The present disclosure relates generally to gas turbine engines, and more specifically to turbine shrouds used in gas turbine engines.
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. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.
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.
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.
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.
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.
In illustrative embodiments, the turbine shroud disclosed includes an annular ceramic runner that is illustratively made from a ceramic matrix composite material adapted to withstand high temperatures. The ceramic runner is formed to include a plurality of cutouts that extend inward from an outer radial surface of the annular ceramic runner toward an inner radial surface of the annular ceramic runner. The turbine shroud also includes a plurality of inserts each arranged to extend into a corresponding cutout. Each insert is held in its corresponding cutout by a braze layer.
In illustrative embodiments, the turbine shroud disclosed includes a metallic carrier adapted to be coupled to other metallic components of the turbine section to hold the ceramic runner in place relative to the rest of the turbine section. More specifically, the metallic carrier holds the ceramic runner radially between the metallic carrier and the turbine wheel assembly to insulate the annular metallic carrier from the hot gasses directed at the blades of the turbine wheel assembly.
In illustrative embodiments, the plurality of inserts coupled engage with the metallic carrier to form a cross-key connection between the ceramic runner and the metallic carrier. The cross-key connection locates the ceramic blade track relative to the metallic carrier while allowing the metallic carrier and the ceramic blade track to expand and contract at different rates based on temperature.
These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.
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.
The turbine 18 illustratively includes static turbine vane assemblies 21, 22, etc. and corresponding turbine wheel assemblies 26 etc. as shown in
The turbine 18 also includes a plurality of turbine shrouds 46, 47, etc. that extend around each turbine wheel assembly 26 etc. to block combustion products from passing over the blades 36 etc. without pushing the blades 36 etc. to rotate. An exemplary first stage turbine shroud 46, shown in
The turbine shroud 46 illustratively includes a carrier 48, a blade track (sometimes called seal ring) 50, and a retainer 52 as shown in
In the illustrative embodiment, the blade track 50 includes an annular runner 51 and a plurality of inserts 53 as shown in
In some embodiments, instead of bonding the inserts 53 to the annular runner 51 using a braze layer 57, the inserts 53 may be integrally woven into a preform that is later hardened to create the annular runner 51 so that the inserts are bonded to the annular runner 51. In some such embodiments, the inserts 53 are machined after hardening of the annular runner 51 so that the inserts 53 have a predetermined shape/orientation relative to the geometry of the annular runner 51.
In some embodiments, instead of bonding the inserts 53 to the annular runner 51 using a braze layer 57, the inserts 53 may be welded to the annular runner 51 creating a weld between the inserts 53 and the annular runner 51 (similar to the braze layer 57). Filler materials would be used to form the welds and such filler materials may include silicon, a transition metal silicide, and/or a MAX phase material.
The annular runner 51 is illustratively made from a ceramic material; and, more particularly, a ceramic matrix composite (CMC) including silicon carbide fibers and silicon carbide matrix. 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 annular runner 51 may be made of other metallic, non-metallic, or composite materials with low coefficients of thermal expansion.
Similarly, in the illustrative embodiment, each insert 53 is made from a ceramic material; and, more particularly, a ceramic matrix composite (CMC) including silicon carbide fibers and silicon carbide matrix. In other embodiments, each insert 53 may be made from monolithic silicon carbide, dense chopped fiber reinforced silicon carbide, monolithic silicon nitride based materials, monolitihic aluminum oxide, whisker reinforced aluminum oxide, and/or MAX phase materials (e.g. Ti3SlC2, Ti2AlC, etc.). In still other embodiments, each insert 53 may be made of other metallic, non-metallic, or composite materials with low coefficients of thermal expansion that are compatible with both the carrier 48 and the annular runner 51.
The braze layer 57 is illustratively made from a transition metal and silicon. More particularly, some embodiments of the illustrative braze layer 57 include a combination of molybdenum (Mo) and silicon (Si), a combination of Niobium (Nb) and silicon (Si), or a combination of titanium (Ti) and silicon (Si). In some embodiments, the braze layer 57 may also include fluxing agents such as boron (B) and/or carbon (C). In some embodiments, the braze layer may include filler materials such as silicon carbide, polycarbosilanes, carbon, MAX phase materials, aluminum oxide, or other types of filler.
The illustrative inserts 53 extend outward in the radial direction from the annular runner 51 as shown in
The cutouts 55 are illustratively arcuate and sized to receive a portion of the insert 53 as shown in
The annular runner 51 has a relatively low coefficient of thermal expansion because of its composition. The illustrative annular runner 51 has a coefficient of thermal expansion of between about 1.0 and 4.0 in/in/F. Considering this relatively small coefficient of thermal expansion, the annular runner 51 can be designed to maintain a small gap between the blade track 50 and the blades 36 thereby improving performance of the engine 10.
Additionally, the annular runner 51 is a unitary component forming a full hoop as shown in
To accommodate the connection of the CMC blade track 50 to the metallic carrier 48 (which has a relatively high coefficient of thermal expansion, illustratively between about 5.0 and 10.0 in/in/F), the turbine shroud 46 includes a cross-key connection 54 that is formed between the carrier 48 and the blade track 50 as shown, for example, in
In the illustrative embodiment, the keys 56 are provided by a portion of each inserts 53 that extends outward in the radial direction from the annular runner 51. In other embodiments, the keys may be integrated with the annular runner 51 as described in U.S. Provisional Application No. 61/758,023, filed Jan. 29, 2013, which is hereby incorporated by reference herein. The keyways 58 are formed in the carrier 48 and extend outward in the radial direction into the carrier 48 as shown in
Referring now to
The support band 68 forms a downwardly-opening channel 80 that faces the blade track 50 as shown in
The retainer 52 is an annular metallic ring with a linear cross section as shown in
According to at least one method of assembling the turbine shroud 46, a user first places each of the inserts 53 into a corresponding cutout 55 formed in the annular runner 51. Then the user brazes the inserts 53 in place forming the braze layer 57 between each insert 53 and the annular runner 51 to form the blade track 50.
When the blade track 50 is completed, the user rotates the blade track 50 to a predetermined orientation relative to the retainer 48 so that the keys 56 are aligned corresponding keyways 58. Then the user nests the blade track 50 into the retainer 48 so that the blade track 50 is concentric with the retainer. Next, the user inserts the keys 56 of the blade track 50 into the corresponding keyways 58 formed in the carrier 48 to thereby establish the cross-key connection 54 between the blade track 50 and the carrier 48.
Another illustrative blade track 250 is shown in
Unlike blade track 50, the cutout 255 of the annular runner 251 included in the blade track 250 extends all the way through the annular runner 251 from the outer radial surface 261 through the inner radial surface 263 as shown in
Another illustrative blade track 350 is shown in
Unlike blade track 50, the insert 353 of the blade track 350 is cross-shaped when viewed in the axial direction as shown in
Another illustrative blade track 450 is shown in
Unlike blade track 50, the insert 453 of the blade track 450 is T-shaped when viewed in the axial direction as shown in
Another illustrative turbine 518 is shown in
Unlike the turbine 18, the turbine 518 includes a turbine shroud 546 in which the cross-key connection 554 is reversed such that the metallic carrier 548 includes the keys 556 and the blade track 550 includes the keyways 558 as shown in
The illustrative inserts 553 extend inward in the radial direction from the outer radial surface 561 of the annular runner 551 as shown in
The cutouts 555 are illustratively arcuate and sized to receive the insert 553 as shown in
Another illustrative blade track 650 is shown in
Unlike blade track 550, the cutout 655 of the annular runner 651 included in the blade track 650 extends all the way through the annular runner 651 from the outer radial surface 661 through the inner radial surface 663 as shown in
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.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/779,572, filed 13 Mar. 2013, the disclosure of which is now incorporated herein by reference.
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