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1. (WO2014163674) DOVETAIL RETENTION SYSTEM FOR BLADE TRACKS
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DOVETAIL RETENTION SYSTEM FOR BLADE TRACKS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application Number 61 /779,534, filed 13 March 2013, the disclosure of which is now incorporated herein by reference.

FIELD OF THE DISLOSURE

[0002] The present disclosure relates generally to gas turbine engines, and more specifically to turbine shrouds used in gas turbine engines.

BACKGROUND

[0003] Gas turbine engines are used to power aircraft, watercraft, power generators, and the like. Gas turbine engines typically include a compressor, a combustor, and a turbine. The compressor compresses air drawn into the engine and delivers high pressure air to the combustor. In the combustor, fuel is mixed with the high pressure air and is ignited. Products of the combustion reaction in the combustor are directed into the turbine where work is extracted to drive the compressor and, sometimes, an output shaft, fan, or propeller. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.

[0004] Compressors and turbines typically include alternating stages of static vane assemblies and rotating wheel assemblies. The rotating wheel assemblies include disks carrying blades around their outer edges. When the rotating wheel assemblies turn, tips of the blades move along blade tracks included in static shrouds that are arranged around the rotating wheel assemblies. Such static shrouds may be coupled to an engine case that surrounds the compressor, the combustor, and the turbine.

[0005] Some shrouds positioned in the turbine may be exposed to high temperatures from products of the combustion reaction in the combustor. Such shrouds sometimes include components made from materials that have different coefficients of thermal expansion. Due to the differing coefficients of thermal expansion, the components of some turbine shrouds expand at different rates when exposed to combustion products. For example, coupling such components with

traditional fasteners such as rivets or bolts may not allow for the differing levels of expansion and contraction during operation of the gas turbine engine.

SUMMARY

[0006] The present application discloses one or more of the features recited in the appended claims and/or the following features which, alone or in any

combination, may comprise patentable subject matter.

[0007] A turbine shroud for use in the turbine section of a gas turbine engine is disclosed in this paper. The turbine shroud is adapted to extend around a rotatable turbine wheel assembly having a wheel and blades. The turbine shroud blocks hot gasses flowing through the turbine section from passing over the blades without pushing the blades. By ensuring that the hot gasses push the blades, the turbine shroud helps cause the turbine wheel assembly to rotate when hot gasses are driven through the turbine section from a combustion section of the gas turbine engine. Rotation of the turbine wheel assembly can then be used to drive a compressor, a fan, a propeller, a generator, or other modules coupled to the turbine wheel assembly.

[0008] In illustrative embodiments, the turbine shroud disclosed includes a metallic support ring and a ceramic blade track. The metallic support ring is adapted to be coupled to other metallic components of the turbine section to hold the turbine shroud in place relative to the rest of the turbine section. The ceramic blade track is illustratively made up of a plurality of ceramic blade track segments manufactured from a ceramic matrix composite material adapted to withstand high temperatures. The plurality of ceramic blade track segments are arranged to form a hoop around the turbine wheel assembly so that the ceramic blade track is positioned radially between the metallic support ring and the turbine wheel assembly. The position of the ceramic blade track insulates the metallic support ring from the hot gasses directed at the blades of the turbine wheel assembly.

[0009] In illustrative embodiments, the turbine shroud also includes a plurality of segment retainers adapted to hold each of the plurality of ceramic blade track segments in place relative to the metallic support ring while allowing the metallic support ring and the ceramic segments of the blade track to expand and contract at different rates based on temperature. The metallic support ring has a metallic inner carrier formed to include a plurality of apertures. The plurality of ceramic blade track segments each includes an arcuate runner arranged radially inward from the metallic inner carrier and at least one dovetail post extending radially outward from the arcuate runner through one of the apertures formed in the metallic inner carrier. The plurality of segment retainers mate with the dovetail posts of each ceramic blade track segment so that the plurality of ceramic blade track segments are coupled to the metallic inner carrier.

[0010] According to an aspect of the present disclosure, a turbine shroud may include a metallic inner carrier, a plurality of ceramic blade track segments, and a plurality of segment retainers. The metallic inner carrier may be formed to include a plurality of apertures. The plurality of ceramic blade track segments may each include an arcuate runner arranged radially inward from the metallic inner carrier and a dovetail post extending radially outward from the arcuate runner through one of the apertures formed in the metallic inner carrier. The plurality of segment retainers may be arranged radially outward from the metallic inner carrier. Additionally, each segment retainer may be formed to include a retention channel mated with a portion of a corresponding dovetail post. Further each segment retainer may be sized to block movement of the corresponding dovetail post through the aperture so that the plurality of ceramic blade track segments are coupled to the metallic inner carrier.

[0011] In some embodiments, each dovetail post may include a body extending radially outward from a corresponding arcuate runner through the aperture formed in the metallic inner carrier and a head spaced apart from the arcuate runner. The head may be received in the retention channel of the segment retainer. The body may extend axially along an outer radial face of the arcuate runner.

[0012] In some embodiments, the body may be arcuate and may extend circumferentially along an outer radial face of the arcuate runner. The head may extend circumferentially both clockwise and counter-clockwise from the body.

[0013] In some embodiments, head may extend axially both forward and aft from the body. The retention channel formed in the segment retainer may be arcuate.

[0014] In some embodiments, the turbine shroud may also include a first perimeter seal. The first perimeter seal may be arranged radially between the metallic inner carrier and the arcuate runner of the blade track segment. The first perimeter seal may be a rope seal. The first perimeter seal may be arranged axially forward of the dovetail post.

[0015] In some embodiments, the turbine shroud may include a second perimeter seal. The second perimeter seal may be arranged radially between the metallic inner carrier and the arcuate runner. The second perimeter seal may be arranged axially rearward of the dovetail post.

[0016] In some embodiments, the turbine shroud may include an outer carrier. The outer carrier may be coupled to the metallic inner carrier. The outer may cooperate with the metallic inner carrier to form an annular cavity between the outer carrier and the metallic inner carrier. The head of the dovetail post and the segment retainer may be located in the annular cavity. In some embodiments, the ceramic blade track segment may include ceramic fibers and a matrix material.

[0017] According to another aspect of the present disclosure, a turbine shroud may include an inner carrier, a blade track segment, and a first segment retainer. The inner carrier may be formed to include a first aperture. The blade track segment may include a runner arranged radially inward from the inner carrier and a first dovetail post extending radially outward from the arcuate runner through the first aperture formed in the inner carrier. The first segment retainer may be arranged radially outward from the inner carrier and mated with a portion of the first dovetail post.

[0018] In some embodiments, the inner carrier may have a first coefficient of thermal expansion and the blade track segment may have a second coefficient of thermal expansion. The second coefficient of thermal expansion may be smaller than the first coefficient of thermal expansion.

[0019] In some embodiments, the inner carrier may be formed to include a second aperture. The blade track segment may include a second dovetail post extending radially outward from the arcuate runner through the second aperture formed in the inner carrier. The turbine shroud may include a second segment retainer arranged radially outward from the inner carrier and mated with a portion of the second dovetail post.

[0020] In some embodiments, the first dovetail post and the second dovetail post may be spaced radially apart. The first dovetail post and the second dovetail post may be spaced axially apart.

[0021] According to another aspect of the present disclosure, a method of assembling a turbine shroud may include inserting a dovetail post included in a ceramic blade track segment through an aperture formed in a metallic inner carrier. The method may also include sliding a segment retainer over a portion of the dovetail post inserted through the aperture. Further the method may include attaching the metallic inner carrier to a metallic turbine case.

[0022] In some embodiments, the step of attaching the metallic inner carrier to the metallic turbine case may include (i) sliding the ceramic blade track segment and the metallic inner carrier into a metallic outer carrier and (ii) coupling the metallic outer carrier to a connection feature of the metallic turbine case. The metallic inner carrier may be concentric with the metallic outer carrier and an annular cavity may be formed between the metallic inner carrier and the metallic outer carrier when the ceramic blade track segment and the metallic inner carrier are slid into a metallic outer carrier. The segment retainer may be located in the annular cavity when the ceramic blade track segment and the metallic inner carrier are slid into the metallic outer carrier.

[0023] In some embodiments, the method may include placing a rope seal in a perimeter seal pocket. The perimeter seal pocket may be formed in the metallic inner carrier.

[0024] These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Fig. 1 is a cut-away perspective view of a gas turbine engine;

[0026] Fig. 2 is a partial cross-sectional view of the gas turbine engine of Fig. 1 showing the arrangement of a turbine shroud in the gas turbine engine;

[0027] Fig. 2A is a detail cross-sectional view showing a portion of Fig. 2;

[0028] Fig. 2B is another detail cross-sectional view taken along line 2B-2B shown in Fig. 2;

[0029] Fig. 3 is an exploded perspective view of a segment of the turbine shroud shown in Fig. 2 showing that the turbine shroud includes a blade track segment with axially-extending dovetail posts, an inner carrier segment, a plurality of segment retainers, a clip segment, and an outer carrier segment;

[0030] Fig. 4 is a partial cross-sectional view of another gas turbine engine showing the arrangement of another turbine shroud in the gas turbine engine;

[0031] Fig. 4A is a detail cross-sectional view showing a portion of Fig. 4; and

[0032] Fig. 5 is an exploded perspective view of a section of the turbine shroud shown in Fig. 4.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

[0034] Fig. 1 is an illustrative aerospace gas turbine engine 10 cut-away to show that the engine 10 includes a fan 12, a compressor 14, a combustor 16, and a turbine 18 all mounted to a case 20. The fan 12 is driven by the turbine 18 and provides thrust for propelling an air vehicle (not shown). The compressor 14 is configured compress and deliver air to the combustor 16. The combustor 16 is configured to mix fuel with the compressed air received from the compressor 14 and to ignite the fuel. The hot high pressure products of the combustion reaction in the combustor 16 are directed into the turbine 18 and the turbine 18 extracts work to drive the compressor 14 and the fan 12.

[0035] Referring now to Fig. 2, a portion of the turbine 1 8 is shown to include static turbine vane assemblies 21 , 22 and a turbine wheel assembly 26. Each vane assembly 21 , 22 includes a plurality corresponding of vanes 31 , 32 and the turbine wheel assembly 26 includes a plurality of corresponding blades 36. The vanes 31 of the vane assembly 21 extend across the flow path of the hot, high-pressure combustion products from the combustor 16 to direct the combustion products toward the blades 36 of the turbine wheel assembly 26. The blades 36 are in turn pushed by the combustion products to cause the turbine wheel assembly 26 to rotate; thereby, driving the rotating components of the compressor 14 and the fan 12.

[0036] The turbine 18 also includes a turbine shroud 46 that extends around turbine wheel assembly 26 to block combustion products from passing over the blades 36 without pushing the blades 36 to rotate as shown in Fig. 2. Combustion products that are allowed to pass over the blades 36 do not push the blades 36 and such passed-over products contribute to lost performance within the engine 10.

[0037] The turbine shroud 46 illustratively includes a metallic support ring 48, a ceramic blade track (sometimes called seal ring) 50, and a plurality of metallic segment retainers 52 as shown in Figs. 2, 2A, and 2B. The support ring 48 is coupled to the case 20 and extends inwardly in a radial direction from the case 20 toward the turbine wheel assembly 26. The blade track 50 is coupled to the support ring 48 by the segment retainers 52 and is supported by the support ring 48 in position adjacent to the blades 36 of the turbine wheel assembly 26 so that the blades 36 run along the blade track 50.

[0038] The support ring 48 is an annular component including an outer carrier 54 and an inner carrier 56 as shown in Figs. 2 and 2A. The outer carrier 48 is coupled to the inner carrier 50 by a clip 58 that is deformed to clamp down on both the outer carrier 48 and the inner carrier 50. The outer carrier 54 is made up of a plurality of outer carrier segments 55 and is coupled to the case 20. The inner carrier 56 is made up of a plurality of inner carrier segments 57 each coupled to a corresponding outer carrier segment 55. The clip 58 is also made up of a plurality clip segments 59 with a C-shaped cross-section that forms a forward facing channel 71 . In other embodiments, the outer carrier 54, the inner carrier 56, and the clip 58 may each be monolithic components rather than segmented components.

[0039] The blade track 50 is made up of a plurality of blade track segments 51 , one of which is shown in Fig. 3. Each of the blade track segments 51 is coupled to a corresponding outer carrier segment 55 and an inner carrier segment 57 by two of the segment retainers 52 to support the blade track segment 51 in position adjacent to the blades 36 of the turbine wheel assembly 26 as shown in Fig. 2.

[0040] In the illustrative embodiment, the blade track segments 51 are each made from a ceramic material; and, more particularly, a ceramic matrix composite (CMC). However, other ceramic materials are contemplated. For purposes of this application, a ceramic material is any monolithic ceramic or composite in which at least one constituent is a ceramic. In other embodiments, the blade track segments 51 may be made of other metallic, non-metallic, or composite materials.

[0041] Turning now to Fig. 3, segments 51 , 55, 57, 59 of the blade track 50, the outer carrier 54, the inner carrier 56, and the clip 58 are shown along with two segment retainers 52 and two locating keys 60. Each of the segments 51 , 55, 57, 59 are repeated to provide the fully annular turbine shroud 46.

[0042] Each blade track segment 51 includes an arcuate runner 65, a first dovetail post 61 , and a second dovetail post 62 as shown in Fig. 3. The arcuate runner 65 is located adjacent to the blades 36 of the turbine wheel assembly 26 so that the blades 36 move along an inner radial face 66 of the arcuate runner 65. The dovetail posts 61 , 62 are coupled to an outer radial face 68 of the arcuate runner 65 and are spaced radially from one another as shown in Fig. 3.

[0043] Each of the dovetail posts 61 , 62 includes a body 70 and a head 72 as shown in Fig. 3. The body 70 of each dovetail post 61 , 62 extends outward in the radial direction from the arcuate runner 65 and axially along the arcuate runner 65. The head 72 of each dovetail post extends circumferentially in both directions from the body 70 so that the head 72 can be captured by the segment retainers 52 when the turbine shroud 46 is assembled as shown in Fig. 2B.

[0044] Each of the outer carrier segments 55 includes a forward connection portion 74, an aft connection portion 76, and an intermediate portion 78 extending axially from the forward connection portion 74 to the aft connection portion 76 as shown in Fig. 3. The forward connection portion 74 includes outer hangers 75 for connecting the outer carrier 54 to the case 20 and inner hangers 77 for connecting the outer carrier 54 to a forward portion of the blade track 50. The aft connection portion 76 includes an outer hanger 79 for connecting the outer carrier 54 to the case 20 and an aft flange 80 for connecting the outer carrier 54 to the inner carrier 56 via the clip 58 as shown in Fig. 2A.

[0045] Each of the inner carrier segments 57 includes an arcuate plate 82, a forward seal carrier 84, an aft seal carrier 86, and an aft flange 90 as shown in Figs. 2 and 3. The arcuate plate 82 is formed to include apertures 91 , 92 sized and arranged to receive the dovetail posts 61 , 62 of the corresponding blade track segment 51 as shown in Figs. 2A and 2B. The forward seal carrier 84 is spaced forward in the axial direction from the apertures 91 , 92 and extends inward in the radial direction from the plate 82. The aft seal carrier 86 is spaced aft in the axial direction from the apertures 91 , 92 and extends inward in the radial direction from the plate 82. Each seal carrier 84, 86 forms a corresponding seal receiving channel 85, 87 extending circumferentially along the plate 82 and sized to receive rope seals 88, 89 as shown in Fig. 2A. The aft flange 90 is coupled to the aft flange 80 of the outer carrier segment 55 via the clip 58 as shown in Fig. 2A.

[0046] When assembled, the outer carrier 54 and the inner carrier 56 cooperate to form an annular cavity 98 as shown in Fig. 2A. The heads 72 and the segment retainers 52 are arranged in the annular cavity 98 when the turbine shroud 46 is assembled.

[0047] Each segment retainer 52 is illustratively C-shaped forming a retention channel 94 sized and arranged to receive the head 72 of one of the dovetail posts 62, 64 as shown in Figs. 2A and 3. Further, each segment retainer 52 is sized to block the heads 72 of the dovetail posts 61 , 62 from moving through the apertures 91 , 92 of the inner retainer 56 when the segment retainers 52 are coupled to the dovetail posts 61 , 62 as shown in Fig. 2B. In other embodiments, the segment retainers 52 may be coupled to or incorporated into the inner carrier segments 57 and the apertures 91 , 92 of the inner carrier segments 57 may be slots extending from an edge of the inner carrier segment 57.

[0048] In other embodiments, the arrangement of the dovetail retention system formed by the blade track segments 51 , the segment retainers 52, and the inner carrier segments 57 may be reversed. In such an embodiment, the segment retainers 52 may be incorporated into the blade track segments 51 in place of the dovetail posts 61 , 62. Further, the dovetail posts 61 , 62 may be attached to plates and may extend through the apertures formed in the inner carrier segments 57 to allow mating of the dovetail posts 61 , 62 with the segment retainers 52.

[0049] The locating keys 60 are configured to locate circumferentially the inner carrier segments 57 relative to the outer carrier segments 55 when the turbine shroud 46 is assembled. The aft flange 80 of the outer carrier segment 55 is formed to include holes 95 sized to receive the locating keys 60 as shown in Fig. 3. The aft flange 90 of the inner carrier segment 57 is formed to include notches 96 sized to receive a portion of the locating keys 60. When assembled, the locating keys 60 extend through the holes 95 and into the notches 96 to locate the inner carrier segments 57 relative to the outer carrier segments 55.

[0050] According to one method of assembling the turbine shroud 46, the blade track segment 51 is first coupled to the inner carrier segment 57 by the segment retainers 52. To couple the blade track segment 51 to the inner carrier segment 57, the dovetail posts 61 , 62 of a blade track segment 51 are radially inserted through the apertures 91 , 92 formed in the inner carrier segment 57 as shown in Figs. 2, 2A, and 2B. Then segment retainers 52 are slid over the heads 72 of the dovetail posts 61 , 62 so that the heads of the dovetail posts 61 , 62 are received in the retention channels 94 of a segment retainer 52.

[0051] Next, the outer carrier segment 55 is located circumferentially relative to the inner carrier segment 57. To locate the outer carrier segment 55, the outer carrier segment 55 is placed over the inner carrier segment 57 with holes 95 formed in the aft flange 80 of the outer carrier segment 55 aligned with notches 96 formed in the aft flange 90 of the inner carrier segment 57. Then, locating keys 60 are inserted through holes 95 are into notches 96.

[0052] Then the outer carrier segment 55 is coupled to the inner carrier segment 57. To couple the outer carrier segment 55 to the inner carrier segment 57, the clip segment 59 is slid over the aft flanges 80, 90 included in the outer carrier segment 55 and the inner carrier segment 57, respectively, so that the aft flanges 80, 90 are received in the channel 71 formed by the clip segment 59. The clip segment 59 is then deformed or crimped to engage the aft flanges 80, 90 coupling the outer carrier segment 55 and the inner carrier segment 57.

[0053] After assembling a set 99 of corresponding segments 51 , 55, 57, 59, other sets 99 are assembled. The sets 99 are then arranged in a circular pattern and coupled together. The sets 99 are coupled together via strip seals (not shown) to form the annular turbine shroud 46. The turbine shroud 46 is then coupled to the case 20 via outer hangers 75, 78 included in the outer carrier 54 as shown in Fig. 2.

[0054] Another illustrative turbine shroud 246 is shown in Figs. 4-5. The turbine shroud 246 is configured for use in engine 10 and is substantially similar to the turbine shroud 46 shown in Figs. 1 -4 and described herein. Accordingly, similar reference numbers in the 200 series indicate features that are common between the turbine shroud 46 and the turbine shroud 246. Further the method of assembling the turbine shroud 246 is similar to the method of assembling the turbine shroud 46 described herein. The description of the engine 10 and the turbine shroud 46 and its method of assembly are hereby incorporated by reference to apply to the turbine shroud 246, except in instances when it conflicts with the specific description and drawings of the turbine shroud 246.

[0055] Unlike the turbine shroud 46, the dovetail posts 261 , 262 that are coupled to the arcuate runner 265 are spaced axially from one another as shown in Fig. 5. Also, the body 270 of each dovetail post 261 , 262 extends circumferentially along the arcuate runner 265. Further, the head 272 of each dovetail post extends axially in both directions from the body 270 as shown in Fig. 3A. In the illustrative embodiment, the heads 272 of each dovetail post 261 , 262 is flat, or tangent, to the outer radial surface of the runner 265. In other embodiments, the heads 272 of each dovetail post 261 , 262 are arcuate and spaced a consistent distance from the runner 265. To accommodate the dovetail posts 261 , 262, the arcuate plate 282 is formed to include apertures 291 , 292 that extend circumferentially as shown in Fig. 5 to receive the dovetail posts 261 , 262 of the corresponding blade track segment 251 as shown in Fig. 5.

[0056] Also, unlike the turbine shroud 46, the aft flanges 280, 290 of the outer carrier 254 and the inner carrier 256 are coupled via a bird mouth and hanger arrangement as shown in Figs. 4 and 4A. More specifically, the aft flange 280 of the outer carrier 254 forms a rearwardly-opening channel that receives the aft flange 290 as shown in Figs. 4 and 4A.

[0057] While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.