US20090148298A1

US20090148298A1 - Blade disk seal

Info

Publication number: US20090148298A1
Application number: US12/330,755
Authority: US
Inventors: J. Page Strohl; Anthony Petett; Robert J. Kraft
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2007-12-10
Filing date: 2008-12-09
Publication date: 2009-06-11

Abstract

An apparatus and method are disclosed for reducing the operating stresses in a disk of a gas turbine engine while providing a seal plate to minimize leakage of a cooling fluid from the blades positioned in the disk. The seal plate is fastened to a tang of one or more of the blades. The seal plate configuration can be utilized with a newly manufactured disk and blades or with a modification to an existing disk and blades. The disk, blade, and seal plate configuration reduce operating stresses in the disk that are caused by mechanical loading on the disk by one or more rotating blades.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to the Provisional Patent Application having Ser. No. 61/012,475 and filed on Dec. 10, 2007.

TECHNICAL FIELD

The present invention relates to gas turbine engines. More particularly, embodiments of the present invention relate to an apparatus and method for reducing stress in a blade disk while minimizing leakage of cooling fluids directed towards one or more blades.

BACKGROUND OF THE INVENTION

Gas turbine engines operate to produce mechanical work or thrust. Specifically, land-based gas turbine engines typically have a generator coupled thereto for the purposes of generating electricity. A gas turbine engine comprises a number of components including a compressor section which has a series of rotating compressor blades. The compressor, which receives air from an engine inlet, passes the air through the compressor, where the pressure of the air increases. The compressed air is then directed into one or more combustors where fuel is mixed with the compressed air and the mixture is ignited. The hot combustion gases are then directed into a turbine section, which is coupled by a shaft to the compressor section. The hot combustion gases pass through the turbine causing the turbine blades, which are attached to disks, to rotate, which also drives the compressor. Depending on the type of gas turbine engine, an electrical generator may also be coupled to the engine shaft for harnessing its mechanical output in order to generate electricity.
Referring to FIGS. 1 and 2, a portion of a disk 100, in accordance with a turbine of the prior art, is shown. The blades are typically held in the disk by a series of generally axially extending attachment surfaces 102. These attachment surfaces are machined into an outer surface 104 of the disk 100. The blades and disk have corresponding attachment surfaces such that when the disk rotates, the blade is held in place, in a radial direction, by the attachment surfaces. However, as the blades and disk rotate, the blades apply a substantial pulling load on the disk 100. This is due to the weight of the blades, their radial position relative to the engine centerline, and rotational speed of the disk. For example, for a turbine blade installed in a prior art disk configuration, such as the disk 100, with the disk rotating at approximately 3600 RPM, and the blade having a weight of approximately 17.5 lbs, a pulling load is created that results in a stress concentration of approximately 276 ksi in a corner between an attachment surface and a cooling channel of the disk. Such large stress concentrations have been known to exceed material capabilities at the disk operating temperatures and have led to cracking within the disk, failure of the disk, and engine failure.

SUMMARY

Embodiments of the present invention are directed towards a system and method for, among other things, reducing stress levels in a disk assembly while providing a seal between a portion of the disk and one or more blades for a gas turbine engine.
The present invention provides embodiments for a disk assembly of a gas turbine engine in which a seal plate is secured thereto in order to prevent leakage of cooling air that is directed to cool a blade installed in the disk. The assembly has a disk with generally axially extending slots for receiving one or more blades. In one embodiment, each blade in the disk has a tang that extends radially inward, and one or more seal plates positioned to receive and engage the tang. The tang of the blade is secured to a seal plate by a fastener.
In an alternate embodiment of the present invention, a method of providing a sealing configuration between tangs of one or more blades and a disk is provided. This embodiment can be utilized in a variety of disk configurations, including modifying an existing turbine disk to remove areas of high concentrated stress. The method includes making alterations to the tang of the blade in order for it to mate with a seal plate. These alterations include machining a flat surface into a bottom of the tang and drilling a through hole in the tang. Once the blade is placed in the slot of the disk, the seal plate is placed around a portion of the tang such that a fastener can be placed through the seal plate and the tang, thereby joining the seal plate and tang together.
In yet another embodiment, a seal plate capable of minimizing cooling fluid leakage between a disk and one or more blades is provided. In one embodiment, the seal plate has generally parallel first and second members that are connected by a leg with the first and second members each having through holes for receiving a fastener. The first and second members are spaced apart a distance sufficient to receive a blade tang therebetween.
Additional advantages and features of the present invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 depicts a perspective view of a portion of a disk in accordance with the prior art;

FIG. 2 depicts a cross section view taken through a slot of the disk of FIG. 1 in accordance with the prior art;

FIG. 3 depicts a cross section view taken through a slot of the disk of FIG. 1 in accordance with the prior art where a section of material to be removed is indicated;

FIG. 4 depicts a perspective view of a portion of a disk assembly in accordance with an embodiment of the present invention;

FIG. 5 depicts an elevation view of the disk assembly of FIG. 4 in accordance with an embodiment of the present invention;

FIG. 6 depicts an elevation view of a portion of a disk assembly in accordance with an alternate embodiment of the present invention;

FIG. 7 depicts a cross section view of a seal plate taken through the disk assembly of FIG. 5 in accordance with an embodiment of the present invention;

FIG. 8 depicts an exploded assembly view of the disk assembly depicted in FIG. 5 in accordance with an embodiment of the present invention;

FIG. 9 depicts a perspective view of a seal plate in accordance with an embodiment of the present invention;

FIG. 10 is a cross section view of the seal plate of FIG. 9 in accordance with an embodiment of the present invention.

FIG. 11 is a perspective view of a seal plate in accordance with an alternate embodiment of the present invention;

FIG. 12 is an alternate perspective view of the seal plate of FIG. 11;

FIG. 13 is a cross section view of the seal plate depicted in FIGS. 11 and 12 in accordance with an alternate embodiment of the present invention;

FIG. 14 is a cross section view of a seal plate in accordance with yet another embodiment of the present invention;

FIG. 15 is a detailed cross section view of the seal plate depicted in FIG. 14; and,

FIG. 16 is a perspective view of the seal plate depicted in FIGS. 14 and 15.

DETAILED DESCRIPTION

The subject matter of the present invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different components, combinations of components, steps, or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies.
Referring initially to FIG. 3, a portion of a disk 300 is depicted in cross section. The disk 300 has an outer circumferentially extending surface 302 and a center axis A-A. In operation, the disk 300 rotates about the center axis A-A. Depending on the engine geometry, the disk 300 can vary in a thickness 304. This thickness 304 can also vary for each stage of an engine. The disk 300 comprises a plurality of blade slots 306, as shown in FIGS. 4 and 5, with the blade slots 306 having a slot length 308 that extends through the thickness 304 proximate the outer circumferentially extending surface 302. The blade slots 306 are spaced generally equally about the outer circumferential extending surface 302.
One or more blades 310 are positioned within the blade slots 306 and extend radially outward from the disk 300. Referring now to FIGS. 4, 5, 7, and 8, the one or more blades 310 each comprise a root portion 312, an airfoil portion 314, and a tang 316. More specifically, the root portion 312 has a root length 318 that may or may not be substantially similar to the slot length 308. However, in order for the blade 310 to be secured within the disk 300 it is necessary for the root portion 312 to have a cross sectional profile that corresponds to the blade slot 306. That is, the root portion 312 has a series of attachment surfaces 313A that mate to attachment surfaces 313B of the blade slot 306. The cross sectional profile of the root portion 312 will be slightly undersized compared to the blade slot 306 to ensure that the blade 310 can slide into the blade slot 306, as shown in FIG. 5.
Referring to FIG. 7, the tang 316 is shown in greater detail. The tang 316 has a thickness 320 and extends radially inward opposite of the direction of the airfoil portion 314 and is spaced axially from the root portion 312 by a seal slot 322. The tang 316 of the blade 310 also has a hole 324 that extends through the thickness of the tang 316.
Turning to FIGS. 7-10, the disk assembly also incorporates one or more seal plates 326 that are positioned to receive the tang 316 of the blade 310 in order to provide one or more sealing surfaces. Use of the seal plate 326 is especially critical for blades 310 that receive some type of internal cooling, as is commonly found in a turbine section of a gas turbine engine. Without adequate sealing, the cooling fluid, which is typically air or steam, can leak out of a cooling channel and not provide sufficient cooling to the blade, resulting in blade overheating and possible premature blade failure.
Referring to FIGS. 9 and 10, the seal plate 326 comprises a first member 328 having a first thickness 330 and a second member 332 having a second thickness 334. As it can be seen from FIGS. 7 and 10, the first member 328 is generally parallel to the second member 332. In the embodiment shown, the first member 328 also has a height H1 that is greater than a height H2 of the second member 332, but the second thickness 334 is greater than the first thickness 330. Also, the first member 328 has one or more holes 336 that extends through the first thickness 330 and the second member 332 has one or more threaded holes 338 in the second thickness 332. It is necessary, for the embodiment shown, that the second thickness 334 be greater than the first thickness 330, since the hole 338 is threaded and a threaded hole requires additional thickness for the threads than does a through hole. The seal plate 326 also comprises a leg 333 that connects the first member 328 to the second member 332.
The disk 300 utilizes one or more fasteners 340 to secure the seal plate 326 to the tang 316 of the blade 310. Fasteners 340 are placed through the one or more holes 336 in the first member 328, through the hole 324 in the tang 316, and engages a set of threads 342 of the one or more threaded holes 338 in the second member 332. This arrangement is depicted in FIG. 7. When the threads of the fastener 340 engage corresponding threads 342 of the threaded hole 338, at least the second member 332 of seal plate 326 is drawn into contact with the tang 316 to provide a seal. Also, upon rotation of the disk 300 having one or more blades 310, angular momentum of the seal plate 326 causes a flat portion 344 of the leg 333 to move slightly radially outward and contact a corresponding flat surface 346 of the tang 316. This contact provides an additional sealing region.
As previously discussed, a sealing arrangement is required for blades which receive a supply of cooling fluid. While embodiments of this invention can be applied to a variety of blades and disk designs, including newly manufactured components, one particular embodiment in which this invention is applicable is with respect to a method of modifying an existing turbine disk having regions of excessive stress in an attachment area between a blade and the disk. For clarity purposes, the same figures will be used in describing this embodiment of the present invention that is directed towards modifying a turbine disk, as have been previously referenced.
As previously discussed, the turbine disk 300 has a plurality of blade slots 306 for receiving blades along its outer circumferential surface 302. However, this disk also contains a tangential cooling cavity 350 (see FIG. 3). The intersection of the cooling cavity 350 and blade slots 306, when combined with the radial pull associated with rotating blades 310, can create excessive stress concentrations at these intersections. If not alleviated, the stress concentrations can exceed the allowable stress levels for a particular material and operating temperature resulting in failure of the disk.
An alternate embodiment of the present invention applies the seal plate arrangement previously discussed to a modified blade disk, when the structure of the cooling cavity 350 adjacent to known high stress regions has been modified. Referring back to FIG. 3, a dashed line 352 indicates where a section of the disk, identified as 354, is to be removed. An elliptical cut is made to reduce any remaining stress concentrations in the disk 300. The blades 310 for that stage of the engine are also machined to place a flat surface 346 on the tang 316. Then, a through hole is drilled into the tang 316 of the blade 310.
Once modifications have been made to the disk 300 and blade 310, the blade 310 is then placed into the blade slot 306 of the now modified disk 300 and a seal plate 326 is slid at least partially around the tang 316 and into a seal slot 322 of the disk 300. Referring to FIG. 7, the seal plate 326 is placed adjacent to the blade 310 and the disk 300 such that the first member 328, which has a through hole 336, is placed adjacent to a first side 316A of the tang 316 while the second member 332, which has a threaded hole 338, is placed adjacent to a second side 316B of the tang 316. The second member 332 is placed into the seal slot 322 such that the through holes 336, 324, and 338 are in alignment. During such an alignment, the flat surface 346 of the tang 316 may also contact the flat surface 344 of the seal plate 326.
Once the seal plate 326 is positioned around the tang 316, a threaded fastener 340 is placed through the through hole 336 in the seal plate 326 and through the through hole 324 in the tang 316 such that the fastener 340 engages the threaded hole 338 in the second member 332 of the seal plate 326. The fastener 340 is then secured to the first member 328 by a means such as tack welding so as to prevent the fastener 340 from backing out and coming loose during engine operation.
Although this seal plate 326 has been described in use with a particular modification to a blade disk 300, as shown in FIG. 3, similar modifications can be applied to a variety of disk configurations. Also, the seal plate 326 can take on a variety of configurations. One such alternate embodiment of the seal plate is depicted in FIG. 6. For clarity purposes, similar numerical identifiers are used in FIG. 6 to denote similar features of other embodiments of the present invention. In this embodiment, the seal plate 626 extends circumferentially across a plurality of blades 610. In this embodiment, the seal plate 626 extends across three blades 610, but this alternate embodiment is not limited to spanning only three blades 610. The seal plate 626 can span a larger or smaller quantity of blades 610 and can use a single fastener 640, as depicted in FIG. 6, or multiple fasteners.
Depending on the blade construction, the seal plate geometry can vary to include additional members similar to members 328 and 332. Also, the spacing between the members 328 and 332 can vary and as a result, the length of the leg 333 will also vary. Furthermore, depending on the blade and disk configuration, it is possible that more than one seal plate 326 will be required. For example, multiple seal plates 326 can be used, with one at a forward end of a blade/disk assembly and another at an aft end of the blade/disk assembly.
While the seal plate 326 and fastener 340 have been described with respect to a threaded engagement, this is but one type of coupling. Alternate forms of fastening the seal plate 326 and the blade tang 316 together are envisioned as such, slight modifications to the seal plate 326 and/or blade tang 316 may be required. For example, depending on the fastener type, the hole 338 may not be threaded, but instead may be a through hole or a tapered hole so as to engage an alternate form of the fastener 340.
Although the present invention has been described in terms of a threaded fastener, the fastener 340 is not limited to this configuration. In fact, alternate sealing arrangements between the seal plate 326 and the blade tang 316 can be utilized, such as a snap fit or trapping the seal plate 326 between the tang 316 and the disk 310. Furthermore, the second member 332 may not have a hole 338. In this embodiment, a fastener can pass through the first member and the tang and contact the second member 332
An alternate embodiment of the present invention is shown in FIGS. 11-16. Referring initially to FIGS. 11-13, a first alternate embodiment of a seal plate 1100 is depicted. In this first alternate embodiment, a seal plate 1100 for minimizing a cooling fluid leakage between a portion of a disk 1102 and one or more blades 1104 is shown. The seal plate 1100 comprises a circumferentially extending base member 1106, a first vertical member 1108 that extends radially outward from an end of the circumferentially extending base member 1106. A second vertical member 1110 extends radially outward from the first vertical member 1108. The first and second vertical members are connected by an axial member 1112.
The circumferentially-extending member 1106 also includes an angled surface 1114 that mates to an angled surface 1116 of the blade tang 1118. During operation, as the blade 1104 rotates, the blade 1104 moves slightly radially outward away, from the disk 1102 due to the circumferential pull created by the blade weight and rotation. However, the blade 1102 is fixed in place radially by an attachment (not shown). The coverplate 1100, is secured to a blade tang 1118 by one or more pins 1120 that pass through respective openings in the coverplate 1100 and tang 1118. This securing means permits the coverplate 1100 to move slightly radially outward such that the angled surface 1114 of the coverplate comes into and maintains a line-on-line contact with the blade tang 1118.
Referring now to FIGS. 14-16, yet another alternate embodiment of the present invention is shown. The features of this alternate embodiment are similar to those described in FIGS. 11-13 and carry similar identifiers where common, and as such, only new and/or different features of this embodiment are described in more detail below.
In this alternate embodiment, the second vertical member 1110 further comprises a slot 1122 that contains a generally circumferentially-extending seal 1124 that has a circular cross section, such as a wire seal. The slot 1122 is formed from material removed or void from the radially outer portion of the second vertical member 1110. The circumferentially-extending seal 1124 extends the circumference of the disk 1102 to provide a supplemental seal to the angled surfaces 1114 and 1116.
The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope.
From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.

Claims

1. A disk assembly for a gas turbine engine comprising:

a disk having an outer circumferentially extending surface, a center axis, a thickness, and a plurality of blade slots having a slot length extending at least partially through the thickness, the plurality of blade slots are spaced generally equally about the outer circumferentially extending surface;

one or more blades positioned in each of the blade slots and extending radially outward from the disk, the one or more blades each having a root portion, an airfoil portion, and a tang;

one or more seal plates configured to receive the tang of the blade so as to secure the one or more seal plates to the tangs of the one or more blades;

wherein at least one seal is formed between the tang of the blade and the one or more seal plates.

2. The disk assembly of claim 1, wherein the root portion has a root length and a profile corresponding substantially to the blade slots.

3. The disk assembly of claim 1, further comprising one or more fasteners for securing the one or more seal plates to the tangs of the one or more blades.

4. The disk assembly of claim 3, wherein the tang has a thickness and extends radially inward and is spaced axially from the root portion by a seal slot, the tang also having a through hole.

5. The disk assembly of claim 4, wherein the seal plate comprises a first member having a first thickness and a second member having a second thickness, the first member being generally parallel to the second member and separated from the second member by a leg, the first member having one or more through holes in the first thickness and the second member having one or more holes in the second thickness.

6. The disk assembly of claim 5, wherein the leg of the seal plate contacts the tang upon rotation of the disk assembly.

7. The disk assembly of claim 5, wherein the one or more fasteners and the one or more holes in the second member are threaded such that when one or more fasteners are placed through the one or more holes in the first member, through the hole in the tang, the one or more fasteners engage with a corresponding one or more threaded holes in the second member.

8. The disk assembly of claim 7, wherein the one or more fasteners are positioned such that at least the second member of the one or more seal plates contacts the tang.

9. A seal plate for minimizing a cooling fluid leakage between a portion of a disk and one or more blades, the seal plate comprising:

a first member having a first thickness, a first height, a first width and a first through hole;

a second member having a second thickness, a second height, and a second width, where the second member is generally parallel to the first member; and

a leg connecting the first member to the second member, the leg having at least one flat portion; wherein

the seal plate is capable of being positioned to seal a joint between a portion of the disk and the one or more blades and is secured to the one or more blades by a fastener.

10. The seal plate of claim 9, wherein the first thickness is less than the second thickness and the first height is greater than the second height.

11. The seal plate of claim 9, wherein the second member further comprises a second through hole.

12. The seal plate of claim 9, wherein the first through hole has a constant diameter and the second through hole is threaded.

13. The seal plate of claim 12, wherein the fastener has threads that correspond to the threads of the second through hole.

14. The seal plate of claim 9, wherein the first and second widths are equal to or greater than a width of a slot in the disk.

15. A disk assembly for a gas turbine engine comprising:

a disk having an outer circumferentially extending surface, a center axis, a thickness, a hook portion, and a plurality of blade slots having a slot length extending at least partially through the thickness, the plurality of blade slots are spaced generally equally about the outer circumferentially extending surface;

one or more seal plates configured to engage the hook portion of the disk so as to secure the one or more seal plates to the tangs of the one or more blades;

wherein at least one seal is formed between the hook portion of the disk and the one or more seal plates.

16. The disk assembly of claim 15 further comprising a pin for securing the seal plate to the tang of the blade.

17. The disk assembly of claim 16, wherein the pin prevents circumferential movement of the seal plate relative to the blade.

18. The disk assembly of claim 15, wherein the seal is formed upon rotation of the disk assembly by centrifugal loads such that the one or more seal plates move radially outward and contact a portion of the hook portion of the disk.

19. The disk assembly of claim 18, wherein the seal is formed along corresponding chamfered surfaces of the hook portion and seal plates.

20. The disk assembly of claim 15, wherein the one or more plates comprises up to six plates.

21. A seal plate for minimizing a cooling fluid leakage between a portion of a disk and one or more blades, the seal plate comprising:

a circumferentially extending base member;

a first vertical member extending radially outward from an end of the circumferentially extending base member; and,

a second vertical member extending radially outward from the first vertical member; wherein

the first and second vertical members are connected by an axial member.

22. The seal plate of claim 21, wherein the circumferentially-extending base member has a portion with an angled surface.

23. The seal plate of claim 22, wherein the angled surface contacts the angled surface of a blade tang to form a sealing surface.

24. The seal plate of claim 21 further comprising one or more openings for a pin.

25. The seal plate of claim 24, wherein the pin attaches to the tang of the blade.

26. The seal plate of claim 21 further comprising a circumferentially-extending seal positioned between the second vertical member and the disk.