Abstract:
A seal for a duct having an upstream portion and a downstream portion, the duct upstream portion and the duct downstream portion separated by a first gap, includes a first portion having a length greater than a width of the first gap between the first portion and the second portion, the first portion having a first thickness, a first upstream end and a first downstream end; a second portion having a length greater than a width of the gap between the first portion and the second portion, the second portion having a second thickness, a second upstream end and a second downstream end; and an attachment between the first portion and the second portion such that the first portion and the second portion move relative to each other, wherein the first portion is inside the duct and the second portion is outside of the duct.

Description:
BACKGROUND 
     Operating temperatures of gasses in and passing from combustors of gas turbine engines are typically quite high, requiring cooled liners in the combustors and downstream thereof to avoid damage to the internal parts of the engines. Cooling is typically provided by a compressor upstream of the combustor. To maximize engine efficiency, it is desirable to use the minimal amount of cooling air necessary to maintain the integrity of the liners and not to allow any cooling air leakage. 
     Leakage may occur between mating or adjacent components and seals. Tight tolerances between such mating or adjacent components are typically employed to minimize such leakage. 
     SUMMARY OF THE INVENTION 
     According to a non-limiting embodiment disclosed herein, a seal for a duct having an upstream portion and a downstream portion, the duct upstream portion and the duct downstream portion separated by a first gap, includes a first portion having a length greater than a width of the first gap between the first portion and the second portion, the first portion having a first thickness, a first upstream end and a first downstream end; a second portion having a length greater than a width of the gap between the first portion and the second portion, the second portion having a second thickness, a second upstream end and a second downstream end; and an attachment between the first portion and the second portion such that the first portion and the second portion move relative to each other wherein the first portion is inside the duct and the second portion is outside of the duct. 
     According to any previous claim, a second gap is disposed between the first upstream portion and the second upstream portion wherein the second gap is smaller than a thickness of the duct upstream portion. 
     According to any previous claim, a third gap is disposed between the first downstream portion and the second downstream portion wherein the third gap is smaller than a thickness of the duct upstream portion. 
     According to any previous claim, a third gap is disposed between the first downstream portion and the second downstream portion wherein the third gap is smaller than a thickness of the duct upstream portion. 
     According to any previous claim, the first thickness is thicker than the second thickness. 
     According to any previous claim, the second thickness is thinner than the first thickness. 
     According to any previous claim, the second thickness is thinner than the first thickness and is disposed in a higher pressure environment than a lower pressure environment in which the first thickness is disposed. 
     According to any previous claim, each of the upstream ends and the downstream ends have rotation points that rotate the first portion and the second portion about the duct upstream portion and the duct downstream portion. 
     According to any previous claim, one of the first portion and the second portion are disposed radially inwardly within the duct, the one of the first portion and the second portion having an extension extending distally beyond the a rotation point on either of the upstream end or the downstream end. 
     According to any previous claim, the first portion and the second portion are spring loaded against the duct upstream portion and the duct downstream portion. 
     According to any previous claim, the attachment includes a first finger extending from the first portion towards the second portion, a second finger extending from the second portion towards the first portion, and an axle extending through the first finger and the second finger about which the first and second finger may rotate. 
     According to any previous claim, the second portion is segmented into first members to maintain a seal if the duct is curved wherein two adjacent members are defined by a cleft. 
     According to any previous claim, the cleft is covered by a band attaching to one of the adjacent first members and is forced against another of the adjacent first members by pressure. 
     According to any previous claim, wherein the first portion is segmented into second members to maintain a seal if the duct is curved. 
     According to any previous claim, wherein each the first portion and the second portion are arcuate, and a concave side of the first portion faces a concave side of the second portion. 
     According to a further non-limiting embodiment disclosed herein, a seal for sealing a first gap between a higher temperature, lower pressure first flow path and a lower temperature higher pressure second flow path in a gas turbine engine, the seal includes a first portion having a length greater than a width of the first gap, the first length disposed in the higher temperature, lower pressure first flow, the first portion having a first thickness, a first upstream end and a first downstream end; a second portion having a length greater than a width of the gap the second portion disposed in the higher pressure, lower temperature second flow, the second portion having a second thickness, a first upstream end and a first downstream end; and an attachment between the first portion and the second portion such that the first portion and the second portion move relative to each other. 
     According to any previous claim, wherein the first thickness is thicker than the second thickness. 
     According to any previous claim, wherein each of the upstream ends and the downstream ends have rotation points for rotating the first portion and the second portion about a first edge or a second edge, wherein the gap is formed between the first edge and the second edge. 
     According to any previous claim, the first portion and the second portion are spring loaded against the first edge and the second edge. 
     According to any previous claim, wherein the attachment includes a first finger extending from the first portion towards the second portion, a second finger extending from the second portion towards the first portion, and an axle extending through the first finger and the second finger about which the first and second finger rotate. 
     According to any previous claim, wherein each the first portion and the second portion are arcuate, and a concave side of the first portion faces a concave side of the second portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
         FIG. 1  is a sectional view of a gas turbine engine that incorporates an exemplary embodiment disclosed herein. 
         FIG. 2  is a side-view of a seal used between adjacent ducts taken along the lines  2 - 2  of  FIG. 1 . 
         FIG. 2A  is a side-view of the seal taken along the lines  2 - 2  of  FIG. 2 . 
         FIG. 3  is a perspective side-view of a first embodiment of the seal of  FIG. 2 . 
         FIG. 4  is a perspective inner view of a segmented seal of  FIG. 2 . 
         FIG. 4A  is a perspective outer view of a segmented seal of  FIG. 2   
         FIG. 5  is a side-view of the seal of  FIG. 2  in operation. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a gas turbine engine  10  includes a fan section  12 , a compressor section  14 , a combustor section  16 , and a turbine section  18 . Air entering into the fan section  12  is initially compressed and a portion fed to the compressor section  14 . Bypass air flow  301  provides some of the propulsion force from the engine. In the compressor section  14 , the incoming air from the fan section  12  is further compressed and communicated to the combustor section  16 . In the combustor section  16 , the compressed air is mixed with gas and ignited to generate a hot exhaust stream  28 . The hot exhaust stream  28  is expanded across the turbine section  18  to drive the fan section  12  and the compressor section  14 . In this example, the gas turbine engine  10  includes an augmenter section  20  where additional fuel can be mixed with the exhaust gasses  28  and ignited to generate additional thrust. The exhaust gasses  28  flow from the turbine section  18  and the augmenter section  20  through an exhaust duct  22 . Some bypass air  302  passes within the duct  22  as cooling air. An inner liner for the exhaust duct  22  protects outer surface  82  from the hot gasses  28  escaping from the augmentor section  20  and the turbine section  18 . Of course, this application extends to engines without an augmentor section. 
     As one may appreciate, there may be several liners in the engine  10 . Liner  55  is in the exhaust duct  22 . Liner  60  is in the augmentor section  20  and liner  65  is in the turbine section  18 . The liners  55 ,  60  and  65 , however, may be in more than one piece and are constructed generally of axial segments. For instance, duct liner  55  may have an upstream segment  75  and a downstream segment  80  (See  FIG. 2 ). 
     Referring now to  FIGS. 2-4 , the liner  55  has an upstream segment  75  and a downstream segment  80  separated by a gap  77 . Each of the upstream and downstream segments  75  and  80  has a radially inner chamfer  85  and a radially outer chamfer  90  and an edge formed therebetween  95 . A seal  100  bridges the gap between the upstream segment  75  and the downstream segment  80 . The seal  100  is shaped like a clamshell and has a radially inner half  105 , a radially outer half  110  that are both disposed radially outward from an axial centerline  115 . 
     The radial inner half  105  has an arcuate body  130  and radially outwardly extending fingers  135  which extend from a central area  140  of the arcuate body  130 . The arcuate body  130  is thicker than the body of the radially outer half  110  as will be discussed infra. Each finger  135  has an opening  145  near a remote end  150  thereof. Each of the fingers is separated by a distance D 1 , as will be discussed infra. The arcuate body  130  may have one or more vents  155  to prevent any pressure buildup between the radial inner half  105  and the radial outer half  110 . The arcuate body  130  has an upstream end  160  and a downstream end  165 . 
     Referring to  FIG. 2A , each of the upstream end  160  and the downstream end  165  has a flat portion  170  that is offset from each of the streamed portion and the downstream portions  75  and  80  by an arcuate bump  175  that comes into contact with the upstream portion and the downstream portion (see  FIG. 2A ). A gap  180  is formed between the flat portion and the liner to allow relative motion of the seal  100  about the upstream segment  75  and a downstream segment  80 . 
     The radial outer half  110  has an arcuate body  185  with radially inwardly extending fingers  190 , each of which extends outwardly from the central area  195  of the arcuate body  185 . Each finger has an h  200  near a finger remote end  205  and each of the fingers is also separated by a distance D 1 . The fingers  190  of the radial outer half mesh with the fingers  135  of the radial inner half to receive a pin  210  in the holes  200  in the radially outer half and the openings  145  and the fingers  135  of the radial inner half  105 . The pin  210  locks the radial outer half  110  to the radial inner half  105 . The arcuate bodies  130  and  185  are convex sides  187  facing each other. 
     The radial outer half  110  has an upstream end  215  and a downstream end  220 . Each of the upstream end and the downstream end have an arcuate bump  230  extending from the upstream end  215  and the downstream end  220  that comes in contact with each of the upstream liners  75  and the downstream segment  80  to relative motion of the seal  100  about the upstream segment  75  and a downstream segment  80 . 
     The arcuate body of the radial outer half  110  is thinner than the body  130 . The thinness promotes cooling of the radial outer half arcuate body  185 , while the thicker arcuate body  130  of the radial inner half  105  helps protect it from heat. Moreover, the radial outer half arcuate body  185  can be springier and thinner to enable the secondary flow  37  press the arcuate bumps  230  against the upstream segment  75  and the downstream segment  80  to provide primary sealing thereby. The secondary flow  37  is higher pressure and cooler than the hot exhaust stream  28  of gas. 
     In operation, the edges  95  and the radially inner chamfer and the radially outer chamfer  85 ,  90 , enable the upstream ends  160  and  215  to be separated by the chamfer surfaces and allow the seal  100  to be slid across the upstream segment  75 . Similarly, the downstream segment  80  may be inserted through the arcuate bump  230  and the arcuate bump  175  of the radial inner half  105  and the radial outer half  110 . Alternatively, the radial inner half  105  and the radial outer half  110  may be placed against the upstream segment  75  and the downstream segment  80  and then compressed while the pin  210  is snaked through the openings  145 . 
     Because the normal spacing between the upstream ends  160 ,  215  of the radial inner half  105  and the radial outer half  110  is less than the thickness of the upstream segment  75  and the downstream segment  80 , the seal  100  becomes spring loaded against the upstream segment  75  and the downstream segment  80 . Pressure from the secondary flow  37  pushes the radial outer half  110  and the contact bumps  230  against the radial upstream segment  75  and the downstream segment  80 , thereby providing the primary seal. The vents  155  minimize the probability that air will leak under the gap  180  and the arcuate bumps  175  to allow the air to pressurize the area  255  between the radial inner half  105  and the radial outer half  110  so that neither of the radial inner half or the radial outer half  110  are lifted away from the upstream segment  75  or the downstream segment  80 . Because the radial inner half  105  and the radial outer half  110  are free to rotate about the pin  235 , the parts may rotate about the pin to allow relative motion between the seal  100  and the upstream segment  75  and the downstream segment  80  (see  FIG. 5 ). However, motion between the seal  100  and the upstream segment  75  and a downstream segment  80  may be limited if the gap  180  is closed and the downstream end  165  contacts either the upstream segment  75  or the downstream segment  80 . 
     Referring now to  FIGS. 4 and 4   a , because many ducts and liners  55  have contoured shapes, the seal  100  must be able to conform to the contoured shapes. In this instance the liner  55  is annularly shaped. In order for the seal  100  to seal the gap  77 , the radial outer half  110  may be made of radial outer members  250  separated by narrow slots or kerfs  255 . A band  260  covers each slot  255 . The band  260  may be glued on one member  255  and forced against an adjacent member  255  by the secondary flow  37  to seal each slot  255  from air leakage therethrough thereby maintaining the seal. 
     In order for the seal  100  to seal the gap  77 , the radial outer half  110  may be made of a plurality of abutting radial outer members  250  that may be separated by narrow clefts  255 . A band  260  covers each cleft  255 . The band  260  may be glued on one radial outer member  255  and forced against an adjacent radial outer member  255  by the secondary flow  37  to seal each cleft  255  from air leakage therethrough thereby maintaining the seal. Because the seal  100  is segmented by the radial outer members  255 , the radial outer members  250  have enough bend about the clefts  255  to maintain a shape of the liner  55  while maintaining a seal. 
     Similarly, the radial inner half  105  may be made of a plurality of abutting radial inner members  270  that may be separated by narrow clefts  275 . Because the seal  100  is segmented by the radial inner members  275 , the radial inner members have enough flexibility to maintain a curve of the liner  55  while maintaining a seal. Because the radial inner half  105  experiences the lower pressure provided by the hot exhaust stream  28 , it is not necessary to provide band  260  on the radial inner half  105  which may also have clefts  280  about which the radial inner members may rotate to maintain a curve of the liner  55 . 
     Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.