US20090191050A1

US20090191050A1 - Sealing band having bendable tang with anti-rotation in a turbine and associated methods

Info

Publication number: US20090191050A1
Application number: US12/019,002
Authority: US
Inventors: Brian D. Nereim; David M. Shaefer
Original assignee: Siemens Power Generations Inc
Current assignee: Siemens Energy Inc
Priority date: 2008-01-24
Filing date: 2008-01-24
Publication date: 2009-07-30

Abstract

The turbine includes a plurality of successive stages each having a rotatable disk and blades carried thereby. A pair of adjacent rotatable disks define an annular gap therebetween and have respective opposing sealing band receiving slots aligned with the annular gap. At least one of the rotatable disks has at least one notch therein coupled to the respective sealing band receiving slot, and a sealing band is in the opposing sealing band receiving slots to seal the corresponding annular gap. The sealing band includes at least one sealing strip and at least one movable locking tang carried thereby and extending into the at least one notch to define an anti-rotational feature for the sealing band.

Description

FIELD OF THE INVENTION

The present invention relates to the field of turbines, and, more particularly, to baffle seals within a turbine and related methods.

BACKGROUND OF THE INVENTION

In various multistage turbomachines used for energy conversion, such as turbines, a fluid is used to produce rotational motion. In a gas turbine, for example, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce the rotational motion. The turbine stages and compressor stages typically have stationary or non-rotary components, e.g. vane structures, that cooperate with rotatable components, e.g. rotor blades, for compressing and expanding the operational gases.
The rotor blades are typically mounted to disks that are supported for rotation on a rotor shaft. Annular disk arms extend from opposed portions of adjoining disks to define paired annular disk arms. A disk cooling air cavity is formed on an inner side of the paired annular arms between the disks of mutually adjacent stages, and a labyrinth seal may be provided on an inner surface of the stationary vane structures for cooperating with the annular arms to define a gas seal between a path for the hot combustion gases and the cooling air cavity. The paired annular arms extending from opposed portions of adjoining disks define opposing end faces located in spaced relation to each other.
Typically the opposing end faces may be provided with a slot for receiving a sealing strip, also known as a “Belly Band” seal, which bridges the gap between the end faces to prevent cooling air flowing through the cooling air cavity from leaking into the path for the hot combustion gases. The sealing strip may be formed of multiple segments, in the circumferential direction, that are interconnected at overlapped or stepped ends, as is described in U.S. Pat. No. 6,315,301, which is incorporated herein by reference.
When the seal strip comprises plural segments positioned adjacent to each other, in the circumferential direction, the seal strips may shift circumferentially relative to each other. Shifting may cause one end of a seal strip segment to increase the overlap with an adjacent segment, while the opposite end of the seal strip segment will move out of engagement with an adjacent segment, opening a gap for passage of gases through the seal strip. To prevent rotation of the seal strip segments, the segments may be provided with pins or anti-rotation blocks to cooperate with an adjacent disk surface for holding the segments stationary relative to the disk.
When a belly band wears or cracks, a repair is implemented that typically requires, e.g. as illustrated in FIG. 7, a replacement belly band 68 to be welded to an anti-rotation block 70. The welds 72 may be subject to cracking and may reduce the belly band life. The repair may require the cutting of additional slots in the disk arms to accept the anti-rotation block. The mass of the anti-rotation block may cause vibration issues, and accidental welding of the disk during repair may also occur. Also, such a repair process can take up to 2-3 days to finish which impacts outage times of the turbine.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of the present invention to provide an anti-rotation feature for a sealing strip in a turbine that does not require welding or the increased mass of an anti-rotation block.
This and other objects, features, and advantages in accordance with the present invention are provided by a turbine including a plurality of successive stages each comprising a rotatable disk and blades carried thereby, at least one pair of adjacent rotatable disks defining an annular gap therebetween and having respective opposing sealing band receiving slots aligned with the annular gap. At least one of the rotatable disks has at least one notch therein coupled to the respective sealing band receiving slot, and a sealing band is in the opposing sealing band receiving slots to seal the corresponding annular gap. The sealing band comprises at least one sealing strip, and at least one movable locking tang carried thereby and extending into the at least one notch to define an anti-rotational feature for the sealing band.
The at least one movable locking tang and the at least one sealing strip may be integrally formed as a monolithic unit, and the movable locking tang may be bendable with respect to adjacent portions of the at least one sealing strip. The at least one sealing strip may comprise at least one metal sealing strip. The at least one movable locking tang may have a distal end being movable from a coplanar position relative to adjacent portions of the at least one sealing strip to a bent position extending radially inwardly from adjacent portions of the at least one sealing strip. The distal end may be flush with adjacent side edges of the at least one sealing strip when in the coplanar position.
The at least one movable locking tang may have a generally rectangular shape with a proximal end connected to adjacent medial portions of the at least one sealing strip and opposing sides being spaced from adjacent portions of the at least one sealing strip. The at least one sealing strip may comprise a plurality thereof, e.g. four 90° sealing strips, having overlapping ends. Each sealing strip may carry a respective movable locking tang. The at least one pair of adjacent disks may further define a disk cooling fluid chamber positioned radially inwardly from the sealing band and a blade cooling chamber positioned radially outwardly from the sealing band.
In accordance with features of the present approach, when a sealing band wears or cracks, a repair may implemented that does not require a replacement band to be welded to an anti-rotation block. The repair does not require the cutting of additional slots in the disk arms to accept the anti-rotation block. The mass of an anti-rotation block that may cause vibration issues is avoided, and accidental welding of the disk during repair may also be eliminated. Also, the use of the present sealing band in such a repair process can reduce outage times of the turbine.
A method aspect is for installing a sealing band in a turbine including a plurality of successive stages each comprising a rotatable disk and blades carried thereby, at least one pair of adjacent rotatable disks defining an annular gap therebetween and having respective opposing sealing band receiving slots aligned with the annular gap. At least one of the rotatable disks has at least one notch therein coupled to the respective sealing band receiving slot. The method includes positioning the sealing band in the opposing sealing band receiving slots to seal the corresponding annular gap, the sealing band comprising at least one sealing strip and at least one movable locking tang carried thereby. The method further includes moving the at least one movable locking tang to extend into the at least one notch to define an anti-rotational feature for the sealing band.
The at least one movable locking tang and the at least one sealing strip may be integrally formed as a monolithic unit, and moving may include bending the at least one movable locking tang with respect to adjacent portions of the at least one sealing strip. Moving may comprise moving a distal end of the at least one movable locking tang from a coplanar position relative to adjacent portions of the at least one sealing strip to a bent position extending radially inwardly from adjacent portions of the at least one sealing strip. The distal end may be flush with adjacent side edges of the at least one sealing strip when in the coplanar position.
The at least one sealing strip may comprise a plurality thereof, and positioning the sealing band may comprise overlapping ends of the plurality of sealing strips in the opposing sealing band receiving slots. Each sealing strip may carry a respective movable locking tang that is moved into a corresponding notch. Furthermore, positioning the sealing band and moving the at least one movable locking tang may be performed without welding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a turbine including a sealing band in accordance with aspects of the present invention.

FIG. 2 is a perspective view of a section of adjacent disks and the associated sealing band of the turbine of FIG. 1.

FIG. 3 is a top view of the section of adjacent disks and the associated sealing band of FIG. 2.

FIG. 4 is a cross-sectional view of the section of adjacent disks and the associated sealing band of FIG. 2.

FIG. 5 is a cross-sectional perspective view of the section of adjacent disks and the associated sealing band of FIG. 2.

FIG. 6 is an enlarged perspective view of a section of the sealing band and associated movable locking tang of the turbine of FIG. 1.

FIG. 7 is a cross-sectional view of a conventional anti-rotation block and sealing band positioned between turbine disks in accordance with the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout to indicate similar elements in alternative embodiments.
Referring initially to FIG. 1, a portion of a turbine engine 10 is illustrated diagrammatically including adjoining stages 12, 14, each stage 12, 14 comprising an array of stationary vane assemblies 16 and an array of rotating blades 18, where the vane assemblies 16 and blades 18 are positioned circumferentially within the engine 10 with alternating arrays of vane assemblies 16 and blades 18 located in the axial direction of the turbine engine 10. The blades 18 are supported on rotor disks 20 which may be secured to adjacent disks, e.g. with spindle bolts. The vane assemblies 16 and blades 18 extend into an annular gas passage 24, and hot gases, e.g. from a combustion stage, are directed through the gas passage 24 past the vane assemblies 16 and blades 18.
Disk cavities 26, 28 are located radially inwardly from the gas passage 24. Purge air is preferably provided from cooling gas passing through internal passages in the vane assemblies 16 to the disk cavities 26, 28 to cool blades 18 and to provide a pressure to balance against the pressure of the hot gases in the gas passage 24. In addition, interstage seals comprising labyrinth seals 32 are supported at the radially inner side of the vane assemblies 16 and are engaged with surfaces defined on paired annular disk arms 34, 36 extending axially from opposed portions of adjoining disks 20.
An annular cooling air cavity 38 is formed between the opposed portions of adjoining disks 20 on an inner side of the paired annular disk arms 34, 36. The annular cooling air cavity 38 receives cooling air passing through disk passages to cool the disks 20. A sealing band 46 or “Belly Band” seal is positioned between the annular cooling air cavity 38 and the disk cavities 26, 28.
Referring to FIGS. 2-5, various views showing a segment of two adjoining disks 20 are illustrated for the purpose of describing the sealing band 46, it being understood that the disks 20 and associated disk arms 34, 36 define an annular structure extending the full circumference about a rotor centerline. The disk arms 34, 36 define respective opposed end faces 48, 50 located in closely spaced relation to each other. A circumferentially extending sealing band receiving slot 52, 53 is formed in each end face 48, 50, and at least one opening 54 extends from at least one of the outer surfaces 58, 59 of respective disk arms 34, 36, extending inwardly to a notch 80 and intersecting the corresponding slot 52, 53.
The sealing band 46 includes at least one sealing strip 60, which may be metal, for example. The sealing strip 60 is positioned within the slots 52, 53 defined in the opposed end faces 48, 50. The sealing strip 60 spans the gap between the end faces 48, 50 and defines a seal for preventing or substantially limiting flow of gases between the cooling air cavity 38 and the disk cavities 26, 28.
The sealing band 46 further includes an anti-rotation feature defined by one or more movable locking tangs 82 carried by the sealing strip 60. The movable locking tang is extended into the notch 80 to define the anti-rotational feature for the sealing band 46. The movable locking tang 82 and the sealing strip 60 may be integrally formed as a monolithic unit, perhaps as best illustrated in FIG. 6. The movable locking tang 82 may be bendable with respect to adjacent portions of the sealing strip 60. The sealing strip 60 and movable locking tang 82 may be made of metal, for example. The movable locking tang 82 may have a distal end 84 being movable from a coplanar position relative to adjacent portions 86, 87 of the sealing strip 60 to a bent position (FIG. 6) extending radially inwardly from the adjacent portions of the sealing strip. The distal end 84 may be flush with adjacent portions 86, 87 or side edges of the sealing strip 60 when in the coplanar position.
The movable locking tang 82 may have a generally rectangular shape with a proximal end 85 connected to adjacent medial portions 88, 89 of the sealing strip 60 and opposing sides 91, 92 being spaced from adjacent portions 86, 87 of the sealing strip. The sealing strip may comprise a plurality thereof, e.g. four 90° sealing strips, having overlapping ends, as would be appreciated by those skilled in the art. In this embodiment, each of the plurality of sealing strip 60 may carry a respective movable locking tang 82 to be moved into a corresponding one of a plurality of notches 80.
Accordingly, in a typical application, the sealing strip 60 may be provided as four separate sealing strip segments having overlapped ends (not shown) to form a continuous belly band seal about the circumference of the disk cooling fluid cavity 38. The anti-rotation feature of the movable locking tang 82 may be provided at the mid-span of each of the sealing strip segments to thereby locate each sealing strip segment relative to adjacent sealing strip segments.
As discussed above, a pair of adjacent disks 20 may further define a disk cooling fluid chamber 38 positioned radially inwardly from the sealing band 46 and one or more blade cooling chambers or cavities 26, 28 positioned radially outwardly from the sealing band. The sealing band 46 bridges the gap between the end faces 48, 50 of the disk arms 34, 36 to prevent cooling air flowing through the disk cooling fluid cavity 38 from leaking into the path 24 for the hot combustion gases.
The sealing band 46 provides a structure that may be incorporated into existing gas turbine engines and may not require modification of the disk arms 34, 36 to incorporate the sealing band. In particular, the present sealing band 46 is adapted to fit within the existing slots 52, 53 and make use of an existing notch 80 which may be currently provided on turbine engine disk arms 34, 36 and which may have been used to secure the prior art baffle seal 68 and associated anti-rotation block 70, such as is disclosed in FIG. 7.
In accordance with features of the present approach, when a sealing band wears or cracks, a repair may implemented that does not require a replacement band to be welded to an anti-rotation block. The repair does not require the cutting of additional slots in the disk arms to accept the anti-rotation block. The mass of an anti-rotation block that may cause vibration issues is avoided, and accidental welding of the disk during repair may also be eliminated. Also, the use of the present sealing band in such a repair process can reduce outage times of the turbine engine.
Field repair of the sealing strip 60 is typically performed by removing and replacing sealing strips through an opening (not shown) formed in the inner surfaces 56, 57 of the arms 34, 36. The sealing band 46 permits accurate placement by providing a structure having tolerances that may be accurately machined in a shop or factory environment, prior to transport to the field. Further, the installation of the disclosed sealing band 46 is simplified in that a weld connection utilized for the prior art installation is eliminated and replaced by the movable locking tang 82 that facilitates manipulation in the field, and that permits disassembly of the sealing band 46 if repositioning or removal of components of the assembly is required. The sealing band 46 may be provided as an original equipment manufacturer (OEM) part or may be installed as a replacement sealing band as discussed above.
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.

Claims

1. A turbine comprising:

a plurality of successive stages each comprising a rotatable disk and blades carried thereby, at least one pair of adjacent rotatable disks defining an annular gap therebetween and having respective opposing sealing band receiving slots aligned with the annular gap, at least one of the rotatable disks having at least one notch therein coupled to the respective sealing band receiving slot; and

a sealing band in the opposing sealing band receiving slots to seal the corresponding annular gap;

said sealing band comprising at least one sealing strip and at least one movable locking tang carried thereby and extending into the at least one notch to define an anti-rotational feature for the sealing band.

2. The turbine according to claim 1, wherein the at least one movable locking tang and the at least one sealing strip are integrally formed as a monolithic unit; and wherein said movable locking tang is bendable with respect to adjacent portions of the at least one sealing strip.

3. The turbine according to claim 2, wherein the at least one sealing strip comprises at least one metal sealing strip.

4. The turbine according to claim 1, wherein the at least one movable locking tang has a distal end being movable from a coplanar position relative to adjacent portions of the at least one sealing strip to a bent position extending radially inwardly from adjacent portions of the at least one sealing strip.

5. The turbine according to claim 4, wherein the distal end is flush with adjacent side edges of the at least one sealing strip when in the coplanar position.

6. The turbine according to claim 1, wherein the at least one movable locking tang has a generally rectangular shape with a proximal end connected to adjacent medial portions of the at least one sealing strip and opposing sides being spaced from adjacent portions of the at least one sealing strip.

7. The turbine according to claim 1, wherein the at least one sealing strip comprises a plurality thereof having overlapping ends.

8. The turbine according to claim 7, wherein each sealing strip carries a respective movable locking tang.

9. The turbine according to claim 1, according to claim 7 wherein the plurality of sealing strips comprises four 90° sealing strips.

10. The turbine according to claim 9, wherein the at least one movable locking tang comprises a respective movable locking tang carried by each of the four 90° sealing strips.

11. The turbine according to claim 1, wherein the at least one pair of adjacent disks further defines a disk cooling fluid chamber positioned radially inwardly from the sealing band and a blade cooling chamber positioned radially outwardly from the sealing band.

12. A sealing band for a turbine including a plurality of successive stages each comprising a rotatable disk and blades carried thereby, at least one pair of adjacent rotatable disks defining an annular gap therebetween and having respective opposing sealing band receiving slots aligned with the annular gap, at least one of the rotatable disks having at least one notch therein coupled to the respective sealing band receiving slot, the sealing band for positioning in the opposing sealing band receiving slots to seal the corresponding annular gap, the sealing band comprising:

at least one sealing strip; and

at least one movable locking tang carried by the at least one sealing strip for extending into the at least one notch to define an anti-rotational feature for the sealing band.

13. The sealing band according to claim 12, wherein the at least one movable locking tang and the at least one sealing strip are integrally formed as a monolithic unit; and wherein said movable locking tang is bendable with respect to adjacent portions of the at least one sealing strip.

14. The sealing band according to claim 12, wherein the at least one movable locking tang has a distal end being movable from a coplanar position relative to adjacent portions of the at least one sealing strip to a bent position extending radially inwardly from adjacent portions of the at least one sealing strip.

15. The sealing band according to claim 14, wherein the distal end is flush with adjacent side edges of the at least one sealing strip when in the coplanar position.

16. The sealing band according to claim 14, wherein the at least one sealing strip comprises a plurality thereof having overlapping ends.

17. The sealing band according to claim 16, wherein each sealing strip carries a respective movable locking tang.

18. A method for installing a sealing band in a turbine including a plurality of successive stages each comprising a rotatable disk and blades carried thereby, at least one pair of adjacent rotatable disks defining an annular gap therebetween and having respective opposing sealing band receiving slots aligned with the annular gap, at least one of the rotatable disks having at least one notch therein coupled to the respective sealing band receiving slot, the method comprising:

positioning the sealing band in the opposing sealing band receiving slots to seal the corresponding annular gap, the sealing band comprising at least one sealing strip and at least one movable locking tang carried thereby; and

moving the at least one movable locking tang to extend into the at least one notch to define an anti-rotational feature for the sealing band.

19. The method according to claim 18, wherein the at least one movable locking tang and the at least one sealing strip are integrally formed as a monolithic unit; and wherein moving comprises bending the at least one movable locking tang with respect to adjacent portions of the at least one sealing strip.

20. The method according to claim 18, wherein moving comprises moving a distal end of the at least one movable locking tang from a coplanar position relative to adjacent portions of the at least one sealing strip to a bent position extending radially inwardly from adjacent portions of the at least one sealing strip.

21. The method according to claim 20, wherein the distal end is flush with adjacent side edges of the at least one sealing strip when in the coplanar position.

22. The method according to claim 18, wherein the at least one sealing strip comprises a plurality thereof; and wherein positioning the sealing band comprises overlapping ends of the plurality of sealing strips in the opposing sealing band receiving slots.

23. The method according to claim 22, wherein each sealing strip carries a respective movable locking tang that is moved into a corresponding notch.

24. The method according to claim 22, wherein positioning the sealing band and moving the at least one movable locking tang are performed without welding.