Abstract:
A method for assembling a gas turbine engine is provided. The method comprises coupling a first turbine nozzle within the engine, coupling a second turbine nozzle circumferentially adjacent the first turbine nozzle such that a gap is defined between the first and second turbine nozzles and providing at least one spline seal including a substantially planar body. The method also comprises forming at least one retainer tab to extend outward from the body portion of the at least one spline seal, and inserting the at least one spline seal into a slot defined in at least one of the first and second turbine nozzles to facilitate reducing leakage through said gap, such that the at least one retainer tab facilitates retaining the retainer tab within the turbine nozzle slot.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to turbine engines and more particularly, to methods and apparatus for assembling gas turbine engines.  
         [0002]     Known gas turbine engines include combustors which ignite fuel-air mixtures which are then channeled through a turbine nozzle assembly towards a turbine. At least some known turbine nozzle assemblies include a plurality of arcuate nozzle segments arranged circumferentially. At least some known turbine nozzles include a plurality of circumferentially-spaced hollow airfoil vanes coupled by integrally-formed inner and outer band platforms. More specifically, the inner band forms a portion of the radially inner flowpath boundary and the outer band forms a portion of the radially outer flowpath boundary.  
         [0003]     Within known turbine nozzle assemblies, the turbine nozzle segments are coupled circumferentially within the turbine engine. More specifically, because of temperature differentials that may develop and to accommodate thermal expansion, known turbine nozzles are positioned such that a gap or clearance is defined between pairs of circumferentially-adjacent nozzles. To facilitate preventing cooling air supplied to such nozzle segments from leaking through the clearance gaps, at least some known turbine nozzle assemblies include a plurality of spline seals.  
         [0004]     Known spline seals are substantially flat pieces of material that are inserted within slots defined in the turbine nozzles. More specifically, at least some known nozzle assemblies include a loading slot that facilitates the installation of the spline seals within the spline seal slots. However, depending on the operation of the turbine engine, at least some known spline seals may undesirably slip out of the spline seal slots through the loading slot. Such seals may be channeled downstream and cause damage to other engine components. Moreover, over time, continued operation with decreased cooling of the turbine nozzles adjacent such spline seal slots may limit a useful life of the turbine nozzle.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In one aspect, a method for assembling a gas turbine engine is provided. The method comprises coupling a first turbine nozzle within the engine, coupling a second turbine nozzle circumferentially adjacent the first turbine nozzle such that a gap is defined between the first and second turbine nozzles and providing at least one spline seal including a substantially planar body. The method also comprises forming at least one retainer tab to extend outward from the body portion of the at least one spline seal, and inserting the at least one spline seal into a slot defined in at least one of the first and second turbine nozzles to facilitate reducing leakage through said gap, such that the at least one retainer tab facilitates retaining the retainer tab within the turbine nozzle slot.  
         [0006]     In another aspect, a seal assembly for use with a turbine engine turbine nozzle assembly is provided. The seal assembly includes at least one spline seal sized for insertion within a slot formed within a turbine nozzle. The at least one spline seal is configured to facilitate reducing leakage through the turbine engine turbine nozzle assembly, and includes a substantially planar body and at least one tab extending outward from said body. The seal body is bounded by an outer periphery, and the at least one tab is adjacent to the body outer periphery.  
         [0007]     In a further aspect, a turbine nozzle assembly for a gas turbine engine is provided. The nozzle assembly includes a plurality of turbine nozzles and a seal assembly. Each turbine nozzle includes an outer band, an inner band, and at least one airfoil vane extending between the outer and inner bands. A portion of each of the plurality of turbine nozzles defines a slot therein. The seal assembly includes at least one spline seal sized for insertion within the turbine nozzle slot to facilitate reducing leakage between circumferentially adjacent pairs of the turbine nozzles. The at least one spline seal includes a substantially planar body and at least one retainer tab extending outward from the body. The body is bounded by an outer periphery, and the at least one retainer tab is adjacent to the body outer periphery. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine;  
         [0009]      FIG. 2  is a side view of an exemplary turbine nozzle that may be used with the gas turbine engine shown in  FIG. 1 ;  
         [0010]      FIG. 3  is a perspective view of an exemplary spline seal that may be used with the turbine nozzle shown in  FIG. 2 ;  
         [0011]      FIG. 4  is a perspective view of an alternative embodiment of the spline seal shown in  FIG. 3 ;  
         [0012]      FIG. 5  is perspective view of a further alternative embodiment of the spline seal shown in  FIG. 3 ; and  
         [0013]      FIG. 6  is a perspective view of another alternative embodiment of the spline seal shown in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine  10  including a low pressure compressor  12 , a high pressure compressor  14 , and a combustor  16 . Engine  10  also includes a high pressure turbine  18  and a low pressure turbine  20 . Compressor  12  and turbine  20  are coupled by a first shaft  21 , and compressor  14  and turbine  18  are coupled by a second shaft  22 . In one embodiment, gas turbine engine  10  is an LM2500 engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio. In another embodiment, gas turbine engine  10  is a CFM engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio.  
         [0015]     In operation, air flows through low pressure compressor  12  supplying compressed air from low pressure compressor  12  to high pressure compressor  14 . The highly compressed air is delivered to combustor  16 . Airflow from combustor  16  is channeled through a turbine nozzle (not shown in  FIG. 1 ) to drive turbines  18  and  20 , prior to exiting gas turbine engine  10  through an exhaust nozzle  24 .  
         [0016]      FIG. 2  is a side view of an exemplary turbine nozzle  50  that may be used with a gas turbine engine, such as turbine engine  10  (shown in  FIG. 1 ). In the exemplary embodiment, nozzle  50  is one segment of a plurality of segments that are positioned circumferentially to form a nozzle assembly (not shown) within the gas turbine engine. Nozzle  50  includes at least one airfoil vane  52  extending between an arcuate radially outer band or platform  54 , and an arcuate radially inner band or platform (not shown). More specifically, in the exemplary embodiment, outer band  54  and the inner band are each integrally-formed with airfoil vane  52 .  
         [0017]     In the exemplary embodiment, nozzle  50  also includes an axial spline seal slot  60  and a radial spline seal slot  62  that are each formed in a generally axially-extending face  64  of nozzle  50 . More specifically, slot  60  extends generally axially through a portion of face  64  and slot  62  extends generally radially through a radial flange  66  portion of nozzle  50 . In the exemplary embodiment, slot  60  is also formed integrally with a loading slot portion  68  that facilitates the installation of axial spline seals (not shown in  FIG. 2 ) into the segmented nozzle assembly.  
         [0018]     A thickness T of spline seal slot  60  is substantially constant through slot  60 . In the exemplary embodiment, loading slot portion  68  is frusto-conical such that a thickness T LS  of slot portion  68  increases from slot  60  to a stop projection  72  adjacent a trailing end  76  of slot portion  68 . Stop projection  72  facilitates maintaining the spline seal within slot  60 .  
         [0019]     During assembly of the nozzle assembly, a plurality of nozzles  50  are positioned circumferentially adjacent to each other to form the nozzle assembly. Specifically, nozzles  50  are positioned relative to each other such that a clearance gap is defined between each pair of circumferentially adjacent pairs of nozzles. More specifically, the clearance gap is defined between circumferentially adjacent and opposing nozzle end faces  64 . To facilitate sealing the clearance gaps, spline seals (not shown in  FIG. 2 ) are inserted within a pair of circumferentially adjacent spline seal slots  60 . More specifically, when positioned within slots  60 , each spline seal circumferentially bridges the clearance gap to facilitate preventing leakage through the gap.  
         [0020]      FIG. 3  is a perspective view of an exemplary spline seal  100  that may be used in turbine nozzle  50  (shown in  FIG. 2 ). In the exemplary embodiment, spline seal  100  is substantially rectangular and is bordered by an outer perimeter  102  including a pair of circumferentially-spaced sides  104  that are connected by a leading edge side  106  and a trailing edge side  108 . Alternatively, spline seal  100  may have any non-rectangular shape that enables seal  100  to function as described herein. Accordingly, in the exemplary embodiment, at least one corner portion  114  is defined at the intersection of sides  104  and  106  or sides  104  and  108 .  
         [0021]     Spline seal  100  includes a body portion  120  and a retainer tab  122 . Body portion  120  is substantially planar and includes a radially outer surface  124  and an opposite radially inner surface  126 . Body portion  120  is sized for insertion within spline seal slot  60  and has a thickness T B  that is thinner than spline seal slot thickness T. In one embodiment, spline seal  100  is fabricated from a substantially flat piece of sheet metal.  
         [0022]     Retainer tab  122  extends outward from body portion  120  and is not co-planar with body portion  120 . Specifically, in the exemplary embodiment, retainer tab  122  extends outward from spline seal outer perimeter  102 , and more specifically, is formed within a spline seal corner portion  114 . Accordingly, in the exemplary embodiment, retainer tab  122  is substantially triangular shaped. Alternatively, retainer tab  122  may extend from any portion of body portion  120 , or have any shape, that enables retainer tab  122  to function as described herein. Moreover, although only one retainer tab  122  is illustrated, spline seal  100  may include any number of retainer tabs  122 . In the exemplary embodiment, retainer tab  122  is oriented at an oblique angle θ with respect to body radially outer surface  124 . Alternatively, retainer tab  122  may be oriented at any angle θ with respect to radially outer surface  124  that enables retainer tab  122  to function as described herein. In another alternative embodiment, retainer tab  122  may be oriented at any angle θ with respect to body radially inner surface  126  such that retainer tab  122  extends radially inward from surface  126  rather than outward from surface  124 .  
         [0023]     In the exemplary embodiment, retainer tab  122  is formed integrally with body portion  120 . More specifically, in the exemplary embodiment, retainer tab  122  is formed by bending a portion of spline seal  122  to a desired angle θ. Alternatively, retainer tab  122  may be coupled to body portion  120 .  
         [0024]     During assembly, spline seal  100  is inserted through loading slot portion  68  and into spline seal slot  60  such that spline seal  100  circumferentially bridges the clearance gap between adjacent nozzles  50  (shown in  FIG. 2 ). More specifically, spline seal  100  is inserted into slot  60  such that seal leading edge side  106  is upstream from seal trailing edge side  108 . As such, in the exemplary embodiment, when spline seal  100  is fully inserted into slot  60 , retainer tab  122  extends outward from spline seal body portion  120  and contacts a radially upper surface  130  (shown in  FIG. 2 ) of slot portion  68 , which limits the amount of radial movement of trailing edge side  108 . Moreover, because the radial movement of spline seal side  108  is limited, spline seal trailing edge side  108  is facilitated to be maintained in contact with, or in position to contact, stop projection  72 . As such, during engine operation, retainer tab  122  facilitates maintaining spline seal  100  within spline seal slot  60 , and thus facilitates preventing spline seal  100  from undesirably slipping or backing out from slot  60 . As a result, retainer tab  122  facilitates minimizing leakage through the segmented turbine nozzle assembly clearance gaps and thus facilitates enhancing engine performance and component life expectancy.  
         [0025]      FIG. 4  is a perspective view of an alternative embodiment of spline seal  100 . The embodiment illustrated in  FIG. 4  is substantially similar to the embodiment illustrated in  FIG. 3  and components of spline seal  100  illustrated in  FIG. 4  that are identical to components of spline seal  100  illustrated in  FIG. 3 , are identified in  FIG. 4  using the same reference numerals used in  FIG. 3 . Accordingly, spline seal  100  includes a retainer tab  150  that extends outward from body portion  120  and as such, is not co-planar with body portion  120 . Specifically, in the exemplary embodiment, retainer tab  122  has a width W that is identical to a width Ws of spline seal  100  measured between sides  104 . Accordingly, in the exemplary embodiment, retainer tab  122  is substantially rectangular-shaped. Alternatively, retainer tab  150  may extend from any portion of body portion  120 , or have any shape, that enables retainer tab  150  to function as described herein. In the exemplary embodiment, retainer tab  150  is oriented at an oblique angle β with respect to body radially inner surface  126 . Alternatively, retainer tab  150  may be oriented at any angle β with respect to radially inner surface  126  that enables retainer tab  150  to function as described herein.  
         [0026]     In the exemplary embodiment, retainer tab  150  is formed integrally with body portion  120 . More specifically, in the exemplary embodiment, retainer tab  150  is formed by bending a portion of spline seal  100  to a desired angle β. Alternatively, retainer tab  150  may be coupled to body portion  120 .  
         [0027]     During engine operation, when spline seal  100  is fully inserted into slot  60 , because retainer tab  150  extends outward from spline seal body portion  120 , retainer tab  150  facilitates limiting an amount of radial and axial movement of spline seal  100 . More specifically, as spline seal  100  travels afterward towards loading slot portion  68 , retainer tab  150  contacts stop projection  72 . As such, during engine operation, retainer tab  150  facilitates maintaining spline seal  100  within spline seal slot  60 , and thus facilitates preventing spline seal  100  from undesirably slipping or backing out from slot  60 . As a result, retainer tab  150  facilitates minimizing leakage through the segmented turbine nozzle assembly clearance gaps and thus facilitates enhancing engine performance and component life expectancy.  
         [0028]      FIG. 5  is perspective view of a further alternative embodiment of spline seal  100 . The embodiment illustrated in  FIG. 5  is substantially similar to the embodiment illustrated in  FIG. 3  and components of spline seal  100  illustrated in  FIG. 5  that are identical to components of spline seal  100  illustrated in  FIG. 3 , are identified in  FIG. 5  using the same reference numerals used in  FIG. 3 . Accordingly, spline seal  100  includes retainer tab  122  and body portion  120 . Spline seal  100  also includes a second retainer tab  200  that extends outward from body portion  120  and is not co-planar with body portion  120 . Specifically, in the exemplary embodiment, retainer tab  200  extends outward from spline seal outer perimeter  102 , and more specifically, is formed within a spline seal corner portion  114 . Accordingly, in the exemplary embodiment, retainer tab  200  is substantially triangular shaped. Alternatively, retainer tab  200  may extend from any portion of body portion  120 , or have any shape, that enables retainer tab  200  to function as described herein.  
         [0029]     In the exemplary embodiment, retainer tab  200  is oriented at an oblique angle β with respect to body radially inner surface  126 . Alternatively, retainer tab  200  may be oriented at any angle β with respect to radially inner surface  126  that enables retainer tab  200  to function as described herein.  
         [0030]     In the exemplary embodiment, retainer tab  200  is formed integrally with body portion  120 . More specifically, in the exemplary embodiment, retainer tab  200  is formed by bending a portion of spline seal  100  to a desired angle β. Alternatively, retainer tab  200  may be coupled to body portion  120 .  
         [0031]      FIG. 6  is a perspective view of another alternative embodiment of spline seal  100 . The embodiment illustrated in  FIG. 6  is substantially similar to the embodiment illustrated in  FIG. 3  and components of spline seal  100  illustrated in  FIG. 6  that are identical to components of spline seal  100  illustrated in  FIG. 3 , are identified in  FIG. 6  using the same reference numerals used in  FIG. 3 . Accordingly, spline seal  100  includes body portion  120  and a first retainer tab  210  and a second retainer tab  220 . Specifically, in the exemplary embodiment, each retainer tab  210  and  220  extends outward from spline seal outer perimeter  102 , and each is formed partially within a spline seal corner portion  114 . More specifically, in the exemplary embodiment, spline seal  100  includes a retainer division slot or cut  222  that extends a distance axially upstream from spline seal trailing edge side  108 . In the exemplary embodiment, slot  222  is substantially centered between spline seal sides  104 , such that retainer tabs  210  and  220  are approximately the same size. Alternatively, slot  222  is non-centered with respect to spline seal  100  and retainer tabs  210  and  220  have different sizes. Accordingly, in the exemplary embodiment, retainer tabs  210  and  220  are each substantially rectangular-shaped.  
         [0032]     Slot  222  extends from spline seal trailing edge  108  to a relief stop hole  230  extending through spline seal  100 . Stop hole  230  facilitates reducing stresses that may be induced to spline seal  100  adjacent retainer tabs  210  and  220  and also facilitates preventing the initiation or propagation of cracks that may develop within spline seal  100  between retainer tabs  210  and  220 .  
         [0033]     In the exemplary embodiment, retainer tab  210  is oriented at an oblique angle θ with respect to body radially outer surface  124 , and retainer tab  220  is oriented at an oblique angle β with respect to body radially inner surface  126 . Alternatively, retainer tabs  210  and  220  may be oriented at any angles θ or β with respect to radially outer and inner surfaces  124  and  126 , respectively, that enables retainer tabs  210  and  220  to function as described herein.  
         [0034]     In the exemplary embodiment, retainer tabs  210  and  220  are each formed integrally with body portion  120 . More specifically, in the exemplary embodiment, retainer tabs  210  and  220  are each formed by bending a portion of spline seal  100  that is adjacent to slot  222  to a respective desired angle θ or β. Alternatively, either retainer tab  210  and/or retainer tab  220  may be coupled to body portion  120 .  
         [0035]     In each embodiment, the above-described spline seals include a retainer tab that facilitates preventing the spline seal from inadvertently backing out of the nozzle assembly spline seal slots. More specifically, in each embodiment, the retainer tab extends outward from the body portion of the spline seal to facilitate limiting radial and movement of the spline seal within the spline seal slot. As a result, during engine operation, the retainer tabs facilitate reducing leakage through the clearance gap defined between circumferentially adjacent turbine nozzles. Accordingly, engine performance and component useful life are each facilitated to be enhanced in a cost effective and reliable means. Moreover, the invention provides a means wherein existing spline seals can be modified to facilitate enhancing turbine engine performance.  
         [0036]     Exemplary embodiments of turbine nozzles are described above in detail. The spline seals are not limited to use with the specific nozzle embodiments described herein, but rather, the spline seals can be utilized independently and separately from other turbine nozzle components described herein. Moreover, the invention is not limited to the embodiments of the spline seals described above in detail. Rather, other variations of spline embodiments may be utilized within the spirit and scope of the claims.  
         [0037]     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.