Abstract:
In a fuel injector assembly, for an internal combustion engine, a curved outer housing, fixed at one end, fully encloses a curved flexible fuel feed member, affixed to the housing inlet end and has a nozzle assembly operatively connected to an inner end, wherein the improvement comprises that the housing inlet includes at least one first shaped surface portion, and the nozzle assembly includes a movable nozzle spray-tip having another shaped surface portion that mates conformingly with and is in contact with the at least one shaped surface portion, resulting in relative motion therebetween upon operation of this engine, as a result of the thermal differential arising due to the differing temperatures of the housing and feed member.

Description:
RELATED CASE 
   This application claims the priority of U.S. Provisional Application Ser. No. 60/428,327, filed Nov. 21, 2002, the disclosure of which is expressly incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention generally relates to fuel injectors, and more particularly, to fuel injectors having a flexible feed and movable nozzle spray-tip, useful for internal combustion engines, such as gas turbines. 
   BACKGROUND OF THE INVENTION 
   Fuel injector assemblies are useful for such applications such as gas turbine combustion engines for directing pressurized fuel from a manifold to one or more combustion chambers. Such assemblies also function to prepare the fuel for mixing with air prior to combustion. Each injector assembly typically has an inlet fitting connected to the manifold, a tubular extension or stem connected at one end to the fitting in a typically cantilevered fashion, and one or more spray nozzles connected to the other end of the stem or housing for directing the fuel into the combustion chamber. A single or multiple fuel feed (e.g., a cylindrical tubing or a MacroLaminate structure) circuits extend through the housing to supply fuel from the inlet fitting to the nozzle or nozzle assembly. Appropriate valves and/or flow dividers can be provided to direct and control the fuel flow through the nozzle. The fuel provided by the injector(s) is mixed with air and ignited so that the expanding gases of combustion can, for example, move rapidly across and rotate turbine blades in the gas turbine engine to provide power, for example, to an aircraft. Further discussion of a multi-layered feed strip and the technique for making same are set forth in U.S. Pat. No. 6,321,541 B1 to Wrubel et al. which is also owned by the assignee of this invention and which is also incorporated herein by reference. 
   In typical fuel injector assembly constructions, the fuel feed is fixedly attached at its inlet end and at its outlet end to the inlet fitting and nozzle, respectively, and generally includes a coiled or convoluted portion which is designed to absorb the mechanical stresses generated by the differences in thermal expansion of the internal nozzle component parts and the external nozzle component parts during engine combustion and shut-down. In addition, the fuel nozzle is fixedly and unyieldingly mounted to the inner end of the stem or housing. Due to the insulating air space between the housing and the fuel feed, the housing grows or expands to a much greater extent than the relatively cooler fuel feed which is enveloped by the former. 
   At elevated temperatures, the generally “L” or mirror-image J-shaped housing generally expands over the length of the long, vertical portion of the “L”. However, since the fuel feed remains relatively cool, with reference to the surrounding housing, the fuel feed is pulled or stretched, by the housing, with the thermal differential therebetween being largely compensated by movement of the fuel feed over the short, horizontal leg portion of the “L”. 
   The unsolved problem with the noted prior art construction is that if the nozzle tip is unyieldingly, rigidly attached to the housing, the occurring high stresses are maximized at a transition zone between the fuel feed inner end and the adjoining nozzle end, which can result in early low cycle fatigue failure of this assembly in the general area of the noted transition zone. 
   Attempted prior art solutions have been directed to self-aligning fuel nozzle assemblies of the type set forth in U.S. Pat. No. 4,454,711 to Ben-Porat, wherein the self-aligning fuel nozzle is described as reducing the development of local stresses between a turbine engine swirler member and the fuel nozzle so that wear between these parts is reduced. The Ben-Porat device is basically designed to maintain the proper alignment of the swirler and fuel nozzle for any displacement of the combustor liner relative to the combustor housing during the operation of an aircraft engine, as well as for improving engine fuel efficiency by compensating for relative movement between a liner and a combustor in six degrees of freedom. Thus, the Ben-Porat device attempts to not only solve a different problem but also the proposed structural solution, as best seen in  FIG. 2  thereof, is much more mechanically complex as well as much more expensive in comparison with the present invention. 
   Another known construction utilizes a sliding, reciprocal, translational straight-line movement between the injector nozzle and the housing and/or shroud. However, this construction can be susceptible to excessive translational movement thereof, which in turn introduces another set of problems. 
   SUMMARY OF THE INVENTION 
   Accordingly, in order to overcome the deficiencies of prior art devices, the present invention provides a device or structure for permitting relative movement between a movable nozzle tip and the adjoining housing end, which has the net effect of safely transferring the noted high stresses to the large radius bend area of the generally L-shaped flexible fuel feed. 
   Specifically, in a fuel injector assembly, for dispensing fuel in the combustion chamber of a gas turbine engine, having a contoured outer housing, attached on one end to an engine casing, fully enveloping a contoured flexible fuel feed, fixedly attached at one end thereof to a housing inlet and having a nozzle assembly operatively connected therewith at another end, attached at a housing outlet end, the fuel feed being otherwise separated from the housing by a peripheral insulating space, the improvement comprises the housing outlet end having a first contoured surface portion, and the nozzle assembly including a movable nozzle spray-tip having a second contoured surface portion in complementary mating engagement with the housing first contoured surface portion, resulting in sliding relative motion therebetween upon the operation of the gas turbine engine, as a result of the thermal expansion differential arising due to the differing temperatures of housing the said fuel feed. The first and second contoured surface portions can be either interior or exterior surfaces and can be curved. Preferably, each of the contoured surface portions includes at least a portion of a spherical surface component. 
   In a variation thereof, the housing outlet end further includes a shroud, with the shroud including the first contoured surface portion. 
   In a further variation thereof, the contoured surface portions are curved and preferably include a spherical surface component. 
   In another variation thereof, the housing outlet end further includes an adaptor member, interposed between the housing outlet end and the shroud, the adaptor member including a further contoured surface portion, with the nozzle spray-tip exterior surface portion being in complementary mating engagement with both of the first and further contoured surface portions, the first and further contoured surface portions also being axially movable relative to each other, and each of the contoured surface portions including at least a portion of a spherical surface component. 
   In another embodiment of this invention, in a fuel injector assembly, for dispensing fuel in the combustion chamber of a gas turbine engine, having a shaped outer housing, attached at one end to an engine casing, fully enveloping a shaped flexible fuel feed line, affixed at one end thereof to a housing inlet and having a nozzle assembly operatively connected therewith at another end, affixed to a housing outlet end via a shroud and an intermediate adaptor member, the fuel feed line being otherwise separated from the housing by a surrounding insulating, closed, space, the improvement comprising the shroud and the adaptor member both including spaced first and second contoured surface portions, respectively, and the nozzle assembly including a movable, elastically deformable, nozzle spray-tip, having a third contoured surface portion mating with both the first and second contoured surface portions, resulting in pivotal relative motion therebetween upon the operation of the gas turbine engine, as a result of the thermal expansion differential arising from the differing temperatures of the housing and the fuel feed line. Preferably, each of the contoured surface portions are curved and include at least a portion of a spherical surface component, with the first and second spherical surface components also being axially movable relative to each other. 
   A differing embodiment of this invention pertains to an improved fuel injector assembly, for use in an internal combustion engine, including a curved outer housing, fixedly retained on one end at an engine casing, fully enclosing a curved flexible fuel feed member, the flexible feed member being affixed at an outer end to a housing inlet end and having a nozzle assembly operatively connected therewith at an inner end thereof, the nozzle assembly being yieldingly attached at a housing outlet end, with the fuel feed member being otherwise spaced from the housing via a peripheral insulating space, the improvement comprising the housing outlet end including at least one shaped surface portion, and the nozzle assembly including a movable nozzle spray-tip having another shaped surface portion complementarily matingly conforming with and being in contact with the at least one shaped surface portion, resulting in relative motion therebetween upon the operation of the internal combustion engine, as a result of the thermal expansion differential arising due to the differing temperatures of the housing and the fuel feed member. Preferably, each of the shaped surface portions is at least partially curved, with the at least one curved surface portion being interior surface portions and the other curved surface portion being an exterior surface portion. 
   In a variation thereof, each of the curved surface portions includes at least a portion of a spherical surface component with the at least one spherical surface component being interior surface components and the other spherical surface component being an exterior surface component. Preferably, the at least one curved surface portion includes a second curved surface portion, with the at least one and second curved surface portions also being axially movable relative to each other. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is schematic and greatly simplified cross-sectional side view of a gas turbine engine combustion chamber, utilizing fuel injector assemblies constructed according to the principles of the present invention. 
       FIGS. 2   a  and  2   b  are schematic showings of a simplified fuel injector assembly having a curvilinearly movable nozzle spray-tip, shown at ambient (cold) and operating (hot) conditions, respectively. 
       FIG. 3  is an enlarged, simplified showing of a construction of an adjoining fuel nozzle tip and nozzle shroud, of the type shown in  FIG. 2 , that permits swiveling movement therebetween. 
       FIG. 4  is a schematic showing, in vertical cross section, of a fuel feed and housing portion of a fuel injector assembly incorporating a movable nozzle spray-tip of the type shown in  FIG. 2 . 
       FIG. 5  is an enlarged schematic showing of the fuel feed large radius bend and the nozzle spray-tip of  FIG. 4 . 
       FIG. 6  is a schematic showing, similar to that of  FIG. 3 , utilizing another embodiment of a construction that permits relative movement between an adjoining fuel nozzle spray-tip and a nozzle shroud. 
       FIG. 7  is a schematic showing of another cylindrical nozzle spray-tip and pivot pin construction similar to that of  FIG. 6 . 
       FIG. 7A  is a transverse, schematic, cross-sectional view of the  FIG. 7  nozzle construction, taken through the spray tip at the pivot pin line centers of rotation, showing opposed inwardly-directed pivot pin members on one component thereof. 
       FIG. 7B  is a view, similar to that of  FIG. 7A , but showing the use of opposed pin members with the rotational interface of the pivot members on another of the components thereof. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, and initially to  FIG. 1 , a schematic and simplified portion of a gas turbine engine is indicated generally at  10 . The upstream, front wall of a combustion chamber for the engine is shown at  12 , and a plurality of fuel injector-assemblies, for example, as indicated generally at  20 , constructed according to the present invention, are shown mounted within chamber  12 . Combustion chamber  12  is a typical combustion chamber for aircraft applications, and will not be discussed further for the sake of brevity. The fuel injector assemblies  20  atomize and direct fuel into combustion chamber  12  for ignition. A compressor (not shown) is mounted upstream of the fuel injectors and provides pressurized air at elevated temperatures in combustion chamber  12  to facilitate the ignition. The air is typically provided at highly elevated temperatures, which can reach over 1000 degrees F. in aircraft applications. 
   While fuel injector assemblies  20  of the present invention are particularly useful in gas turbine engines for aircraft, these fuel injector assemblies are also deemed to be useful in other types of applications, such as in industrial power generating equipment and in marine propulsion applications. 
   Turning now particularly to  FIGS. 2   a  and  2   b , there are illustrated, in simplified schematic showings, a fuel injector assembly  20  comprised of a generally L-shaped housing  22 , having an attachment flange  26  at an upper end portion  24  thereof, and a nozzle assembly including a nozzle tip adaptor  31  ( FIG. 4  et al.), having a movable nozzle spray-tip  32 , within a shroud  30 , attached at a lower housing end portion  28  thereof. Located within housing  22 , surrounded by a generally cylindrical, insulating space  36 , is a flexible fuel feed  38 , having a large radius bend  40 , of any desired construction, such as cylindrically tubular or macrolaminated, for example. A typical hybrid atomizing nozzle is set forth in prior art U.S. Pat. No. 6,547,163 B1, which is also assigned to the assignee of the present invention and is incorporated herein by reference. 
   As better seen in  FIGS. 4 and 5 , fuel feed  38  includes a fuel inlet  42  and is affixed, such as by welding or brazing, to housing  22  at housing end portion  24 . Flange  26  is removably attached to engine case  44  ( FIG. 1 ). An inner end portion  39  of fuel feed  38  is affixed to an inner end  34  of nozzle tip adaptor  31  and forms a portion of a transition zone  46  from fuel feed  38  to adaptor  31  via inner ends  39  and  34  thereof, respectively. 
   Returning now to  FIGS. 2   a ,  2   b  and  3 ,  FIG. 2   a  illustrates assembly  20  at an ambient or cold condition, while  FIG. 2   b  illustrates assembly  20  at an elevated or hot operating condition. In the hot operating condition, the outer surface of nozzle assembly  20  is exposed to temperatures in the general range of about 1000 to 1200 degrees F., while the temperature of internal fuel feed  38  reaches the general range of about 200 to 300 degrees F. As the result of known thermal expansion, housing  22  grows or expands, as best seen in  FIG. 2   b , relative to  FIG. 2   a.    
   Specifically, as best seen in  FIG. 4 , at an elevated temperature, housing  22  expands over the shown length “L”. Since fuel feed  38  remains relatively cool, with reference to housing  22 , fuel feed  38  is pulled or stretched by housing  22 , with the thermal differential therebetween being largely compensated by movement of fuel feed  38  over shown length “T” in  FIG. 4 . 
   If nozzle spray-tip  32  is unyieldingly, rigidly attached to shroud portion  30  of housing  22 , the resulting unacceptably high stresses are maximized at transition zone  46  between fuel feed inner end  39  and nozzle tip adaptor inner end  34 , which can result in the early low cycle fatigue failure of this assembly in the general area of transition zone  46 . However, if movable nozzle spray-tip  32  and shroud  30  are allowed to move relative to each other, the noted stresses are largely translated to and more readily absorbed or dissipated in large radius bend area  40  of flexible fuel feed  38 . 
   As noted, in order to reduce the stresses in transition zone  46 , relative motion must be permitted between nozzle spray-tip  32  and shroud  30 . One such mechanism includes structures that permit nozzle spray-tip  32  to move via one or more of pivoting, sliding, rotating, reciprocating or combinations of such movements, for example. A schematic version of such a mechanism is illustrated in  FIG. 3  wherein at least an exterior surface portion or “slice” of movable nozzle spray-tip  32  includes a contoured, curvilinear, or curved surface  48 , such as a spherical surface component portion that is received in or cradled in a substantially-corresponding or mating interior contoured or curved surface portion  50  of shroud  30 . 
   As seen in each of  FIGS. 2   b  and  5 , nozzle spray-tip  32  can move or pivot, etc., around an axis  52 , perpendicular to the plane of the paper on which  FIG. 3  is illustrated. It should of course be understood that shroud  30  could move relative to nozzle spray-tip  32  and that such members can move relative to each other. The important concept here is that the mechanisms be structured so as to permit relative movement between shroud  30  and movable nozzle spray-tip  32 . 
   Turning now specifically to  FIG. 5 , fixedly interposed, in this embodiment of the invention, between housing lower end  28  and an inner end  35  of shroud  30 , is an adaptor member  54  whose outer end section  56 , extending beyond shroud inner end  35 , includes an interior contoured or curved surface portion  58 . The shape or contour of portion  58  substantially corresponds to that of movable nozzle spray-tip exterior contoured or curved surface portion  48 , with the former also being substantially similar in shape or contour to that of shroud interior curved surface portion  50 . It should be clear from a perusal of  FIG. 5  that nozzle exterior contoured surface portion  48  is in operative contact with each of stem or housing for directing the fuel into the combustion chamber. A single or multiple fuel feed (e.g., a cylindrical tubing cylindrical tubing or a MacroLaminate structure) circuits extend through the housing to supply fuel from the inlet fitting to the interior contoured surface portions  50  and  58 . Preferably, shroud member  30  is adjustably secured, relative to adaptor member  54 , so as to permit at least initial adjustment of the required clearance and/or fit between shroud  30  and adaptor member  54  so as to enable the desired relative movement for the retention of movable nozzle spray-tip  32  therebetween. 
     FIG. 5  also best illustrates that during engine operation, movable nozzle spray-tip curved surface portion  48  is pulled, as a result of the previously-noted thermal expansion characteristics, against adaptor member curved surface portion  58 , causing movable and resilient nozzle spray-tip  32  to be rotated downwardly from horizontal plane  51  ( FIG. 4 ). Calculations for one specific nozzle assembly configuration have shown that the resulting angle of rotation, inclination or deflection (not shown per se), about axis  52 , to be about 1 or 2 degrees. Once such an angle of inclination has been determined, be it empirically or via actual experimentation, the angular relationships between shroud  30 , adaptor member  54  and movable nozzle spray-tip  32  can be so controlled, adjusted or set that, when operating under “full power”, movable nozzle spray-tip  32  is preferably substantially centered relative to or concentric, while being slightly off-center relative to or not fully concentric at other than “full-power” operating conditions. Thus, the relative movement and/or deflection between shroud  30  and movable nozzle spray-tip  32  reduces the stress, in nozzle assembly  20 , in the area of transition zone  46 , between nozzle  31  and shroud  30 , thereby increasing the fatigue life of this assembly. 
   Turning now to  FIGS. 6 and 7 , there are shown simplified fuel injector assemblies  20 ′ and  20 ″, respectively, which, except for shroud  30 ′, nozzle tip adaptors  31 ′ and movable nozzle spray-tip  32 ′, are substantially similar to previously described fuel injector assembly  20  shown in  FIGS. 2–5 . The same reference numerals apply for like components, with the corresponding components bearing an affixed prime symbol. 
   Fuel injector assembly  20 ′ differs from fuel injector assembly  20  mainly in that the former does not utilize a spherical nozzle tip construction. Rather, movable nozzle spray-tip  32 ′ is preferably substantially cylindrical, or even frustoconical if desired, in shape and of a maximum body diameter slightly less than the smallest inside diameter of shroud  30 ′ so that nozzle spray-tip  32 ′ can have a tilting or pivoting-type movement relative to shroud  30 ′. This is accomplished in the  FIG. 6  embodiment via two diametrically opposed pivot pin members  66  (only one shown) extending radially inwardly through a apertures  68 , in shroud  30 ′, into recesses  72  in nozzle spray-tip  32 ′. At least one pivot pin member  66 , as illustrated in  FIG. 7 , is utilized, although the use of two diametrically opposed pin members  66  ( FIG. 6 ) is preferred. While the inner end  72  of pin member  66  is shown as being hemispherical and located in a complementary surface in movable nozzle spray-tip  32 ′, pin  72  can also be generally cylindrical or even frustoconical if so desired. It should be understood that movable nozzle spray-tip  32 ′ can pivot or tilt slightly, via the at least one pivot pin member  66 , so as to permit the relative movement and/or deflection between shroud  30 ′ and movable nozzle spray-tip  32 ′. 
   In addition, a construction essentially the reverse of assembly  20 ″ can also be utilized in that, instead of using one or more inwardly-directed pivot pin members  66 , movable nozzle spray-tip  32 ′ can be provided with at least one radially outwardly directed pivot member akin to member  66 , the outer end of which is received within a complementary surface in the inner peripheral surface of shroud  30 ′. Again, the pin outer end can be hemispherical and/or cylindrical or the like. In such a construction, in order to permit assembly thereof, shroud  30 ′ is preferably split into two semi-cylindrical shells. 
   Specifically, the construction of nozzle  20 ″, shown in  FIG. 7A , represents a transverse, schematic, cross sectional view of the  FIG. 7  construction, taken through spray tip  32 ′ at the center line of pivot pins  66 . In the  FIG. 7B  construction of nozzle assembly  20 ″′, even though opposed pin members  66  are similarly outwardly directed as in  Fig. 7A , pin members  66  are fixedly received in spray tip  32 ′, thereby shifting the rotational interface to shroud  30 Δ, while, in Fig,  7 A, the rotational interface remains with nozzle tip  32 ′. In the  FIG. 7B  construction, in order to facilitate the assembly of spray tip  32 ″, shroud  30 ′ of  FIG. 7A  may be split into two semi- cylindrical shell portions  30 ″(only one being shown) abutting at pin members  66 , each shell portion having opposed cylindrical cutouts in order to accommodate pin members  66 . Thus, the  FIG. 7B  construction is essentially the reverse of the  FIG. 7A  nozzle construction. 
   While there are shown and described several presently preferred embodiments of this invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims.