Patent Publication Number: US-10316687-B2

Title: Blade track assembly with turbine tip clearance control

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/135,443, filed Dec. 19, 2013, which claimed the benefit of U.S. Provisional Patent Application Ser. No. 61/786,187, filed Mar. 14, 2013, both of which are incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to gas turbine engines, and more specifically to turbine shrouds used in gas turbine engines. 
     BACKGROUND 
     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. 
     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 shrouds that are arranged around the rotating wheel assemblies. 
     During operation, the tips of the blades included in the rotating wheel assemblies typically move inwardly and outwardly relative to a centerline of the engine due to changes in centrifugal force and temperatures experienced by the blades. Because of this movement inwardly and outwardly relative to the centerline, turbine shrouds are often designed to allow clearance between the blade tips and the blade tracks. This clearance may allow combustion products to pass over the blades without pushing the blades, thereby contributing to lost performance within a gas turbine engine. In some designs, the blade tips contact the blade tracks arranged around the rotating wheel assemblies and cut grooves into the blade tracks further contributing to lost performance within a gas turbine engine. 
     SUMMARY 
     The present disclosure may comprise one or more of the following features and combinations thereof. 
     A turbine shroud or blade track assembly adapted to extend around a turbine wheel assembly is disclosed. The turbine shroud includes a carrier and a blade track coupled to the carrier. The blade track is movable between a radially-inward position having a first inner diameter and a radially-outward position having a second inner diameter larger than the first inner diameter. The movable blade track accommodates the movement of blades included in the turbine wheel assembly due to changes in centrifugal force and temperatures experienced by the blades during use of the turbine wheel assembly in a gas turbine engine. 
     According to one aspect of the present disclosure, a turbine shroud may include a carrier arranged around an axis, a blade track concentric with the carrier, and an actuator configured to change size in response to a change in temperature. The carrier may be formed to include a first guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The blade track may be movable between a radially-inward position having a first inner diameter and a radially-outward position having a second inner diameter larger than the first inner diameter. The actuator may be coupled to the blade track to move the blade track between the radially-inward position and the radially-outward position when the actuator changes size in response to a change in temperature. 
     In some embodiments, the actuator may be coupled to the carrier by a mover pin that extends from the actuator into the first guide slot so that the blade track moves along a portion of the circumference of the carrier around the axis when the actuator changes size. The mover pin may extend to a blade track segment included in the blade track to couple the blade track to the actuator. The actuator may be a ring configured to change diameter in response to a change in temperature. The actuator may be an arm configured to change length in response to a change in temperature. 
     In some embodiments, the carrier may be formed to include a second guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The first guide slot and the second guide slot may be arcuate when viewed in the axial direction. 
     In some embodiments, a guide pin may extend through a blade track segment and into the second guide slot. The carrier may include a first side wall and a second side wall spaced apart from the first side wall in an axial direction. The first guide slot may be formed in the first side wall and the second guide slot may be formed in the second side wall so that the second guide slot is spaced apart from the first guide slot in the axial direction. 
     In some embodiments, the blade track may include a plurality of blade track segments that move circumferentially away from one another when the blade track moves from the radially-inward position to the radially-outward position. The blade track may include a plurality of strip seals that extend circumferentially between adjacent blade track segments. 
     According to another aspect of the present disclosure, a turbine shroud may include a carrier arranged around an axis, a blade track concentric with the carrier, and an actuator ring arranged around the axis. The carrier may be formed to include a first guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The blade track may be movable between a radially-inward position having a first inner diameter and a radially-outward position having a second inner diameter larger than the first inner diameter. The actuator ring may be configured to change diameter in response to a change in temperature. The actuator ring may be coupled to the blade track to move the blade track between the radially-inward position and the radially-outward position when the actuator ring changes diameter in response to a change in temperature. 
     In some embodiments, the actuator ring may be coupled to the carrier by a mover pin that extends from the actuator ring into the first guide slot so that the actuator ring and the blade track move along a portion of the circumference of the carrier around the axis when the actuator ring changes diameter. The mover pin may extend to a blade track segment included in the blade track to couple the blade track to the actuator ring. The carrier may be formed to include a second guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. A guide pin may extend through a blade track segment and into the second guide slot. The second guide slot may be spaced circumferentially apart from the first guide slot. 
     In some embodiments, the blade track may include a plurality of blade track segments that move circumferentially away from one another when the blade track moves from the radially-inward position to the radially-outward position. Each blade track segment may be formed to include a shroud wall that partially defines the inner diameter of the blade track and a first wall that extends outwardly in the radial direction from the shroud wall. In some embodiments, the mover pin may extend through the first wall of a blade track segment to couple the blade track segment to the actuator ring. 
     In some embodiments, each blade track segment may be formed to include a second wall spaced apart from the first wall in an axial direction that extends outwardly in the radial direction from the shroud wall. The carrier may be formed to include a second guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The mover pin may extend through the first wall of a first blade track segment to couple the blade track segment to the actuator ring. A guide pin may extend through the second wall of the first blade track segment and into the second guide slot. 
     According to another aspect of the present disclosure, a turbine shroud may include a carrier arranged around an axis, a blade track concentric with the carrier, and an actuator arm configured to change length in response to a change in temperature. The carrier may be formed to include a first guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The blade track may be movable between a radially-inward position having a first inner diameter and a radially-outward position having a second inner diameter larger than the first inner diameter. The actuator arm may be coupled to the blade track to move the blade track between the radially-inward position and the radially-outward position when the actuator arm changes length in response to a change in temperature. 
     In some embodiments, the actuator arm may be coupled to the carrier by a mover pin that extends from the actuator arm into the first guide slot so that the blade track moves in a radial direction when the actuator arm changes length in response to a change in temperature. The actuator arm may be coupled to the carrier for movement about a pivot axis spaced apart from the mover pin. The mover pin may be coupled to the actuator arm at a first end of the actuator arm and the pivot axis may extend through the actuator arm at a second end of the actuator arm. The mover pin may extend to a blade track segment included in the blade track to couple the blade track to the actuator arm. 
     In some embodiments, the carrier may be formed to include a second guide slot extending outward in a radial direction from the axis and along a portion of the circumference of the carrier. The first guide slot and the second guide slot may be arcuate when viewed in the axial direction. A guide pin may extend through a blade track segment and into the second guide slot. 
     In some embodiments, the carrier may include a first side wall and a second side wall spaced apart from the first side wall in an axial direction. The first guide slot may be formed in the first side wall and the second guide slot may be formed in the second side wall so that the second guide slot is spaced apart from the first guide slot in the axial direction. 
     In some embodiments, the blade track may include a plurality of blade track segments that move circumferentially away from one another when the blade track moves from the radially-inward position to the radially-outward position. The blade track may include a plurality of strip seals that extend circumferentially between adjacent blade track segments. 
     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 
         FIG. 1  is a cut-away perspective view of a gas turbine engine; 
         FIG. 2  is a cross-sectional view of a portion of the gas turbine engine of  FIG. 1  showing that the gas turbine engine includes a turbine wheel and a turbine shroud providing a blade track extending around the turbine wheel; 
         FIG. 3  is a detail view of a portion of the cross-sectional view of  FIG. 2  showing that the turbine shroud includes a carrier mounted to a turbine case, the blade track coupled to the carrier and arranged around the turbine wheel, and an actuator ring coupled to both the carrier and the blade track; 
         FIG. 4  is an exploded perspective view of a portion of the turbine shroud of  FIG. 3  showing that the blade track is made up of a plurality of blade track segments; 
         FIG. 5  is a side elevation view of a portion of the turbine shroud shown in  FIG. 3  showing the blade track in a radially-inward position when the actuator ring is contracted to a relatively-small diameter; 
         FIG. 6  is a view similar to  FIG. 5  showing the blade track in a radially-outward position when the actuator ring is expanded to a relatively-large diameter; 
         FIG. 7  is a cross-sectional view of a portion of another a turbine shroud incorporated into the gas turbine engine of  FIGS. 1 and 2 ; 
         FIG. 8  is a detail view of a portion of the cross-sectional view of  FIG. 7  showing that the turbine shroud includes a carrier mounted to a turbine case, the blade track coupled to the carrier and arranged around the turbine wheel, and an actuation ring coupled to both the carrier and the blade track; 
         FIG. 9  is a side elevation view of a portion of the turbine shroud shown in  FIG. 8  showing the blade track in a radially-inward position when the actuation arm is contracted to a relatively-short length; and 
         FIG. 10  is a view similar to  FIG. 9  showing the blade track in a radially-outward position when the actuator ring is expanded to a relatively-long length. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     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. 
       FIG. 1  is an illustrative aerospace gas turbine engine  110  cut-away to show that the engine  110  includes a fan  112 , a compressor  114 , a combustor  116 , and a turbine  118  all mounted to a case  120 . The fan  112  is driven by the turbine  118  to provide thrust. The compressor  114  compresses and delivers air to the combustor  116 . The combustor  116  mixes fuel with the compressed air received from the compressor  114  and ignites the fuel to produce hot, high-pressures gas. The hot, high-pressure gas from burning fuel in the combustor  116  is directed into the turbine  118  and the turbine  118  extracts work to drive the compressor  114  and the fan  112 . 
     The turbine  118  illustratively includes a first static vane assembly  122 , a first turbine wheel assembly  124 , and a second static vane assembly  126  as shown in  FIG. 2 . The first static vane assembly  122  extends across the flow path of the hot, high-pressure gas from the combustor  116  to direct the gas toward blades  134  included in the first turbine wheel assembly  124 . The blades  134  are in turn pushed by the combustion products to cause the first turbine wheel assembly  124  to rotate; thereby, driving the rotating components of the compressor  114  and the fan  112 . 
     The turbine  118  may also include a turbine shroud  10  with a blade track  14  that extends around the first turbine wheel assembly  124  to block combustion products from passing over tips  135  of the blades  134  without pushing the blades  134  to rotate as shown in  FIGS. 2 and 3 . The illustrative turbine shroud  10  may be adjustable to control the amount of blade tip clearance between the tips  135  of the blades  134  and the blade track  14  included in the turbine shroud  10 . Thus, the amount of hot, high-pressure gas that is allowed to pass over the tips  135  of the blades  134  without pushing the blades  134  can be managed as the first turbine wheel assembly  124  expands and contracts during operation of the gas turbine engine  110 . 
     The turbine shroud  10 , sometimes called an adjustable blade track assembly, may include a carrier  12 , the blade track  14 , and an actuator ring  16  as shown, for example, in  FIGS. 3 and 4 . The carrier  12  may be configured to support the blade track  14  in position adjacent to the blades  134  of the first turbine wheel assembly  124  and may guide movement of the blade track  14  and actuator ring  16  during adjustment. The illustrative blade track  14  may be generally concentric with the carrier  12  and may be movable relative to the carrier  12  from a radially-inward position (shown in  FIG. 5 ) having a relatively-small diameter to a radially-outward position (shown in  FIG. 6 ) having a relatively-large diameter. The actuator ring  16  may be coupled to both the carrier  12  and the blade track  14  to move the blade track  14  relative to the carrier  12  outwardly and inwardly in the radial direction as the actuator ring  16  is heated to expand or cooled to contract. 
     The actuator ring  16  may be coupled to the carrier  12  by a series of mover pins  26  received in guide slots  31 ,  41  formed in the carrier  12  as shown, for example, in  FIGS. 5 and 6 . The guide slots  31 ,  41  may extend outward in the radial direction from an axis  11  of the gas turbine engine  110  and along a portion of the circumference of the carrier  12 . Thus, as the actuator ring  16  expands or contracts in diameter to move the blade track  14  outwardly or inwardly in the radial direction, the mover pin  26  may cause the actuator ring  16  and the blade track  14  coupled to the actuator ring  16  to rotate circumferentially along a portion of the circumference of the carrier  12  as suggested by arrows  141 ,  161  in  FIG. 6 . 
     The carrier  12  may be an annular, round metallic component and may include a top wall  20 , a first side wall  22 , and a second side wall  24  as shown, for example, in  FIG. 4 . The top wall  20  may be coupled to the case  120  of the gas turbine engine  110 . The first side wall  22  and the second side wall  24  may be spaced apart from one another in the axial direction and may extend inwardly in the radial direction from the top wall  20  so that the carrier  12  forms a radially-inwardly-opening, annular channel  25 . In the illustrative embodiment, the carrier  12  may be made from a number of segments and in other embodiments may be a monolithic component. 
     The first side wall  22  of the carrier  12  may be formed to include a series of guide slot pairs  30  having a radially-outer guide slot  31  and a radially-inner guide slot  32  as shown in  FIG. 4 . The second side wall  24  of the carrier  12  may be similarly formed to include a series of slot pairs  40  having a radially-outer guide slot  41  and a radially-inner guide slot  42 . The radially-outer guide slots  31 ,  41  may be axially aligned to receive the mover pin  26  that extends axially across the carrier  12 . The radially-inner guide slots  32 ,  42  may be spaced apart axially and may receive guide pins  36 ,  46  that extend to the blade track  14  to guide the blade track  14  during movement induced by expansion or contraction of the actuator ring  16 . In illustrative embodiments, each guide slot  31 ,  32 ,  41 ,  42  may be arcuate when viewed in the axial direction. However, in other embodiments, each guide slot may be generally linear or may have another shape. 
     The blade track  14  may include a plurality of blade track segments  44  that cooperate to form a substantially annular blade track  14  as suggested in  FIGS. 4-6 . Each blade track segment  44  may be formed to include a shroud wall  50 , a first wall  52 , and a second wall  54  as shown in  FIG. 4 . The shroud wall  50  may partially define the inner diameter of the blade track  14 . The first wall  52  and the second wall  54  are spaced apart axially and extend outwardly in the radial direction from the shroud wall  50 . The second wall  54  may extend further in the radial direction from the shroud wall  50  than the first wall  52 . 
     The mover pins  26  may extend through corresponding holes  27  formed in the second wall  54  of each blade track segment  44 , through the actuator ring  16 , and into the radially-outer guide slots  31 ,  41  of the carrier  12  as suggested in  FIGS. 3 and 4 . Thus, each blade track segment  44  is coupled to the actuator ring  16  for movement in the radial direction upon expansion or contraction of the actuator ring  16  and will rotate with the actuator ring  16  on account of the mover pins  26  captured in the radially-outer guide slots  31 ,  41  of the carrier  12 . 
     The guide pins  36 ,  46  may extend through corresponding holes  37 ,  47  formed in the first wall  52  and the second wall  54  of each blade track segment  44  (respectively) and into one of the radially-inner guide slots  32 ,  42  formed in the carrier  12  (respectively) as suggested in  FIGS. 3 and 4 . Thus, each blade track segment  44  is coupled to the carrier  12  at circumferential locations spaced apart from the mover pin  26  so that each blade track segment  44  remains in proper orientation with the shroud walls  50  facing the engine centerline  11  during expansion and contraction of the actuator ring  16  as it moves the blade track  14  between the radially-inward position (shown in  FIG. 5 ) and the radially outward position (shown in  FIG. 6 ). 
     In the illustrative embodiment, the blade track segments may each be made from a ceramic material; and, more particularly, a ceramic matrix composite (CMC). For purposes of this application, a ceramic material may be any monolithic ceramic or composite in which at least one constituent is a ceramic. In other embodiments, the blade track segments  44  may be made of other metallic, non-metallic, or composite materials. 
     Bushings  29 ,  39 ,  49  may be mounted in corresponding holes  27 ,  37 ,  47  formed in each blade track segment  44  as suggested in  FIG. 4 . The bushings  29 ,  39 ,  49  may be made from a ceramic or metallic material and may provide a bearing surface upon which pins  26 ,  36 ,  46  can rotate. 
     The actuator ring  16  (sometimes called an expansion ring or an actuator) may be arranged in the channel  25  formed by the carrier  12  as shown in  FIG. 3 . The actuator ring  16  may have a rectangular cross-section and may be formed to include holes  56  through which the mover pins  26  may extend. The actuator ring  16  may be made from a metallic material selected based on the material coefficient of thermal expansion. The selected material may provide a specific amount of expansion and contraction across a temperature range corresponding to a subset of engine operating temperatures. In illustrative embodiments, the actuator ring  16  may be a monolithic annular component. However in other embodiments, the actuator ring  16  may be segmented into two or more parts that form an annular (or substantially annular) ring. 
     During operation of the gas turbine engine  110 , the inner diameter of the blade track  14  is adjusted to control the distance (if any) between the tips  135  of the blades  134  to maintain a high level of efficiency across the turbine  118 . To control the inner diameter of the blade track  14 , the blade track segments  44  are moved outwardly and inwardly in the radial direction by expansion and contraction of the actuator ring  16  as suggested in  FIGS. 5 and 6 . 
     To cause expansion and contraction of the actuator ring  16 , the temperature of the actuator ring  16  may be controlled by a temperature control system (not shown). As the actuation ring  16  heats or cools it will expand and contract so that the diameter of the actuation ring  16  changes. The temperature control system (not shown) may include a source of cooling air, one or more temperature sensors arranged to determine the temperature of the cooling air or the actuation ring  16 , one or more flow control valves, and a controller coupled to the temperature sensors and flow control valves. The controller configured to adjust the diameter of the actuator ring  16  by controlling the cooling flow rate so that the actuator ring  16  is maintained at a selected temperature. The selected temperature can be provided in a lookup table or calculated based on the expected diameter of the first stage turbine wheel  124 . 
     When the blade track  14  is moved to the radially-inward position shown in  FIG. 5 , the actuator ring  16  may have been contracted to a relatively-small diameter by cooling the actuator ring  16 . Also, the pins  26 ,  36 ,  46  may be moved to a first end of the respective guide slots  27 ,  37 ,  47  that receive the pins  26 ,  36 ,  46 . Further, the blade track segments  44  may be spaced circumferentially apart (if at all) a first distance  64  as shown in  FIG. 5 . 
     When the blade track  14  is moved to the radially-outward position shown in  FIG. 6 , the actuator ring  16  may have been expanded to a relatively-large diameter by heating the actuator ring  16 . Also, the pins  26 ,  36 ,  46  may be moved to a second end of the respective guide slots  27 ,  37 ,  47  that receive the pins  26 ,  36 ,  46 . Further, the blade track segments  44  may be spaced circumferentially apart a second distance  66  which is larger than the first distance  64  as shown in  FIGS. 5 and 6 . 
     Another illustrative turbine shroud  210  adapted for use in the gas turbine engine  110  is shown in  FIGS. 7-10 . The turbine shroud  210  is substantially similar to the turbine shroud  10  shown in  FIGS. 1-6  described herein. Accordingly, similar reference numbers in the 200 series indicate several features that are common between the turbine shroud  10  and the turbine shroud  210 . The description of the turbine shroud  10  is hereby incorporated by reference to apply to the turbine shroud  210 , except in instances when it conflicts with the specific description and drawings of turbine shroud  210 . 
     Unlike the turbine shroud  10 , the turbine shroud  210  includes a plurality of actuator arms  216  instead of an actuation ring  16  as shown in  FIGS. 8 and 9 . The actuator arms  216  may be configured to expand and contract in length to cause the blade track  214  to move between the radially-inward position and the radially-outward position. 
     The actuator arms  216  may be coupled to the carrier  212  by a series of mover pins  226  received in guide slots  231 ,  241  formed in the carrier  212  as shown, for example, in  FIG. 8 . The guide slots  231 ,  241  may extend outward in the radial direction from an axis  11  of the gas turbine engine  110  and along a portion of the circumference of the carrier  212 . Thus, as the actuator arms  216  expands or contracts in length to move the blade track  14  circumferentially around a portion of the carrier  212 , the mover pins  226  may cause the blade track  214  coupled to the actuator ring  216  to move radially inwardly or outwardly as suggested in  FIGS. 9 and 10 . 
     The actuator arms  216  (sometimes called expansion arms or actuators) may be arranged in the channel  225  formed by the carrier  212  as shown in  FIG. 8 . The actuator arms  216  may each be coupled at a first end to a pivot mount  280  attached to the top wall  220  of the carrier  212  to pivot about a pivot axis  281  relative to the carrier  212 . The mover pins  226  may extend through the actuator arms  216  at a second end, opposite the first end, and into the guide slots  231 ,  241  of the carrier  212 . The actuator arms  216  may be made from a metallic material selected based on the material coefficient of thermal expansion. The selected material may provide a specific amount of expansion/contraction across a temperature range corresponding to a subset of engine operating temperatures. 
     Also, unlike the turbine shroud  10 , the turbine shroud  210  may not incorporate guide pins that extend from both side walls  252 ,  254  of each blade track segment  244  included in the blade track  214 . Rather, the turbine shroud  210  may include only a single guide pin  236  that extends from the first side wall  252  of each blade track segment  244  and into a corresponding radially-inner guide slot  232  formed in the carrier  212  as shown in  FIG. 8 . The guide pin  236  may be spaced circumferentially apart from the mover pin  226  to help maintain proper orientation of the blade track segments  244 . 
     During operation of the gas turbine engine  110 , the inner diameter of the blade track  214  is adjusted to control the distance (if any) between the tips  135  of the blades  134  to maintain a high level of efficiency across the turbine  118 . To control the inner diameter of the blade track  214 , the blade track segments  244  are moved outwardly and inwardly in the radial direction by expansion and contraction of the actuator arms  216  as suggested in  FIGS. 9 and 10 . 
     To cause expansion and contraction of the actuator arms  216 , the temperature of the actuator arms  216  may be controlled by a temperature control system (not shown). As the actuation arms  216  heat or cool they will expand or contract so that the length of the actuation arms  216  change. The temperature control system (not shown) may include a source of cooling air, one or more temperature sensors arranged to determine the temperature of the cooling air or the actuation arms  16 , one or more flow control valves, and a controller coupled to the temperature sensors and flow control valves. The controller may be configured to adjust the length of the actuator arms  216  by controlling the cooling flow rate so that the actuator arms  216  are maintained at a selected temperature. The selected temperature can be provided in a lookup table or calculated based on the expected diameter of the first stage turbine wheel  124 . 
     When the blade track  214  is moved to the radially-inward position shown in  FIG. 9 , the actuator arms  216  may have been contracted to a relatively-short length by cooling the actuator arms  216 . Also, the pins  226 ,  236  may be moved to a first end of the guide slots  231 ,  232  that receive the pins  226 ,  236 . Further, the blade track segments  244  may be spaced circumferentially apart (if at all) a first distance  264  as shown in  FIG. 9 . 
     When the blade track  214  is moved to the radially-outward position shown in  FIG. 10 , the actuator arms  216  may have been expanded to a relatively-long length by heating the actuator arms  216 . Also, the pins  226 ,  236  may be moved to a second end of the respective guide slots  231 ,  232  that receive the pins  226 ,  236 . Further, the blade track segments  244  may be spaced circumferentially apart a second distance  266  which is larger than the first distance  264  as shown in  FIGS. 9 and 10 . 
     The turbine shroud  210  may include strip seals  291 ,  292  that extend between circumferentially-adjacent blade track segments  244  included in the blade track  214  as shown in  FIGS. 9 and 10 . The strip seals  291 ,  292  fill the gaps between the circumferentially-adjacent blade track segments  244  and decrease air loss through the gaps. Such strip seals may be incorporated into the turbine shroud  10  in some embodiments. 
     While the disclosure has been illustrated and described with reference to an aerospace gas turbine engine, the teachings are also applicable for use in other types of turbine applications. For example, energy turbines, marine turbines, pumping turbines, and other types of turbines may incorporate the teachings of this disclosure without departure from the scope of the present description. 
     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.