Abstract:
Certain embodiments include a first individual sector configured to fit together with a plurality of individual sectors to form a combustor cap assembly of a turbine combustor, wherein the first individual sector is configured to fixedly attach to a first fuel nozzle of a plurality of fuel nozzles, the first individual sector comprises a first substantially enclosed cavity configured to surround the first fuel nozzle, and the first substantially enclosed cavity is configured to receive a cooling air flow.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to gas turbine engines, and, more particularly, to a fuel nozzle in a turbine combustor. 
         [0002]    A gas turbine engine combusts a fuel-air mixture in a combustor, and then drives one or more turbines with the resulting hot combustion gases. In general, fuel and air are mixed and ignited within one or more fuel nozzles of the combustor. Conventional combustion assemblies may include a single cap having a face exposed to a combustion chamber of the combustor. The single cap includes large circular openings to support multiple circular-shaped fuel nozzles. Unfortunately, existing cap design may be susceptible to various weaknesses. For example, combustion dynamics (e.g., flow disturbances, pressure waves, etc.) and high thermal gradients across the single cap can cause cracking and undesirable oscillations within the head end of the combustor. 
       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 turbine combustor having a plurality of fuel nozzles and a combustor cap assembly having a plurality of individual sectors supporting the plurality of fuel nozzles, wherein each sector of the plurality of individual sectors is fixedly attached to a respective fuel nozzle of the plurality of fuel nozzles, and each sector of the plurality of individual sectors has a substantially enclosed cavity surrounding the respective fuel nozzle. 
         [0005]    In a second embodiment, a system includes a first fuel nozzle and a first individual sector configured to fit together with a plurality of individual sectors to form a combustor cap assembly of a turbine combustor, wherein the first individual sector is fixedly attached to the first fuel nozzle, the first individual sector comprises a first substantially enclosed cavity surrounding the first fuel nozzle, and the first substantially enclosed cavity is configured to receive a cooling air flow. 
         [0006]    In a third embodiment, a system includes a first individual sector configured to fit together with a plurality of individual sectors to form a combustor cap assembly of a turbine combustor, wherein the first individual sector is configured to fixedly attach to a first fuel nozzle of a plurality of fuel nozzles, the first individual sector comprises a first substantially enclosed cavity configured to surround the first fuel nozzle, and the first substantially enclosed cavity is configured to receive a cooling air flow. 
     
    
     
       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 of an embodiment of a gas turbine system with a plurality of turbine combustors; 
           [0009]      FIG. 2  is a cross-sectional side view schematic of an embodiment of one of the turbine combustors of  FIG. 1 ; 
           [0010]      FIG. 3  is a perspective view of an embodiment of a turbine combustor fuel nozzle assembly having fuel nozzles with individual sector cap assemblies; 
           [0011]      FIG. 4  is a perspective view of an embodiment of a peripheral fuel nozzle having an individual sector cap assembly; 
           [0012]      FIG. 5  is a cross-sectional axial view of an embodiment of a peripheral fuel nozzle having an individual sector cap assembly, illustrating a mounting arrangement of the individual sector cap assembly to the fuel nozzle; 
           [0013]      FIG. 6  is a schematic, taken within line  6 - 6  of  FIG. 2 , of an embodiment of a turbine combustor, illustrating a peripheral fuel nozzle having an individual sector cap assembly; 
           [0014]      FIG. 7  is a schematic, taken within line  6 - 6  of  FIG. 2  of an embodiment of a turbine combustor, illustrating a peripheral fuel nozzle having an individual sector cap assembly; 
           [0015]      FIG. 8  is a schematic, taken within line  6 - 6  of  FIG. 2 , of an embodiment of a turbine combustor, illustrating a peripheral fuel nozzle having an individual sector cap assembly; 
           [0016]      FIG. 9  is a schematic, taken within line  9 - 9  of  FIG. 6 , of an embodiment of a peripheral fuel nozzle having an individual sector cap assembly; and 
           [0017]      FIG. 10  is a schematic, taken within line  9 - 9  of  FIG. 6 , of an embodiment of a peripheral fuel nozzle having an individual sector cap assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    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. 
         [0019]    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. 
         [0020]    The disclosed embodiments are directed toward a combustor cap assembly for a turbine combustor. More specifically, the disclosed embodiments may include a plurality of individual sector assemblies mounted to respective fuel nozzles of a fuel nozzle assembly. For example, in certain embodiments, the fuel nozzle assembly may have a plurality of peripheral fuel nozzles arranged about a central fuel nozzle. The plurality of peripheral fuel nozzles may each include an individual sector assembly mounted to the respective peripheral fuel nozzle. Further, the individual sector assemblies may have a geometry that enables the individual sector assemblies to abut one another (e.g., adjacent individual sector assemblies), the central fuel nozzle, and a turbine combustor liner surrounding the fuel nozzle assembly. In certain embodiments, the individual sector assemblies may include seals, such as hula seals, to improve the interface (e.g., seal while enabling some movement) between the individual sector assemblies and surrounding components (e.g., adjacent individual sector assemblies, the central fuel nozzle, and the liner of the turbine combustor). In this manner, the individual sector assemblies may form the substantially continuous combustor cap assembly between the fuel nozzle assembly and a combustion chamber of the turbine combustor. 
         [0021]    Additionally, as discussed in detail below, the seals may be configured to provide damping, account for tolerances within the head end of the turbine combustor, and/or reduce air leakage across the combustor cap assembly. Furthermore, the individual sector assemblies may be configured to receive an air flow, such as a high pressure cooling air flow. In this manner, the combustor cap assembly of turbine combustor may achieve improved cooling and reduce undesired effects of combustion dynamics. Additionally, in certain embodiments, the individual sector assemblies may be substantially enclosed, thereby increasing the pressure of the air flow received by each individual sector assembly and further improving the cooling of the combustor cap assembly. 
         [0022]    Turning now to the drawings,  FIG. 1  illustrates a block diagram of an embodiment of a gas turbine system  10 . The system  10  includes a compressor  12 , turbine combustors  14 , and a turbine  16 . The turbine combustors  14  each include a fuel nozzle assembly  18 . The fuel nozzle assembly  18  of each turbine combustor  14  includes fuel nozzles which route a liquid fuel and/or gas fuel, such as natural gas or syngas, into the turbine combustors  14 . As described in detail below, each turbine combustor  14  may include a combustor cap assembly with individual sector assemblies. More specifically, the individual sector assemblies may be mounted to a respective fuel nozzle of the fuel nozzle assembly  18 , and the individual sector assemblies may collectively form the combustor cap assembly. Furthermore, the individual sector assemblies may be configured to receive an air flow to cool the combustor cap assembly. 
         [0023]    The turbine combustors  14  ignite and combust an air-fuel mixture, and then pass hot pressurized combustion gasses  20  (e.g., exhaust) into the turbine  16 . Turbine blades are coupled to a shaft  22 , which is also coupled to several other components throughout the turbine system  10 . As the combustion gases  20  pass through the turbine blades in the turbine  16 , the turbine  16  is driven into rotation, which causes the shaft  22  to rotate. Eventually, the combustion gases  20  exit the turbine system  10  via an exhaust outlet  24 . Further, the shaft  22  may be coupled to a load  26 , which is powered via rotation of the shaft  22 . For example, the load  26  may be any suitable device that may generate power via the rotational output of the turbine system  10 , such as an electrical generator, a propeller of an airplane, and so forth. 
         [0024]    Compressor blades are included as components of the compressor  12 . The blades within the compressor  12  are coupled to the shaft  22 , and will rotate as the shaft  22  is driven to rotate by the turbine  16 , as described above. The rotation of the blades within the compressor  12  compress air from an air intake  28  into pressurized air  30 . The pressurized air  30  is then fed into the fuel nozzle assembly  18  (e.g., fuel nozzles) of the turbine combustors  14 . The fuel nozzles of the fuel nozzle assemblies  18  mix the pressurized air  30  and fuel to produce a suitable mixture ratio for combustion (e.g., a combustion that causes the fuel to more completely burn) so as not to waste fuel or cause excess emissions. As discussed below, in certain embodiments, the pressurized air  30  may also flow to the individual sector assemblies of the combustor cap assembly of each combustor  14  to cool the combustor cap assembly. 
         [0025]      FIG. 2  is a schematic of an embodiment of one of the turbine combustors  14  of  FIG. 1 , illustrating the fuel nozzle assembly  18  having a combustor cap assembly  52  within a head end  54  of the turbine combustor  14 . As described above, the compressor  12  receives air from the air intake  28 , compresses the air, and produces a flow of pressurized air  30  for use in the combustion process within the turbine combustor  14 . As shown in the illustrated embodiment, the pressurized air  30  is received by a compressor discharge  56  that is operatively coupled to the turbine combustor  14 . As indicated by arrows  58 , the pressurized air  30  flows from the compressor discharge  56  towards the head end  54  of the turbine combustor  14 . More specifically, the pressurized air  30  flows through an annulus  60  between a liner  62  and a flow sleeve  64  of the turbine combustor  14  to reach the head end  54 . The pressurized air  30  may reach the head end  54  at a reduced pressure air  31  (e.g., air  31  has a lower pressure than the pressurized air  30 ). As will be appreciated, the pressure of the pressurized air  30  is reduced as it cools (e.g., via impingement) the combustor  14  via impingement holes  59 . 
         [0026]    In certain embodiments, the head end  54  includes an end plate  66  that may support the fuel nozzle assembly  18  depicted in  FIG. 1 . In the illustrated embodiment, the fuel nozzle assembly  18  has multiple fuel nozzles  68 , which may include individual sector assemblies of the combustor cap assembly  52 . A fuel supply  70  provides fuel  72  to the fuel nozzles  68 . Additionally, an air flow path  74  (e.g., air flow path  180  shown in  FIG. 6 ) delivers the pressurized air  30  from the annulus  60  of the turbine combustor  14  to the fuel nozzles  68 . The fuel nozzles  68  combine the pressurized air  30  with the fuel  72  provided by the fuel supply  70  to form an air/fuel mixture. For example, the fuel  72  may be injected into the air flow path  74  by swirl vanes. The air/fuel mixture flows from the air flow path  74  through the combustor cap assembly  52  and into a combustion chamber  76  where the air/fuel mixture is ignited and combusted to form combustion gases (e.g., exhaust). As shown, the combustor cap assembly  52  creates a boundary between the combustion chamber  76  and the fuel nozzles  68 . The combustion gases flow in a direction  78  toward a transition piece  80  of the turbine combustor  14 . The combustion gases pass through the transition piece  80 , as indicated by arrow  82 , toward the turbine  16 , where the combustion gases drive the rotation of the blades within the turbine  16 . 
         [0027]    During the combustion process, the combustor cap assembly  52  may experience stress as combustion occurs. In particular, the pressurized air  30  may be at a temperature, around 300-700° C., which causes thermal expansion of combustor cap assembly  52 . Fuel may be at around 10 to 175° C., thereby causing a thermal expansion of fuel nozzles  68  that is of a lesser magnitude, relative to the thermal expansion of the combustor cap assembly  52 . The fuel nozzles  68  and the combustor cap assembly  52  may be composed of similar or different materials, such as stainless steel, an alloy, or other suitable material. Furthermore, combustion may expose the combustor cap assembly  52  to temperatures ranging from approximately 1000° to 1700° or more Celsius. As a result of exposure to these various temperatures, the combustor cap assembly  52  may experience considerable thermal stresses. As discussed in detail below, segmentation of the combustor cap assembly  52  may provide stress relief that may be caused, for example, by thermal expansion of the different components of the combustor cap assembly  52 . More particularly, the combustor cap assembly  52  may include multiple individual sector assemblies attached or fixed to the fuel nozzles  68  that are configured to receive a cooling air flow  84 , which may be a higher pressure than the pressurized air  31 . As a result, the combustor cap assembly  52  may not include piston rings and/or floating collars. In other embodiments, the cooling air flow  84  may be the pressurized air  31  from the annulus  60  or an air flow from another source. Additionally, the multiple individual sector assemblies may abut one another and the liner  62  of the turbine combustor  14  with hula seals, thereby improving sealing and vibration damping between adjacent fuel nozzles  68  in the fuel nozzle assembly  18  and reducing undesired leakage of pressurized air  30  across the combustor cap assembly  52 . The hula seals between the individual sector assemblies may also allow for misalignment and improved tolerances between the fuel nozzles  68 . 
         [0028]      FIG. 3  is a perspective view of the fuel nozzle assembly  18  and the combustor cap assembly  52 , where the combustor cap assembly  52  includes individual sector assemblies  100 . As mentioned above, the combustor cap assembly  52  is disposed on ends  102  of the fuel nozzles  68 , thereby separating the fuel nozzles  68  from the combustion chamber  76  of the turbine combustor  14 . In the illustrated embodiment, the fuel nozzle assembly  18  includes six fuel nozzles  68 . More specifically, the fuel nozzle assembly  18  includes a central fuel nozzle  104  and five peripheral fuel nozzles  106  disposed about the central fuel nozzle  104 . However, other embodiments of the fuel nozzle assembly  18  may includes other numbers of fuel nozzles  68  (e.g., 4, 5, 7, 8, or more), with peripheral fuel nozzles  106  surrounding the central fuel nozzle  104 . 
         [0029]    As shown, each of the peripheral fuel nozzles  106  of the fuel nozzle assembly  18  includes a respective individual sector assembly  100  disposed about the respective end  102  of each of the peripheral fuel nozzles  106 . Additionally, each of the individual sector assemblies  100  has a similar “pie-shaped” or “wedge-shaped” configuration. In this manner, the individual sector assemblies  100  may collectively form the combustor cap assembly  52 . More specifically, each individual sector assembly  100  disposed about each peripheral fuel nozzle  106  abuts the individual sector assemblies  100  of the peripheral fuel nozzles  106  to which it is adjacent. Additionally, each individual sector assembly  100  abuts the central fuel nozzle  104 . As mentioned above, each individual sector assembly  100  also abuts the liner  62  of the turbine combustor  14 . In this manner, the entire perimeter of each individual sector assembly  100  abuts another surface. Furthermore, the interfaces between each of the individual sector assemblies  100  may include hula seals  108 . That is, the individual sector assemblies  100  may include hula seals  108  to improve the interfaces and contacts between one another. Similarly, the individual sector assemblies  100  may include hula seals  108  to improve the interfaces and contacts with the central fuel nozzle  104 . The hula seals  108  may also provide improved damping and alignment among the fuel nozzles  68  in the fuel nozzle assembly  18 . The hula seals  108  may also allow some movement, thermal expansion, contraction, etc., among the fuel nozzles  68 . Additionally, while the illustrated embodiments show hula seals  108 , other embodiments of the combustor cap assembly  52  may include other types of seals, such as leaf seals, brush seals, metal cloth seals, spring seals, and so forth. 
         [0030]    As discussed in further detail below, each individual sector assembly  100  is configured to receive the cooling air flow  84 . For example, the cooling air flow  84  may be the pressurized air  31  from the air flow path  74  or cooling air from another source, which may be a different (e.g., higher) pressure than the pressurized air  31 . For example, the cooling air flow  84  may be the pressurized air  30  from the compressor discharge  56 . As each individual sector assembly  100  receives the cooling air flow  84 , the cooling air flow  84  passes through respective front plates  112  of the individual sector assemblies  100 . In this manner, the cooling air flow  84  may cool the individual sector assemblies  100  and the combustor cap assembly  52 . By cooling the individual sector assemblies  100  and the combustor cap assembly  52 , the thermal gradient between the combustion chamber  76  and the head end  54  of the turbine combustor  14  may be reduced, which may reduce low cycle fatigue and wear on the fuel nozzle assembly  18  and the fuel nozzles  68 . Additionally, certain embodiments of the fuel nozzle assembly  18  may include a dynamics plate  114 . The dynamics plate  114  is disposed about the fuel nozzle assembly  18  upstream of the combustor cap assembly  52 . As will be appreciated, the dynamics plate  114  may be adjusted along the fuel nozzle assembly  18  to regulate a volume  116  between dynamics plate  114 , the combustor cap assembly  52 , and the liner  62  surrounding the dynamics plate  114 , the combustor cap assembly  52  and the fuel nozzle assembly  18 . As the volume  116  is increased or decreased, the frequencies of combustion dynamics damped or attenuated in the head end  54  of the turbine combustor  14  may be adjusted. 
         [0031]      FIG. 4  is a perspective view of an embodiment of the individual sector assembly  100  mounted to, and disposed about, the end  102  of one of the peripheral fuel nozzles  106 . In certain embodiments, the individual sector assembly  100  may be mounted to the peripheral fuel nozzle  106  by welding joints or other fixed joints. As a result, the individual sector assembly  100  is fixed to the peripheral fuel nozzle  106 . Additionally, when the individual sector assembly  100  and the peripheral fuel nozzle  106  are installed within the turbine combustor  14 , the individual sector assembly  100  may not move relative to the peripheral fuel nozzle  106 . 
         [0032]    As mentioned above, the individual sector assembly  100  has the front plate  112 , which is exposed to the combustion chamber  76  of the turbine combustor  14 . Additionally, the individual sector assembly  100  has sides  120 , which form an outer perimeter of the individual sector assembly  100 . For example, the individual sector assembly  100  includes an inner radial side or surface  122  (e.g., arcuate surface), an outer radial side or surface  124  (e.g., arcuate surface) and lateral sides or surfaces  126  (e.g., converging or diverging surfaces). When the fuel nozzle assembly  18  (e.g., the central fuel nozzle  104  and the peripheral fuel nozzles  106 ) and the combustor cap assembly  52  (e.g., the individual sector assemblies  100 ) are assembled, the respective inner radial surface  122  of each individual sector assembly  100  abuts the central fuel nozzle  104 . Additionally, the lateral surfaces  126  abut respective lateral surfaces  126  of adjacent individual sector assemblies  100 , and the outer radial surface  124  abuts the liner  62  of the turbine combustor  14 . As mentioned above, the sides  120  (e.g., the inner radial surface  122 , the outer radial surface  124 , and the lateral surfaces  126 ) may each include one or more hula seals  108 . The hula seals  108  serve to improve the interface between the sides  120  and the respective surfaces, which abut the sides  120 . In particular, the hula seals  108  provide an improved seal while enabling some movement, such as thermal expansion or contraction. Additionally, the hula seals  108  may provide improved alignment among the fuel nozzles  68  in the fuel nozzle assembly  18 , while also helping to damp vibration associated with combustion dynamics or other sources. 
         [0033]    As mentioned above, the individual sector assembly  100  is configured to receive the cooling air flow  84 , which may be the pressurized air  31  from the air flow path, the pressurized air  30  from the compressor discharge  56 , or other high pressure air flow (e.g., higher pressure than the pressurized air  30 ). More specifically, the outer radial surface  124  of the individual sector assembly  100  may include one or more apertures  128  configured to receive the cooling air flow  84 , in the manner described below. In one embodiment, the cooling air flow  84  flows into a cavity (e.g., cavity  148  shown in  FIG. 5 ) of the individual sector assembly  100  formed by the sides  120 , the front plate  112 , and the peripheral fuel nozzle  106 , as indicated by arrow  130 . Thereafter, the cooling air flow  84  passes through apertures  132  formed in the front plate  112 , as indicated by arrows  134 . In this manner, the cooling air flow  84  may cool the individual sector assemblies  100  and the combustor cap assembly  52 . Additionally, the cooling air flow  84  may flow through the air flow path  74  and into the volume  116 , from where the cooling air flow  84  may enter the cavity of the individual sector assembly  100  from a back side  135  (e.g., a side opposite the front plate  112 ) of the individual sector assembly  100 . By cooling the individual sector assemblies  100  and the combustor cap assembly  52 , the thermal gradient between the combustion chamber  76  and the head end  54  of the turbine combustor  14  may be reduced, which may reduce thermal stress and wear on the fuel nozzle assembly  18  and the fuel nozzles  68 . 
         [0034]    Furthermore, in certain embodiments, the individual sector assembly  100  may include a back plate  136  (e.g., opposite the front plate  112 ). The addition of the back plate  136  may substantially enclose the cavity of the individual sector assembly  100 . In this manner, the pressure of the cooling air flow  84  passing through the apertures  132  of the front plate  112  may increase, thereby increasing the pressure drop across the front plate  112 . As will be appreciated, elevated pressure of the cooling air flow  84  passing through the apertures  132  of the front plate  112  may help reduce the effects of combustion dynamics produced within the combustion chamber  76  of the turbine combustor  14 . Additionally, the elevated pressure of the cooling air flow  84  within the individual sector assembly  100  may increase the flow rate of the cooling air flow  84  through the apertures  132  of the front plate  112 , thereby increasing the cooling and reducing thermal stress of the individual sector assemblies  100  and the combustor cap assembly  52 . 
         [0035]      FIG. 5  is a cross-sectional axial view of an embodiment of the peripheral fuel nozzle  106  with the individual sector assembly  100 , illustrating a mounting arrangement of the individual sector assembly  100  to the peripheral fuel nozzle  106 . Additionally, the illustrated embodiment show a cavity  148  formed by the individual sector assembly  100  and the peripheral fuel nozzle  106  into which the cooling air flow  84  may flow (e.g., from the air flow path  74 ). The individual sector assembly  100  is mounted to the peripheral fuel nozzle  106  by several brackets  150 . In the illustrated embodiment, the brackets  150  have an A-shaped configuration. However, other embodiments may include brackets  150  having other configurations. 
         [0036]    As shown, a first bracket  152  couples the inner radial surface  122  of the individual sector assembly  100  to the peripheral fuel nozzle  106 . Similarly, a second bracket  154  couples the outer radial surface  124  of the individual sector assembly  100  to the peripheral fuel nozzle  106 , a third bracket  156  couples one of the lateral surfaces  126  of the individual sector assembly  100  to the peripheral fuel nozzle  106 , and a fourth bracket  158  couples another lateral surface  126  of the individual sector assembly  100  to the peripheral fuel nozzle  106 . As mentioned above, the individual sector assembly  100  is fixedly attached to the peripheral fuel nozzle  106 . For example, each of the brackets  150  may be secured to the peripheral fuel nozzle  106  and the respective side  120  of the individual sector assembly  100  by weld joints  160 . In other embodiments, the brackets  150  may be secured to the peripheral fuel nozzle  106  by other methods such as brazed joints, bolts, rivets, and so forth. Because the individual sector assembly  100  is fixedly attached to the peripheral fuel nozzle  106 , the combustor cap assembly  52  may not include piston rings and/or floating collars. In other words, the individual sector assembly  100  does not move or float relative to its supported fuel nozzle  106 . 
         [0037]      FIG. 6  is a schematic of an embodiment of the individual sector assembly  100  mounted to the peripheral fuel nozzle  106  and installed within the head end  54  of the turbine combustor  14 . Specifically, the illustrated embodiment shows the front plate  112  of the individual sector assembly  100  coupled to the peripheral fuel nozzle  106  and the outer radial surface  124  interfacing with the liner  62  of the turbine combustor  14 . As mentioned above, the cooling air flow  84  (e.g., pressurized air  30 , pressurized air  31 , or other air flow) flows into the cavity  148  of the individual sector assembly  100  and subsequently passes through the apertures  132  of the front plate  112 , thereby cooling the individual sector assembly  100 , the combustor cap assembly  52 , and the peripheral fuel nozzle  106 . As described below, the cooling air flow  84  may flow into the cavity  148  of the individual sector assembly  100  through various paths (e.g., through air flow path  180 , gap  217 , and volume  218 , through the air inlet  214 , and so forth). 
         [0038]    As mentioned above, in operation, the peripheral fuel nozzle  106  (e.g., fuel nozzle  68 ) combines the pressurized air  31  from the annulus  60  with the fuel  72  provided by the fuel supply  70  to form an air/fuel mixture for combustion within the combustion chamber  76  of the turbine combustor  14 . For example, the peripheral fuel nozzle  106  may received the pressurized air  31  from an air flow path  180  operatively coupled to the annulus  60  between the liner  62  and the flow sleeve  64  of the turbine combustor  14 . As shown, the air flow path  180  contains a first portion  182  and a second portion  184 , and the first portion  182  and the second portion  184  are operatively coupled. The first portion  182  of the air flow path  180  is defined by an outer wall  186  (e.g, a head end casing) and an inner wall  188  (e.g., a head end sleeve) of the turbine combustor  14 . The second portion  184  of the air flow path  180  is defined by an outer shell  190  (e.g., a burner tube of the fuel nozzle  68 ,  106 ) and an inner shell  192  (e.g., a central fuel supply conduit) of the peripheral fuel nozzle  106 . As indicated by arrows  194 , the pressurized air  31  flows from the annulus  60 , first through the first portion  182  of the air flow path  180  in an upstream direction, and then through the second portion  184  of the air flow path  180  in a downstream direction. Subsequently, the pressurized air  31  flows around swirl vanes  196  of the peripheral fuel nozzle  106 . As mentioned above, the fuel  72  is released into the pressurized air  31  through the swirl vanes  196 . Specifically, the fuel  72  flows down a fuel path  198  within the inner shell  192  (e.g., central fuel supply conduit) of the peripheral fuel nozzle  106 , as represented by arrows  200 . The fuel  72  passes into the swirl vanes  196  from the fuel path  198 , as represented by arrows  202 , and exits the swirl vanes  196  through fuel ports  204  in the swirl vanes  196 , as represented by arrows  206 . The fuel  72  mixes with the pressurized air  31  to create an air/fuel mixture. The air/fuel mixture flows downstream, as indicated by arrows  208 , toward the combustion chamber  76 . 
         [0039]    As mentioned above, the individual sector assembly  106  of the combustor cap assembly  52  is coupled to the peripheral fuel nozzle  106  of the fuel nozzle assembly  18 . As shown, the individual sector assembly  100  may receive the cooling air flow  84 , represented by arrows  209 , from a cooling air flow path  210 . For example, in the illustrated embodiment, the cooling air flow path  210  is formed by the flow sleeve  64  of the turbine combustor  14  and a casing  212  of the turbine combustor  14 . As mentioned above, the cooling air flow  84  may be the pressurized air  30  supplied by the compressor discharge  54 . In other embodiments, the cooling air flow  84  may be supplied by another source. Furthermore, the cooling air flow  84  may have a higher pressure than the pressurized air  31  flowing through the liner  62  and the flow sleeve  64  (e.g., represented by arrows  194 ). 
         [0040]    The cooling air flow  84 , represented by arrows  209 , enters the cavity  148  of the individual sector assembly  100  through the aperture  128  in the outer radial surface  124  and from a cooling air inlet  214  operatively coupled to the cooling air flow path  210 . While the illustrated embodiment shows a single cooling air inlet  214 , other embodiments may include more cooling air inlets  214 . For example, the individual sector assembly  100  may have 2, 3, 4, 5, 6, 7, 8, or more cooling air inlets  214 . Similarly, other individual sector assemblies  100  of the combustor cap assembly  52  may include a single or multiple cooling air inlets  214  configured to flow the cooling air flow  84  into the respective cavity  148  of each individual sector assembly  100 . The cavity  148  receives the cooling air flow  84 , represented by arrows  209 , from the cooling air inlet  214  and directs the cooling air flow  84  in an upstream direction towards the front plate  112  of the individual sector assembly  100 , as indicated by arrow  216 . Moreover, the cooling air  84  is directed toward the apertures  132  in the front plate  112 . In the illustrated embodiment, the apertures  132  are straight holes. However, as discussed below, other embodiments of the front plate  112  may have apertures  132  that are angled holes. As the cooling air flow  84  passes through the apertures  132 , the air flow  84  helps to cool the front plate  112 , the individual sector assembly  100  and the combustor cap assembly  52 . 
         [0041]    In the illustrated embodiment, the cavity  148  of the individual sector assembly  100  may also receive the pressurized air  31  flowing through the air flow path  180 , as mentioned above. Specifically, the pressurized air  31  may flow through the gap  217  between the outer shell  190  (e.g., burner tube) of the peripheral fuel nozzle  106  and the inner wall  188  (e.g., a head end sleeve) and into the volume  218 , as represented by arrows  220 . From the volume  218 , the pressurized air  30 , represented by arrow  220 , may pass into the cavity  148  of the individual sector assembly  100 . As mentioned above, the head end  54  of the turbine combustor  14  may include the dynamics plate  114 . As shown, the dynamics plate  114  is disposed between the outer shell  190  (e.g., burner tube) of the peripheral fuel nozzle  106  and the inner wall  188  (e.g., a head end sleeve), and may be moved to adjust the size of the volume  218 . As the size of the volume  218  is adjusted, the frequencies of vibrations and pressure fluctuations damped within the head end  54  of the turbine combustor  14  may be changed. 
         [0042]    As mentioned above, the individual sector assembly  100  is rigidly attached to the peripheral fuel nozzle  106 . Specifically, an inner perimeter  223  of the individual sector assembly  100  is fixedly attached to the outer shell  190  (e.g., burner tube) of the peripheral fuel nozzle  106 . In the illustrated embodiment, the inner perimeter  223  is secured to the outer shell  190  by a weld joint  224 . As will be appreciated, multiple weld joints  224  may be used to secure the inner perimeter  223  to the outer shell  190 . In other embodiments, the inner perimeter  223  may be fixedly attached to the outer shell  190  of the peripheral fuel nozzle  106  by other methods, such as the brackets  150 , brazing, bolting, riveting, etc. 
         [0043]    Additionally, hula seals  108  are disposed between the individual sector assembly  100  and the liner  62  and the outer wall  188  of the turbine combustor  14 . The hula seals  108  serve multiple functions. For example, the hula seals  108  may substantially block the pressurized air  31  and/or the cooling air flow  84  from leaking between the individual sector assembly  100 , the liner  62 , and the outer wall  186  and into the combustion chamber  76 . Additionally, the hula seals  108  may allow for less stringent tolerances and misalignment of the fuel nozzle assembly  18  and the combustor cap assembly  52  within the head end  54  of the turbine combustor  14 . In other words, the hula seals  108  may enable some movement, such as thermal expansion and/or contraction, of the fuel nozzles  68 . Furthermore, the hula seals  108  may enable improved damping of vibration associated with combustion dynamics among the fuel nozzles  68  and within the head end  54  of the turbine combustor. Indeed, the spring rate of the hula seals  108  may be selected to adjust damping among the fuel nozzles  68  and within the head end  54  of the turbine combustor  14 . Furthermore, the hula seals  108  may simplify the installation of the fuel nozzle assembly  18  and the combustor cap assembly  52 . 
         [0044]    In the illustrated embodiment, the outer radial surface  124  of the individual sector assembly  100  includes a first hula seal  108 ,  226 . As shown, the first hula seal  226  is configured to interface with the inner wall  188  (e.g., head end sleeve) of the turbine combustor  14 . Similarly, the liner  62  of the turbine combustor  14  includes a second hula seal  108 ,  228  (e.g., an inverted hula seal) configured to interface with the outer radial surface  124  of the individual sector assembly  100 . However, in other embodiments, the inner wall  188  of the turbine combustor  14  may include the hula seal  108 ,  226  (e.g., an inverted hula seal) configured to interface with the outer radial surface  124  of the individual sector assembly  100 . Similarly, in certain embodiments, the outer radial surface  124  of the individual sector assembly  100  may include the hula seal  108 ,  228  configured to interface with the liner  62  of the turbine combustor  14 . 
         [0045]      FIG. 7  is a schematic of an embodiment of the individual sector assembly  100  mounted to the peripheral fuel nozzle  106  and installed within the head end  54  of the turbine combustor  14 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 6 . However, in the illustrated embodiment, the cavity  148  of the individual sector assembly  100  receives the pressurized air  31 , represented by arrows  194 , as the cooling air flow  84 . In other words, the individual sector assembly  100  does not receive the cooling air flow  84  from the cooling air inlet  214  (e.g., where the cooling air flow  84  is the pressurized air  30  or other air flow). For example, the pressurized air  31  may reach the cavity  148  of the individual sector assembly  100  by flowing from the annulus  60 , through the air flow path  180 , through the gap  217 , through the volume  218 , and into the cavity  148  through the back side  135  of the individual sector assembly  100 , as discussed in detail above. 
         [0046]    Additionally, or alternatively, the pressurized air  31  may flow into the cavity  148  through the aperture  128  of the outer radial surface  124  of the individual sector assembly  100 . That is, the pressurized air  31  may flow into the cavity  148  through the aperture  128  of the outer radial surface  124  instead of, or in addition to, the pressurized air  31  passing through the air flow path  180 , the gap  217 , and the volume  218  to reach the back side  135  of the individual sector assembly  100 . As shown, the pressurized air  31  may pass through an aperture  222  in the liner  62 , as indicated by arrow  221 . In some embodiments, the aperture  222  may be formed in the inner wall  188  (e.g., head end sleeve) of the turbine combustor  14 . However, other embodiments of the turbine combustor  14  may not include the aperture  222 . Furthermore, the illustrated embodiment of the individual sector assembly  100  includes one hula seal  108 . Specifically, the individual sector assembly  100  includes the second hula seal  228 , but not the first hula seal  226  shown in  FIG. 6 . 
         [0047]      FIG. 8  is a schematic of an embodiment of the individual sector assembly  100  mounted to the peripheral fuel nozzle  106  and installed within the head end  54  of the turbine combustor  14 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 6 . Additionally, the illustrated embodiment of the individual sector assembly  100  includes the back plate  136 , which may be secured to the outer shell  190  (e.g., burner tube) of the peripheral fuel nozzle  106  by a weld joint  240 . In this manner, the cavity  148  of the individual sector assembly  100  is substantially enclosed and/or sealed relative to the fuel nozzle  68 ,  106 . That is, the cavity  148  is substantially enclosed by the front plate  112 , the back plate  136 , the lateral sides  126 , the outer radial surface  124 , the inner radial surface  122 , and the outer shell  190  (e.g., burner tube) of the peripheral fuel nozzle  106 . As a result, the elevated pressure of the cooling air flow  84  may be maintained or increased within the individual sector assembly  100 . As mentioned above, the cooling air flow  84  may have a pressure higher than the pressurized air  30  flowing through the annulus  60  and the air flow path  180 . As a result, the substantially enclosed individual sector assembly  100  may block the pressurized air  30  (e.g., flowing within the volume  218 , as described above) from mixing with the higher pressure cooling air flow  84  within the cavity  148 . In this manner, the cooling air flow  84  may maintain an elevated pressure within the individual sector assembly  100 , thereby providing improved cooling of the combustor cap assembly  52  and the fuel nozzle assembly  18  and increasing the pressure drop across the front plate  112  of the individual sector assembly  100 . 
         [0048]      FIGS. 9 and 10  are schematics of embodiments of the front plate  112  of the individual sector assembly  100  mounted to the peripheral fuel nozzle  106 . For example,  FIG. 9  illustrates the front plate  112  of the individual sector assembly  100 , where the apertures  132  in the front plate  112  are angled holes. In certain embodiments, the front plate  112  having apertures  132 , which are angled holes, may act as an effusion plate.  FIG. 10  illustrates an embodiment of the individual sector assembly  100  having two front plates  112  (e.g., a first front plate  280  and a second front plate  282 ). As shown, each of the two front plates  112  has the apertures  132  configured to flow the cooling air flow  84 , represented by arrows  270 , from the cavity  148  to the combustion chamber  76 , as indicated by arrows  134 . For example, the first front plate  280  may be an impingement plate and the second front plate  282  may be an effusion plate. That is, the first front plate  280  may impinge the cooling air flow  84 , represented by arrows  270 , on the second front plate  282 . 
         [0049]    As described in detail above, the disclosed embodiments are directed towards the combustor cap assembly  52  for the turbine combustor  14 . More specifically, the disclosed embodiments include a plurality of individual sector assemblies  100  mounted to fuel nozzles  68  of the fuel nozzle assembly  18 . For example, in certain embodiments, the fuel nozzle assembly  18  includes peripheral fuel nozzles  106  arranged about the central fuel nozzle  104 . The peripheral fuel nozzles  106  may each include the individual sector assembly  100  mounted to the respective peripheral fuel nozzle  106 . Further, the individual sector assemblies  100  may have a geometry that enables an entire outer perimeter of the individual sector assemblies  100  to abut one another (e.g., adjacent individual sector assemblies  100 ), the central fuel nozzle  106 , and the liner  62  surrounding the fuel nozzle assembly  18 . In certain embodiments, the individual sector assemblies  100  further include hula seals  108  to improve the interface between the individual sector assemblies  100  and surrounding components (e.g., adjacent individual sector assemblies  100 , the central fuel nozzle  106 , and the liner  62  of the turbine combustor  14 ). In this manner, the individual sector assemblies  100  may form the substantially continuous combustor cap assembly  52  between the fuel nozzle assembly  18  and the combustion chamber  76  of the turbine combustor  14 . Additionally, the hula seals  108  may be configured to provide damping, account for tolerances within the head end  54  of the turbine combustor  14 , allow movement, e.g., thermal expansion or contraction, of the fuel nozzles  68 , and/or reduce air leakage across the combustor cap assembly  52 . Furthermore, the individual sector assemblies  100  are configured to receive a cooling air flow  84 , which may be a high pressure cooling air flow. For example, the cooling air flow  84  may be pressurized air  31  from an annulus  60  between a liner  62  and flow sleeve  64  of the combustor  14 , or pressurized air  30  from a compressor discharge case  56 . In this manner, the combustor cap assembly  52  of turbine combustor  14  may achieve improved cooling and reduce undesired effects of combustion dynamics. Additionally, in certain embodiments, the individual sector assemblies  100  may be substantially enclosed, thereby increasing the pressure of the cooling air flow  84  received by each individual sector assembly  100  and further improving the cooling of the combustor cap assembly  52 . 
         [0050]    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.