Abstract:
Method and apparatus for providing an afterburner fuel-feed arrangement including an elongate fuel spraybar for distributing fuel to the afterburner section of a turbo-combustion engine. The spraybar has a longitudinal axis and includes a fuel-receiving spray head in fluid communication with a plurality of elongate fuel pipes surrounded by an elongate, aerodynamic-shaped shroud. The spray head is configured to be mounted in a casing of a turbo-combustion engine which projects the surrounded fuel pipes into an interior through-core of the engine in cross-wise orientation to a core gas flow thereof. The shroud has an interior lateral sidewall that includes a pipe-receiving portion configured to abuttingly engage a corresponding shroud-engaging portion of an exterior surface of one of the fuel pipes. The pipe-receiving portion is configured to substantially radially fix a fuel pipe, received therein, relative to the shroud. In this manner, the fuel pipes are supported along their length, and when the pipes are abuttingly engaged with the shroud, the braced configuration is stiffened which raises the eigenfrequencies of the assembly into ranges higher than those of the incorporating engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of U.S. Provisional Application Nos. 60/601,011 filed 12 Aug. 2004 and 60/522,205 filed 31 Aug. 2004. Said applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to afterburners for jet engines; and more particularly, the invention relates to afterburner fuel-feed arrangements for such engines which may be exemplarily employed on aircraft.  
       BACKGROUND OF THE INVENTION  
       [0003]     Afterburner spraybars for jet engines are well appreciated assemblies by those persons skilled in the relevant art. An example of such spraybars is found in International Publication Number WO 2004/033966 A1 which designates the United States, and in the corresponding United States Provisional Patent Application having Application No. 60/319,601; each of which are hereby expressly incorporated by reference for purposes of disclosure.  
         [0004]     In general, afterburner fuel spray arrangements are utilized to boost the thrust of jet engines during limited high-demand periods. Relevant to aircraft engines, such times can include, for instance, take off from the flight deck of an aircraft carrier.  
         [0005]     The afterburner spraybars are located in the core gas flow of the jet engine, and are therefore subjected to extremely high temperatures, which can also be quite variable. This can present challenges, especially to configurations such as that shown in WO 2004/033966 A1 in which fuel pipes are directly exposed to the hot core gases behind the turbine section of the engine. Another problem with such fuel-pipe-exposed configurations is that the unsupported, relatively long length of the fuel pipes can make the assembly susceptible to eigenfrequencies (natural or harmonic frequencies) falling within engine range frequencies which is also viewed as detrimental.  
         [0006]     For these reasons, it is generally known to provide protective heat shield structures for such afterburner fuel pipes, and even to distribute cooling bypass air thereto. One particular example is found in U.S. Pat. No. 5,297,391 wherein a fuel distributing pipe  52  is preceded (with respect to core gas flow) by a shielding tubular enclosure  54 . Through the illustrations of  FIGS. 4-6  of the &#39;391 patent, however, it is clear that the overall length of the fuel pipe  52  remains substantially unbraced with regard to the enclosure  54 . In fact, as depicted in  FIG. 5  of the &#39;391 patent, it is clear that a slit  70  must be maintained therebetween in order for cooling air to pass therethrough. Even though it could be said that it appears from  FIG. 6  that a distal or bottom end of the fuel pipe could be anchored in a wall end  66  of the enclosure  54 , it is not represented that the predominantly unsupported length of the fuel pipe  52  is braced against assuming harmonic oscillation, with the engine. This detrimental performance can obviously cause extreme vibration of the fuel pipe  52  and/or enclosure  54  resulting in unacceptable vibrations of, and friction and wear between, the several constituent components. Still further, each fuel pipe is individually enclosed, and no fuel pipes are arranged adjacent or abreast to one another in a crosswise orientation to the engine&#39;s core gas flow as defined by the present invention, and as will be described in greater detail hereinbelow. These individual assemblies disclosed in the &#39;391 patent are not only costly, but their required frequency of radial distribution within the core gas flow can compromise the throughput of the engine.  
         [0007]     For these reasons, as well as others that will become evident to those persons skilled in the art from the descriptive disclosure provided herein, the present invention has been developed to address these problems and provide additional benefits to users.  
       SUMMARY OF THE INVENTION  
       [0008]     As disclosed herein, the present invention is described with respect to three primary embodiments: (1) the afterburner fuel-feed arrangement alone; (2) the arrangement installed in a turbo-combustion engine; and (3) the arrangement installed in a turbo-combustion engine and mounted on an aircraft. In that the commonality between these several embodiments is the spraybar of the afterburner fuel-feed arrangement, and the other components of the developed embodiments are generally known, at least as utilized in the present disclosure, the invention is summarized on the basis of the spraybar.  
         [0009]     Therefore, in one embodiment, the present invention takes the form of an afterburner fuel-feed arrangement comprising (including, but not necessarily limited to) an elongate fuel spraybar for distributing fuel to the afterburner section of a turbo-combustion engine. The spraybar has a longitudinal axis and includes a fuel-receiving spray head in fluid communication with a plurality of elongate fuel pipes surrounded by an elongate, aerodynamic-shaped shroud. The spray head is configured to be mounted in a casing of a turbo-combustion engine (which is contemplated to include both turbo-jet and turbo-fan engine configurations) and thereby project the surrounded fuel pipes into an interior through-core of the engine in cross-wise orientation to a core gas flow therein to establish an installed configuration of the spraybar.  
         [0010]     In this embodiment, the shroud has an interior lateral sidewall that includes a pipe-receiving portion. The pipe-receiving portion is configured to abuttingly engage a corresponding shroud-engaging portion of an exterior surface of one of the plurality of elongate fuel pipes. The pipe-receiving portion is configured to substantially maintain the position of a fuel pipe, received therein, relative to the shroud. In this manner, the fuel pipes are supported along their length, and when the pipes are abuttingly engaged with the shroud, the thereby braced configuration is stiffened which raises the eigenfrequencies of the assembly (arrangement) into ranges higher than those of the incorporating engine. Each such feature serves and functions to minimize vibration, reduce wear, and increase operational life of the elongate fuel spraybar assembly.  
         [0011]     In a further development (variation), the shroud has an elliptically tubular cross-sectional shape, taken perpendicularly to the longitudinal axis of the spraybar, along a predominance of a length of the shroud. Furthermore, the elliptical cross-sectional shape defines a long and short cross-axis of the shroud, the long cross-axis of the shroud being substantially aligned, in a preferred installed configuration, with a direction of core gas flow of the engine.  
         [0012]     In an optional development, at least two of the several elongate fuel pipes are arranged adjacent and substantially parallel to one another, and with a longitudinal axis of each perpendicularly intersecting the short cross-axis of the shroud. As may be best appreciated in  FIG. 9 , this orientation places the fuel pipes (in the illustrated case, a pair of fuel pipes) abreast of one another, and oriented long-wise (the combined width of the adjacent pipes, plus two thickness of the shroud) across the core gas flow. Heretofore, such orientations have been avoided in order present as little resistance to the core flow as possible by the fuel pipes. The unique configuration of the present adjacent fuel pipes, however, within the aerodynamic, elliptically shaped shroud, facilitates such an advantageous orientation. Still further, such a configuration reduces the total number of spraybar assemblies (compared to previously known configurations) necessary to adequately feed an engine&#39;s afterburner.  
         [0013]     In a complementary development, the shroud and all of the elongate fuel pipes have a longitudinal axis oriented substantially parallel to the longitudinal axis of spraybar.  
         [0014]     As a further optional complement, the two elongate fuel pipes are adjacently and abuttingly arranged one to the other, and the so paired fuel pipes are in abutting contact with opposite interior lateral sidewalls of the shroud. In this manner, the elongate fuel pipes constitute a brace in the shroud against bending moments about the long cross-axes of the shroud.  
         [0015]     As intimated above, another beneficial feature of the present invention is that accordingly configured spraybars have eigenfrequencies greater than eigenfrequencies of receiving engines thereof.  
         [0016]     In a further development, the shroud further includes multiple (a plurality of) pipe-receiving portions, each of which includes an elongate recessed portion flanked on each of two lateral sides thereof by an elongate raised-ridge portion. It is this configuration that presents the “wave” or fluted interior surface of the shroud.  
         [0017]     In one example, a tight friction-fit exists between each of the plurality of pipe-receiving portions and a respective fuel pipe received therein when the spraybar is in an inactive state without fuel being fed through the fuel pipes (see  FIG. 9 ). A comparatively reduced friction-fit exists therebetween when the spraybar is in an active state with fuel being fed through the fuel pipes (see  FIG. 10 ).  
         [0018]     It is preferred that each of the fuel pipes be tubular, and more preferably cylindrical in shape (having a circular cross-section) and that each respective pipe-receiving portion of the shroud be concavely configured and sized to establish an abutting conformance fit with a respective fuel pipe received therein when in the inactive state. In this manner, relative motion (or resistance thereto) between the fuel pipes and shroud provides mechanical damping to the spraybar and thereby decreases stress caused by vibrations.  
         [0019]     Conversely, but in a complementary manner, in the active state in which the fuel pipes are being cooled (but the shroud is obviously still being heated by the core gas flow), a spaced-apart, but trapped configuration is established for the cylindrical fuel pipes received within the recessed portion (bounded by the raised-ridge portions) of the pipe receiving configuration at the interior lateral wall of the shroud. It should be appreciated that in this configuration a gap space can at least intermittently exist between the fuel pipes and shroud. Benefits that are derived therefrom are that the transfer of heat (given the buffering air gap) between the pipes and shroud is drastically reduced, and that the thermal stress of the shroud is also reduced.  
         [0020]     Because of the fluted configuration presented by the pipe receiving portion(s) on the interior lateral sidewall(s) of the shroud, these receiving portions, and particularly the raised-ridge portions, brace against bending moments about long cross-axes of the shroud.  
         [0021]     As may be best appreciated in  FIGS. 6 and 8 , an expanding transition portion is interposed between the spray head and the shroud. An interior wall of the expanding transition portion is provided with a plurality of recesses therein, each of such recesses being aligned with an elongate recessed portion of a respective pipe-receiving portion of the interconnected shroud.  
         [0022]     In still a further development of the invention, the long cross-axis of the shroud (see  FIG. 9 ) is substantially aligned, in the installed configuration, with a longitudinal axis of the engine. In this orientation, the shroud acts as a directing vane for the core gas flow of the engine. In a preferred embodiment, the direction imparted to the gas flow is aligned with the longitudinal axis of the engine thereby easing throughput.  
         [0023]     In yet a further development, a cooling air inlet opening is provided in the spraybar for receiving relatively cool engine bypass air into an interior space of the shroud at a location proximate a head-end of the spraybar. At a distal end of the spraybar, a cooling air outlet opening is provided for exhausting cooling air therefrom. As may be best appreciated from  FIG. 5 , the cooling air outlet is of an elongated elliptical shape, dictated at least in partial dependence upon the elliptical shape of the shroud, which is effectively cut at an angle to a longitudinal axis thereof to provide such an outlet opening. In a complementary manner, it can be said that the cooling air outlet has an opening area greater than an interior cross-sectional area within the shroud taken perpendicular to the longitudinal axis of the spraybar at a lengthwise location of the spraybar proximate the cooling air outlet (compare  FIGS. 5 and 10 ).  
         [0024]     As may be further appreciated from  FIG. 5 , the configuration of the cooling air outlet can be described in terms of a plane that is coincident with the opening area of the cooling air outlet being transversely oriented to the longitudinal axis of the spraybar.  
         [0025]     Due to the preferred orientation of the spraybar relative to the core gas flow as depicted at least in  FIGS. 2 and 3 , the cooling air outlet forms a negative air-scoop relative to the core gas flow in the engine through-core in the installed configuration. In this manner, an effectively negative pressure is instituted outside the cooling air outlet thereby tending to draw the cooling air from the shroud, and at a minimum does not present back pressure thereto.  
         [0026]     Several beneficial features have been described hereinabove regarding the presently disclosed invention(s). It should be appreciated that these observations are not exhaustive, and further advantages and benefits will become obvious to those persons skilled in the art in view of the present disclosure. Still further, the embodiment and examples described herein should not be considered as limiting, but are provided to assist persons skilled in the art to implement the inventions, but the meets and bounds of which are delimited exclusively by the patented claims. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0027]      FIG. 1  is a perspective view showing an exemplary aircraft, with engines adapted according to the present invention, mounted thereto;  
         [0028]      FIG. 2  is a perspective view, shown in partial cutaway, illustrating an installed configuration of a pair of elongate fuel spraybars on an engine and configured according to the teachings of the present invention;  
         [0029]      FIG. 3  is a schematic view, taken as a radial section, showing details of the installed configuration of one spraybar;  
         [0030]      FIG. 4  is a detailed perspective view of an elongate fuel spraybar shown in fluid communication with a fuel source;  
         [0031]      FIG. 5  is a detailed perspective of the elongate fuel spraybar of  FIG. 4 , but taken from the opposite direction, and illustrating details of the negative air-scoop cooling air outlet of the spraybar;  
         [0032]      FIG. 6  is a partial-cutaway perspective view of the spraybar illustrating an exemplary embodiment of the pipe receiving portion of the shroud;  
         [0033]      FIG. 7  is a partial-cutaway, perspective view similar to  FIG. 6 , but showing a pair of elongate fuel pipes installed within the shroud;  
         [0034]      FIG. 8  is a cutaway perspective view illustrating an interior half of a spraybar, and more particularly showing interior details of the shroud;  
         [0035]      FIG. 9  is a cross-sectional view of a spraybar illustrating an inactive fuel-feed state (configuration) in which no fuel is being fed through the fuel pipes;  
         [0036]      FIG. 10  is a cross-sectional view of the spraybar as illustrated in  FIG. 9 , but in an active, feel-feeding state in which the fuel pipes have been cooled relative to the configuration of  FIG. 9 ;  
         [0037]      FIG. 11  is a cross-sectional view of the spraybar taken at a top location or portion of the embodiment depicted in  FIGS. 14 and 15  below the spray head and where the fuel pipes are spaced apart, one from the other;  
         [0038]      FIG. 12  is a cross-sectional view of the spraybar taken at a lower location or portion of the embodiment depicted in  FIGS. 14 and 15  showing the paired fuel pipes welded together and in an inactive state;  
         [0039]      FIG. 13  corresponds to  FIG. 12 , but in an active state;  
         [0040]      FIG. 14  is a perspective, cutaway view of an exemplary embodiment of the spraybar in which the paired fuel pipes are welded together along a majority of their length; and  
         [0041]      FIG. 15  is a detailed cutaway, perspective view showing details of the paired fuel pipes adjacent the spray head of the spraybar. 
     
    
     DETAILED DESCRIPTION  
       [0042]     Exemplary embodiments of the present invention are depicted in the accompanying drawings; the primary and unique common component being the configuration and orientation of an elongate fuel spraybar  28  for a turbo-combustion engine  12 , which is contemplated to take the form of either a turbo-jet or turbo-fan configuration.  
         [0043]      FIG. 1  illustrates an actual utilization embodiment of the invention wherein an aircraft  10  is shown with a pair of turbo-combustion engines  12  mounted thereupon.  
         [0044]      FIG. 2  illustrates in detail, one of the engines  12  depicted as being mounted on the aircraft  10  in  FIG. 1 . In  FIG. 2 , the engine  12  is shown having a longitudinal axis  14  centrally located through a casing  16  of the engine  12 . Defined within the casing  16  is an interior through-core  18  which is generally divided into a gas turbine section  23  preceding an afterburner section  24 . Through the core  18 , and the turbine and afterburner sections  23 ,  24 , a core gas flow  20  passes.  
         [0045]     An afterburner fuel-feed arrangement  26  is shown generally interposed between the turbine and afterburner sections  23 ,  24 , and ahead of a flame holder  21  supported on flame holder struts  22 . In  FIG. 2 , the spraybar  28  is shown in an installed configuration  30  with a longitudinal axis  32  thereof generally radially oriented with respect to the longitudinal axis  14  of the engine  12 .  
         [0046]     It may be further appreciated in  FIG. 2  that the casing  16  defines a bypass air annulus  19  through which bypass air is directed during the engine&#39;s  12  operation. The bypass annulus  19  is exteriorly bounded by an outer sleeve  17  and interiorly bounded by an inner sleeve  15 . Bypass air is diverted into the annulus  19  downstream of the intake fan of the engine  12 . A cooling air inlet  86  of the afterburner fuel-feed arrangement  26  is located in the bypass annulus  19  with its opening directed forwardly into the oncoming bypass air  19 . In this manner, bypass air is diverted through the afterburner fuel-feed arrangement  26  as described in greater detail hereinbelow. It should also be appreciated that a majority of the bypass air  19  flows past the spray head  34  of the afterburner fuel-feed arrangement  26  and is redirected back into the interior through-core  18  at the afterburner section  24  of the engine  12 . An exemplary course of bypass air  19  that is diverted through the spraybar  28  is shown in  FIG. 3  utilizing a solid outlined arrow in the casing annulus, and then with a dashed-line outlined arrow in the afterburner fuel-feed arrangement  26 .  
         [0047]     The radial section view of  FIG. 3  schematically depicts the installed configuration  30  of a spraybar  28  in an engine  12 . The spraybar  28 , in this instance, constitutes an afterburner fuel-feed arrangement  26 . The spraybar  28  includes a spray head  34 , which in this illustration is connectable to a fuel source  35  (see  FIG. 4 ). The location of the spray head  34  designates a head-end  36  of the spraybar  28 . In  FIG. 3 , an elongate fuel pipe  38 , preferably cylindrical shaped, is depicted. As can be best appreciated from  FIG. 7 , the visible fuel pipe  38  in  FIG. 3  is a front pipe (from the perspective of the drawing) of a pair  46  of elongate fuel pipes housed within a shroud  50  and oriented crosswise to the core gas flow  20 .  
         [0048]     The fuel pipe  38  includes fuel outlets  39 , exemplarily shown in  FIG. 3  to number three, through which fuel from the source  35  is spray-ejected. From  FIG. 3 , it may be appreciated that each fuel pipe  38  has a longitudinal axis  40  and an exterior surface  42 . As will be discussed in greater detail herebelow, and is more clearly illustrated in  FIGS. 7, 9  and  10 , a portion of the exterior surface  42  of the fuel pipe  38  constitutes a shroud-engaging portion  44 .  
         [0049]      FIG. 3  also illustrates a preferred embodiment of the afterburner fuel-feed arrangement  26  wherein a spraybar  28  is mounted in the casing  16  of the engine  12 , independently from the flame holding arrangement. In the illustration, the flame holding arrangement is schematically depicted as comprising a flame holder  21  supported upon struts  22  which are fixed to the casing  16 .  
         [0050]     It should also be mentioned that  FIG. 3  schematically illustrates an installed orientation, or configuration  30  of the spraybar  28  in which a cooling air outlet  88  is located at the distal end thereof, and oriented to form a negative air-scoop  94 . This negative air-scoop  94  can be considered to be akin to conventional air-scoops employed, for example, as air rams on airplanes. The “negative” aspect is achieved by effectively twisting the scoop one-hundred and eighty degrees with respect to oncoming-flow, which in the instance of the present invention, is the core gas flow  20 . Therefore, the cooling air outlet  88  faces predominantly away from the oncoming core gas flow  20  so that a low-pressure zone or region is developed about the open area  90  of the outlet  88  so that cooling air is effectively withdrawn therefrom, without the possibility of backpressure. Still further, the aerodynamic characteristics of the elliptically shaped shroud assure very little wake-effect, downstream therefrom.  
         [0051]     The open area  90  of the air outlet  88  is illustrated in  FIG. 5 , where a reference plane  92  which contains (is coincident with) the open area  90  is provided for establishing relative orientations and configurations of outlet  88  with respect to the balance of the spraybar  28 .  
         [0052]     As intimated hereinabove,  FIG. 4  provides a perspective view of the embodiment of the present invention in which the afterburner fuel-feed arrangement  26  is constituted exclusively by the elongate spraybar  28 , which in this illustrated embodiment is shown fluidly connected with a fuel source  35  (which is not necessarily a required component of the instantly described embodiment of the invention). Here, however, exemplary placement of a cooling air inlet  86  into the spraybar  28  is shown proximate the spray head  34 , and the elliptical, elongate nature of the shroud  50  is illustrated. Still further, the longitudinal axis  32  of the spraybar  28  is shown, as is the length  56  of the shroud  50 . Fuel outlets  51  through the shroud  50  are also shown, and should be understood to align with fuel outlets  39  of at least one of the fuel pipes  38  in the assembled configuration of the afterburner arrangement  26 .  
         [0053]      FIGS. 6-8  provide various cutaway views of the spraybar  28 .  FIG. 6  illustrates the spraybar  28  without fuel pipes  38  installed therein, and as well indicates the longitudinal axis  54  of the shroud  50 . The interior space  52  of the shroud  50  can be best appreciated from the cross-section of  FIG. 9 .  
         [0054]     The spray head  34  is generally cylindrically shaped, while the shroud  50  is generally elliptically shaped. Therefore, an expanding transition portion  82  is interconnectively interposed therebetween. A recess  84  is shown in an interior surface of the transition portion  82  which serves as a lead-in to an elongate recessed portion  70  of the pipe receiving portion  68  of the shroud  50 . Details of the interior lateral sidewall  66  of the shroud  50  are clearly depicted in  FIGS. 8 and 9 . Therein, a “wave” or fluted configuration of the lateral sidewall  66  is shown as being collectively constituted by the elongate, concave, recessed portion  70  that is flanked on each lateral side thereof by an elongate raised-ridge portion  72 .  
         [0055]     Particularly suitable methods for manufacturing the shroud  50  include cold-drawing a tube through a slotted mold or die having a shape corresponding to the desired cross-sectional shape of the shroud, including the “wave” or fluted configuration of the pipe-receiving portions  68  located on the shroud&#39;s lateral sidewall  66 . Benefits of such manufacture includes the production of a relatively rigid shroud having high thermal strength. As an alternative, it is also contemplated that the shroud  50  may be produced by extrusion methods.  
         [0056]     It will be appreciated by those persons skilled in the art, especially when taken together with the illustrations of  FIGS. 9 and 10 , that the wave-configuration of the pipe receiving portion  68  acts and serves as a brace  74  to the shroud  50 . The bracing action of this configuration resists bending moments in the shroud  50 , and consequently the spraybar  28 , in directions substantially perpendicular to the longitudinal axis  76  of symmetry of the pipe receiving portion  68 .  
         [0057]      FIG. 7  is also a cutaway view of the spraybar  28 , but with a pair  46  of elongate fuel pipes  38  installed within the shroud  50 . From this Figure, especially when taken together with  FIG. 9 , it can be appreciated that the pair  46  of elongate fuel pipes serve as a brace to the spraybar  28  against bending moments, particularly those directed across the paired fuel pipes  38  (aligned with the short axis  64 ).  
         [0058]      FIGS. 9 and 10  illustrate cross-sectional views of the elongate spraybar  28 , taken along the length  56  of the shroud  50 . In each, the elliptically tubular cross-sectional shape  58  of the shroud  50 , and consequently a predominance of the spraybar  28  is shown. An interior cross-sectional area  60  of the shroud  50  is depicted in  FIG. 10 . Furthermore, the elliptical shape also defines long cross-axis  62  and short cross-axis  64 . Still further, the alignment of fuel outlets  39 ,  51  can be appreciated from these figures.  
         [0059]      FIG. 9  illustrates an inactive state of the afterburner fuel-feed arrangement  26 . In this configuration, no afterburner fuel is being fed through the fuel pipes  38 . In contrast,  FIG. 10  illustrates an active state in which fuel is being fed through the fuel pipes  38 . By comparison, the fuel pipes  38  are relatively cooler in the active state and experience a certain degree of radial contraction. In the inactive state of  FIG. 9 , a tight friction fit  78  is established between the fuel pipes  38  and shroud  50  at the engaging portion  44 . Conversely, in the active state of  FIG. 10 , due to the constriction of the cooled fuel pipes  38 , a reduced friction fit  80  is established with the shroud  50 . It is contemplated that the abutting fit between the pipes  38  and shroud  50  may be merely reduced in the active state, or as depicted in  FIG. 10 , a gap air space may be created therebetween. In either event, the location of the fuel pipes  38  relative to the shroud  50  is maintained by the raised-ridge portions  72  of the pipe receiving portion  68  formed on the interior of the shroud  50 .  
         [0060]     One particularly preferred and exemplary embodiment of the elongate fuel spraybar  28  is illustrated in  FIGS. 11-15 .  FIG. 14  provides a cut-away perspective view of the entire length of the spraybar  28 , with the interior thereof exposed to reveal a pair of associated fuel pipes  38 . A detailed cut-away, perspective view of the spray head  34  is provided in  FIG. 15  where the manifold for the distribution of fuel to each pipe  38  is shown. As depicted, at the spray head  34 , the two fuel pipes  38  are separated from one another, but converge toward each other at a top portion  47  thereof into an adjacent and parallel orientation. As illustrated, the adjacent portions of the fuel pipes  38  are joined together by a braze-weld connection  49  along a majority of their extension length. A cross-section depicting the fuel pipes  38  in their separated configuration adjacent the spray head  34  is illustrated in  FIG. 11 . An example of the two pipes&#39; orientation along their welded-together length is depicted in  FIG. 12  regarding an inactive state in which fuel is not flowing through the pipes  38  and therefore abutting engagement exist between those pipes  38  and the shroud  50 .  FIG. 13  is a cross-sectional view illustrating an active state of the spraybar  28  taken at a similar location to that shown in  FIG. 12  except the welded together pipes  38  are slightly separated from the shroud  50 .  
         [0061]     As intimated above, the described embodiments of the present invention are disclosed for illustration purposes of exemplary implementations of the unique afterburner fuel-feed arrangement  26 . It should be appreciated, however, that these examples are in no way limiting with respect to the afforded patent protection which is defined by the following patented claims.