Combustor heat shield and attachment features

Combustor assemblies having heat shields heat shield attachment features are provided. For example, a combustor assembly includes a dome plate defining first and second apertures, and a heat shield defining first and second openings. The heat shield includes a first cup extending about the first opening and a second cup extending about the second opening. The combustor assembly further includes a collar having a first frame at least partially surrounding the first cup and a second frame at least partially surrounding the second cup. The collar includes a first fastening feature and the dome plate includes a second fastening feature. The first fastening feature mates with the second fastening feature to couple the heat shield to the dome plate. The combustor assembly also may include an attachment piece configured to couple the heat shield to the dome plate. Methods for forming ceramic matrix composite (CMC) heat shields also are provided.

FIELD OF THE INVENTION

The present subject matter relates generally to combustor assemblies of gas turbine engines. More particularly, the present subject matter relates to heat shields for combustors of gas turbine engines and features for attaching heat shields to combustor assemblies.

BACKGROUND OF THE INVENTION

A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section 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.

Combustion gas temperatures are relatively hot, such that some components in or near the combustion section and the downstream turbine section require features for deflecting or mitigating the effects of the combustion gas temperatures. For example, one or more heat shields may be provided on a combustor dome to help protect the dome from the heat of the combustion gases. However, such heat shields often require cooling themselves, e.g., through a flow of cooling fluid directed against the heat shields, which can negatively impact turbine emissions. Further, turbine performance and efficiency generally may be improved by increasing combustion gas temperatures. Therefore, there is an interest in providing heat shields that can withstand increased combustion gas temperatures yet also require less cooling, to increase turbine performance and efficiency while also reducing turbine emissions.

Non-traditional high temperature materials, such as ceramic matrix composite (CMC) materials, are more commonly being used for various components within gas turbine engines. For example, because CMC materials can withstand relatively extreme temperatures, there is particular interest in replacing components within the flow path of the combustion gases, such as combustor dome heat shields, with CMC materials. Nonetheless, typical CMC heat shields have complex shapes that are difficult to fabricate, often requiring complex or special tooling, and are difficult to assemble with the combustor dome, usually requiring numerous intricate metal pieces to properly assemble the heat shields with the dome.

Accordingly, improved combustor heat shields and features for attaching heat shields within combustor assemblies that overcome one or more disadvantages of existing designs would be desirable. In particular, a combustor assembly utilizing a CMC heat shield would be helpful. Additionally, a combustor assembly with one or more features for fastening a CMC heat shield to a combustor dome that compensates for any difference in thermal expansion between the CMC heat shield and the combustor dome would be beneficial. Moreover, a combustor assembly with one or more features for minimizing rotation of a heat shield with respect to a combustor dome would be useful. Further, a combustor assembly with one or more features providing sealing between a heat shield and a combustor dome would be beneficial. Improved methods of fabricating a CMC heat shield also would be advantageous.

BRIEF DESCRIPTION OF THE INVENTION

In one exemplary embodiment of the present disclosure, a combustor assembly for a gas turbine engine is provided. The combustor assembly includes a dome plate defining a first aperture and a second aperture, and a heat shield defining a first opening and a second opening. The heat shield includes a first cup extending about the first opening and a second cup extending about the second opening. The first cup extends toward the first aperture of the dome plate and the second cup extends toward the second aperture of the dome plate. The combustor assembly further includes a collar having a first frame at least partially surrounding the first cup and a second frame at least partially surrounding the second cup. Additionally, the collar includes a first fastening feature and the dome plate includes a second fastening feature. The first fastening feature mates with the second fastening feature to couple the heat shield to the dome plate.

In another exemplary embodiment of the present disclosure, a combustor assembly for a gas turbine engine is provided. The combustor assembly includes a dome plate defining a first aperture and a second aperture. The combustor assembly also comprises a heat shield that includes a first cup extending toward the first aperture of the dome plate and a second cup extending toward the second aperture of the dome plate. The first cup defines a flange about its outer perimeter, and the second cup defines a flange about its outer perimeter. The combustor assembly further comprises a first attachment piece that defines a flange about its outer perimeter, as well as a second attachment piece that defines a flange about its outer perimeter. Moreover, the combustor assembly includes a collar having a first frame and a second frame. The first frame fits around the flange of the first cup and the flange of the first attachment piece to couple the first attachment piece to the first cup. The second frame fits around the flange of the second cup and the flange of the second attachment piece to couple the second attachment piece to the second cup. The first and second attachment pieces are configured to couple the heat shield to the dome plate.

In a further exemplary embodiment of the present disclosure, a method for forming a ceramic matrix composite (CMC) heat shield for a gas turbine engine combustor assembly is provided. The method comprises laying up a plurality of plies of a CMC material; processing the plurality of plies to form a green state CMC heat shield; firing the green state CMC heat shield; and densifying the fired CMC heat shield to produce the CMC heat shield. The heat shield includes a first cup extending about a first opening defined by the heat shield, a second cup extending about a second opening defined by the heat shield, and a pad for receipt of a seal member.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,FIG. 1is 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 ofFIG. 1, the gas turbine engine is a high-bypass turbofan jet engine10, referred to herein as “turbofan engine10.” As shown inFIG. 1, the turbofan engine10defines an axial direction A (extending parallel to a longitudinal centerline12provided for reference) and a radial direction R. In general, the turbofan10includes a fan section14and a core turbine engine16disposed downstream from the fan section14.

For the depicted embodiment, fan section14includes a fan38having a plurality of fan blades40coupled to a disk42in a spaced apart manner. As depicted, fan blades40extend outward from disk42generally along the radial direction R. The fan blades40and disk42are together rotatable about the longitudinal axis12by LP shaft36. In some embodiments, a power gear box having a plurality of gears may be included for stepping down the rotational speed of the LP shaft36to a more efficient rotational fan speed.

Referring now toFIG. 2, a schematic, cross-sectional view is provided of a combustor assembly79according to an exemplary embodiment of the present subject matter. More particularly,FIG. 2provides a side, cross-sectional view of an exemplary combustor assembly79, which may, for example, be positioned in the combustion section26of the exemplary turbofan engine12ofFIG. 1.

Combustor assembly79depicted inFIG. 2generally includes a combustion chamber80defined by an inner liner82and an outer liner84, e.g., combustion liners82,84together at least partially define combustion chamber80therebetween. Combustion liners82,84, or other components of combustor assembly79, may be made from a ceramic matrix composite (CMC) material as further described below. Combustor assembly79extends generally along the axial direction A from a forward end86to an aft end88. Inner liner82generally defines a hot side90exposed to and defining in part a portion of the hot gas path78extending through the combustion chamber80. Inner liner82further defines a cold side92opposite hot side90. Similarly, outer liner84also defines a hot side94exposed to and defining in part a portion of the hot gas path78extending through the combustion chamber80, and outer liner84further defines a cold side96opposite hot side94.

The inner and outer liners82,84are each attached to an annular dome100at the forward end86of combustor assembly79. More particularly, dome100includes an inner dome section102attached to inner liner82and an outer dome section104attached to outer liner84. The inner and outer dome sections102,104may each extend along a circumferential direction C (FIG. 3) to define an annular shape. Inner and outer dome sections102,104each also define a slot106for receipt of inner liner82and outer liner84, respectively.

Combustor assembly79further includes a plurality of fuel air mixers108spaced along the circumferential direction and positioned at least partially within the dome100. More particularly, the plurality of fuel air mixers108are disposed at least partially between outer dome section104and inner dome section102along the radial direction R. Compressed air from the compressor section of the turbofan engine10flows into or through the fuel air mixers108, where the compressed air is mixed with fuel and ignited to create the combustion gases66within the combustion chamber80. The inner and outer dome sections102,104are configured to assist in providing the flow of compressed air from the compressor section into or through the fuel air mixers108. For example, inner dome section102includes an inner cowl110, and outer dome section104similarly includes an outer cowl112. The inner and outer cowls110,112may assist in directing the flow of compressed air from the compressor section into or through one or more of the fuel air mixers108.

In certain exemplary embodiments, the inner dome section102with inner cowl110may be formed integrally as a single annular component, and similarly, the outer dome section104with outer cowl112also may be formed integrally as a single annular component. It should be appreciated, however, that in other exemplary embodiments, the inner dome section102and/or the outer dome section104alternatively may be formed by one or more components being joined in any suitable manner. For example, with reference to the outer dome section104, in certain exemplary embodiments, outer cowl112may be formed separately from outer dome section104and attached to outer dome section104using, e.g., a welding process. Additionally or alternatively, the inner dome section102may have a similar configuration.

Referring still toFIG. 2, the exemplary combustor assembly79further includes a heat shield114positioned around the fuel air mixer108as depicted. The exemplary heat shield114, for the depicted embodiment, is attached to and extends between inner and outer dome sections102,104. The heat shield114is configured to protect certain components of the turbofan engine10from the relatively extreme temperatures of the combustion chamber80, as described in greater detail below.

Keeping withFIG. 2, combustor assembly79at the aft end88includes an inner piston ring seal116at inner liner82and an outer piston ring seal118at outer liner84. The inner piston ring seal116is attached to an inner piston ring holder120extending from and attached to an inner casing122. Similarly, the outer piston ring seal118is attached to an outer piston ring holder124extending from and attached to an outer casing126. Inner piston ring holder120and outer piston ring holder124are configured to accommodate an expansion of the inner liner82and the outer liner84generally along the axial direction A, as well as generally along the radial direction R. To allow for a relative thermal expansion between the outer liner84and the outer dome section104, as well as between the inner liner82and the inner dome section102, a plurality of mounting assemblies130are used to attach outer liner84to outer dome section104and inner liner82to inner dome section104. More particularly, the mounting assemblies130attach the forward end of outer liner84to outer dome section104within the slot106of outer dome section104and the forward end of inner liner82to inner dome section102within the slot122of inner dome section102.

Further, as is discussed above, the combustion gases66flow from the combustion chamber80into and through the turbine section of the turbofan engine12, where a portion of thermal and/or kinetic energy from the combustion gases66is extracted via sequential stages of turbine stator vanes and turbine rotor blades. A stage one (1) stator vane128is depicted schematically inFIG. 2, aft of the combustor assembly79.

In some embodiments, components of turbofan engine10, particularly components within hot gas path78such as components of combustion assembly79, 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's SCS-6), as well as rovings and yarn including silicon carbide (e.g., Nippon Carbon's NICALON®, Ube Industries' TYRANNO®, and Dow Corning's SYLRAMIC®), alumina silicates (e.g., Nextel's 440 and 480), and chopped whiskers and fibers (e.g., Nextel'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 path78, such as within the combustion and/or turbine sections of engine10. 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, heat shield114for combustor dome100may be formed from a CMC material to provide protection to the dome from the heat of the combustion gases, e.g., without requiring cooling from a flow of fluid as is usually required for metal heat shields.

Turning now toFIG. 3, an aft side perspective view is provided of a heat shield114and a portion of a dome plate132of combustor assembly79, according to an exemplary embodiment of the present subject matter. In various embodiments, dome plate132may include at least a portion of inner dome segment102, at least a portion of outer dome segment104, or at least a portion of both inner and outer dome segments102,104. In some embodiments, dome plate132may comprise the entire dome100. Other configurations of dome plate132may be used as well.

As illustrated inFIG. 3, the dome plate132includes a forward side134and an aft side136, and heat shield114is attached to dome plate132such that a plate portion138of heat shield114is positioned on the aft side136of dome plate132. Dome plate132defines a first aperture140(FIG. 4) and a second aperture142(FIG. 4), and heat shield114includes a first cup144and a second cup146. As shown, the first cup144extends toward the first aperture140of dome plate132. Similarly, second cup146extends toward the second aperture142of dome plate132. Moreover, heat shield114defines a first opening148and a second opening150. The first opening148is defined at least in part by first cup144and the second opening150is defined at least in part by second cup146. As such, first opening148, first cup144, and first aperture140define a first passage152through heat shield114and dome plate132. Similarly, second opening150, second cup146, and second aperture142define a second passage154through heat shield114and dome plate132.

Referring now toFIG. 4, an exploded view is provided of heat shield114, dome plate132, and means for attaching the heat shield to the dome plate, according to an exemplary embodiment of the present subject matter. More particularly, heat shield114includes a forward surface156and an aft surface158. The forward surface156and aft surface158each define in part the first and second openings148,150in heat shield114. Further, as shown inFIG. 4, first cup144extends from the forward surface156, as well as extends about the first opening148. Similarly, second cup146extends from the forward surface156, as well as extends about the second opening150. Although first and second cups144,146generally are annular in the depicted embodiment, in other embodiments first and second cups144,146may have another suitable shape.

Keeping withFIG. 4, the combustor assembly79further includes a collar160that is attachable to the heat shield114for coupling the heat shield114to the dome plate132. Collar160includes a first frame162and a second frame164. Turning toFIG. 5, when assembled with heat shield114, the first frame162extends about an outer perimeter of the first cup144such that the first frame162at least partially surrounds the first cup144. Likewise, the second frame164extends about an outer perimeter of the second cup146such that the second frame164at least partially surrounds the second cup146. As depicted inFIGS. 4 and 5, collar160is split into two halves along a collar centerline CL1(FIGS. 6A and 7A) that extends generally along the radial direction R. Further, each of the first frame162and second frame164is generally annular or ring-shaped. As such, the depicted collar160may be described as a split-ring collar. A first half160aof the split-ring collar160may include a first portion162aof the first frame162and a first portion164aof the second frame164, while a second half160bof the split-ring collar160may include a second portion162bof the first frame162and a second portion164bof the second frame164.

As illustrated inFIG. 4, an attachment piece166may be included to help couple heat shield114to dome plate132. As most clearly shown inFIGS. 6C and 8Band described in greater detail below, collar160may couple attachment piece166to heat shield114, and as shown inFIG. 4, attachment piece166may be threaded to engage threads of a nut101or another suitable component and thereby couple heat shield114to dome plate132of combustor dome100. For example, as described below with respect toFIG. 10, the threads of attachment piece166may engage the threads of retainer nut101that, together with a spacer103, secures attachment piece166within a bore of combustor dome100. Of course, in other embodiments, attachment piece166may have other configurations or features to help attach heat shield114to dome plate132.

FIG. 5depicts an aft perspective view of heat shield114and collar160according to an exemplary embodiment of the present subject matter. As shown inFIG. 5, a pad168is defined along a perimeter of forward surface156of the plate portion138of heat shield114. The pad168along the perimeter may, e.g., provide a target area for the placement of a seal member190(FIGS. 6C, 8B) between heat shield114and dome plate132, e.g., to provide a seal between the heat shield and the dome plate. More particularly, the raised pad168preferably is dimensioned to reduce or relax a locational tolerance required for any seal member placed about the perimeter of heat shield114. That is, pad168may be sized such that a tight or close tolerance is not required for the placement of a seal member about the perimeter of heat shield114. In one embodiment, the seal member190may be a spline seal that is used along pad168to provide a seal between heat shield114and dome plate132. In other embodiments, other types and/or configurations of seal member190may be used.

Turning now toFIGS. 6A and 6B, aft side views are provided of split-ring collar160(FIG. 6A) and dome plate132(FIG. 6B) according to an exemplary embodiment of the present subject matter. As shown inFIG. 6A, each of first portion162aof first frame162, second portion162bof first frame162, first portion164aof second frame164, and second portion164bof second frame164includes at least one fastening feature170. More particularly, in the embodiment depicted inFIG. 6A, each of the fastening features170of first frame162and second frame164are tabs, which, as described in greater detail below, are configured to mate with corresponding grooves defined in dome plate132to couple the heat shield to the dome plate. The tabs170may be defined at different positions along the respective frame162,164, and some frame portions may include more than one tab170. For example, in the embodiment ofFIG. 6A, first and second portions162a,162bof first frame162each include two tabs170, and each tab170extends outwardly from first frame162generally along or parallel to the collar centerline CL1and the radial direction R. In contrast, first and second frame portions164a,164bof second frame164each define one tab170, and the tabs170of second frame164extend outwardly from second frame164, generally at a non-orthogonal angle α with respect to the collar centerline CL1and the radial direction R. More specifically, tabs170of second frame164generally extend in a direction of a straight line172drawn through both tabs170, where the line172is at the non-orthogonal angle α with respect to the collar centerline CL1and the radial direction R.

As further shown inFIG. 6A, each collar half160a,160bincludes a bridge member174. First bridge member174ahelps connect the first portion162aof first frame162with the first portion164aof second frame164, and second bridge member174bhelps connect the second portion162bof first frame162with the second portion164bof second frame164. As will be discussed in greater detail below, bridge members174may act as springs in collar160, e.g., to help hold the collar's position with respect to dome plate132, and therefore the position of heat shield114with respect to dome plate132, as the temperatures within combustor79increase and the components undergo thermal expansion.

Referring toFIG. 6B, the dome plate132includes at least one fastening feature176that is complementary to fastening feature170of collar160. More particularly, in the embodiment ofFIG. 6B, the fastening features176are grooves defined in dome plate132adjacent first and second apertures140,142. Each groove fastening feature176is configured to receive at least one tab170of collar160to help couple heat shield114to dome plate132. For example, in the depicted embodiment ofFIG. 6B, two grooves176are defined in the dome plate132adjacent first aperture140such that the grooves176open into the first aperture140. The grooves176in dome plate132at first aperture140correspond to the tabs170included on first frame162of collar160. As such, the grooves176at first aperture140are defined substantially along the radial direction R, and when collar160is received within dome plate132, the tabs170of first frame162are received within the grooves176adjacent first aperture140. Similarly, two grooves176are defined in the dome plate132adjacent second aperture142such that the grooves176open into the second aperture142. The grooves176in dome plate132at second aperture142correspond to the tabs170included on second frame164of collar160. Accordingly, the grooves176at second aperture142are defined at the non-orthogonal angle α with respect to the radial direction R. As such, when collar160is received within dome plate132, the tabs170of second frame164are received within the grooves176adjacent second aperture142, and a straight line178drawn through both grooves176defined at second aperture142is substantially parallel to straight line172drawn through tabs170of second frame164of collar160.

The fastening features170of collar160and fastening features176of dome plate132thereby provide essentially anti-rotation fastening between the heat shield114and dome plate132while also accounting for different coefficients of thermal expansion between the heat shield material and the dome plate material. That is, heat shield114preferably is fabricated from a CMC material as discussed above and as further described below, and the dome plate132and collar160each may be made from a metallic material, such as a metal alloy. In such embodiments, there is an alpha mismatch between heat shield114, dome plate132, and collar160, i.e., the coefficient of thermal expansion of the CMC heat shield is different from the coefficient of thermal expansion of the metallic dome plate and the metallic collar. Generally, in such embodiments, the dome plate132will expand at lower temperatures than the CMC heat shield114. The grooves176, i.e., the fastening features of dome plate132, may be set or defined in the direction of growth of dome plate132. More particularly, the first and second apertures140,142of dome plate132may grow, or thermally expand, in the same direction or in different directions. Therefore, the grooves176may be defined at different locations with respect to the apertures140,142as shown inFIGS. 4 and 6B, or in other embodiments, may be defined at substantially the same location with respect to each aperture140,142. The tabs170of collar160are positioned with respect to first and second frames162,164to correspond to the respective grooves176of dome plate132, as previously described. Then, when collar160is assembled with heat shield114and the collar and heat shield assembly is received within dome plate132, the tabs170mate with the grooves176to attach the heat shield114such that the first and second cups144,146and heat shield114do not rotate with respect to dome plate132, or vice versa. Further, it will be appreciated that, as the combustion temperatures rise and the components experience thermal expansion, the collar160may grow with dome plate132such that tabs170remain within groove176to maintain the relative positions of the heat shield114and dome plate132.

Referring toFIG. 6C, a cross-section view is provided of a heat shield and dome plate assembly according to an exemplary embodiment of the present subject matter. As illustrated, the collar160is received within the first aperture140and the second aperture142of the dome plate132such that the collar expands and contracts within the dome plate132with thermal changes in the combustor assembly79. That is, as temperatures increase within combustor assembly79, the collar160thermally expands within dome plate132, and as temperatures subsequently decrease within combustor assembly79, the collar160thermally contracts within dome plate132. As described above, the first and second fastening features, such as tabs170of collar160and grooves176of dome plate132, mate to help prevent rotational and/or other movement of collar160relative to the dome plate132as the components of combustor assembly79thermally expand and contract, which helps keep the heat shield114in place with respect to dome plate132. However, it will be understood that the configuration of collar160and heat shield114, e.g., the first and second frames162,164of collar160fitting around first and second cups144,146of heat shield114, allows or compensates for differences in thermal expansion between the collar and heat shield, as well as differences in thermal expansion between the heat shield and combustor dome100.

Moreover, as previously stated, an attachment piece166may be used at each cup144,146of heat shield114to help couple heat shield114to dome plate132. In the exemplary embodiment shown inFIG. 6C, first cup144includes a flange192that extends about the outer perimeter of the cup. Attachment piece166also includes a flange194extending about an outer perimeter of the attachment piece at an aft end thereof. First frame162of collar160has a generally C- or U-shaped cross-section such that first frame fits over both the first cup flange192and attachment piece flange194to couple the attachment piece166to heat shield114. One or more seals and/or washers, such as a flat washer200and a wave seal202as depicted inFIG. 6C, may be included between the first cup flange192and attachment piece flange194. The seals and/or washers may, e.g., compensate for variations in part dimensions and/or differences in thermal expansion between the CMC heat shield114and metallic collar160and attachment piece166and thereby help mitigate wear between heat shield114and attachment piece166and/or help prevent hot gas leakage between heat shield114and attachment piece166, as hot gas leakage could decrease the effectiveness of the heat shield in protecting dome plate132from exposure to the hot combustion gases. As previously described, at least a portion of attachment piece166, such as a portion of an outer surface of the attachment piece, may be threaded to engage with threads defined in dome plate132(or to engage threads of a feature such as retainer nut101) and thereby help couple the heat shield114to dome plate132of combustor dome100.

As further illustrated inFIG. 6C, one heat shield114may be positioned adjacent another heat shield114. That is, in some embodiments, multiple heat shields may be used to protect dome100from hot combustion gases generated within combustor79. At the interface between adjacent heat shields114, a seal member190may be used to provide a seal between the heat shields114and dome plate132and, e.g., to prevent hot gas leakage at the interface between the heat shields. In the exemplary embodiment ofFIG. 6C, a seal member190is received within a recess204defined in dome plate132and seals against pad168extending about the edge of a heat shield114. Thus, at least one seal member190is provided at the edge of each heat shield114such that two seal members190may be adjacent one another at the interface between adjacent heat shields114. It will be understood that other types and configurations of seal members190may be used as well.

Further, it will be appreciated that, although described above with respect to only first cup144of heat shield114and first frame162of collar160, as illustrated inFIG. 6C, second cup146and second frame164may be configured similarly to first cup144and first frame162, respectively, and a second attachment piece166coupled with second cup146to help attach heat shield114to dome plate132. More particularly, second cup146may include a flange192that extends about the outer perimeter of the cup, and the second attachment piece166may also include a flange194extending about an outer perimeter of the attachment piece at an aft end thereof. Second frame164of collar160may have a generally C- or U-shaped cross-section such that the second frame164fits over both the second cup flange192and the second attachment piece flange194to couple the second attachment piece166to heat shield114. Moreover, one or more seals and/or washers, such as a flat washer200and a wave seal202, may be included between the second cup flange192and second attachment piece flange194, e.g., to compensate for variations in part dimensions and/or differences in thermal expansion between the CMC heat shield114and metallic collar160and second attachment piece166, which can help mitigate wear between heat shield114and second attachment piece166and/or help prevent hot gas leakage between heat shield114and second attachment piece166. At least a portion of the second attachment piece166, such as a portion of an outer surface of the attachment piece, may be threaded to engage with threads defined in dome plate132(or to engage threads of a feature such as retainer nut101) and thereby help couple the heat shield114to dome plate132of combustor dome100.

Turning now toFIGS. 7A and 7B, an aft side view is provided of collar160(FIG. 7A) and dome plate132(FIG. 7B) according to another exemplary embodiment of the present subject matter. As illustrated inFIG. 7A, in some embodiments bridge members174, rather than first and/or second frames162,164, may define one or more fastening features to help couple heat shield114to dome plate132. More specifically, in the illustrated embodiment, each bridge member174defines a pin aperture180, i.e., bridge member174aof first half160adefines a pin aperture180aand bridge member174bof second half160bdefines a pin aperture180b. As such, the pin apertures180a,180bare defined between the first frame162and the second frame164along the radial direction R. Further, in the depicted embodiment bridge members174a,174beach include a generally annular or ring-shaped portion182that defines pin apertures180a,180b. First bridge member174aincludes a first annular portion182athat defines first pin aperture180a, and second bridge member174bincludes a second annular portion182bthat defines second pin aperture180b. However, in other embodiments, bridge members174a,174bmay have other shapes or configurations and may define pin apertures180in any suitable portion of the respective bridge member. In still other embodiments, pins apertures180may be defined by other suitable portions collar160than bridge members174.

Referring toFIG. 7B, in some embodiments, the dome plate132defines one or more fastening features between the first aperture140and second aperture142. The exemplary dome plate132depicted inFIG. 7Bdefines two slots184between first aperture140and second aperture142, a first slot184aand a second slot184b. The slots184are spaced from first and second apertures140,142along the radial direction R and from one another along the circumferential direction C. As shown, the slots184are elongated, or generally pill-shaped, along the radial direction R.

When the collar160as shown inFIG. 7Ais assembled with heat shield114and the dome plate132as shown inFIG. 7B, the slots184of the dome plate132align with pin apertures180of collar160such that a pin (not shown) may be received within both the slots184and the pin apertures180to help couple the heat shield to the dome plate. More particularly, a pin is received with both first slot184aand first pin aperture180a, which is defined by first annular portion182a. It will be understood that a second pin may be similarly received within second slot184band second pin aperture180b. In appropriate embodiments, only one pin aperture180, slot184, and pin may be used, or in other embodiments, more than two pin apertures180, slots184, and pins may be used. In any event, the pin and slot fastening features of collar160and dome plate132can help couple heat shield114(to which collar160is attached) to dome plate132, or at least help heat shield114and dome plate132maintain their relative positions with respect to one another. More specifically, a pin is received in slot(s)184and pin aperture(s)180to mate the fastening feature of collar160(i.e., pin aperture180) with the fastening feature of dome plate132(i.e., slot184) to help couple the heat shield114and dome plate132and/or to help maintain the relative positions of heat shield114and dome plate132.

Further, it will be appreciated that slots184may be located to minimize the impacts of an alpha mismatch, i.e., a mismatch of coefficients of thermal expansion, between the heat shield114and dome plate132. That is, slots184may be defined in an area of dome plate132that is the relatively coolest area of the dome plate to minimize the thermal changes in the slot dimensions, which may impact the relative positions of the heat shield114and dome plate132with respect to one another. As such, the slots184may be defined in dome plate132to minimize the changes in position of heat shield114and dome plate132in the direction of growth of the dome plate.

Turning now toFIGS. 8A and 8B, an aft side view (FIG. 8A) and a cross-section view (FIG. 8B) are provided of heat shield114according to another exemplary embodiment of the present subject matter. As illustrated inFIGS. 8Aand8B, plate portion138of heat shield may have a generally conical shape about first and second openings148,150. Stated differently, in some embodiments, the plate portion138around first opening148and second opening150may project away from dome plate132to define generally conical or funnel-shaped areas188around first and second openings148,150opposite first and second cups144,146. Similar attachment features as described above with respect toFIGS. 6A and 6B or 7A-7Cmay be used to couple heat shield114having conical areas188to dome plate132.

Turning now toFIGS. 9 and 10, another embodiment of a combustor assembly according to the present subject matter is illustrated. As shown schematically inFIG. 9, in some embodiments, the combustor assembly may include a heat shield220comprising a single cup222that defines a cup centerline CL2extending generally along or parallel to the axial direction A. That is, a single cup heat shield220, rather than heat shield114having multiple cups such as first and second cups144,146described above, may be used with combustor dome100. In such embodiments, a collar224having a single frame may be used with each cup222of heat shield220rather than a collar160having multiple frames such as frames162,164previously described. Additionally or alternatively, a single frame collar224may be used with each cup of a multi-cup heat shield114, e.g., rather than a multi-frame collar160.

Similar to collar160described above, collar224is attachable to the heat shield220for coupling the heat shield220to the combustor dome100. Collar224includes a first half or piece224aand a second half or piece224b. When assembled with heat shield220, the first piece224aextends about a portion of the cup222defined by heat shield220such that the first piece224apartially surrounds the cup222. Likewise, the second piece224bextends about the remaining portion of cup222such that the second piece224bpartially surrounds the cup222. In exemplary embodiments, collar224is split into the two halves224a,224balong a collar centerline, and the collar224is generally annular or ring-shaped such that each half224a,224bis generally a half ring shape or extends in a 180° arc. In other embodiments, the collar224may be split into unequal pieces, e.g., one piece224aor224bmay extend in an arc of more than 180° while the other piece224aor224bextends in an arc of less than 180°. In still other embodiments, the collar224may be split into more than two pieces, e.g., three generally wedge or pie-shaped pieces or the like. In any event, like collar160, because collar224is split such that it is not a single piece collar, the collar224may be described as a split-ring collar.

Referring particularly toFIGS. 10 and 11,FIG. 10provides a close-up view of a portion of the combustor assembly ofFIG. 9, andFIG. 11provides a perspective view of collar224in which the first piece224ais separated from the second piece224b. As illustrated, collar224defines a groove226about its outer perimeter such that first piece224adefines a first portion226aof the groove and second piece224bdefines a second portion226bof the groove. A snap ring228is positioned within the groove portions226a,226bforming groove226such that the snap ring228spans an interface230between the collar pieces224a,224b. The snap ring228may be a constricting snap ring for holding the collar pieces224a,224btogether, particularly as the collar224is installed in the combustor assembly. Of course, in some embodiments, the collar224may be a non-round or non-annular shape such that the snap ring228has a non-ring shape but still serves to hold together the first and second pieces224a,224bof collar224.

As shown inFIG. 10, collar224has a generally C- or U-shaped cross-section. More particularly, collar224includes a first arm232, a second arm234, and a body236that connects the first arm232and the second arm234. As depicted inFIG. 10, the first arm232, second arm234, and body236define the generally C- or U-shaped cross-section of collar224. Further, body236connects first and second arms232,234such that the collar224defines a recess238between the first arm232and the second arm234.

It will be appreciated that, because the first piece224acomprises one piece of collar224and the second piece224bcomprises the second piece of collar224, each piece224a,224bincludes a portion of the first arm232, a portion of the second arm234, and a portion of the body236such that each piece224a,224bdefines a portion of the recess238between the first and second arms232,234. More specifically, as shown in most clearly inFIG. 11, first piece224aof collar224includes a first piece232aof first arm232, a first piece234aof second arm234, a first piece236aof body236, and a first piece238aof recess238. Similarly, second piece224bof collar224includes a second piece232bof first arm232, a second piece234bof second arm234, a second piece236bof body236, and a second piece238bof recess238.

As illustrated inFIGS. 9 and 10, an attachment piece166may be included to help couple the heat shield220to combustor dome100. As previously described, attachment piece166may be threaded to engage threads defined in the combustor dome100, or in a retainer nut101that, together with a spacer103, interfaces with dome100, and thereby couple heat shield220to the combustor dome100. Of course, in other embodiments, attachment piece166may have other configurations or features to help attach heat shield220to combustor dome100.

Referring particularly toFIG. 10, the heat shield220defines a heat shield flange240around an outer perimeter of the cup222, and the attachment piece166defines an attachment flange194, as described above. Collar224fits around both the heat shield flange240and attachment flange194to couple the attachment piece166to heat shield220. That is, heat shield flange240and attachment piece flange194are positioned within recess238of collar224to couple the heat shield220and the attachment piece166. The first arm232of collar224defines a first mating surface242that contacts a heat shield mating surface244defined by heat shield flange240. Similarly, the second arm234of collar224defines a second mating surface246that contacts an attachment mating surface196defined by attachment piece166. One or more seals and/or washers, such as a flat washer200and a wave seal202described above with respect toFIG. 6C, may be included within recess238, e.g., between the heat shield flange240and attachment piece flange194such that the seals and/or washers help to hold heat shield mating surface244against first mating surface242of collar224and to hold attachment mating surface196against second mating surface246of collar224, which can help prevent hot gas leakage between the heat shield220and attachment piece166. Additionally or alternatively, the seals and/or washers may help mitigate wear between heat shield220and attachment piece166and/or may otherwise provide a seal to help prevent hot gas leakage between heat shield220and attachment piece166. The leakage of hot gas between the heat shield220and attachment piece166could decrease the effectiveness of the heat shield in protecting combustor dome100from exposure to the hot combustion gases. Moreover, the seals and/or washers included within recess238also may compensate for variations in part dimensions and/or differences in thermal expansion between collar224and heat shield220and attachment piece166, e.g., to help to hold heat shield mating surface244against first mating surface242of collar224and to help to hold attachment mating surface196against second mating surface246of collar224.

Further, as previously described, at least a portion of attachment piece166, such as a portion of an outer surface of the attachment piece, may be threaded to help couple the heat shield220to combustor dome100. For example, the threads of the attachment piece166may threadingly engage combustor dome100directly or, as shown inFIGS. 9 and 10, may threadingly engage one or more components such as retainer nut101and spacer103that attach the attachment piece166to the dome100. Of course, attachment piece166may attach to combustor dome100in other ways as well.

The combustor assembly also may include one or more features for keeping its components properly oriented with respect to one another. For example, the heat shield220preferably is a CMC component, and collar224, attachment piece166, and combustor dome100may be metallic components. As such, the rates of thermal expansion may vary between the components, particularly between the CMC component and the metallic components, such that the components may shift and/or rotate with respect to one another as the temperature of the combustion assembly increases. Accordingly, the combustor assembly may include features for maintaining the components oriented with respect to one another.

For example, as most clearly shown inFIG. 10, the combustor dome100defines a dome pocket248and the collar224defines a collar pocket250. The collar pocket250aligns with the dome pocket248such that a pin252may be positioned within the dome pocket248and collar pocket250to hold the collar224, and thereby heat shield220, in position with respect to combustor dome100. More specifically, a portion of pin252is positioned in the dome pocket248and a remaining portion of pin252is received in the collar pocket250such that pin252is positioned within both pockets248,250. It will be appreciated that pockets248,250may be defined in any appropriate locations within combustor dome100and collar224, respectively, and may be of any suitable size and shape. Further, some embodiments of the combustor assembly may define more than one dome pocket248and more than one collar pocket250such that multiple pin and pocket features are utilized to orient the collar224with respect to the combustor dome100. Thus, the pocket features248,250together with pin252may be included in the combustor assembly for keeping heat shield220and combustor dome100properly oriented with respect to one another. As discussed above, such features may be particularly useful for embodiments in which the heat shield220is made from a CMC material and combustor dome100is made from a metallic material such that the heat shield and dome have different coefficients of thermal expansion and thermally expand at different rates.

As another example, referring toFIGS. 10 and 11, the heat shield flange240may include a projection254extending toward the collar224, and the collar224may define a slot256for receipt of the projection254. In some embodiments, the heat shield flange240may include a tab-like projection at one or more locations about its outer perimeter or rim, and the collar224may define one or more slots256, wherein each slot256is configured to receive a projection254of the heat shield flange240. The heat shield flange projection254and collar slot256may be included at any suitable location of flange240and collar224, respectively. In an exemplary embodiment, the collar224may define slot256such that a portion of slot256is defined by the first piece224aof collar224and a remaining portion of slot256is defined by the second piece224bof collar224. Thus, the heat shield flange240may define a projection254such that when the projection254is received within the slot256, the projection spans the interface230between the first and second pieces224a,224bof collar224. Additionally or alternatively, each piece224a,224bof collar224may fully, rather than partially, define a slot256that receives a projection254of heat shield flange240. It will be understood that collar224and heat shield220may define any appropriate number of slots256and projections254, respectively, such that the heat shield220and collar224may each include one or more features for keeping the heat shield and collar properly oriented with respect to one another. As previously stated, such features may be particularly beneficial in embodiments in which the heat shield220is made from a CMC material and collar224is made from a metallic material such that the heat shield and collar have different coefficients of thermal expansion and thermally expand at different rates.

Although described with respect to a single or individual heat shield cup222, it will be appreciated that the description of the combustor assembly depicted inFIGS. 9 through 11also may apply to multi-cup heat shield designs utilizing collars having multiple rings or frames. For example, in some embodiments, a double split-ring collar may be used that has one or more collar pockets, and the combustor dome may define one or more dome pockets, such that a pin may be partially received in each dome pocket and the remainder of each pin received in a corresponding collar pocket to help hold the collar in position with respect to the combustor dome.

FIG. 12provides a flow diagram illustrating a method1200for forming a CMC component, such as a CMC heat shield, according to an exemplary embodiment of the present subject matter. As previously described, heat shield114may be made from a CMC material, which is a non-metallic material having high temperature capability. As such, CMC materials may be beneficial for use in forming parts of combustor assembly79, e.g., heat shield114, that are exposed to the hot combustion gases. However, although method1300is described below with respect to forming a CMC heat shield114, it will be appreciated that method1300may be applicable to forming other components of combustor assembly79and turbofan engine10.

As shown at1202inFIG. 12, a plurality of plies of a CMC material for forming the CMC component may be laid up to form a CMC component 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 component preform may be a desired shape or contour of the resultant CMC component. As an example, the plies may be laid up to define a shape of CMC component preform that is the shape of heat shield114, such as the heat shield shown inFIG. 4or inFIG. 8B, or heat shield220shown inFIGS. 9 and 10. In one embodiment, laying up the plurality of plies may include stacking plies to define pad168about a perimeter of the heat shield preform, such that the pad168comprises a stack of plies of the CMC material. Laying up the plurality of plies also may include defining a flange192extending about first cup144and second cup146. Laying up the plurality of plies to form the heat shield preform may include defining other features of heat shield114as well, or may include defining features of heat shield220such as cup222having flange240.

The exemplary double cup heat shields114described above define a relatively large area for positioning a perimeter seal and with relatively simple features for coupling the heat shields to a combustor dome. Therefore, the plurality of plies of CMC material for forming such heat shields114may have more reasonable or less complex ply shapes than known or former heat shield configurations, which may simplify the layup process and thereby simplify the fabrication of CMC heat shields114. Similarly, the exemplary single cup heat shields220also may have simpler or less complex shapes and attachment features than known single cup or other heat shield designs, which may simplify the layup process and thereby simplify the fabrication of CMC heat shields220.

After the plurality of plies is laid up, the plies may be processed, e.g., compacted and cured in an autoclave, as shown at1204inFIG. 12. After processing, the plies form a green state CMC component, e.g., a green state CMC heat shield114or a green state heat shield220. The green state CMC component is a single piece component, i.e., curing the plurality of plies joins the plies to produce a CMC component formed from a continuous piece of CMC material. The green state component then may undergo firing (or burn-off) and densification, illustrated at1206and1208inFIG. 12, to produce a final CMC component. In an exemplary embodiment of method1200, the green state component is placed in a furnace with silicon to burn off any mandrel-forming materials and/or solvents used in forming the CMC plies, to decompose binders in the solvents, and 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 1300° C. to allow silicon or another appropriate material or materials to melt-infiltrate into the component. Optionally, as shown at1210inFIG. 12, after firing and densification the CMC component may be finish machined, if and as needed, and/or coated with an environmental barrier coating (EBC).

Method1200is provided by way of example only. For example, other processing cycles, e.g., utilizing other known methods or techniques for compacting and/or curing CMC plies, may be used. Further, the CMC component may be post-processed or densified using any appropriate means. Alternatively, any combinations of these or other known processes may be used as well.