavities C2 to C4 is increased, the diameter of the ring-shaped minute gap H is increased as in the conventional configuration using the step portion. Thus, the area of the ring-shaped minute gap H viewed from the axial direction can be kept small. In other words, the average diameter of the plurality of minute gaps H can be kept small. As a result, it is possible to reduce the leakage flow through the minute gap H and improve the contraction effect by the main vortices MV2 to MV4.
Accordingly, it is possible to easily reduce the leakage flow rate of the steam S passing through the gap between the tip of the moving blade 50 and the partition plate outer ring 12 of the casing 10 and to improve the performance of the steam turbine 1 associated therewith.

  Further, in the steam turbine 1 of the present embodiment, even if a plurality of the gap cavities C2 to C4 are arranged in the axial direction, the seal fins 15 and 55 and the expansion recess 17 and 57 are only arranged alternately. That is, even if the number of the gap cavities C2 to C4 increases, it is not necessary to increase the thickness of the chip shroud 51 as in the conventional configuration using the step portion. The weight applied to the rotor blade 50 by the weight of 51 can be reduced. Accordingly, the design freedom of the shape of the moving blade 50 is improved, and the shape of the moving blade 50 for improving the performance of the steam turbine 1 can be easily designed.

  Further, in the steam turbine 1 of the present embodiment, even if the number of the gap cavities C2 to C4 is increased, the thickness of the chip shroud 51 is not increased unlike the conventional configuration using the step portion. That is, since the radial dimension of the moving blade 50 does not become long, the inside diameter of the casing 10 can be reduced in a compact manner.

  Further, according to the steam turbine 1 of the present embodiment, an axial step is generated between the downstream seal fins 55B, 15C, and 55D that form the same gap cavities C2 to C4 and the expansion recesses 17 and 57. Therefore, it is possible to set the axial dimensions of the gap cavities C <b> 2 to C <b> 4 to be shorter than the conventional configuration in which the separation vortex is generated using the step portion, as much as this step is eliminated. Accordingly, when the axial length of the chip shroud 51 is constant, the number of gap cavities C2 to C4 (number of seal fins 15 and 55) that can be arranged in the axial direction is set larger than that of the conventional configuration. It is possible to further reduce the leakage flow rate in the gap between the tip of the moving blade 50 and the partition plate outer ring 12 of the casing 10.

  Further, in the steam turbine 1 of the present embodiment, the aspect ratio of each gap cavity C2 to C4 is 1, so that the energy of the main vortices MV2 to MV4 generated in each gap cavity C2 to C4 is the gap cavity C2. The aspect ratio of .about.C4 becomes larger than when the aspect ratio is larger or smaller than 1. Along with this, in the vicinity of the upstream side of the minute gaps H2 to H4 located on the downstream side of the gap cavities C2 to C4, the radial flow velocity due to the main vortices MV2 to MV4 also increases. Accordingly, it is possible to further reduce the leakage flow passing through the gaps C2 to C4 and the minute gaps H2 to H4 on the downstream side, thereby obtaining a large contraction effect.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
In this embodiment, compared with the steam turbine 1 of the first embodiment, only the cross-sectional shape of each cavity C is different, and the other configurations are the same as those of the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the tip shroud 51 and the annular groove 12a of the present embodiment are provided with seal fins 15 and 55 and expansion recesses 17 and 57 similar to those of the first embodiment, whereby a plurality of cavities C are formed. (C1 to C4) are formed.

In the present embodiment, inclined surfaces 70A and 70B are formed at the inner corners of the recesses between the bottoms of the respective extension recesses 17 and 57 and the end edges in the axial direction. In the present embodiment, since the respective expansion recesses 17 and 57 are formed in a rectangular cross section, the bottom indicates the recess bottom surfaces 19a and 59a of the respective expansion recesses 17 and 57. Further, the end edge portion includes the upstream inner side surfaces 19c and 59c of the respective extension recesses 17 and 57 including the upstream end edges 18c and 58c, and the respective extension recesses 17 and 57 including the downstream end edges 18d and 58d. It shows the downstream inner side surfaces 19d and 59d. And the said corner | angular part in a recessed part makes two corner | angular parts among each clearance gap cavity C2-C4 formed in the cross-sectional rectangular shape.
In this way, the inclined surfaces 70A and 70B formed at the inner corners of the recesses are curved so that the recess bottom surfaces 19a and 59a and the upstream inner side surfaces 19c and 59c and the downstream inner side surfaces 19d and 59d are smoothly connected. Is formed.

In the present embodiment, the inclined surface is also formed on the fin corner portion between the outer peripheral surface 51 b of the tip shroud 51 and the surface (part) facing the upstream side in the axial direction of the blade-side seal fin 55 extending from the tip shroud 51. 70C is formed. Similarly, the inclined surface 70C is also formed at the fin corner portion between the groove bottom surface 12b of the annular groove 12a and the surface (part) facing the upstream side in the axial direction of the structure-side seal fin 15 extending from the groove bottom surface 12b. Is formed. The fin corner portion forms one corner portion of each of the gap cavities C2 to C4, or forms one corner portion of the most upstream cavity C1.
As described above, the inclined surface 70C formed at each corner of the fin is smooth in the outer peripheral surface 51b of the tip shroud 51 and the groove bottom surface 12b of the annular groove 12a and the surfaces of the seal fins 15 and 55 facing the upstream side in the axial direction. It is formed in a curved surface so as to be continuous.

  Furthermore, in the present embodiment, the inclined surface 70D is also formed in the groove inner corner between the groove bottom surface 12b and the upstream inner surface 12c of the annular groove 12a. The corner in the groove forms one corner of the most upstream cavity C1. In this way, the inclined surface 70D formed at the corner in the groove is formed in a curved surface so that the groove bottom surface 12b and the upstream inner surface 12c are smoothly connected.

  All the inclined surfaces 70 (70A to 70D) described above are inclined both in the axial direction and in the radial direction. In addition, each inclined surface 70 may be directly formed on the partition plate outer ring 12, the tip shroud 51, and the seal fins 15, 55 of the casing 10, but as shown in the illustrated example, the partition plate outer ring 12 and the tip shroud of the casing 10. 51 and seal fins 15 and 55 may be formed by providing inclined wall portions 71 separate from the corner portions.

As described above, the cross-sectional shapes of the gap cavities C2 to C4 are rounded by the inclined surfaces 70A to 70C so as to approach the circle including the “ellipse” from the rectangle as in the first embodiment (see FIGS. 2 and 3), respectively. It will be formed. In particular, in this embodiment, since the aspect ratio of the gap cavities C2 to C4 is set to 1 as in the first embodiment, the cross-sectional shape of the gap cavities C2 to C4 approaches a “perfect circle”. However, of the four corners of the gap cavities C2 to C4, the inclined surfaces 70A to 70C are formed only at the three corners. Since the minute gaps H1 to H3 are located in the remaining one corner, the inclined surface 70 is not formed.
Further, the two corners (groove inner corner and fin corner) of the most upstream cavity C1 are rounded by the inclined surfaces 70C and 70D.

The operation of the steam turbine of the present embodiment configured as described above is the same as that of the first embodiment.
That is, as shown in FIG. 5, the steam S that has flowed into the annular groove 12a first flows into the most upstream cavity C1, and thereby the main vortex MV1 that rotates in the first rotation direction into the most upstream cavity C1, and Then, a separation vortex SV1 rotating in the second rotation direction is generated.
Here, since the corner in the groove of the most upstream cavity C1 is formed in an arc shape close to the shape of the main vortex MV1 by the inclined surface 70D, the energy loss of the main vortex MV1 generated in the corner in the groove can be suppressed to be small. it can. In other words, the energy of the separation vortex SV1 generated by the main vortex MV1 is larger than that in the first embodiment.

Further, since the fin corner portion of the most upstream cavity C1 is formed in an arc shape close to the shape of the separation vortex SV1 by the inclined surface 70C, the energy loss of the separation vortex SV1 generated at the fin corner portion can be suppressed to be small. .
From the above, the downflow directed inward in the radial direction generated just before the first minute gap H1 by the separation vortex SV1 is larger than that in the first embodiment, and the first flow downstream from the most upstream cavity C1. The leakage flow that flows out to the gap cavity C2 can be further reduced. That is, it is possible to improve the contraction effect by the separation vortex SV1.

Further, when the steam S flows into the gap cavities C2 to C4 from the axial upstream side (for example, the most upstream cavity C1) through the minute gaps H1 to H3, the main vortices MV2 to MV2 enter the gap cavities C2 to C4. MV4 is generated.
Here, since the three corners of the gap cavities C2 to C4 are formed in an arc shape close to the shape of the main vortices MV2 to MV4 by the inclined surfaces 70A to 70C, the main vortices generated at these three corners. The energy loss of MV1 can be kept small. In other words, the radial direction generated by the main vortices MV2 to MV4 in the vicinity of the upstream side of the minute gaps H2 to H4 (hereinafter referred to as downstream minute gaps H2 to H4) located on the downstream side of the gap cavities C2 to C4. The flow velocity is larger than that in the first embodiment.
Therefore, the leakage flow flowing out of the gap cavities C2 to C4 from the downstream minute gaps H2 to H4 can be further reduced, and the contraction effect by the main vortices MV2 to MV4 can be improved.

  In addition to the effects described above, the steam turbine according to the present embodiment also has the same effects as the first embodiment.

Although the details of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the second embodiment, the inclined surface 70 is formed at all three corners of the same gap cavity C2, but may be formed only at one corner, for example.
In the second embodiment, the inclined surface 70 is formed in all the cavities C, but may be formed in at least one gap cavity C2 to C4.

Furthermore, in the second embodiment, each inclined surface 70 is not limited to a curved shape so that the corners of the cavity C are rounded, but at least the corners of the cavity C are generated in the cavity C. What is necessary is just to incline in both the axial direction and radial direction so that the shape of main vortex MV1-MV4 and peeling vortex SV1 may be approximated. Therefore, each inclined surface 70 may be formed in a cross-sectional linear shape so that, for example, the cavity C is formed in a polygonal shape having more corners than a rectangular shape.
Further, when the inclined surface 70 is linear in cross section, not only one inclined surface 70 is formed at the same corner, but, for example, the corner shape of the cavity C is generated in the cavity C. A plurality of inclined surfaces 70 having different inclination angles may be formed so as to be closer to the main vortex MV1 to MV4 or the separation vortex SV1.

  In all the embodiments described above, the contraction effect that reduces the leakage flow from the most upstream cavity C1 to the first gap cavity C2 uses the separation vortex SV1, but for example, uses the main vortex MV1. Also good. In this case, for example, the axial position of the first structure-side seal fin 15A is made to coincide with the upstream end face 51c of the chip shroud 51, as in the case of the downstream-side seal fins 55B, 15C, 55D of the gap cavities C2 to C4. Just do it. In this case, the extension length L of the first structure-side seal fin 15A is set to the upstream end face 51c so that the flow velocity on the radially outer side due to the main vortex MV1 increases in the vicinity of the upstream side of the first minute gap H1. More preferably, it is made to coincide with the radial dimension.

In addition, the depth dimension D of each of the expansion recesses 17 and 57 is equal to the extension length L of the downstream seal fins 55B, 15C, and 55D located on the downstream side of each of the expansion recesses 17 and 57. For example, it may be different from the extension length L.
However, it is preferable that the difference between the depth dimension D and the extension length L is small. That is, as the difference between the depth dimension D and the extension length L is smaller, the radial positions of the central axes A2 to A4 of the main vortices MV2 to MV4 generated in the gap cavities C2 to MV4 are the positions of the gap cavities C2 to C4. It approaches the radial position of the minute gaps H2 to H4 located on the downstream side. As a result, the leakage flow flowing from the gap cavities C2 to C4 through the minute gaps H2 to H4 to the downstream side is reduced, and the contraction effect by the main vortices MV2 to MV4 in the gap cavities C2 to C4 is more effective. Can be demonstrated.

Further, the axial positions of the upstream end edges 18c, 58c of the respective expansion recesses 17, 57 are set in the axial direction of the upstream seal fins 15A, 55B, 15C of the respective expansion recesses 17, 57 as in the above-described embodiment. For example, the position may be shifted to the downstream side in the axial direction with respect to the upstream seal fins 15A, 55B, and 15C.
Furthermore, in the above embodiment, no axial step is generated between the downstream seal fins 55B, 15C, and 55D that form the same gap cavities C2 to C4 and the expansion recesses 17 and 57. May have occurred. However, in this case, it is more preferable that the downstream end edges 18d and 58d of the expansion recesses 17 and 57 are positioned on the upstream side in the axial direction with respect to the downstream seal fins 55B, 15C and 55D.

Further, the aspect ratio of each gap cavity C2 to C4 may not be set to 1 as in the above embodiment.
Furthermore, in the above-described embodiment, the plurality of seal fins 15 and 55 are arranged at equal intervals in the axial direction, but may be arranged at unequal intervals, for example.

In addition, the extending lengths L of the plurality of seal fins 15 and 55 are all set to be equal, but may be different from each other, for example.
Furthermore, in the above embodiment, a plurality of the gap cavities C2 to C4 are formed, but it is sufficient that at least one gap cavity is formed. In other words, four seal fins 15 and 55 are formed in the above embodiment, but it is sufficient that at least two seal fins are formed.
In the above embodiment, all the seal fins 15 and 55 alternately extend from the tip shroud 51 and the annular groove 12a toward the mating side, but at least the gap cavities C2 to C4 similar to the above embodiment are provided. It is sufficient that at least one structure-side seal fin 15 and one blade-side seal fin 55 (a pair of seal fins 15 and 55) are arranged side by side in the axial direction so that one is formed. Therefore, in addition to the pair of seal fins 15 and 55 described above, for example, only the plurality of structure-side seal fins 15 or only the plurality of blade-side seal fins 55 may be continuously arranged in the axial direction.

Further, the cavity C, the seal fins 15 and 55 forming the cavity C, and the expansion recesses 17 and 57 are formed in the partition plate outer ring 12 of the casing 10. For example, the casing C without the partition plate outer ring 12 is provided. You may form directly in the 10 main-body parts 11. FIG.
Furthermore, in the above embodiment, the cavity C exhibiting the contraction effect is formed in the final stage moving blade 50, but may be formed in the other stage moving blade 50, for example.

  In addition, the cavity C that exhibits the contraction effect as in the above embodiment is not limited to being formed in the gap between the tip shroud 51 that forms the tip of the moving blade 50 and the casing 10. It may be formed in the gap between the hub shroud 41 and the shaft body 30 forming the tip. That is, the stationary blade 40 may be the “blade” of the present invention, and the shaft body 30 may be the “structure” of the present invention. Even in this case, the same effect as all the embodiments described above can be obtained.

In the above embodiment, the present invention is applied to a condensing steam turbine. However, the present invention is applied to other types of steam turbines, for example, turbine types such as a two-stage extraction turbine, an extraction turbine, and an air-mixing turbine. You can also
Furthermore, in the above-described embodiment, the present invention is applied to a steam turbine. However, the present invention can also be applied to a gas turbine, and further, the present invention can be applied to all the rotor blades.

DESCRIPTION OF SYMBOLS 1 ... Steam turbine (turbine), 10 ... Casing (structure), 11 ... Main-body part, 12 ... Partition plate outer ring, 12a ... Ring groove, 12b ... Groove bottom face, 15, 15A, 15C, 55, 55B, 55D ... Seal Fins, 17, 57 ... recess for expansion, 19a, 59a ... bottom surface (bottom), 18c, 58c ... upstream edge (edge), 18d, 58d ... downstream edge (edge), 19c, 59c ... upstream Side inner side surface (end edge portion), 19d, 59d ... downstream inner side surface (end edge portion), 30 ... shaft body, 40 ... stationary blade, 50 ... moving blade (blade), 70, 70A, 70B, 70C, 70D ... Inclined surface, 71 ... Inclining wall, C ... Cavity, C1 ... Most upstream cavity, C2, C3, C4 ... Gap cavity, D, D2, D3, D4 ... Depth dimension, L ... Extension length, H , H1, H2, H3, H4 ... minute gap

Claims (7)

A blade,
A turbine provided with a structure provided on the tip side of the blade via a gap and rotating relative to the blade,
A plurality of seal fins provided on the tip of the blade and the structure alternately extending in the direction of the rotation axis of the structure toward the other side and defining a minute gap with the other side;
Between the adjacent seal fins, the blade is formed in the tip of the blade or the structure defining the minute gap together with the seal fin on the downstream side in the rotation axis direction so as to be depressed in the radial direction of the rotation axis. And a recess for expansion.   The turbine according to claim 1, wherein three or more seal fins are arranged.   The position in the rotation axis direction of the downstream edge of the expansion recess is coincident with the position in the rotation axis direction of the seal fin formed on the downstream side of the expansion recess. The turbine according to claim 1 or 2.   The extension length of the seal fin extending in the radial direction and the depth dimension of the expansion recess formed on the upstream side in the rotation axis direction of the seal fin are the same. The turbine according to any one of claims 1 to 3. A cavity is formed that is surrounded by the tip of the blade, the structure, and the two seal fins adjacent to each other in the rotation axis direction and is expanded by the expansion recess between the two seal fins,
The turbine according to any one of claims 1 to 4, wherein a dimension of the cavity in the rotation axis direction and a dimension in the radial direction are equal.   The inner corner of the recess between the bottom of the extension recess and the edge of the extension recess in the rotation axis direction, one of the tip of the blade or the structure, and the seal fin extending from the one The inclined surface is formed in at least one corner part of the fin corner part with the site | part which faces the said rotating shaft upstream among these, The Claim 1 characterized by the above-mentioned. Turbine.   The turbine according to claim 6, wherein the inclined surface is formed in a curved surface shape.

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