Patent Publication Number: US-8123228-B2

Title: Augmentor spray bar mounting

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of Ser. No. 11/174,378, filed Jun. 30, 2005, and entitled AUGMENTOR SPRAY BAR MOUNTING, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     U.S. GOVERNMENT RIGHTS 
     The invention was made with U.S. Government support under contract N00019-02-C-3003 awarded by the U.S. Navy. The U.S. Government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to turbine engines, and more particularly to turbine engine augmentors. 
     Afterburners or thrust augmentors are known in the industry. A number of configurations exist. In a typical configuration, exhaust gases from the turbine pass over an augmentor centerbody. Additional fuel is introduced proximate the centerbody and is combusted to provide additional thrust. In some configurations, the augmentor centerbody is integrated with the turbine centerbody. In other configurations, the augmentor centerbody is separated from the turbine centerbody with a duct surrounding an annular space between the two. U.S. Pat. Nos. 5,685,140 and 5,385,015 show exemplary integrated augmentors. 
     The centerbody may contain a burner serving as a combustion source. For introducing the additional fuel, a number of spray bars may be positioned within generally radially extending vanes. A pilot may be proximate an upstream end of the tailcone. Alternatively or additionally to the burner, a number of igniters may be positioned within associated ones of the vanes to ignite the additional fuel. Trailing portions of the vanes may serve as flameholder elements for distributing the flame across the flow path around the centerbody. 
     Separately, electro-graphitic carbon materials have been developed for a variety of uses. US Pre-grant Publication 20050084190A1 discloses a variable vane inner diameter (ID) bushing made from electro-graphitic carbon. 
     SUMMARY OF THE INVENTION 
     Accordingly, one aspect of the invention involves a turbine engine. A centerbody is positioned within a gas flowpath from upstream to downstream. The augmentor has upstream and downstream shell sections, a downstream rim of the upstream shell section meeting an upstream rim of the downstream shell section shell section. A plurality of vanes are positioned in the gas flowpath outboard of the centerbody. An augmentor spray bar fuel conduit extends through the centerbody and a first of the vanes to deliver fuel to the centerbody. A seal is mounted to the spray bar and positioned in a recess extending from at least one of the downstream rim of the upstream shell section and upstream rim of the downstream shell section shell section. The seal has a first portion and a second portion engaging the first portion in a backlocked interfitting. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic longitudinal sectional view of an aircraft powerplant. 
         FIG. 2  is an aft view of an augmentor of the powerplant of  FIG. 1 . 
         FIG. 3  is a side view of a spray bar array and fueling manifold of the augmentor of  FIG. 2 . 
         FIG. 4  is a front view of the spray bar array and manifold of  FIG. 3 . 
         FIG. 5  is a partially exploded view of a spray bar of the array of  FIGS. 3 and 4 . 
         FIG. 6  is an aft view of a spray bar-to-centerbody seal. 
         FIG. 7  is a transverse sectional view of the seal of  FIG. 6 . 
         FIG. 8  is an exploded view of the seal of  FIG. 6 . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a gas turbine engine  10  comprising, from upstream to downstream and fore to aft, a fan  11 , a compressor  12 , a combustor  14 , a turbine  16 , and an augmentor  18 . Air entering the fan  11  is divided between core gas flow  20  and bypass air flow  22 . Core gas flow  20  follows a path initially passing through the compressor  12  and subsequently through the combustor  14  and turbine  16 . Finally, the core gas flow  20  passes through the augmentor  18  where additional fuel  19  is selectively added, mixed with the flow  20 , and burned to impart more energy to the flow  20  and consequently more thrust exiting an engine nozzle  24 . Hence, core gas flow  20  may be described as following a path essentially parallel to the axis  26  of the engine  10 , through the compressor  12 , combustor  14 , turbine  16 , and augmentor  18 . Bypass air  22  also follows a path parallel to the axis  26  of the engine  10 , passing through an annulus  28  along the periphery of the engine  10  to merge with the flow  20  at or near the nozzle  24 . 
     The augmentor comprises a centerbody  30  generally symmetric around the axis  26  and formed as a portion of an engine hub. The exemplary centerbody has a main portion  32  and a tailcone  34  downstream thereof. Circumferentially arrayed vanes  36  have leading and trailing extremities  37  and  38  and extend generally radially between the centerbody  30  and a turbine exhaust case (TEC)  40 . Each of the vanes may be an assembly of a leading main body portion  42  and a trailing edge box  44 . The vanes have circumferentially opposite first and second sides  46  and  48  ( FIG. 2 ). The trailing edge box  44  may contain a spray bar (discussed below) for introducing the additional fuel  19 . The centerbody may contain a burner  50  for combusting fuel to, in turn, initiate combustion of the fuel  19 . The burner  50  and spray bars may be supplied from one or more supply conduits (not shown) extending through or along one or more of the vanes to the centerbody. As so far described, the engine configuration may be one of a number of existing engine configurations to which the present teachings may apply. However, the teachings may also apply to different engine configurations. 
       FIGS. 3 and 4  show portions of an augmentor fueling system  60  including a manifold  62  for feeding fuel to an array of spray bars  64 . The manifold  62  may be located within the centerbody  30 .  FIG. 5  shows further details of an exemplary spray bar  64 . The exemplary spray bar is a dual conduit spray bar having first and second conduits  66  and  68 . The conduits  66  and  68  are secured to each other by blocks  69  having a pair of apertures respectively receiving the conduits. The conduits have proximal end portions mounted to outlets of a spray bar block  70  (e.g., by brazing or welding). The block  70  has an inboard end  72  bearing inlets for connection to the manifold  62 . The exemplary block  70  includes inboard and outboard slots  74  and  76 . The inboard slot  74  receives a seal (not shown) for engaging the centerbody structure. The outboard slot  76  receives first and second side halves of the associated vane. Each of the spray bars carries a plurality of nozzles  80  and wear blocks  82 . Each nozzle has an aperture  81  for discharging an associated jet of fuel. Each wear block has a central aperture  83  which receives the associated nozzle  80 . Whereas prior art systems provide wear blocks, nozzles, and spray bars as unitary or integrated (e.g., by welding or brazing) structures, the exemplary wear blocks  82  are otherwise formed. In the exemplary embodiment, each of the nozzles  80  is integrated (e.g., by brazing or welding) with an associated boss  84  of the associated conduit  66  or  68 . The wear block  82 , however, is formed of a material that wears preferentially relative to adjacent material of the vane and nozzle. The wear block  82  may be mounted for reciprocal motion along a nozzle axis  86  by means of a retainer  88 . A spring  90  (e.g., compressed between the block  82  and the associated conduit) may bias the block  82  outward. In addition to wearing preferentially to mating details, the electrographitic material used for the wear members may deposit a thin layer of graphite at the wear interface. This deposition may serve to further reduce the rates of wear. 
       FIG. 6  shows further details of a seal  100  sealing a spray bar  64  to the centerbody  30 . As noted above, the seal encircles the spray bar and is captured in the slot  74  of  FIG. 5 . The slot  74  is between a first flange  102  and a second flange  104  ( FIG. 7 ) inboard thereof. The spray bar  64  passes through an aperture in the centerbody shell and the seal  100  is accommodated within the aperture. The aperture is formed by the combination of a recess  106  extending forward/upstream from an aft/downstream rim  108  of the centerbody main portion  32  on the one hand and a forward rim  110  ( FIG. 1 ) of the tailcone  34  (removed in  FIG. 6  to show the seal) on the other hand. The recess  106  has first and second lateral surfaces  112  and  114  and a forward/upstream end surface  116  forming respective associated surfaces of the aperture. The tailcone forward rim  110  (not shown in  FIG. 6 ) forms the aperture downstream surface. In cross-sectional planform, the aperture and recess  106  are half obround, with the sides  112  and  114  being straight and the end  106  being semicircular. The sides  112  and  114  are parallel to each other and have a direction  120  in a transverse plane. In the exemplary embodiment, this direction  120  is non-parallel to both a local radial direction  122  and a local direction  124  of the conduit length. Specifically, the directions  120  and  124  are off radial in opposite directions as is discussed below. 
     The periphery  126  of the seal  100  is complementary to the centerbody aperture to permit the seal to move reciprocally within the aperture (e.g., in the direction  120 ). The exemplary periphery is thus a non-right, non-circular, cylinder surface. A seal central aperture surface  128  may be complementary to a cross-section of the block  70  between the flanges  102  and  104 . The seal  100  has outboard and inboard surfaces or faces  130  and  132 . 
     The exemplary seal  100  is formed of two pieces in snap-fit, backlocking, engagement.  FIG. 8  shows further details of the exemplary seal  100 . The seal  100  has upstream and downstream ends  140  and  142  respectively semi-circular and flat as noted above for engaging the associated aperture surfaces  116  and  110 . The seal  100  also has first and second sides  144  and  146  for respectively engaging the aperture/recess first and second sides  112  and  114 . The exemplary seal is formed in first and second pieces  150  and  152 . At the forward/upstream end  140 , the first piece  150  has a rebate or notch  154  receiving a corresponding projection  156  of the second piece. Immediately aft/downstream thereof and extending to the seal central aperture  157 , the first piece  150  has a projection  158  received by a rebate  159  in the second piece. These projections/rebates form a half dovetail backlocked interfitting connection resisting transverse separation of the two seal halves  150  and  152 . Similarly, at the rear of the seal there are projections  160  and  162  received by rebates or notches  164  and  166 . The two halves may be snapped into engagement around the block  70 , with elastic deformation of the halves permitting an over-center snap fit engagement. The snap fit engagement may be reversible by unsnapping. In alternative embodiments (e.g., of barbed rather than half dovetail engagement) the engagement may be irreversible, requiring destructive removal of the seal. Other embodiments (e.g., requiring release tools for nondestructive removal) are possible. When the seal halves  150  and  152  are installed around the spray bar, the proximity of the flanges  102  and  104  prevents separation of the seal halves by relative translation in the direction  124 . 
     Exemplary seal material is a substantially monolithic electro-graphitic carbon. With exemplary centerbody and tailcone material being a nickel-based superalloy, electro-graphitic carbon has an advantageous preferential wear property. Additionally, the electro-graphitic carbon has advantageous temperature stability relative to polymers and other non-metallic sacrificial wear materials used in other applications. Thus, as thermal cycling, vibration, and the like cause relative motion of the seal and centerbody, the seal will preferentially wear. Eventually, the wear will be sufficient to require seal replacement. Alternative seals may be other than monolithic (e.g., having a metallic core carrying an electro-graphitic carbon exterior portion). The seals need not prevent all leakage. Especially as time passes, there will be gaps between the seals and their associated centerbody apertures. However, the effect of the seals is to reduce the magnitude flow through the apertures relative to what would occur in their absence. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.