JP7148273B2 - steam turbine - Google Patents

Description

The present invention relates to steam turbines.

Turbomachinery, including steam turbines and gas turbines, converts the energy of a fluid taken in from the outside into rotational motion of a rotor. Specifically, a steam turbine includes a rotor that rotates about an axis and a casing that covers the rotor from the outer peripheral side. A plurality of moving blade stages (moving blades) are provided on the outer peripheral surface of the rotor, and a plurality of stationary blade stages (stationary blades) are provided on the inner peripheral surface of the casing. The rotor blade stages and the stator blade stages are arranged so as to be staggered in the axial direction. The fluid introduced into the casing rotates the rotor by alternately colliding with the moving blade stages and the stationary blade stages.

By the way, in a steam turbine, in order to realize smooth rotation of the rotor, it is common to provide a constant clearance between the tip portions (shrouds) of moving blades and the inner peripheral surface of the casing. However, since the steam flowing through the clearance flows downstream without colliding with the moving blades or stationary blades, it does not contribute to the rotational driving of the rotor. Therefore, there is a need for a technique for reducing steam circulation (leakage) in this clearance as much as possible. As an example of such technology, one described in Patent Document 1 below is known. In the device according to Patent Document 1, a plurality of fins are provided between the inner peripheral surface of the eaves provided on the downstream side of the stator blade outer ring and the outer peripheral surface of the moving blade shroud. Furthermore, the inner peripheral surface of the eaves portion is located radially outside the inner peripheral surface of the stator blade outer ring. Thereby, a concave portion is formed by a pair of stator blade outer rings adjacent to each other and the inner peripheral surface of the eaves portion. The blade shroud and fins are contained within this recess. The provision of the fins is said to reduce leakage steam that deviates from the mainstream steam and flows into the recesses, thereby improving the efficiency of the steam turbine.

Japanese Patent Application Laid-Open No. 2007-321721

However, since a gap is formed between the tips of the fins and the outer peripheral surface of the rotor blade shroud, leakage steam still exists through this gap. The leaked steam forms a vortex between the most downstream fin and the downstream side surface of the recess (the surface facing the upstream side of the stator blade outer ring located downstream). Some of the components that deviate from this vortex collide with the downstream surface of the recess, change direction, and join the mainstream steam. Specifically, this leaked steam flows from the radially outer side toward the inner side. On the other hand, mainstream steam flows from the upstream side toward the downstream side. For this reason, the angle at which the leaked steam and the mainstream steam intersect becomes large, and a mixing loss occurs between them. As a result, the efficiency of the steam turbine may decrease.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam turbine with improved efficiency by reducing mixing loss.

According to a first aspect of the present invention, a steam turbine includes a rotating shaft rotating about an axis, a moving blade body extending radially outward from the rotating shaft, and a radially outer end portion of the moving blade body. a rotor blade having a shroud provided in a casing; a casing surrounding the rotor blade from the radially outer side and having a recess for accommodating the shroud on the inner peripheral side; and a facing surface of the recess facing the shroud. a fin that protrudes radially inward and forms a clearance between itself and the outer peripheral surface of the shroud, wherein the recess faces the axial downstream side of the clearance and extends radially outward toward the downstream side. and a guide surface extending radially inward from the downstream and radially outer end of the guide surface toward the upstream side via the radially outer side of the opposing surface. and a return surface connected to a radially outer end of the downstream facing surface, wherein the guide surface is located in a region defined by the guide surface, the return surface, and the downstream facing surfaces of the fins. A swirling vortex is formed in the order of the surface, the return surface, and the downstream facing surface of the fin.

Here, in the space surrounded by the surface of the fin facing the downstream side, the guide surface, and the reflux surface, the steam that has passed through the clearance forms a vortex swirling in the direction from the guide surface to the fin via the reflux surface. be done. In the above configuration, the guide surface extends radially outward toward the downstream side. As a result, compared to the case where the guide surface spreads in the direction (radial direction) orthogonal to the axis, for example, the axial component of the steam flow increases, making it easier to form a stronger vortex. Furthermore, the reflux surface extends to the surface of the fin facing downstream via the radially outer side of the opposing surface. As a result, the region in which the vortex is formed can be expanded, for example, compared to the case where the reflux surface is at the same position as the opposing surface in the radial direction. As a result, the swirl center of the vortex moves relatively downstream and the radius of the vortex becomes larger. Therefore, a vortex expands radially inward between the shroud and the guide surface. Specifically, the flow of steam that reaches the outer peripheral surface of the shroud through the downstream surface of the fin flows downstream and radially inward from the downstream end of the shroud. That is, the flow direction of the steam flowing out from the recess becomes closer to the flow direction of the steam (main stream) flowing around the rotor blade body, and the mixing loss between them can be reduced.

According to the second aspect of the present invention, the reflux surface may extend linearly in a direction intersecting the axis in a cross-sectional view including the axis.

According to this configuration, since the return surface extends in a straight line that intersects with the axis, the time required for processing and processing are reduced compared to the case where the return surface is curved or composed of a plurality of surfaces, for example. Cost can be reduced.

According to a third aspect of the present invention, a steam turbine includes a rotating shaft rotating about an axis, a moving blade body extending radially outwardly from the rotating shaft, and a radially outer end portion of the moving blade body. a rotor blade having a shroud provided in a casing; a casing surrounding the rotor blade from the radially outer side and having a recess for accommodating the shroud on the inner peripheral side; and a facing surface of the recess facing the shroud. a fin that protrudes radially inward and forms a clearance between itself and the outer peripheral surface of the shroud, wherein the recess faces the axial downstream side of the clearance and extends radially outward toward the downstream side. and a reflux surface extending from the downstream and radially outer end of the guide surface to the surface of the fin facing the downstream side via the radially outer side of the opposing surface, The reflux surface includes a first reflux surface that extends radially outward and upstream from a radially outer end portion of the guide surface to a position radially outer than the opposing surface; a second reflux surface that extends radially inward toward the upstream side from the radially outer end of the reflux surface to the surface of the fin that faces the downstream side .

In this configuration, the return flow surface has a first return surface and a second return surface. The first reflux surface extends radially outward toward the upstream side, and the second reflux surface extends radially inward toward the upstream side. That is, the angle formed by the guide surface and the first reflux surface and the angle formed by the first reflux surface and the second reflux surface increase in a direction approaching an obtuse angle. As a result, compared to, for example, the case where the first and second reflux surfaces are flush with each other (that is, when the reflux surface is formed of only one surface), the It is possible to reduce the dead water area of the vortex formed in the In addition, the swirl center of the vortex moves further downstream. As a result, dissipation of vortex energy is suppressed, and mixing loss can be further reduced.

According to a fourth aspect of the present invention, a steam turbine comprises: a rotating shaft rotating about an axis; a moving blade body extending radially outward from the rotating shaft; a rotor blade having a shroud provided on an outer end thereof; a casing surrounding the rotor blade from the radially outer side and having a recess formed therein for accommodating the shroud; and a recess facing the shroud in the recess. and a fin that protrudes radially inward from the facing surface to form a clearance between itself and the outer peripheral surface of the shroud, and the recess faces the axially downstream side of the clearance and extends toward the downstream side. a guide surface extending radially outward according to the guide surface, and a reflux surface extending from the downstream and radially outer end of the guide surface to the downstream surface of the fin via the radially outer side of the opposing surface; and the reflux surface includes a first reflux surface that extends radially outward and upstream from a downstream radially outer end of the guide surface to a position radially outer than the opposing surface. , a second reflux surface extending further upstream from the radially outer end of the first reflux surface, and a downstream side of the fin from the radially outer end of the second reflux surface; a third reflux surface that extends radially inward toward the upstream side to the facing surface .

In this configuration, the return flow surface has a first return surface, a second return surface and a third return surface. The first reflux surface extends upstream as it goes radially outward, and the second reflux surface extends further upstream as it goes radially outward. The third reflux surface extends radially inward toward the upstream side. That is, the angle formed by the guide surface and the first return flow surface, the angle formed by the first return flow surface and the second return flow surface, and the angle formed by the second return flow surface and the third return flow surface are each approaching an obtuse angle. growing. Thereby, the dead water area of the vortex formed between the guide surface and the reflux surface can be further reduced. In addition, the swirl center of the vortex moves further downstream. As a result, dissipation of vortex energy can be further suppressed.

According to a fifth aspect of the present invention, the return surface bulges radially outward between the downstream and radially outer end of the guide surface and the downstream-facing surface of the fin. It may be curved.

According to this configuration, since the reflux surface is curved, the vortex flows along the reflux surface without forming a dead water area. In addition, the swirl center of the vortex moves further downstream. As a result, dissipation of vortex energy can be suppressed more effectively.

According to a sixth aspect of the present invention, the steam turbine comprises a rotating shaft that rotates about an axis, a moving blade body that extends radially outward from the rotating shaft, and a moving blade body that extends radially outward from the rotating shaft. a rotor blade having a shroud provided on an outer end thereof; a casing surrounding the rotor blade from the radially outer side and having a recess formed therein for accommodating the shroud; and a recess facing the shroud in the recess. and a fin that protrudes radially inward from the facing surface to form a clearance between itself and the outer peripheral surface of the shroud, and the recess faces the axially downstream side of the clearance and extends toward the downstream side. a guide surface extending radially outward according to the guide surface, and a reflux surface extending from the downstream and radially outer end of the guide surface to the downstream surface of the fin via the radially outer side of the opposing surface; and the upstream and radially inner end of the guide surface is positioned radially inward of the outer peripheral surface of the shroud.

In this configuration, the upstream and radially inner end of the guide surface is positioned radially inward of the outer peripheral surface of the shroud. As a result, between the outer peripheral surface of the shroud and the end of the guide surface, the vortex flows radially inward toward the downstream side. As a result, the flow direction of the steam flowing out from the recess becomes closer to the flow direction of the steam (main stream) flowing around the rotor blade body, and the mixing loss between them can be further reduced.

According to a seventh aspect of the present invention, the downstream and radially outer end of the guide surface may be positioned radially outwardly of the outer peripheral surface of the shroud.

According to this configuration, the downstream and radially outer end portion of the guide surface is located radially outer than the outer peripheral surface of the shroud. As a result, the flow of steam passing through the outer peripheral surface of the shroud and flowing downstream can be guided more smoothly radially outward and downstream. As a result, vortex formation can be further promoted.

According to the present invention, it is possible to provide a steam turbine with improved efficiency by reducing mixing loss.

1 is a schematic diagram showing the configuration of a steam turbine according to a first embodiment of the present invention; FIG. 1 is an enlarged view of a main part of a steam turbine according to a first embodiment of the invention; FIG. FIG. 4 is an enlarged view of a main part of a steam turbine according to a second embodiment of the invention; FIG. 5 is an enlarged view of a main part of a steam turbine according to a third embodiment of the invention; FIG. 11 is an enlarged view of a main part of a steam turbine according to a fourth embodiment of the invention;

[First embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. As shown in FIG. 1, a steam turbine 1 according to this embodiment includes a rotating shaft 2, a bearing device 3, a plurality of rotor blade stages 4, a casing 5, a plurality of stator blade stages 6, and fins 7 ( See FIG. 2). The rotating shaft 2 has a columnar shape extending along the axis O and is rotatable around the axis O. As shown in FIG. A bearing device 3 supports the shaft end of the rotary shaft 2 . The bearing device 3 has a pair of journal bearings 31 and only one thrust bearing 32 . A pair of journal bearings 31 are provided at both ends of the rotating shaft 2 in the direction of the axis O, respectively. Each journal bearing 31 supports a load in the radial direction with respect to the axis O. As shown in FIG. The thrust bearing 32 is provided only on one side in the axis O direction. The thrust bearing 32 supports a load in the axis O direction. A plurality of rotor blade stages 4 arranged at intervals in the direction of the axis O are provided on the outer peripheral surface of the rotating shaft 2 . Each rotor blade stage 4 has a plurality of rotor blades 40 that are circumferentially spaced about the axis O. As shown in FIG. The blade 40 has a blade platform 41 , a blade body 42 and a blade shroud 43 . The rotor blade platform 41 protrudes radially outward from the outer peripheral surface of the rotating shaft 2 . The rotor blade body 42 is attached to the outer peripheral surface of the rotor blade platform 41 . The rotor blade main body 42 extends in the radial direction and has an airfoil cross-sectional shape when viewed in the radial direction. A blade shroud 43 is attached to the radially outer end of the blade main body 42 .

The rotating shaft 2 and the rotor blade stages 4 (rotor blades 40) are surrounded by a casing 5 from the radially outer side. The casing 5 has a tubular shape centered on the axis O. As shown in FIG. A plurality of stator blade stages 6 arranged at intervals in the direction of the axis O are provided on the inner peripheral surface of the casing 5 . These stator blade stages 6 are alternately arranged with the rotor blade stages 4 in the axis O direction. Each stator vane stage 6 has a plurality of stator vanes 60 that are circumferentially spaced with respect to the axis O. As shown in FIG. The stator vane 60 has a stator vane main body 61 and a stator vane shroud 62 . The stator blade body 61 is attached to the inner peripheral surface of the casing 5 . The stator vane main body 61 extends in the radial direction and has an airfoil cross-sectional shape when viewed in the radial direction. A stator blade shroud 62 is attached to the radially inner end of the stator blade body 61 . A concave portion 8 that is recessed radially outward from the inner peripheral surface of the casing 5 is formed between a pair of adjacent stator vanes 60 on the inner peripheral surface of the casing 5 . The rotor blade shroud 43 described above is accommodated in this recess 8 .

An intake port 51 is formed at one end of the casing 5 in the direction of the axis O to introduce high-temperature, high-pressure steam supplied from the outside. An exhaust port 52 for discharging the steam that has passed through the casing 5 is formed at the other end of the casing 5 in the direction of the axis O. As shown in FIG. The steam introduced from the intake port 51 passes through the casing 5 from one side to the other side in the direction of the axis O, and passes through a plurality of rotor blade stages 4 (rotor blades 40) and a plurality of stator blade stages 6 (stator blades 40). The wings 60) are alternately struck. Rotational energy is thereby imparted to the rotating shaft 2 . The rotation of the rotating shaft 2 is extracted from the shaft end and used for driving a generator (not shown), for example. In the following description, the flow of steam flowing through the casing 5 from one side to the other side in the direction of the axis O will be referred to as the main stream Fm. Further, the side from which the main flow Fm flows (one side in the direction of the axis O) is called the upstream side, and the side from which the main flow Fm flows (the other side in the direction of the axis O) is called the downstream side.

Next, the configuration around the recess 8 will be described with reference to FIG. FIG. 2 is an enlarged view of the periphery of the recess 8 in a cross section including the axis O. As shown in FIG. As shown in the figure, the recessed portion 8 is recessed from the inner peripheral surface of the casing 5 (the inner peripheral surface 5A of the casing) in the shape of an angular groove radially outward. The recess 8 has a first region 81 located relatively upstream and a second region 82 located downstream of the first region 81 . Of the surfaces forming the first region 81, the surface facing the downstream side (that is, the surface located on the upstream side within the first region 81) is an upstream side wall surface 8A. Of the surfaces forming the first region 81, the surface facing radially inward is the facing surface 8B. The facing surface 8B extends along the axis O. As shown in FIG. The opposing surface 8B faces the outer peripheral surface of the moving blade shroud 43 (shroud outer peripheral surface 43A) from the radially outer side. In this embodiment, the upstream side wall surface 8A and the facing surface 8B are orthogonal to each other in a cross-sectional view.

A plurality (two) of casing-side fins 71 (fins 7) arranged at intervals in the direction of the axis O are provided on the facing surface 8B. Each casing-side fin 71 has a plate shape extending radially inward from the facing surface 8B. A radially widening gap (clearance C) is formed between the tip of each casing-side fin 71 and the shroud outer peripheral surface 43A. Furthermore, rotor-blade-side fins 72 (fins 7) are provided between the two casing-side fins 71 on the shroud outer peripheral surface 43A. The moving blade-side fins 72 are plate-shaped and extend radially outward from the shroud outer peripheral surface 43A. A radially widening gap (clearance C) is formed between the tip portion of the blade-side fin 72 and the facing surface 8B.

Next, the configuration of the second area 82 will be described. The second region 82 is separated from the first region 81 by sandwiching the casing-side fin 71 (downstream-side fin 71D) positioned most downstream of the two casing-side fins 71 . The second region 82 includes a second upstream side wall surface 71S that faces the downstream side of the downstream fin 71D, a guide surface S1 that faces the second upstream side wall surface 71S from the direction of the axis O, and a return flow path that faces radially inward. and a surface S2. A radially outer end portion L1 of the second upstream side wall surface 71S is positioned radially outwardly of the above-described facing surface 8B. Furthermore, the end L1 is located upstream of the downstream edge S1 of the rotor blade shroud 43 . The second upstream side wall surface 71S extends from the downstream side toward the upstream side as it goes radially inward from the end portion L1.

The guide surface S1 faces the downstream side of the clearance C formed between the tip of the downstream fin 71D and the shroud outer peripheral surface 43A. That is, the radial inner end portion L2 of the guide surface S1 is located radially inward of the shroud outer peripheral surface 43A. The guide surface S1 extends in a planar shape radially outward from the end L2 toward the downstream side. In other words, the guide surface S1 extends in a direction intersecting the casing inner peripheral surface 5A (or the axis O) in a cross-sectional view including the axis O. As shown in FIG. A downstream and radially outer end portion L3 of the guide surface S1 is positioned radially outwardly of the radially outer end portion L1 of the second upstream side wall surface 71S. The angle θ between the guide surface S1 and the axis O is preferably within the range of 15° to 75°. More desirably, the angle θ is in the range of 30° to 60°. Most preferably, the angle θ is between 40° and 50°.

A surface connecting the end portion L1 and the end portion L3 is a reflux surface S2. That is, the reflux surface S2 extends radially outward in a planar shape (linearly in a cross-sectional view) from the upstream end L1 toward the downstream end L3. In other words, the return surface S2 extends from the end L3 of the guide surface S1 to the second upstream side wall surface 71S via the radially outer side of the facing surface 8B.

Next, operation of the steam turbine 1 according to this embodiment will be described. When operating the steam turbine 1 , steam is supplied into the casing 5 from an external steam supply source (such as a boiler) through the intake port 51 described above. The steam forms a main stream Fm in the casing 5 from the upstream side to the downstream side. The main flow Fm collides alternately with the plurality of stator blade stages 6 and the plurality of rotor blade stages 4 on the way through the casing 5 . Stator vane stages 6 straighten the flow of steam. Rotational energy is imparted to the rotary shaft 2 by the collision of the rectified steam flow with the moving blade stages 4 .

Here, a part of the main stream Fm flows into the recess 8 described above to form a side stream Fs. More specifically, the side flow Fs flows into the first region 81 through the gap between the upstream side wall surface 8A of the recess 8 and the blade shroud 43 . Some components of the side flow Fs are blocked by the fins 7 described above. On the other hand, the remaining component of the side flow Fs flows through the clearance C between the casing-side fins 71 and the shroud outer peripheral surface 43A and the clearance C between the rotor-blade-side fins 72 and the opposing surface 8B to the second region on the downstream side. flow into 82; The secondary flow Fs that has flowed into the second region 82 collides with the guide surface S1 facing the clearance C, changes direction, and flows radially outward along the guide surface S1. The secondary flow Fs, which has reached the radially outer side through the guide surface S1, collides with the return surface S2, changes direction, and flows along the return surface S2 from the downstream side to the upstream side. After that, the secondary flow Fs flows from the radially outer side toward the inner side along the second upstream side wall surface 71S. That is, in the second region 82, a vortex V1 is formed that turns in the order of the guide surface S1, the reflux surface S2, and the second upstream side wall surface 71S. A small vortex (small vortex V2) different from the vortex V1 is formed at a corner formed by the guide surface S1 and the reflux surface S2. That is, this corner becomes a dead water area.

A part of the component Fp (that is, a part of the side flow Fs) of the vortex V1 merges (mixes) with the main flow Fm through the gap between the rotor blade shroud 43 and the guide surface S1. . Here, in the above configuration, the guide surface S1 extends radially outward toward the downstream side. As a result, compared to the case where the guide surface S1 spreads in the direction (radial direction) orthogonal to the axis O, for example, the component of the steam flow in the direction of the axis O increases, forming a stronger vortex V1. easier.

Further, the reflux surface S2 extends to the downstream side surface of the fin 7 via the radially outer side of the opposing surface 8B. As a result, the volume of the region in which the vortex V1 is formed can be increased compared to, for example, the case where the reflux surface S2 is located at the same position as the opposing surface 8B in the radial direction. As a result, the center of rotation of the vortex V1 moves relatively downstream, and the radius of the vortex V1 becomes larger. Therefore, the vortex V1 expands radially inward between the shroud and the guide surface S1. Specifically, the flow of steam that has reached the outer peripheral surface of the shroud through the downstream surface of the fin 7 flows downstream and radially inward from the downstream edge S1 of the shroud. That is, the flow direction of the steam flowing out from the recess 8 (second region 82) approaches the flow direction of the steam (main flow Fm) flowing around the rotor blade body 42, thereby reducing the mixing loss therebetween. As a result, the efficiency of the steam turbine 1 can be improved.

Furthermore, according to the above configuration, since the return surface S2 extends in a straight line that intersects with the axis O, the return surface S2 is curved or composed of a plurality of surfaces. , the time and cost required for processing can be reduced.

In addition, in the above configuration, the upstream and radially inner end portion L2 of the guide surface S1 is positioned radially inward of the outer peripheral surface of the shroud. As a result, between the shroud outer peripheral surface 43A and the end of the guide surface S1, the vortex V1 flows radially inward toward the downstream side. As a result, the flow direction of the steam flowing out from the recess 8 approaches the flow direction of the steam (main stream Fm) flowing around the rotor blade body 42, and the mixing loss between them can be further reduced.

In addition, according to the above configuration, the downstream and radially outer end portion L3 of the guide surface S1 is located radially outer than the shroud outer peripheral surface 43A. As a result, the flow of steam passing through the shroud outer peripheral surface 43A and flowing downstream can be guided more smoothly radially outward and downstream. As a result, formation of the vortex V1 can be further promoted.

The first embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention. For example, in the above embodiment, an example in which two casing-side fins 71 are provided and only one blade-side fin 72 is provided has been described. However, the numbers of these casing-side fins 71 and moving-blade-side fins 72 are not limited to the above, and can be changed as appropriate according to design and specifications.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said 1st embodiment, and detailed description is abbreviate|omitted. As shown in the figure, in this embodiment, the shape of the second region 82 is different from that in the first embodiment. More specifically, the reflux surface S22 has a first reflux surface S221 and a second reflux surface S222.

The first reflux surface S221 extends from the downstream and radially outer end portion L3' of the guide surface S21 to a position radially outer than the facing surface 8B. More specifically, the first reflux surface S221 extends upstream as it extends radially outward. In addition, this end L3' is positioned radially inward and downstream of the end L3 in the above-described first embodiment. That is, in this embodiment, the angle θ′ formed between the guide surface S21 and the casing inner peripheral surface 5A (or the axis O) is smaller than the angle θ in the first embodiment described above. The second reflux surface S222 extends from the radially outer end portion L4 of the first reflux surface S221 to the second upstream side wall surface 71S. The second reflux surface S222 extends radially inward toward the upstream side.

In the configuration according to this embodiment, the reflux surface S22 has the first reflux surface S221 and the second reflux surface S222. The first return flow surface S221 extends radially outward toward the upstream side, and the second return flow surface S222 extends radially inward toward the upstream side. That is, the angle formed by the guide surface S21 and the first reflux surface S221 and the angle formed by the first reflux surface S221 and the second reflux surface S222 become larger toward obtuse angles. As a result, for example, compared to the case where the first reflux surface S221 and the second reflux surface S222 are flush with each other (that is, when the reflux surface S22 is formed by only one surface), A dead water area formed between the surface S22 can be reduced. In addition, compared to the conventional configuration in which the guide surface S21 and the reflux surface S22 are orthogonal to each other, the center of rotation of the vortex V1 moves further downstream. As a result, the vortex V1 can be developed to a greater extent, and the dissipation of the energy of the vortex V1 can be suppressed to further reduce the mixing loss.

The second embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention. For example, in the above embodiment, an example in which two casing-side fins 71 are provided and only one blade-side fin 72 is provided has been described. However, the numbers of these casing-side fins 71 and moving-blade-side fins 72 are not limited to the above, and can be changed as appropriate according to design and specifications.

[Third embodiment]
Next, a third embodiment of the invention will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said each embodiment, and detailed description is abbreviate|omitted. As shown in the figure, in this embodiment, the shape of the second region 82 is different from those in each of the above embodiments. More specifically, the reflux surface S32 has a first reflux surface S321, a second reflux surface S322, and a third reflux surface S323.

The first reflux surface S321 extends from the downstream and radially outer end portion L3' of the guide surface S21 to a position radially outer than the facing surface 8B. More specifically, the first reflux surface S321 extends upstream as it extends radially outward. In addition, this end L3' is positioned radially inward and downstream of the end L3 in the above-described first embodiment. That is, in this embodiment, the angle θ′ formed between the guide surface S21 and the casing inner peripheral surface 5A (or the axis O) is smaller than the angle θ in the first embodiment described above. The second reflux surface S322 extends further radially outward from the radially outer end portion L4' of the first reflux surface S321. The second reflux surface S322 extends upstream as it goes radially outward. The angle formed by the second reflux surface S322 with respect to the axis O is smaller than the angle formed with the axis O by the first reflux surface S321. The third reflux surface S323 extends from the radially outer end portion L5 of the second reflux surface S322 to the second upstream side wall surface 71S. The third reflux surface S323 extends radially inward toward the upstream side.

In the configuration according to this embodiment, the return flow surface S32 has a first return flow surface S321, a second return flow surface S322, and a third return flow surface S323. The first reflux surface S321 extends upstream as it goes radially outward, and the second reflux surface S322 extends further upstream as it goes radially outward. The third reflux surface S323 extends radially inward toward the upstream side. That is, the angle formed by the guide surface S21 and the first reflux surface S321, the angle formed by the first reflux surface S321 and the second reflux surface S322, and the angle formed by the second reflux surface S322 and the third reflux surface S323 are Each increases in the direction approaching the obtuse angle. Thereby, the dead water area formed between the guide surface S21 and the reflux surface S32 can be further reduced. In addition, compared to the conventional configuration in which the guide surface S21 and the reflux surface S32 are perpendicular to each other, the center of rotation of the vortex V1 moves further downstream. As a result, the vortex V1 can be further developed, and the dissipation of the energy of the vortex V1 can be further suppressed.

The third embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention. For example, in the above embodiment, an example in which two casing-side fins 71 are provided and only one blade-side fin 72 is provided has been described. However, the numbers of these casing-side fins 71 and moving-blade-side fins 72 are not limited to the above, and can be changed as appropriate according to design and specifications.

[Fourth embodiment]
Next, a fourth embodiment of the invention will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said each embodiment, and detailed description is abbreviate|omitted. As shown in the figure, in this embodiment, the shape of the second region 82 is further different from the above embodiments. More specifically, the return flow surface S42 has a curved surface shape that expands radially outward between the downstream and radially outer end portion L3′ of the guide surface S21 and the second upstream side wall surface 71S. there is In other words, the return flow surface S42 extends from the end L3' via the downstream side of the end L3' and extends radially outward of the end L1 of the second upstream side wall surface 71S. It extends to L1. It is desirable that the reflux surface S42 be a continuous curved surface.

According to the configuration of the present embodiment, since the return surface S42 is curved, the vortex V1 smoothly flows along the return surface S42 without forming a dead water area. In addition, compared to the conventional configuration in which the guide surface S21 and the reflux surface S42 are orthogonal to each other, the center of rotation of the vortex V1 moves further downstream. As a result, the vortex V1 can be further developed, and the dissipation of the energy of the vortex V1 can be more effectively suppressed.

The fourth embodiment of the present invention has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present invention. For example, in the above embodiment, an example in which two casing-side fins 71 are provided and only one blade-side fin 72 is provided has been described. However, the numbers of these casing-side fins 71 and moving-blade-side fins 72 are not limited to the above, and can be changed as appropriate according to design and specifications.

Reference Signs List 1 Steam turbine 2 Rotating shaft 3 Bearing device 4 Rotor blade stage 5 Casing 6 Stationary blade stage 7 Fin 8 Recess 31 Journal bearing 32 Thrust bearing 40 Rotor blade 41 Rotor blade platform 42 Moving blade main body 43 Moving blade shroud 51 Intake port 52 Exhaust port 60 Stator blade 61 Stator blade main body 62 Stator blade shroud 71 Casing-side fin 72 Moving blade-side fin 81 First region 82 Second region 43A Shroud outer peripheral surface 5A Casing inner peripheral surface 71D Downstream fin 71S Second upstream side wall surface 8A Upstream side wall surface 8B Opposing surface C Clearance Fm Main flow Fs Side flow O Axes S1, S21 Guidance Surfaces S2, S22, S32, S42... Return surface S221, S321... First return surface S222, S322... Second return surface S323... Third return surface V1... Vortex V2... Small vortex

Claims (7)

a rotating shaft that rotates about an axis;
a blade having a blade body extending radially outwardly from the axis of rotation and a shroud provided at a radially outer end of the blade body;
a casing that surrounds the moving blades from the radially outer side and has a concave portion that accommodates the shroud on the inner peripheral side;
a fin that protrudes radially inward from a surface of the recess that faces the shroud and forms a clearance with the outer peripheral surface of the shroud;
with
The recess is
a guide surface facing the axially downstream side of the clearance and extending radially outward toward the downstream side;
Extending radially inward from the downstream and radially outer end of the guide surface toward the upstream side via the radially outer side of the opposing surface, the surface facing the downstream side of the fin a return surface connected to the radially outer end ;
has
In a region defined by the guide surface, the return surface, and the downstream-facing surface of the fin, a vortex is formed that turns in the order of the guide surface, the return surface, and the downstream-facing surface of the fin. steam turbine. a rotating shaft that rotates about an axis;
a blade having a blade body extending radially outwardly from the axis of rotation and a shroud provided at a radially outer end of the blade body;
a casing that surrounds the moving blades from the radially outer side and has a concave portion that accommodates the shroud on the inner peripheral side;
a fin that protrudes radially inward from a surface of the recess that faces the shroud and forms a clearance with the outer peripheral surface of the shroud;
with
The recess is
a guide surface facing the axially downstream side of the clearance and extending radially outward toward the downstream side;
a reflux surface extending from a downstream radially outer end of the guide surface to a downstream surface of the fin via a radially outer side of the opposing surface;
has
The reflux surface is
a first reflux surface extending radially outward and upstream from a downstream radially outer end of the guide surface to a position radially outer than the opposing surface;
a second reflux surface extending radially inward toward the upstream side from the radially outer end of the first reflux surface to the surface of the fin facing the downstream side;
a steam turbine. a rotating shaft that rotates about an axis;
a blade having a blade body extending radially outwardly from the axis of rotation and a shroud provided at a radially outer end of the blade body;
a casing that surrounds the moving blades from the radially outer side and has a concave portion that accommodates the shroud on the inner peripheral side;
a fin that protrudes radially inward from a surface of the recess that faces the shroud and forms a clearance with the outer peripheral surface of the shroud;
with
The recess is
a guide surface facing the axially downstream side of the clearance and extending radially outward toward the downstream side;
a reflux surface extending from a downstream radially outer end of the guide surface to a downstream surface of the fin via a radially outer side of the opposing surface;
has
The reflux surface is
a first reflux surface extending radially outward and upstream from a downstream radially outer end of the guide surface to a position radially outer than the opposing surface;
a second reflux surface extending further upstream from the radially outer end of the first reflux surface toward the radially outer side;
a third reflux surface extending radially inward toward the upstream side from the radially outer end of the second reflux surface to the surface of the fin facing the downstream side;
a steam turbine. a rotating shaft that rotates about an axis;
a blade having a blade body extending radially outwardly from the axis of rotation and a shroud provided at a radially outer end of the blade body;
a casing that surrounds the moving blades from the radially outer side and has a concave portion that accommodates the shroud on the inner peripheral side;
a fin that protrudes radially inward from a surface of the recess that faces the shroud and forms a clearance with the outer peripheral surface of the shroud;
with
The recess is
a guide surface facing the axially downstream side of the clearance and extending radially outward toward the downstream side;
a reflux surface extending from a downstream radially outer end of the guide surface to a downstream surface of the fin via a radially outer side of the opposing surface;
has
The steam turbine , wherein the upstream and radially inner end of the guide surface is located radially inward of the outer peripheral surface of the shroud . The steam turbine according to claim 1 or 4, wherein the return surface extends linearly in a direction intersecting the axis in a cross-sectional view including the axis. 5. The reflux surface according to claim 4 , wherein the return surface has a curved surface that bulges radially outward between the downstream and radially outer end of the guide surface and the downstream-facing surface of the fin. steam turbine. The steam turbine according to any one of claims 1 to 6, wherein a downstream and radially outer end portion of the guide surface is positioned radially outer than the outer peripheral surface of the shroud.

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