Abstract:
Fuel nozzles for gas turbines are provided that include liquid fuel cartridges. In one embodiment, a fuel nozzle includes a fuel plenum plate separating an air plenum from a fuel plenum. The fuel nozzle also includes a plurality of mixing tubes extending through the fuel plenum from the fuel plenum plate to a face plate. Each mixing tube includes an air inlet configured to receive air from the air plenum, a fuel inlet disposed in a tube wall within the fuel plenum to direct fuel from the fuel plenum into the mixing tube to produce a fuel-air mixture, and a fuel-air outlet configured to discharge the fuel-air mixture away from the face plate into a combustion region. The fuel nozzle further includes a liquid fuel cartridge extending through the air plenum and the fuel plenum to the face plate. The liquid fuel cartridge includes a liquid fuel passage.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to fuel nozzles and more specifically, to fuel nozzles for gas turbine combustors. 
         [0002]    In general, gas turbines combust a mixture of compressed air and fuel within a combustor to produce hot combustion gases. The hot combustion gases rotate blades of the turbine to rotate a shaft that drives a load, such as an electrical generator. Fuel nozzles within the combustor inject fuel and air into the combustor. In some designs, the fuel nozzles include one or more mixing tubes that pre-mix the fuel and air before the fuel and air enters the combustion zone. For example, the mixing tubes may be employed to mix a gaseous fuel with air. However, the fuel nozzles may not be designed to direct liquid fuel through the mixing tubes. For example, the mixing tubes may become clogged by liquid fuel due to the small size of the mixing tubes. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
         [0004]    In a first embodiment, a system includes a gas turbine fuel nozzle. The gas turbine fuel nozzle includes a fuel plenum plate separating an air plenum from a fuel plenum. The gas turbine fuel nozzle also includes a plurality of mixing tubes extending through the fuel plenum from the fuel plenum plate to a face plate, wherein each mixing tube comprises an air inlet configured to receive air from the air plenum, a fuel inlet disposed in a tube wall within the fuel plenum to direct fuel from the fuel plenum into the mixing tube to produce a fuel-air mixture, and a fuel-air outlet configured to discharge the fuel-air mixture away from the face plate into a combustion region. The fuel nozzle further includes a liquid fuel cartridge extending through the air plenum and the fuel plenum to the face plate, wherein the liquid fuel cartridge comprises a liquid fuel passage. 
         [0005]    In a second embodiment, a system includes a gas turbine fuel nozzle. The gas turbine fuel nozzle includes a fuel plenum plate and a face plate spaced from the fuel plenum plate to define a fuel plenum therebetween. The face plate includes mixing tube apertures disposed circumferentially around a liquid fuel cartridge aperture. The gas turbine fuel nozzle also includes a plurality of mixing tubes extending through the fuel plenum from the fuel plenum plate to a face plate. Each mixing tube comprises an air inlet configured to receive air from the air plenum, a fuel inlet disposed in a tube wall within the fuel plenum to direct fuel from the fuel plenum into the mixing tube to produce a fuel-air mixture, and a fuel-air outlet configured to discharge the fuel-air mixture away from the face plate into a combustion region. The fuel nozzle further includes a liquid fuel cartridge extending through the fuel plenum plate. The liquid fuel cartridge includes a nozzle portion disposed in the liquid fuel cartridge aperture, a liquid fuel passage coupled to the nozzle portion, and an air passage disposed around the liquid fuel passage. 
         [0006]    In a third embodiment, a system includes a gas turbine fuel nozzle. The gas turbine fuel nozzle includes a plurality of sector nozzles disposed adjacent to one another to form a circular cross section. Each sector nozzle of the plurality of sector nozzles includes a fuel plenum plate separating an air plenum from a fuel plenum plate. Each sector nozzle of the plurality of sector nozzles also includes a plurality of mixing tubes extending through the fuel plenum from the fuel plenum plate to a face plate. Each mixing tube comprises an air inlet configured to receive air from the air plenum, a fuel inlet disposed in a tube wall within the fuel plenum to direct fuel from the fuel plenum into the mixing tube to produce a fuel-air mixture, and a fuel-air outlet configured to discharge the fuel-air mixture away from the face plate into a combustion region. The gas turbine fuel nozzle also includes a liquid fuel cartridge that includes a liquid fuel passage and an air passage disposed in a concentric arrangement. The liquid fuel passage and the air passage are configured to output liquid fuel and air away from the face plate into the combustion region. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is a schematic flow diagram of an embodiment of a gas turbine system that may employ sector nozzles with liquid fuel cartridges; 
           [0009]      FIG. 2  is a cross-sectional view of the combustor of  FIG. 1 ; 
           [0010]      FIG. 3  is a cross-sectional view of an embodiment of a sector nozzle of the combustor of  FIG. 1 ; 
           [0011]      FIG. 4  is a front view of the combustor of  FIG. 1  illustrating a fuel nozzle assembly with multiple sector nozzles collectively fitting together across the interior of the combustor; 
           [0012]      FIG. 5  is a front view of another embodiment of a sector nozzle that includes a liquid fuel cartridge; 
           [0013]      FIG. 6  is a front view of another embodiment of a sector nozzle that includes a liquid fuel cartridge; 
           [0014]      FIG. 7  is a perspective view of an embodiment of a fuel nozzle assembly that includes a liquid fuel cartridge within a center nozzle; and 
           [0015]      FIG. 8  is a cross-sectional view of another embodiment of a sector nozzle of the combustor of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
         [0017]    When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
         [0018]    The present disclosure is directed to sector nozzles that include liquid fuel cartridges. Each sector nozzle may have a segmented shape, such as a wedge shaped cross section, that allows the sector nozzle to fit together with adjacent sector nozzles to form an annular ring of sector nozzles within a combustor of a gas turbine. A series of mixing tubes are disposed within each sector nozzle to produce a fuel-air mixture that is directed to the combustion zone. In particular, the mixing tubes direct air from an air plenum near the combustor end cover, through the mixing tubes to the nozzle face. A fuel plenum surrounds the mixing tubes and gaseous fuel from the fuel plenum is directed into the mixing tubes through apertures in the side of the tubes to produce the fuel-air mixture. The sector nozzles also may include a liquid fuel cartridge that directs liquid fuel, such as fuel oil or other distillates, to the combustion zone. Accordingly, the sector nozzles described herein may provide the flexibility to operate on liquid fuel, gaseous fuel, or a combination thereof. The liquid fuel cartridge may be located within the sector nozzle between the mixing tubes, and, in certain embodiments, may be radially surrounded by the mixing tubes. Accordingly, the liquid fuel may be directed through the liquid fuel cartridge to the combustion zone without flowing through the mixing tubes, which could be fouled by the liquid fuel. 
         [0019]    The liquid fuel cartridge extends from the combustor end cover through the fuel plenum to the nozzle face. Within the fuel plenum, the liquid fuel cartridge may be mounted within a tube that isolates the liquid fuel cartridge from the fuel within the fuel plenum. The liquid fuel cartridge includes an inner passage for directing liquid fuel through the liquid fuel cartridge and may also include one or more outer passages for directing air and/or water through the liquid fuel cartridge. A nozzle portion may be located at the end of the liquid fuel cartridge to direct the fuel into the combustion zone. According to certain embodiments, the nozzle portion expels the liquid fuel radially outward toward mixing tubes that are disposed radially around the liquid fuel cartridge. The mixing tubes may be disposed radially around the liquid fuel cartridge in a pattern designed to promote efficient mixing of the fuel and air. Further, in certain embodiments, a perimeter row of mixing tubes may be disposed around the outer circumference of the sector nozzle to inhibit liquid fuel from flowing past the sector nozzle towards the liner. 
         [0020]      FIG. 1  is a block diagram of an embodiment of a gas turbine system  10  that employs sector fuel nozzles that include liquid fuel cartridges. The gas turbine system  10  may be part of a simple cycle system or a combined cycle system. The gas turbine system  10  includes a combustor  12  that combusts fuel  14  to drive the gas turbine system  10 . According to certain embodiments, the fuel  14  may be a liquid or gaseous fuel, such as natural gas, light or heavy distillate oil, naphtha, crude oil, residual oil, or syngas. 
         [0021]    Within the combustor  12 , the fuel  14  may mix with pressurized air  16 , shown by arrows, and ignition may occur, producing hot combustion gases  18  that power the gas turbine system  10 . As discussed further below with respect to  FIG. 2 , the combustor  12  includes sector fuel nozzles that pre-mix the fuel  14  and the pressurized air  16  and direct the fuel-air mixture into a combustion chamber in a suitable ratio for optimal combustion, emissions, fuel consumption, and power output. Further, the sector nozzles also may include liquid fuel cartridges that direct liquid fuel into the combustion chamber. 
         [0022]    The pressurized air  16  includes intake air  20  that enters the gas turbine system  10  through an air intake section  22 . The intake air  20  is compressed by a compressor  24  to produce the pressurized air  16  that enters the combustor  12 . The sector fuel nozzles may direct the fuel  14  and the pressurized air  16  into the combustion zone of the combustor  12 . Within the combustion zone, the pressurized air  16  combusts with the fuel  14  to produce the hot combustion gases  18 . From the combustor  12 , the hot combustion gases  18  may flow through a turbine  26  that drives the compressor  24  via a shaft  28 . For example, the combustion gases  18  may apply motive forces to turbine rotor blades within the turbine  26  to rotate the shaft  28 . Shaft  28  also may be connected to a load  30 , such as a generator, a propeller, a transmission, or a drive system, among others. After flowing through the turbine  26 , the hot combustion gases  18  may exit the gas turbine system  10  through an exhaust section  32 . 
         [0023]      FIG. 2  is a cross-sectional view of an embodiment of the combustor  12 . The combustor  12  includes sector nozzles  34  that inject the fuel-air mixture into a combustion chamber  36 . The combustion chamber  36  is generally defined by a casing  38 , a liner  40 , and a flow sleeve  42 . The flow sleeve  42  may be located coaxially and/or annularly about the liner  40  to direct air from the compressor into the sector nozzles  34 , as generally shown by the arrows  43 . 
         [0024]    The sector nozzles  34  are arranged adjacent to one another to form a generally circular fuel nozzle assembly  44 . According to certain embodiments, each sector nozzle  34  has a wedge-shaped cross section designed to abut a pair of adjacent sector nozzles  34 . Further, in certain embodiments, each sector nozzle  34  may be arranged around a center fuel nozzle  46  ( FIG. 4 ). Each sector nozzle  34  may extend outward from the center fuel nozzle  46  in the radial direction  47 . Each sector nozzle  34  includes mixing tubes  48  that mix gaseous fuel and air to form a fuel-air mixture that is injected into the combustion chamber  36 . One or more of the sector nozzles  34  also may include a liquid fuel cartridge  50  that injects liquid fuel into the combustion chamber  36 . As discussed further below with respect to  FIG. 3 , the mixing tubes  48  may be disposed radially around the liquid fuel cartridge  50 . 
         [0025]    The sector nozzles  34  each include a base  52  that secures the sector nozzle  34  to an end cover  54  of the combustor  12 . For example, the base  52  may abut the end cover  54  and fasteners, such as bolts, may be inserted through corresponding openings in the base  52  and the end cover  54  to secure the base  52  to the end cover  54 . A shell  56  extends between the base  52  and a fuel plenum  58  in the axial direction  60 . The shell  56  generally encloses an air plenum  62  ( FIG. 3 ) that directs air from the compressor through the interior of the sector nozzles  34  to the mixing tubes  48 , which extend through the fuel plenum  58  to a face plate  66 . The shell  56  includes openings  64  that allow air from the compressor to enter the air plenum  62 . Fuel supply passages  68  ( FIG. 3 ) extend through the base  52  and the air plenum  62  to direct gaseous fuel into the fuel plenum  58 . Within the fuel plenum  58 , the gaseous fuel may enter the mixing tubes  48  through holes in the sides of the mixing tubes  48  to produce the fuel-air mixture that flows through the mixing tubes  48  to enter the combustion chamber  36 . The liquid fuel cartridge  50  extends through the base  52 , the air plenum  62 , and the fuel plenum  58  to direct liquid fuel into the combustion chamber  36 . Within the combustion chamber  36 , the fuel-air mixture is combusted to produce the hot combustion gases  18 . From the combustion chamber  36 , the hot combustion gases  18  flow through a transition piece  70  to the turbine  26 . 
         [0026]      FIG. 3  depicts one of the sector nozzles  34  sectioned to show the interior of the sector nozzle  34 . The liquid fuel cartridge  50  extends through an aperture  72  in the base  52 , through the air plenum  62 , and through the fuel plenum  58  to the face plate  66 . The fuel plenum  58  is generally defined by a fuel plenum plate  74  and the face plate  66 . A housing  76  is coupled to the fuel plenum plate  74  and the face plate  66  to enclose the fuel plenum  58 . 
         [0027]    One or more fuel supply passages  68  extend through the base  52  to the fuel plenum  58  to direct gaseous fuel into the fuel plenum  58 . The mixing tubes  48  extend through the fuel plenum  58  and are mounted in apertures  78  in the fuel plenum plate  74  and apertures  80  in the face plate  66 . The mixing tubes  48  include apertures  82  in the tube walls  84  that allow fuel from the fuel plenum  58  to enter the mixing tubes  48 . Air enters the sector nozzle  34  through windows  64  in the shell  56 , and then flows through the air plenum  62  to enter the ends of the mixing tubes  48  through the apertures  78  in the fuel plenum plate  74 . Within the mixing tubes  48 , the air mixes with fuel that enters the mixing tubes  48  through the apertures  82  to produce the fuel-air mixture that is directed into the combustion chamber  36 . In particular, the fuel-air mixture exits the mixing tubes  48  through the apertures  80  in the face plate  66 . The fuel plenum  58  also includes a housing  86  that encloses a portion of the mixing tubes  48 . The housing  86  is disposed adjacent to the face plate  66 , and in certain embodiments, may include fuel that may be employed to cool the face plate  66 . However, in other embodiments, the housing  86  may be omitted. Further, as described further below with respect to  FIG. 8 , in certain embodiments, air, rather than fuel, may be employed to cool the face plate  66 . 
         [0028]    The mixing tubes  48  are disposed radially around the liquid fuel cartridge  50 , which extends through an aperture  88  in the fuel plenum plate  74  and an aperture  90  in the face plate  66 . As shown in  FIG. 3 , the apertures  88  and  90  are centered within the fuel plenum plate  74  and the face plate  66 , respectively. Accordingly, the liquid fuel cartridge  50  extends axially through the approximate center of the sector nozzle  34 . However, in other embodiments, the locations of the apertures  88  and  90  may vary to dispose the liquid fuel cartridge  50  in other positions within the sector nozzle  34 . 
         [0029]    The liquid fuel cartridge  50  includes an inner tube  92  that defines a liquid fuel passage  94 , an intermediate tube  96  that defines a water passage  98 , and an outer tube  100  that defines an air passage  102 . According to certain embodiments, liquid fuel, water, and air, such as high-pressure atomizing air, may be supplied to the liquid fuel cartridge  50  through inlets in the liquid fuel cartridge  50  that are external to the sector nozzle  34 . The liquid fuel cartridge  50  also includes a nozzle portion  104  that expels the liquid fuel, water, and air, from the passages  94 ,  98 , and  102  through the face plate  66  into the combustion chamber  36  ( FIG. 2 ). As shown, the liquid fuel cartridge  50  includes three concentric tubes  92 ,  96 , and  100  that define three separate flow passages  94 ,  98 , and  102 , respectively. However, in other embodiments, any number of one or more tubes may be included within the liquid fuel cartridge  50 . For example, in certain embodiments, the liquid fuel cartridge  50  may include a single tube that supplies liquid fuel, or a combination of liquid fuel and water, to the combustion chamber. 
         [0030]    The liquid fuel cartridge  50  is disposed within a mounting tube  106  that extends through the fuel plenum  58  and is mounted within the aperture  88  in the fuel plenum plate  74  and the aperture  90  in the face plate  66 . The tube  106  may fit snugly within the apertures  88  and  90  to inhibit the escape of gaseous fuel through the apertures  88  and  90 . The tube  106  may include a lip  110  designed to interface with mounting pegs  111  disposed on the liquid fuel cartridge  50  to facilitate proper alignment of the liquid fuel cartridge within the tube  106 . Moreover, in certain embodiments, the mounting pegs  111  may have an aerodynamic cross section designed to direct air into a passage between the mounting tube  106  and the outer tube  100  of the liquid fuel cartridge  50 . However, in yet other embodiments, the tube  106  may fit snugly around the outer tube  100  of the liquid fuel cartridge  50 . 
         [0031]      FIG. 4  is a front view of the fuel nozzle assembly  44  depicting the sector nozzles  34  arranged around the center fuel nozzle  46 . The sector nozzles  34  are disposed adjacent to one another to form a generally circular cross section. For example, each shell  56  and housing  76  ( FIG. 3 ) may be disposed proximate to a shell  56  and housing  76  of an adjacent sector nozzle  34 . Each face plate  66  of the sector nozzle  34  includes the apertures  80  that receive ends of the mixing tubes  48  and the aperture  90  that receives the nozzle portion  104  of the liquid fuel cartridge  50 . Liquid fuel  113 , or a mixture of liquid fuel, water, and/or air, is sprayed radially outward from the nozzle portion  104 , as generally indicated by the dashed lines. According to certain embodiments, the liquid fuel  113  may mix with the fuel-air mixture exiting the apertures  80 , which may further disperse the liquid fuel  113  into the combustion chamber  36 . 
         [0032]    Each face plate  66  also includes areas  114  that are aligned with the fuel supply passages  68 . These areas  114  are devoid of apertures  80  and corresponding mixing tubes  48  to allow fuel to enter the fuel plenum  58  through the fuel plenum plate  74 , without being directed into a tube end. However, as described further below with respect to  FIG. 7 , in other embodiments, the fuel supply passages  68  may enter the fuel plenum  58  through the housing  76 , and in these embodiments, substantially all of the face plate  66  may include apertures  80  and corresponding mixing tubes  48 . As shown in  FIG. 4 , each sector nozzle  34  includes a liquid fuel cartridge  50 . However, in other embodiments, only one or more of the sector nozzles  34  may include a liquid fuel cartridge  50 . Further, as shown, five sector nozzles  34  are disposed about the center nozzle  46 . However, in other embodiments, any number of sector nozzles  34  may be included within the fuel nozzle assembly  44 . Further, in certain embodiments, the center nozzle  46  may be omitted. Moreover, in yet other embodiments, the type of liquid fuel cartridges  50  employed may vary between sector nozzles  34 . For example, in certain embodiments, one sector nozzle  34  may include a liquid fuel cartridge  50  designed to direct fuel oil into the combustion chamber  36  while another sector nozzle  34  includes a liquid fuel cartridge  50  designed to direct liquid distillate into the combustion chamber  36 . 
         [0033]      FIGS. 5 and 6  depict alternate embodiments of sector nozzles  34  that include apertures  80  for mixing tubes  48  and apertures  90  for liquid fuel cartridges  50 . As shown in  FIG. 4 , the apertures  80  for the mixing tubes  48  are disposed in a generally random arrangement around the aperture  90  for the liquid fuel cartridge  50 . In contrast, as shown in  FIG. 5 , the apertures  80  are aligned radially in a patterned arrangement to form radial flow paths  116  between the apertures  80  for the liquid fuel  113 . The radial flow paths  116  diverge radially outward from the liquid fuel cartridge  50 , and the fuel may flow along the flow paths  116  as indicated by the dashed lines  113 . According to certain embodiments, the liquid fuel  113  may travel along these flow paths  116 , which may facilitate dispersion of the liquid fuel  113  towards the perimeter  118  of the face plate  66 . The face plate  66  also includes a perimeter row  120  of apertures  80  that are offset from the radially aligned apertures  80 . The offset apertures  80  may impede the flow of liquid fuel  113  past the perimeter  118  of the face plate  66 , which may inhibit contact of the liquid fuel  113  with the liner  40 , and accordingly, may reduce hot spots on the liner  40  ( FIG. 2 ). Although the apertures  80  are radially aligned in  FIG. 5 , in other embodiments, the apertures  80  may be disposed in other patterned configurations, such as hexagonal patterns or staggered patterns, among others. 
         [0034]      FIG. 6  depicts an embodiment of a sector nozzle  34  that include multiple liquid fuel cartridges  50 . In particular, the apertures  80  and corresponding mixing tubes  48  are arranged around three liquid fuel cartridges  50 . According to certain embodiments, including multiple liquid fuel cartridges  50  within a sector nozzle  34  may provide more efficient dispersion of the liquid fuel  113  towards the perimeter  118  relative to a single liquid fuel cartridge  50 . In other embodiments, any number of 1, 2, 3, 4, or more liquid fuel cartridges  50  may be included within a sector nozzle  34 . 
         [0035]      FIG. 7  depicts another embodiment of a fuel nozzle assembly  44 . As described above with respect to  FIGS. 1 through 6 , each sector nozzle  34  includes the apertures  80  and corresponding mixing tubes  48  that extend through the housing  76  of the fuel plenum  58 . However, rather than including liquid fuel cartridges  50  in one or more individual sector nozzles  34 , a center fuel nozzle  122  includes the liquid fuel cartridges  50 . In particular, the center fuel nozzle  122  includes an outer housing  124  that contains the liquid fuel cartridges  50 , which are arranged around a central portion  126 . As shown in  FIG. 7 , the central portion  126  includes a swozzle style nozzle that swirls the flow of air to enhance mixing of liquid fuel and air. However, in other embodiments, the central portion  126  may be a micro-mixer style nozzle, or other suitable type nozzle. Each of the liquid fuel cartridges  50  is designed to spray the liquid fuel  113  radially outward in a fan spray pattern toward the sector nozzles  34 . As shown in  FIG. 7 , none of the sector nozzles  34  include a liquid fuel cartridge  50 . However, in other embodiments, one or more liquid fuel cartridges  50  may be included in one or more of the sector nozzles  34  and may be employed in conjunction with the liquid fuel cartridges  50  included within the center fuel nozzle  122 . Further, the apertures  80  and corresponding mixing tubes  48  may be arranged in a random configuration or patterned configuration as described above with respect to  FIGS. 4 through 6 . 
         [0036]    The fuel nozzle assembly  44  also includes fuel supply passages  128  that direct fuel into the fuel plenum  58 . The fuel supply passages  128  are generally similar to the fuel supply passages  68  described above with respect to  FIGS. 1 and 2 . However, rather than directing fuel into the fuel plenum  58  through the fuel plenum plate  74 , the fuel supply passages  128  direct fuel into the fuel plenum  58  through the housing  76 . Accordingly, the apertures  80  and corresponding mixing tubes  48  may be arranged over substantially all of the face plate  66 , and the areas  114  devoid of the apertures  80  may be omitted. According to certain embodiments, the fuel supply passages  128  may be particularly beneficial in the sector nozzle  34  where additional mixing tubes  48  are desired. 
         [0037]      FIG. 8  depicts another embodiment of a sector nozzle  34  that can be employed within the combustor  12  ( FIGS. 1 and 2 ). The sector nozzle  34  shown in  FIG. 8  is generally similar to the sector nozzle  34  described above with respect to  FIG. 3 . However, rather than employing fuel to cool the face plate  66 , the embodiment shown in  FIG. 8  may employ air to cool the face plate  66 . In particular, the sector nozzle  34  includes a housing  130  that encloses a fuel plenum  132  and an air plenum  134 . 
         [0038]    The air plenum  134  is generally defined by an interior plate  136 , the housing  130 , and a cooling plate  138 . The interior plate is disposed generally parallel to the fuel plenum plate  74  and the face plate  66  and divides the interior of the housing  130  into the fuel plenum  132  and the air plenum  134 . The housing  130  includes cooling holes  140  that direct air into the air plenum  134 . The air from the air plenum  134  then flows through openings in the cooling plate  138  to provide cooling to the face plate  66 . 
         [0039]    The fuel plenum  132  is generally defined by the fuel plenum plate  74 , the housing  130 , and the interior plate  136 . The fuel supply passages  68  direct fuel into the fuel plenum  132  where the fuel enters the mixing tubes  48  through the apertures  82 . The mixing tubes  48  extend from the fuel plenum plate  74 , through the fuel plenum  132 , through the interior plate  36  (i.e., through apertures in the interior plate  36 ), through the air plenum  134 , and through the cooling plate  138  (i.e., through apertures in the cooling plate  138 ) to the face plate  66 . As described above with respect to  FIG. 3 , air from the air plenum  62  enters the ends of the mixing tubes  48  to produce the fuel-air mixture that exits the mixing tubes  48  through the apertures  80  in the face plate  66 . The liquid fuel cartridge  50  also extends through the fuel plenum plate  74 , the fuel plenum  132 , the interior plate  136  (i.e., through an aperture in the interior plate  136 ), the air plenum  134 , and the cooling plate  138  (i.e., through an aperture in the cooling plate  138 ) to the face plate  66  where the nozzle portion  104  expels liquid fuel, water, and air through the face plate  166  into the combustion chamber  36  ( FIG. 2 ). 
         [0040]    As shown in  FIG. 8 , the mixing tubes  48  are disposed radially around the liquid fuel cartridge  50 , in a manner similar to that described above with respect to  FIG. 3 . However, in other embodiments, the sector nozzle  34  of  FIG. 8  may be employed in conjunction with other arrangements of the liquid fuel cartridge  50  and the mixing tubes  48 . For example, the mixing tubes  48  may be arranged to form radial flow paths as described above with respect to  FIG. 5 , or multiple liquid fuel cartridges  50  may be included within the sector nozzle  34 , as described above with respect to  FIG. 6 . Further, the sector nozzle  34  shown in  FIG. 8  may be employed in conjunction with the center fuel nozzle  122  described above with respect to  FIG. 7 . 
         [0041]    As discussed above, the sector nozzles described herein may be particularly well suited to fuel nozzle assemblies that include liquid fuel cartridges and mixing tubes for producing a gaseous fuel-air mixture. In certain embodiments, the sector nozzles include liquid fuel nozzles that are disposed within the individual sector nozzles along with the mixing tubes. Further, in other embodiments, the sector nozzles may be arranged around a central nozzle including one or more liquid fuel cartridges. Accordingly, the sector nozzles provide flexibility in that gaseous fuel can be directed through the mixing tubes while liquid fuel can be directed through the liquid fuel cartridges. 
         [0042]    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 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.