Patent Description:
The present application claims filing benefit of <CIT>.

The present disclosure generally relates to a segmented combustion system for use in a gas turbine. An exemplary prior art gas turbine combustor is described in <CIT>. More particularly, this disclosure relates to a segmented combustion system having multiple panel fuel injectors.

Industrial gas turbine combustion systems usually burn hydrocarbon fuels and produce air polluting emissions such as oxides of nitrogen (NOx) and carbon monoxide (CO). Oxidization of molecular nitrogen in the gas turbine depends upon the temperature of gas located in a combustor, as well as the residence time for reactants located in the highest temperature regions within the combustor. Thus, the amount of NOx produced by the gas turbine may be reduced or controlled by either maintaining the combustor temperature below a temperature at which NOx is produced, or by limiting the residence time of the reactant in the combustor.

One approach for controlling the temperature of the combustor involves pre-mixing fuel and air to create a fuel-air mixture prior to combustion. This approach may include the axial staging of fuel injectors where one or more injectors are located at an upstream end of the combustor and one or more injectors are located at an axially downstream location. The upstream injectors inject a first fuel-air mixture into a first or primary combustion zone where it is ignited to produce a main flow of high energy combustion gases. A second fuel-air mixture is injected into and mixed with the main flow of high energy combustion gases via a plurality of radially oriented and circumferentially spaced fuel injectors or axially staged fuel injector assemblies positioned downstream from the primary combustion zone.

Axially staged injection increases the likelihood of complete combustion of available fuel, which in turn reduces the air polluting emissions. However, with conventional axially staged fuel injection combustion systems there are various challenges with balancing air flow to the various combustor components, air flow requirements to the head end of the combustor for the first fuel-air mixture and/or compressed air flow to the axially staged fuel injectors for the second fuel-air mixture while maintaining emissions compliance over the full range of operation of the gas turbine. Therefore, an improved gas turbine combustion system which includes axially staged fuel injection would be useful in the industry.

Aspects and advantages are set forth below in the following description, or may be obvious from the description, or may be learned through practice. An annular combustion system according to the herein claimed invention is defined in claim <NUM>.

The herein claimed invention is defined in the appended claims.

A full and enabling disclosure of the various embodiments, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:.

Reference will now be made in detail to present embodiments of the disclosure, one or more examples of which are illustrated in the accompanying drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the disclosure.

The term "radially" refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, the term "axially" refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component and the term "circumferentially" refers to the relative direction that extends around the axial centerline of a particular component.

Each example is provided by way of explanation, not limitation. In fact, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope of the appended claims. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the claims and their equivalents.

Although exemplary embodiments of the present disclosure will be described generally in the context of a segmented annular combustion system for a land-based power-generating gas turbine for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present disclosure may be applied to any type of turbomachine and are not limited to annular combustion systems for land-based power-generating gas turbines unless specifically recited in the claims.

Referring now to the drawings, <FIG> illustrates a schematic diagram of an exemplary gas turbine <NUM>. The gas turbine <NUM> generally includes an inlet section <NUM>, a compressor <NUM> disposed downstream of the inlet section <NUM>, a combustion section <NUM> disposed downstream of the compressor <NUM>, a turbine <NUM> disposed downstream of the combustion section <NUM> and an exhaust section <NUM> disposed downstream of the turbine <NUM>. Additionally, the gas turbine <NUM> may include one or more shafts <NUM> that couple the compressor <NUM> to the turbine <NUM>.

During operation, air <NUM> flows through the inlet section <NUM> and into the compressor <NUM> where the air <NUM> is progressively compressed, thus providing compressed air <NUM> to the combustion section <NUM>. At least a portion of the compressed air <NUM> is mixed with a fuel <NUM> within the combustion section <NUM> and burned to produce combustion gases <NUM>. The combustion gases <NUM> flow from the combustion section <NUM> into the turbine <NUM>, wherein energy (kinetic and/or thermal) is transferred from the combustion gases <NUM> to rotor blades (not shown), thus causing shaft <NUM> to rotate. The mechanical rotational energy may then be used for various purposes such as to power the compressor <NUM> and/or to generate electricity. The combustion gases <NUM> exiting the turbine <NUM> may then be exhausted from the gas turbine <NUM> via the exhaust section <NUM>.

<FIG> provides an upstream view of the combustion section <NUM>, according to various embodiments of the present disclosure. As shown in <FIG>, the combustion section <NUM> may be at least partially surrounded by an outer or compressor discharge casing <NUM>. The compressor discharge casing <NUM> may at least partially define a high pressure plenum <NUM> that at least partially surrounds various components of the combustion section <NUM>. The high pressure plenum <NUM> may be in fluid communication with the compressor <NUM> (<FIG>) so as to receive the compressed air <NUM> therefrom.

In various embodiments, as shown in <FIG>, the combustion section <NUM> includes a segmented annular combustion system <NUM>. As shown in <FIG>, the segmented annular combustion system <NUM> includes a series of fuel nozzles <NUM> and a corresponding series of hollow or semi-hollow panel fuel injectors <NUM> arranged in alternating fashion in an annular array about an axial centerline <NUM> of the combustion section <NUM>. The panel fuel injectors <NUM> extend radially (with respect to centerline <NUM>) between an inner liner <NUM> and an outer liner <NUM>, which form a radially inner and a radially outer combustion gas flow boundary within the combustion section <NUM>. The fuel nozzles <NUM> are disposed between the inner liner <NUM> and the outer liner <NUM>, though not necessarily extending across an entire radius therebetween.

<FIG> provides a downstream or aft side view of a portion of the segmented annular combustion system <NUM>, according to at least one embodiment of the present disclosure. <FIG> provides an upstream or forward side view of a portion of the segmented annular combustion system <NUM>, according to at least one embodiment of the present disclosure. In particular embodiments, as shown in <FIG> collectively, each panel fuel injector <NUM> circumferentially separates two circumferentially adjacent fuel nozzles <NUM>. In the embodiments illustrated herein, the fuel nozzles <NUM> are shown and described as bundled tube fuel nozzles, but it should be clear that other types of fuel nozzles may be used instead. For example, one or more fuel nozzles (e.g., swozzles) or burners may be mounted in a cap face segment (not shown separately) that extends radially between the inner liner <NUM> and the outer liner <NUM> and that extends circumferentially between adjacent panel fuel injectors <NUM>. Any reference to "bundled tube fuel nozzle <NUM>" is intended to encompass any type of fuel nozzle, unless context dictates otherwise.

In particular embodiments, as shown in <FIG>, a seal <NUM> such as a floating collar seal, spring seal, or hula seal may be attached to a side wall of one or more of the bundled tube fuel nozzles <NUM>. In particular embodiments, as shown in <FIG>, a seal <NUM> such as a floating collar seal, spring seal, or hula seal may be attached to a side wall of one or more of the panel fuel injectors <NUM>. The seals <NUM>, <NUM> may be used to prevent, reduce and/or control air leakage between adjacent bundled tube fuel nozzles <NUM> and respective panel fuel injectors <NUM> during operation of the combustion section <NUM>.

In particular embodiments, as shown in <FIG>, <FIG> collectively, the segmented annular combustion system <NUM> may be subdivided into individual combustor segments <NUM>. Each combustor segment <NUM> may include two or more (bundled tube) fuel nozzles <NUM> and at least one panel fuel injector <NUM>. In particular embodiments, as illustrated in <FIG> and <FIG>, the inner liner <NUM> and/or the outer liner <NUM> may be subdivided into multiple sections which correspond with one or more of the combustor segments <NUM>.

<FIG> provides a perspective view of an exemplary combustor segment <NUM>, according to at least one embodiment of the present disclosure. In particular embodiments, as shown in <FIG>, one or more of the combustor segments <NUM> may be coupled to an end cover <NUM>, which is formed to couple to and/or seal against the compressor discharge casing <NUM> (<FIG>) of the combustion section <NUM>. In particular embodiments, the bundled tube fuel nozzles <NUM> may be fluidly coupled to the end cover <NUM> and/or a fuel supply (not shown) via one or more fluid conduits <NUM>. In particular embodiments, one or more of the panel fuel injectors <NUM> may be fluidly coupled to the end cover <NUM> and/or a fuel supply (not shown) via one or more fluid conduits <NUM>.

<FIG> provides a cross-sectioned perspective view of a portion of an exemplary bundled tube fuel nozzle <NUM>, taken along section line A-A as shown in <FIG>, according to at least one embodiment of the present disclosure. In various embodiments, as shown in <FIG>, the bundled tube fuel nozzle <NUM> includes a housing body <NUM>. The housing body <NUM> includes a forward or upstream plate or face <NUM>, an aft or downstream plate or face <NUM>, and an outer wall or shroud <NUM> that extends axially from and/or between the forward plate <NUM> and the aft plate <NUM> and that may define a radially outer perimeter of the bundled tube fuel nozzle <NUM>. A bundled tube fuel plenum <NUM> is defined within the housing body <NUM>. In particular embodiments, the bundled tube fuel plenum <NUM> may be at least partially defined by and/or between the forward plate <NUM>, the aft plate <NUM>, and the outer shroud <NUM>.

As shown in <FIG>, a plurality of tubes <NUM> extends axially through the forward plate <NUM>, the bundled tube fuel plenum <NUM>, and the aft plate <NUM>. Each tube <NUM> of the plurality of tubes <NUM> includes an inlet <NUM> defined at or upstream from the forward plate <NUM> and an outlet <NUM> defined at or downstream from the aft plate <NUM>. Each of the tubes <NUM> defines a respective premix passage <NUM> that extends between the respective inlet <NUM> and outlet <NUM>. At least some of the tubes <NUM> include or define at least one fuel port <NUM> in fluid communication with the bundled tube fuel plenum <NUM>. The fuel port(s) <NUM> provides for fluid communication from the bundled tube fuel plenum <NUM> into the respective premix passage <NUM> of the respective tube <NUM>.

In operation, gaseous fuel (or in some embodiments, a liquid fuel reformed into a gaseous mixture) flows, via the fuel ports <NUM>, from the bundled tube fuel plenum <NUM> into the respective premix passage <NUM> of each of the tubes <NUM>, where the fuel mixes with air entering the respective inlet <NUM> of each tube <NUM>. The fuel ports <NUM> may be positioned along the respective tubes <NUM> in a single axial plane or in more than one axial plane with respect to a centerline of the bundled tube fuel nozzle <NUM>, for example, if a multi-tau arrangement is desired to address or tune combustion dynamics between two adjacent primary combustion zones <NUM> or to mitigate coherent axial modes between the segmented annular combustion system <NUM> and the turbine <NUM>.

In particular embodiments, the bundled tube fuel plenum <NUM> may be subdivided or partitioned via a wall or other feature (not shown) into two or more bundled tube fuel plenums <NUM> defined within the housing body <NUM>. In this embodiment, a first subset of tubes of the plurality of tubes <NUM> may be fueled via a first bundled tube fuel plenum, and a second subset of tubes of the plurality of tubes <NUM> may be fueled independently via a second bundled tube fuel plenum. The bundled tube fuel nozzles <NUM> may be made as an integrated component, via casting or additive manufacturing, to reduce costs and simplify assembly.

As shown in <FIG>, the fluid conduit <NUM> may be coupled to and/or extend through the forward plate <NUM> and may provide for fluid communication into the bundled tube fuel plenum <NUM>. In particular embodiments, as shown in <FIG>, one or more of the bundled tube fuel nozzles <NUM> may include an inner tube <NUM> that extends axially within the respective fluid conduit <NUM> and through the respective aft plate <NUM>. The inner tube <NUM> may define a cartridge or air passage <NUM> through the bundled tube fuel nozzle <NUM>, which is capable of holding a liquid fuel cartridge, a sensor, an igniter, or some other component. In particular embodiments, the cartridge passage <NUM> may extend through the aft plate <NUM>.

<FIG> provides a cross-sectioned side view of the annular combustion system <NUM> mounted within the compressor discharge casing <NUM> of the combustion section <NUM>, according to various embodiments of the present disclosure. As shown in <FIG>, the inner liner <NUM>, the outer liner <NUM>, and each respective panel fuel injector <NUM> at least partially define a primary combustion chamber or zone <NUM> which is defined downstream from a respective bundled tube fuel nozzle <NUM> of the plurality of bundled tube fuel nozzles <NUM>. As shown in <FIG>, the inner liner <NUM>, the outer liner <NUM> and the plurality of panel fuel injectors <NUM> define a plurality of annularly arranged primary combustion zones <NUM> that are structurally and/or fluidly isolated with respect to each other. An axial gap <NUM> is formed between an aft end <NUM> of each panel fuel injector <NUM> and a leading edge (or forward portion) <NUM> of a stationary nozzle <NUM> disposed proximate to an inlet of the turbine (<FIG>). The secondary combustion zones <NUM> are unimpeded by the panel fuel injectors <NUM> (that is, the secondary combustion zones <NUM> are distributed within a portion of the annulus between the inner liner <NUM> and the outer liner <NUM> downstream of the aft ends <NUM> of the panel fuel injectors <NUM>).

<FIG> provides a perspective view illustrating a first side wall <NUM> of an exemplary panel fuel injector <NUM>, according to at least one embodiment of the present disclosure. <FIG> provides a perspective view of a second side wall <NUM> of the exemplary fuel injection panel <NUM> as shown in <FIG>, according to at least one embodiment of the present disclosure. As shown in <FIG> collectively, each panel fuel injector <NUM> includes a first side wall <NUM>, a second side wall <NUM>, a forward wall or upstream end portion <NUM>, an aft or downstream end <NUM>, a bottom (or radially inner) wall <NUM> and a top (or radially outer) wall <NUM>. The first side wall <NUM> and the second side wall <NUM> terminate and/or are interconnected at the aft end <NUM>.

<FIG> provides a cross-sectioned top view, taken along section line B-B as shown in <FIG>, of the exemplary panel fuel injector <NUM>, according to at least one embodiment of the present disclosure. <FIG> provides a cross-sectioned top view, taken along section line C-C as shown in <FIG>, of the panel fuel injector <NUM>, according to at least one embodiment of the present disclosure. As shown in <FIG> collectively, the first side wall <NUM> includes an outer (or hot) side surface <NUM> and an inner (or cold) side surface <NUM>. As shown in <FIG> collectively, the second side wall <NUM> includes an outer (or hot) side surface <NUM> and an inner (or cold) side surface <NUM>. The outer side surface <NUM> of the first side wall <NUM> and the outer side surface <NUM> of the second side wall <NUM> are exposed to combustion gases during operation of the combustion system <NUM>.

In various embodiments, as shown in <FIG>, <FIG> collectively, each panel fuel injector <NUM> includes a premix air plenum or pocket <NUM> (shown in hidden lines in <FIG>) and one or more fuel distribution plenums <NUM> (shown in hidden lines in <FIG>) defined within the respective panel fuel injector <NUM> between the respective first side wall <NUM> and the second side wall <NUM>. As shown in <FIG>, the fuel distribution plenum <NUM> and/or the premix air plenum <NUM> may extend radially between the respective radially inner wall <NUM> and the radially outer wall <NUM>. In particular embodiments, the fuel distribution plenum <NUM> may be in fluid communication with a fuel supply (not shown) via the fluid conduit <NUM>. In particular embodiments, as shown in <FIG>, the fuel distribution plenum <NUM> may be in fluid communication with a fuel supply (not shown) via a fluid conduit or coupling <NUM> that extends radially outwardly from the top wall <NUM> and/or the bottom wall <NUM>. Thus, the delivery of fuel <NUM> into the panel injector wall <NUM> may occur in an axial direction or a radial direction, relative to the center line of the combustor <NUM>.

In various embodiments, as shown in <FIG> collectively, the panel fuel injector <NUM> includes a plurality of premix channels that are radially stacked, that extend within the panel fuel injector <NUM> between the first side wall <NUM> and the second side wall <NUM>, and that are in fluid communication with the premix air plenum <NUM> and the fuel distribution plenum <NUM>. In particular embodiments, the plurality of premix channels includes a plurality of first side premixing channels <NUM> and a plurality of second side premixing channels <NUM> radially stacked within the panel fuel injector <NUM> between the first side wall <NUM> and the second side wall <NUM>.

In particular embodiments, as shown in <FIG>, one or more of the first side premixing channels <NUM> extends axially along the inner surface <NUM> of the second side wall <NUM> and before curving partially around the fuel distribtuion plenum <NUM> towards the first side wall <NUM> where it terminates at a corresponding first side injection aperture <NUM> defined along the first side wall <NUM>. In particular embodiments, as shown in <FIG>, one or more of the second side premixing channels <NUM> extends axially along the inner surface <NUM> of the first side wall <NUM> and then curves partially around the fuel distribution plenum <NUM> towards the second side wall <NUM> where it terminates at a corresponding second side injection aperture <NUM> defined along the second side wall <NUM>. For purposes of discussion herein, a "first side" premixing channel <NUM> is so-identified based on the side wall <NUM> on which its outlet (injection aperture <NUM>) is located. Likewise, a "second side" premixing channel <NUM> is so-identified based on having an outlet (injection aperture <NUM>) on the second side wall <NUM>.

In particular embodiments, the first side premixing channels <NUM> and/or the second side premixing channels <NUM> may traverse or wind between the first side wall <NUM> and the second side wall <NUM> of the panel fuel injector <NUM>. In one embodiment, the first side premixing channels <NUM> and/or the second side premixing channels <NUM> may traverse radially inwardly and/or outwardly between the first side wall <NUM> and the second side wall <NUM> rather than along a straight or constant axial or longitudinal plane of the panel fuel injector <NUM>. The first side premixing channels <NUM> and/or the second side premixing channels <NUM> may be oriented at different angles within the panel fuel injector <NUM>. In particular embodiments, one or more of the first side premixing channels <NUM> and/or the second side premixing channels <NUM> may be formed with varying sizes and/or geometries. In particular embodiments, one or more of the premixing channels <NUM>, <NUM> may include a mixing-enhancing feature therein, such as a bend, a kink, a twist, a helical portion, turbulators, or the like.

As shown in <FIG>, each first side premixing channel <NUM> includes an air inlet <NUM>, which is in fluid communication with the premix air plenum <NUM>. In particular embodiments, one or more of the first side premixing channels <NUM> is in fluid communication with the fuel distribution plenum <NUM> via a respective fuel port <NUM>. In various embodiments, as shown in <FIG>, the respective first side injection apertures <NUM> are radially spaced and/or stacked along the first side wall <NUM>.

As shown in <FIG>, each second side premixing channel <NUM> includes an air inlet <NUM>, which is in fluid communication with the premix air plenum <NUM>. In particular embodiments, one or more of the second side premixing channels <NUM> is in fluid communication with the fuel distribution plenum <NUM> via a respective fuel port <NUM>. In various embodiments, as shown in <FIG>, the respective second side injection apertures <NUM> are radially spaced and/or stacked along the second side wall <NUM>.

It is contemplated that the panel fuel injector <NUM> may have premixing channels (<NUM> or <NUM>) that terminate in injection apertures located along a single side wall (either the first side wall <NUM> or the second side wall <NUM>, respectively). Thus, while reference is made herein to embodiments having injection apertures <NUM>, <NUM> on both the first side wall <NUM> and the second side wall <NUM>, it should be understood that there is no requirement that both the first side wall <NUM> and the second side wall <NUM> have injection apertures <NUM>, <NUM> for delivering a fuel-air mixture unless recited in the claims. Additionally, the injection apertures <NUM>, <NUM> may be uniformly sized and spaced (as shown), or may be non-uniformly sized and/or spaced, as needs dictate.

In particular embodiments, the panel fuel injector <NUM> may be made as an integrated or unitary component, via casting, additive manufacturing (such as by 3D printing techniques), or other similar manufacturing processes. By forming the panel fuel injector <NUM> as a unitary or integrated component, the need for seals between the various features of the panel fuel injector <NUM> may be reduced or eliminated, part count and costs may be reduced, and assembly steps may be simplified or eliminated. In other embodiments, the panel fuel injector <NUM> may be fabricated, such as by welding, or may be formed from different manufacturing techniques, where components made with one technique are joined to components made by another technique. In particular embodiments, at least a portion or all of each panel fuel injector <NUM> may be formed from a ceramic matrix composite (CMC) or other composite material.

<FIG> provides a cross-sectioned top view of a portion of the annular combustion system <NUM> including one bundled tube fuel nozzle <NUM> of the plurality of bundled tube fuel nozzles <NUM> and a pair of circumferentially adjacent panel fuel injectors <NUM> of the plurality of panel fuel injectors <NUM>, according to various embodiments of the present disclosure. As shown in <FIG>, each respective primary combustion zone <NUM> is defined upstream from the corresponding first side injection apertures <NUM> and second side injection apertures <NUM> of a pair of circumferentially adjacent panel fuel injectors <NUM>. As shown in <FIG>, a secondary combustion zone <NUM> is defined downstream from the corresponding first side injection apertures <NUM> and second side injection apertures <NUM> of the pair of circumferentially adjacent panel fuel injectors <NUM>.

As shown in <FIG>, the first side injection apertures <NUM> and the second side injection apertures <NUM> of two circumferentially adjacent fuel injection panels <NUM> of the plurality of panel fuel injectors <NUM> define respective first side and second side injection plane(s) <NUM>, <NUM>, respectively, from which a second fuel and air mixture is injected into a flow of combustion gases originating from the respective primary combustion zone <NUM>. The first side injection plane <NUM> is defined at a first axial distance <NUM> from the aft plate <NUM> of the respective bundled tube fuel nozzle <NUM>. The second side injection plane <NUM> is defined at a second axial distance <NUM> from the aft plate <NUM> of the respective bundled tube fuel nozzle <NUM>.

In particular embodiments (such as the embodiment shown in <FIG>), the first axial distance <NUM> of the first side injection plane <NUM> and the second axial distance <NUM> of the second side injection plane <NUM> may be coincident (i.e., at the same axial distance from the aft plate <NUM> of the respective bundled tube fuel nozzle <NUM>). In other embodiments (such as the embodiment shown in <FIG>), the first side injection plane <NUM> and the second side injection plane <NUM> may be defined or axially staged at different axial distances from the aft plate <NUM> of the respective bundled tube fuel nozzle <NUM> (i.e., the first axial distance <NUM> is different from the second axial distance <NUM>).

Although the plurality of first side injection apertures <NUM> are shown in <FIG> in a common radial or injection plane <NUM>, in some embodiments, one or more of the first side injection apertures <NUM> may be staggered axially with respect to radially adjacent first side injection apertures <NUM>, thereby off-setting the axial distance <NUM> of one or more of the first side injection apertures <NUM>. Similarly, although the plurality of second side injection apertures are shown in <FIG> in a common radial or injection plane <NUM>, in some embodiments, one or more of the second side injection apertures <NUM> may be staggered axially with respect to radially adjacent second side injection apertures <NUM>, thereby off-setting the axial distance <NUM> of one or more of the second side injection apertures <NUM>. The amount of off-set of the first side injection apertures <NUM> may be different from the amount of off-set of the second side injection apertures <NUM>.

<FIG> provides a cross-sectioned top view of a portion of the annular combustion system <NUM> including one bundled tube fuel nozzle <NUM> of the plurality of bundled tube fuel nozzles <NUM> and a pair of circumferentially adjacent panel fuel injectors <NUM> of the plurality of panel fuel injectors <NUM>, according to various embodiments of the present disclosure. In particular embodiments, the aft end <NUM>(a) of a first panel fuel injector <NUM>(a) of the plurality of panel fuel injectors <NUM> may be positioned axially downstream, with respect to the aft plate <NUM> of a respective bundled tube fuel nozzle <NUM>, from the aft end <NUM>(b) of a second panel fuel injector <NUM>(b) of the plurality of panel fuel injectors <NUM>. In other words, an axial gap <NUM>(a) defined between the aft end <NUM>(a) of the panel fuel injector <NUM>(a) and a leading edge <NUM>(a) of a stationary nozzle <NUM>(a) may be smaller than an axial gap <NUM>(b) defined between the aft end <NUM>(b) of panel fuel injector <NUM>(b) and a leading edge <NUM>(b) of a second stationary nozzle <NUM>(b).

Referring again to <FIG>, during axially staged operation of the combustion system <NUM>, a portion of the compressed air <NUM> from the compressor <NUM> flows through the inlets <NUM> of the tubes <NUM> of the bundled tube fuel nozzles <NUM> while fuel <NUM> is supplied to the respective fuel plenums <NUM>. The fuel <NUM> is injected via fuel ports <NUM> into the flow of compressed air within the tubes <NUM>. The fuel and air mix within each tube <NUM> to provide a primary fuel-air mixture to the primary combustion zone <NUM>. The primary fuel-air mixture is burned in the primary combustion zone <NUM> to produce a hot effluent stream of combustion gases. In the case of the exemplary bundled tube fuel nozzles <NUM> illustrated herein, relatively short flames originate from the outlets <NUM> of each of the tubes <NUM> in each corresponding primary (or first) combustion zone <NUM>. The hot effluent stream flows downstream towards the first side injection plane <NUM> and the second side injection plane <NUM>.

A portion of the compressed air <NUM> is routed into the premix air plenum <NUM> of the panel fuel injectors <NUM>. The compressed air <NUM> is routed from the premix air plenum <NUM> into the respective inlet <NUM> of each of the first side premixing channels <NUM> and into the respective inlet <NUM> of each second side premixing channels <NUM>. Fuel <NUM> is supplied to the fuel distribution plenum <NUM> via fluid conduit <NUM> and/or fluid conduit <NUM>. As the compressed air <NUM> flows through the first side premixing channels <NUM> and the second side premixing channels <NUM> of the respective panel fuel injectors <NUM>, the fuel may be injected into the first side premixing channels <NUM> via respective fuel ports <NUM> and/or into each of the second side premixing channels <NUM> via fuel ports <NUM>.

The fuel and air mix within the first side premixing channels <NUM> of a first panel fuel injector <NUM> to provide a first premixed stream of fuel and air to the first side injection plane <NUM> via the first side injection apertures <NUM>. The fuel and air mix within the second side premixing channels <NUM> of a circumferentially adjacent panel fuel injector <NUM> to provide a second premixed stream of fuel and air to the second side injection plane <NUM> via the second side injection apertures <NUM>. In at least one embodiment, it may be desirable to have the secondary fuel and air introduction occur from a single side (e.g., the first side wall <NUM> or the second side wall <NUM>) of the panel fuel injector <NUM>. The first side injection apertures <NUM> and/or the second side injection apertures <NUM> may be arranged in one or more radial or axial planes.

The hot effluent stream and the first and second premixed streams of fuel and air react in the secondary combustion zone <NUM>. The hot effluent stream from the primary combustion zone <NUM>, approximately <NUM>% to <NUM>% of total combustion gas flow, accelerates until reaching the injection planes <NUM> and/or <NUM>, where the balance of fuel and air flow, via the first and second premixed streams, is added into the secondary combustion zone <NUM>. In one embodiment, approximately <NUM>% of total combustion gas flow originates from the primary combustion zone <NUM>, and the remaining approximately <NUM>% originates from the secondary combustion zone <NUM>. This arrangement enables sufficient time to achieve CO conversion to CO2 and to minimize NOx formation at the lower temperatures of the primary combustion zone and prior to the elevated gas temperatures that occur between the first and second side injection planes <NUM>, <NUM> and the stationary nozzle <NUM>, thereby minimizing overall NOx emissions.

Circumferential dynamics modes are common in traditional annular combustors. However, largely due to axially staged secondary fuel-air injection, the segmented annular combustion system <NUM> described and illustrated herein does not allow these dynamic modes to exist. Further, because each combustor segment is isolated from circumferentially adjacent segments, multi-can dynamics is mitigated or non-existent.

During operation of the segmented annular combustion system <NUM>, it may be necessary to cool one or more of the first side wall <NUM>, the second side wall <NUM>, the stationary nozzle <NUM>, the inner liner <NUM> and/or the outer liner <NUM> in order to enhance mechanical performance of the individual components. In order to accommodate cooling requirements, one or more of the first side wall <NUM>, the second side wall <NUM>, the stationary nozzle <NUM>, the inner liner <NUM> and/or the outer liner <NUM> may include various air passages or cavities, which may be in fluid communication with the high pressure plenum <NUM> formed within the compressor discharge casing <NUM> and/or with the premix air plenum <NUM> defined within each panel fuel injector <NUM>.

In particular embodiments, as shown in <FIG>, one or more of the fuel ports <NUM> may be angled, shaped or formed so as to impinge or direct a jet of fuel <NUM> from the fuel distribution plenum <NUM> onto the inner surface <NUM> of the first side wall <NUM>, thereby providing impingement cooling thereto. In particular embodiments, the compressed air <NUM> flowing from the premix air plenum <NUM> may provide convective cooling to the inner surface <NUM> of the first side wall <NUM>.

In particular embodiments, as shown in <FIG>, one or more of the fuel ports <NUM> may be angled, shaped or formed so as to impinge or direct a jet of fuel <NUM> from the fuel distribution plenum <NUM> onto the inner surface <NUM> of the second side wall <NUM>, thereby providing impingement cooling thereto.

As shown in <FIG>, a cooling air cavity or pocket <NUM> may be defined within the panel fuel injector <NUM> between the first side wall <NUM> and the second side wall <NUM>. One or more ports <NUM> may be angled, shaped or formed so as to impinge or direct a jet of compressed air <NUM> from the cooling air cavity <NUM> onto the inner surface <NUM> of the premixing channel <NUM>. In the exemplary embodiment shown, the inner surface <NUM> of the premixing channel <NUM> is coincident with the first side wall <NUM>, thereby providing impingement cooling thereto.

In particular embodiments, the compressed air <NUM> flowing from the premix air plenum <NUM> may provide convective cooling to the inner surface <NUM> of the second side wall <NUM>. One or more ports <NUM> may be angled, shaped or formed so as to impinge or direct a jet of compressed air <NUM> from the cooling air cavity <NUM> onto the inner surface <NUM> of the premixing channel <NUM>. In the exemplary embodiment shown, the inner surface <NUM> of the premixing channel <NUM> is coincident with the second side wall <NUM>, thereby providing impingement cooling thereto.

<FIG> also illustrates that the fuel distribution plenum <NUM> is flanked on an upstream side by the cooling air cavity <NUM> and on the downstream side by a continuation of the cooling air cavity <NUM>. Downstream of the fuel port <NUM>, <NUM>, the premixing channels <NUM>, <NUM> include a curved end section that directs the fuel/air mixture to the respective injection aperture <NUM>, <NUM>. The curved end section includes an inner radius and an outer radius. Ports <NUM> may be provided in the inner radius of the curved portion, the ports <NUM> being in fluid communication with the downstream portion of the cooling air cavity <NUM>, to direct a film of air along an interior surface of the curved portion of the premixing channel <NUM>, <NUM>, thereby preventing the flow from stagnating along the wall of the premixing channel <NUM>, <NUM>.

<FIG> is a simplified perspective view of an exemplary combustor segment <NUM>, according to at least one embodiment of the present disclosure. <FIG> is an enlarged cross-sectioned top view of an exemplary panel fuel injector <NUM> and includes a portion of an exemplary stationary nozzle <NUM>, according to one or more embodiments of the present disclosure. In particular embodiments, as shown in <FIG> and <FIG> collectively, the aft end <NUM> of at least one panel fuel injector <NUM> is disposed proximate, adjacent, immediately adjacent or next to a respective leading edge <NUM> of a respective stationary nozzle <NUM>. As such, the respective axial gap <NUM> defined between the aft end <NUM> of the panel fuel injector <NUM> and the leading edge <NUM> of the respective stationary nozzle <NUM> is minimalized, thereby at least partially shielding the respective leading edge <NUM> from the flow of combustion gases <NUM>. For example, the axial gap <NUM> between the aft end <NUM> and the leading edge of a respective stationary nozzle <NUM> may be less than six inches (<NUM>,<NUM>), less than three inches (<NUM>,<NUM>), less than two inches (<NUM>,<NUM>), or less than one inch (<NUM>,<NUM>). Further, in these embodiments, the secondary combustion zones <NUM> are separated from one another, and the number of secondary combustion zones <NUM> is equal to the number of primary combustion zones <NUM>.

In particular embodiments, as shown in <FIG>, the aft end at least one of the first side wall <NUM> and the second side wall <NUM> may extend axially past the leading edge <NUM> towards the trailing edge and/or partially across a pressure side wall <NUM> or a suction side wall <NUM> of the stationary nozzle <NUM>, thereby at least partially shielding a portion of the pressure side wall <NUM> and/or the suction side wall <NUM> from the flow of combustion gases <NUM>.

In particular embodiments, as shown in <FIG>, at least one panel fuel injector <NUM> includes a cooling air plenum <NUM> defined between the first side wall <NUM> and the second side wall <NUM> proximate to the aft end <NUM>. An aft wall <NUM> or the aft end <NUM> of the panel fuel injector <NUM> may be arcuate or concave or otherwise complementary in shape to the leading edge <NUM> of a respective stationary nozzle <NUM>. For example, the aft end <NUM> of the panel fuel injector <NUM> may define a pocket or slot, and the leading edge <NUM> of the stationary nozzle <NUM> may extend into the pocket. One or more cooling holes <NUM> may be defined along the aft wall <NUM>. The cooling holes <NUM> are in fluid communication with the cooling air plenum <NUM>. During operation, compressed air <NUM> may flow from the cooling air plenum <NUM>, though the cooling holes <NUM> and into the axial gap <NUM>, thereby providing at least one of impingement and film cooling to the corresponding stationary nozzle <NUM>, particularly to the leading edge <NUM> of the corresponding stationary nozzle <NUM>.

Alternately, as shown in <FIG>, the combustor <NUM> may include a first set of panel fuel injectors 200a that define a first axial gap 50a between a respective aft end <NUM> and a corresponding stationary nozzle <NUM> ("short" panel fuel injectors, as in <FIG>) and a second set of panel fuel injectors 200b that define a second axial gap 50b between a respective aft end <NUM> and a corresponding stationary nozzle <NUM> ("long" panel fuel injectors, as in <FIG>). The number of panel fuel injectors 200b in the second set may be smaller than the number of panel fuel injectors 200a in the first set. In some embodiments, the panel fuel injectors 200b in the second set are spaced circumferentially apart from one another (i.e., are not adjacent). In this exemplary configuration, which may be useful for mitigating dynamics, the number of secondary combustion zones <NUM> is smaller than the number of primary combustion zones <NUM>. That is, the secondary combustion zones <NUM> are formed axially downstream of the aft ends <NUM> of the panel fuel injectors 200a in the first set and extend circumferentially between the panel fuel injectors 200b of the second set.

<FIG> provides a top cross-sectioned perspective view of a portion of an exemplary panel fuel injector <NUM>, according to at least one embodiment of the present disclosure. In particular embodiments, as shown in <FIG>, the first side wall <NUM> may define a plurality of first side micro-cooling channels <NUM> that extend between and/or is defined between the inner surface <NUM> and the outer surface <NUM> of the first side wall <NUM>. Each first side micro-cooling channel <NUM> includes a respective inlet <NUM> and a respective outlet <NUM>. The respective inlet <NUM> to one or more of the first side micro-cooling channels <NUM> may be in fluid communication with the cooling air plenum <NUM>, the cooling air cavity <NUM>, the premix air plenum <NUM> or other compressed air or cooling fluid source. The respective outlet <NUM> of one or more of the first side micro-cooling channels <NUM> may be defined along the aft wall <NUM> of the panel fuel injector <NUM>. Although the first side micro-cooling channels <NUM> are shown as extending substantially axially or linearly through the first side wall <NUM>, it should be noted that one or more of the first side micro-cooling channels <NUM> may extend between the inner surface <NUM> and the outer surface <NUM> in a serpentine or curved pattern.

In particular embodiments, as shown in <FIG>, the second side wall <NUM> may define a plurality of second side micro-cooling channels <NUM> that extend between the inner surface <NUM> and the outer surface <NUM> of the second side wall <NUM>. Each second side micro-cooling channel <NUM> includes a respective inlet <NUM> and a respective outlet <NUM>. The respective inlet <NUM> to one or more of the second side micro-cooling channels <NUM> may be in fluid communication with the cooling air plenum <NUM>, the cooling air cavity <NUM>, the premix air plenum <NUM> (<FIG>) or other compressed air or cooling fluid source. The respective outlet <NUM> of one or more of the second side micro-cooling channels <NUM> may be defined along the aft wall <NUM> of the panel fuel injector <NUM>. Although the second side micro-cooling channels <NUM> are shown as extending substantially axially or linearly through the second side wall <NUM>, it should be noted that one or more of the second side micro-cooling channels <NUM> may extend between the inner surface <NUM> and the outer surface <NUM> in a serpentine or curved pattern.

In particular embodiments, as shown in <FIG>, a wall thickness T of either or both of the first side wall <NUM> and the second side wall <NUM> of the panel fuel injector <NUM> may vary along the axial or longitudinal length and/or along a radial span of the panel fuel injector <NUM>. For example, the wall thickness of either or both of the first side wall <NUM> and the second side wall <NUM> of the panel fuel injector <NUM> may vary between the upstream end portion <NUM> and the aft end <NUM> and/or between the radially inner wall <NUM> and the radially outer wall <NUM> (<FIG>).

In particular embodiments, as illustrated in <FIG>, an overall injection panel thickness PT may vary along the axial or longitudinal length and/or along a radial span of the panel fuel injector <NUM>. For example, the first side wall <NUM> and/or the second side wall <NUM> may bulge outwardly towards and/or into the flow of combustion gases flowing between two circumferentially adjacent panel fuel injectors <NUM>. The bulge or variation in overall injection panel thickness PT may occur at any point along the radial span and/or the axial length of the respective first side wall <NUM> or the second side wall <NUM>. Panel thickness PT or the position of the bulged region may vary along the axial length and/or the radial span of first side wall <NUM> or the second side wall <NUM> the passage to tailor the local hot passage areas to achieve a certain target velocity and residence time profile without requiring a change in wall thickness T.

<FIG> provides a perspective view of an exemplary panel fuel injector <NUM>, bundled tube fuel nozzle <NUM>, a portion of the inner liner <NUM> and a portion of the outer liner <NUM>, according to at least one embodiment of the present disclosure. <FIG> provides an enlarged cross-sectioned view of a portion of the panel fuel injector <NUM> as shown in <FIG>, according to at least one embodiment. In particular embodiments, as shown in <FIG> collectively, at least one of the panel fuel injectors <NUM> may define at least one cross-fire opening <NUM> that extends through the first side wall <NUM> and the second side wall <NUM> of the respective panel fuel injector <NUM>. The cross-fire opening <NUM> permits cross-fire and ignition of circumferentially adjacent primary combustion zones <NUM>.

In one embodiment, the cross-fire opening <NUM> is defined by a double-walled cylindrical structure with an air volume therebetween. The combustion gases <NUM>, ignited in a first combustion zone <NUM>, are permitted to flow through the inner wall of the cross-fire opening <NUM> into an adjacent primary combustion zone <NUM>, where ignition of the fuel and air mixture in the adjacent primary combustion zone <NUM> occurs. To prevent combustion gases <NUM> from stagnating in the cross-fire opening <NUM>, purge air holes <NUM> are provided in the inner wall. In addition to purge air holes <NUM>, the outer walls of the cross-fire openings <NUM> may be provided with air feed holes <NUM> that may be in fluid communication with at least one of the premix air plenum <NUM>, the cooling air cavity <NUM>, or another compressed air source. The purge air holes <NUM> are in fluid communication with the air volume, which receives air via the air feed holes <NUM>. The combination of smaller air feed holes <NUM> in the outer wall and larger purge air holes <NUM> in the inner wall transforms the cross-fire opening <NUM> into a resonator for mitigating potential combustion dynamics within the segmented annular combustion system <NUM>.

<FIG> provides a perspective view of a portion of an exemplary panel fuel injector <NUM>, according to at least one embodiment. In particular embodiments, as shown in <FIG>, at least one impingement air insert <NUM>, <NUM> may be disposed within a respective air cavity such as the cooling air cavity <NUM> and/or the cooling air plenum <NUM> defined within a respective panel fuel injector <NUM> of the plurality of panel fuel injectors <NUM>. The impingement air inserts <NUM>, <NUM> include walls that are complementary in shape to the cooling air cavity <NUM> and cooling air plenum <NUM>, respectively. The impingement air inserts <NUM>, <NUM> include at least one open end through which air may flow. At least one of the impingement air insert(s) <NUM>, <NUM> may include or define a plurality of cooling or impingement holes <NUM>, <NUM> oriented and/or formed to direct multiple discrete jets of air onto one or more inner surfaces <NUM>, <NUM> (<FIG>) of the respective panel fuel injector <NUM> at discrete locations to provide jetted or impingement cooling thereto.

<FIG> provides a perspective view of a portion of an exemplary combustor segment <NUM>, according to at least one embodiment of the present disclosure. In particular embodiments, as shown in <FIG>, the inner liner <NUM> and the outer liner <NUM> are double-banded structures, each defining a respective flow annulus between an inner band and an outer band. In these embodiments, the inner liner <NUM> and the outer liner <NUM> are cooled by impingement and/or film cooling.

Specifically, in these embodiments, the inner liner <NUM> includes an inner band <NUM> that is radially spaced from an outer band <NUM>. In at least one embodiment, a wall <NUM> extends radially between the inner band <NUM> and the outer band <NUM>. The inner band <NUM>, the outer band <NUM>, and the wall <NUM> (when present) define an inner flow annulus <NUM> therebetween.

In particular embodiments, an inlet <NUM> to the inner flow annulus <NUM> is defined at a downstream end of the inner liner <NUM>. In particular embodiments, the inner flow annulus <NUM> is in fluid communication with the compressor <NUM> via the high pressure plenum <NUM> and the inlet <NUM>. In particular embodiments, the outer band <NUM> may define a plurality of apertures <NUM>. In operation, the apertures <NUM> provide for fluid communication between the high pressure plenum <NUM> and the inner flow annulus <NUM>. In particular embodiments, one or more apertures <NUM> of the plurality of apertures <NUM> is oriented to direct jets of cooling air against a cool side surface <NUM> of the inner band <NUM> of the inner liner <NUM>.

In particular embodiments, the inner band <NUM> defines a primary aperture <NUM>. In operation, the primary aperture <NUM> provides for fluid communication between the inner flow annulus <NUM> and a respective panel fuel injector <NUM>. For example, in particular embodiments, the primary aperture <NUM> may provide for compressed air flow between the inner flow annulus <NUM> and one or more of the premix air plenum <NUM>, the cooling air cavity <NUM> and the cooling air plenum <NUM>. In particular embodiments, the inner band <NUM> may define a plurality of secondary apertures <NUM>. During operation, compressed air <NUM> from the inner flow annulus <NUM> may flow through the secondary apertures <NUM>, thereby providing a cooling film of the compressed air <NUM> across an outer or hot side surface <NUM> of the inner band <NUM>.

In particular embodiments, as shown in <FIG>, the outer liner <NUM> includes an inner band <NUM> that is radially spaced from an outer band <NUM>. In at least one embodiment, a wall <NUM> extends radially between the inner band <NUM> and the outer band <NUM>. The inner band <NUM>, the outer band <NUM>, and the wall <NUM> (when present) define an outer flow annulus <NUM> therebetween. In particular embodiments, an inlet <NUM> to the outer flow annulus <NUM> is defined at a downstream end of the outer liner <NUM>. In particular embodiments, the outer flow annulus <NUM> is in fluid communication with the compressor <NUM> via the high pressure plenum <NUM> and the inlet <NUM>. In particular embodiments, the outer band <NUM> may define a plurality of apertures <NUM>. In operation, the apertures <NUM> provide for fluid communication between the high pressure plenum <NUM> and the outer flow annulus <NUM>. In particular embodiments, one or more apertures <NUM> of the plurality of apertures <NUM> is oriented to direct jets of cooling air against a cool side surface of the inner band <NUM> of the outer liner <NUM>.

In particular embodiments, the inner band <NUM> defines a primary aperture <NUM>. In operation, the primary aperture <NUM> provides for fluid communication between the outer flow annulus <NUM> and a respective panel fuel injector <NUM>. For example, in particular embodiments, the primary aperture <NUM> may provide for compressed air flow between the outer flow annulus <NUM> and one or more of the premix air plenum <NUM>, the cooling air cavity <NUM>, and the cooling air plenum <NUM>. In particular embodiments, the inner band <NUM> may define a plurality of secondary apertures <NUM>. During operation, compressed air <NUM> from the outer flow annulus <NUM> may flow through the secondary apertures <NUM>, thereby providing a cooling film of the compressed air <NUM> across an inner or hot side surface <NUM> of the inner band <NUM>.

<FIG> are intended to be illustrative of a portion of either or both the inner band <NUM> of the inner liner <NUM> or the inner band <NUM> of the outer liner <NUM>, according to particular embodiments of the present disclosure. In these embodiments, the inner liner <NUM> and the outer liner <NUM> are single-wall structures through which micro-channel cooling passages are disposed, as described below. Thus, the cooling of the inner liner <NUM> and the outer liner <NUM> is accomplished via convective cooling, rather than impingement and/or film cooling as described with reference to <FIG>.

In particular embodiments, as shown in <FIG>, the outer or cool side surface of the inner liner <NUM> and/or the outer or cool side surface <NUM> of the outer liner <NUM> may define or include a plurality of inlet holes <NUM>, <NUM> for receiving compressed air <NUM> from the high-pressure plenum <NUM> (<FIG>). Each inlet hole <NUM>, <NUM> may be integrated with a micro-channel cooling passage <NUM>, <NUM> that terminates at a corresponding outlet hole or exhaust port <NUM>, <NUM>. The length of the micro-channel cooling passages <NUM>, <NUM> may vary in different areas of the liner <NUM>, <NUM>.

In particular embodiments, the length of some or all of the micro-channel cooling passages <NUM>, <NUM> may be less than about ten inches (<NUM>,<NUM>). In particular embodiments, the length of some or all of the micro-channel cooling passages <NUM>, <NUM> may be less than about five inches (<NUM>,<NUM>). In particular embodiments, the length of some or all of the micro-channel cooling passages <NUM>, <NUM> may be less than about two inches (<NUM>,<NUM>). In particular embodiments, the length of some or all of the micro-channel cooling passages <NUM>, <NUM> may be less than about one inch (<NUM>,<NUM>). In particular embodiments, one or more of the micro-channel cooling passages <NUM>, <NUM> may be between <NUM> inches (<NUM>,<NUM>) and <NUM> inches (<NUM>,<NUM>). The length of the various micro-channel cooling passages <NUM>, <NUM> may be determined by the heat pick-up capability of the air flowing therethrough (i.e., the temperature of the cooling air), the diameter of the micro-channel passage, and the temperature of the liner <NUM>, <NUM> in the area to be cooled.

In particular embodiments, one or more of the outlet holes <NUM>, <NUM> may be located along the respective outer surface <NUM>, <NUM> and may deposit the compressed air <NUM> from the respective inlet holes <NUM>, <NUM> into a respective flow passage or collection channel <NUM>, <NUM>. In at least one embodiment, as shown in <FIG>, the collection channel <NUM>, <NUM> may be defined by a duct <NUM>, <NUM> that extends along the respective outer surface <NUM>, <NUM>. The respective collection channel <NUM>, <NUM> may convey at least a portion of the compressed air <NUM> to the premix air plenum <NUM> (<FIG>) of the panel fuel injector <NUM> where it may be distributed to the various first side premixing channels <NUM> and/or the second side premixing channels <NUM>. More details about micro-channel cooling using this approach are described in commonly assigned U. Patent Application No. <NUM>/<NUM>,<NUM>, filed November <NUM>, <NUM>.

In particular embodiments, one or more of the micro-channel cooling passages <NUM>, <NUM> may be oriented so as to provide for compressed air flow between one or more of the premix air plenum <NUM>, the cooling air cavity <NUM> and the cooling air plenum <NUM>. Thus, the compressed air <NUM> from one or more of the micro-channel cooling passages <NUM>, <NUM> may be mixed with the compressed air <NUM> that is used to cool the interior of the panel fuel injector <NUM>.

In particular embodiments, it is possible to use micro-channel cooling and impingement cooling. For example, the outlet holes <NUM>, <NUM> of one or more of the micro-channel cooling passages <NUM>, <NUM> may be located along a side wall <NUM>, <NUM> (<FIG>) of the inner band <NUM> or the inner band <NUM>, such that the compressed air <NUM> flows through the micro-channel cooling passages <NUM>, <NUM> and then between two circumferentially adjacent inner liners <NUM> or adjacent outer liners <NUM> along a split line defined between the two adjacent inner or outer liners <NUM>, <NUM>, thereby creating a fluid seal therebetween. In one embodiment, the outlet holes <NUM>, <NUM> of one or more of the micro-channel cooling passages <NUM>, <NUM> may be located along the respective hot side surface <NUM> of the inner band <NUM> or the hot side surface <NUM> of the outer band <NUM>, such that the compressed air <NUM> flows through the micro-channel cooling passages <NUM>, <NUM> and then enters either the primary or the secondary combustion chambers or zones <NUM>, <NUM> as cooling film air.

The various embodiments of the segmented annular combustion system <NUM>, particularly the bundled tube fuel nozzles <NUM> in combination with the panel fuel injectors <NUM>, the inner liner <NUM>, and outer liner <NUM> described and illustrated herein provide various enhancements or improvements to the operations and turndown capability over conventional annular combustion systems. For example, during start-up of the segmented annular combustion system <NUM>, the igniters may ignite the fuel and air mixture flowing from the outlets <NUM> of the tubes <NUM> of the plurality of tubes <NUM>. As power needs increase, fuel to the panel fuel injectors <NUM> may be turned on simultaneously or sequentially until each panel fuel injector <NUM> is operational.

To reduce power output, the fuel flowing to the tubes <NUM> of the bundled tube fuel nozzles <NUM> and/or to the panel fuel injectors <NUM> may be throttled down simultaneously or sequentially as desired. When it becomes desirable or necessary to turn off the panel fuel injectors <NUM>, the fuel may be shut off to each panel fuel injector <NUM> or to individual panel fuel injectors <NUM> or groups of the panel fuel injectors <NUM>, thereby minimizing any disturbance to the turbine operation.

Claim 1:
An annular combustion system (<NUM>) comprising:
an inner liner (<NUM>) and an outer liner (<NUM>) disposed radially outward of the inner liner (<NUM>), the inner liner (<NUM>) and the outer liner (<NUM>) defining therebetween an annulus circumscribing a centerline of the annular combustion system (<NUM>), the annulus including a plurality of primary combustion zones (<NUM>) at an upstream end thereof and a plurality of secondary combustion zones (<NUM>) downstream of the primary combustion zones (<NUM>);
a plurality of fuel nozzles (<NUM>), at least one fuel nozzle (<NUM>) discharging a combustible mixture into each primary combustion zone (<NUM>) of the plurality of primary combustion zones (<NUM>);
a plurality of panel fuel injectors (<NUM>), each panel fuel injector (<NUM>) being disposed between adjacent fuel nozzles (<NUM>) and extending in an axially downstream direction to separate adjacent primary combustion zones (<NUM>), each panel fuel injector (<NUM>) discharging a combustible mixture into at least one secondary combustion zone (<NUM>); wherein
each panel fuel injector (<NUM>) of the plurality of panel fuel injectors (<NUM>) comprises:
a first side wall (<NUM>);
a second side wall (<NUM>) opposite the first side wall (<NUM>); and
an aft end (<NUM>) connecting the first side wall (<NUM>) and the second side wall (<NUM>);
wherein the first side wall (<NUM>), the second side wall (<NUM>), and the aft end (<NUM>) define therebetween a premix air plenum (<NUM>) and a fuel distribution plenum (<NUM>); and
wherein a plurality of premixing channels (<NUM>, <NUM>) are disposed between the first side wall (<NUM>) and the second side wall (<NUM>), each premixing channel of the plurality of premixing channels (<NUM>, <NUM>) being in fluid communication with the premix air plenum (<NUM>) and the fuel distribution plenum (<NUM>) and having an injection aperture (<NUM>, <NUM>) formed in one of the first side wall (<NUM>) and the second side wall (<NUM>).