JP6197985B2 - Seal structure and turbine device provided with the same - Google Patents

Description

  The present invention relates to a seal structure and a turbine apparatus including the seal structure.

  In a turbine apparatus such as a steam turbine, a gas turbine, an axial compressor, etc., as one of the pressure losses in the turbine, the top of the turbine blade and the inner peripheral surface of the housing (seal ring) facing the top close to the top There is a blade top leakage loss in which a working fluid such as steam or gas leaks through. In order to improve the turbine efficiency by reducing the blade top leakage loss, there are seal structures disclosed in Patent Documents 1 and 2 and the like.

  The seal structure disclosed in Patent Document 1 forms a step portion whose inner diameter changes stepwise along the turbine axial direction at the top portion (shroud portion, etc.) of the turbine blade, while facing the top portion of the turbine blade. A plurality of large cavities, small cavities, and seal fins are formed on the inner peripheral surface of the housing corresponding to the position of each step portion of the turbine blade top, and the main vortex is applied to the flow of leaked steam inside the large cavity. A separation vortex that rotates in the opposite direction to the main vortex of the leaked steam is formed by the small cavity and the seal fin, and the separation vortex leaks through the minute gap between the seal fin and the step part. It has a so-called labyrinth structure that reduces the blade top leakage loss by exerting a contraction effect that hinders the flow of steam.

  Further, the seal structure disclosed in Patent Document 2 is provided with a seal fin projecting from the top of the turbine blade, while forming a machinable abradable layer on the inner peripheral surface of the housing facing the top, Even if the top of the turbine blade contacts the inner peripheral surface of the housing during turbine operation, the abradable layer is cut to prevent damage, wear, vibration, etc. of the turbine blade and the housing. It has an abradable seal structure that can reduce the blade top leakage loss by setting the gap with the inner peripheral surface to a minimum.

  In order to further reduce the blade top leakage loss, it is preferable to have a seal structure having both a labyrinth structure and an abradable seal structure. In this case, for example, a seal structure 101 as shown in FIG. 9 is conceivable.

  That is, a plurality of seal fins 2a to 2d and cavity portions 3a to 3c are formed in a step shape on the top of the turbine blade 1, and the inner periphery of the housing 5 facing the seal fins 2a to 2d and the cavities 3a to 3c. Step portions 6a to 6d whose inner diameter changes stepwise along the turbine axial direction are formed on the surface. The step portions 6a to 6d include an axial surface 61 parallel to the axial direction of the turbine blade and a radial surface 62 (step surface) perpendicular to the turbine axial direction.

  The positions of the seal surfaces 21 of the seal fins 2a to 2d facing the working fluid flow direction F are shifted rearward in the flow direction F with respect to the radial surfaces 62 of the nearest step portions 6a to 6d. Then, the abradable layer 7 is formed on each axial surface 61 by thermal spraying or the like. As the abradable material, there is, for example, an MCrAlY alloy, and polyester and hexagonal boron nitride (h-BN) are mixed and sprayed to form a porous metal layer. Thereby, the clearance gap between the seal fins 2a-2d and the axial surface 61 can be minimized.

  In the seal structure 101 configured in this manner, the working fluid leaking between the axial surface 61 of the first step portion 6a and the tip of the first step seal fin 2a is radial in the second step portion 6b. The main vortex A is formed by colliding with the surface 62 and changing the flow direction on the bottom side of the cavity 3a. Further, after a part of this working fluid hits the radial surface 62 as described above, it forms a separation vortex B that spirals in the opposite direction toward the seal surface 21 of the second-stage seal fin 2b.

  Since the separation vortex B is a counter vortex having a swirl direction opposite to the swirl direction of the main vortex A, the flow of the working fluid attempting to leak between the seal fin 2a and the axial surface 61 by the separation vortex B. Is hindered and sealability is improved. Thereafter, the main vortex A and the separation vortex B are similarly generated in the cavities 3b and 3c, thereby reducing the leakage of the working fluid in a stepwise manner, combined with the sealing effect due to the provision of the abradable layer 7. Therefore, good sealing performance is exhibited, and the blade top leakage loss can be remarkably reduced.

JP 2011-208602 A JP 2008-223660 A

  In the seal structure 101 shown in FIG. 9, in order to effectively form the separation vortex B, the corner portion C formed by the axial surface 61 and the radial surface 62 of the step portions 6a to 6d has a sharp edge, Thus, it is desirable that the main vortex A is strongly wound on the seal surface 21 side of the seal fins 2a to 2d. As shown in an enlarged view in FIG. 10, when the edge of the corner C is rounded, the flow of the main vortex A does not get caught on the seal surface 21 side at the end of the corner C and passes through the corner C. The tendency to end up becomes stronger, and the separation vortex B is less likely to occur. For this reason, the sealing performance of the working fluid is deteriorated.

  In particular, when the abradable layer 7 is formed on the axial surface 61 by thermal spraying, it is difficult to uniformly form the abradable layer 7 up to the end portion (corner portion C) of the axial surface 61. The corner C tends to be rounded.

  The present invention has been made in view of such circumstances, and has a labyrinth structure and an abradable seal structure, and a simple seal structure in which the abradable layer is formed up to the corner of the labyrinth structure. With this structure, the labyrinth structure has a sealing structure that prevents the corners from being rounded and reliably forms a separation vortex, and improves the sealing performance of the working fluid to reduce the blade top leakage loss. An object is to provide a turbine device.

In order to achieve the above object, the present invention provides the following means.
That is, the seal structure according to the present invention has both a labyrinth structure and an abradable seal structure, and the labyrinth structure has one of two surfaces constituting a corner for forming a separation vortex of the working fluid. A turbine blade seal structure having an abradable layer and having seal fins extending toward the abradable layer, the edge of the other surface of the two surfaces constituting the corner portion The flange portion has a step surface projecting higher than the one surface along the surface direction of the other surface, facing the upstream side, and an inclined surface inclined toward the upstream side toward the projecting direction toward the downstream side. When, in the space defined between the circumferential surface facing the radially inner side of the other continuous to the inclined surface and the inclined surface, provided in contact with the inclined surface and the circumferential surface, said Shirufu Characterized in that it comprises a position corresponding to the tip of the emission and circumferentially extending abradable layer in which the grooves are formed, the.

  According to the above configuration, since the flange portion is formed at the corner portion forming the separation vortex of the working fluid in the labyrinth structure, the edge of the corner portion is kept sharp. In addition, since the abradable layer formed on one surface of the two surfaces constituting the corner portion is blocked by the flange portion, the end portion of the abradable layer is square as in the conventional case. The edges of the parts are not rounded. In this way, it is possible to prevent the corners of the labyrinth structure from being rounded, to reliably form a separation vortex, to improve the sealing performance of the working fluid, and to reduce the blade top leakage loss.

  According to the above configuration, the flange portion can be formed with a simple structure. Since the flange portion can be formed simultaneously with the turning of one surface, the manufacturing process of the housing or the like is not complicated and can be easily formed.

  According to the above configuration, the flange portion can be easily formed by a simple structure in which the plate member is fixed to the other surface. Moreover, the flange part can be retrofitted to an existing turbine apparatus that does not include the flange part for improvement.

  According to the said structure, since the axial direction dimension of the front-end | tip of a convex part is small, it becomes easy to design the position of a seal fin to the step surface side. Moreover, when the inclined surface is an inclined structure, the adhesion of the free-cutting material is improved and the durability against peeling is improved.

The flange portion may be formed by scraping a circumferential surface facing the radially inner side on the other side so that the flange portion remains.

The flange portion may be formed by a plate member fixed to the other.

The seal structure preferably includes a housing provided with the flange portion and divided in the circumferential direction, and a chamfer is provided at the radially inner end of the dividing portion mating surface of the housing.
According to the said structure, the adhesion degree of a free-cutting material can be raised and peeling during a driving | operation can be prevented.

  Moreover, the turbine apparatus according to the present invention is characterized by including the seal structure of each of the above aspects.

  According to this turbine apparatus, the corner portion of the labyrinth structure is prevented from being rounded to reliably form a separation vortex, thereby preventing the working fluid from leaking between the top of the turbine blade and the housing. Thus, the blade top leakage loss can be reduced and the turbine efficiency can be increased.

  As described above, according to the turbine blade seal structure according to the present invention and the turbine apparatus including the same, the labyrinth structure and the abradable seal structure are combined, and the abradable layer is formed up to the corner of the labyrinth structure. With a simple structure, the corners of the labyrinth structure can be prevented from being rounded and a separation vortex can be reliably formed, and the sealing loss of the working fluid can be improved and the blade top leakage loss can be reduced. .

1 is a schematic cross-sectional view showing a steam turbine according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the seal structure which shows 1st Embodiment of this invention. It is the longitudinal cross-sectional view which expanded the principal part of this invention. It is a longitudinal cross-sectional view of the seal structure which shows 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the seal structure which shows 3rd Embodiment of this invention. It is a perspective view of the housing which concerns on 4th Embodiment of this invention. It is VII-VII sectional drawing of FIG. 6, and is a figure which shows the shape of the division part matching surface of a housing. It is a figure which shows another form of the housing of 4th Embodiment of this invention. It is a longitudinal cross-sectional view of the seal structure which shows the prior art. It is the longitudinal cross-sectional view which expanded the vicinity of the corner | angular part of an axial surface and a radial surface shown in FIG.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. First, the configuration of the steam turbine according to the first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing a steam turbine 71 according to the first embodiment.

  The steam turbine 71 is provided in a hollow casing 72, a regulating valve 73 that adjusts the amount and pressure of steam S (fluid) flowing into the casing 72, and a casing 72. A shaft body 77 (rotor) that transmits power to a machine such as a generator, an annular stator blade group 78 held in the casing 72, an annular rotor blade group 79 provided on the shaft body 77, and the shaft body 77 And a bearing portion 80 that is rotatably supported around the CL.

  The casing 72 has an internal space hermetically sealed and a flow path for the steam S. The casing 72 has a ring-shaped partition plate outer ring 83 fixed to the inner wall surface thereof. A shaft body 77 is inserted through the partition plate outer ring 83. Further, the facing portion of the annular rotor blade group 79 in the partition plate outer ring 83 is the housing 5 (stator, see FIG. 2).

  A plurality of regulating valves 73 are attached to the inside of the casing 72, and each includes a regulating valve chamber 74 into which steam S flows from a boiler (not shown), a valve body 75, and a valve seat 76. When the valve seat 76 is separated from the valve seat 76, the steam flow path is opened so that the steam S flows into the internal space of the casing 72 through the steam chamber 84.

  The shaft body 77 includes a shaft main body 85 and a plurality of disks 86 extending in the radial direction from the outer periphery of the shaft main body 85. The shaft body 77 transmits rotational energy to a machine such as a generator (not shown).

  The annular stator blade group 78 includes a plurality of stator blades 87 provided on the inner surface of the casing 72 along the circumferential direction of the shaft body 77. The stationary blade 87 includes a blade main body 88 whose base end is held by a partition plate outer ring 83, and a ring-shaped hub shroud 89 that connects the radial tip ends of the blade main body 88 in the circumferential direction. . A shaft body 77 is inserted into the hub shroud 89 through a gap having a predetermined width in the radial direction. The six annular stator blade groups 78 configured in this way are provided at predetermined intervals in the axial direction of the shaft body 77, and convert the pressure energy of the steam S into velocity energy, and are adjacent to the downstream side. It guides to the turbine blade 1 (moving blade) side.

  The bearing portion 80 includes a journal bearing device 81 that receives the shaft body 77 in the radial direction and a thrust bearing device 82 that receives the shaft body 77 in the axial direction, and supports the shaft body 77 rotatably.

  The annular blade group 79 includes a plurality of turbine blades 1 along the circumferential direction of the shaft body 77. The six annular blade groups 79 configured as described above are respectively provided adjacent to the downstream side of the six annular stator blade groups 78. As a result, the annular stator blade group 78 and the annular rotor blade group 79, which are set in a single stage, are configured in a total of six stages along the axial direction.

FIG. 2 is a longitudinal sectional view of a seal structure showing the first embodiment of the present invention, and FIG. 3 is an enlarged view of a main part of the present invention.
This seal structure 11 is applied to, for example, a steam turbine apparatus, and has both a labyrinth structure and an abradable seal structure. In FIG. 2, the structure other than the vicinity of the corner C1 formed by the axial surface 61 and the radial surface 62 of the step portions 6a to 6d is the same as the conventional seal structure 101 shown in FIGS. Are denoted by the same reference numerals and description thereof is omitted.

  In the seal structure 11, in the labyrinth structure in which the main vortex A and the separation vortex B are formed in the steam as the working fluid in the cavities 3a to 3c, two surfaces constituting the corner portion C1 for forming the separation vortex B, That is, the abradable layer 7 (free-cutting material) is formed on the axial surface 61 of the axial surface 61 and the radial surface 62 by thermal spraying or the like, thereby adopting an abradable seal structure. Thereby, the space | interval of the axial surface 61 and seal fin 2a-2d can be minimized, and a sealing performance can be improved.

  As shown in an enlarged view in FIG. 3, a flange portion 8 </ b> A (convex portion) that protrudes higher than the axial surface 61 along the surface direction of the radial surface 62 is formed at the edge of the radial surface 62. . The flange portion 8A is formed by scraping the axial surface 61 so that a portion in the vicinity of the corner portion C1 remains with a predetermined width. The width of the flange portion 8A is designed within several mm.

  The protruding amount of the flange portion 8A from the axial surface 61 is set to about 1 mm to 3 mm so as to be equal to the film thickness of the abradable layer 7. Therefore, after the abradable layer 7 is formed on the axial surface 61, the surface of the abradable layer 7 and the inner peripheral surface of the flange portion 8A have the same height. When the abradable layer 7 is formed on the axial surface 61, the inner peripheral surface of the flange portion 8A is masked, and after the abradable layer 7 is sprayed onto the axial surface 61, the masking is peeled off.

  According to the seal structure 11 configured as described above, since the flange portion 8A is formed at the corner portion C1 forming the vapor separation vortex B in the labyrinth structure, the edge of the corner portion C1 is kept sharp. Further, since the abradable layer 7 formed by thermal spraying on the axial surface 61 is dammed by the flange portion 8A, the end portion of the abradable layer 7 is a corner portion C as in the conventional case (see FIG. 10). The edges are never rounded.

  Therefore, when the steam flowing along the flow direction F passes between the axial surface 61 and the tip of the seal fin 2a and forms the main vortex A inside the cavity 3a, the main vortex A is formed at the corner C1. Separation vortex B, which is a counter vortex, is peeled off by the edge, and the separation vortex B hinders the flow of steam that leaks between the axial surface 61 and the tip of the seal fin 2a, thereby improving the sealing performance. improves.

  Thus, by forming the flange portion 8A at the corner portion C1, the corner portion C1 is prevented from being rounded along with the formation of the abradable layer 7, and the peeling vortex B is reliably formed to seal the steam. The efficiency of the turbine apparatus can be improved by improving the performance and reducing the blade top leakage loss. In addition, since the thickness of the abradable layer 7 during spraying can be easily controlled by the flange portion 8A, the surface of the abradable layer 7 can be finished smoothly.

  Since the flange portion 8A is formed by scraping the axial surface 61 so that a portion in the vicinity of the corner portion C1 remains with a predetermined width, no additional parts or the like are required, and the flange portion has a very simple structure. The portion 8A can be formed. Since the flange portion 8A can be formed at the same time when the axial surface 61 is formed by turning, the manufacturing process of the housing 5 and the like can be easily formed without being particularly complicated.

  In FIG. 3, the thickness of the flange portion 8A is uniform. However, the flange portion 8A may be made thinner toward the tip while the radial surface 62 is kept flat. That is, the surface of the flange portion 8 </ b> A opposite to the radial surface 62 is an inclined surface so that the sandwich angle with the axial surface 61 is an obtuse angle. Thereby, the position of 8 A of flange parts and the front-end | tip part of seal fin 2a-2d can be closely approached to the axial direction of the turbine blade 1. FIG. Or the contact margin of the front-end | tip part of seal fin 2a-2d and the turbine blade 1 can be increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a longitudinal sectional view of a seal structure showing a second embodiment of the present invention.
Also in this seal structure 11B, the flange portion 8B is formed at the edge portion of the radial surface 62 constituting the corner portion C2. The flange portion 8 </ b> B is formed by fixing a thin metal plate member 10 to the radial surface 62 by welding, welding, or the like, and projecting the tip of the plate member 10 beyond the axial surface 61. The amount of protrusion of the flange portion 8B from the axial surface 61 is set to be equal to the film thickness of the abradable layer 7 as in the case of the flange portion 8A in the first embodiment. The plate member 10 may have a shape that is divided into a plurality of portions along the circumferential direction of the turbine shaft.

  The operation of the seal structure 11B configured in this way is the same as that of the seal structure 11 of the first embodiment. However, according to this seal structure 11B, the plate member 10 is fixed to the radial surface 62 in a very simple manner. The flange portion 8B can be easily formed by the structure, and the separation vortex B can be generated.

  Further, when the abradable layer 7 is formed by thermal spraying, the plate member 10 is positioned even if the thickness of the abradable layer 7 is not sufficiently high in the portion adjacent to the plate member 10. As a result, the corner C2 is prevented from being rounded, so that the separation vortex B can be reliably generated to prevent vapor leakage.

  Furthermore, it is possible to improve the existing turbine apparatus that does not include the flange portion by retrofitting the plate member 10 to form the flange portion 8B.

  Then, by providing the turbine apparatus with the seal structures 11 and 11B shown in the first and second embodiments, the corners of the labyrinth structure are prevented from being rounded, and a separation vortex is reliably formed. The working fluid is prevented from leaking between the blade top and the housing, and the blade top leakage loss can be reduced to increase the turbine efficiency.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a longitudinal sectional view of a seal structure showing a third embodiment of the present invention.
In the seal structure 11C, the flange portion 8C has a radial surface 62 and an inclined surface 63 that is inclined toward the upstream side toward the turbine blade 1 side toward the downstream side. That is, the flange portion 8C has a thin tip. The angle of the inclined surface 63 is set to about 15 ° to 30 ° with respect to the radial surface 62.

The amount of protrusion of the flange portion 8C from the axial surface 61 is set to be equal to the film thickness of the abradable layer 7 as in the flange portions 8A and 8B in the above embodiments.
The abradable layer 7 is in contact with the inclined surface 63 and the axial surface 61 in a space defined between the inclined surface 63 of the flange portion 8C and the axial surface 61 continuous to the inclined surface 63. It is provided and disposed so as to face the tips of the seal fins 2a to 2d.

According to the seal structure 11 </ b> C configured in this way, the axial dimension at the tip of the flange portion 8 </ b> C is small, so that the positions of the seal fins 2 a to 2 d can be more easily designed on the radial surface 62 side.
Further, since the inclined surface 63 has an inclined structure, the adhesion of the abradable layer 7 is improved and the durability against peeling is improved.

  As in the second embodiment, the flange portion 8C may be formed by fixing a thin metal plate member to the radial surface 62 by welding, welding, or the like.

[Fourth Embodiment]
FIG. 6 is a perspective view of the housing 5 in which the flange portion 8 is formed. The housing 5 has a division structure (for example, six divisions) in the circumferential direction.
A chamfer 52 is provided at the radially inner end of the dividing portion mating surface 51 of the housing 5 of the present embodiment. That is, as shown in FIG. 7, the dividing portion mating surface 51 is not formed in a flat shape, and has a structure in which an end portion on the inner peripheral side is inclined.

  When the abradable layer 7 is formed on the axial surface 61, as shown in FIG. 7, the abradable layer 7 is formed so as to be slightly raised in the circumferential direction, and then the plurality of housings 5 are coupled.

According to the seal structure configured as described above, the adhesion degree of the sprayed coating of the abradable layer 7 can be increased and peeling during operation can be prevented. That is, the reliability of the abradable seal can be improved.
Note that a structure in which a step 53 having a combination structure as shown in FIG. 8 is provided on the flat surface portion of the dividing portion mating surface 51 to further strengthen the coupling between the housings 5 may be adopted.

It should be noted that the present invention is not limited to the configuration of each of the embodiments described above, and can be appropriately modified or improved within the scope not departing from the gist of the present invention. The form is also included in the scope of the right of the present invention.
For example, the surface on which the abradable layer is provided may be a surface other than the axial surface, and the corner portion that generates the separation vortex is not necessarily a right angle.

Moreover, it is preferable to form a groove 90 extending in the circumferential direction in advance in the abradable layer 7 (see, for example, FIG. 5). The groove 90 is a slightly smaller groove than the range in which the seal fins 2a to 2d are supposed to move. By forming such a groove 90, the contact amount of the abradable layer 7 at the first start-up can be reduced, and the cutting resistance can be minimized.
In the above embodiment, the present invention is applied to a condensing steam turbine. However, the present invention can also be applied to other types of steam turbines such as a two-stage extraction turbine, an extraction turbine, and an air-mixing turbine.
Furthermore, in the said embodiment, although this invention was applied to the steam turbine, it can be applied also to a gas turbine, Furthermore, this invention is applicable to all the apparatuses which have a rotary blade.

2a to 2d Seal fins 3a to 3c Cavity part 5 Housing (stator)
6a-6d Step part 7 Abradable layer (free cutting material)
8A, 8B Flange (convex)
DESCRIPTION OF SYMBOLS 10 Plate member 11, 21 Seal structure 21 Seal surface 51 Split part matching surface 52 Chamfer 61 Axial surface (surface which comprises corner | angular part, peripheral surface)
62 Radial surface (surface composing corners, step surface)
63 Inclined surface A Main vortex B Separation vortex C1, C2 Corner

Claims (5)

Combines labyrinth structure and abradable seal structure,
In the labyrinth structure, an abradable layer is formed on one of two surfaces constituting a corner for forming a separation vortex of the working fluid, and a seal fin extending toward the abradable layer is provided. A turbine blade seal structure comprising:
The edge of the other surface of the two surfaces constituting the corner portion protrudes higher than the one surface along the surface direction of the other surface, the step surface facing the upstream side, and the downstream side A flange portion having an inclined surface that inclines toward the upstream side toward the protruding direction ,
Provided in a space defined between the inclined surface and the circumferential surface facing the radially inner side of the other side that is continuous with the inclined surface so as to be in contact with the inclined surface and the peripheral surface, and the tip of the seal fin And an abradable layer in which a groove extending in the circumferential direction is formed at a position corresponding to .   2. The seal structure according to claim 1, wherein the flange portion is formed by scraping a circumferential surface facing the radially inner side at the other side so that the flange portion remains.   The seal structure according to claim 1, wherein the flange portion is formed by a plate member fixed to the other. The flange portion is provided, and includes a housing divided in the circumferential direction,
The seal structure according to any one of claims 1 to 3, wherein a chamfer is provided at a radially inner end portion of the dividing portion mating surface of the housing.   A turbine apparatus comprising the seal structure according to claim 1.

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