Patent Publication Number: US-10775048-B2

Title: Fuel nozzle for a gas turbine engine

Description:
FIELD 
     The present subject matter relates generally to a fuel nozzle for a gas turbine engine. 
     BACKGROUND 
     A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air using one or more fuel nozzles within the combustion section and burned to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gasses through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere. 
     More specifically, the fuel nozzles function to introduce liquid fuel into an air flow stream such that the liquid fuel may atomize and burn. Additionally, staged fuel nozzles have been developed to operate with relatively high efficiency and operability. In a staged fuel nozzle, fuel may be introduced through two or more discrete stages, with each stage being defined by an individual fuel flow path within the fuel nozzle. For example, at least certain staged fuel nozzles include a pilot stage that may be operable continuously, and a main stage that operates at, e.g., high power levels. 
     With certain embodiments, the main stage may include an annular main injection ring having a plurality of fuel injection ports which discharge fuel through a round centerbody into a swirling mixer airstream. When the main stage is not in use, it may be beneficial to purge at least a portion of the fuel therein such that the fuel does not increase in temperature and begin to coke. Accordingly, a fuel nozzle with one or more features enabling the main stage of the fuel nozzle to purge at least a portion of the fuel therein would be useful. 
     BRIEF DESCRIPTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one exemplary embodiment of the present disclosure a fuel nozzle for a gas turbine engine is provided. The fuel nozzle defines a centerline axis and includes an outer body extending generally along the centerline axis and defining an exterior surface, the outer body defining a plurality of openings in the exterior surface. The fuel nozzle additionally includes a main injection ring disposed at least partially inside the outer body, the main injection ring including a fuel post extending into or through one of the plurality of openings of the outer body. The fuel post defines a spray well and a main fuel orifice, the spray well defining a bottom surface, a side wall, and a taper in the bottom surface extending from the main fuel orifice towards the side wall. 
     In certain exemplary embodiments the main fuel orifice defines a centerline, wherein the taper extends at least about twenty degrees about the centerline of the main fuel orifice. 
     In certain exemplary embodiments the main fuel orifice defines a centerline, wherein the taper extends at least about forty-five degrees about the centerline of the main fuel orifice. 
     In certain exemplary embodiments the fuel post defines a top surface, wherein the taper defines a projection angle with a reference plane extending parallel to the top surface, and wherein the projection angle is greater than zero degrees and less than about seventy-five degrees. 
     In certain exemplary embodiments the spray well defines a maximum width, wherein the main fuel orifice defines a maximum width, and wherein the maximum width of the spray well is at least about twice as large as the maximum width of the main fuel orifice. 
     In certain exemplary embodiments the taper extends from the main fuel orifice to the side wall. 
     In certain exemplary embodiments a bottom edge of the taper extends in a substantially straight direction from the main fuel orifice generally towards the side wall. 
     In certain exemplary embodiments the side wall of the spray well defines a maximum height, wherein the taper in the bottom wall defines a maximum height, and wherein the maximum height of the taper is at least about five percent of the maximum height of the side wall of the spray well. For example, in certain exemplary embodiments, the maximum height of the taper is at least about ten percent of the maximum height of the side wall of the spray well. 
     In certain exemplary embodiments the fuel post further defines a top surface, wherein the top surface of the fuel post defines a scarf extending away from the spray well. 
     In certain exemplary embodiments the fuel post is configured as one of a plurality of fuel posts, wherein each fuel post defines a spray well and a main fuel orifice, the spray well of each fuel post defining a bottom surface, a side wall, and a taper in the bottom surface extending from the main fuel orifice towards the side wall. For example, certain exemplary embodiments each of the plurality of fuel posts further defines a top surface, wherein the top surfaces of each of the plurality of fuel posts each define a scarf extending away from the spray well. 
     In another exemplary embodiment of the present disclosure, a gas turbine engine is provided. The gas turbine engine includes a compressor section, a turbine section, and a combustion section located downstream of the compressor section and upstream of the turbine section. The combustion section includes a fuel nozzle defining a centerline axis. The fuel nozzle includes an outer body extending generally along the centerline axis and defining an exterior surface, the outer body defining a plurality of openings in the exterior surface. The fuel nozzle also includes a main injection ring disposed at least partially inside the outer body. The main injection ring includes a fuel post extending into or through one of the plurality of openings of the outer body. The fuel post defines a spray well and a main fuel orifice, the spray well defining a bottom surface, a side wall, and a taper in the bottom surface extending from the main fuel orifice towards the side wall. 
     In certain exemplary embodiments the main fuel orifice defines a centerline, wherein the taper extends at least about twenty degrees about the centerline of the main fuel orifice. 
     In certain exemplary embodiments the main fuel orifice defines a centerline, wherein the taper extends at least about forty-five degrees about the centerline of the main fuel orifice. 
     In certain exemplary embodiments the fuel post defines a top surface, wherein the taper defines a projection angle with a reference plane extending parallel to the top surface, and wherein the projection angle is greater than zero degrees and less than about seventy-five degrees. 
     In certain exemplary embodiments the spray well defines a maximum width, wherein the main fuel orifice defines a maximum width, and wherein the maximum width of the spray well is at least about twice as large as the maximum width of the main fuel orifice. 
     In certain exemplary embodiments the taper extends from the main fuel orifice to the side wall. 
     In certain exemplary embodiments a bottom edge of the taper extends in a substantially straight direction from the main fuel orifice generally towards the side wall. 
     In certain exemplary embodiments the side wall of the spray well defines a maximum height, wherein the taper in the bottom wall defines a maximum height, and wherein the maximum height of the taper is at least about five percent of the maximum height of the side wall of the spray well. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a schematic cross-sectional view of an exemplary gas turbine engine according to various embodiments of the present subject matter. 
         FIG. 2  is a schematic, cross-sectional view of a fuel nozzle in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 3  is a close-up, cross-sectional view of a section of the exemplary fuel nozzle of  FIG. 2 . 
         FIG. 4  is a perspective view of a section of the exemplary fuel nozzle of  FIG. 2 . 
         FIG. 5  is a plan view of a section of the exemplary fuel nozzle of  FIG. 2 . 
         FIG. 6  is a perspective view of a fuel post of a fuel nozzle in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 7  is a side, cross-sectional view of the exemplary fuel post of  FIG. 6 . 
         FIG. 8  is a side, cross-sectional view of a fuel post of a fuel nozzle in accordance with another exemplary embodiment of the present disclosure. 
         FIG. 9  is a close-up, side, cross-sectional view of the exemplary fuel post of  FIG. 8 . 
         FIG. 10  is a top view of a spray well of a fuel post in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 11  is a top view of a spray well of a fuel post in accordance with another exemplary embodiment of the present disclosure. 
         FIG. 12  is a top view of a spray well of a fuel post in accordance with yet another exemplary embodiment of the present disclosure. 
         FIG. 13  is a top view of a spray well of a fuel post in accordance with still another exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. 
     As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. 
     The terms “forward” and “aft” refer to relative positions within a gas turbine engine, with forward referring to a position closer to an engine inlet and aft referring to a position closer to an engine nozzle or exhaust. 
     The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. 
     The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
     Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. 
     Here and throughout the specification and claims, range limitations may be combined and interchanged, such that ranges identified include all the sub-ranges contained therein unless context or language indicates otherwise. 
     Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  is a schematic cross-sectional view of a gas turbine engine in accordance with an exemplary embodiment of the present disclosure. More particularly, for the embodiment of  FIG. 1 , the gas turbine engine is a high-bypass turbofan jet engine  10 , referred to herein as “turbofan engine  10 .” As shown in  FIG. 1 , the turbofan engine  10  defines an axial direction A (extending parallel to a longitudinal centerline  12  provided for reference), a radial direction R, and a circumferential direction (i.e., a direction extending about the axial direction A; not depicted). In general, the turbofan  10  includes a fan section  14  and a core turbine engine  16  disposed downstream from the fan section  14 . 
     The exemplary core turbine engine  16  depicted generally includes a substantially tubular outer casing  18  that defines an annular inlet  20 . The outer casing  18  encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor  22  and a high pressure (HP) compressor  24 ; a combustion section  26 ; a turbine section including a high pressure (HP) turbine  28  and a low pressure (LP) turbine  30 ; and a jet exhaust nozzle section  32 . A high pressure (HP) shaft or spool  34  drivingly connects the HP turbine  28  to the HP compressor  24 . A low pressure (LP) shaft or spool  36  drivingly connects the LP turbine  30  to the LP compressor  22 . The compressor section, combustion section  26 , turbine section, and jet exhaust nozzle section  32  together define a core air flowpath  37  through the core turbine engine  16 . 
     For the embodiment depicted, the fan section  14  includes a variable pitch fan  38  having a plurality of fan blades  40  coupled to a disk  42  in a spaced apart manner. As depicted, the fan blades  40  extend outwardly from disk  42  generally along the radial direction R. Each fan blade  40  is rotatable relative to the disk  42  about a pitch axis P by virtue of the fan blades  40  being operatively coupled to a suitable actuation member  44  configured to collectively vary the pitch of the fan blades  40  in unison. The fan blades  40 , disk  42 , and actuation member  44  are together rotatable about the longitudinal axis  12  by LP shaft  36  across a power gear box  46 . The power gear box  46  includes a plurality of gears for stepping down the rotational speed of the LP shaft  36  to a more efficient rotational fan speed. 
     Referring still to the exemplary embodiment of  FIG. 1 , the disk  42  is covered by rotatable front nacelle  48  aerodynamically contoured to promote an airflow through the plurality of fan blades  40 . Additionally, the exemplary fan section  14  includes an annular fan casing or outer nacelle  50  that circumferentially surrounds the fan  38  and/or at least a portion of the core turbine engine  16 . It should be appreciated that the nacelle  50  may be configured to be supported relative to the core turbine engine  16  by a plurality of circumferentially-spaced outlet guide vanes  52 . Moreover, a downstream section  54  of the nacelle  50  may extend over an outer portion of the core turbine engine  16  so as to define a bypass airflow passage  56  therebetween. 
     During operation of the turbofan engine  10 , a volume of air  58  enters the turbofan  10  through an associated inlet  60  of the nacelle  50  and/or fan section  14 . As the volume of air  58  passes across the fan blades  40 , a first portion of the air  58  as indicated by arrows  62  is directed or routed into the bypass airflow passage  56  and a second portion of the air  58  as indicated by arrow  64  is directed or routed into the LP compressor  22 . The ratio between the first portion of air  62  and the second portion of air  64  is commonly known as a bypass ratio. The pressure of the second portion of air  64  is then increased as it is routed through the high pressure (HP) compressor  24  and into the combustion section  26 , where it is mixed with fuel provided through one or more fuel nozzles and burned to provide combustion gases  66 . 
     The combustion gases  66  are routed from the combustion section  26 , through the HP turbine  28  where a portion of thermal and/or kinetic energy from the combustion gases  66  is extracted via sequential stages of HP turbine stator vanes  68  that are coupled to the outer casing  18  and HP turbine rotor blades  70  that are coupled to the HP shaft or spool  34 , thus causing the HP shaft or spool  34  to rotate, thereby supporting operation of the HP compressor  24 . The combustion gases  66  are then routed through the LP turbine  30  where a second portion of thermal and kinetic energy is extracted from the combustion gases  66  via sequential stages of LP turbine stator vanes  72  that are coupled to the outer casing  18  and LP turbine rotor blades  74  that are coupled to the LP shaft or spool  36 , thus causing the LP shaft or spool  36  to rotate, thereby supporting operation of the LP compressor  22  and/or rotation of the fan  38 . 
     The combustion gases  66  are subsequently routed through the jet exhaust nozzle section  32  of the core turbine engine  16  to provide propulsive thrust. Simultaneously, the pressure of the first portion of air  62  is substantially increased as the first portion of air  62  is routed through the bypass airflow passage  56  before it is exhausted from a fan nozzle exhaust section  76  of the turbofan  10 , also providing propulsive thrust. The HP turbine  28 , the LP turbine  30 , and the jet exhaust nozzle section  32  at least partially define a hot gas path  78  for routing the combustion gases  66  through the core turbine engine  16 . 
     It should be appreciated, however, that the exemplary turbofan engine  10  depicted in  FIG. 1  is by way of example only, and that in other exemplary embodiments, the turbofan engine  10  may have any other suitable configuration. Additionally, or alternatively, aspects of the present disclosure may be utilized with any other suitable aeronautical gas turbine engine, such as a turboshaft engine, turboprop engine, turbojet engine, etc. Moreover, aspects of the present disclosure may further be utilized with any other land-based gas turbine engine, such as a power generation gas turbine engine, or any aeroderivative gas turbine engine, such as a nautical gas turbine engine. 
     Referring now to  FIG. 2 , a side, cross-sectional view is provided of a fuel nozzle  100  in accordance with an exemplary embodiment of the present disclosure. The exemplary fuel nozzle  100  depicted in  FIG. 2  may be included within a combustor assembly of the exemplary combustion section  26  described above with reference to  FIG. 1 . Alternatively, however, the exemplary fuel nozzle  100  of  FIG. 2  may instead be included within a combustor assembly of a combustion section  26  of any other suitable gas turbine engine. 
     The exemplary fuel nozzle  100  of  FIG. 2  may be configured to inject liquid hydrocarbon fuel into an airflow stream of the combustor assembly with which it is included. The fuel nozzle  100  is of a “staged” type, meaning it is operable to selectively inject fuel through two or more discrete stages, each stage being defined by individual fuel flowpaths within the fuel nozzle  100 . A fuel flowrate may also be variable within each of the stages. 
     The fuel nozzle  100  is connected to a fuel system  102  operable to supply a flow of liquid fuel at varying flowrates according to operational need. The fuel system  102  supplies fuel to a pilot control valve  104  which is coupled to a pilot fuel conduit  106 , which in turn supplies fuel to a pilot  108  of the fuel nozzle  100 . The fuel system  102  also supplies fuel to a main valve  110  which is coupled to a main fuel conduit  112 , which in turn supplies a main injection ring  114  of the fuel nozzle  100 . 
     The fuel nozzle  100  generally defines an axial direction A 2  extending along a centerline axis  116 , a radial direction R 2 , and a circumferential direction C 2 . The centerline axis  116  of the fuel nozzle  100  may generally be parallel to a longitudinal centerline of a gas turbine engine within which it is installed (see, e.g., longitudinal centerline  12  of turbofan engine  10  of  FIG. 1 ). Starting from the centerline axis  116  and proceeding outwardly along the radial direction R 2 , the illustrated fuel nozzle  100  includes: the pilot  108 , a splitter  118 , a venturi  120 , an inner body  122 , the main injection ring  114 , and an outer body  124 . Each of these structures will be described in more detail below. 
     The pilot  108  is disposed at an upstream end of the fuel nozzle  100 , aligned with the centerline axis  116  and surrounded by a fairing  126 . The illustrated pilot  108  includes a generally cylindrical, axially-elongated, pilot centerbody  128 . An upstream end of the pilot centerbody  128  is connected to the fairing  126 . The downstream end of the pilot centerbody  128  includes a converging-diverging discharge orifice  130  with a conical exit. 
     A metering plug  132  is disposed within a central bore  134  of the pilot centerbody  128 . The metering plug  132  communicates with the pilot fuel conduit. The metering plug  132  includes transfer holes  136  that flow fuel to a feed annulus  138  defined between the metering plug  132  and the central bore  134 , and also includes an array of angled spray holes  140  arranged to receive fuel from the feed annulus  138  and flow it towards the discharge orifice  130  in a swirling pattern, with a tangential velocity component. 
     The annular splitter  118  surrounds the pilot injector  108 . It includes, in axial sequence: a generally cylindrical upstream section  144 , a throat  146  of minimum diameter, and a downstream diverging section  148 . Additionally, an inner air swirler comprises a radial array of inner swirl vanes  150  which extend between the pilot centerbody  128  and the upstream section  144  of the splitter  118 . The inner swirl vanes  150  are shaped and oriented to induce a swirl into air flow passing through the inner air swirler. 
     The annular venturi  120  surrounds the splitter  118 . It includes, in axial sequence: a generally cylindrical upstream section  152 , a throat  154  of minimum diameter, and a downstream diverging section  156 . A radial array of outer swirl vanes  158 , defining an outer air swirler, extends between the splitter  118  and the venturi  120 . The outer swirl vanes  158 , splitter  118 , and inner swirl vanes  150  physically support the pilot  108 . The outer swirl vanes  158  are shaped and oriented to induce a swirl into air flow passing through the outer air swirler. The bore of the venturi  120  defines a flowpath for a pilot air flow, generally designated “P”, through the fuel nozzle  100 . A heat shield  160  in the form of an annular, radially-extending plate may be disposed at an aft end of the diverging section  156 . A thermal barrier coating (TBC) (not shown) of a known type may be applied on the surface of the heat shield  160  and/or the diverging section  156 . 
     The inner body  122  may be connected to the fairing  126  and serves as part of a mechanical connection between the main injection ring  114  and stationary mounting structure such as a fuel nozzle stem, a portion of which is shown as item  162 . 
     The main injection ring  114  is for the embodiment depicted annular in form and surrounds the inner body  122 . More specifically, the main injection ring  114  extends generally about the centerline axis  116  (i.e., in a circumferential direction C 2 ). It is connected to the inner body  122  and to the outer body  124  by a suspension structure  188  which is described in more detail below with reference to  FIG. 3 . 
     Referring now also to  FIG. 3 , providing a close-up view of the exemplary main injection ring  114 , the main injection ring  114  includes a main fuel gallery  164  (sometimes also referred to as a main fuel tube). The main fuel gallery  164  is coupled to and supplied with fuel by the main fuel conduit  112 . A radial array of main fuel orifices  166  formed in the main injection ring  114  communicate with the main fuel gallery  164 . During engine operation, fuel is discharged through the main fuel orifices  166 . Running through the main injection ring  114  closely adjacent to the main fuel gallery  164  are one or more pilot fuel galleries  168 . During engine operation, fuel may constantly circulate through the pilot fuel galleries  168  to cool the main injection ring  114  and prevent coking of the main fuel gallery  164  and the main fuel orifices  166 . 
     The outer body  124  is generally annular in shape for the embodiment depicted and generally defines the outer extent of the fuel nozzle  100 . Accordingly, the main injection ring  114  is disposed at least partially inside the outer body  124 , or rather is disposed substantially inside the outer body  124 , as is the venturi  120  and the pilot  108 . In the illustrated example, an aft end of the inner body  122  is connected to the outer body  124  by a radially-extending flange  170 . A forward end of the outer body  124  is joined to the stem  162  when assembled (see  FIG. 2 ). An aft end of the outer body  124  may include an annular, radially-extending baffle  174  incorporating cooling holes  176  directed at the heat shield  160 . Extending between the forward and aft ends is a generally cylindrical exterior surface  178 . In operation, the exterior surface  178  defines an airflow direction in which a mixer airflow, generally designated “M”, flows over the exterior surface  178 . Accordingly, as will be described in greater detail below, the mixer airflow generally swirls around the exterior surface  178  of the outer body  124  along the mixer airflow direction M. 
     The exemplary outer body  124  of  FIG. 2  additionally defines a secondary flowpath  180 , in cooperation with the venturi  120  and the inner body  122 . Air passing through this secondary flowpath  180  is discharged through the cooling holes  176 . 
     Moreover, referring still to  FIGS. 2 and 3 , the outer body  124  additionally defines a plurality of openings  182  in the exterior surface  178  of the outer body  124 . Each of the main fuel orifices  166  is aligned with one of the openings  182 . Additionally, for the embodiment of  FIGS. 2 and 3 , the plurality of openings  182  are arranged in an annular array, spaced substantially evenly along the circumferential direction C 2  of the fuel nozzle  100 . As is described below, fuel posts  202  extend into or through these openings  182 . 
     The outer body  124  and the inner body  122  cooperate to define an annular tertiary space or void  184  protected from the surrounding, external air flow. The main injection ring  114  is contained in this void  184 . Within the fuel nozzle  100 , a flowpath is provided for the tip air stream to communicate with and supply the void  184  a minimal flow needed to maintain a small pressure margin above the external pressure at locations near the openings  182 . In the illustrated example, this flow is provided by a relatively small supply slot  186 . 
     The fuel nozzle  100  and its constituent components may be constructed from one or more metallic alloys. Nonlimiting examples of suitable alloys include nickel and cobalt-based alloys. 
     All or part of the fuel nozzle  100  or portions thereof may be part of a single unitary, one-piece, or monolithic component, and may be manufactured using a manufacturing process which involves layer-by-layer construction or additive fabrication (as opposed to material removal as with conventional machining processes). Such processes may be referred to as “rapid manufacturing processes” and/or “additive manufacturing processes,” with the term “additive manufacturing process” being used herein to refer generally to such processes. Additive manufacturing processes include, but are not limited to: Direct Metal Laser Melting (DMLM), Laser Net Shape Manufacturing (LNSM), electron beam sintering, Selective Laser Sintering (SLS), 3D printing, such as by inkjets and laserjets, Sterolithography (SLA), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), and Direct Metal Deposition (DMD). 
     The main injection ring  114  is attached to the inner body  122  and to the outer body  124  by a suspension structure  188 . The suspension structure  188  includes an annular inner arm  190  extending forward from the flange  170  generally along the axial direction A 2 . The inner arm  190  passes radially inboard of the main injection ring  114 . In section view, the inner arm  190  is curved convex-inward, and is spaced-away from and generally parallels the convex curvature of an inner surface  148  of the main injection ring  114 . An annular outer arm  192  extends axially forward from the main injection ring  114 . A U-bend  194  interconnects the inner and outer arms  190 ,  192  at a location forward of the main injection ring  114  along the axial direction A 2 . A baffle  196  extends forward from the flange  170  also generally along the axial direction A 2 . The baffle  196  passes radially outboard of the main injection ring  114 , between the main injection ring  114  and the outer body  124 . In section view the baffle  196  is curved convex-outward, and is spaced-away from and generally parallels the convex curvature of an outer surface  198  of the main injection ring  114 . The baffle  196  includes an opening  200  through which a fuel post  202  (described in greater detail below) passes, and a forward end  204  of the baffle is connected to the outer body  124  forward of the opening  200 . Notably, for the embodiment depicted, the fuel post  202  at least partially defines the main fuel orifice  166 . 
     The suspension structure  188  is effective to substantially rigidly locate the position of the main injection ring  114  in axial and circumferential directions A 2 , C 2  while permitting controlled deflection in a radial direction R 2 . This is accomplished by the size, shape, and orientation of the elements of the suspension structure  188 . In particular, the inner and outer arms  190 ,  192  and the U-bend  194  are configured to act as a spring element in the radial direction R 2 . In effect, the main injection ring  114  substantially has one degree of freedom of movement (“1-DOF”). 
     It should be appreciated, however, that the fuel nozzle  100  described above is by way of example only, and that in other exemplary embodiments the fuel nozzle  100  may have any other suitable configuration, and may be formed in any other suitable manner. For example, in other exemplary embodiments the main injection ring  114  may instead be mounted to the outer body  124  in any other suitable manner. 
     Referring still to  FIGS. 2 and 3 , the main injection ring  114 , main fuel orifices  166 , and openings  182  may be configured to provide a controlled secondary purge air path and an air assist at the main fuel orifices  166  through perimeter gaps  206  defined around the fuel posts  202 . The openings  182  are oriented in a radial direction R 2  relative to the centerline axis  116 , and each fuel post  202  is aligned with one of the openings  182  and is positioned to define the perimeter gap  206  in cooperation with the associated opening  182 . These small controlled gaps  206  around the fuel posts  202  permit minimal purge air to flow through to protect internal tip space or void  96  from fuel ingress. 
     During engine operation, the outer body  124  is exposed to a flow of high-temperature air and therefore experiences relatively significant thermal expansion and contraction, while the main injection ring  114  is constantly cooled by a flow of liquid fuel and remains relative stable. The effect of the suspension structure  188  is to permit thermal growth of the outer body  124  relative to the main injection ring  114  and centerline axis  116  while maintaining a size of perimeter gaps  206  described above, thereby maintaining the effectiveness of the purge flow. 
     Additionally, as briefly mentioned above, the main injection ring  114  includes a plurality of raised fuel posts  202  extending outwardly along the radial direction R 2  from the main fuel gallery  164  of the main injection ring  114  into or through the plurality of openings  182  of the outer body  124 . The fuel posts  202  include a perimeter wall  208  defining a lateral surface  210 . Additionally, the fuel posts  202  define a distal, top surface  212 , a radially-facing floor  214  recessed from the top surface  212 , and a spray well  216  therebetween. The spray well  216  is fluidly connected with a respective main fuel orifice  166  to receive a flow of fuel therefrom. Additionally, as is indicated the main fuel gallery  164  extends generally about the centerline axis  116  (e.g., in a circumferential direction C 2 ) fluidly connecting the array of fuel posts  202 , or more particularly, fluidly connecting with each of the main fuel orifices  166  and the spray wells  216  of the respective fuel posts  202 . Accordingly, it will be appreciated that each of the main fuel orifices  166  extends through the floor  214  of the respective fuel post  202  to fluidly connect with the spray well  216  of the respective fuel post  202  to the respective main fuel orifice  166 . 
     Referring now to  FIGS. 4 and 5 , additional views of a portion of the exemplary fuel nozzle  100  of  FIGS. 2 and 3  are provided.  FIG. 4  provides a perspective view of the exemplary fuel nozzle  100 , and  FIG. 5  provides a top, plan view of a portion of the exemplary fuel nozzle  100 . 
     As is depicted, the openings  182  define a shape substantially similar to a shape of the top surface  212  of the respective fuel post  202 . Additionally, for the embodiment depicted, the top surfaces  212  of the plurality of fuel posts  202  each generally define at least one of a teardrop shape, an ovular shape, a circular shape, or an elliptical shape. More specifically, in the example illustrated the top surfaces  212  of the plurality of fuel posts  202  are each “teardrop-shaped,” having two convex-curved ends, with one end having a greater width than the other end (e.g., a greater maximum radius of curvature). Accordingly, the top surface  212  of each of the fuel posts  202  includes a narrow end  218  (i.e., the end with the lesser width) and a wide end  220  (i.e., the end with the greater width). 
     The elongated shape of the fuel posts  202  provides surface area so that the top end  212  of one or more of the fuel posts  202  can be configured to incorporate a ramp-shaped “scarf”  222 . The scarfs  222  can be arranged to generate local static pressure differences between other main fuel orifices  166  (e.g., adjacent main fuel orifices  166 ). These local static pressure differences between main fuel orifices  166  may be used to purge stagnant main fuel from the main injection ring  114  during periods of pilot-only operation as to avoid main circuit coking. 
     The orientation of the scarf  222  determines the static air pressure present at the associated main fuel orifice  166  during engine operation. The mixer air flowing in the airflow direction M defined by the outer body  124  exhibits “swirl,” that is, its velocity has both axial and circumferential components relative to the centerline axis  116 . More specifically, for the exemplary embodiment depicted, the airflow direction M defines an angle  224  with the centerline axis  116  greater than zero degrees and less than about seventy-five degrees. More specifically, for the exemplary embodiment depicted, the angle  224  between the airflow direction M and the centerline axis  116  is between about fifteen degrees and about sixty degrees, such as between about thirty degrees and about forty-five degrees. Notably, however, in other exemplary embodiments, the mixer air may flow/swirl in the other direction, such that the angle  224  defined between the airflow direction M and the centerline axis  116  is the reverse of the angles defined above (i.e., the negative of). Alternatively, in still other embodiments, the mixer air may define an angle  224  with the centerline axis  116  substantially equal to zero, such that the mixer air flows generally along the centerline axis  116 . 
     To achieve the purge function mentioned above, the spray wells  216  may be arranged such that different ones of the main fuel orifices  166  are exposed to different static pressures during engine operation. For example, the exemplary fuel nozzle  100  depicted, and more specifically, the exemplary main injection ring  114  depicted includes an LP fuel post  202 A, as well as an HP fuel post  202 B. The LP fuel post  202 A is generally configured to generate a “low static pressure” (i.e., a reduced static pressure relative to a prevailing static pressure in the mixer airflow) and the HP fuel post  202 B is generally configured to generate a “high static pressure” (i.e., an increased static pressure relative to a prevailing static pressure in the mixer airflow). Each of the LP fuel post  202 A and the HP fuel post  202 B defines a spray well  216 , a top surface  212 , and a scarf  222 . The scarf  222  of the LP fuel post  202 A extends in the top surface  212  from the spray well  216  in a first direction  226  relative to the centerline axis  116 . By contrast, the scarf  222  of the HP fuel post  202 B extends in the top surface  212  from the spray well  216  in a second direction  228  relative to the centerline axis  116 . The second direction  228  is at least about ninety degrees different than the first direction  226 , and the first direction  226  is substantially aligned with the airflow direction M defined by the outer body  124 . More specifically, for the embodiment depicted, the second direction  228  is about one hundred eighty degrees different than the first direction  226 , such that the scarf  222  of the HP fuel post  202 B extends upstream with respect to the airflow direction M. 
     Accordingly, the scarf  222  of the LP fuel post  202 A may generally be referred to as a “downstream” scarf, while the scarf  222  of the HP fuel post  202 B may generally be referred to as an “upstream” scarf. Additionally, as discussed, the top surfaces  212  of the LP and HP fuel posts  202 A,  202 B each generally define a teardrop shape including a narrow end  218  and a wide end  220 . For the top surface  212  of the HP fuel post  202 B, the narrow end  218  is positioned forward of the wide end  220  along the second direction  228  (i.e., upstream relative to the airflow direction M), and similarly, for the LP fuel post  202 A, the narrow end  218  is positioned forward of the wide end  220  along the first direction  226  (i.e., downstream relative to the airflow direction M). Notably, however, in other exemplary embodiments, the scarf  202  may have any other suitable shape, and/or the HP fuel post  202 B may be oriented in any other suitable manner. 
     For the embodiment depicted, the LP fuel post  202 A is arranged sequentially with the HP fuel post  202 B. More particularly, for the exemplary fuel nozzle  100  depicted, the array of fuel posts  202  further includes a plurality of LP fuel posts  202 A and a plurality of HP fuel post  202 B. Each of the plurality of LP fuel posts  202 A are, for the embodiment depicted, configured in substantially the same manner as one another, and further, each of the plurality of HP fuel posts  202 B are also configured in substantially the same manner as one another. Referring particularly to the embodiment of  FIG. 4 , the plurality of LP fuel posts  202 A are arranged with the plurality of HP fuel posts  202 B in a sequential and alternating manner (i.e., arranged in the following pattern: LP fuel post  202 A, HP fuel post  202 B, LP fuel post  202 A, HP fuel post  202 B, etc.) 
     It should be appreciated, however, that in other exemplary embodiments, the plurality of LP fuel posts  202 A and HP fuel posts  202 B may instead be arranged in any other suitable manner. For example, in other exemplary embodiments, the plurality of LP fuel posts  202 A may be grouped together and the plurality of HP fuel posts  202 B may also be grouped together. 
     Referring now to  FIGS. 6 and 7 , a fuel post  202  including a scarf  222  in accordance with an exemplary embodiment of the present disclosure is provided. The exemplary fuel post  202  and scarf  222  of  FIGS. 6 and 7  is described as an HP fuel post  202 B and scarf  222  (it being appreciated, however, that in other embodiments the fuel post  202  and scarf  222  depicted may instead be an LP fuel post  202 A and scarf  222 ). 
     As is depicted, the scarf  222  generally defines a height  230  and a length  232 . The scarf  222  defines a maximum height  230  at the spray well  216 . The length  232  of the scarf  222  extends in a direction parallel to the second direction  228 , extending gradually (with, for the embodiment depicted, a constant slope) to a minimum height  230  at a distal end of zero (i.e., flush with the top surface  212 ). Additionally, the exemplary spray well  216  defines a maximum width  234  and the scarf  222  similarly defines maximum width  236  (e.g., in a plane parallel to the top surface  212 ). For the embodiment depicted, the maximum width  236  of the scarf  222  is substantially equal to the maximum width  234  of the exemplary spray well  216 . 
     Referring particularly to  FIG. 7 , the length  232  of the scarf  222  refers to a total length  232  of the scarf  222  beginning at a centerline  238  of the spray well  216  and ending where the scarf  222  becomes flush with the top surface  212 . Additionally, the height  230  of the scarf  222  refers to a maximum height  230  of the scarf  222 . For the embodiment depicted, the length  232  may generally be greater than about forty thousandths of an inch (“mils”) and less than about three hundred mils. For example, in certain exemplary embodiments, the length  232  may generally be greater than about fifty mils and less than about two hundred and fifty mils, such as greater than about seventy-five mils and less than about two hundred mils. Additionally, the height  230  of the scarf  222  may generally be greater than about five mils and less than about fifty mils. For example, in certain exemplary embodiments, the height  230  of the scarf  222  may generally be greater than about ten mils and less than about forty mils, such as greater than about fifteen mils and less than about thirty mils. 
     As stated, for the embodiment depicted, the fuel post  202  is configured as an HP fuel post  202 B, such that the scarf  222  is configured as an upstream scarf  222 . Accordingly, in at least certain exemplary embodiments, the scarf  222  may define a length  232  to height  230  ratio between about one and a half ( 1 . 5 ) and about five, such as between about two and about four. However, in other exemplary embodiments, the fuel post  202  depicted may instead be configured as an LP fuel post  202 A, such that the scarf  222  is configured as a downstream scarf  222 . With such an exemplary embodiment, the scarf  222  may define a length  232  to height  230  ratio between about four and about nine, such as between about five and about eight. Accordingly, for certain exemplary fuel nozzles  100  the upstream scarf  222  may define a length  232  to height  230  ratio that is less than a length  232  to height  230  ratio of the downstream scarf  222  (such as at least about twenty percent less, such as at least about thirty percent less, such as at least about forty percent less, such as at least about fifty percent less). 
     Notably, in other exemplary embodiments, one or more of the LP fuel posts  202 A and/or HP fuel posts  202 B may define any other suitable scarf  222  in the respective top surfaces  212 . For example, in other exemplary embodiments, LP fuel posts  202 A and/or HP fuel posts  202 B may be oriented such that the scarf  222  extends from the spray well  216  towards the wide end  220  of the respective fuel post. With such an exemplary embodiment, the scarf may be configured as a channel extending with, e.g., a substantially constant depth along a length  232  thereof through an outer edge of the top surface  212  of the fuel post  202 . 
     As will be appreciated, inclusion of a fuel nozzle including a main injection ring having one or more fuel posts extending into or through respective openings in an outer body of the fuel nozzle with upstream scarfs, in combination with one or more fuel posts extending into or through respective openings in the outer body of the fuel nozzle with downstream scarfs, may provide for a greater pressure differential to provide the desired fuel purging. Such a configuration may therefore result in less fuel coking, and therefore may increase a useful life of the fuel nozzle. 
     It should be appreciated, however, that in other embodiments, the fuel nozzle  100  may have any other suitable configuration. For example, referring now to  FIG. 8 , a side, cross-sectional view is provided of a fuel post  202  of a fuel nozzle  100  in accordance with another exemplary embodiment of the present disclosure. The exemplary fuel post  202  and fuel nozzle  100  depicted in  FIG. 8  may be configured in substantially the same manner as one or more of the exemplary fuel posts  202  and fuel nozzles  100  described above with reference to  FIG. 2 through 7 . For example, in certain exemplary embodiments, the fuel post  202  may be an LP fuel post  202 A or an HP fuel post  202 B. 
     More specifically, the exemplary fuel post  202  of  FIG. 8  generally defines a top surface  212 , a spray well  216 , and a main fuel orifice  166 . Additionally, for the embodiment depicted the fuel post  202  includes a scarf  222  defined in the top surface  212  of the fuel post  202 , extending from the spray well  216 . The scarf  222  is configured in substantially the same manner as the exemplary scarf  222  described above with reference to  FIGS. 6 and 7 . However, in other exemplary embodiments, the scarf  222  may have any other suitable configurations, or alternatively the fuel post  202  may not include a scarf altogether. For example, in other exemplary embodiments, the top surface  212  may be substantially completely flat and continuous, with the exception only of the spray well  216 . 
     Referring still to  FIG. 8 , the spray well  216  defines a maximum width  234  and the main fuel orifice  166  also defines a maximum width  240 . The maximum width  234  of the spray well  216  is defined in a direction perpendicular to a centerline  238  of the spray well  216 , and similarly, the maximum width  240  of the main fuel orifice  166  is defined in a direction perpendicular to a centerline  242  of the main fuel orifice  166 . Notably, for the embodiment depicted the centerline  242  of the main fuel orifice  166  is aligned with the centerline  238  of the spray well  216 . Additionally, for the embodiment depicted the maximum width  234  of the spray well  216  is at least about twice as large as the maximum width  240  of the main fuel orifice  166 , such as at least about three times as large, and up to about ten times as large as the maximum width  240  of the main fuel orifice  166 . 
     Moreover, the spray well  216  generally includes one or more side walls  244  and a bottom wall  214 . In contrast to the previously discussed fuel posts  202 , for the embodiment of  FIG. 8 , the spray well  216  of the fuel post  202  additionally defines a taper  246  in the bottom wall  214  extending from the main fuel orifice  166  towards the side wall  244  of the spray well  216 . As will be discussed in greater detail below, such may reduce an overall surface tension of fuel in the spray well  216 , such that less pressure is required to force the fuel back through the main fuel orifice  166  during purging operations of the fuel nozzle  100 . 
     Referring now also to  FIG. 9 , a close-up view is provided of the exemplary fuel post  202  of  FIG. 8 , depicting the taper  246  defined in the bottom wall  214  of the spray well  216  in greater detail. As is depicted, for the embodiment of  FIG. 9  the taper  246  extends in a substantially straight direction from the main fuel orifice  166  generally towards a side wall  244  of the spray well  216 . More specifically, a bottom edge  248  of the taper  246  defines a substantially straight line extending from the main fuel orifice  166  generally towards the side wall  244  of the spray well  216 . Moreover, for the embodiment depicted the taper  246  extends from the main fuel orifice  166  all the way to the side wall  244 . Notably, however, in other exemplary embodiments, the taper  246  may extend between about 40% and 100% of the way to the side wall  244  (measured as a percent of a radius of the spray well  216 , or one half of the width  234  of the spray well  216 ), such as between about 50% and 100%, such as between about 60% and 100%, such as between about 80% and 100%. 
     Furthermore, for the embodiment depicted, the side wall  244  of the spray well  216  defines a maximum height  250  in a direction parallel to the centerline  238  of the spray well  216  (see  FIG. 8 ). Further, the taper  246  in the bottom wall  214  of the spray well  216  also defines a maximum height  252  in a direction parallel to the centerline  238  of the spray well  216 . For the embodiment depicted, the maximum height  252  of the taper  246  is at least about 5% of the maximum height  250  of the side wall  244  of the spray well  216 . For example, in certain embodiments, the maximum height  252  of the taper  246  may be at least about 10% of the maximum height  250  of the side wall  244  of the spray well  216 , and up to about 100% of the maximum height  250  of the side wall  244  of the spray well  216 . 
     Referring still to  FIG. 9 , will be appreciated that the taper  246  further defines a projection angle  254 . More particularly, the fuel post  202  defines a reference plane  255  extending parallel to the top surface  212  of the fuel post  202 , and the taper  246  defines a projection angle  254  with the reference plane  255  (i.e., the angle between the bottom edge  248  of the taper  246  and the reference plane  255 ). For example, the projection angle  254  is, for the embodiment depicted, greater than 0° and less than about 75°. However, in other embodiments, the projection angle  254  may be any other suitable angle. For example, in other exemplary embodiments, the projection angle  254  may be between about 20° and about 60°. 
     Referring now to  FIGS. 10 through 13 , top views are provided of additional exemplary embodiments of fuel posts  202  in accordance with aspects of the present disclosure. More particularly, the views provided in  FIGS. 10 through 13  are of a bottom wall  214  of a spray well  216  of the fuel post  202 , along the centerline  238  of the spray well  216  of the fuel post  202 . 
     As is depicted, each of the embodiments of  FIGS. 10 through 13  include a taper  246  extending from a main fuel orifice  166  towards the side wall  244 . Referring particularly to  FIGS. 10 through 12 , the taper  246  extends about the centerline  242  of the main fuel orifice  166  and about the centerline  238  of the spray well  216 . As is depicted, the taper  246  may extend about the centerline  238  of the spray well  216  greater than 0° and up to 360°. For example, in certain exemplary embodiments, the taper  246  may extend about the centerline  238  of the spray well  216  at least about 20° (see, e.g., the embodiment of  FIG. 10 ), such as at least about 45°, such as at least about 180° (see, e.g., the embodiment of  FIG. 11 ), such as up to 360° (see, e.g., the embodiment of  FIG. 12 ). 
     Notably, however, referring particularly to  FIG. 13 , in other exemplary embodiments, the taper  246  may instead have any other suitable shape, such as a shape that converges as it extends away from the main fuel orifice  166 . For example, for the embodiment depicted in  FIG. 13 , the taper  246  defines a convergence angle  256 . More specifically, side edges  258  of the taper  246  (i.e., the intersections between the taper  246  and the bottom wall  214 ) define the convergence angle  256 . For the embodiment depicted, the convergence angle  256  is between about 0° and about 45°. However, in other embodiments, any other suitable convergence angle  256  may be provided. 
     Inclusion of a taper in a bottom wall of a spray well of a fuel post in a fuel nozzle may allow for better purging of fuel in the fuel nozzle during purging operations. More specifically, inclusion of the taper may reduce an overall surface tension of fuel in the spray well, such that less pressure is required to force the fuel back through the main fuel orifice during purging operations of the fuel nozzle. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. 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 include 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 languages of the claims.