Abstract:
An injector assembly includes a barrel-shaped housing and an injector, the injector including a feed ring formed of multiple, etched, T-shaped plates. A plurality of nozzles are arranged in an evenly-spaced array around the injector and direct fluid radially inward into the central annulus of the injector assembly. The injector includes an air inlet port with an internal feed passage fluidly connected to swirl chambers and exit orifices to provide individual sprays of fuel from the nozzles. Integral air swirlers impart a swirling component of motion to the fuel sprays. A venturi configuration is provided by the housing. The nozzles are provided along the venturi configuration, which maintains fluid separation from the walls of the housing downstream from the venturi.

Description:
CROSS-REFERENCE TO RELATED CASES 
   The present application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/487,092; filed Jul. 14, 2003 and U.S. Provisional Ser. No. 60/498,626; filed Aug. 28, 2003, the disclosures of which are expressly incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates in general to injectors for dispensing fluids in fine sprays, and more particularly relates to fuel injectors for dispensing liquid fuel in fine sprays for ignition in gas turbine engines. 
   DESCRIPTION OF THE PRIOR ART 
   The art of producing sprays of liquid is extensive. Many injectors have a nozzle with a swirl chamber. One or more angled inlet slots direct the fluid to be sprayed into the swirl chamber. The inlet slots cause the fluid to create a vortex in the swirl chamber adjacent to a spray orifice. The fluid then exits through the spray orifice in a conical spray. Patents showing such injectors include U.S. Pat. Nos. 4,613,079 and 4,134,606. 
   In the combustion of fuels, a nozzle that provides a spray of fine droplets improves the efficiency of combustion and reduces the production of undesirable air pollutants. In some applications, it is desirable to have very low Flow Numbers and Flow Numbers that vary from location to location. The “Flow Number” relates the rate of fluid flow output to the applied inlet pressure. Flow Numbers that are less than 1.0 lb/hr.psi 0.5 , and even as small as 0.1 lb/hr.psi 0.5 , are desirable in some applications. This corresponds to swirl chambers less than 1.905 mm (0.075 inches); and exit orifices of less than 0.3048 mm (0.012 inches) diameter. 
   It is believed that for many years it was only possible to manufacture many of the openings and surfaces of small nozzles to create such low Flow Numbers by using relatively low volume machine tool and hand tool operations in connection with high magnification and examination techniques. This was a labor-intensive process with a high rejection or scrap rate. 
   One technique which has overcome this problem and produces spray nozzles having Flow Numbers as low as 0.1 lb/hr.psi 0.5  is described and illustrated in U.S. Pat. No. 5,435,884. In this patent, which is owned by the assignee of the present application, a nozzle having a small swirl chamber, exit orifice and feed slots is provided that produces a fine droplet spray. The swirl chamber, exit orifice and feed slots are formed by chemical etching the surfaces of one or more thin metal plates. The etching produces a nozzle with very streamlined geometries thereby resulting in significant reductions in pressure losses and enhanced spray performance. The chemical etching process is easily repeatable and highly accurate, and can produce multiple nozzles for individual or simultaneous use. 
   The nozzle shown and described in the &#39;884 patent has many advantages over the prior art, mechanically-formed nozzles, and has received acceptance in the marketplace. The nozzle has design features that allow it to be integrated into an affordable multi-point fuel injection scheme. One particular application for such a nozzle is described in U.S. Pat. No. 6,550,696, also owned by the assignee of the present invention, where an integral air swirler, provided in one or more etched plates of the injector, is combined with the nozzle allowing the introduction of fuel sprays into an air flow. By premixing the fuel and air, a homogeneous fuel-air mixture is achieved, localized regions of near stoichiometric fuel-air mixtures are avoided, and a reduction in Nitrous Oxide (NOx) and Carbon Monoxide (CO) emissions can be realized. 
   The injector described in the &#39;696 patent achieves some fundamental advantages, and has a plurality of nozzles arranged in a matrix across the surface of the injector, with the nozzles oriented to provide sprays of fuel in the axial (downstream) direction. 
   A similar arrangement is shown in U.S. Pat. No. 6,311,473, where the axial sprays are arranged in an annular configuration in a single plane, and outwardly bounded by an annular sheet of air, to avoid impinging on the downstream walls of the housing. Downstream radial air swirlers are also provided to facilitate vaporization of the fuel. 
   Certain applications require the use of radial, rather than axial-directed nozzles. Such an arrangement can provide some advantages. It is known to provide an injector comprising a plurality of plates with etched passages, where the plates have a T-shaped design, and which are then mechanically formed into a cylindrical, ring-shaped configuration, such as shown and described in U.S. Pat. No. 6,321,541, also owned by the assignee of the present invention. The fuel is dispensed radially inward (or outward) through nozzles spaced around the circumferences of the ring. In this application however, air swirlers are not disclosed, which again, can be useful in some application to achieve better overall combustion. 
   It is believed there is a demand for a fuel injector with a nozzle assembly having a cylindrical configuration for gas turbine applications with a plurality of nozzles that are compact and lightweight, and where each nozzle includes integral structure that allows the introduction of air (or another fluid) into or in conjunction with the fuel. It is further believed that there is a demand, particularly for gas turbine applications, for an injector with a feed ring that has a plurality of nozzles with a low Flow Number and integral air swirlers to reduce NOX and CO emissions, improve spray patternization, and provide a fuel spray that is well dispersed for efficient combustion. 
   SUMMARY OF THE INVENTION 
   The present invention provides a novel and unique fuel injector having a cylindrical configuration and a plurality of compact and lightweight nozzles that provide sprays of fine droplets of fuel, and includes integral structure that allows the introduction of air or other fluid into or in conjunction with the fuel. According to one application of the invention, the injector is useful for gas turbine applications and includes a feed ring with a plurality of nozzles spaced around the circumference of the ring, where each nozzle has a low Flow Number, and an integral air swirler that reduces NOX and CO emissions. The nozzles provide good spray patternization and the fuel spray is well dispersed for efficient combustion. In addition, the nozzles can be accurately and repeatably manufactured. 
   According to the present invention, the feed ring of the injector includes a plurality of thin, flat T-shaped plates of etchable material disposed in adjacent, surface-to-surface contact with one another. A plurality of nozzles are formed in a linear, evenly-spaced array along the head nozzle portion (transversely extending arms) of the plates. Each nozzle includes a metering assembly formed in one or more of the plates to provide a fine spray of fuel; and an integral swirler structure formed in one or more of the plates. The swirler structure allows the introduction of air or other fluid into or in conjunction with the fuel spray. 
   The metering assembly preferably includes a bowl-shaped swirl chamber shaped by etching at least one of the plates. Chemical etching, electro-mechanical etching or other appropriate etching technique can be used to form the swirl chamber. A spray orifice, also preferably formed by etching, is in fluid communication with the center of the swirl chamber. At least one feed slot, also preferably formed by etching, is in fluid communication with the swirl chamber and extends in tangential (non-radial) relation thereto. Fuel directed through the feed slot(s) moves in a vortex motion toward the center of the swirl chamber, and then exits the spray orifice in the conical spray of fine droplets. 
   The swirler structure preferably provides a swirling component of motion to the fuel spray. The swirler structure preferably includes a cylindrical swirler passage, also shaped by etching through at least one of the other plates. The cylindrical swirler passage is located in co-axial relation to the spray orifice of the metering set, such that the fuel from the spray orifice passes through the swirler passage. At least one air feed slot, also preferably formed by etching, is provided in fluid communication with the swirler passage and extends in tangential (non-radial) relation thereto. The second fluid (air) is provided through the feed slot and moves in a swirling motion in the swirler passage. The second fluid imparts a swirling component of motion to the fuel as the fuel passes through the swirler passage. The feed slot(s) can be oriented to provide fluid streams in the same direction (co-rotating), or in opposite directions (counter-rotating). In some applications the air feed slots could be purely radial, such that the air is not caused to swirl. 
   Supply passages for the second fluid extend through the plates of the metering set and the swirler structure to the feed slots in each plate of the swirler structure. 
   The plates of the feed ring are fastened together (such as by bonding), and are mechanically formed such that the arms of the ring define a cylinder, with the nozzles preferably oriented to dispense fuel radially inward into the annulus of the injector, although the strip could also be configured to dispense fuel radially outward merely by bending the strip in the opposite direction (or forming the nozzles on the opposite side of the strip). 
   The feed ring is supported within a barrel-shaped housing, which preferably includes an upstream housing portion and a downstream housing portion, each of which has a chamber portion which when the housing portions are assembled together, define a ring chamber for the feed ring. The downstream housing portion includes an inner annular flange that radially inwardly supports the feed ring, and a series of ports to allow fuel to pass from the ring radially inward toward the central axis of the housing. The inner housing flange also includes a venturi configuration, that is, an annular geometry projecting radially-inward toward the central axis of the housing, and causing fuel sprayed out through the ports to remain separated from the downstream walls of the housing to facilitate efficient combustion. The ports are preferably formed along about the axial midpoint of the venturi configuration. 
   Injectors constructed according to the present invention have a cylindrical configuration that is lightweight and compact, and can be used to introduce a second fluid into a fuel spray. In gas turbine applications, the injector can be used to introduce a swirling air flow into a fuel spray to enhance mixing and reduce NOX and CO emissions from the gas turbine engine. The swirling flow also enhances flame stability by generating toroidal recirculation zones that bring combustion products back towards the fuel injection apparatus thereby resulting in a sustained combustion and a stable flame. The swirling flow also provides good spray patternization and the fuel spray is well-dispersed for efficient combustion. 
   Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-section side view of a combustion system for a gas turbine engine, with a fuel injector assembly constructed according to the present invention; 
       FIG. 2  is a cross-sectional end view of the injector assembly, taken substantially along the plane described by the lines  2 — 2  in  FIG. 1 ; 
       FIG. 3  is a cross-sectional side view of the injector assembly of  FIG. 2  with the swirler removed; 
       FIG. 4  is an elevated perspective view of the injector for the injector assembly of  FIG. 3 ; 
       FIG. 5  is an enlarged cross-sectional side view of a portion of the injector assembly of  FIG. 3 ; 
       FIG. 6A  is an elevated perspective view of the manifold plate for the injector of  FIG. 4 ; 
       FIG. 6B  is an elevated plan view of the manifold plate after forming; 
       FIG. 7A  is an elevated perspective view of the distribution plate for the injector; 
       FIG. 7B  is an elevated plan view of the distribution plate after forming; 
       FIG. 8A  is an elevated perspective view of the spin plate for the injector; 
       FIG. 8B  is an elevated plan view of the spin plate after forming; 
       FIG. 9A  is an elevated perspective view of the orifice plate for the injector; 
       FIG. 9B  is an elevated plan view of the orifice plate after forming; 
       FIG. 10A  is an elevated perspective view of the heat shield plate for the injector; 
       FIG. 10B  is an elevated plan view of the heat shield plate after forming; 
       FIG. 11A  is an elevated perspective view of the air swirler plate for the injector; and 
       FIG. 11B  is an elevated plan view of the air swirler plate after forming. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the drawings and initially to  FIG. 1 , a portion of a combustion system for a turbine engine is indicated generally at  20 . The system includes a combustion chamber  22 ; and a fuel injector assembly, indicated generally at  24 , mounted to the upstream end wall  25  of the combustion chamber. The fuel injector assembly  24  atomizes and directs fuel into the combustion chamber  22  for burning, as should be well known to those skilled in the art. Combustion chamber  22  can be any useful type of combustion chamber, such as a combustion chamber for industrial power generation equipment; however, the present invention is believed useful for combustion chambers for other types of combustion applications, such as in ground vehicles, where a fine dispersion of fuel droplets of two fluids (e.g., a liquid fuel and air) is desirable. One particularly useful application for the combustion system of the present invention is in the premixer described in U.S. Pat. No. 6,311,473, owned by the assignee of the present invention and which is incorporated herein by reference. In any case, the combustion chamber will not be described herein for sake of brevity, with the exception that as should be known to those skilled in the art, air is compressed, mixed with the fuel, and directed into the combustion chamber and ignited, so that the expanding gases of combustion can rapidly move across and thus rotate turbine blades (not shown). While a single injector assembly is shown in  FIG. 1 , it should be appreciated that multiple injector assemblies could be used mounted to the combustor. 
   The fuel injector assembly  24  includes a barrel-shaped housing, indicated generally at  30 ; an another air swirler, indicated generally at  32 ; and a fuel injector, indicated generally at  36 . The air swirler  32  preferably comprises an axial swirler having a series of helical vanes  38  for directing air in a swirling manner into the upstream end of the injector assembly. A center body  39  is centrally located in the housing and surrounded by swirler  32 . Center body  39  comprises a pilot nozzle for introducing natural gas or liquid fuel into the fuel injector assembly. The pilot nozzle is useful to stabilize the flow when the fuel injector assembly is used in a lean premix mode, and may not be necessary in every application. In any event, the type of pilot nozzle useful for the particular application can be determined by those skilled in the art. 
   Referring to  FIGS. 2–5 , the fuel injector  36  comprises a feed ring, indicated generally at  67  having an inlet port  68 . The feed ring is preferably formed from relatively thin (e.g., 0.005–0.090 inches thick), flat plates  76 – 81  which are located in adjacent, surface-to-surface contact with each other. As can be seen in  FIGS. 6A–11A , each of the plates  76 – 81  preferably has a T-shaped configuration, and is formed in one piece from a metal sheet of an appropriate material such as INCONEL 600. Each plate can be formed in the required configuration (such as the illustrated T-shape configuration) by durable etching, stamping or die-cutting. While six plates are illustrated and described, it is of course possible that a greater or lesser number of plates could be provided, and that the shape of the individual plates may be other than as illustrated, for example, they could simply be elongated flat strips (i.e., not “T” shaped). 
   As shown in  FIGS. 6A and 6B , the first, manifold plate  76 , has a short feed portion  80  and an elongated head nozzle portion  82 , extending substantially perpendicular to the feed portion  80 . A fuel feed passage is formed on an inner surface  83  of the plate. The feed passage includes an enlarged cavity in the feed portion  80 ; and a pair of thin channels or grooves  85 ,  86 , which are fluidly connected to the cavity  84 , and extend outwardly centrally along each arm of the head nozzle portion in parallel, spaced relation, along substantially the entire length of the opposing arms. The distal ends of the respective channels  85 ,  86  can be fluidly interconnected. 
   Slotted through-passages as at  88  are provided through the head nozzle portion of plate  76 , and extend along the peripheral edge, to allow the passage of air, as will be described below. The number, spacing and dimension of the passages  88  can vary, as will also be described below. 
   A series of elongated slots as at  89  are interposed between the fuel channels  85 ,  86  and the through passages  88 , and define stagnant air gaps for thermal protection. The number, spacing and dimension of slots  89  can also vary, as will be described below. 
   The cavity, grooves, passages and slots in the manifold plate  76  are preferably formed when the plate is flat ( FIG. 6A ). The cavity, grooves, passages and slots can be formed in any appropriate manner, and it is preferred that they be formed by etching, such as chemical etching, electro-mechanical etching or other appropriate etching technique. The etching of such plates should be known to those skilled in the art, and is described for example in Simmons, U.S. Pat. No. 5,435,884, which is hereby incorporated by reference. The etching of the plates allows the forming of very fine, well-defined and complex openings and passages, which provides a hydraulically natural shape for efficient fluid flow. 
   Referring now to  FIGS. 7A ,  7 B, the second, distribution plate  77  is similarly constructed and includes a short feed portion  90  and an elongated head nozzle portion  92 , extending substantially perpendicular to the feed portion  90 . An inlet passage  93  is formed centrally through feed portion  90 . Pairs of spaced-apart fuel distribution through-slots, as at  94 , are formed along the length of the arms of the head nozzle portion  92 . 
   Slotted through-passages as at  98  are provided through the distribution plate  77 , and extend along the peripheral edge, to allow the passage of air, in the same manner as passages  88  in manifold plate  76 . 
   A series of elongated slots as at  99  are interposed between the fuel slots  94  and the through passages  98 , and define stagnant air gaps for thermal protection in the same manner as slots  89  in manifold plate  76 . 
   The passages and slots in the distribution plate  77  are also preferably formed when manifold plate  76  is flat, in the same manner as described above. When the distribution plate  77  is located adjacent, surface-to-surface relation to manifold plate  76 , inlet passage  93  in plate  77  is fluidly aligned and communicates with cavity  84  in adjacent manifold plate  76 . Likewise, each fuel distribution slot  94  in plate  77  is fluidly aligned and communicates with a respective fuel channel  85 ,  86  in the adjacent manifold plate  76 . The through-passages  98  and slots  99  in distribution plate  77  are likewise fluidly aligned and communicate with respective passages  88  and slots  89  in the adjacent manifold plate  76  (see  FIG. 4 ). 
   Referring now to  FIGS. 8A and 8B , third, spin plate  78  is similarly constructed and includes a short feed portion  100  and an elongated head nozzle portion  102 , extending substantially perpendicular to the feed portion  100 . An inlet passage  103  is formed centrally through feed portion  100 . Spin chambers as at  104  with non-radial feed slots as at  105 , are formed along the length of the arms of the head nozzle portion  102 , and extend through the plate from one side to the other. 
   Slotted through-passages as at  108  are provided through the spin plate  78 , and extend along the peripheral edge, to allow the passage of air, in the same manner as passages  98  in distribution plate  77 . 
   A series of elongated slots as at  109  are interposed between the swirl chambers  104  and the through passages  108 , and also between adjacent swirl chambers, and define stagnant air gaps for thermal protection in the same manner as slots  99  in distribution plate  77 . 
   The passages and slots in spin plate  78  are also preferably formed when the spin plate  78  is flat, in the same manner as described above. The spin plate  78  is located in adjacent, surface-to-surface relation with distribution plate  77 . When so located, inlet passage  103  in plate  78  is fluidly aligned and communicates with inlet passage  93  in adjacent distribution plate  77 . Each feed slot  105  is fluidly aligned and communicates with the distal end of a respective one of the fuel distribution slots  94  in the adjacent distribution plate  77 . The through-passages  108  and slots  109  in spin plate  78  are likewise fluidly aligned and communicate with respective passages  98  and slots  99  in the adjacent distribution plate  77  (see  FIG. 4 ). 
   Referring now to  FIGS. 9A and 9B , fourth, orifice plate  79  is similarly constructed and includes a short feed portion  110  and an elongated head nozzle portion  112 , extending substantially perpendicular to the feed portion  110 . An inlet passage  113  is formed centrally through feed portion  110 . Small circular orifices as at  115  are formed along the length of the arms of the head nozzle portion  112 , and extend through the plate from one side to the other. 
   Slotted through-passages as at  118  are provided through the orifice plate  79 , and extend along the peripheral edge, to allow the passage of air, in the same manner as passages  108  in spin plate  78 . 
   A series of elongated slots as at  119  are interposed between the orifices  115  and the through passages  118 , and also between adjacent orifices, and define stagnant air gaps for thermal protection in the same manner as slots  109  in spin plate  78 . 
   The orifices, passages and slots in orifice plate  79  are preferably formed when orifice plate  79  is flat, in the same manner as described above. The orifice plate is located in adjacent, surface-to-surface relation with spin plate  78 . When so located, inlet passage  113  in plate  79  is fluidly aligned and communicates with inlet passage  103  in adjacent spin plate  78 . Each orifice  115  is centrally, fluidly aligned and communicates with a respective spin chamber  104  in the adjacent spin plate  78 . The through-passages  118  and slots  119  in orifice plate  79  are likewise fluidly aligned and communicate with respective passages  108  and slots  109  in the adjacent spin plate  78  (see  FIG. 4 ). 
   Referring now to  FIGS. 10A and 10B , fifth, heat shield plate  80  is similarly constructed and includes a short feed portion  120  and an elongated head nozzle portion  122 , extending substantially perpendicular to the feed portion  120 . An inlet passage  123  is formed centrally through feed portion  120 . Circular orifices as at  125 , of a diameter larger than orifices  115  in orifice plate  79 , are formed along the arms of the head nozzle portion  122 , and extend through the plate from one side to the other. 
   Slotted through-passages as at  128  are provided through the heat shield plate  80 , and extend along the peripheral edge, to allow the passage of air, in the same manner as passages  118  in orifice plate  79 . 
   A series of elongated channels or grooves as at  129  are formed on an outer surface  130  of the heat shield plate, and are interposed between the orifices  125  and the through passages  128 , and also between adjacent orifices, and define stagnant air gaps for thermal protection in the same manner as slots  119  in orifice plate  79 . 
   The orifices, passages and channels in heat shield plate  80  are preferably formed when heat shield plate  80  is flat, in the same manner as described above. The heat shield plate is located in adjacent, surface-to-surface contact with orifice plate  79 . When so located, inlet passage  123  is fluidly aligned and communicates with inlet passage  113  in adjacent orifice plate  79 . Each orifice  125  is co-axially, fluidly aligned with a respective orifice  115  in the adjacent orifice plate  79 . The through passages  128  and channels  129  in heat shield plate  80  are likewise fluidly aligned and communicate with respective passages  118  and slots  119  in the adjacent orifice plate  79  (see  FIG. 4 ). 
   Referring now to  FIGS. 11A and 11B , sixth, air swirler plate  81  is similarly constructed and includes a short feed portion  130  and an elongated head nozzle portion  132 , extending substantially perpendicular to the feed portion  130 . An inlet passage  133  is formed centrally through feed portion  130 . Circular orifices as at  135 , of a diameter larger than orifices  125  in heat shield plate  80 , are formed along the length of the arms of the head nozzle portion  132 , and extend through the plate from one side to the other. 
   Slotted channels or grooves as at  138  are provided along the outer surface  139  of air swirler plate  81 , and extend along the peripheral edge, to direct the passage of air across the plate. Non-radial channels or grooves as at  141  fluidly interconnect with channels  138 , and direct the air into orifices  135 . 
   A series of channels as at  141  are also formed on the outer surface of the air swirler plate, and are interposed between the orifices  135  and channels  138  and  140 , and also between adjacent orifices, and define stagnant air gaps for thermal protection. 
   The orifices and channels in the air swirler plate  81  are preferably formed when air swirler plate  81  is flat, in the same manner as described above. The air swirler plate is located in adjacent, surface-to-surface contact with heat shield plate  80 . When so located, inlet passage  133  is fluidly aligned and communicates with inlet passage  123  in adjacent heat shield plate  80 . Each orifice  135  is co-axially, fluidly aligned with a respective orifice  125  in the adjacent heat shield plate  80 . The channels  138  in air swirler plate  81  are likewise fluidly aligned with respective passages  128  in the adjacent heat shield plate  80  (see  FIG. 4 ). 
   After the plates are appropriately formed and stacked as above, the plates  76 – 81  are fixed together in an appropriate manner to form the complete feed ring  67 . It is preferred that the plates are fixed together in surface-to-surface contact with a bonding process such as brazing or diffusion bonding. Such bonding processes are well-know to those skilled in the art, and provide a secure connection between the various plates. A more detailed discussion of such bonding can be found, for example, in U.S. Pat. No. 5,484,977; U.S. Pat. No. 5,479,705; and U.S. Pat. No. 5,038,857, among others. 
   The head nozzle portions of all the plates are then mechanically formed (bent) into an appropriate configuration. As shown in  FIG. 4 , the head portions are illustrated as being formed into a cylindrical or annular configuration, such that manifold plate  76  is the radially outermost plate, and air swirler plate  81  is the radially innermost plate. The bending of the plates can be accomplished using appropriate equipment, for example, a cylindrical mandrel or other appropriately-shaped tool. A gap is preferably provided between the opposing, distal ends of the plates to allow for some thermal growth, however they could also be joined together by an appropriated process such as brazing or welding to form a continuously cylindrical nozzle. It should be noted that the plates could also be formed into shapes other than cylindrical, or even provided without forming, in appropriate applications. 
   The feed portions of the plates are then collectively bent at an angle, and preferably substantially normal to the plates, to create the inlet port  68 . 
   Referring now to  FIGS. 3 and 5 , the injector  36 , after it is assembled as above, is captured and supported within a ring chamber  140  formed in the barrel shaped housing  30 . Housing  30  comprises an upstream annular housing portion  142  and a downstream annular housing portion  144 , each of which includes a portion of the chamber, and which fit closely together to form the entire chamber. Upstream housing portion  142  includes an outer annular flange  146  which outwardly supports the feed ring  67 , and which includes a series of slotted feed passages  150  which are fluidly aligned with and communicate with the air passages  88  in the manifold plate  76  (see  FIG. 4 ) to direct air into the feed strip. 
   The downstream housing portion  144  also includes an annular flange  152 , supporting the radially inner side of the feed ring. A series of openings  154  are formed around flange  152 , having a dimension larger than the openings  135  in air swirler plate  81 , and which are co-axially aligned therewith (see  FIG. 4 ). 
   The housing portions  142 ,  144  are also fixed together in an appropriate manner after the plates are located in the ring chamber, such as by welding or brazing. 
   When the injector is supported within the housing as described above, a series of nozzles as at  200 , are defined around the circumference of the injector assembly (see FIG.  2 ). The nozzles are preferably evenly-spaced around the injector assembly, and the flow channels, slots and passages in each nozzle direct fuel from the feed stem  64  into chamber  84  in plate  76 , where the fuel is directed (circumferentially) out through channels  85 ,  86  in plate  76  ( FIG. 6A ), and then radially inward through distribution slots  94  in plate  77  ( FIG. 7A ). The distribution slots  77  direct the fuel into feed slots  105  in plate  78  ( FIG. 8A ) where the fuel then is directed into swirl chamber  104  in a swirling manner. The fuel then passes radially inward through orifice  115  in the adjacent plate  79  ( FIG. 9A ) and is delivered in a conical spray through orifices  125 ,  135  in adjacent plates  80 ,  81  ( FIGS. 10A ,  11 A). The foregoing defines the metering structure of the injector that meters fuel through the injector. 
   Air is provided through inlet passages  150  in housing  66 , where the air passes through slots  88  in plate  76  ( FIG. 6A ), slots  98  in plate  77  ( FIG. 7A ), slots  108  in plate  78  ( FIG. 8A ), slots  118  in plate  79  ( FIG. 9A ), and slots  128  in plate  80  ( FIG. 10A ), where the air is then directed through channels  139  into non-radial feed channels  140  and into the fuel spray in a swirling manner, where the swirling air imparts a swirling component of motion to the fuel spray to facilitate atomization and uniform mixing. The above structure defines the integral air swirler aspect of the injector. 
   The swirling fuel sprays then pass through openings  154  in the downstream housing portion, and into the air stream passing axially through the housing. 
   While only a single air swirler plate is shown, it is of course possible that multiple plates could be provided, each providing separate levels of swirling air flows to add further components of swirl to the fuel spray. The number, spacing and dimensions of the air passages can also vary depending on the desired air flow to be imported to the fuel sprays. The air passages could also be configured to provide simply axial air flows, so that the air flow would not be swirling. While not as preferred as a swirling air flow, such a configuration may be appropriate in certain applications to provide a sufficiently atomized spray. The number, spacing and dimensions of each nozzle could likewise vary depending on the particular application. 
   The air flow through the plates provides thermal protection for the nozzles. The stagnant air gaps in the interconnecting passages  89  in plate  77  ( FIG. 6A ); passages  99  in plate  78  ( FIG. 7A ); passages  109  in plate  79  ( FIG. 8A ); passages  109  in plate  78  ( FIG. 9   a ); and channels  129  in plate  80  ( FIG. 10B ) likewise provide thermal protection for the nozzles. 
   As should be appreciated, the spray nozzles  200  are provided around the radially-inner surface of the injector assembly in the illustrated embodiment to provide sprays of fuel radially-inward toward the central axis of the assembly. However, by appropriate routing of the fuel passages between the plates, or bending the plates in the opposite direction, the spray nozzles could likewise be formed in the radially-outer surface to direct fuel radially outward from the injector assembly. 
   As apparent in  FIG. 4 , inlet port  68  comprises a tab or flange which is defined when the plates are interfitted together. The inlet port  68  provides a fuel inlet connection to the fuel stem  64 . The inlet port  68  includes aligned and fluidly-connected opening  293  in plate  77  ( FIG. 7B ), opening  103  in plate  78  ( FIG. 8B ), opening  113  in plate  79  ( FIG. 9B ), opening  123  in plate  80  ( FIG. 10B ) and opening  133  in plate  81  ( FIG. 11B ). Port  68  is located in abutting relation to the downstream surface of an annular, radially-enlarged flange  212  of upstream housing portion  142 . A passage  214  is provided through flange  212  from a front nipple  216 , and fluidly interconnects with opening  133  in plate  81 . Nipple  216  is connected to an appropriate source of fuel (not shown). 
   The inner annular flange  152  of the downstream housing portion preferably has a venturi geometry to facilitate the flow of fuel and air through the nozzle assembly. As shown in  FIGS. 3 and 5 , the venturi configuration preferably comprises a radially-inward projecting geometry along the inside surface of one or both housing portions, which causes the fluid (air) flowing therepast to accelerate and converge toward the central axis of the housing. Upon introduction of the fuel through the nozzles, in a radially-inward manner, the accelerated air and venturi configuration cause the sprays to be redirected axially downstream through the housing, past the downstream lip of the downstream housing portion  144 . The venturi geometry of the housing substantially prevents the fuel from wetting the walls of the housing, downstream of the venturi, and thereby detrimentally effecting the atomized sprays. Rather, the sprays somewhat converge toward the central axis of the housing, and then pass downstream from the housing in a fully atomized and well-dispersed spray. 
   It is preferred that the nozzles  200  are located at the axial midpoint of the venturi geometry, however, it is believed they could also be located anywhere from the beginning to the end point of the venturi geometry and have some beneficial effect on the distribution of fuel. 
   As should be appreciated, swirling air is provided downstream through the housing by the axial swirler  32 , and directed past the nozzles. The swirling air flow impacts the fuel sprays along the venturi geometry; while air is also directed into inlet passages  150  ( FIG. 5 ) and then internally of each nozzle to provide a swirl component of motion to each spray. When the swirling fuel spray passes through each nozzle  200 , the fuel is impacted by the air passing downstream through the housing. The fuel/air mixture then passes out through the housing for burning in the combustion chamber. 
   If a pilot nozzle  39  is used, the fuel flow through the pilot and through nozzles  200  can be modulated to enhance combustion stability. 
   Again, while a single injector configuration is shown, such a structure is only for exemplary purposes, and it is possible that multiple injectors could be provided; and each injector could have more or fewer nozzles than illustrated, depending upon the particular application. Likewise, while a radially outer spray from the injector is shown, the spray could likewise be radially inner, or even axially from the end of the nozzle. 
   While nozzles  200  are pressure swirl atomizers for providing a hollow conical air atomized fuel spray, it should be appreciated that other nozzle designs could alternatively (or in addition) be used with the present invention to provide other spray geometries, such as plain jet, solid cone, flat spray, etc. Also, while identical round spray orifices  115  are shown in fuel swirler plate  79  ( FIG. 9A ), it should be appreciated that the dimensions and geometries of the orifices may vary across the plate, to tailor the fuel spray volume to a particular application. This can be easily accomplished by the aforementioned etching process. 
   It has been found that the air enhances mixing and reduces NOX and CO emissions from the gas turbine engine, and reduces flame blowout. The metering set and integral swirler structure also provide good spray patternization and the spray is well-dispersed for efficient combustion. The nozzles can also be accurately and repeatably manufactured. 
   The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein should not, however, be construed as limited to the particular form described as it is to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims.