Abstract:
According to some embodiments, a ceramic matrix composite (CMC) hanger sleeve is provided for retaining a ceramic matrix composite shroud panel. The sleeve may be connected to an upper hanger by a retainer or a casing. The hanger sleeve includes a radially inward opening with a flowpath panel disposed therein. When the CMC flowpath panel is worn due to time, rubs or both, the panel may be replaced without need to replace the entire assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage application under 35 U.S.C. §371(c) of prior filed, co-pending PCT application serial number PCT/US14/071058, filed on Dec. 18, 2014 which claims priority to U.S. Provisional Patent Application Serial No. 61/928,757, titled “CMC Hanger Sleeve for CMC Shroud” and having filing date Jan. 17, 2014. The above-listed applications are incorporated by reference herein. 
     
    
     FIELD OF INVENTION 
       [0002]    The disclosed embodiments generally pertain to shrouds for a gas turbine engine. More particularly, but not by way of limitation, present embodiments relate to ceramic matrix composite hanger sleeves for ceramic matrix composite shrouds utilized in gas turbine engines. 
       BACKGROUND 
       [0003]    A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is located at a forward end of the engine. Moving toward the aft end, in order, the intake is followed by a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the gas turbine engine, such as, for example, low-pressure and high-pressure compressors, and low-pressure and high-pressure turbines. This, however, is not an exhaustive list. A gas turbine engine also typically has an internal shaft axially disposed along a center longitudinal axis of the engine. The internal shaft is connected to both the turbine and the air compressor, such that the turbine provides a rotational input to the air compressor to drive the compressor blades. 
         [0004]    In operation, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine first receives the hot combustion gases from the combustor and includes a stator nozzle assembly directing the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a supporting rotor disk. In a two stage turbine, a second stage stator nozzle assembly is positioned downstream of the first stage blades followed in turn by a row of second stage rotor blades extending radially outwardly from a second supporting rotor disk. The turbine converts the combustion gas energy to mechanical energy. 
         [0005]    Each of the high pressure and low pressure turbines may include one or more stages of rotor blades which extend radially outward from rotor discs. A shroud assembly circumscribes the turbine rotor and defines an outer boundary for combustion gases flowing through the turbine. The turbine shroud may be a single unitary structure or may be formed of a plurality of segments. Some known shroud assemblies include a shroud hanger that is coupled to an outer casing of the engine to provide support to a plurality of shrouds positioned adjacent to, and radially outward of, the tips of the turbine blades. 
         [0006]    The shroud must be capable of meeting the design life requirements for use in the turbine engine operating temperature and pressure environment. To enable current materials to operate effectively in such strenuous temperature and pressure conditions, it has been practiced to utilize composite and, in particular, ceramic matrix composite (CMC) materials for use in the shroud segments because they have higher temperature capability than metallic type parts. However, such ceramic matrix composite (CMC) have mechanical properties that must be considered during the design and application of the CMC use as a shroud segment or component. 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 shrouds of CMC type materials. Therefore, if a CMC shroud segment is restrained and cooled on one surface during operation, stress concentrations can develop leading to failure of the segment. 
         [0007]    Another goal with existing shroud structures is to improve stress levels and gradients with the flowpath portion of the shroud, and therefore improve hardware durability. Further, when adjacent blades expand and contract due to thermal conditions, the blades can rub the shroud needing replacement. Over time, the rubs may result in blades needing to be replaced or the shroud. It may be beneficial to have portions of the shroud be replaced in the flowpath area, rather than the entire shroud structure. 
         [0008]    As may be seen by the foregoing, it may be beneficial to improve aspects of function and durability of gas turbine engine components. Moreover, it may be beneficial to improve the reliability of a CMC shroud, part quality, manufacturability and allow for replacement solely of the flowpath portion of the shroud assembly. 
         [0009]    The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the instant embodiments are to be bound. 
       BRIEF DESCRIPTION 
       [0010]    According to some embodiments, a CMC hanger sleeve is provided for retaining a ceramic matrix composite shroud panel. The hanger is connected to an upper hanger by a retainer. The hanger sleeve includes a radially inward opening with a flowpath panel disposed therein. When this flowpath panel is worn due to time, rubs or both, the flowpath panel may be replaced without need to replace the entire assembly. 
         [0011]    According to some embodiments, a ceramic matrix composite hanger assembly includes a CMC hanger sleeve having a first CMC hanger sleeve leg and a second CMC hanger sleeve leg, the first and second CMC hanger sleeve legs may be spaced apart at a radial inward end. A CMC flowpath panel is disposed between the first and second CMC hanger sleeve legs at the radial inward end. A spacing may be between the radial outer ends of the first and second CMC hanger sleeve legs and, a cooling air flowpath passing through the CMC hanger sleeve and cooling the flowpath panel. 
         [0012]    All of the above outlined features are to be understood as exemplary only and many more features and objectives of the CMC hanger sleeve for the CMC shroud may be gleaned from the disclosure herein. This Brief Description is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Brief Description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the present invention is provided in the following written description of various embodiments of the invention, illustrated in the accompanying drawings, and defined in the appended claims. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith. 
     
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         [0013]    The above-mentioned and other features and advantages of these exemplary embodiments, and the manner of attaining them, will become more apparent and the CMC hanger sleeve for CMC shroud will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein: 
           [0014]      FIG. 1  is a side section view of an exemplary gas turbine engine; 
           [0015]      FIG. 2  is a side section view of an assembled exemplary turbine assembly including a CMC hanger sleeve and CMC shroud or flowpath panel; 
           [0016]      FIG. 3  is an isometric view of a first exemplary shroud hanger; 
           [0017]      FIG. 4  is an isometric view of a second exemplary shroud hanger; 
           [0018]      FIG. 5  is an isometric view of a further alternate exemplary shroud hanger; 
           [0019]      FIG. 6  is an isometric view of a CMC flowpath panel for use with the exemplary shroud hangers; and, 
           [0020]      FIG. 7  is an isometric view of a second exemplary shroud assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0022]    Referring to  FIGS. 1-7  various embodiments of a Ceramic Matrix Composite (“CMC”) hanger sleeve for a CMC shroud are depicted. The shroud hanger sleeve is an alternative architecture wherein the flowpath portion of the shroud is separated into multiple portions along the axial direction while a majority of the flowpath surface is formed from a panel, which may aid in part, quality and manufacturability. All of these features improve any or all of manufacture, operation or performance. 
         [0023]    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 engine nozzle, or a component being relatively closer to the engine nozzle as compared to another component. 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. 
         [0024]    Referring initially to  FIG. 1 , a schematic side section view of a gas turbine engine  10  is shown. The function of the gas turbine engine  10  is to extract energy from high pressure and temperature combustion gases and convert the energy into mechanical energy for work. The gas turbine engine  10  has an inlet end  12  wherein air enters the core or propulsor  13  which is defined generally by a high pressure compressor  14 , a combustor  16  and a multi-stage high pressure turbine  20 . Collectively, the propulsor  13  provides thrust or power during operation. The gas turbine engine  10  may be used for aviation, power generation, industrial, marine or the like. 
         [0025]    In operation, air enters through the air inlet end  12  of the gas turbine engine  10  and moves through at least one stage of compression where the air pressure is increased and directed to the combustor  16 . The compressed air is mixed with fuel and burned in the combustor  16  providing the hot combustion gas which exits the combustor  16  toward the high pressure turbine  20 . At the high pressure turbine  20 , energy is extracted from the hot combustion gas causing rotation of turbine blades which in turn cause rotation of the shaft  24 . The shaft  24  passes toward the front of the gas turbine engine  10  to continue rotation of the one or more compressor stages  14 ,  15 , a fan  18  having inlet fan blades  19 , depending on the turbine design. The fan  18  is connected by the shaft  28  to a low pressure turbine  21  and creates thrust for the gas turbine engine  10 . The low pressure turbine  21  may also be utilized to extract further energy and power additional low pressure compressor stages  15 . The low pressurized air from the low pressure compressor  15  may be used to aid in cooling components of the engine as well. 
         [0026]    Referring now to  FIG. 2 , a side section view of exemplary shroud support assembly  30  is depicted. An exemplary turbine is shown, however the instant embodiments are not limited to turbine use. The high pressure turbine  20  ( FIG. 1 ) includes a row of circumferentially spaced stationary vanes (not shown) and a plurality of circumferentially spaced turbine blades  23  downstream axially of the vanes. The turbine blades  23  are foil-shaped and mounted to a turbine rotor disk (not shown). Each of the turbine blades  23  extends radially toward the shroud assembly  30 . The shroud assembly  30  extends circumferentially about the engine axis  26  ( FIG. 1 ) and may be comprised of a plurality of flowpath panels  80  in the circumferential direction. The shroud assembly  30  is tightly configured relative to the turbine blades  23  to improve turbine efficiency so that the shroud assembly  30  defines an outer radial flowpath boundary for the hot combustion gas flowing through the high pressure turbine  20 . Turbine efficiency is based upon the ability of the airfoil surfaces to extract energy from the differential pressure in the combustion gases acting over the pressure and suction sides of the airfoil from root to tip and between the leading and trailing edges. 
         [0027]    The shroud assembly  30  includes an upper shroud hanger  40  which may include various shapes. An engine casing  29  extends circumferentially about the engine axis  26  ( FIG. 1 ). Upper shroud hanger  40  extends from the radially inward side of the engine casing  29  and retains hanger sleeve  70  in circular configuration about the engine axis  26  ( FIG. 1 ). The hanger sleeve or shroud sleeve  70  retains a flowpath panel  80  in position which defines the flow boundary within portions of the gas turbine engine  10 , for non-limiting example, the compressor  14  or high pressure turbine  20 . 
         [0028]    As depicted, the upper shroud hanger  40  is generally U-shaped in section including a first radially extending leg  42 , a second radially extending leg  44  and a third axially extending leg  46  extending between the first and second legs  42 ,  44 . The first and second legs  42 ,  44  extend in a circumferential direction about the engine axis  26 . The upper shroud hanger  40  extends in the circumferential direction. The upper shroud hanger  40  may be formed of metal or alternatively may be formed of ceramic matrix composite material. At radially outward ends of the first and second legs,  42 ,  44  are hooks  48  which engage structures in the engine case  29 . The hooks  48  extend in the axial direction to mate with engaging structure of the engine case  29 . For example, the hooks  48  are generally male while the turbine case includes female receiving structures. Further, while hooks  48  are shown, other structures may be utilized and for example, a male part may be located on the engine case  29  and a female part may be located on the upper shroud hanger  40 . According to alternate embodiments, it is within the scope of the present disclosure that the hanger sleeve  70  may extend to the engine casing  29  and be connected thereto, wherein the upper shroud hanger  40  may be eliminated. 
         [0029]    Multiple support webs or gussets  50  may extend between the first leg  42  and the second leg  44 . The gussets  50  may be spaced apart in the circumferential direction of the upper hanger. The support web or gusset  50  may extend between the first leg  42  and the second leg  44  and may extend axially or may extend at an angle to the central engine axis  26  as depicted. For example, the instant embodiment provides a gusset  50  that is tapered from a lower radial height at the first leg  42  to a higher radial height at the second leg  44 . The gusset  50  may alternatively be tapered in the opposite direction or may extend horizontally. 
         [0030]    The axial leg  46  includes one or more spaced-apart bolt apertures  52  which receive a fastener  54 . The fastener  54  extends through the upper shroud hanger  40  into a retainer or baffle  60 . The retainer  60  captures the hanger sleeve  70  and pulls the hanger sleeve  70  against the upper shroud hanger  40 . The fasteners  54 , for example bolts, may be parallel to one another to reduce bolt bending. This increases bolt durability and results in an improved joint. According to alternative embodiments however, the fasteners  54  may be disposed at an angle relative to each other, for example all extending in the radial direction, for ease of assembly. 
         [0031]    The hanger sleeve  70  extends in a circumferential direction and includes a CMC shroud sleeve forward leg  72  and a CMC hanger sleeve aft leg  74 . The forward leg  72  is formed by a C-shape including an upper portion  71 , a lower portion  73  and radially extending portion  75  between the upper and lower portions  71 ,  73 . Similarly, the aft leg  74  includes an upper portion  76 , a lower portion  77  and a radially extending portion  78  and defines a reverse C-shape in section. The hanger sleeve  70 , upper shroud hanger  40  and shroud flowpath panel  80  include circumferential end faces which are commonly referred to as “slash faces.” The slash faces may lie in plane parallel to the center line axis  26  of the gas turbine engine  10 , referred to as a “radial plane”, or they may be slightly offset from the radial plane, or otherwise oriented so that they are at an acute angle to such radial plane. 
         [0032]    The hanger sleeve  70  is shown having two leg portions  72 ,  74  although this sleeve segment  70  is a one-piece segment as shown in  FIG. 3 . This is due to the location of the section cut in the depicted view. However, one skilled in the art should realize that the hanger sleeve  70  may be formed of a two or more piece structure as described and shown further herein. 
         [0033]    When circumferential segments of the hanger sleeve  70 , flowpath panel  80  segments and upper shroud hanger  40  segments are assembled, complete rings are formed. End gaps may be present between the slash faces of the adjacent segments. One or more seals may be provided at these slash faces. These seals are generally known as “spline” seals formed of thin strips of metal or other suitable materials which are inserted in slots in the end faces to span the gaps between adjacent segments. Additionally, when assembled, the circumferential ends of the upper shroud hanger  40 , the hanger sleeve  70  and the flowpath panel  80  may be aligned or offset or some combination thereof. 
         [0034]    The forward leg  72  and the aft leg  74  are spaced apart at a radial outer end by a window  62 . The forward leg  72  and the aft leg  74  are alternatively joined in a different circumferential location. The hanger sleeve  70  may include one or more windows  62  depending on the circumferential length of the hanger sleeve  70 . The retainer  60  extends through the window  62  and is sized to be of a larger dimension in at least one corresponding dimension to the window  62  so that when the fastener  54  is tightened, the retainer  60  pulls the hanger sleeve  70  radially to the upper shroud hanger  40 . 
         [0035]    The baffle  60  may be, according to some embodiments, an inverted T-shape which engages the upper shroud hanger  40  at one end. The T-shape has a radially extending leg  64  and a transversely extending leg  66 . A cooling air flowpath  68  may extend through the baffle  60  to provide cooling air to the flowpath panel  80  of the CMC shroud. The cooling air flowpath  68  may receive air from the upper shroud hanger  40 . These holes provide shroud cooling air from a known source, for example the compressor, through the retainer baffle  60  and to the flowpath panel  80 . 
         [0036]    The baffle  60  receives the fastener  54  in aperture  61 . The lower surface of the baffle  60  may include one or more cooling apertures, for example arranged in an array, to provide backside impingement cooling to the flowpath panel  80 . 
         [0037]    The transverse leg  66  may include reliefs, slots, or other features  65  adjacent the radially inward end. According to instant embodiment, a seal  67 , such as a leaf seal, is disposed in the feature  65 . The leaf seal  67  forces cooling air from the retainer  60  to cool the upper surface  83  of the flowpath panel  80 . 
         [0038]    Extending between the lower portions  73 ,  77  is a flowpath panel  80 . A lower surface  81  of the flowpath panel  80  is disposed adjacent to the turbine blade  23  while an upper surface  83  is facing the retainer  60  and receives cooling air passing from the retainer  60 . The flowpath panel  80  includes a first shoulder  82  near a forward axial end and a second shoulder  84  near a second rearward axial end. The first shoulder  82  engages the upper surface of the first or forward axial portion  73 . The second shoulder  84  engages the upper surface of the second or rearward axial portion  77 . 
         [0039]    The first shoulder  82  is depicted as horizontal in the section view. Similarly, the second shoulder  84  is also depicted as horizontal. The corresponding contact surfaces of the lower portions  73 ,  77  are also horizontal in the depicted embodiment. The horizontal surfaces of the shoulders  82 ,  84  and the lower portions  73 ,  77  define pressure flats which engage one another. This allows for engagement of the flowpath panel  80  and support between the lower portions  73 ,  77 . The pressure flats may alternatively be angled or tapered surfaces rather than horizontal. 
         [0040]    Extending from the shoulders  82 ,  84  are arms  86 ,  88 . The arms  86 ,  88  may extend radially or may extend at an angle within the bounds of the forward and aft legs  72 ,  74 . The seals  67  extend from the feature areas  65  to the arms  86 ,  88 . The arms  86 ,  88  are spaced apart wider than the spacing between ends of lower portions  73 ,  77 . 
         [0041]    The hanger sleeve  70  and flowpath panel  80  may be formed of various low ductility and low coefficient of thermal expansion materials including, but not limited to, ceramic matrix composite (CMC). Generally, CMC materials include a ceramic fiber, for example a silicon carbide (SiC), forms of which are coated with a compliant material such as boron nitride (BN). The fibers are coated in a ceramic type matrix, one form of which is silicon carbide (SiC). Typically, the shroud hanger  40  can also be constructed of other low-ductility, high-temperature-capable materials. CMC materials generally have room temperature tensile ductility of less than or equal to about 1% which is used herein to define a low tensile ductility material. Generally, CMC materials have a room temperature tensile ductility in the range of about 0.4% to about 0.7%. 
         [0042]    CMC materials have a characteristic wherein the materials tensile strength in the direction parallel to the length of the fibers (the “fiber direction”) is stronger than the tensile strength in the direction perpendicular. This perpendicular direction may include matrix, interlaminar, secondary or tertiary fiber directions. Various physical properties may also differ between the fiber and the matrix directions. 
         [0043]    At least the lower exterior surfaces of the lower portions  73 ,  77  and the lower surface  81  of the flowpath panel  80  may also incorporate a layer of environmental barrier coating, which may be an abradable material, and/or a rub-tolerant material of a known type suitable for use with CMC materials. This layer is sometimes referred to as a “rub coat”. As used herein, the term “abradable” implies that the rub coat is capable of being abraded, ground, or eroded away during contact with the tips of the turbine blades  23  as they turn inside the flowpath panel  80  extending at high speed, with little or no resulting damage to the turbine blade tips. This abradable property may be a result of the material composition of the rub coat, by its physical configuration or by some combination thereof. The rub coat may include a ceramic layer such as yttria stabilized zirconia or barium strontium aluminosilicate. 
         [0044]    Referring now to  FIG. 3 , is an isometric view of the shroud hanger sleeve  70 . The hanger sleeve  70  extends circumferentially and is shown as a segment  79 . The segment  79  may be of a length to extend completely circumferentially as a single structure. Alternatively, as depicted, the segment  79  may be shorter wherein the multiple segments are utilized to surround the high pressure turbine  20 . 
         [0045]    Also, as shown, the hanger sleeve  70  includes the windows  62  in the upper surface  63 . The windows  62  may be formed of various sizes and are defined by structures defining the windows  62 . The upper surface  63  of the structures may be of various widths in the circumferential direction and/or may be spaced apart at different distances in the circumferential direction. The upper surface  63  width or spacing may be dependent upon loading, retainer  60  size, ducting of cooling air from the upper shroud hanger  40  and other variables. For example, the depicted segment  79  may have a single window  62  which may be centered or may have a centered arrangement, as shown in  FIG. 4  or may be off-center. Alternatively, the segment  79  may have two or more windows  62 . Further, the one or more windows  62  may extend to the circumferential end of the sleeve segment  79  so as to mate with an adjacent window of an adjacent segment and define a larger window, as depicted in  FIG. 5 . 
         [0046]    Referring now to  FIG. 6 , an isometric view of the flowpath panel  80  removed from the hanger sleeve  70  is depicted. The flow panel lower surface  81  and the upper surface  83  may be curved as shown or alternatively, may be linear so that a plurality of flowpath panels  80  can approximate the circumferential shape of the high pressure turbine  20 . 
         [0047]    The flowpath panel  80  also includes shoulders  82 ,  84  which define the flat pressure surfaces. The shoulders  82 ,  84  and arms  86 ,  88  retain the flowpath panel  80  within the opening  69  ( FIG. 5 ) of the hanger sleeve  70  between lower portions  73 ,  77 . While the panel utilizes a right angle architecture between the shoulders  82 ,  84  and a sidewall of the panel extending from the lower surface  81 , other architectures may be utilized. For example, the flowpath panel  80  may include an angled pressure flat so that the angle between the shoulder surface and the sidewall is not 90 degrees. The sidewalls extending from the lower surface  81  may also be angled, rather than extending from the lower surface at 90 degrees. Various alternative shapes may be used to provide for retaining engagement between the flowpath panel  80  and the hanger sleeve  70 . 
         [0048]    The upper panel surface  83  also receives cooling air from the retainer  60 , above. The impingement cooling air aids to maintain the temperature of the flowpath panel  80  at a suitable temperature or within a suitable operating range. 
         [0049]    The flowpath panel  80  is dimensioned so that when the shoulders  82 ,  84  are seated, the lower surface  81  is flush with the lower surface of the lower portions  73 ,  77 . 
         [0050]    As shown herein, the joints between walls are generally radiused which may improve manufacture of the part. However, other arrangements such as sharp angle corners may be used. 
         [0051]    Referring now to  FIG. 7 , a second embodiment of the shroud assembly  130  is depicted. At an upper end of the shroud assembly  130  is an upper shroud hanger  140  having a first leg  142  and a second leg  144  similar to the previously described embodiment. The upper ends of the first and second legs  142 ,  144  include hooks  148  for connection with an engine casing  129 . Extending between the first leg  142  and the second leg  144  is a shroud hanger base  147 . In combination with the first and second legs  142 ,  144 , the hanger base  147  forms a U-shape for the upper shroud hanger  140 . Extending between the first and second legs  142 ,  144  is a support web or gusset  150 . Passing through the upper shroud hanger  140  is a cooling flowpath  168 . 
         [0052]    Depending from the hanger base  147  is an alternative retainer  160  which is integrally formed with the upper shroud hanger  140 . Depending from the shroud hanger  140  is a first retainer leg  164  and a second retainer leg  166 . As with the previously described structures, the legs  164 ,  166  extend circumferentially with the segment structure defining a portion or all of the upper shroud hanger  140 . 
         [0053]    Connected to the retaining legs  164 ,  166  is an alternative embodiment of the CMC hanger sleeve  170 . The hanger sleeve  170  is defined by separated first and second CMC hanger sleeve legs  172 ,  174 . The legs  172 ,  174  extend in a radial direction and in a circumferential direction and are fastened to the retainer legs  164 ,  166 . The first CMC hanger sleeve leg  172  and second CMC hanger sleeve leg  174  include lower ends which engage the flowpath panel  180 . The flowpath panel  180  has shoulders. The shoulders  182 ,  184  are formed and have surfaces which engage corresponding surfaces of legs  172 ,  174 . 
         [0054]    A leaf seal  167  may extend between the U-shaped flowpath panel  180  and the upper shroud hanger  140 . The cooling flowpath  168  allows a path through the open shroud hanger  140  and between the retaining legs  164 ,  166  to provide impingement cooling to the flowpath panel  180 . 
         [0055]    The foregoing description of structures and methods has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the structures and methods to the precise forms and/or steps disclosed, and obviously many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. It is understood that while certain forms of composite structures have been illustrated and described, it is not limited thereto and instead will only be limited by the claims, appended hereto. 
         [0056]    While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. 
         [0057]    Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. 
         [0058]    All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. 
         [0059]    It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.