Abstract:
A method for assembling an expansion joint includes providing a first seal retainer, positioning an annular first seal at least partially within the first seal retainer such that the first seal extends between the first seal retainer first and second ends and substantially fills the first seal retainer cavity, providing a second seal retainer, positioning an annular second seal at least partially within the second seal retainer such that the second seal extends between the second seal retainer first and second ends and substantially fills the second seal retainer cavity, coupling a bellows to the first and second seal retainers, and slidably coupling a unitary annular shroud the first and second seal retainers such that the shroud substantially circumscribes the first and second seal retainers, and such that the bellows is operable in conjunction with the annular shroud and the first and second seal retainers.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engines, and, more specifically, to expansion joints therein for accommodating differential thermal movement of fluid carrying components.  
         [0002]     Gas turbine engines generally include, in serial flow arrangement, a high-pressure compressor for compressing air flowing through the engine, a combustor in which fuel is mixed with the compressed air and ignited to form a high temperature gas stream, and a high pressure turbine. The high-pressure compressor, combustor and high-pressure turbine are sometimes collectively referred to as the core engine. Such gas turbine engines also may include a low-pressure compressor, or booster, for supplying compressed air to the high pressure compressor.  
         [0003]     At least one known gas turbine engine utilizes compressed air, from the compressor, to facilitate cooling various gas turbine engine components. More specifically, compressed air is channeled from the compressor, through various conduits and joints, to the turbine to facilitate cooling components within the turbine. Accordingly, at least some known conduits are subjected to differential thermal movement and vibratory excitation during gas turbine engine operation.  
         [0004]     For example, at least one known fluid carrying joint used in the bleed air system, includes ball and socket joints which allow relative pivotal movement, with the joints also being configured to accommodate differential translation between adjacent ends of the conduits. However, at least one known ball joint may cause undesirable leakage in view of the various differential pivotal and translation movements to which the joint is subjected to during operation, as well as due to vibratory excitation. More specifically, as the ball joints wear during operation, leakage therefrom becomes an increasing problem until the traditional ball joints require replacement at a relatively substantial cost.  
         [0005]     Additionally, at least one known gas turbine engine includes a type of flex joint commonly referred to as a non-metallic seal. Non-metallic seals typically include an elastomeric seal that facilitates preventing leakage of the fluid contained within the ducting system while still allowing flexibility in the flex joint. However, during use, the non-metallic seals may become brittle causing them to leak at higher temperatures. Moreover, at least one known non-metallic seal includes an outrigger that is configured to secure the non-metallic seal to the piping components. Accordingly, known non-metallic seals operate in compression and include a plurality of external components to secure the outrigger to the piping components, thus increasing the costs of the non-metallic seal. Moreover, since known seals include a plurality of external components, assembling a known seal is relatively time consuming, thus further increasing the cost of the seal.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0006]     In one aspect, a method for assembling an expansion joint is provided. The method includes providing a first seal retainer, positioning an annular first seal at least partially within the first seal retainer such that the first seal extends between the first seal retainer first and second ends and substantially fills the first seal retainer cavity, providing a second seal retainer, positioning an annular second seal at least partially within the second seal retainer such that the second seal extends between the second seal retainer first and second ends and substantially fills the second seal retainer cavity, coupling a bellows to the first and second seal retainers, and slidably coupling a unitary annular shroud the first and second seal retainers such that the shroud substantially circumscribes the first and second seal retainers, and such that the bellows is between the annular shroud and the first and second seal retainers.  
         [0007]     In another aspect, an expansion joint is provided. The expansion joint includes an annular first seal retainer having a cavity that is defined between a first end and a second end, an annular first seal positioned at least partially within the first seal retainer such that the first seal substantially fills the first seal retainer cavity, the first seal extends between the first seal retainer first and second ends, an annular second seal retainer having a cavity that is defined between a first end and a second end, an annular second seal positioned at least partially within the second seal retainer such that the second seal substantially fills the second seal retainer cavity, the second seal extends between the second seal retainer first and second ends, a bellows coupled to the first and second seal retainers, and a unitary annular shroud circumscribing, and slidably coupled to, the first and second seal retainers, the bellows between the annular shroud and the first and second seal retainers.  
         [0008]     In a further aspect, a gas turbine engine is provided. The gas turbine engine includes a compressor, a turbine, and a bleed air system configured to channeled compressed air from the compressor to the turbine. The bleed air system includes an expansion joint including an annular first seal retainer having a cavity that is defined between a first end and a second end, an annular first seal positioned at least partially within the first seal retainer such that the first seal substantially fills the first seal retainer cavity, the first seal extends between the first seal retainer first and second ends, an annular second seal retainer having a cavity that is defined between a first end and a second end, an annular second seal positioned at least partially within the second seal retainer such that the second seal substantially fills the second seal retainer cavity, the second seal extends between the second seal retainer first and second ends, a bellows coupled to the first and second seal retainers, and a unitary annular shroud circumscribing, and slidably coupled to, the first and second seal retainers, the bellows between the annular shroud and the first and second seal retainers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exemplary aircraft turbofan gas turbine engine having a bleed air system channeling a portion of compressed air to an annular manifold surrounding a low pressure turbine for cooling thereof;  
         [0010]      FIG. 2  is a radial view of an exemplary articulated air manifold surrounding the low pressure turbine illustrated in  FIG. 1  and taken generally along line  2 - 2 , and includes a plurality of exemplary expansion joints;  
         [0011]      FIG. 3  is an elevational, sectional view of an exemplary embodiment of one of the expansion joints illustrated in  FIG. 2  and taken generally along line  3 - 3 ; and  
         [0012]      FIG. 4  is a perspective, partly cut away view of the exemplary expansion joint illustrated in  FIGS. 2 and 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  is an axial, partly sectional view of an exemplary aircraft turbofan gas turbine engine  10 . Gas turbine engine  10  includes in serial flow communication a fan  12 , a low pressure compressor  14 , a high pressure compressor  16 , a combustor  18 , a high pressure turbine  20 , and a low pressure turbine  22 .  
         [0014]     High pressure turbine  20  is coupled to high pressure compressor  16  with a first rotor shaft  40 , and low pressure turbine  22  is coupled to low pressure compressor  14  with a second rotor shaft  42 . Rotor shafts  40  and  42  are each substantially coaxially aligned with respect to a longitudinal centerline axis  43  of gas turbine engine  10 .  
         [0015]     In operation, ambient air  46 , drawn into low pressure compressor  14 , is compressed and channeled downstream to high pressure compressor  16 . High pressure compressor  16  further compresses the air and delivers high pressure air to combustor  18  where it is mixed with fuel, and the mixture is ignited to generate high temperature combustion gases. The combustion gases are channeled from combustor  18  to drive turbines  20  and  22 .  
         [0016]     In the exemplary embodiment, selected components of low pressure turbine  22  are cooled utilizing compressed air that is channeled from a suitable stage of high pressure compressor  16  through a bleed air system  50 . In the exemplary embodiment, bleed air system  50  includes an annular, multi-component air manifold  52  which receives cooling air  54  and suitably disperses cooling air  54  to the various components within the low pressure turbine  22 .  
         [0017]      FIG. 2  illustrates an exemplary embodiment of manifold  52  surrounding low pressure turbine  22  shown in phantom. Cooling air  54  is suitably channeled into the manifold  52  through a plurality of inlets  56  thereof. Cooling air  54  is then discharged from the manifold  52  into low pressure turbine  22  through a plurality of outlets  58  in the form of radially inwardly extending and axially inclined tubes. In the exemplary embodiment, cooling air  54  is distributed circumferentially around manifold  52  through interconnected fluid carrying conduits indicated generally at  60 . In the exemplary embodiment, a plurality of expansion joints  100  are circumferentially spaced apart around the circumference of manifold  52  between adjacent outlets  58  to accommodate differential thermal movement due to expansion and contraction during operation. In an alternative embodiment, expansion joints  100  are located in each of manifold outlet  58 , one of which is illustrated in phantom at the 12:00 position in  FIG. 2 .  
         [0018]      FIG. 3  illustrates an exemplary expansion joint  100  wherein the interconnected conduits  60  include at least a first conduit  102  which enters expansion joint  100  from a first side  104 , and a second conduit  112  which enters expansion joint  100  from a second side  114 , that is opposite first side  104 . In the exemplary embodiment, expansion joint  100  carries therethrough and between conduits  60  the cooling air  54 . A cutaway perspective view of expansion joint  100  is illustrated in  FIG. 4 .  
         [0019]     In the exemplary embodiment, expansion joint  100  includes a first annular seal retainer  120 , a second annular seal retainer  122 , and an annular bellows assembly  124  that is connected to first and second seal retainers  120  and  122 , respectively. More specifically, first and second seal retainers  120  and  122  each include a first portion  130  and a second portion  132  that is coupled to first portion  130  using a welding procedure, for example. In the exemplary embodiment, first portion  130  has a substantially L-shaped cross-sectional profile such that when second portion  132  is coupled to first portion  130 , each respective seal retainer  120  and  122 , have a substantially U-shaped cross-sectional profile.  
         [0020]     Accordingly, and in the exemplary embodiment, first and second portions  130  and  132  define an annular cavity  140  and an annular cavity  141  respectively, therein that is configured to retain at least one seal. More specifically, seal retainers  120  and  122  each include at least one annular seal  142  and  143 , respectively, that are inserted at least partially therein. In the exemplary embodiment, each respective seal  142  and  143  is positioned at least partially within each respective seal retainer  120  and  122 , such that each respective seal  142  and  143  substantially fills seal retainer cavities  140  and  141 , and such that seal  142  extends between a seal retainer first end  144  and a seal retainer second end  145 , and such that seal  143  extends between a seal retainer first end  146  and a seal retainer second end  147 . In the exemplary embodiment, seals  142  and  143  are fabricated from a graphite material. In an alternative embodiment, seals  142  and  143  is fabricated from a material other than graphite.  
         [0021]     In the exemplary embodiment, each seal  142  and  143  includes a first seal portion  150  and a second seal portion  152  that is positioned adjacent first seal portion  150 . In an alternative embodiment, each seal  142  and  143  includes a single seal portion such that first and second seal portions  150  and  152  are unitarily formed together to form unitary a seal  142  and  143 , respectively. Each seal  142  and  143  includes a radially outer surface  160  and a radially inner surface  162 . In the exemplary embodiment, radially outer surface  160  is substantially planar, and radially inner surface  162  is substantially concave.  
         [0022]     Bellows assembly  124  includes a first portion  170 , a second portion  172 , and a bellows  174  that is coupled between first and second portions  170  and  172 , respectively. In the exemplary embodiment, first portion  170  is coupled to an exterior surface  176  of seal retainer  120 , and second portion  172  is coupled to an exterior surface  178  of seal retainer  122 , using a welding procedure for example.  
         [0023]     Expansion joint  100  also includes an annular outer shroud  180  that is configured to circumscribe at least a portion of seal retainers  120  and  122 , respectively, and bellows assembly  124 . In the exemplary embodiment, outer shroud  180  includes a first portion  182 , a second portion  184  that is coupled to first portion  182 , and a third portion  186  that is coupled to second portion  184 . In the exemplary embodiment, second portion  184  substantially circumscribes bellows  174 . In the exemplary embodiment, expansion joint  100  also includes a substantially L-shaped retainer  190  that is positioned between outer shroud  180  and exterior surface  176  of seal retainer  120  to facilitate securing at least one end of bellows  174  in a substantially fixed position. More specifically, retainer  190  facilitates bellows first portion  170  in a substantially fixed position. In an alternative embodiment, expansion joint  100  does not include retainer  190 .  
         [0024]     During assembly, and in the exemplary embodiment, a first substantially tubular fitting  200  having at a proximal end thereof has a cylindrical first sleeve  202  for being fixedly joined to the end of a first conduit  204  using a welding or brazing procedure, for example. Disposed at an opposite, distal end of the first fitting  200  is a first ball  206  which includes a substantially spherical section having a substantially convex annular outer surface  208  such that a sealing contact is created between outer surface  208  and  162  seal inner surface  162 . Similarly, a substantially identical tubular second fitting  210  includes at a proximal end thereof a cylindrical second sleeve  212  which is fixedly joined to a corresponding end of a second conduit  214 . Second fitting  210  includes a second ball  216  at its distal end which is also a truncated spherical section having a convex annular outer surface  218  such that a sealing contact is created between outer surface  218  and seal inner surface  162 .  
         [0025]     In the exemplary embodiment, bellows assembly  124  is coupled to seal retainers  120  and  122 , respectively. A respective seal  142  is then at least partially inserted into each respective annular cavity  140  formed by each respective seal retainer  120  and  122 , respectively. First sleeve  202  is then positioned radially inward of first seal retainer  120  such that a seal is formed between seal inner surface  162  and sleeve outer surface  208 . More specifically, first seal portion  150  is inserted into first seal retainer first portion  130 , first sleeve  202  is then inserted radially inward of first seal retainer first portion  130 . Second seal portion  152  is then inserted between first sleeve retainer first portion  130  and first sleeve  202 . First seal retainer second portion  132  is then coupled to first seal retainer first portion  130  to facilitate securing first sleeve  202  in a substantially fixed position within seal retainer  120 .  
         [0026]     Second sleeve  212  is then positioned radially inward of second seal retainer  122  such that a seal is formed between seal inner surface  162  and sleeve outer surface  216 . More specifically, second seal portion  150  is inserted into second seal retainer first portion  130 , second sleeve  212  is then inserted radially inward of second seal retainer first portion  130 . Second seal portion  152  is then inserted between second seal retainer first portion  130  and second sleeve  212 . Second seal retainer second portion  132  is then coupled to second seal retainer first portion  130  to facilitate securing second sleeve  212  in a substantially fixed position within seal retainer  122 .  
         [0027]     Outer shroud  180  is then coupled to first and second seal retainers  120  and  122 , respectively. More specifically, outer shroud second portion  184  is coupled circumferentially around first and second seal retainers  120  and  122  such that outer shroud second portion  184  substantially circumscribes first and second seal retainers  120  and  122 . Outer shroud first and third portions  182  and  186  are then coupled to outer shroud second portion  184  to facilitate maintaining first and second seal retainers  120  and  122 , and bellows assembly  124  substantially within outer shroud assembly  180 .  
         [0028]     In the exemplary embodiment, first conduit  204  is then coupled to first sleeve  202 , and second conduit  214  is coupled to second sleeve  212  such that airflow  54  can be channeled from a suitable stage of high pressure compressor  16  through a bleed air system  50 , through manifold  52 , to the various components within the low pressure turbine  22  as described previously herein.  
         [0029]     The expansion joint described herein includes at least two graphite seals to allow the expansion joint to be utilized within a plurality of relatively high temperature applications equal to or greater than those of expansion joints currently used in various aerospace applications. Additionally, the expansion joint described herein includes a bellows to apply a force on the structure, i.e. each conduit, to assure a good seal. For example, during operation, as the pressure within the expansion joint increases, the force applied by the bellows to the seals increases to improve the sealing at the higher pressure. Moreover, the expansion joint described herein does not require additional ancillary brackets or external rigging, thus reducing the associated weight, space and cost, of the expansion joint. Moreover, since the expansion joint described herein does not require additional ancillary brackets or external rigging, assembling a known seal is relatively time consuming, thus further increasing the cost of the seal.  
         [0030]     Accordingly, the expansion joint described herein is a self contained, light weight flex joint capable of withstanding very high temperatures such as those currently needed in current aerospace applications.  
         [0031]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.