Patent Publication Number: US-2022228744-A1

Title: Cmc combustor deflector

Description:
FIELD 
     The present subject matter relates generally to combustion assemblies of gas turbine engines. More particularly, the present subject matter relates to combustor deflectors of combustion assemblies. 
     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, which includes a combustor defining a combustion chamber. Fuel is mixed with the compressed air and burned within the combustion chamber to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere. 
     Typically, the combustor includes a combustor dome at its forward end, and one or more combustor deflectors are positioned within the combustion chamber just aft of the combustor dome, e.g., to protect the combustor dome from the combustion gases. However, the combustor deflectors usually are made of metal, which may limit engine operating temperatures and may sustain damage such as metal oxidation and chipping of a thermal barrier coating (TBC) applied to the deflector. In some instances, cracked metal deflectors may liberate and damage airfoils and/or other engine components. Thus, metal combustor deflectors may frequently cause unscheduled engine removal and maintenance. 
     More commonly, non-traditional high temperature materials, such as ceramic matrix composite (CMC) materials, are being used in gas turbine applications. Components fabricated from such materials have a higher temperature capability compared with typical components, e.g., metal components, which may allow improved component performance and/or increased engine temperatures. Accordingly, using high temperature materials for combustor deflectors may improve the durability of the deflectors, as well as allow reduction of impingement cooling or other types of cooling of the deflectors, which may improve engine performance. Therefore, combustor deflectors that overcome one or more disadvantages of existing designs would be desirable. In particular, a CMC combustor deflector would be beneficial. Additionally, a combustor assembly having one or more CMC combustor deflectors would be useful. Further, methods of assembling combustor assemblies having CMC combustor deflectors would be advantageous. 
     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 combustor dome assembly having a forward side and an aft side is provided. The combustor dome assembly comprises a combustor dome defining an opening; a ceramic matrix composite (CMC) deflector positioned adjacent the combustor dome on the aft side of the combustor dome assembly; a fuel-air mixer defining a groove about an outer perimeter of the fuel-air mixer; and a seal plate including a key. The CMC deflector includes a cup extending forward through the opening in the combustor dome, and the cup defines one or more bayonets and a slot. The bayonets are received in the groove of the fuel-air mixer, and the seal plate key is received in the slot of the CMC deflector. 
     In another exemplary embodiment of the present disclosure, a combustor dome assembly having a forward side and an aft side is provided. The combustor dome assembly comprises a combustor dome defining an opening; a ceramic matrix composite (CMC) deflector positioned adjacent the combustor dome on the aft side of the combustor dome assembly; and a fuel-air mixer positioned adjacent the combustor dome of the forward side of the combustor dome assembly. A spring is positioned between the fuel-air mixer and the CMC deflector to hold the CMC deflector in place with respect to the combustor dome. 
     In a further exemplary embodiment of the present disclosure, a method of assembling a combustor dome assembly is provided. The combustor dome assembly has a forward side and an aft side. The method comprises assembling a combustor dome with a combustor; inserting a seal plate from the forward side of the assembly; attaching the seal plate to the combustor dome; inserting a CMC deflector from an aft side of the assembly, the CMC deflector having one or more bayonets; inserting a fuel-air mixer from a forward side of the assembly, the fuel-air mixer defining a groove for receipt of the one or more bayonets; rotating the fuel-air mixer to engage the bayonets; and attaching the fuel-air mixer to the seal plate. 
     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  provides a schematic cross-section view of an exemplary gas turbine engine according to various embodiments of the present subject matter. 
         FIG. 2  provides a perspective view of a portion of a combustor dome assembly according to an exemplary embodiment of the present subject matter. 
         FIG. 3  provides a perspective cross-section view of the combustor dome assembly of  FIG. 2  according to an exemplary embodiment of the present subject matter. 
         FIG. 4  provides a forward side, perspective view of a CMC combustor deflector according to an exemplary embodiment of the present subject matter. 
         FIG. 5  provides a forward side, perspective view of a portion of the combustor dome assembly of  FIG. 3 . 
         FIG. 6  provides a cross-section view of a portion of the combustor dome assembly of  FIG. 3 . 
         FIG. 7  provides a cross-section view of the portion of the combustor dome assembly of  FIGS. 3 and 6  according to another exemplary embodiment of the present subject matter. 
         FIGS. 8 through 13  provide cross-section views of a portion of the combustion dome assembly of  FIG. 2  according to other exemplary embodiments of the present subject matter. 
         FIG. 14  provides a flow diagram illustrating a method of assembling a combustor dome assembly according to an exemplary embodiment of the present subject matter. 
     
    
    
     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 “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. 
     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) and a radial direction R. 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 . 
     For the depicted embodiment, fan section  14  includes a fan  38  having a plurality of fan blades  40  coupled to a disk  42  in a spaced apart manner. As depicted, fan blades  40  extend outward from disk  42  generally along the radial direction R. The fan blades  40  and disk  42  are together rotatable about the longitudinal axis  12  by LP shaft  36 . In some embodiments, a power gear box having a plurality of gears may be included 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 , 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 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 turbofan  10  through an associated inlet  60  of the nacelle  50  and/or fan section  14 . As the volume of air  58  passes across 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 arrows  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 and burned to provide combustion gases  66 . 
     The combustion gases  66  are routed 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 . 
     In some embodiments, components of turbofan engine  10 , particularly components within hot gas path  78 , may comprise a ceramic matrix composite (CMC) material, which is a non-metallic material having high temperature capability. Exemplary CMC materials utilized for such components may include silicon carbide (SiC), silicon, silica, or alumina matrix materials and combinations thereof. Ceramic fibers may be embedded within the matrix, such as oxidation stable reinforcing fibers including monofilaments like sapphire and silicon carbide (e.g., Textron&#39;s SCS-6), as well as rovings and yarn including silicon carbide (e.g., Nippon Carbon&#39;s NICALON®, Ube Industries&#39; TYRANNO®, and Dow Corning&#39;s SYLRAIMIC®), alumina silicates (e.g., Nextel&#39;s 440 and 480), and chopped whiskers and fibers (e.g., Nextel&#39;s 440 and SAFFIL®), and optionally ceramic particles (e.g., oxides of Si, Al, Zr, Y, and combinations thereof) and inorganic fillers (e.g., pyrophyllite, wollastonite, mica, talc, kyanite, and montmorillonite). For example, in certain embodiments, bundles of the fibers, which may include a ceramic refractory material coating, are formed as a reinforced tape, such as a unidirectional reinforced tape. A plurality of the tapes may be laid up together (e.g., as plies) to form a preform component. The bundles of fibers may be impregnated with a slurry composition prior to forming the preform or after formation of the preform. The preform may then undergo thermal processing, such as a cure or burn-out to yield a high char residue in the preform, and subsequent chemical processing, such as melt-infiltration with silicon, to arrive at a component formed of a CMC material having a desired chemical composition. In other embodiments, the CMC material may be formed as, e.g., a carbon fiber cloth rather than as a tape. 
     As stated, components comprising a CMC material may be used within the hot gas path  78 , such as within the combustion and/or turbine sections of engine  10 . However, CMC components may be used in other sections as well, such as the compressor and/or fan sections. As a particular example described in greater detail below, a deflector for a combustor dome may be formed from a CMC material, e.g., to provide greater temperature capability of the deflector to better protect the dome from the temperature of combustion gases and/or to reduce cooling of the deflector. 
     Turning to  FIG. 2 , a perspective view is provided of a portion of a combustor dome assembly  100  according to an exemplary embodiment of the present subject matter. As shown in  FIG. 2 , the exemplary combustor dome assembly  100  has a forward side  102  and an aft side  104 . Further, the combustor dome assembly  100  includes a generally annular combustor dome  106  and a plurality of combustor deflectors  108  positioned adjacent the aft side  104 . As will be generally understood, the combustion section  26  includes a combustor (not shown) that defines a combustion chamber (not shown) in which the fuel is burned to provide combustion gases  66 . Each deflector  108  includes a body  109  configured to help shield the combustor dome  106 , e.g., from the heat of the combustion gases  66 . 
     The combustor dome  106  generally is positioned at a forward end of the combustor and defines a plurality of openings  110  ( FIG. 3 ). Each deflector  108  defines an opening  112  ( FIG. 4 ) that aligns with a dome opening  110 . A fuel-air mixer  114  is positioned through each dome opening  110  and deflector opening  112 ; the fuel-air mixers  114  provide a mixture of fuel and air to the combustion chamber located immediately downstream of the combustor dome assembly  100 . As described in greater detail herein, each mixer  114  helps retain its respective deflector  108  within the dome opening  110 . 
       FIG. 3  provides a perspective cross-section view of the combustor dome assembly  100  of  FIG. 2  according to an exemplary embodiment of the present subject matter. As depicted in  FIG. 3 , the combustor dome assembly  100  further comprises a seal plate  116  that helps retain the deflector  108  within the dome opening  110 , as described in greater detail below.  FIG. 3  also illustrates that the deflector  108  defines at least one projection or bayonet  118 , which fits within a groove  120  defined in an outer perimeter of an aft end  122  of the mixer  114 . The bayonet(s)  118  and groove  120  thus form a bayonet joint, which couples the deflector  108  and the mixer  114 . Further, in the depicted embodiment, the mixer  114  defines a slot  124  corresponding to each bayonet  118 , i.e., each slot  124  is configured for the passage of a bayonet  118  therethrough during assembly of the mixer  114  with the deflector  108 . After the bayonets  118  pass through the slots  124 , the mixer  114  may be twisted or rotated such that the bayonets  118  are no longer aligned with the slots  124 , thereby retaining the bayonets  118  in the groove  120  of the mixer  114 . In an exemplary embodiment, the deflector  108  includes three bayonets and the mixer  114  defines three slots  124  (one slot  124  for each bayonet  118 ), but the deflector  108  and mixer  114  may include any suitable number and configuration of bayonets  118  and slots  124 , respectively. Further, in some embodiments, a key may be attached, e.g., welded, within each mixer slot  124 , e.g., to fill the slot and avoid leakage and/or aerodynamic effects that could result from the slots  124 . In other embodiments, as appropriate, the mixer  114  may define the bayonets and the deflector  108  may define the groove. 
       FIG. 3  further illustrates that the aft end  122  of the mixer  114  is positioned within the dome opening  110  and the deflector opening  112 . Moreover, the aft end  122  generally flares outward from a generally cylindrical midsection  126  to form a flare cone  128 . Additionally, an opening  130  defined through mixer  114 , e.g., for the passage of a fuel-air mixture from the mixer  114  to the combustion chamber, that is aligned with the dome opening  110  and the deflector opening  112 . The mixer  114  further defines an axial mixer centerline M CL , which generally extends axially through the mixer opening  126 , but need not be parallel to the engine centerline  12 , e.g., as shown in  FIG. 6 , the mixer centerline is at an angle of approximately 30 degrees to the engine centerline. 
     Referring now to  FIG. 4 , a forward side, perspective view is provided of a combustor deflector  108  according to an exemplary embodiment of the present subject matter. The deflector  108  has a forward side  132  and an aft side  134 . A cup  136  projects forwardly from the forward side  132  and defines the deflector opening  112 . As such, the cup  136  extends forward through the dome opening  110  when the deflector  108  is positioned adjacent the combustor dome  106  as shown in  FIG. 3 . The deflector cup  136  may be generally cylindrical as illustrated in  FIG. 4 , but the cup  136  may have different shapes or configurations in other embodiments. 
     Further, the cup  136  defines a slot  138 . As shown in  FIG. 5 , which provides a forward side, perspective view of a portion of the combustor dome assembly  100  of  FIG. 3 , the seal plate  116  includes a key  140  that is received within the slot  138  defined by the deflector cup  136 . The key  140  and slot  138  thereby form a tongue and groove joint that helps prevent rotational movement of the deflector  108 . In some embodiments, the deflector  108  may include the key  140  and the seal plate  116  may define the slot  138 . 
     As further illustrated in  FIGS. 3 and 5 , the seal plate  116  is positioned adjacent the forward side  102  of the combustor dome assembly  100 . The seal plate  116  includes a generally annular wall  142  that extends aft through the opening  110  in the combustor dome  106  and defines an opening through the seal plate  116 . The wall  142  is positioned between the combustor dome  106  and the cup  136  of the deflector  108 . As such, the deflector cup  136  is positioned within the seal plate opening. 
     Turning to  FIG. 6 , a cross-section view is provided of a portion of the combustor dome assembly  100  of  FIG. 3 . In the depicted embodiment, each of the combustor dome  106 , mixer  114 , and seal plate  116  are formed from a metallic material, such as a metal or metal alloy. To help retain the mixer  114  and seal plate  116  in the assembly  100 , the seal plate  116  is attached to the combustor dome  106 , e.g., by welding or brazing, as generally indicated at area W/B in  FIG. 6 , and the mixer  114  is attached to the seal plate  116 , e.g., by welding or brazing, as generally shown at area W/B in  FIG. 6 . As previously described, the deflector  108  preferably is formed from a CMC material such that the deflector is a CMC deflector  108 . The CMC deflector  108  is retained in the assembly  100  by the bayonet joint between the CMC deflector  108  and the mixer  114  and the tongue and groove joint between the CMC deflector  108  and the seal plate  116 . Further, during operation of the engine  10 , a pressure differential from the forward side  102  to the aft side  104  presses the CMC deflector  108  aft and against the mixer  114 , which helps axially retain the deflector  108 . Additionally, a coating C, such as an environmental barrier coating (EBC) or thermal barrier coating (TBC), may be applied to the deflector  108 , e.g., to help protect the deflector during operation of engine  10 . 
     Moreover, it will be appreciated that the metallic components, e.g., the combustor dome  106 , mixer  114 , and seal plate  116 , have a different rate of thermal expansion than the CMC deflector  108 . More particularly, the metallic components will grow faster than the CMC deflector  108  and will begin to thermally expand at lower temperatures than the CMC deflector  108 . As such, under cold, non-operating engine conditions the seal plate opening defined by the wall  142  is sized to receive the deflector cup  136 , and the deflector opening  112  is sized to receive the mixer  114 . A gap may be defined between an inner diameter of the deflector cup  136  and an outer diameter of the mixer  114  such that the mixer  114  has room to grow as the engine temperatures increase. For example, at hot, operating engine conditions, the inner diameter of the deflector cup  136  may be supported by the outer diameter of the mixer  114 . Thus, the sizing of the various components may help radially retain the CMC deflector  108  under cold and hot engine conditions. 
       FIG. 7  provides a cross-section view of the portion of the combustor dome assembly  100  of  FIGS. 3 and 6  according to another exemplary embodiment of the present subject matter. Similar to the embodiment shown in  FIGS. 3 and 6 , the deflector  108  illustrated in  FIG. 7  includes at least one bayonet  118 , which is received within the groove  120  defined in the outer perimeter of the aft end  122  of mixer  114 . However, unlike the previous embodiment of assembly  100 , the deflector  108  also includes at least a portion of the flare cone  128  that is shown as part of the mixer  114  in the embodiment of  FIGS. 3 and 6 . Thus, where the deflector  108  is a CMC deflector, the flare cone  128  included with the deflector  108  also is made from a CMC material. As such, the CMC flare cone  128  may help protect the metallic mixer  114  from the temperatures within the combustion chamber. Additionally, the flare cone  128  of the CMC deflector  108  covers the mixer slots  124  on the aft side  104  of the combustor dome assembly  100 , such that the flare cone  128  shields the mixer  114  from the combustion temperatures as well as helps prevent combustion gas leakage through the mixer slots  124 . 
     As further illustrated in  FIG. 7 , the mixer  114  defines a pocket  146 , and a washer or spring  148 , such as a Belleville washer or the like, is received within the pocket  146 . The spring  148  is positioned between the mixer  114  and the CMC deflector  108  to hold the deflector in place with respect to the combustor dome  106 . More particularly, the spring  148  presses against a forward edge  150  of the deflector cup  136  to axially load the deflector  108  into the mixer  114  and thereby to help hold the deflector  108  in place axially. Further, as described above with respect to  FIG. 6 , the seal plate  116  may be attached to the combustor dome  106  and the mixer  114  attached to the seal plate  116 , where the seal plate  116  and mixer  114  are attached by welding, brazing, or the like. 
       FIGS. 8 through 13  provide cross-section views of a portion of the combustion dome assembly  100  according to other exemplary embodiments of the present subject matter. Referring to  FIG. 8 , in one embodiment of the combustor dome assembly  100 , the forward edge  150  of deflector cup  136  is flared outward such that the edge  150  is chamfered. A washer or spring  148 , such as a Belleville washer or the like, is positioned between the mixer  114  and the deflector  108  to hold the deflector in place with respect to the combustor dome  106 . More particularly, the spring  148  is positioned between the chamfered edge  150  and the mixer  114  to axially load the deflector  108  into the seal plate  116  and thereby to help hold the deflector  108  in place axially. The spring  148  helps to press an outside surface  152  of the edge  150  into a surface  154  of the seal plate  116 , such that the deflector outside surface  152  interfaces with the seal plate surface  154 . It will be appreciated that, although the flare cone  128  is illustrated in  FIG. 8  as part of the mixer  114 , in suitable embodiments, the flare cone  128  may be included as part of the deflector  108  as described with respect to  FIG. 7 . Further, in some embodiments, the seal plate  116  may have to be split circumferentially to allow for assembly. 
     In the embodiment of combustor dome assembly  100  shown in  FIG. 9 , a flange  156  is defined about the forward edge  150  of deflector cup  136 . The flange  156  is received between a shoulder  158  of the mixer  114  and a shoulder  160  of the seal plate  116 . More specifically, the flange  156  is captured between the mixer shoulder  158  and the seal plate shoulder  160  to hold the deflector  108  in place. As such, a first surface  162  of the flange  156  interfaces with a surface  164  of the mixer shoulder  158 , and a second surface  166  of the flange  156  interfaces with a surface  168  of the seal plate shoulder  160 . Further, as stated with respect to  FIG. 8 , although the flare cone  128  is illustrated in  FIG. 9  as part of the mixer  114 , in suitable embodiments, the flare cone  128  may be included as part of the deflector  108  as described with respect to  FIG. 7 . Moreover, in some embodiments, the seal plate  116  may have to be split circumferentially to allow for assembly. 
     Turning to  FIG. 10 , in another embodiment of the combustor dome assembly  100 , the seal plate  116  may be omitted such that the deflector  108  is positioned adjacent the combustor dome  106  in dome opening  110 , and a portion of the mixer  114  may be configured to be positioned adjacent the combustor dome  106  on the forward side  102  of the combustor dome assembly  100 . As shown in  FIG. 10 , the deflector  108  includes the flare cone  128  such that the flare cone  128  is made from a CMC material. Further, the deflector cup  136  defines a pocket  170  for receipt of a spring  148  that helps hold the deflector  108  in position as described in greater detail above, i.e., the spring  148  is positioned between the dome  106  and the deflector  108  to hold the deflector in place with respect to the combustor dome  106 . The mixer  114  includes an outer arm  172  that extends toward the combustor dome  106  on the forward side  102  of the combustor dome assembly  100 . The mixer  114  may be attached, e.g., brazed or welded, to the combustor dome  106  at the end of the outer arm  172 . As such, the mixer  114  is used to hold the deflector  108  in place with respect to the combustor dome  106 . 
     In the embodiment illustrated in  FIG. 11 , the seal plate  116  is omitted such that the deflector  108  is positioned adjacent the combustor dome  106  in dome opening  110 , and similar to the embodiment of  FIG. 10 , the mixer  114  is used to hold the deflector  108  in place with respect to the combustor dome  106 . Like the embodiment shown in  FIG. 10 , the mixer  114  illustrated in  FIG. 11  includes an outer arm  172  that may be attached, e.g., brazed or welded, to the combustor dome  106 . The mixer  114  also includes an inner arm  174  having a flange  176  at its aft end. The deflector  108  includes the flare cone  128 , which transitions to a ramp portion  178  at the cup portion  136  of the deflector  108 . The ramp portion  178  defines a groove  180  about its outer perimeter. As such, when the mixer  114  is assembled with the deflector  108 , the mixer inner arm  174  slides up the deflector ramp portion  178  until the flange  176  is received in the groove  180  such that the flange  176  and groove  180  form a joint between the mixer  114  and the deflector  108 . It will be appreciated that, although only one half of the cross-section of the mixer  114  and the deflector  108  are shown in the exemplary embodiment of  FIG. 11 , the inner arm  174 , flange  176 , and groove are generally annular. Accordingly, the interface or joint between the mixer  114  and deflector  108  at the flange  176  and groove  180  helps hold the deflector  108  in position with respect to the mixer  114  and combustor dome  106 . 
     Referring now to  FIG. 12 , in another exemplary embodiment of the present subject matter, the cup  136  of the deflector  108  defines a pocket  170  for the receipt of a spring  148 . The spring  148  extends generally from an interface between the mixer  114  and the seal plate  116  to the pocket  170  and helps holds the deflector  108  in position as described in greater detail above, i.e., the spring  148  is positioned between the mixer  114  and the deflector  108  to hold the deflector in place with respect to the combustor dome  106 . Further, although  FIG. 12  illustrates the flare cone  128  as included with the mixer  114 , in suitable embodiments, at least a portion of the flare cone  128  may instead be included with the deflector  108 . 
       FIG. 13  provides a cross-section view of yet another embodiment of the present subject matter. In the embodiment shown in  FIG. 13 , the seal plate  116  is omitted, and the deflector  108  includes the flare cone  128 . The mixer  114  includes an outer arm  172  and an inner arm  174 , and a pocket  182  is defined in the inner arm  174 . An aperture (not shown) is defined in each of the outer arm  172  and the deflector cup  136 , and the apertures are configured for receipt of a pin  184 . In some embodiments, a plurality of apertures may be defined in each of the outer arm  172  and the deflector cup  136  for receipt of a plurality of pins  184 , in a configuration that generally may be described as a hub and spoke configuration. The pins  184  help hold the deflector  108  in position with respect to the mixer  114  and combustor dome  106 . A retention mechanism may be used to help retain the pins  184  within the apertures, e.g., a weld may be used between each pin  184  and the mixer  114  to help retain each pin  184  in its respective mixer and deflector apertures. 
     As will be readily understood, the deflector  108  of the embodiments shown in  FIGS. 7 through 13  preferably is formed from a CMC material such that the deflector is a CMC deflector  108 , as described with respect to  FIG. 6 . As such, the CMC deflector  108  has a different rate of thermal expansion than the metallic components, e.g., the combustor dome  106 , mixer  114 , and seal plate  116 . More particularly, the metallic components will grow faster than the CMC deflector  108  and will begin to thermally expand at lower temperatures than the CMC deflector  108 . As such, the CMC deflector  108  and the metallic components may be appropriately sized such that the components may be assembled under cold, non-operating engine conditions with room to expand under hot, operating engine conditions. Further, as described above, the sizing of the various components may help retain the CMC deflector  108  in a desired position under cold and hot engine conditions. 
     Moreover, it will be appreciated that the above embodiments of the combustor dome assembly  100  may be retrofits of existing combustor dome assembly designs or may be implemented as new builds. For instance, existing fuel-air mixers may be modified to accommodate bayonets of new CMC deflectors  108  such that the deflector  108  as described herein may be utilized with existing combustor dome  106 , mixer  114 , and seal plate  116  components. However, some embodiments of, e.g., the mixer  114  described herein may not be suitable for modification of existing mixers and may require fabrication of new mixers  114 . 
     As illustrated by the flow diagram of  FIG. 14 , a method of assembling an exemplary combustor dome assembly  100  also may be provided. With particular reference to the embodiment shown in  FIGS. 3 through 6 , an exemplary method of assembly  1400  includes assembling the combustor dome  106  with the combustor, as shown at  1402  in  FIG. 14 . Then, as indicated at  1404 , a seal plate  116  is inserted from the forward side  102 , such that the seal plate wall  142  is inserted into the dome opening  110 . Next, at  1408 , it is determined whether there is more than one seal plate  116  in the combustor dome assembly  100 , and if so, the process of inserting the seal plate  116  is repeated until each seal plate  116  is assembled with the combustor dome  106 . For example, a seal plate  116  may be provided adjacent each dome opening  110 , or a single seal plate  116  may include more than one seal plate wall  142  such that one seal plate  116  is positioned adjacent more than one dome opening  110 . In any event, if more than one seal plate  116  is provided with the combustor dome assembly  100 , the steps shown at  1404  and  1406  are repeated until all seal plates  116  are inserted. Then, the seal plates  116  are attached to the combustor dome  106 , as shown at  1408 , e.g., by welding or brazing. Thus, the seal plates  116  are attached to the combustor dome  106  before the CMC deflectors  108  are present. 
     Then, as shown at  1410  in  FIG. 14 , the CMC deflector  108  is inserted from the aft side  104  of the combustor dome assembly  100  such that the deflector cup  136  extends through the seal plate opening defined by the wall  142 . Further, the seal plate key  140  is received in the deflector groove  138 . Next, as shown at  1412 , the mixer  114  is inserted from the forward side  102 , with the mixer slots  124  aligned with the deflector bayonets  118  such that the aft end  122  of the mixer  114  slides past the bayonets  118  and the bayonets  118  are positioned in the groove  120 . As indicated at  1414 , the mixer  114  is then rotated to engage the bayonets  118  with the mixer  114  and thereby couple the deflector  108  and the mixer  114 . As described with respect to seal plates  116  and as shown at  1416 , in embodiments comprising a plurality of deflectors  108 , steps  1410  through  1414  may then be repeated for each deflector  108  and mixer  114  such that a mixer  114  is inserted next to each one of the plurality of deflectors  108 . 
     Next, as shown at  1418  in  FIG. 14  and if required, a key may be attached within each mixer slot  124 , e.g., by welding or brazing, to fill the slots  124  and to help prevent undesirable leakage and aerodynamic effects as described above. Finally, as indicated at  1420 , each mixer  114  may be attached to its adjacent seal plate  116 , for example, by welding or brazing the mixers  114  to the adjacent seal plate  116 . 
     Method  1400  is provided by way of example only, and it will be appreciated that the method of assembly may be modified for other embodiments of the combustor dome assembly  100 . For example, in embodiments in which the seal plate  116  is omitted, steps  1404  through  1408  are omitted. 
     As previously stated, the deflector  108  described in each of the exemplary embodiments herein is formed from a CMC material, and a method for forming a CMC deflector  108  first may comprise laying up a plurality of plies of the CMC material to form a CMC preform having a desired shape or contour. It will be appreciated that the plurality of CMC plies forming the preform may be laid up on a layup tool, mold, mandrel, or another appropriate device for supporting the plies and/or for defining the desired shape. The desired shape of CMC preform may be a desired shape or contour of the resultant CMC deflector  108 . As an example, the plies may be laid up to define the deflector body  109  and the deflector cup  136 . Laying up the plurality of plies to form the CMC deflector preform may include defining other features of the deflector  108  as well, such as the flare cone  128  and/or the pocket  170 . 
     After the plurality of plies is laid up to form the preform, the preform may be processed, e.g., compacted and cured in an autoclave. After processing, the preform forms a green state CMC component, i.e., a green state CMC deflector  108 . The green state CMC component is a single piece component, i.e., curing the plurality of plies of the preform joins the plies to produce a CMC component formed from a continuous piece of green state CMC material. The green state component then may undergo firing (or burn-off) and densification to produce a densified CMC deflector  108 . For example, the green state component may be placed in a furnace to burn off any mandrel-forming materials and/or solvents used in forming the CMC plies and to decompose binders in the solvents, and then placed in a furnace with silicon to convert a ceramic matrix precursor of the plies into the ceramic material of the matrix of the CMC component. The silicon melts and infiltrates any porosity created with the matrix as a result of the decomposition of the binder during burn-off/firing; the melt infiltration of the CMC component with silicon densifies the CMC component. However, densification may be performed using any known densification technique including, but not limited to, Silcomp, melt-infiltration (MI), chemical vapor infiltration (CVI), polymer infiltration and pyrolysis (PIP), and oxide/oxide processes. In one embodiment, densification and firing may be conducted in a vacuum furnace or an inert atmosphere having an established atmosphere at temperatures above 1200° C. to allow silicon or another appropriate material or materials to melt-infiltrate into the component. 
     Optionally, after firing and densification the CMC deflector  108  may be finish machined, if and as needed, and/or coated with one or more coatings, such as an environmental barrier coating (EBC) or a thermal barrier coating (TBC). For instance, the pocket  170  utilized in some embodiments may be machined into the CMC deflector  108 . 
     The foregoing method of forming a CMC deflector  108  is provided by way of example only. For example, other known methods or techniques for compacting and/or curing CMC plies, as well as for densifying the green state CMC component, may be utilized. Alternatively, any combinations of these or other known processes may be used. 
     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 language of the claims.