Abstract:
An exhaust nozzle assembly includes a plurality of interfitting flap assemblies that are moveable between a maximum area ratio and a minimum area ratio. Each of the pluralities of flap assemblies includes a slot and a wing. The wing fits within an adjacent slot of an adjacent flap assembly. Each of the flap assemblies includes a divergent element that provides a specific geometric shape forming the trailing edge surfaces. The flap element is attached to the divergent element and extends to a static structure. The flap element and the divergent element combine to form a continuous faceted outer surface of the exhaust nozzle assembly substantially void of gaps throughout the range of motion between the maximum and minimum area ratios.

Description:
[0001]     The US Government may have certain rights in this invention in accordance with Contract Number N00019-02-C-2003 awarded by the United States Navy. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to an exhaust nozzle assembly for a gas turbine engine. More particularly this invention relates to interfitting flap assemblies for a variable exhaust nozzle assembly.  
         [0003]     An exhaust nozzle for a gas turbine engine accelerates gas flow exiting the engine increasing thrust. A fixed exhaust nozzle including a fixed exhaust opening provides optimal performance for a single operating condition. A variable exhaust nozzle opens and closes to provide differing opening sizes to optimize performance for many operating conditions. Such exhaust nozzles typically include a plurality of flap sections moveable radially to change the opening area of the exhaust nozzle.  
         [0004]     Typically, a seal is provided on a hot side of the flaps for blocking a portion of a gap created between adjacent flaps during movement of the exhaust nozzle assembly. Disadvantageously, such seals cannot block or control all gaps created between adjacent flap assemblies during movement of the exhaust nozzle assembly.  
         [0005]     Accordingly, it is desirable to design and develop a variable exhaust nozzle assembly that minimizes gaps throughout all positions of the exhaust nozzle assembly.  
       SUMMARY OF THE INVENTION  
       [0006]     This invention is an exhaust nozzle assembly including a plurality of interfitting flap assemblies having a wing portion and a slot portion. The wing portion of one flap fits within a slot portion of an adjacent flap to minimize and control formation of gaps between each of the flap assemblies.  
         [0007]     The exhaust nozzle assembly includes a plurality of interfitting flap assemblies defining a variable cross-section opening. Pivoting of the flap assemblies about a fixed pivot varies the cross-sectional area of the opening. Each of the flap assemblies includes a divergent element, a flap element, and a seal. The seal is disposed between adjacent flap assemblies on an interior surface of the exhaust assembly to block gaps between adjacent flap assemblies. Each of the flap assemblies interfits into an adjacent flap assembly to provide a substantially uniform and continuous, faceted outer surface of the exhaust nozzle assembly.  
         [0008]     Each of the seals includes a tented portion extending rearward from a trailing edge. The trailing edge of the seal includes a notch. The tented portion is disposed along a plane different than the substantial planar surface of the remaining portions of the seal. The tented portion is bent outwardly away from the interior surface of the flap assemblies. The notched and tented portions are disposed substantially at the trailing edge of the exhaust nozzle assembly to reduce and control formation of gaps between adjacent flap assemblies during articulation.  
         [0009]     Accordingly, the exhaust nozzle assembly of this invention provides an improved flap assembly that reduces and controls gaps generated during articulation of a variable exhaust nozzle assembly.  
         [0010]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of an exhaust nozzle assembly for a gas turbine engine.  
         [0012]      FIG. 2  is a plan view of a flap assembly according to this invention.  
         [0013]      FIG. 3  is a plan view of several flap assemblies interfit with one another.  
         [0014]      FIG. 4  is an exploded view of two flap assemblies according to this invention.  
         [0015]      FIG. 5  is a top view of a divergent element.  
         [0016]      FIG. 6  is a side view of the divergent element shown in  FIG. 5 .  
         [0017]      FIG. 7  is a rear perspective view of two divergent elements interfit into one another.  
         [0018]      FIG. 8  is a rear cross sectional view of two-flap elements interfit into one another.  
         [0019]      FIG. 9  is an enlarged view of the interface between two flap elements.  
         [0020]      FIG. 10  is a perspective view of interfit flap assemblies viewed from the trailing edge.  
         [0021]      FIG. 11  is a plane view of an interior surface of adjacent flap assemblies including a seal.  
         [0022]      FIG. 12  is a perspective view of the seal. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     Referring to  FIG. 1 , an exhaust nozzle assembly  10  includes a plurality of interfitting flap assemblies  16  defining an opening  14 . Each of the flap assemblies  16  is pivotally attached to a static structure at pivots  18 . An actuator illustrated schematically at  17  is attached to move each of the flap assemblies  16 . Pivoting of the flap assemblies  16  varies the cross-sectional area of the opening  14 .  
         [0024]     Each of the flap assemblies  16  includes a divergent element  20 , a flap element  22 , and a seal  24 . The seal  24  is disposed between adjacent flap assemblies  16  on an interior surface  15  of the exhaust nozzle assembly  10  to substantially prevent leakage of exhaust gasses therethrough. Each of the flap assemblies  16  interfits into an adjacent flap assembly  16  to provide a substantially uniform and continuous, faceted outer surface  11  of the exhaust nozzle assembly  10 . The opening  14  includes a serrated trailing edge  21  defined by the divergent elements  20  of each flap assembly  16 . The serrated trailing edge  21  includes a plurality of aft most portions  28  and trailing edge surfaces  26  defined by the divergent elements  20 . The aft most portions  28  alternate with the trailing edge surfaces  26  creating the trailing edge  21  having a plurality of peaks and valleys.  
         [0025]     Referring to  FIG. 2 , each of the flap assemblies  16  includes the flap element  22  that is attached to the divergent element  20 . The divergent element  20  includes a wing segment  32  and the flap element  22  also includes a wing segment  34 . The wing segments  32 ,  34  combine to form a common wing  30 . The wing  30  extends from one side of the flap element  22  and a slot  39  is provided within each flap assembly  16  on a side opposite the wing  30 .  
         [0026]     Each flap assembly  16  defines a portion of the outer surface  11  and includes a crest  23  between tapered surfaces  25 . The tapered surface  25  gradually transition upward toward the crest  23 . The wing  30  is disposed on a separate plane below the tapered surface  25  of each flap assembly  16 .  
         [0027]     Referring to  FIG. 3 , several flap assemblies  16  are shown interfit with each other. Each wing  30  fits within the slot  39  of an adjacent flap assembly  16 . As the nozzle opening  14  expands and contracts, the wing  30  moves progressively into and out of the slot  39  formed in an adjacent flap assembly  16  such that no gap is formed therebetween. An interface  38  between adjacent flap assemblies  16  moves along the wing  30  during expansion. During contraction the interface  38  is at a position such that the tapered surfaces  25  of adjacent flap assemblies  16  abut to form the faceted outer surface  11 . The interface  38  between each flap assembly  16  moves, but is always covered by the wing  30  to provide the substantially continuous and uninterrupted faceted outer surface  11 . Although the interface  38  forms a visible seam between adjacent flap assemblies  16 , there are no gaps exposed along adjoining flap assemblies  16  through the full range of motion of each of the plurality of flap assemblies  16 .  
         [0028]     Referring to  FIG. 4 , each of the flap assemblies  16  includes the divergent element  20  and the flap element  22 . The flap element  22  includes the crest  23  and the tapered surfaces  25  to form a portion of the outer surface  11 . The flap element  22  is attached by way of the pivot  18  to a static structure of the engine  12  at one end and to the divergent element  20  on an end opposite the pivot  18 . Attachment of the flap element  22  to the divergent element  20  is as known and can include welding or the use of mechanical fasteners.  
         [0029]     The divergent element  20  includes the wing segment  34  that interfits within an adjacent divergent element  20 . The divergent element  20  defines the trailing edge surface  26  that is angled outwardly towards the aft point  28 . Each divergent element  20  includes bosses  36  for attaching to articulating mechanisms of the actuator  17  ( FIG. 1 ) utilized for actuating the flap assemblies  16 .  
         [0030]     Referring to  FIG. 5 , the divergent element  20  is shown and is formed to include a desired geometric shape that combines with adjacent divergent elements  20  to define the serrated trailing edge  21  for the exhaust nozzle assembly  10 . The divergent element  20  includes a sweep angle  40  and a plane length  41 . The plane length  41  in conjunction with the sweep angle  40  combined with adjacent divergent elements  20  provides desired performance characteristics and minimizes and controls the formation of gaps in the trailing edge  21 .  
         [0031]     The example divergent element  20  is a single cast piece. The material that is utilized to fabricate the divergent element  20  is compatible with the temperatures and the chemical composition of the exhaust gasses that are emitted from the gas turbine engine through the exhaust nozzle assembly  10 . Although, the example divergent element  20  is a cast piece, a worker skilled in the art with the benefit of this disclosure would understand that the divergent element  20  may be fabricated utilizing other known manufacturing processes.  
         [0032]     The wing segment  34  of the divergent element  20  deviates from the overall shape of the divergent element  20  and extends rearward of the trailing edge surface  26 . The wing segment  34  is shaped to interfit within an adjacent divergent element  20  such that when the exhaust nozzle assembly  10  is at its maximum opening, the wing segment  34  will remain within a slot  35  of an adjacent divergent element  20  thereby providing the substantially continuous outer surface  11  between adjacent flap assemblies  16 .  
         [0033]     Referring to  FIG. 6 , the divergent element  20  is shown in a side view to illustrate the wedge surface  46  and the wedge angle  42 . The sweep angle  40  and wedge angle  42  along with the surface wedge  46  and length  41  act in concert to provide desired operating characteristics and the desired serrated trailing edge  21 .  
         [0034]     Referring to  FIG. 7 , two divergent elements  20  are shown from a rear view with the flap element  22  omitted for clarity. The wing segment  34  of one divergent element  20  is disposed within the slot  35  of the adjacent divergent element  20 . The divergent elements  20  include a lip portion  48  that is provided to conform to assembly of the flap element  22 . The lip portion  48  accommodates the configuration of the flap element  22  to provide a substantially continuous outer surface of the flap assembly  16 .  
         [0035]     The wing segment  34  fits within the accompanying slot  35  of the adjacent divergent element  20 ; however, the wing segment  34  does not contact the adjacent divergent element  20  during movement. Instead the wing segment  34  moves within the slot  35  of the adjacent divergent element  20 . Because there is no contact between the wing segment  34  and the adjacent divergent element  20 , undesirable wear and friction between adjacent divergent elements  20  are substantially eliminated. Referring to  FIG. 8 , a cross-section of adjacent flap elements  22  is shown to illustrate the relationship between the wing segment  32  and the slot  37 . As in the divergent element  20 , the wing segment  32  of the flap element  22  is disposed within a slot  37  of an adjacent flap element  22 . The wing segment  32  does not contact any portion or surface of the adjacent flap element  22 . Interfitting wings  30  of each flap assembly  16  produces the continuous outer surface  11  of the exhaust nozzle assembly  10 .  
         [0036]     Each of the flap elements  22  includes ribbed portions  50 . The ribbed portions  50  strengthen the flap elements  22  and provide for the inclusion of cooling features or articulation features that are utilized to move each of the flap assemblies  16 .  
         [0037]     Referring to  FIG. 9 , an enlarged view of the interface  38  between the flap assemblies  16  is shown at the intersection between adjacent flap elements  22 . The wing segment  32  of each flap element  22  fits within the slotted portion  37  of the adjacent flap element  22 . The wing segment  32  recedes within the slot  37  of the adjacent flap element  22  during articulation and movement of each of the flap assemblies  16 . Because the wing segment  32  does not contact the adjacent flap element  22  frictional forces are not introduced, however, the gaps between adjacent flap assemblies  16  are substantially eliminated providing the desirable continuous surface of the exhaust nozzle assembly  10 .  
         [0038]     Referring to  FIG. 10 , two adjacent flap assemblies  16  are shown in a view looking toward the trailing edge surface  26 . The flap element  22  is attached to the divergent element  20  such that the two form a substantially continuous exterior surface. The flap element  22  and the divergent element  20  of the illustrated example are formed as a single composite piece. The material utilized can be of any material compatible with the environmental conditions experienced by the exhaust nozzle assembly  10 . A worker skilled in the art with the benefit of this disclosure would understand what types of materials and processes are required to fabricate elements consistent and compatible with operation in the extreme conditions of the exhaust nozzle assembly.  
         [0039]     The interface between adjacent flap assemblies  16  may result in a gap  52  along the trailing edge  21  for some exhaust nozzle openings. The gap  52  is minimized by geometric configuration of the wings  30  of the flap assemblies  16  and the fit between adjacent divergent elements  20 . Further, the seal  24  is disposed on the interior surface  15  between adjacent flap assemblies  16  for covering the gap  52 . The seal  24  is comprised of sheet metal that is attached to move and maintain a position relative to the flap assemblies  16  through the range of motion.  
         [0040]     Referring to  FIG. 11 , the seal  24  disposed on the interior surface  15  of each of the flap assemblies  16  is shown. The seal  24  includes a notch  54 . The notch  54  conforms to the geometry of adjacent divergent elements  20  such that a portion of the seal  24  can be positioned further towards the trailing edge  21 . Each of the seals  24  includes a tented portion  56 . The tented portion  56  is rearward of the notch  54  along a plane different than the substantial planar surface  58  of the remaining portions of the seal  24 . The tented portion  56  is bent outwardly away from the interior surface  15  of the flap assemblies  16 . This provides the flexibility of the seal  24  to not only block gaps produced during articulation of the exhaust nozzle assembly  10 , but also provides a desired geometry for reducing and substantially eliminating potential gaps through trailing edge  21  resulting from articulation of adjacent flap assemblies  16 .  
         [0041]     Although a preferred embodiment of this invention 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.