Title:
Replaceable blade tip shroud
Kind Code:
A1


Abstract:
One embodiment of the present invention is a blade with a replaceable blade tip shroud that includes an airfoil shaped spar extending from a leading edge to a trailing edge between a root end and a tip end. It can also include a plurality of tiles coupled to an exterior of the spar; a tip shroud positioned to overlap at least a portion of the tip end of the spar; and means for anchoring the tip shroud to the tip end of the spar.



Inventors:
Dierksmeier, Douglas D. (Franklin, IN, US)
Heffernan, Tab M. (Plainfield, IN, US)
Application Number:
12/069512
Publication Date:
08/13/2009
Filing Date:
02/11/2008
Assignee:
Rolls-Royce North American Technologies, Inc.
Primary Class:
Other Classes:
416/236R, 416/241B
International Classes:
F01D5/20; F01D5/14
View Patent Images:



Primary Examiner:
MCDOWELL, LIAM J
Attorney, Agent or Firm:
KRIEG DEVAULT LLP (ONE INDIANA SQUARE, SUITE 2800, INDIANAPOLIS, IN, 46204-2079, US)
Claims:
What is claimed is:

1. A blade with a replaceable blade tip shroud, comprising: a spar extending from a leading edge to a trailing edge between a root end and a tip end; a plurality of tiles coupled to an exterior of the spar; a tip shroud positioned to overlap at least a portion of the tip end of the spar; and means for anchoring the tip shroud to the tip end of the spar.

2. The blade of claim 1, wherein the spar is airfoil shaped.

3. The blade of claim 2, wherein the tip shroud overlaps the entire tip end of the spar, and wherein the tip shroud is configured to retain at least one of the tiles in place against movement from the root end toward the tip end.

4. The blade of claim 2, wherein the tip shroud includes at least one groove to receive the means for anchoring the tip shroud to the tip end of the spar.

5. The blade of claim 4, wherein the tip end of spar also includes at least one groove to receive the means for anchoring the tip shroud to the tip end of the spar.

6. The blade of claim 5, wherein the spar is metal and wherein the tip shroud is metal.

7. The blade of claim 5, wherein the spar is metal and wherein the tip shroud is ceramic.

8. An apparatus comprising a shroud tip held on a tip end of an airfoil shaped spar by a retaining clip positioned within a pair of grooves on the spar and a corresponding pair of grooves in the shroud tip.

9. The apparatus of claim 8, wherein the retaining clip extends from a leading edge of the airfoil shaped spar toward a trailing edge of the airfoil shaped spar.

10. The apparatus of claim 9, wherein the pair of grooves extends from a leading edge of the spar toward a trailing edge of the spar, and wherein the pair of grooves do not extend all the way to the trailing edge.

11. The apparatus of claim 9, wherein the retaining clip is airfoil shaped.

12. The apparatus of claim 8, further comprising a plurality of ceramic tiles coupled to the spar.

13. The apparatus of claim 12, wherein the shroud tip overlaps at least one of the plurality of ceramic tiles and retains it in place against movement toward the tip end.

14. The apparatus of claim 8, wherein the spar is metal and the shroud tip is selected from the group consisting of a metal and a ceramic.

15. The apparatus of claim 14, wherein the shroud tip is metal, and wherein the shroud tip is a different metal than the spar.

16. A gas turbine engine blade with a replaceable tip shroud, comprising: an airfoil shaped spar extending radially between a hub end and a tip end, the spar extending substantially axially between a leading edge and a trailing edge; a tip shroud positioned to at least partially radially overlap the tip end of the airfoil shaped spar; a retaining member extending from the leading edge toward the trailing edge, the retaining member radially overlapping both the tip shroud and the airfoil shaped spar.

17. The blade of claim 16, wherein the tip shroud includes a first pair of channels shaped to receive the retaining member, and wherein the tip end of the spar includes a corresponding second pair of channels shaped to receive the retaining member.

18. The blade of claim 17, further comprising a plurality of tiles coupled to the spar.

19. The blade of claim 18, wherein the tip shroud overlaps the entire tip end of the spar, and wherein the tip shroud is configured to retain at least one of the plurality of tiles in place against movement from the root end toward the tip end.

20. The blade of claim 19, wherein the retaining member is an airfoil shaped clip with a pair of prongs, and wherein the prongs extend from the leading edge toward the trailing edge.

21. The blade of claim 20, wherein the spar is metal and the tip shroud is selected from the group consisting of a metal and a ceramic.

Description:

BACKGROUND

The present invention relates generally to blade tip shrouds and more particularly, but not exclusively, to a retaining system for retaining a blade tip shroud to a turbine blade in a gas turbine engine. Although, the present invention was developed for use in gas turbine engines, certain applications may be outside this field.

Blade tip shrouds typically wear during operation in gas turbine engines and require replacement. Current blade tip shrouds have issues including, for example, those respecting complexity of geometry, manufacturing cost, assembly time, limitations on shroud materials, ease of replacement, and fatigue life of the replacement. Thus, there is a need for the development of technology for removable blade tip shrouds within a gas turbine engine. The present invention satisfies this need in a novel and unobvious way.

SUMMARY

One embodiment of the present invention is a blade with a replaceable blade tip shroud that includes an airfoil shaped spar extending from a leading edge to a trailing edge between a root end and a tip end. It also includes a plurality of tiles coupled to an exterior of the spar; a tip shroud positioned to overlap at least a portion of the tip end of the spar; and means for anchoring the tip shroud to the tip end of the spar.

In one refinement the tip shroud overlaps the entire tip end of the spar, and the tip shroud is configured to retain at least one of the tiles in place against movement from the root end toward the tip end.

In another refinement the tip shroud includes at least one groove shaped to receive the means for anchoring the tip shroud to the tip end of the spar.

In another refinement the tip end of spar also includes at least one groove shaped to receive the means for anchoring the tip shroud to the tip end of the spar.

In another refinement the spar is metal and the tip shroud is metal.

In another refinement the spar is metal and the tip shroud is ceramic.

Another embodiment of the present invention is an apparatus including a shroud tip held on a tip end of an airfoil shaped spar by a retaining clip positioned within a pair of grooves on the spar and a corresponding pair of grooves in the shroud tip.

In one refinement the retaining clip extends from a leading edge of the airfoil shaped spar toward a trailing edge of the airfoil shaped spar.

In another refinement the pair of grooves extends from a leading edge of the spar toward a trailing edge of the spar, and the pair of grooves do not extend all the way to the trailing edge.

In another refinement the retaining clip is airfoil shaped.

In another refinement a plurality of ceramic tiles are coupled to the spar.

In another refinement the tip shroud overlaps at least one of the plurality of tiles and retains it in place against movement toward the tip end.

In another refinement the spar is metal and the tip shroud is selected from the group consisting of a metal and a ceramic.

In another refinement the tip shroud is metal, and the tip shroud is a different metal than the spar.

Another embodiment of the present invention is a gas turbine engine blade with a replaceable tip shroud, including an airfoil shaped spar extending radially between a hub end and a tip end. The spar extends substantially axially between a leading edge and a trailing edge. The blade also includes a tip shroud positioned to at least partially radially overlap the tip end of the airfoil shaped spar. A retaining member extends from the leading edge toward the trailing edge. The retaining member radially overlaps both the tip shroud and the airfoil shaped spar.

In one refinement the tip shroud includes a first pair of channels shaped to receive the retaining member, and the tip end of the spar includes a corresponding second pair of channels shaped to receive the retaining member.

In another refinement a plurality of tiles are coupled to the spar.

In another refinement the tip shroud overlaps the entire tip end of the spar. The tip shroud is configured to retain at least one of the plurality of tiles in place against movement from the root end toward the tip end.

In another refinement the retaining member is an airfoil shaped clip with a pair of prongs. The prongs extend from the leading edge toward the trailing edge.

In another refinement the spar is metal and the tip shroud is selected from the group consisting of a metal and a ceramic.

One form of the present invention contemplates a replaceable blade tip shroud for a blade. Other forms of the present invention contemplate unique apparatuses, systems, devices, hardware, methods, and combinations of these for defining a replaceable blade tip shroud for a gas turbine engine. Further embodiments, forms, objects, features and aspects of the present inventions shall become apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

FIG. 1 is an illustrative schematic representation of a gas turbine engine.

FIG. 2 is a perspective view of a gas turbine engine blade according to an embodiment of the present invention.

FIG. 3 is a partial cross sectional view of a gas turbine engine blade according to an embodiment of the present invention.

FIG. 4 is a top cross sectional view of a gas turbine engine blade according to an embodiment of the present invention.

FIG. 5 is a top view of a retaining clip according to an embodiment of the present invention.

DETAILED DESCRIPTION

For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

With reference to FIG. 1, there is illustrated a schematic representation of a gas turbine engine 10. This non-limiting depiction of gas turbine engine 10 includes a compressor section 20, a combustor section 30, and a turbine section 40. A person of ordinary skill in the art should appreciate that there are a multitude of ways in which the gas turbine engine components may be linked together. For instance, the engine may include a fan stage, a nozzle and/or additional compressors and turbine stages may be added with intercoolers connecting between the compressor stages. The present inventions are contemplated as being applicable with virtually all types and configurations of gas turbine engines.

The gas turbine engines contemplated herein are applicable for use in aircraft, as industrial power plants, and as propulsion systems in vehicles and vessels. Industrial power plant applications include, for example, pumping sets for gas and oil transmission lines and electricity generation systems. The term “aircraft” is generic and includes helicopters, airplanes, missiles, unmanned space devices, transatmospheric vehicles and other substantially similar devices.

Turbine section 40 includes at least one rotor or disk 50 having a plurality of turbine blades coupled thereto. A rotatable shaft 60 is located within a mechanical housing/case 70 of the turbine section 40 and is coupled to the rotor 50. The rotor 50 and the shaft 60 may also be integrated together into a unitary component. One form of the present invention contemplates that the rotatable shaft 60 and the rotor 50 are supported by a plurality of bearings. As the hot exhaust gas passes from the combustor section 30 the plurality of turbine blades rotate as the gas expands and functions to extract work from the hot exhaust flow. While the present disclosure will be generally described with reference to a turbine blade it is contemplated that forms of the present invention will be applicable to other gas turbine engine components including, but not limited to, fan blades and compressor blades.

Referring now to FIG. 2, there is illustrated a non-limiting perspective view of a gas turbine engine blade 100. The present invention contemplates a variety of blade designs and geometries. Each turbine blade 100 includes an airfoil 120 that rotates with the disk 50 (not shown in FIG. 2). Each airfoil 120 extends between a leading edge 130 and a trailing edge 140 in a stream wise direction and between an inner shroud or platform 150 and an outer or tip shroud 160 in a spanwise direction. The airfoil 120 extends radially outward from an outer surface 170 of the platform 150 from a hub end 180 toward a tip end 190. The airfoil 120 is preferably attached to the platform 150 proximate the hub end 180 of the airfoil 120. It is contemplated that the airfoil 120 can be integrally formed with the platform 150 through a casting process or the like or alternatively may be mechanically joined via welding, brazing or by any other joining method known to those skilled in the art. However, airfoils that are separable from the platform are also contemplated herein.

As described in further detail below, tip shroud 160 is preferably removably attached to the airfoil 120 proximate the tip end 190 of the airfoil 120. The tip shroud 160 includes an inner surface 200 and an outer surface 210. The outer surface 210 of the tip shroud 160 preferably includes at least one seal 220, and in this particular embodiment includes two seals 220. The seals 220 are preferably knife seals, and minimize leakage of working fluid from an outer flow path of air in the turbine section 40. Additionally, the seals 220 preferably include an abradable material layer 222 that is contactable with a housing (not shown in FIG. 2) to provide a relatively tight seal. Other forms of the present invention contemplate a layer of material or a seal such as a blade track seal attached to the housing to prevent direct contact between the abradable material layer 222 and the mechanical housing. Over time, the abradable material layer 222 may degrade from direct contact with the housing or the layer affixed to the housing and require repair or replacement. It is contemplated that the tip shroud 160 may be formed of a variety of materials including, but not limited to, ceramic, intermetallic, ceramic matrix composite, metallic, and a thermal barrier coated material. Additionally, at least one form of the present invention contemplates that the abradable material layer 222 is formed from a different material than the tip shroud 160.

As partially described previously, each blade 100 is attached to the rotor or disk 50 (not shown in FIG. 2) with an attachment member 230 located inward from an inner surface 240 of the platform 150. The attachment member 230 includes a connecting joint 250 that connects the turbine blade 100 and the turbine disk 50. One form of the present invention contemplates that the connecting joint 250 is formed from a common connection such as a dovetail joint, or as this particular embodiment illustrates, a “fir tree” design. Other forms contemplate different attachments than a dovetail or fir tree joint known to those having ordinary skill in the art.

As shown in FIG. 3, the airfoil 120 includes a spar or structural member 262. The spar 262 includes an exterior surface 320 and extends between a root end (not shown) and a tip end 330. The spar 262 preferably has an outer profile that corresponds to an airfoil shape. In another form, the outer profile of the spar 262 does not correspond to an airfoil shape. The spar 262 is preferably formed of a material suitable for operating within the environment of a turbine section of a gas turbine engine. In one form of the present invention, the spar 262 is formed of a heat-resistant superalloy composition. There are various types of superalloy compositions including, but not limited to, nickel-based or cobalt-based superalloy compositions. The spar member 262, in one form, has a unitary cast configuration. However, alternative embodiments of the spar 262 contemplate an assembly of cast components and/or wrought components. The spar 262 may be one of an equiax, directionally solidified or a single crystal structure. In still another form, the spar 262 is a cast integral single crystal structure. Further, the present inventions contemplate that the spar 262 may be formed of material appropriate for use in the compressor section 20 of the gas turbine engine 10.

Referring now to FIGS. 3-5, the tip shroud 160 is preferably removably coupled to the airfoil 120 by a retaining assembly 256. The retaining assembly 256 includes a retainer receiving portion defined by a pair of retaining channels or grooves 264 formed in the spar 262 of the airfoil 120, a pair of retaining channels or grooves 266 formed in the tip shroud 160, and a retaining member 268. A retainer receiving portion is formed by aligning the first retaining channels 264 with the second retaining channel 266. The retainer receiving portion preferably extends from the leading edge 130 to the trailing edge 140 and is operable to receive the retaining member 268. The retaining member 268 is preferably in the form of a clip including a tip portion 270 and a pair of legs or prongs 272 (see FIG. 5). The retaining member 268 is preferably inserted or fed into the leading edge side of the retainer receiving portion 260. Once partially inserted, the legs 272 extend around the spar 262 anchoring the tip shroud 160 to the airfoil 120. When inserted, the legs 272 preferably extend from the leading edge 130 to the trailing edge 140. In one form the retaining member 268 extends entirely to the trailing edge 140, however in another form the retaining member 268 extends only a portion of the distance from the leading edge 130 to the trailing edge 140. The retaining member 268 preferably has an airfoil shape. However, the present application contemplates retaining member 268 having a variety of shapes and is not limited to an airfoil shape unless specifically provided to the contrary. In one form of the present invention, a retaining member pushout access 274 is provided in a trailing edge cooling channel 276 of the airfoil 120 to facilitate removal of the retaining member 268. The tip shroud 160 is preferably replaced when the abradable material layer 222 reaches a certain wear level. It should be appreciated that the wear level may be chosen based on maintenance standards or other factors known to those having ordinary skill in the art. Additionally, the retaining assembly 256 allows the tip shroud 160 to be formed from a similar or different material than the airfoil 120. In some forms of the present invention, a plurality of retaining assemblies 256 might be utilized in coupling the tip shroud 160 to the airfoil 120.

In one form of the present invention, the outer surface 300 of the airfoil 120 is defined by a plurality of cover tiles 310 coupled to at least a portion of the exterior surface 320 of the spar 262, as shown in FIG. 3. Other embodiments of the present invention contemplate that the outer surface of the airfoil 120 might include a different quantity of tiles 310 and/or have a portion or portions not including a tile 310. Additionally, at least one embodiment contemplates that the tiles 310 substantially cover the exterior surface 320 of the spar 262. The tiles 310 may be formed of a variety of materials including, but not limited to, ceramic, intermetallic, ceramic matrix composite, metallic, and a thermal barrier coated material. In one form the thermal barrier coated material is a metallic material. The plurality of tiles 310 may be formed of the same material or may be formed of a different material for some or all of the tiles 310. The present application contemplates that the tiles 310 may have a three-dimensional-shaped outer surface. In another form of the present application the outer surface of at least one of the tiles 310 is substantially flat/planar. Further, the present invention contemplates that the resulting aggregate outer surface preferably has a three-dimensional shape, and even more preferably the resulting aggregate outer surface is an airfoil shape.

The tiles 310 are substantially adjacent and coupled to the spar 262. One form of the present invention contemplates that the plurality of tiles 310 are not permanently affixed to the spar 262. Another form of the present invention contemplates that the plurality of tiles 310 are mechanically coupled to the spar 262 by a plurality of retaining elements (not shown). Still another form of the present invention contemplates that at least one of the plurality of tiles 310 is held in place by the tip shroud 160. As shown in FIG. 3, tip shroud 160 is positioned to at least partially overlap a portion of the tip end 330 of the spar 262 The tip shroud 160 preferably includes a cover engagement portion 400 operable to engage a shroud engagement portion 410 of each of at least one of the plurality of tiles 310. Another embodiment contemplates that the tip shroud 160 overlaps the entire tip end 330 of the spar 262 thereby preferably retaining one or more of the plurality of tiles 310 against movement from the hub end 180 to the tip end 190. Other forms contemplate that the plurality of tiles 310 may also be retained by at least one coupler (not shown) to restrain movement of the tiles 310 in an axial direction.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.