Patent Publication Number: US-8534995-B2

Title: Turbine engine sealing arrangement

Description:
BACKGROUND 
     This application relates generally to an arrangement of gas turbine engine components that facilitates sealing a turbine engine. 
     Gas turbine engines are known and typically include multiple sections, such as a fan section, a compression section, a combustor section, a turbine section, and an exhaust nozzle section. The compressor and turbine sections include blade arrays mounted for a rotation about an engine axis. The blade arrays include multiple individual blades that extend radially from a mounting platform to a blade tip. 
     Rotating the blade arrays compresses air in the compression section. The compressed air mixes with fuel and is combusted in the combustor section. The products of combustion expand to rotatably drive blade arrays in the turbine section. The tips of the individual blades within the rotating blade arrays each establish a seal with another portion of the engine, such as an engine control ring or a blade outer air seal, at a seal interface. The sealing relationship between the individual blade and the other portion of the engine facilitates compression of the air and expansion of the products of combustion. Maintaining the integrity of the components near the sealing interface helps maintain the sealing relationship. 
     As known, cooling air removes thermal byproducts from the engine, but many components are still exposed to extreme temperatures and temperature variations. Exposing a single monolithic component to varied temperatures can result in uneven expansion of that component, which can affect the integrity of that component by, for example, disrupting the mounting of the component or causing the component to fracture. Disadvantageously, components made of materials capable of withstanding extremely high temperatures often fail when exposed to varied temperatures, and components made of materials capable of withstanding varied temperatures often fail when exposed to extreme temperatures. 
     SUMMARY 
     An example turbine engine sealing arrangement includes a blade array rotatable about an axis. The blade array has a plurality of blades extending radially from the axis. A control ring is circumferentially disposed about the blade array. A plurality of tiles are secured relative to the control ring and configured to establish an axially extending seal with one of the blades. 
     Another example turbine engine cladding arrangement includes a first tile mountable to a control ring of a turbine engine and a second tile mountable to the control ring. The first tile is configured to be positioned axially adjacent to the second tile in the turbine engine. The first tile and the second tile together provide a portion of a sealing interface with a blade of the turbine engine. 
     A method of sealing a portion of a turbine engine includes securing a first tile relative to a control ring and securing a second tile relative to a control ring. The second tile is positioned axially adjacent the first tile. The method includes establishing a seal with a blade using the first tile and the second tile. 
     These and other features of the example disclosure can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic view of an example gas turbine engine. 
         FIG. 2  shows a perspective view of a portion of a sealing arrangement from the  FIG. 1  engine. 
         FIG. 3  shows an exploded view of a cladding and a seal from the  FIG. 2  sealing arrangement. 
         FIG. 4  shows a section view through the sealing arrangement portion of the  FIG. 1  engine. 
         FIG. 5  shows a section view at line  5 - 5  of  FIG. 4  having a cutaway portion. 
         FIG. 6A  shows a section view at line  6 - 6  of  FIG. 4  showing an example cladding arrangement. 
         FIG. 6B  shows a section view at line  6 - 6  of  FIG. 4  showing an alternative cladding arrangement. 
         FIG. 6C  shows a section view at line  6 - 6  of  FIG. 4  showing another alternative cladding arrangement. 
         FIG. 6D  shows a section view at line  6 - 6  of  FIG. 4  showing yet another alternative cladding arrangement. 
         FIG. 7  shows a perspective view of an alternative sealing arrangement from the  FIG. 1  engine. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates an example gas turbine engine  10  including (in serial flow communication) a fan section  14 , a low-pressure compressor  18 , a high-pressure compressor  22 , a combustor  26 , a high-pressure turbine  30 , and a low-pressure turbine  34 . The gas turbine engine  10  is circumferentially disposed about an engine centerline X. During operation, air is pulled into the gas turbine engine  10  by the fan section  14 , pressurized by the compressors  18  and  22 , mixed with fuel, and burned in the combustor  26 . The turbines  30  and  34  extract energy from the hot combustion gases flowing from the combustor  26 . 
     In a two-spool design, the high-pressure turbine  30  utilizes the extracted energy from the hot combustion gases to power the high-pressure compressor  22  through a high speed shaft  38 . The low-pressure turbine  34  utilizes the extracted energy from the hot combustion gases to power the low-pressure compressor  18  and the fan section  14  through a low speed shaft  42 . The examples described in this disclosure are not limited to the two-spool engine architecture described and may be used in other architectures, such as a single-spool axial design, a three-spool axial design, and still other architectures. That is, there are various types of engines that could benefit from the examples disclosed herein, which are not limited to the design shown. 
     Referring now to  FIGS. 2-4  with continuing reference to  FIG. 1 , an example sealing arrangement  48  within the engine  10  includes a blade  50  having a blade tip portion  54  that is configured to seal against a cladding  58  carried by a control ring  62 . A sealing interface  66  is established between the blade tip  54  and the cladding  58  when the blade tip  54  seals against the cladding  58 . The example cladding  58  includes a first outer tile  70 , an inner tile  74 , and a second outer tile  78 . Other examples include other arrangements of tiles. 
     In this example, the axial length of the sealing interface  66  generally corresponds to the axial length of the blade tip  54 . The sealing interface  66  also axially extends from the first outer tile  70 , across the inner tile  74 , to the second outer tile  78 . That is, the blade tip  54  is configured to establish the sealing interface  66  with cladding  58  having multiple individual tiles, rather than a single tile. 
     The example cladding  58  is ceramic. In another example, one or more of the first outer tile  70 , the inner tile  74 , or the second outer tile  78  have another composition, such as a ceramic matrix composite. 
     To hold the position of the cladding  58 , the example cladding  58  slidingly engages the control ring  62 . More specifically, in this example, the cladding  58  establishes a groove  82  that is operative to receive a corresponding extension  86  of the control ring  62 . The first outer tile  70  and the second outer tile  78  further include a flange  90  directed radially outward that act as stops to limit axial movements of the cladding  58  relative to the control ring  62 . 
     In this example, securing the cladding  58  relative to the control ring  62  involves first sliding the inner tile  74  axially such that the extension  86  of the control ring  62  is received within the groove  82  of the inner tile  74 . Next, the first outer tile  70  and the second outer tile  78  are slid over corresponding portions of the extension  86 . 
     As can be appreciated from the figures, the example extension  86  and the example groove  82  have a tongue and groove type relationship that limits relative radial movement between the cladding  58  and the control ring  62  when the extension  86  is received within the groove  82 . In another example, the control ring  62  establishes a groove operative to receive an extension of the cladding. 
     Other portions of the engine  10 , such as a vane section  94  upstream from the control ring  62  limit axial movement of the cladding  58  away from the control ring  62 . In one example, a portion  98  of the engine  10  is spring loaded such that the portion  98  biases the cladding  58  in an upstream direction toward the vane section  94 . 
     The example inner tile  74  and outer tiles  70  and  78  each include a surface  99  facing the blade tip  54  that is about 2-3 centimeters by 2-3 centimeters. The minimum depth of the inner tile  74  and outer tiles  70  and  78  is about 1 centimeter, for example. 
     In this example, a plurality of hangers  102  extend from an outer casing  106  of the engine  10  to hold the control ring  62  within the engine  10 . The hangers  102  are circumferentially disposed about the control ring  62 . In one example, the control ring  62  is made of a ceramic material. In another example, the control ring  62  comprises a ceramic metal composite. Cooling airflow moves between the outer casing  106  and the control ring  62  as is known. 
     Portions of the cladding  58  are radially spaced from the control ring  62  when the extension  86  is received within the groove  82  to provide a cleared area  100  between the control ring  62  and the cladding  58 . In some examples, no cooling airflow near the sealing interface  66  is required, which forces the cladding  58  to operate in a higher temperature environment. The cladding  58  is still able to seal with the blade  50  in such an environment at least because the cladding  58  withstands the higher temperatures more effectively than a monolithic structure. In one example, cooling airflow moves to the cleared area  100  to cool the sealing interface  66 , especially the cladding  58 . 
     A seal plate  108  provides a seal near the cleared area  100  that blocks flow of air between the cleared area  100  and another portion of the engine  10 . Compression forces within the engine  10  force the seal plate  108  radially inward against the control ring  62  and the cladding, which enhances the effectiveness of the associated seal. In one example, the seal is a cobalt alloy seal. Other examples may include a ceramic matrix composite seal. 
     In this example, the cladding  58  is arranged in axially extending rows  114  on the control ring  62 . The example seal  108  extends axially to contact each of the first outer tile  70 , the inner tile  74 , and the second outer tile  78  of the cladding  58 . The example rows  114  are circumferentially distributed around the control ring  62 . 
     In the  FIG. 6A  example, the inner tile  74  meets the first outer tile  70  and the second outer tile  78  at tile interfaces  126 , which are aligned with the tile interfaces  126  of adjacent rows  114 . In the  FIG. 6B  example, some of the rows  114  include two inner tiles  74 , and the tile interfaces  126  of adjacent rows  114  are staggered. In both the  FIGS. 6A and 6B  examples, the rows are generally aligned with the engine centerline X. 
     In the  FIG. 6C  example, the rows  114  extend in an arc relative to the engine centerline X. In the  FIG. 6D  example, the rows  114  are disposed at an angle θ relative to the engine centerline X. Other examples include other arrangements of the cladding  58 . 
     As shown in  FIG. 7 , in some examples, a plurality of clips  130  are secured to the control ring  136  and the cladding  58  is slidingly received over the clips  130 , rather than the extension  86  ( FIG. 2 ) to hold the cladding  58  relative to the control ring  136 . 
     Features of the disclosed examples include using cladding consisting of multiple components, such as tiles, to provide a sealing interface with a blade rather than a cladding consisting of a single monolithic structure that can crack in response to temperature variations. Another feature of the disclosed example is simplified method of securing the cladding relative to other portions of an engine. Yet another feature is to size the tiles such that internal flaws created during manufacturing are minimized, and process yields are increased. 
     Although an exemplary embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.