# Patent

## Title
Method and system for a ceramic matrix composite shroud hanger assembly

## Abstract

A shroud and hanger assembly for a gas turbine engine and a method of transferring load from a ceramic matrix composite (CMC) shroud to a CMC shroud hanger assembly are provided. The shroud and hanger assembly includes a shroud hanger assembly formed of a first material having a first coefficient of thermal expansion, the shroud hanger assembly having a forward hanger portion and a separate aftward hanger portion and a shroud formed of a second material having a second coefficient of thermal expansion, the forward and aftward hanger portions configured to couple together to clamp across a forward radially extending wall of the shroud.

## Background
BACKGROUND
This description relates to a composite shroud hanger assembly, and, more particularly, to a method and system for a two-piece ceramic matrix composite (CMC) shroud hanger assembly which clamps across a forward vertical wall of a shroud to support the shroud while transferring turbine nozzle load through the shroud hanger assembly and into a gas turbine engine casing.
At least some known gas turbine engines include a core having a high pressure compressor, combustor, and high pressure turbine (HPT) in serial flow relationship. The core engine is operable to generate a primary gas flow. The high pressure turbine includes annular arrays (“rows”) of stationary vanes or nozzles that direct the gases exiting the combustor into rotating blades or buckets. Collectively one row of nozzles and one row of blades make up a “stage”. Typically two or more stages are used in serial flow relationship. These components operate in an extremely high temperature environment, and may be cooled by air flow to ensure adequate service life.
Components of the gas turbine engine, for example stationary shrouds or shroud segments and their supporting structures, such as, shroud hanger assemblies, are exposed to a heated stream of combustion gases. It is desirable to operate a gas turbine engine at high temperatures most efficient for generating and extracting energy from these gases. However, such elevated temperatures frequently exceed the temperature capability of the basic component materials and can result in compromise of mechanical and/or physical properties, or distortion of the components. Consequently, use has been made of various heat-resistant coatings and/or cooling processes. If cooling is used, is it usually implemented by channeling relatively cooler air, for example from various points in the high-pressure compressor of the engine, and discharging it within or from a component to provide convection, impingement, or film cooling.
In other examples, due to operating temperatures within the gas turbine engine, materials having a low coefficient of thermal expansion (CTE) are used. For example, to operate effectively in such adverse temperature and pressure conditions, ceramic matrix composite (CMC) materials may be used. These low coefficient of thermal expansion materials have higher temperature capability than similar metallic parts, so that, when operating at the higher operating temperatures, the engine is able to operate at a higher engine efficiency. However, such ceramic matrix composite (CMC) have mechanical properties that must be considered during the design and application of the CMC. CMC materials have relatively low tensile ductility or low strain to failure when compared to metallic materials. Also, CMC materials have a coefficient of thermal expansion which differs significantly from metal alloys used as restraining supports or hangers for CMC type materials. Therefore, if a CMC component is restrained and cooled on one surface during operation, stress concentrations can develop leading to a shortened life of the segment.
At least some known gas turbine engine are manufactured using a CMC “open shroud” configuration, which may be preferred for manufacturing over other types of segmented CMC shrouds, such as a “box shroud”. Complex hanger assemblies have been required, however to transfer a load from, for example, a nozzle of a turbine through the shroud hanger assembly without damaging the shroud. Because of the configuration, some portions of the CMC components are not always in compression. CMC material can withstand compression loads, but experiences a reduced life when subject to tensile or moment loads.
Other hanger designs have used a flexible spring-arm at the forward or aft side of the hanger and a ridged arm at opposite side to provide a light clamp load across the entire shroud for sealing. At the same time, additional engine components or more complex hanger designs were used to transfer the nozzle load around the shroud and through the hanger and into the turbine casing.
BRIEF DESCRIPTION
In one embodiment, a shroud and hanger assembly for a gas turbine engine includes a shroud hanger assembly formed of a first material having a first coefficient of thermal expansion, the shroud hanger assembly having a forward hanger portion and a separate aftward hanger portion and a shroud formed of a second material having a second coefficient of thermal expansion, the forward and aftward hanger portions configured to couple together to clamp across a forward radially extending wall of the shroud.
In another embodiment, a method of transferring load from a ceramic matrix composite (CMC) shroud to a CMC shroud hanger assembly includes clamping a forward hanger portion and a separate aftward hanger portion of a shroud hanger assembly together, a forward radially extending wall of the shroud positioned between the forward hanger portion and the aftward hanger portion, the forward radially extending wall receiving a clamping force on a forward side from the forward hanger portion and on an aftward side from the aftward hanger portion providing a load transfer joint between the shroud and the shroud hanger assembly. The method further includes coupling the shroud hanger assembly to a casing of a turbine and transferring load from a nozzle through a diagonal web member of the shroud hanger assembly to the casing.
In yet another embodiment, a gas turbine engine includes a shroud hanger assembly formed of a first material having a first coefficient of thermal expansion, the shroud hanger assembly having a forward hanger portion and a separate aftward hanger portion and a shroud formed of a second material having a second coefficient of thermal expansion, the forward and aftward hanger portions configured to couple together to clamp across a forward radially extending wall of the shroud.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-7 show example embodiments of the method and apparatus described herein.
FIG. 1 is a schematic diagram of a gas turbine engine in accordance with an example embodiment of the present disclosure.
FIG. 2 is a side view of a shroud hanger assembly in accordance with an example embodiment of the present disclosure.
FIG. 3 is a perspective view of a segment of the aftward hanger portion shown in FIG. 2.
FIG. 4 is a forward perspective view looking aft of the segment shown in FIG. 3 coupled to the shroud shown in FIG. 2.
FIG. 5 is an aft perspective view of the shroud hanger assembly looking forward from above.
FIG. 6 is a forward perspective view of the shroud hanger assembly looking aft from above.
FIG. 7 is a perspective view of the shroud hanger assembly looking radially inwardly.



Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and/or claimed in combination with any feature of any other drawing.
Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems including one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.
DETAILED DESCRIPTION
Embodiments of this disclosure describe a two-piece CMC shroud hanger assembly, which clamps across a forward vertical wall of a shroud to support the shroud while transferring turbine nozzle load through the hanger and into a casing of a turbine. Such a support method maintains the CMC material of the shroud hanger assembly in compression, a direction in which it has high strength, and allows the nozzle load to be transferred through the shroud instead of around it.
A forward hanger is bolted to an aft hanger proximate a radially outer diameter of the hangers. A shroud formed of a material having a relatively low coefficient of thermal expansion, such as, but, not limited to a ceramic matrix composite (CMC) material is clamped between the forward and aft hanger sections at a radially inner diameter of the hangers. This clamp allows loads from the HPT nozzle to be transferred into the forward hanger, and across a load transfer joint between the shroud and the shroud hanger assembly while allowing the CMC shroud to remain in compression. This clamp also serves to seal the shroud post-impingement cavity leakage at the forward end of the shroud. At the aft end of the shroud this leakage flow is sealed via two conformal seals, for example, but not limited to M-seals.
The CMC shroud is radially supported by one or more pins, which pass axially through both the shroud and the aft hanger. The pins are slightly loose in the shroud, and press fit into the hanger. The inner most conformal seal is present to block any flow leakage through the shroud aft pin holes.
The following detailed description illustrates embodiments of the disclosure by way of example and not by way of limitation. It is contemplated that the disclosure has general application to analytical and methodical embodiments of transmitting loads from one component to another.
Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
As used herein, the terms “axial” or “axially” refer to a dimension along a longitudinal axis of an engine. The term “forward” used in conjunction with “axial” or “axially” refers to moving in a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term “aft” used in conjunction with “axial” or “axially” refers to moving in a direction toward the rear of the engine.
As used herein, the terms “radial” or “radially” refer to a dimension extending between a center longitudinal axis of the engine and an outer engine circumference.
All directional references (e.g., radial, axial, proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto may vary.
The following description refers to the accompanying drawings, in which, in the absence of a contrary representation, the same numbers in different drawings represent similar elements.
FIG. 1 is a schematic diagram of a gas turbine engine 120 including a fan 122, a high pressure compressor 124, and a combustor 126. Engine 120 also includes a high pressure turbine 128 and a low pressure turbine 130 aligned coaxially about a longitudinal axis 132 of gas turbine engine 120. Fan 122 and turbine 130 are coupled by a first shaft 134, and high pressure compressor 124 and turbine 128 are coupled by a second shaft 136. In one embodiment, engine 120 is an F414 engine commercially available from GE Aircraft Engines, Evendale, Ohio.
In operation, air received through an inlet end 138 of engine 120 is compressed by fan 122 and channeled to high pressure compressor 124, where the compressed air is compressed even further. The highly compressed air from high pressure compressor 124 is channeled to combustor 126, Wherein it is mixed with a fuel and ignited to produce combustion gases. The combustion gases are channeled from combustor 126 to drive turbines 128 and 130, and exit an outlet end 140 of engine 120 through an exhaust nozzle assembly 142 to provide thrust.
FIG. 2 is a side view of a shroud hanger assembly 200 in accordance with an example embodiment of the present disclosure. FIG. 3 is a perspective view of a segment 300 of the aftward hanger portion 204 (shown in FIG. 2). FIG. 4 is a forward perspective view looking aft of segment 300 (shown in FIG. 3) coupled to shroud 206 (shown in FIG. 2). One or more of the segments 300 extend circumferentially about axis 132 (shown in FIG. 1). In the example embodiment, shroud hanger assembly 200 may be located within high pressure turbine 128 and/or low pressure turbine 130 (shown in FIG. 1) between or adjacent to rows of nozzles (not shown). Shroud hanger assembly 200 is formed of a first metallic material having a relatively higher coefficient of thermal expansion and includes a forward hanger portion 202 and separate aftward hanger portion 204. Shroud hanger assembly 200 also includes a shroud 206 formed of a second material having a relatively lower coefficient of thermal expansion compared to the first material. Forward hanger portion 202 and aftward hanger portion 204 are configured to couple together to clamp across a forward radially extending wall 208 of shroud 206 at a load transfer joint 209 between forward hanger portion 202 and aftward hanger portion 204.
Aftward hanger portion 204 includes a first forward radially extending leg 210 and a second aftward radially extending leg 212. Aftward hanger portion 204 also includes one or more web members 214 extending between first leg 210 and second leg 212. Specifically, in the example embodiment, web members 214 include an axially extending web member 216 and a diagonal web member 218 that extends from a radially inner end 220 of leg 210 to a radially outer end 222 of leg 212. At a radially outer extent of each of legs 210 and 212, respective hanger tabs 224 and 226 are configured to engage respective lips 228 and 230 in a turbine casing 232. Between aftward radially extending wall 240 and a radially inwardly extending leg 256 of turbine casing 232, leakage flow is sealed using two conformal seals 258 and 260, for example, but not limited to M-seals. In various embodiments, seals 260 is backed-up by a second seal 262, for example, but, not limited to, a C-seal.
Forward hanger portion 202 includes a radially extending body 233 that includes one or more apertures 234 configured to receive a respective fastener 236, such as a bolt 236 secured by a nut 238. In various embodiments, other mechanical fasteners 236 are used.
Shroud 206 is formed of CMC and includes forward radially extending wall 208, an aftward radially extending wall 240, and a body 242 extending axially therebetween. When fully assembled, forward wall 208 is clamped between forward hanger portion 202 and first forward radially extending leg 210 of aftward hanger portion 204. Bolt 236 secures forward hanger portion 202 and aftward hanger portion 204 together providing a predetermined clamping force. A load 244 transmitted from shroud 206 into hanger assembly 200 is carried through diagonal web member 218, hanger tab 226, and lip 230 to turbine casing 232.
Radial support for shroud 206 is also provided by a pin 246 extending through an aperture 248 in aftward radially extending wall 240, an aperture 250 in leg 212, an aperture 252 in leg 210, and an aperture 254 in forward radially extending wall 208 of shroud 206.
In the example embodiment, as illustrated in FIGS. 3 and 4, first forward radially extending leg 210 of aftward hanger portion 204 and forward radially extending wall 208 of shroud 206 include complementary tabs 402 spaced circumferentially about leg 210 and wall 208. Specifically, leg 210 includes tabs 404 and wall 208 includes tabs 406 extending radially outwardly between radially outwardly extending tabs 404. In this manner, tabs 404 and tabs 406 are interdigitated with respect to each other about a circumference of aftward hanger portion 204 and shroud 206.
FIG. 5 is an aft perspective view of shroud hanger assembly 200 looking forward from above. FIG. 6 is a forward perspective view of shroud hanger assembly 200 looking aft from above. In the example embodiment, forward radially extending wall 208 of shroud 206 is shown clamped between radially extending body 233 of forward hanger portion 202 and radially inner end 220 of leg 210.
FIG. 7 is a perspective view of shroud hanger assembly 200 looking radially inwardly. In the example embodiment, includes contours 700 spaced circumferentially along a radially outer surface 702 of aftward hanger portion 204. Contours 700 include a raised area 704 corresponding to each of pins 246. Increased material of each raised area provides space for respective pins which pass through aftward hanger portion 204 in the area of raised area 704. Depressed areas 706 of surface 702 corresponding to fasteners 236 and in between raised area 704 permit clearance for tooling used to tighten, loosen, or otherwise couple fasteners 236.
It will be appreciated that the above embodiments that have been described in particular detail are merely example or possible embodiments, and that there are many other combinations, additions, or alternatives that may be included.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
The above-described embodiments of a method and system of transferring load in compression through a diagonal ceramic matrix composite (CMC) web member provides a cost-effective and reliable means for maintaining CMC components in compression during operation and temperature excursions. More specifically, the method and system described herein facilitate coupling a multi-piece hanger assembly to a CMC shroud and transferring a shroud load through the CMC hanger so that the CMC components of the shroud and hanger assembly stay in compression. As a result, the methods and systems described herein facilitate extending a service life of the shroud and hanger assemblies in a cost-effective and reliable manner.
This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

## Claims

1. A shroud and shroud hanger assembly for a gas turbine engine, said assembly comprising:
a shroud hanger assembly formed of a first material having a first coefficient of thermal expansion, said shroud hanger assembly having a forward hanger portion and a separate aftward hanger portion, said shroud hanger assembly includes a diagonal web member that extends from a radially inner end of a forward radially extending leg to a radially outer end of an aftward radially extending leg of said aftward hanger portion; and
a shroud formed of a second material having a second coefficient of thermal expansion, said forward and aftward hanger portions configured to couple together to clamp across a forward radially extending wall of said shroud.

2. The shroud and hanger assembly of claim 1, wherein said forward and aftward hanger portions are configured to couple together using a mechanical fastener connection.

3. The shroud and hanger assembly of claim 1, wherein said forward and aftward hanger portions are configured to couple together using a bolted connection.

4. The shroud and hanger assembly of claim 1, wherein the first coefficient of thermal expansion is equal to the second coefficient of thermal expansion.

5. The shroud and hanger assembly of claim 1, wherein the first and second materials are ceramic matrix composite materials.

6. The shroud and hanger assembly of claim 1, wherein said shroud is supported radially by a pin extending thorough radially outwardly extending walls of said shroud and extending through radially inwardly extending legs of said aftward hanger portion.

7. The shroud and hanger assembly of claim 1, wherein said shroud hanger assembly includes an axial web member extending axially between a forward radially extending leg and an aftward radially extending leg of said aftward hanger portion.

8. The shroud and hanger assembly of claim 1, wherein said aftward hanger portion is supported radially by a first tab extending axially from a radially outer end of a forward leg of said aftward hanger portion and a second tab extending axially from a radially outer end of an aftward leg of said aftward hanger portion, said first and said second tabs configured to engage circumferential lips of a casing surrounding said shroud and hanger assembly.

9. A method of transferring load from a ceramic matrix composite (CMC) shroud to a CMC shroud hanger assembly, said method comprising:
clamping a forward hanger portion and a separate aftward hanger portion of a shroud hanger assembly together, a forward radially extending wall of the shroud positioned between the forward hanger portion and the aftward hanger portion, the forward radially extending wall receiving a clamping force on a forward side from the forward hanger portion and on an aftward side from the aftward hanger portion providing a load transfer joint between the shroud and the shroud hanger assembly;
coupling the shroud hanger assembly to a casing of a turbine; and
transferring load from a nozzle through a diagonal web member of the shroud hanger assembly to the casing.

10. The method of claim 9, wherein clamping a forward hanger portion and a separate aftward hanger portion comprises clamping the forward radially extending wall between the forward hanger portion and the aftward hanger portion at the load transfer joint.

11. A gas turbine engine comprising:
a shroud hanger assembly formed of a first material having a first coefficient of thermal expansion, said shroud hanger assembly having a forward hanger portion and a separate aftward hanger portion, said shroud hanger assembly includes a diagonal web member that extends from a radially inner end of a forward radially extending leg to a radially outer end of an aftward radially extending leg of said aftward hanger portion; and
a shroud formed of a second material having a second coefficient of thermal expansion, said forward and aftward hanger portions configured to couple together to clamp across a forward radially extending wall of said shroud.

12. The gas turbine engine of claim 11, wherein said forward and aftward hanger portions are configured to couple together using a mechanical fastener connection.

13. The gas turbine engine of claim 11, wherein said forward and aftward hanger portions are configured to couple together using a bolted connection.

14. The gas turbine engine of claim 11, wherein the first coefficient of thermal expansion is equal to the second coefficient of thermal expansion.

15. The gas turbine engine of claim 11, wherein the first and second materials are ceramic matrix composite materials.

16. The gas turbine engine of claim 11, wherein said shroud is supported radially by a pin extending thorough radially outwardly extending walls of said shroud and extending through radially inwardly extending legs of said aftward hanger portion.

17. The gas turbine engine of claim 11, wherein said shroud hanger assembly includes an axial web member extending axially between a forward radially extending leg and an aftward radially extending leg of said aftward hanger portion.

18. The gas turbine engine of claim 11, wherein said aftward hanger portion is supported radially by a first tab extending axially from a radially outer end of a forward leg of said aftward hanger portion and a second tab extending axially from a radially outer end of an aftward leg of said aftward hanger portion, said first and said second tabs configured to engage circumferential lips of a casing surrounding said shroud and hanger assembly.