Abstract:
A fuel nozzle apparatus includes: a fuel distributor including an annular distributor ring, an aft interior mounting surface; and a pilot supply tube; a venturi defining a splitter with a first bore, and axially spaced-apart forward and aft exterior mounting surfaces; and a swirler including second bore and a forward interior mounting surface. The pilot supply tube is received in the second bore, outer ends of the inner vanes are received in the first bore; and the forward and aft exterior mounting surfaces of the venturi are received in the forward and aft interior mounting surfaces, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Divisional application of U.S. patent application Ser. No. 12/412,512, filed Mar. 27, 2009, currently pending, which is herein incorporated by reference in its entirety, and which claims the benefit of U.S. Provisional Application Ser. No. 61/044,116, filed Apr. 11, 2008, which is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates generally to fuel nozzles, and more specifically fuel nozzle assemblies having unitary components coupled using brazing for use in gas turbine engines. 
         [0003]    Turbine engines typically include a plurality of fuel nozzles for supplying fuel to the combustor in the engine. The fuel is introduced at the front end of a burner in a highly atomized spray from a fuel nozzle. Compressed air flows around the fuel nozzle and mixes with the fuel to form a fuel-air mixture, which is ignited by the burner. Because of limited fuel pressure availability and a wide range of required fuel flow, many fuel injectors include pilot and main nozzles, with only the pilot nozzles being used during start-up, and both nozzles being used during higher power operation. The flow to the main nozzles is reduced or stopped during start-up and lower power operation. Such injectors can be more efficient and cleaner burning than single nozzle fuel injectors, as the fuel flow can be more accurately controlled and the fuel spray more accurately directed for the particular combustor requirement. The pilot and main nozzles can be contained within the same nozzle assembly or can be supported in separate nozzle assemblies. These dual nozzle fuel injectors can also be constructed to allow further control of the fuel for dual combustors, providing even greater fuel efficiency and reduction of harmful emissions. The temperature of the ignited fuel-air mixture can reach an excess of 3500° F. (1920° C.). It is therefore important that the fuel supply conduits, flow passages and distribution systems are substantially leak free and are protected from the flames and heat. 
         [0004]    Over time, continued exposure to high temperatures during turbine engine operations may induce thermal gradients and stresses in the conduits and fuel nozzle components which may damage the conduits or fuel nozzle components and may adversely affect the operation of the fuel nozzle. For example, thermal gradients may cause fuel flow reductions in the conduits and may lead to excessive fuel maldistribution within the turbine engine. Exposure of fuel flowing through the conduits and orifices in a fuel nozzle to high temperatures may lead to coking of the fuel and lead to blockages and non-uniform flow. To provide low emissions, modern fuel nozzles require numerous, complicated internal air and fuel circuits to create multiple, separate flame zones. Fuel circuits may require heat shields from the internal air to prevent coking, and certain fuel nozzle components may have to be cooled and shielded from combustion gases. Additional features may have to be provided in the fuel nozzle components to promote heat transfer and cooling. Furthermore, over time, continued operation with damaged fuel nozzles may result in decreased turbine efficiency, turbine component distress, and/or reduced engine exhaust gas temperature margin. 
         [0005]    Improving the life cycle of fuel nozzles installed within the turbine engine may extend the longevity of the turbine engine. Known fuel nozzles include a delivery system, a mixing system, and a support system. The delivery system comprising conduits for transporting fluids delivers fuel to the turbine engine and is supported, and is shielded within the turbine engine, by the support system. More specifically, known support systems surround the delivery system, and as such are subjected to higher temperatures and have higher operating temperatures than delivery systems which are cooled by fluid flowing through the fuel nozzle. It may be possible to reduce the thermal stresses in the conduits and fuel nozzles by configuring their external and internal contours and thicknesses. Some known conventional fuel nozzles have 22 braze joints and 3 weld joints. 
         [0006]    Fuel nozzles have swirler assemblies that swirl the air passing through them to promote mixing of air with fuel prior to combustion. The swirler assemblies used in the combustors may be complex structures having axial, radial or conical swirlers or a combination of them. In the past, conventional manufacturing methods have been used to fabricate mixers having separate venturi and swirler components that are assembled or joined together using known methods to form assemblies. For example, in some mixers with complex vanes, individual vanes are first machined and then brazed into an assembly. Investment casting methods have been used in the past in producing some combustor swirlers. Other swirlers and venturis have been machined from raw stock. Electro-discharge machining (EDM) has been used as a means of machining the vanes in conventional fuel nozzle components. 
         [0007]    Conventional gas turbine engine components such as, for example, fuel nozzles and their associated swirlers, conduits, distribution systems, venturis and mixing systems are generally expensive to fabricate and/or repair because the conventional fuel nozzle designs having complex swirlers, conduits and distribution circuits and venturis for transporting, distributing and mixing fuel with air include a complex assembly and joining of more than thirty components. More specifically, the use of braze joints can increase the time needed to fabricate such components and can also complicate the fabrication process for any of several reasons, including: the need for an adequate region to allow for braze alloy placement; the need for minimizing unwanted braze alloy flow; the need for an acceptable inspection technique to verify braze quality; and, the necessity of having several braze alloys available in order to prevent the re-melting of previous braze joints. Moreover, numerous braze joints may result in several braze runs, which may weaken the parent material of the component. Modern fuel nozzles such as the Twin Annular Pre Swirl (TAPS) nozzles have numerous components and braze joints in a tight envelope. The presence of numerous braze joints can undesirably increase the weight and the cost of manufacturing and inspection of the components and assemblies. 
         [0008]    Accordingly, it would be desirable to have a fuel nozzle having unitary components having complex geometries for mixing fuel and air in fuel nozzles while protecting the structures from heat for reducing undesirable effects from thermal exposure described earlier. It is desirable to have a fuel nozzle assembly having assembly features to reduce the cost and for ease of assembly as well as providing protection from adverse thermal environment and for reducing potential leakage. It is desirable to have a method of assembly of unitary components having complex three-dimensional geometries, such as, for example, a distributor, a swirler and a venturi with a heat shield for use in fuel nozzles having reduced potential for leakage in a gas turbine engine. It is desirable to have a method of manufacturing unitary components having complex three-dimensional geometries for use in fuel nozzles. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0009]    The above-mentioned need or needs may be met by exemplary embodiments which provide a fuel nozzle comprising one or more components mutually attached to each other. The fuel nozzle may include at least one unitary component made using a rapid manufacturing process. 
         [0010]    According to one aspect of the invention, fuel nozzle apparatus includes: a fuel distributor having: a fuel conduit; an annular distributor ring including: an array of fuel outlets, a main fuel passage communicating with the fuel conduit and the fuel outlets, and an aft interior mounting surface; and a pilot supply tube extending axially from an inner end of the fuel conduit, and including a pilot fuel passage; a venturi, including: an annular splitter including a cylindrical forward portion with a first bore; an annular venturi wall surrounding the splitter, the venturi including a cylindrical forward portion defining axially spaced-apart forward and aft exterior mounting surfaces; and a row of first vanes extending between the forward portions of the splitter and the venturi wall; a swirler including: a hub with upstream and downstream ends, a second bore at the upstream end, and a pilot fuel outlet at the downstream end; a row of second vanes extending outward from the hub; an annular rim surrounding the upstream end of the hub, defining an air flow passage between the rim and the hub, and a forward interior mounting surface; and a radially-extending wall interconnecting the hub and the rim; wherein: the pilot supply tube is received in the second bore; outer ends of the second vanes are received in the first bore of the splitter; and the forward and aft exterior mounting surfaces of the venturi are received in the forward and aft interior mounting surfaces, respectively. 
         [0011]    According to another aspect of the invention, the swirler further includes a generally annular forward portion disposed forward of the annular rim, the forward portion having a wall section forming a U-shaped slot, and wherein the radially-extending wall is disposed at an intersection of the forward portion and the rim and spans across the U-shaped slot. 
         [0012]    According to another aspect of the invention, the apparatus of further includes: a centerbody having an annular wall surrounding the distributor ring, the annular wall having upstream and downstream ends, and including an array of first openings passing through the annular wall near the upstream end, each of the first openings aligned with one of the fuel outlets. 
         [0013]    According to another aspect of the invention, the annular wall of the centerbody includes one or more circumferential rows of second openings passing through the annular wall near the downstream end. 
         [0014]    According to another aspect of the invention, the venturi wall includes a conical aft portion extending aft from the cylindrical forward portion, and an annular heat shield disposed at an aft end of the conical aft portion. 
         [0015]    According to another aspect of the invention, a radial wall is disposed at an aft end of the centerbody, the radial wall including one or more circumferential rows of holes that are oriented to direct cooling air to impinge on the heat shield. 
         [0016]    According to another aspect of the invention, at least one of the fuel distributor, the venturi, and the fuel swirler is of unitary construction. 
         [0017]    According to another aspect of the invention, the unitary construction is made by a rapid manufacturing process. 
         [0018]    According to another aspect of the invention, the fuel distributor is of unitary construction; the venturi is of unitary construction; the swirler is of unitary construction; and the fuel distributor, the venturi, and the fuel swirler are connected to each other by braze joints. 
         [0019]    According to another aspect of the invention, a fuel nozzle apparatus includes: an annular distributor ring including an internal main fuel passage in fluid communication with an array of fuel posts that define individual fuel outlets; a centerbody having an annular outer wall surrounding the distributor ring, the annular wall having upstream and downstream ends, and including: an array of first openings passing through the annular wall near the upstream end, each of the first openings aligned with one of the fuel posts; and one or more circumferential rows of second openings passing through the annular wall near the downstream end. 
         [0020]    According to another aspect of the invention, the annular outer wall includes a generally cylindrical portion and a radial portion which is disposed at approximately a right angle to the cylindrical portion, at an aft end thereof; an inner edge of the radial portion contacts an aft end of the distributor ring, such that an annular passage for air flow is defined between the outer wall and the distributor ring; and the rows of second openings pass through the cylindrical portion of the outer wall. 
         [0021]    According to another aspect of the invention, 1 to 4 circumferential rows of second openings are provided. 
         [0022]    According to another aspect of the invention, each row includes 60 to 80 second openings. 
         [0023]    According to another aspect of the invention, each second opening has a diameter between 0.020 inches and 0.030 inches. 
         [0024]    According to another aspect of the invention, each second opening is shaped as a diffuser opening with a variable cross sectional area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
           [0026]      FIG. 1  is a diagrammatic view of a high bypass turbofan gas turbine engine comprising an exemplary fuel nozzle according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 2  is an isometric view of an exemplary fuel nozzle according to an exemplary embodiment of the present invention. 
           [0028]      FIG. 3  is a partial cross-sectional view of exemplary fuel nozzle according to an exemplary embodiment of the present invention. 
           [0029]      FIG. 4  is an axial cross sectional view of the tip region of the exemplary fuel nozzle shown in  FIG. 2 . 
           [0030]      FIG. 5  is a flow chart showing an exemplary embodiment of a method for fabricating a unitary component according to an aspect of the present invention. 
           [0031]      FIG. 6 . is a flow chart showing an exemplary embodiment of an aspect of the present invention of a method of assembling a fuel nozzle. 
           [0032]      FIG. 7  is a top plan view of an exemplary fuel swirler having a braze wire with a portion sectioned away. 
           [0033]      FIG. 8  is an axial cross-sectional view of an exemplary primary pilot assembly. 
           [0034]      FIG. 9  is an axial cross-sectional view of an exemplary primary pilot assembly and an exemplary swirler placed on a test fixture. 
           [0035]      FIG. 10  is a schematic view of an X-ray inspection of a primary pilot assembly. 
           [0036]      FIG. 11  is a schematic view of assembling braze wires in a distributor, primary pilot assembly and swirler. 
           [0037]      FIG. 12  is an axial cross sectional view of an exemplary fuel nozzle sub-assembly. 
           [0038]      FIG. 13  is an isometric view of the exemplary fuel nozzle subassembly shown in  FIG. 12 . 
           [0039]      FIG. 14  is a partial axial cross sectional view of the sub-assembly shown in  FIG. 12  inserted in a stem housing. 
           [0040]      FIG. 15  is a partial axial cross sectional view of an outer shell assembled to the sub-assembly shown in  FIG. 14 . 
           [0041]      FIG. 16  is an axial cross sectional view of an exemplary venturi. 
           [0042]      FIG. 17  is a partial cross-sectional view of an exemplary fuel nozzle stem housing and valve housing. 
           [0043]      FIG. 18  is an axial cross-sectional view of the tip assembly area of the exemplary fuel nozzle shown in  FIG. 2  after assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    Referring now to the drawings in detail, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  shows in diagrammatic form an exemplary gas turbine engine  10  (high bypass type) incorporating an exemplary fuel nozzle  100  having unitary components (such as conduit  80 , swirler  200 , distributor  300 , centerbody  450  and venturi  500 , shown in the figures and described herein) used for promoting mixing of air with the fuel in the fuel nozzle  100 . The exemplary gas turbine engine  10  has an axial longitudinal centerline axis  12  therethrough for reference purposes. Engine  10  preferably includes a core gas turbine engine generally identified by numeral  14  and a fan section  16  positioned upstream thereof. Core engine  14  typically includes a generally tubular outer casing  18  that defines an annular inlet  20 . Outer casing  18  further encloses and supports a booster  22  for raising the pressure of the air that enters core engine  14  to a first pressure level. A high pressure, multi-stage, axial-flow compressor  24  receives pressurized air from booster  22  and further increases the pressure of the air. The pressurized air flows to a combustor  26 , where fuel is injected into the pressurized air stream and ignited to raise the temperature and energy level of the pressurized air. The high energy combustion products flow from combustor  26  to a first (high pressure) turbine  28  for driving the high pressure compressor  24  through a first (high pressure) drive shaft  30 , and then to a second (low pressure) turbine  32  for driving booster  22  and fan section  16  through a second (low pressure) drive shaft  34  that is coaxial with first drive shaft  30 . After driving each of turbines  28  and  32 , the combustion products leave core engine  14  through an exhaust nozzle  36  to provide at least a portion of the jet propulsive thrust of the engine  10 . 
         [0045]    Fan section  16  includes a rotatable, axial-flow fan rotor  38  that is surrounded by an annular fan casing  40 . It will be appreciated that fan casing  40  is supported from core engine  14  by a plurality of substantially radially-extending, circumferentially-spaced outlet guide vanes  42 . In this way, fan casing  40  encloses fan rotor  38  and fan rotor blades  44 . Downstream section  46  of fan casing  40  extends over an outer portion of core engine  14  to define a secondary, or bypass, airflow conduit  48  that provides additional jet propulsive thrust. 
         [0046]    From a flow standpoint, it will be appreciated that an initial airflow, represented by arrow  50 , enters gas turbine engine  10  through an inlet  52  to fan casing  40 . Air flow  50  passes through fan blades  44  and splits into a first compressed air flow (represented by arrow  54 ) that moves through conduit  48  and a second compressed air flow (represented by arrow  56 ) which enters booster  22 . 
         [0047]    The pressure of second compressed air flow  56  is increased and enters high pressure compressor  24 , as represented by arrow  58 . After mixing with fuel and being combusted in combustor  26 , combustion products  60  exit combustor  26  and flow through first turbine  28 . Combustion products  60  then flow through second turbine  32  and exit exhaust nozzle  36  to provide at least a portion of the thrust for gas turbine engine  10 . 
         [0048]    The combustor  26  includes an annular combustion chamber  62  that is coaxial with longitudinal centerline axis  12 , as well as an inlet  64  and an outlet  66 . As noted above, combustor  26  receives an annular stream of pressurized air from a high pressure compressor discharge outlet  69 . A portion of this compressor discharge air (“CDP” air) identified by the numeral  190  in the figures herein, flows into a mixer (not shown). Fuel is injected from a fuel nozzle tip assembly  68  to mix with the air and form a fuel-air mixture that is provided to combustion chamber  62  for combustion. Ignition of the fuel-air mixture is accomplished by a suitable igniter, and the resulting combustion gases  60  flow in an axial direction toward and into an annular, first stage turbine nozzle  72 . Nozzle  72  is defined by an annular flow channel that includes a plurality of radially-extending, circumferentially-spaced nozzle vanes  74  that turn the gases so that they flow angularly and impinge upon the first stage turbine blades of first turbine  28 . As shown in  FIG. 1 , first turbine  28  preferably rotates high pressure compressor  24  via first drive shaft  30 . Low pressure turbine  32  preferably drives booster  24  and fan rotor  38  via second drive shaft  34 . 
         [0049]    Combustion chamber  62  is housed within engine outer casing  18 . Fuel is supplied into the combustion chamber by fuel nozzles  100 , such as for example shown in  FIGS. 2 and 3 . Liquid fuel is transported through conduits  80  within a stem  83 , such as, for example, shown in  FIG. 3 , to the fuel nozzle tip assembly  68 . Conduits that have a unitary construction may be used for transporting the liquid fuel into the fuel nozzle tip assembly  68  of the fuel nozzles  100 . The fuel supply conduits, may be located within the stem  83  and coupled to a fuel distributor tip  180 . Pilot fuel and main fuel are sprayed into the combustor  26  by fuel nozzle tip assemblies  68 , such as for example, shown in  FIGS. 2 ,  3  and  4 . During operation of the turbine engine, initially, pilot fuel is supplied through a pilot fuel flow passage, such as, for example, shown as items  82 ,  84  in  FIG. 3 , during pre-determined engine operation conditions, such as during startup and idle operations. The pilot fuel is discharged from fuel distributor tip  180  through the pilot fuel outlet  162 . When additional power is demanded, main fuel is supplied through main fuel passageways  85  (see  FIG. 3 ) and the main fuel is sprayed using the main fuel outlets  165 . 
         [0050]      FIG. 3  is a partial cross-sectional isometric view of an exemplary fuel nozzle  100  having a unitary conduit  85  used for transporting liquid fuel in a fuel nozzle tip  68 . In the exemplary embodiment, the unitary conduit  80  includes a flow passage  86  located within the conduit body  87  which serves as the main fuel passageway into the fuel nozzle, and a pilot fuel passages  82 ,  84  extending within the conduit body  87 . Fuel from the pilot fuel passages is directed into the fuel nozzle tip  68  by a pilot supply tube  154  (see  FIG. 3 ) and exits through a pilot fuel outlet  162 . In some unitary conduits  80 , it is advantageous to have a flow passage  86  that branches into two or more sub-passages  88 ,  89 , such as, shown for example, in  FIG. 3 . As shown in  FIG. 3  for a fuel nozzle  100  application of the unitary conduit  80 , the flow passage  86  branches into a first main passage  88  and a second main passage  89 . Liquid fuel is supplied into the nozzle through a main passage inlet  126  and enters the flow passage  86 . The fuel flow then branches into the two streams, one through the first main passage  88  and the other through the second main passage  89 , before entering the distributor tip  180 . As shown in  FIG. 3 , the main fuel passageway  86 , the sub-passages  88 ,  89 , and the pilot fuel passageways  82 ,  84  extend in a generally longitudinal direction in the unitary conduit  80 . 
         [0051]    An exemplary fuel distributor  100  having a unitary conduit  80  as described herein and used in a gas turbine engine fuel nozzle is shown in  FIG. 3 . In the exemplary embodiment, a unitary conduit  80  is located within a stem  83  which has a flange  81  for mounting in a gas turbine engine  10 . The unitary conduit  80  is located within the stem  83  such that there is a gap  77  between the interior of the stem and the conduit body  80  of the unitary conduit  80 . The gap  77  insulates the unitary conduit  80  from heat and other adverse environmental conditions surrounding the fuel nozzle in gas turbine engines. Additional cooling of the unitary conduit  80  may be accomplished by circulating air in the gap  77 . The unitary conduit  80  is attached to the stem  83  using conventional attachment means such as brazing. Alternatively, the unitary conduit  80  and the stem  83  may be made by rapid manufacturing methods such as for example, direct laser metal sintering, described herein. In the exemplary embodiment of a fuel nozzle  100  shown and described herein, fuel distributor tip  68  extends from the unitary conduit  80  and stem  83  such that main fuel passageways (first main passage  88  and the second main passage  89 ) and the pilot fuel passageways  82 ,  84  are coupled in flow communication with a fuel distributor  300 , such as, for example, shown in  FIG. 3 . Specifically, main fuel passageways  88 ,  89  are coupled in flow communication to main fuel circuits defined within fuel distributor  300 . Likewise, primary pilot passage  82  and secondary pilot passage  84  are coupled in flow communication with corresponding pilot injectors (see, for example, items  163 ,  164  shown in  FIG. 4 ) positioned radially inward within a fuel nozzle. It will be apparent to those skilled in the art that, although the conduit  80  and the distributor ring  171  have been described herein above as a unitary conduit (i.e., having a unitary construction), it is possible to use conduits  80  having other suitable manufacturing constructs using methods known in the art. The unitary distributor ring  171  is attached to the stem  83  using conventional attachment means such as brazing. Alternatively, the unitary distributor ring  171  and the stem  83  may be made by rapid manufacturing methods such as for example, direct laser metal sintering, described herein. 
         [0052]      FIG. 4  shows an axial cross-sectional view of the exemplary fuel nozzle tip assembly  68  of the exemplary fuel nozzle  100  shown in  FIGS. 1 ,  2  and  3 . The exemplary nozzle tip assembly  68  comprises a distributor  300  which receives the fuel flow from the supply conduit  80 , such as described previously, and distributes the fuel to various locations in the fuel nozzle tip  68 , such as main fuel passages and pilot fuel passages.  FIGS. 3 and 4  show exemplary embodiments of the present invention having two main flow passages  304 ,  305  and two pilot flow passages  102 ,  104  that distribute the fuel in a fuel nozzle tip assembly  68 . 
         [0053]    The exemplary distributor  300  shown in  FIG. 4  comprises a distributor ring body  171  that contains the main flow passages and pilot flow passages described herein. The main flow passages  304 ,  305  in the distributor  300  are in flow communication with corresponding main flow passages (such as, for example, shown as items  88 ,  89  in  FIG. 3 ) in the supply conduit  80 . The exemplary main fuel passages shown and described herein each comprise an inlet portion that transport the fuel flow from the supply conduit  80  to two arcuate portions  304 ,  305  that are located circumferentially around a distributor axis  11 . 
         [0054]    The term “unitary” is used in this application to denote that the associated component, such as, for example, a venturi  500  described herein, is made as a single piece during manufacturing. Thus, a unitary component has a monolithic construction for the component. 
         [0055]      FIG. 4  shows an axial cross section of an exemplary fuel nozzle tip  68  of an exemplary embodiment of the present invention of a fuel nozzle assembly  100 . The exemplary fuel nozzle tip  68  shown in  FIG. 4  has two pilot fuel flow passages, referred to herein as a primary pilot flow passage  102  and a secondary pilot flow passage  104 . Referring to  FIG. 4 , the fuel from the primary pilot flow passage  102  exits the fuel nozzle through a primary pilot fuel injector  163  and the fuel from the secondary pilot flow passage  104  exits the fuel nozzle through a secondary pilot fuel injector  167 . The primary pilot flow passage  102  in the distributor ring  171  is in flow communication with a corresponding pilot primary passage in the supply conduit  80  contained within the stem  83  (see  FIG. 3 ). Similarly, the secondary pilot flow passage  104  in the distributor ring  171  is in flow communication with a corresponding pilot secondary passage in the supply conduit  80  contained within the stem  83 . 
         [0056]    As described previously, fuel nozzles, such as those used in gas turbine engines, are subject to high temperatures. Such exposure to high temperatures may, in some cases, result in fuel coking and blockage in the fuel passages, such as for example, the exit passage  164 . One way to mitigate the fuel coking and/or blockage in the distributor ring  171  is by using heat shields to protect the passages such as items  102 ,  104 ,  105 , shown in  FIG. 4 , from the adverse thermal environment. In the exemplary embodiment shown in  FIG. 3 , the fuel conduits  102 ,  104 ,  105  are protected by gaps  116  and heat shields that at least partially surround these conduits. The gap  116  provides protection to the fuel passages by providing insulation from adverse thermal environment. In the exemplary embodiment shown, the insulation gaps  116  have widths between about 0.015 inches and 0.025 inches. The heat shields, such as those described herein, can be made from any suitable material with ability to withstand high temperature, such as, for example, cobalt based alloys and nickel based alloys commonly used in gas turbine engines. In exemplary embodiment shown in  FIG. 4 , the distributor ring  171  has a unitary construction wherein the distributor ring  171 , the flow passages  102 ,  104 ,  105 , the fuel outlets  165 , the heat shields and the gaps  116  are formed such that they have a monolithic construction made using a DMLS process such as described herein. 
         [0057]      FIG. 4  shows a unitary swirler  200  assembled inside an exemplary fuel nozzle assembly  100  according to an exemplary embodiment of the present invention. The exemplary swirler  200  comprises a body  201  having a hub  205  that extends circumferentially around a swirler axis  11  (alternatively referred to as a nozzle tip axis  11 ). A row of vanes  208  extending from the hub  205  are arranged in a circumferential direction on the hub  205 , around the swirler axis  11 . Each vane  208  has a root portion  210  located radially near the hub  205  and a tip portion  220  that is located radially outward from the hub  205 . Each vane  208  has a leading edge  212  and a trailing edge  214  that extend between the root portion  210  and the tip portion  220 . The vanes  208  have a suitable shape, such as, for example, an airfoil shape, between the leading edge  212  and the trailing edge  214 . Adjacent vanes form a flow passage for passing air, such as the CDP air shown as item  190  in  FIG. 4 , that enters the swirler  200 . The vanes  208  can be inclined both radially and axially relative to the swirler axis  11  to impart a rotational component of motion to the incoming air  190  that enters the swirler  200 . These inclined swirler vanes  208  cause the air  190  to swirl in a generally helical manner within the fuel nozzle tip assembly  68 . In one aspect of the swirler  200 , the vane  208  has a fillet that extends between the root portion  210  and the hub  205  to facilitate a smooth flow of air in the swirler hub region. In the exemplary embodiment shown in  FIGS. 4 and 18  herein, the vanes  208  have a cantilever-type of support, wherein it is structurally supported at its root portion  210  on the hub  205  with the vane tip portion  220  essentially free. It is also possible, in some alternative swirler designs, to provide additional structural support to at least some of the vanes  208  at their tip regions  210 . In another aspect of the swirler  200 , a recess  222  is provided on the tip portion  220  of a vane  228 . During assembly of the fuel nozzle  100 , the recess  222  engages with adjacent components in a fuel nozzle  100  to orient them axially, such as for example, shown in  FIGS. 4 and 18 . 
         [0058]    The exemplary swirler  200  shown in  FIGS. 4 and 18  comprises an adaptor  250  that is located axially aft from the circumferential row of vanes  208 . The adaptor  250  comprises an arcuate wall  256  (see  FIG. 4 ) that forms a flow passage  254  for channeling an air flow  190 , such as for example, the CDP air flow coming out from a compressor discharge in a turbo fan engine  10  (see  FIG. 1 ). The in-coming air  190  enters the passage  254  in the adaptor  250  and flows axially forward towards the row of vanes  208  of the swirler  200 . In one aspect of the present invention, a portion  203  of the swirler body  201  extends axially aft from the hub  205  and forms a portion of the adaptor  250 . In the exemplary embodiment shown in  FIG. 6 , the portion  203  of the body  201  extending axially aft forms a portion of the arcuate wall  256  of the adaptor  250 . The adaptor  250  also serves as a means for mounting the swirler  200  in an assembly, such as a fuel nozzle tip assembly  68 , as shown in  FIG. 4 . In the exemplary embodiment shown in  FIG. 4 , the adaptor  250  comprises an arcuate groove  252  for receiving a brazing material  253  (see  FIG. 13 ) that is used for attaching the adaptor  250  to another structure, such as, for example, a fuel nozzle stem  83  shown in  FIG. 2 . As can be seen clearly in  FIGS. 4 and 13 , the groove  252  in the arcuate wall  256  has a complex three-dimensional geometry that is difficult to form using conventional machining methods. In one aspect of the present invention, the groove  252  in the arcuate wall  256  having a complex three-dimensional geometry, such as shown in the  FIGS. 4 and 13 , is formed integrally to have a unitary construction, using the methods of manufacturing described subsequently herein. 
         [0059]    The exemplary swirler  200  shown in  FIGS. 4 ,  11  and  18  comprises an annular rim  240  that is coaxial with the swirler axis  11  and is located radially outward from the hub  205 . As seen in  FIGS. 4 ,  11  and  18 , the rim  240  engages with adjacent components in the fuel nozzle  100 , and forms a portion of the flow passage for flowing air  190  in the swirler  200 . Airflow  190  enters the aft portion of the swirler  200  in an axially forward direction and is channeled toward the vanes  208  by the hub  205  and rim  240 . In the exemplary embodiment shown in  FIG. 4 , airflow  190 , such as from a compressor discharge, enters the passage  254  in the adaptor  250 . As seen best in  FIGS. 4 and 11 , the axially forward end of the arcuate wall  256  of the adaptor  250  is integrally attached to the rim  240  and the body  201 . In a preferred embodiment, the adaptor  250 , rim  240 , the body  201 , the hub  205  and the vanes  208  have a unitary construction using the methods of manufacture described herein. Alternatively, the adaptor  250  may be manufactured separately and attached to the rim  240  and body  201  using conventional attachment means. 
         [0060]    Referring to  FIG. 4 , a wall  260  extends between a portion of the rim  240  and a portion of the hub  205  the body  201 . The wall  260  provides at least a portion of the structural support between the rim  240  and the hub  205  of the swirler. The wall  260  also ensures that air  190  coming from the adaptor  250  passage  254  into the forward portion of the swirler does not flow in the axially reverse direction and keeps the flow  190  going axially forward toward the vanes  208 . In the exemplary embodiment shown in  FIGS. 4 and 12 , the forward face  262  of the wall  260  is substantially flat with respect to a plane perpendicular to the swirler axis  11 . In order to promote a smooth flow of the air, the edges of the wall  260  are shaped smoothly to avoid abrupt flow separation at sharp edges. 
         [0061]    It is common in combustor and fuel nozzle applications that the compressor discharge air  190  (see  FIGS. 3 and 4 ) coming into the combustor and fuel nozzle regions is very hot, having temperatures above 800 Deg. F. Such high temperature may cause coking or other thermally induced distress for some of the internal components of fuel nozzles  100  such as, for example, the fuel flow passages  102 ,  104 , swirler  200  and venturi  500 . The high temperatures of the air  190  may also weaken the internal braze joints, such as, for example, between the fuel injector  163  and the distributor ring body  171  (see  FIG. 4 ). In one aspect of the present invention, insulation gaps  216  are provided within the body  201  of the swirler  200  to reduce the transfer of heat from the air flowing in the fuel nozzle  100  and its internal components, such as primary fuel injectors  163  or secondary fuel injectors  167 . The insulation gaps, such as items  116  and  216  in  FIG. 4 , help to reduce the temperature at the braze joints in a fuel nozzle assembly during engine operations. The insulation gap  216  may be annular, as shown in  FIG. 4 . Other suitable configurations based on known heat transfer analysis may also be used. In the exemplary embodiment shown in  FIG. 4 , the insulation gap is annular extending at least partially within the swirler body  201 , and has a gap radial width of between about 0.015 inches and 0.025 inches. In one aspect of the present invention, the insulation gap  216  may be formed integrally with the swirler body  201  to have a unitary construction, using the methods of manufacturing described subsequently herein. The integrally formed braze groves, such as those described herein, may have complex contours and enable preformed braze rings such as items  253 ,  353  shown in  FIG. 13  to be installed to promote easy assembly. 
         [0062]    Referring to  FIG. 4 , it is apparent to those skilled in the art that the airflow  190  entering from the adaptor passage  254  is not uniform in the circumferential direction when it enters the vanes  208 . This non-uniformity is further enhanced by the presence of the wall  260 . In conventional swirlers, such nonuniformity of the flow may cause non-uniformities in the mixing of fuel and air and lead to non-uniform combustion temperatures. In one aspect of the present invention of a fuel nozzle  100 , the adverse effects of circumferentially non-uniform flow entry can be minimized by having swirler vanes  208  with geometries that are different from those of circumferentially adjacent vanes. Customized swirler vane  208  geometries can be selected for each circumferential location on the hub  205  based on known fluid flow analytical techniques. A swirler having different geometries for the vanes  208  located at different circumferential locations can have a unitary construction and made using the methods of manufacture described herein. 
         [0063]      FIG. 4  shows an axial cross-sectional view of an exemplary venturi  500  according to an exemplary embodiment of the present invention. The exemplary venturi  500  comprises an annular venturi wall  502  around the swirler axis  11  that forms a mixing cavity  550  wherein a portion of air and fuel are mixed. The annular venturi wall may have any suitable shape in the axial and circumferential directions. A conical shape, such as shown for example in  FIG. 4 , that allows for an expansion of the air/fuel mixture in the axially forward direction is preferred. The exemplary venturi  500  shown in  FIGS. 4 and 16  has an axially forward portion  509  having an axially forward end  501 , and an axially aft portion  511  having an axially aft end  519 . The axially forward portion  509  has a generally cylindrical exterior shape wherein the annular venturi wall  502  is generally cylindrical around the swirler axis  11 . The venturi wall  502  has at least one groove  504  located on its radially exterior side capable of receiving a brazing material during assembly of a nozzle tip assembly  68 . In the exemplary embodiment shown in  FIGS. 4 and 16 , two annular grooves  504 ,  564  are shown, one groove  564  near the axially forward end  501  and another groove  504  near an intermediate location between the axially forward end  501  and the axially aft end  519 . The grooves  504  may be formed using conventional machining methods. Alternatively, the grooves  504  may be formed integrally when the venturi wall  502  is formed, such as, for example, using the methods of manufacturing a unitary venturi  500  as described subsequently herein. In another aspect of the present invention, the venturi  500  comprises a lip  518  (alternatively referred to herein as a drip-lip  518 ) located at the axially aft end  519  of the venturi wall  502 . The drip-lip  518  has a geometry (see  FIG. 16 ) such that liquid fuel particles that flow along the inner surface  503  of the venturi wall  502  separate from the wall  502  and continue to flow axially aft. The drip-lip  518  thus serves to prevent the fuel from flowing radially outwards along the venturi walls at exit. 
         [0064]    As shown in  FIGS. 4 and 16 , the exemplary embodiment of venturi  500  comprises an annular splitter  530  having an annular splitter wall  532  located radially inward from the annular venturi wall  502  and coaxially located with it around the swirler axis  11 . The radially outer surface  533  of the splitter  530  and the radially inner surface  503  of the venturi wall  502  form an annular swirled-air passage  534 . The forward portion of the splitter wall  532  has a recess  535  (see  FIG. 16 ) that facilitates interfacing the venturi  500  with an adjacent component, such as for example, shown as item  208  in  FIG. 4 , during assembly of a fuel nozzle tip assembly  68 . The splitter  530  has a splitter cavity  560  (see  FIG. 16 ) wherein a portion of the air  190  mixes with the fuel ejected from the pilot outlets  162 ,  164  (see  FIG. 4 ). 
         [0065]    The exemplary embodiment of the venturi  500  shown in  FIGS. 4 and 16  comprises a swirler  510 . Although the swirler  510  is shown in  FIG. 5  as being located at the axially forward portion  509  of the venturi  500 , in other alternative embodiments of the present invention, it may be located at other axial locations within the venturi  500 . The swirler  510  comprises a plurality of vanes  508  that extend radially inward between the venturi wall  502  and the annular splitter  530 . The plurality of vanes  508  are arranged in the circumferential direction around the swirler axis  11 . 
         [0066]    Referring to  FIGS. 4 and 16 , in the exemplary embodiment of the swirler  510  shown therein, each vane  508  has a root portion  520  located radially near the splitter  530  and a tip portion  521  that is located radially near the venturi wall  502 . Each vane  508  has a leading edge  512  and a trailing edge  514  that extend between the root portion  520  and the tip portion  521 . The vanes  508  have a suitable shape, such as, for example, an airfoil shape, between the leading edge  512  and the trailing edge  514 . Circumferentially adjacent vanes  508  form a flow passage for passing air, such as the CDP air shown as item  190  in  FIG. 4 , that enters the swirler  510 . The vanes  508  can be inclined both radially and axially relative to the swirler axis  11  to impart a rotational component of motion to the incoming air  190  that enters the swirler  510 . These inclined vanes  508  cause the air  190  to swirl in a generally helical manner within venturi  500 . In one aspect of the present invention, the vane  508  has a fillet  526  that extends between the root portion  520  of the vane  508  and the splitter wall  532 . The fillet  526  facilitates a smooth flow of air within the swirler and in the swirled air passage  534 . The fillet  526  has a smooth contour shape that is designed to promote the smooth flow of air in the swirler. The contour shapes and orientations for a particular vane  508  are designed using known methods of fluid flow analysis. Fillets similar to fillets  526  having suitable fillet contours may also be used between the tip portion  521  of the vane  508  and the venturi wall  502 . In the exemplary embodiment of the venturi  500  shown in  FIGS. 4 and 16  herein, the vanes  508  are supported near both the root portion  520  and the tip portion  521 . It is also possible, in some alternative venturi designs, to have a swirler comprising vanes having a cantilever-type of support, wherein a vane is structurally supported at only one end, with the other end essentially free. The venturi  500  may be manufactured from known materials that can operate in high temperature environments, such as, for example, nickel or cobalt based super alloys, such as CoCr, HS188, N2 and N5. 
         [0067]    The venturi  500  comprises a heat shield  540  for protecting venturi and other components in the fuel nozzle tip assembly  68  (see  FIG. 3 ) from the flames and heat from ignition of the fuel/air mixture in a fuel nozzle  100 . The exemplary heat shield  540  shown in  FIGS. 4 and 16  has an annular shape around the swirler axis  11  and is located axially aft from the swirler  510 , near the axially aft end  519  of the venturi  500 . The heat shield  540  has an annular wall  542  that extends in a radially outward direction from the swirler axis  11 . The annular wall  542  protects venturi  500  and other components in the fuel nozzle  100  from the flames and heat from ignition of the fuel/air mixture, having temperatures in the range of 2500 Deg. F to 4000 Deg. F. The heat shield  540  is made from a suitable material that can withstand high temperatures. Materials such as, for example, CoCr, HS188, N2 and N5 may be used. In the exemplary embodiments shown herein, the heat shield  540  is made from CoCr material, and has a thickness between 0.030 inches and 0.060 inches. It is possible, in other embodiments of the present invention, that the heat shield  540  may be manufactured from a material that is different from the other portions the venturi, such as the venturi wall  502  or the swirler  510 . 
         [0068]    The exemplary venturi  500  shown in  FIGS. 4 and 16  has certain design features that enhance the cooling of the heat shield  540  to reduce its operating temperatures. The exemplary venturi  500  comprises at least one slot  544  extending between the venturi wall  502  and the heat shield  540 . The preferred exemplary embodiment of the venturi  500 , shown in  FIGS. 4 and 16 , comprises a plurality of slots  544  extending between the venturi wall  502  and the heat shield  540  wherein the slots  544  are arranged circumferentially around the swirler axis  11 . The slots  544  provide an exit passage for cooling air that flows through the cavity between the fuel conduit and the venturi wall  502  (See  FIG. 4 ). The cooling air entering the axially oriented portion of each slot  544  is redirected in the radially oriented portion of the slot  544  to exit from the slots  544  in a generally radial direction onto the side of the annular wall  542  of the heat shield. In another aspect of the present invention, the exemplary venturi  500  comprises a plurality of bumps  546  located on the heat shield  540  and arranged circumferentially on the axially forward side of the heat shield wall  542  around the swirler axis  11 . These bumps  546  provide additional heat transfer area and increase the heat transfer from the heat shield  540  to the cooling air directed towards, thereby reducing the operating temperatures of the heat shield  540 . In the exemplary embodiment shown in  FIG. 4 , the bumps  546  are arranged in four circumferential rows, with each row having between 100 and 120 bumps. 
         [0069]    Referring to  FIGS. 4 and 16 , it is apparent to those skilled in the art that a portion of the airflow  190  entering the swirler  510  of the venturi  500 , in some cases, may not be uniform in the circumferential direction when it enters passages between the vanes  508 . This non-uniformity is further enhanced by the presence of other features, such as, for example, the wall  260  (see  FIG. 4 ). In conventional venturis, such non-uniformity of the flow may cause non-uniformities in the mixing of fuel and air in the venturi and lead to non-uniform combustion temperatures. In one aspect of the present invention, the adverse effects of circumferentially non-uniform flow entry can be minimized by having a swirler  510  comprising some swirler vanes  508  with geometries that are different from those of circumferentially adjacent vanes. Customized swirler vane  508  geometries can be selected for each circumferential location based on known fluid flow analytical techniques. A venturi  500  having swirlers with different geometries for the vanes  508  located at different circumferential locations can have a unitary construction and made using the methods of manufacture described herein. 
         [0070]    In the exemplary embodiment of a fuel nozzle  100  shown in  FIG. 14  and  FIG. 18 , the fuel nozzle  100  comprises an annular centerbody  450 . The centerbody  450  comprises an annular outer wall  461  that, in the assembled condition of the fuel nozzle  100  as shown in  FIGS. 2 ,  3 ,  4  and  18 , surround the forward portion of the distributor  300  and forms an annular passage  462  for air flow. As can be seen in  FIG. 18 , the annular outer wall  461  includes a generally cylindrical portion and a radial portion which is disposed at approximately a right angle to the cylindrical portion, at an aft end thereof. An inner edge of the radial portion contacts the aft end of the distributor  300 . A feed air stream for cooling the fuel nozzle  100  enters the air flow passage  412  between the centerbody outer wall  461  and the distributor  300  and flows past the fuel posts  165 , facilitating the cooling of the distributor  300 , centerbody  450  and fuel orifices and fuel posts  165 . The outer wall  461  has a plurality of openings  463  that are arranged in the circumferential direction, corresponding to the orifices in the circumferential row of fuel posts  165 . Fuel ejected from the fuel posts  165  exits from the fuel nozzle  100  through the openings  463 . In the exemplary fuel nozzle  100 , scarfs  452 ,  454  are provided near openings  463  at the main fuel injection sites on the outer side of the centerbody  450  wall  461 , as shown in  FIG. 2 , for fuel purge augmentation. The scarfs are upstream ( 454 ) or downstream ( 452 ) so that the main circuit will actively purge during the modes when the main fuel flow is shut off. In some embodiments, such as shown in  FIGS. 4 and 18 , it is possible to have a small gap  464  between the inner diameter of the outer wall  461  and the outer end of the fuel posts  165 . In the exemplary embodiment shown in  FIGS. 4 and 18 , this gap ranges between about 0.000 inches to about 0.010 inches. 
         [0071]    In the exemplary embodiment shown in  FIGS. 4 and 18 , the centerbody wall  461  is cooled by a multi-hole cooling system which passes a portion of the feed air stream entering the fuel nozzle  100  through one or more circumferential rows of openings  456 . The multi-hole cooling system of the centerbody may typically use one to four rows of openings  456 . The openings  456  may have a substantially constant diameter. Alternatively, the openings  456  may be diffuser openings that have a variable cross sectional area. In the exemplary embodiments shown in  FIGS. 2 ,  4  and  18 , the centerbody  450  has three circumferential rows of openings  456 , each row having between 60 to 80 openings and each opening having a diameter varying between about 0.020 inches and 0.030 inches. As shown in  FIGS. 2 ,  4 , and  8 , the openings  456  can have a complex orientation in the axial, radial and tangential directions within the centerbody outer wall  461 . Additional rows of cooling holes  457  arranged in the circumferential direction in the centerbody wall  461  are provided to direct the cooling air stream toward other parts of the fuel nozzle  100 , such as the venturi  500  heat shield  540 . In the exemplary embodiment shown in  FIGS. 2 ,  4  and  18 , the fuel nozzle  100  comprises an annular heat shield  540  located at one end of the venturi  540 . The heat shield  540  shields the fuel nozzle  100  components from the flame that is formed during combustion in the combustor. The heat shield  540  is cooled by one or more circumferential rows of holes  457  having an axial orientation as shown in  FIGS. 4 and 18  that direct cooling air to impinge on the heat shield  540 . In the exemplary fuel nozzle  100  described herein, the holes  457  typically have a diameter of at least 0.020 inches arranged in a circumferential row having between 50 to 70 holes, with a hole size preferred between about 0.026 inches to about 0.030 inches. The centerbody  450  may be manufactured from known materials that can operate in high temperature environments, such as, for example, nickel or cobalt based super alloys, such as CoCr, HS188, N2 and N5. The cooling holes  456 ,  457  openings  463  and scarfs  452 ,  454  in the centerbody  450  may be made using known manufacturing methods. Alternatively, these features of the centerbody can be made integrally using the manufacturing methods for unitary components described herein, such as, preferably, the DMLS method shown in  FIG. 5  and described herein. In another embodiment of the invention, a heat shield similar to item  540  shown in  FIGS. 4 and 18  may be made integrally to have a unitary construction with centerbody  450  using the DMLS method. In another embodiment of the invention, the centerbody  450 , the venturi  500  and a heat shield similar to item  540  shown in  FIGS. 4 and 18  may be made integrally to have a unitary construction using the DMLS method. 
         [0072]    The exemplary embodiment of the fuel nozzle  100  described herein comprises unitary components such as, for example, the unitary conduit  80 /distributor  300 , unitary swirler  200 , unitary venturi  500  and unitary centerbody  450 . Such unitary components used in the fuel nozzle  100  can be made using rapid manufacturing processes such as Direct Metal Laser Sintering (DMLS), Laser Net Shape Manufacturing (LNSM), electron beam sintering and other known processes in the manufacturing. DMLS is the preferred method of manufacturing the unitary components used in the fuel nozzle  100 , such as, for example, the unitary conduit  80 /distributor  300 , unitary swirler  200 , unitary venturi  500  and unitary centerbody  450  described herein. 
         [0073]      FIG. 5  is a flow chart illustrating an exemplary embodiment of a method  700  for fabricating unitary components for fuel nozzle  100 , such as, for example, shown as items  80 ,  200 ,  300 ,  450  and  500  in  FIGS. 2-18  and described herein. Although the method of fabrication  700  is described below using unitary components  80 ,  200 ,  300 ,  450  and  500  as examples, the same methods, steps, procedures, etc. apply for alternative exemplary embodiments of these components. Method  700  includes fabricating a unitary component  80 ,  200 ,  300 ,  450 ,  500  using Direct Metal Laser Sintering (DMLS). DMLS is a known manufacturing process that fabricates metal components using three-dimensional information, for example a three-dimensional computer model, of the component. The three-dimensional information is converted into a plurality of slices, each slice defining a cross section of the component for a predetermined height of the slice. The component is then “built-up” slice by slice, or layer by layer, until finished. Each layer of the component is formed by fusing a metallic powder using a laser. 
         [0074]    Accordingly, method  700  includes the step  705  of determining three-dimensional information of a specific unitary component  80 ,  200 ,  300 ,  450 ,  500  in the fuel nozzle  100  and the step  710  of converting the three-dimensional information into a plurality of slices that each define a cross-sectional layer of the unitary component. The unitary component  80 ,  200 ,  300 ,  450 ,  500  is then fabricated using DMLS, or more specifically each layer is successively formed in step  715  by fusing a metallic powder using laser energy. Each layer has a size between about 0.0005 inches and about 0.001 inches. Unitary components  80 ,  200 ,  300 ,  450 ,  500  may be fabricated using any suitable laser sintering machine. Examples of suitable laser sintering machines include, but are not limited to, an EOSINT® M 270 DMLS machine, a PHENIX PM250 machine, and/or an EOSINT® M 250 Xtended DMLS machine, available from EOS of North America, Inc. of Novi, Mich. The metallic powder used to fabricate unitary components  80 ,  200 ,  300 ,  450 ,  500  is preferably a powder including cobalt chromium, but may be any other suitable metallic powder, such as, but not limited to, HS 188 and INC0625. The metallic powder can have a particle size of between about 10 microns and 74 microns, preferably between about 15 microns and about 30 microns. 
         [0075]    Although the methods of manufacturing unitary components  80 ,  200 ,  300 ,  450 ,  500  in the fuel nozzle  100  have been described herein using DMLS as the preferred method, those skilled in the art of manufacturing will recognize that any other suitable rapid manufacturing methods using layer-by-layer construction or additive fabrication can also be used. These alternative rapid manufacturing methods include, but not limited to, Selective Laser Sintering (SLS), 3D printing, such as by inkjets and laserjets, Sterolithography (SLS), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing (LNSM) and Direct Metal Deposition (DMD). 
         [0076]    Another aspect of the present invention comprises a simple method of assembly of the fuel nozzle  100  having unitary components having complex geometrical features as described earlier herein. The use of unitary components in the fuel nozzle  100  as described herein has enabled the assembly of fuel nozzle  100  having fewer number of components and with fewer number of joints than conventional nozzles. For example, in the exemplary embodiment of the fuel nozzle  100  shown herein, the fuel nozzle tip  68  comprises only seven braze joints and one weld joint, whereas some known conventional nozzles have twenty two braze joints and three weld joints. 
         [0077]    An exemplary method of assembly  800  according to the present invention is shown in  FIG. 6  and Steps are described in detail below. The exemplary method of assembly  800  shown  FIG. 6  can be used to assemble the exemplary fuel nozzle  100  described previously herein. In the exemplary method of assembly  800  shown in  FIG. 6 , the assembly process uses fewer number of components and joints, and is simpler than conventional methods. 
         [0078]    Referring to  FIG. 6  for the various steps described below to assemble the exemplary fuel nozzle  100 , in Step  851 , a preformed braze wire  602  is inserted into a braze groove  601  in Primary Fuel Swirler  603  as shown in  FIG. 7 . The braze wire material can be a known braze material, such as AMS4786 (gold nickel alloy). In  FIG. 7  the exemplary braze wire  602  has a circular cross section. Other suitable cross sectional shapes for the braze wire  602  and corresponding shapes for the braze grove  601  can be used. 
         [0079]    In Step  852  the Primary Fuel Swirler  603  is press-fit into the Primary Orifice  606  as shown in  FIG. 8 . 
         [0080]    In Step  853 , the Primary Fuel Swirler  603  and Primary Orifice  606  are brazed together to form a Primary Pilot Assembly  607  as shown in  FIG. 8 . Brazing is performed using known methods. A brazing temperature of between 1840 Deg. F and 1960 Deg. F can be used. Brazing at a temperature of 1950 Deg. F is preferred. 
         [0081]    In Step  854 , the Primary Pilot Assembly  607  IS inserted into the Adapter  250  and Inner Swirler  200  as shown in  FIG. 9 . 
         [0082]    In the optional Step  855 , fuel flow check is performed, to check the fuel flow patterns in the pilot fuel flow circuits. An exemplary arrangement is shown in  FIG. 9 , showing a primary pilot flow circuit  608  and a secondary pilot flow circuit  609 . Suitable test fixtures known in the art, such as for example shown as item  604  in  FIG. 9  may be used during the flow checking step  855 . Known sealing methods, such as for example using O-rings  616  shown in  FIG. 9 , may be used for preventing fuel leakage during the optional flow checking step  855 . After flow checking is completed, the primary pilot assembly  607  is removed from test fixture  604  and adapter  250  and inner swirler  200 . 
         [0083]    In the optional Step  856 , a non-destructive inspection of the braze joint in the primary pilot assembly  607  is performed, as shown for example in  FIG. 10 . X-ray inspection using known techniques is preferred for inspecting the braze joint. X-rays  610  from a known X-ray source  611  can be used. 
         [0084]    In Step  857 , a preformed braze wire is inserted in a braze-groove in the distributor  300  fuel circuit pilot areas.  FIG. 11  shows an exemplary braze groove  612  in the pilot supply tube  154  around the wall surrounding the primary pilot flow passage  102 . The exemplary distributor  300  shown in  FIG. 11  also comprises a secondary pilot flow passage  104 , and a braze groove  614  that is formed around the wall surrounding the secondary pilot flow passage  104 . As described previously herein, the braze grooves  612  and  614  may be formed in a unitary distributor  300  using the manufacturing techniques such as DMLS. Alternatively, these braze grooves may be formed using machining or other known techniques. The braze wires  613 ,  615  can be made from a known braze material, such as AMS4786 (gold nickel alloy). In  FIG. 11 , the exemplary braze wires  613  and  615  have circular cross sections. Other suitable cross sectional shapes for the braze wires  613 ,  615  and corresponding shapes for the braze grove  612 ,  614  can alternatively be used. In the exemplary Step  857 , the braze wire  613  is inserted into the braze groove  612  and the braze wire  615  is inserted into the braze groove  614  as shown in  FIG. 11 . 
         [0085]    In Step  858 , illustrated in  FIG. 11 , the Primary pilot assembly  607  is inserted on the primary fuel circuit portion of the primary pilot supply tube  154  of the distributor  300 . 
         [0086]    In Step  859 , illustrated in  FIGS. 11 and 12 , the inner swirler/adaptor  200  is inserted over assembly from Step  858 , such that the primary pilot assembly  607  and the braze wire  615  fit inside the inner swirler/adaptor  200 .  FIG. 12  shows the assembled condition after this step. 
         [0087]    In Step  860 , a preformed braze wire  253  is inserted into a groove  252  located in the wall  256  of the adapter/Inner Swirler  200  as shown in  FIG. 13 . A preformed braze wire  353  is inserted into a groove  352  located in distributor  300  wall as shown in  FIG. 13 . As described previously herein, the braze groove  252  in the adaptor may be formed in a unitary adaptor/swirler  200  and braze groove  352  may be formed in a unitary distributor  300  using the manufacturing techniques such as DMLS. Alternatively, these braze grooves may be formed using machining or other known techniques. The braze wires  253 ,  353  are made from known braze materials, such as AMS4786 (gold nickel alloy). In  FIG. 13 , the exemplary braze wires  253  and  353  have circular cross-sections. Other suitable cross-sectional shapes for the braze wires  253 ,  353  and corresponding shapes for the braze grove  252 ,  352  can alternatively be used. 
         [0088]    In Step  861 , the assembly of the primary pilot assembly  607 , adaptor/swirler  200  and distributor  300  having braze wires  613 ,  615 , 253 , 253  in their corresponding grooves as described above, is inserted into the stem  83  and positioned as shown in  FIG. 14 . 
         [0089]    In Step  862 , the assembly from Step  861  shown in  FIG. 14  is brazed. Brazing is performed using known methods. A brazing temperature of between 1800 Deg. F and 1860 Deg. F can be used. Brazing at a temperature of 1850 Deg. F is preferred. 
         [0090]    In the optional Step  863 , a non-destructive inspection of the braze joints formed in Step  862  (see  FIG. 14 ) is performed. X-ray inspection using known techniques is preferred for inspecting the braze joint. 
         [0091]    In Step  864 , the centerbody  450  (alternatively referred to herein as outer shell) is inserted over the assembly from Step  862  after brazing. The centerbody  450  is located circumferentially with respect to the distributor  300  by aligning the tab  451  in the centerbody  450  with a notch  320  that is located at the aft edge of the distributor (see  FIG. 13 ). Other known methods of circumferentially locating the outer shell may alternatively be used. 
         [0092]    In Step  865 , the outer shell  450  is welded to assembly obtained from Step  864 , shown in  FIG. 15 . Known welding methods can be used for this purpose. A preferred welding method is TIG welding, using HS188 weld wire. The resulting weld  460  between the outer shell  450  and the stem  83  is shown in  FIG. 15 . 
         [0093]    In Step  866 , referring to  FIG. 16 , preformed braze wire  505  is inserted to into a groove  504  and preformed braze wire  565  is inserted to into a groove  564  in the venturi  500 . As described previously herein, the grooves  504 ,  564  in the venturi may be formed in a unitary venturi  500  using the manufacturing techniques such as DMLS. Alternatively, these braze grooves may be formed using machining or other known techniques. The braze wires  505 ,  565  are made from known braze materials, such as AMS4786 (gold nickel alloy). In  FIG. 16 , the exemplary braze wires  505  and  565  have circular cross-sections. Other suitable cross-sectional shapes for the braze wires  505 ,  565  and corresponding shapes for the braze groves  504 ,  564  can alternatively be used. 
         [0094]    Referring to  FIG. 17 , in optional Step  867 , preformed braze wires  91 ,  93 ,  95 ,  97  are inserted into the corresponding grooves  92 ,  94 ,  96 ,  98  around the fuel circuit inlets in the conduit  80  or valve housing  99 . The braze wires  91 ,  93 ,  95 ,  97  are made from known braze materials, such as AMS4786 (gold nickel alloy). A circular cross sectional shape is preferred for the braze wires  91 ,  93 ,  95 ,  97 . However, other suitable cross sectional shape may alternatively be used. 
         [0095]    In optional Step  868 , the assembly from step  867  is inserted into the valve housing  99 , shown in  FIG. 17 . 
         [0096]    In Step  869 , the assembly shown in  FIG. 18  is brazed. The assembly shown in  FIG. 17 , if selected in optional Step  868 , is also brazed. Brazing is performed using known methods. A brazing temperature of between 1800 Deg. F and 1860 Deg. F can be used. Brazing at a temperature of 1850 Deg. F is preferred. 
         [0097]    In the optional Step  870 , a non-destructive inspection of the braze joints formed in Step  869  (see  FIGS. 17 and 18 ) is performed. X-ray inspection using known techniques is preferred for inspecting the braze joints. 
         [0098]    The fuel nozzle  100  in a turbine engine (see  FIGS. 1-4 ) and the method of assembly  800  (see  FIG. 6 ) comprises fewer components and joints than known fuel nozzles. Specifically, the above described fuel nozzle  100  requires fewer components because of the use of one-piece, unitary components such as, for example, unitary conduit  80 /distributor  300 , unitary swirler  200  and unitary venturi  500 . As a result, the described fuel nozzle  100  provides a lighter, less costly alternative to known fuel nozzles. Moreover, the described unitary construction for at least some of the fuel nozzle  100  components and method of assembly  800  provides fewer opportunities for leakage or failure and is more easily repairable compared to known fuel nozzles. 
         [0099]    As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. When introducing elements/components/steps etc. of fuel nozzle  100  and its components described and/or illustrated herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0100]    Although the methods such as method of manufacture  700  and method of assembly  800 , and articles such as unitary conduit  80 /distributor  300 , unitary swirler  200 , unitary venturi  500  and unitary centerbody  450  described herein are described in the context of swirling of air for mixing liquid fuel with air in fuel nozzles in a turbine engine, it is understood that the unitary components and methods of their manufacture and their assembly described herein are not limited to fuel nozzles or turbine engines. The method of manufacture  700 , method of assembly  800  and fuel nozzle  100  and its components illustrated in the figures included herein are not limited to the specific embodiments described herein, but rather, these can be utilized independently and separately from other components described herein. 
         [0101]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.