Micromixing cap assembly

A system includes a combustor cap assembly for a multi-tube fuel nozzle. The combustor cap assembly includes a support structure defining an interior volume configured to receive an air flow, a plurality of mixing tubes disposed within the interior volume, wherein each of the plurality of mixing tubes comprises a respective fuel injector and is individually removable from the combustor cap assembly, an air distributor disposed within the interior volume and configured to distribute the air flow received by the interior volume to each of the plurality of mixing tubes, and a combustor cap removably coupled to the support structure.

BACKGROUND

The subject matter disclosed herein relates generally to turbine combustors, and, more particularly to a cap for the turbine combustors.

A gas turbine engine combusts a mixture of fuel and air to generate hot combustion gases, which in turn drive one or more turbine stages. In particular, the hot combustion gases force turbine blades to rotate, thereby driving a shaft to rotate one or more loads, e.g., an electrical generator. The gas turbine engine includes a fuel nozzle assembly, e.g., with multiple fuel nozzles, to inject fuel and air into a combustor. The design and construction of the fuel nozzle assembly can significantly affect the mixing and combustion of fuel and air, which in turn can impact exhaust emissions (e.g., nitrogen oxides, carbon monoxide, etc.) and power output of the gas turbine engine. Furthermore, the design and construction of the fuel nozzle assembly can significantly affect the time, cost, and complexity of installation, removal, maintenance, and general servicing. Therefore, it would be desirable to improve the design and construction of the fuel nozzle assembly.

BRIEF DESCRIPTION

In a first embodiment, a system includes a combustor cap assembly for a multi-tube fuel nozzle. The combustor cap assembly includes a support structure defining an interior volume configured to receive an air flow, a plurality of mixing tubes disposed within the interior volume, wherein each of the plurality of mixing tubes comprises a respective fuel injector and is individually removable from the combustor cap assembly, an air distributor disposed within the interior volume and configured to distribute the air flow received by the interior volume to each of the plurality of mixing tubes, and a combustor cap removably coupled to the support structure.

In a second embodiment, a combustor cap assembly for a multi-tube fuel nozzle includes a support structure defining an interior volume configured to receive an air flow, and an air distributor plate. The air distributor plate includes a plurality of apertures, wherein each of the plurality of apertures is configured to receive one of a plurality of mixing tubes, and a plurality of air passages configured to distribute the air flow to the plurality of mixing tubes.

In a third embodiment, a system includes a combustor cap assembly for a multi-tube fuel nozzle. The combustor cap assembly includes a support structure defining an interior volume, wherein the interior volume is configured to receive an air flow; a plurality of mixing tubes disposed within the interior volume, wherein each of the plurality of mixing tubes is configured to receive the air flow from the interior volume, and each of the plurality of mixing tubes is individually removable from the combustor cap assembly; a plurality of fuel injectors, wherein each of the plurality of fuel injectors is at least partially disposed within a respective one of the plurality of mixing tubes and is configured to inject a fuel flow into the respective one of the mixing tubes; an air distributor disposed within the interior volume, wherein the air distributor comprises a plurality of air passages configured to distribute the air flow within the interior volume to the plurality of mixing tubes; and a combustor cap removably coupled to the support structure.

DETAILED DESCRIPTION

The present disclosure is directed to a fuel and air premixing system for a gas turbine combustor. For example, the fuel and air premixing system may include a cap assembly, wherein the cap assembly includes a support structure defining an interior volume configured to receive an air flow, a plurality of mixing tubes, an air distributor, and a removable combustor cap. In some embodiments, the cap may be attached to the combustor with a radial spring, and may condition an inlet air flow to improve the quality of premixing air and fuel in the mixing tubes. The presently described system may provide lower manufacturing costs, easier repair procedures, longer equipment lifetime, and/or lower emissions, for example.

Turning to the drawings,FIG. 1illustrates a block diagram of an embodiment of a gas turbine system10. As described in detail below, the disclosed turbine system10may employ a cap assembly that includes a removable cap face, a retainer plate, and/or a distributor plate. As shown, the system10also includes a compressor12, a turbine combustor14, and a turbine16. The turbine combustor14may include one or more mixing tubes18, e.g., in one or more multi-tube fuel nozzles, configured to receive both fuel20and pressurized oxidant22, such as air, oxygen, oxygen-enriched air, oxygen reduced air, or any combination thereof. Although the following discussion refers to the oxidant as the air22, any suitable oxidant may be used with the disclosed embodiments. The mixing tubes may be described as micromixing tubes, which may have diameters between approximately 0.5 to 2, 0.75 to 1.75, or 1 to 1.5 centimeters. The mixing tubes18may be arranged in one or more bundles of closely spaced tubes, generally in a parallel arrangement relative to one another. In this configuration, each mixing tube18is configured to mix (e.g., micromix) on a relatively small scale within each mixing tube18, which then outputs a fuel-air mixture into the combustion chamber. In certain embodiments, the system10may include between 10 and 1000 mixing tubes18, and the system10may use a liquid fuel and/or gas fuel20, such as natural gas or syngas. Furthermore, the combustor14may contain the cap assembly noted above and described in more detail inFIG. 2, which may include a removable cap face, a removable retainer plate, and/or a distributor plate. The cap assembly may condition the flow of the pressurized air22to improve the uniformity of the distribution to the mixing tubes18, and may be removed to allow for inspection, maintenance, and/or removal of the mixing tubes18and other components of the combustor14, including the cap assembly itself.

Compressor blades are included as components of the compressor12. The blades within the compressor12are coupled to a shaft24, and will rotate as the shaft24is driven to rotate by the turbine16, as described below. The rotation of the blades within the compressor12compresses air32from an air intake30into pressurized air22. The pressurized air22is then fed into the mixing tubes18of the turbine combustors14. The pressurized air22and fuel20are mixed within the mixing tubes18to produce a suitable fuel-air mixture ratio for combustion (e.g., a combustion that causes the fuel to more completely burn) so as not to waste fuel20or cause excess emissions.

The turbine combustors14ignite and combust the fuel-air mixture, and then pass hot pressurized combustion gasses34(e.g., exhaust) into the turbine16. Turbine blades are coupled to the shaft24, which is also coupled to several other components throughout the turbine system10. As the combustion gases34flow against and between the turbine blades in the turbine16, the turbine16is driven into rotation, which causes the shaft24to rotate. Eventually, the combustion gases34exit the turbine system10via an exhaust outlet26. Further, the shaft24may be coupled to a load28, which is powered via rotation of the shaft24. For example, the load28may be any suitable device that may generate power via the rotational output of the turbine system10, such as an electrical generator, a propeller of an airplane, and so forth. In the following discussion, reference may be made to an axial axis or direction36, a radial axis or direction38, and/or a circumferential axis or direction40of the turbine system10.

FIG. 2is a cross-sectional schematic of an embodiment of the combustor14ofFIG. 1having a cap assembly60. The cap assembly60includes a removable cap face62, a retainer plate64, and an air distributor plate66. As shown, the combustor14further includes a combustion chamber68and a head end70. A plurality of the mixing tubes18are positioned within the head end70of the combustor14. The mixing tubes18may generally extend between the cap face62and an end cover72and may extend in the axial direction36. In some embodiments, the mixing tubes18are suspended in the head end70such that the mixing tubes18may not be attached to the end cover72or the cap face62. Alternatively, however, the mixing tubes18may be coupled to at least one of the cap face62and/or the end cover72, as further described below. In addition, the mixing tubes18may pass through the air distributor plate66, which may provide structural and vibrational damping support to the mixing tubes18. As such, the distributor plate may have apertures that correspond to mixing tubes18, such that the mixing tubes18may extend through the distribution plate66. The distribution plate66may be removably coupled to a support structure106, which may be a barrel shaped structure that extends circumferentially about the mixing tubes18, the retainer plate64, the air distributor plate66, and other components of the combustor14. The end cover72may also include a fuel plenum74for providing fuel20to the mixing tubes18. The fuel plenum74routes fuel to the mixing tubes18in the axial direction36, whereas the mixing tubes18receive air in the radial direction38. The cap face62may be removably coupled to the head end70of the combustor14(e.g., with a radial spring or with fasteners such as bolts) so that it may be detached from the support structure106. Furthermore, the retainer plate64may be coupled to the support structure106upstream of the cap face62. Like the cap face62, the retainer plate64may be removably coupled (e.g., bolted, threaded, etc.) to the support structure106such that it may be removed to allow for inspection, maintenance, and/or removal of the mixing tubes18and other components of the head end70. As described in more detail below, the retainer plate64may provide additional support for a second end112of the mixing tubes18. As mentioned above, one or more components of the cap assembly60may be removed from the support structure106in order to enable inspection, maintenance, and/or removal of the components of the cap assembly60as well as various components of the combustor14, including the mixing tubes18.

As described above, the compressor12receives air32from the air intake30, compresses the air32, and produces the flow of pressurized air22for use in the combustion process. As shown by arrow76, the pressurized air22is provided to the head end70of the combustor14through an air inlet78, which directs the air laterally or radially38inward towards side walls of the mixing tubes18. More specifically, the pressurized air22flows in the direction indicated by arrow76from the compressor12through an annulus80between a liner82and a flow sleeve84of the combustor14to reach the head end70. The liner82is positioned circumferentially about combustion chamber68, the annulus80is positioned circumferentially about liner82, and the flow sleeve84is positioned circumferentially about the annulus80. Upon reaching the head end70, the air22turns from the axial direction36to the radial direction38through the inlet78toward the mixing tubes18, as indicated by arrows76.

The pressurized air22passes through the distributor plate66, enters each of the mixing tubes18through one or more openings, and is mixed with the fuel20within the plurality of mixing tubes18. As will be appreciated, the air distributor plate66may increase the uniformity of the air22passing into the mixing tubes18. Each mixing tube18receives the fuel20in the axial direction36through an axial end portion of the mixing tube18, while also receiving the air22through a plurality of side openings in the mixing tube18. Thus, the fuel20and the air22mix within each individual mixing tube18. As shown by arrows86, the fuel-air mixture flows downstream within the mixing tubes18into the combustion chamber68, where the fuel-air mixture is ignited and combusted to form the combustion gases34(e.g., exhaust). The combustion gases34flow in a direction88toward a transition piece90of the turbine combustor14. The combustion gases34pass through the transition piece90, as indicated by arrow92, toward the turbine16, where the combustion gases34drive the rotation of the blades within the turbine16.

The cap assembly60, including the cap face62, the retainer plate64, and/or the air distributor plate66, may be configured to be removed to enable inspection, maintenance, and/or removal of components of the combustor14, including the mixing tubes18. In addition, the air distributor plate66may improve the uniformity of air22flow to the mixing tubes18, which may increase the efficiency of combustion and reduce emissions (NOx) of the turbine system10. The cap assembly60may therefore extend the life cycle of the combustor14and reduce its lifetime costs.

FIG. 3is a cross-sectional side view of a portion of the plurality of mixing tubes18and the cap assembly60within the combustor14. As described above, the cap assembly60includes the cap face62, the retainer plate64, and the distributor plate66. The cap face62includes a lip102, which extends in an upstream direction from the outer edge of the cap face62. This lip102is configured to fit over a radial spring104, located on the support structure106. The lip102and the radial spring104are configured to have similar radii (for example, the radius of the lip102may be the same or slightly smaller than the radius of the radial spring104) such that the lip102may be fitted over the radial spring104to form a compression or spring-biased fit. The radial spring104may have a radially outward bias, so that it may compress in order to hold the lip102and the cap face62in place to block fluid leakage between the lip102and the radial spring104.

As shown, each mixing tube18has a passage or chamber108extending between a first end110(e.g., axial end opening) and a second end112(e.g., axial end opening) of the mixing tube18. In some embodiments, the second end112of the mixing tube18may extend through the cap face62, so that the fuel-air mixture may be output from the mixing tube18into the combustion chamber68through an axial end opening generally located at the second end112of the mixing tube18.

In some embodiments, the end cover72may be positioned upstream of, and proximate to, the first end110of the mixing tube18. The end cover72may include one or more fuel inlets114through which the fuel20is provided to one or more fuel plenums74(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) within the end cover72. Furthermore, each fuel plenum74may be fluidly connected to one or more fuel injectors116(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more). As illustrated, each mixing tube18includes a respective fuel injector116, which receives the fuel20in the axial direction36as indicated by arrows117. In some embodiments, the end cover72may include a single common fuel plenum74(e.g., fuel supply chamber) for all of the mixing tubes18and associated fuel injectors116. In other embodiments, the system10may include one, two, three, or more fuel plenums74that each provides fuel20to a subgroup of fuel injectors116, and ultimately to the mixing tube18associated with each fuel injector116. For example, one fuel plenum74may provide fuel to about 5, 10, 50, 100, 500, 1000, or more fuel injectors116. In some embodiments, the combustor14having subgroups of fuel injectors116supplied by different fuel plenums74may allow one or more subgroups of fuel injectors116and corresponding mixing tubes18to be run richer or leaner than others, which in turn may allow for more control of the combustion process, for example. Additionally, multiple fuel plenums74may enable the use of multiple types of fuel20(e.g., at the same time) with the combustor14.

As shown inFIG. 3, the support structure106(e.g., side wall) may circumferentially surround the head end70of the combustor14, and the support structure106may generally protect and/or support the mixing tubes18and other structures within the head end70, such as the retainer plate64and the distributor plate66. As described above, in some embodiments, pressurized air22may enter the head end70through an air inlet78. More specifically, pressurized air22may flow through the air inlet78laterally into an air cavity118within the head end70(e.g., in a generally radial direction38as indicated by arrow122). The air cavity118includes the volume of space in between the plurality of mixing tubes18and surrounded by the support structure106(e.g., outer wall). The pressurized air22spreads throughout the air cavity118as the pressurized air22flows to each of the plurality of mixing tubes18.

In some embodiments, a flow distributor diffuser120(e.g., a baffle, a conduit, or turning vane) may be provided in the combustor14to improve distribution of the pressurized air22within the head end70. The diffuser120may be an annular flow conditioning diffuser120configured to distribute the pressurized air22forward, radially38inward, and/or externally across the plurality of mixing tubes18. For example, the diffuser120may include a tapered annular wall121, which gradually angles or curves inwardly toward the cavity118and mixing tubes18in the radial direction38. The diffuser120also may include an annular internal passage123, which generally diverges or grows in cross-sectional area toward the cavity118and the mixing tubes18. In some embodiments, the diffuser120may diffuse the pressurized air22such that the pressurized air22is substantially evenly distributed to each mixing tube18. Furthermore, the perforated air distributor plate66may also contribute to the distribution of the pressurized air22. The air distributor plate66may be provided within the cavity118of the head end70, and may generally be positioned between the end cover72and the cap face62. The perforations in the air distribution plate66may be of any of a variety of shapes and sizes, and may generally provide additional diffusion and distribution of the pressurized air22, so as to improve distribution of the pressurized air22to the mixing tubes18. After entering the head end70through the air inlet78, the pressurized air22may enter each mixing tube18through one or more apertures111formed in the mixing tubes18.

As shown inFIG. 3, in some embodiments, the combustor14also has the retainer plate64and an impingement plate128. The retainer plate64and the impingement plate128may be positioned downstream of the fuel injectors116and generally proximate to the cap face62. The cap face62, the retainer plate64, and/or the impingement plate128may be removable or separable from the support structure106, for example. The retainer plate64may provide support for the mixing tubes18, as it may be configured to couple to the downstream end (e.g., the second end112) of each mixing tube18. The impingement plate128may be positioned substantially adjacent to the cap face62, and in some embodiments, the impingement plate128may be positioned between the retainer plate64and the cap face62. The impingement plate128may support the mixing tubes18, and may additionally or alternatively provide for cooling of the cap face62within the combustor14.

As shown in more detail inFIG. 4, the air distributor plate66comprises apertures142through which the mixing tubes18may extend, as well as air passages144around the apertures142through which the pressurized air22may flow. The air passages144may generally provide additional diffusion and distribution of the pressurized air22in order to improve the uniformity of the flow of the pressurized air22to the mixing tubes18. For example, the distribution plate66may alter the velocity, the pressure, the angle, and/or other qualities of the pressurized air22in order to increase the uniformity of the distribution of the air22to the mixing tubes18. As shown, the pressurized air22may enter through the diffuser120and flow in a direction generally shown by arrow122as it flows across the air distributor plate66and into/across the mixing tubes18. The air distributor plate66may be perpendicular to the flow of the pressurized air22(e.g., may extend along the radial direction38), or it may be angled across the mixing tubes18. For example, the air distributor plate66may be angled at an angle θ1, as shown by dashed line124, or the plate66may be angled at an angle θ2, as shown by dashed line126, or at any other suitable angle. The dashed lines124and126depict the air distributor plate66angled with respect to the radial direction38, but it should be understood that the air distributor plate66may be angled along any axis of the air distributor plate66. In addition, the angles θ1and θ2may be any angle, such as approximately 5, 10, 30, 60, or 80 degrees relative to the radial direction38, or between 5 and 60, 10 to 45, or 30 to 30 degrees The air distributor plate66may be attached to the mixing tubes18, to the support structure106, or both, with radial springs (e.g., hula seals), bolts, brazing, or any other suitable method of coupling. In this way, the air distributor plate66may provide structural or vibrational damping support to the mixing tubes18as it distributes the pressurized air22to the mixing tubes18.

After entering the head end70through the air inlet78, the pressurized air22may enter each mixing tube18and its respective mixing chamber108through one or more apertures111formed in the mixing tubes18. The apertures111may be configured to have any of a variety of shapes, sizes, and arrangements. For example, the apertures111may be generally circular, elliptical, or rectangular in cross-sectional shape. The apertures111may further have a diameter or a dimension in the range of from approximately 0.001 centimeters to approximately 1.5 or more centimeters. The apertures111may also have a diameter or dimension in the range of from approximately 0.01 to 1.0, 0.05 to 0.5, or 0.1 to 0.25 centimeters. In some embodiments, one or more rows of apertures111may be spaced (e.g., evenly) around the circumference of each of the mixing tubes18. The apertures111formed in the mixing tubes18may have substantially similar, or common, shapes, sizes, and/or angles, while in other embodiments the apertures111may have different shapes, sizes, and/or angles. In general, the apertures111may be positioned at any location along the mixing tube18. However, in certain embodiments, the apertures111may be positioned upstream from the position at which the fuel20enters the mixing tube18through the fuel injector116. Furthermore, the apertures111may be spaced circumferentially around the fuel injector116, thereby directing the air radially inward toward the fuel injector116.

As discussed above and as shown inFIG. 3, one fuel injector116is provided for each mixing tube18of the combustor14. In other words, one fuel injector116is positioned within a portion of each mixing tube18in order to deliver fuel20into the respective mixing tube18. In some embodiments, the fuel injector116may be generally coaxially positioned within each mixing tube18by inserting the fuel injector116axially36through the first end110of each mixing tube18. Thus, the mixing tubes18may have a size, shape, and configuration to enable each mixing tube18to receive the corresponding fuel injector116. The cap assembly60, including the removable cap face62, the removable air distributor plate66, and/or the removable retainer plate64, may be removable to enable replacement of individual mixing tubes18, enable the replacement of the cap face62without also replacing the support structure106, and may improve the air distribution to the mixing tubes18. As such, the cap assembly60may increase the robustness of the gas turbine system10, thereby reducing the lifecycle cost of the system10.

FIG. 4illustrates an exploded cross-sectional side view of the cap assembly60, including the cap face62, the air distributor plate66, and the retainer plate64. As described above with respect toFIG. 3, the cap face62may be removably attached to the support structure106via the radial seal104(e.g., a hula seal) or some other fasteners (e.g., bolts). The lip102of the cap face62may be configured to slide over the radial seal104, which may extend around the circumference of the support structure106. The radial seal104may compress radially inward when the lip102is fitted over the seal104. The seal104may be configured to block fluid leakage across an interface between the radial seal104and the lip102, and the seal104may removably couple the cap face62to the support structure106. The retainer plate64may be removably coupled (e.g., bolted, threaded, etc.) to the support structure106upstream of the cap face62, so that it may be removed to enable inspection, maintenance, and/or removal of the mixing tubes18. The retainer plate64may also provide support for the mixing tubes18, which may be attached to the retainer plate64at their downstream ends112. The air distributor plate66may be a single piece or a multi-piece plate configuration, and the plate66may be located upstream of both the cap face62and the retainer plate64. Furthermore, the air distributor plate66may be located adjacent to or just upstream of the air diffuser120and the air inlet78. The air distributor plate66may help distribute the pressurized air22before it enters the mixing tubes18through the apertures111.

As noted above, in some embodiments, the air distributor plate66may be angled relative to an axis of each of the plurality of mixing tubes18or relative to the support structure106. Furthermore, the air distributor66may include a plurality of apertures142, which the mixing tubes18may be configured to extend through. Surrounding these apertures142may be a plurality of air passages144, through which the pressurized air22may flow. The air passages144may be small perforations around the apertures142, or they may be larger cutouts extending along or between the apertures142. The air passages144in the air distributor plate66may be of any of a variety of shapes and sizes, and may include venturi or contoured shapes which may reduce unwanted pressure drops as the pressurized air22flows across the air distributor plate66. For example, the air passages144may be generally circular, elliptical, polygonal, or rectangular in cross-sectional shape, and may extend between or along mixing tubes18. The air passages144may have a diameter or dimension in the range of from approximately 0.001 centimeters to approximately 1.5 or more centimeters. Furthermore, the air passages144may have substantially similar shapes, sizes, and arrangements, or they may have a variety of shapes, sizes, and arrangements. The air passages144and/or the apertures142may be contoured in order to temporarily restrict the pressurized air22as it passes through the air passages144in order to increase the velocity of the pressurized air22as it flows across the air distributor plate66.

In some embodiments, at least one aperture142may include a radial spring146, which may be configured to secure the mixing tube18which passes through it. The radial spring146may be engaged to tighten around the mixing tube18as it passes through the aperture142, and it may provide structural support to the mixing tube18. Additionally, the radial spring146may provide vibrational damping support to the mixing tube18, and may reduce vibrations, oscillations, or other movements experienced by the mixing tubes18. In other embodiments, another fastener between the mixing tubes18and the air distributor plate66may be used to provide structural and vibrational damping support to the mixing tubes18. The structural and vibrational damping support from the radial springs146may increase the robustness of the mixing tube18. As part of the cap assembly60, the air distributor plate66may increase the reliability and operability of the gas turbine system10, thereby reducing the life cycle costs of the gas turbine system10.

As shown, the components of the cap assembly60(e.g., the cap face62, the retainer plate64, and/or the air distributor plate66) may each be removed from the support structure106. This removable cap assembly60may allow access to the mixing tubes18, which may then be inspected, maintained, and/or removed individually. Furthermore, the components of the cap assembly60may be removed or replaced independently, and may not require the removal or replacement of other components of the turbine system10, such as the support structure106. The cap assembly60provides a more modular, easily replaceable, and serviceable configuration for the combustor14. Additionally, the cap assembly60may increase the robustness of the combustor14by increasing the ease of access to the components of the combustor (e.g., the mixing tubes18) and improving the pressurized air22distribution to the mixing tubes18via the air distribution plate66. More uniform pressurized air22distribution may increase the efficiency of the mixing of the fuel20and pressurized air22, which may lower the emissions (NOx) of the gas turbine system10(e.g., in hot pressurized combustion gasses34, or exhaust). By increasing the serviceability, operability, and robustness of the combustor14, the cap assembly60may increase the lifespan of the combustor14and reduce its operating and maintenance costs.

FIG. 5shows a partial axial view of the air distributor plate66, which illustrates the plurality of apertures142and air passages144. The air distributor plate66includes the apertures142through which the mixing tubes18may extend, as well as the air passages144configured to improve the pressurized air22distribution to the apertures111of the mixing tubes18. As noted above, the air passages144may extend along, between, or around the apertures142, and may have any of a variety of shapes, sizes, and arrangements. For example, the air passages144may generally be rectangular, circular, elliptical, polygonal, or triangular in cross-sectional shape, and the air passages144may extend along one, two, three, or more of the apertures142. Additionally, in certain embodiments, the air passages144may be fine perforations, as in a wire mesh. The air passages144may have a diameter from approximately 0.0001 centimeters to approximately 1.5 or more centimeters. In some embodiments, the air passages144may be distributed evenly around the apertures142, or the air passages144may extend along or between one or multiple apertures142. The air passages144may further be contoured to condition the pressurized air22to be better distributed by changing the pressure, angle, direction, or other qualities of the pressurized air22.

Furthermore, as shown inFIG. 5, some apertures142may include a radial spring146(e.g., a metal spring, a hula seal, a fabric ring, etc.), which may extend around the inner circumference or dimension of the aperture142. The radial spring146may provide structural support and vibrational damping support to the mixing tube18, which may pass through the aperture142. Furthermore, the air passages144may be contoured or have shapes that may reduce unwanted pressure drops or may condition the pressurized air22flow to reduce aft side wakes. The air distributor plate66may cause the pressurized air22to distribute more evenly to the mixing tubes18and may, in spreading and conditioning the air22, increase the uniformity of the temperature of the pressurized air22. This may contribute to a more uniform pressurized air-fuel mixture in each mixing tube18. By altering the flow of the pressurized air22, the air distributor plate66may improve the quality of the air flow to the mixing tubes18and/or increase the uniformity of the temperature of the pressurized air22as it distributes to the mixing tubes18.

FIG. 6illustrates a partial view of an embodiment of the air distributor plate66, having a contoured opening (e.g., aperture142). As shown inFIG. 6, the mixing tube18may pass through the aperture142in the air distributor plate66. The aperture142may be configured to temporarily narrow in between an entrance148to the aperture142and an exit150from the aperture142. For example, the aperture142may be configured to have a venturi contouring that includes a converging portion, a throat portion, and a diverging portion. The pressurized air22may flow as indicated by arrow152through the aperture142. The temporary narrowing of the aperture142in between the entrance148and the exit150of the aperture142may reduce the pressure of the pressurized air22passing through the aperture142and increase the velocity of the pressurized air22. In other words, as the pressurized air22flows through the aperture142, it may be constricted by a decrease in the cross-sectional radius or dimensions of the aperture142. It should be understood that the apertures142or the air passages144may utilize such contouring in order to condition the flow of the pressurized air22as it is distributed to the mixing tubes18. For example, in the embodiment shown inFIG. 6, the pressurized air22may flare away from the mixing tube18as it flows through the aperture142, as indicated by arrow152. Conditioning with venturi or other contours may increase the velocity of the pressurized air22or may otherwise condition the pressurized air22as it flows through the aperture142to improve the pressurized air22distribution. In this manner, temperature uniformity of the pressurized air22entering the mixing tubes18, among other things, may be improved. Improving the pressurized air22distribution and increasing temperature uniformity may increase the efficiency of fuel20and pressurized air22mixing, thereby increasing the efficiency and operability of the gas turbine system10.

As described above, the disclosed embodiments include the combustor cap assembly60, which may include the cap face62, the retainer plate64, and the air distributor plate66. For example the cap face62may be removably coupled to the support structure106, and the retainer plate64and the air distributor plate66may be removably coupled to the plurality of mixing tubes18in the head end70of the combustor14. Additionally, the air distributor plate66may improve the distribution of pressurized air22across the mixing tubes18, and the cap assembly60may be configured to be removable, which may enable maintenance, inspection, and/or removal of other components of the combustor14.