Patent Description:
Turbomachines are utilized in a variety of industries and applications for energy transfer purposes. For example, a gas turbine engine generally includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section progressively increases the pressure of a working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and a fuel (e.g., typically natural gas) mix within the combustion section and burn in a combustion chamber to generate high pressure and high temperature combustion gases. The combustion gases flow from the combustion section into the turbine section where they expand to produce work. For example, expansion of the combustion gases in the turbine section may rotate a rotor shaft connected, e.g., to a generator to produce electricity. The combustion gases then exit the gas turbine via the exhaust section.

Traditional gas turbine engines include one or more combustors that burn a mixture of natural gas and air within the combustion chamber to generate the high pressure and temperature combustion gases. As a byproduct, oxides of nitrogen (NOx) and other pollutants are created and expelled by the exhaust section. Regulatory requirements for low emissions from gas turbines are continually growing more stringent, and environmental agencies throughout the world are now requiring even lower rates of emissions of NOx and other pollutants from both new and existing gas turbines.

Burning a mixture of natural gas and high amounts of hydrogen and/or burning pure hydrogen instead of natural gas within the combustor would significantly reduce or eliminate the emission of NOx and other pollutants. However, because hydrogen burning characteristics are different than those of natural gas, traditional combustion systems and methods are not capable of burning high levels of hydrogen and/or pure hydrogen without issue. For example, burning high levels of hydrogen and/or pure hydrogen within a traditional combustion system could promote flashback or flame holding conditions in which the combustion flame migrates towards the fuel being supplied by the nozzles, possibly causing severe damage to the nozzles in a relatively short amount of time.

As such, an improved method for burning high levels of hydrogen and/or pure hydrogen within a gas turbine combustor is desired and would be appreciated in the art. <CIT> discloses a combustor comprising a premix fuel nozzle at an upstream end of the combustor and two sets of diffusion type burners comprising fuel nozzles downstream of the premix fuel nozzle. The premix fuel nozzle taught to be operated on a fuel containing <NUM> vol % or less hydrogen premixed with air. A first plurality of the diffusion type nozzles are taught to be operated on a fuel containing <NUM> vol % or less hydrogen while a second plurality of the diffusion type nozzles are taught to be operated on a fuel containing <NUM> vol % or more hydrogen.

Aspects and advantages of the methods in accordance with the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology. The herein claimed invention is defined by the appended claims.

In accordance with one embodiment, a method of operating a combustor of a turbomachine on a total fuel input that contains a concentration of hydrogen that is greater than about <NUM>% to generate outlet combustion gases having an outlet temperature is provided. The combustor includes a combustion chamber that has a primary combustion zone and a secondary combustion zone. The method includes injecting, with at least one fuel nozzle, a first mixture of air and a first fuel containing hydrogen into the primary combustion zone of the combustor to generate a first flow of combustion gases having a first temperature. The method further includes injecting, with one or more premix injectors disposed downstream of the fuel nozzles, a second mixture of air and a second fuel containing hydrogen into the secondary combustion zone of the combustor as a cross-flow to generate a second flow of combustion gases having a second temperature. The method further includes separately injecting a third fuel into secondary combustion zone. The third fuel ignites and mixes with the first flow and the second flow of combustion gases to generate outlet combustion gases having a third temperature.

In accordance with another embodiment, a method of operating a combustor is provided. The method includes injecting, with at least one fuel nozzle, a first mixture of air and a first fuel into a primary combustion zone of the combustor to generate a first flow of combustion gases having a first temperature. The method further includes injecting, with one or more premix injectors disposed downstream of the fuel nozzles, a second mixture of air and a second fuel into a secondary combustion zone of the combustor as a cross-flow to generate a second flow of combustion gases having a second temperature. The method further includes separately injecting a third fuel into the secondary combustion zone. The third fuel ignites and mixes with the first flow and the second flow of combustion gases to generate outlet combustion gases having a third temperature.

In accordance with yet another embodiment, a method of operating a combustor of a turbomachine on a total fuel input that contains a <NUM>% concentration of hydrogen to generate outlet combustion gases having an outlet temperature is provided. The combustor includes a combustion chamber that has a primary combustion zone and a secondary combustion zone. The method includes injecting, with at least one fuel nozzle, a first mixture of air and hydrogen into the primary combustion zone of the combustor to generate a first flow of combustion gases having a first temperature. The method further includes injecting, with one or more premix injectors disposed downstream of the fuel nozzles, a second mixture of air and hydrogen into the secondary combustion zone of the combustor to generate a second flow of combustion gases having a second temperature. The method further includes separately injecting a flow of pure hydrogen into the combustion chamber of the combustor to generate a third flow of combustion gases having a third temperature.

These and other features, aspects, and advantages of the present methods will become better understood with reference to the following description and appended claims.

A full and enabling disclosure of the present methods, including the best mode of making and using the present systems and methods, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:.

Reference now will be made in detail to embodiments of the present methods, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, rather than limitation of, the technology. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology within the scope of the claimed subject matter. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Like or similar designations in the drawings and description have been used to refer to like or similar parts of the subject technology.

The term "fluid" may refer to a gas or a liquid. The term "fluid communication" means that a fluid is capable of flowing or being conveyed between the areas specified.

As used herein, the terms "upstream" (or "forward") and "downstream" (or "aft") refer to the relative direction with respect to fluid flow in a fluid pathway. 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.

Terms of approximation, such as "about," "approximately," "generally," and "substantially," are not to be limited to the precise value specified. For example, the approximating language may refer to being within a <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> percent margin in either individual values, range(s) of values and/or endpoints defining range(s) of values. When used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction. For example, "generally vertical" includes directions within ten degrees of vertical in any direction, e.g., clockwise or counter-clockwise.

The terms "directly coupled," "directly fixed," "directly attached to," and the like indicated that a first component is joined to a second component with no intervening structures. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive- or and not to an exclusive- or.

Here and throughout the specification and claims, range limitations are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

As used herein, the term "pure hydrogen" may refer to a gas containing almost entirely (or entirely) hydrogen not mixed with air or other oxidants, such as greater than <NUM>% hydrogen with some natural contaminants or <NUM>% hydrogen containing little to no contaminants. Also, as used herein, "pure fuel" may refer to a mixture of fuels in the absence of air or other oxidants, such as hydrogen and natural gas (e.g., <NUM>% hydrogen and <NUM>% natural gas, or such as <NUM>% hydrogen and <NUM>% natural gas, or such as <NUM>% hydrogen and <NUM>% natural gas, or such as <NUM>% hydrogen and <NUM>% natural gas). The natural gas may be ethane, propane, methane, or others. Additionally, as used herein, the term "hydrogen" may refer to diatomic hydrogen (H<NUM>), such as hydrogen gas not containing any carbon.

Referring now to the drawings, <FIG> illustrates a schematic diagram of one embodiment of a turbomachine, which in the illustrated embodiment is a gas turbine <NUM>. Although an industrial or land-based gas turbine is shown and described herein, the present disclosure is not limited to a land-based and/or industrial gas turbine unless otherwise specified in the claims. For example, the technology as described herein may be used in any type of turbomachine including but not limited to a steam turbine, an aircraft gas turbine, or a marine gas turbine.

As shown, gas turbine <NUM> generally includes an inlet section <NUM>, a compressor section <NUM> disposed downstream of the inlet section <NUM>, a plurality of combustors <NUM> (shown in <FIG>) within a combustion section <NUM> disposed downstream of the compressor section <NUM>, a turbine section <NUM> disposed downstream of the combustion section <NUM>, and an exhaust section <NUM> disposed downstream of the turbine section <NUM>. Additionally, the gas turbine <NUM> may include one or more shafts <NUM> coupled between the compressor section <NUM> and the turbine section <NUM>.

The compressor section <NUM> may generally include a plurality of rotor disks <NUM> (one of which is shown) and a plurality of rotor blades <NUM> extending radially outwardly from and connected to each rotor disk <NUM>. Each rotor disk <NUM> in turn may be coupled to or form a portion of the shaft <NUM> that extends through the compressor section <NUM>. The compressor section <NUM> further includes a plurality of stationary vanes (not shown), which are arranged in stages with the rotor blades <NUM> and which direct the flow against the rotor blades <NUM>.

The turbine section <NUM> may generally include a plurality of rotor disks <NUM> (one of which is shown) and a plurality of rotor blades <NUM> extending radially outwardly from and being interconnected to each rotor disk <NUM>. Each rotor disk <NUM> in turn may be coupled to or form a portion of the shaft <NUM> that extends through the turbine section <NUM>. The turbine section <NUM> further includes an outer casing <NUM> that circumferentially surrounds the portion of the shaft <NUM> and the rotor blades <NUM>, thereby at least partially defining a hot gas path <NUM> through the turbine section <NUM>. The turbine section <NUM> further includes a plurality of stationary vanes (not shown), which are arranged in stages with the rotor blades <NUM> and which direct the flow against the rotor blades <NUM>.

During operation, a working fluid such as air flows through the inlet section <NUM> and into the compressor section <NUM> where the air is progressively compressed by multiple compressor stages of rotating blades and stationary vanes, thus providing pressurized air to the combustors <NUM> of the combustion section <NUM>. The pressurized air is mixed with fuel and burned within each combustor <NUM> to produce combustion gases <NUM>. The combustion gases <NUM> flow through the hot gas path <NUM> from the combustion section <NUM> into the turbine section <NUM>, in which energy (kinetic and/or thermal) is transferred from the combustion gases <NUM> to the rotor blades <NUM>, causing the shaft <NUM> to rotate. The mechanical rotational energy may then be used to power the compressor section <NUM> and/or to generate electricity. The combustion gases <NUM> exiting the turbine section <NUM> may then be exhausted from the gas turbine <NUM> via the exhaust section <NUM>.

<FIG> is a schematic representation of a combustor <NUM>, as may be included in a can annular combustion system for the heavy-duty gas turbine <NUM>. In a can annular combustion system, a plurality of combustors <NUM> (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more) are positioned in an annular array about the shaft <NUM> that connects the compressor section <NUM> to the turbine section <NUM>.

As shown in <FIG>, the combustor <NUM> may define an axial direction A that extends along an axial centerline <NUM>. The combustor may also define a circumferential direction C which extends around the axial direction A and the axial centerline <NUM>. The combustor <NUM> may further define a radial direction R perpendicular to the axial direction A and the axial centerline <NUM>.

<FIG> illustrates a combustor <NUM> having one or more exemplary fuel injection assemblies <NUM> (also referred to as an axial fuel staging (AFS) system), as discussed further herein. The combustor <NUM> includes a combustion liner <NUM> that defines a combustion chamber <NUM>. The combustion liner <NUM> may be positioned within (i.e., circumferentially surrounded by) an outer sleeve <NUM>, such that an annulus <NUM> is formed therebetween. At least one fuel nozzle <NUM> may be positioned at the forward end of the combustor <NUM>. Fuel may be directed through first fuel supply conduits <NUM>, which extend through an end cover <NUM>, and into the fuel nozzles <NUM>. The fuel nozzles <NUM> convey the fuel and compressed air <NUM> into a primary combustion zone <NUM>, where combustion occurs. In some embodiments, the fuel and compressed air <NUM> are combined as a mixture prior to reaching the primary combustion zone <NUM>.

The combustion liner <NUM> may contain and convey combustion gases to the turbine section <NUM>. The combustion liner <NUM> defines the combustion chamber <NUM> within which combustion occurs. As shown in <FIG>, the combustion liner <NUM> may extend between the fuel nozzles <NUM> and an aft frame <NUM>. The combustion liner <NUM> may have a cylindrical liner portion and a tapered transition portion that is separate from the cylindrical liner portion, as in many conventional combustion systems. Alternately, the combustion liner <NUM> may have a unified body (or "unibody") construction, in which the cylindrical portion and the tapered portion are integrated with one another. Thus, any discussion of the combustion liner <NUM> herein is intended to encompass both conventional combustion systems having a separate liner and transition piece and those combustion systems having a unibody liner. Moreover, the present disclosure is equally applicable to those combustion systems in which the transition piece and the stage one nozzle of the turbine section <NUM> are integrated into a single unit, sometimes referred to as a "transition nozzle" or an "integrated exit piece.

The combustion liner <NUM> may be surrounded by an outer sleeve <NUM>, which is spaced radially outward of the combustion liner <NUM> to define an annulus <NUM> through which compressed air <NUM> flows to a head end of the combustor <NUM>. Heat is transferred convectively from the combustion liner <NUM> to the compressed air <NUM>, thus cooling the combustion liner <NUM> and warming the compressed air <NUM>.

In exemplary embodiments, the outer sleeve <NUM> may include a flow sleeve <NUM> at the forward end and an impingement sleeve <NUM> at the aft end. The flow sleeve <NUM> and the impingement sleeve <NUM> may be coupled to one another. Alternately, the outer sleeve <NUM> may have a unified body (or "unisleeve") construction, in which the flow sleeve <NUM> and the impingement sleeve <NUM> are integrated with one another in the axial direction. As before, any discussion of the outer sleeve <NUM> herein is intended to encompass both conventional combustion systems having a separate flow sleeve <NUM> and impingement sleeve <NUM> and combustion systems having a unisleeve outer sleeve.

The forward casing <NUM> and the end cover <NUM> of the combustor <NUM> define the head end air plenum <NUM>, which includes one or more fuel nozzles <NUM>. The fuel nozzles <NUM> may be any type of fuel nozzle, such as bundled tube fuel nozzles <NUM> (<FIG>, often referred to as "micromixers") or swirler nozzles (often referred to as "swozzles"). For example, the fuel nozzles <NUM> are positioned within the head end air plenum <NUM> defined at least partially by the forward casing <NUM>. In many embodiments, the fuel nozzles <NUM> may extend from the end cover <NUM>. For example, each fuel nozzle <NUM> may be coupled to an aft surface of the end cover <NUM> via a flange (not shown). As shown in <FIG>, the at least one fuel nozzle <NUM> may be partially surrounded by the combustion liner <NUM>. The aft, or downstream ends, of the fuel nozzles <NUM> extend through a cap plate <NUM> that defines the upstream end of the combustion chamber <NUM>.

The fuel nozzles <NUM> may be in fluid communication with a first fuel supply <NUM> configured to supply a first fuel <NUM> to the fuel nozzles <NUM>. In many embodiments, the first fuel <NUM> may be a fuel mixture containing natural gas (such as methane, ethane, propane, or other suitable natural gas) and hydrogen. In other embodiments, the first fuel <NUM> may be pure natural gas or pure hydrogen (e.g., <NUM>% hydrogen, which may or may not contain some amount of contaminants), such that the first fuel is not a mixture of multiple fuels.

In exemplary embodiments, the first fuel <NUM> and compressed air <NUM> may mix together within the fuel nozzles <NUM> to form a first mixture of compressed air <NUM> and the first fuel <NUM> before being ejected (or injected) by the fuel nozzles <NUM> into the primary combustion zone <NUM>. The first mixture of the first fuel <NUM> and compressed air <NUM> may be injected into the primary combustion zone <NUM> and ignited to generate a first flow of combustion gases <NUM> having a first temperature.

As discussed below, during operation of the combustor <NUM> on a total fuel input that comprises a high amount of hydrogen (e.g., greater than about <NUM>%), the temperature of combustion gases within the primary combustion zone <NUM> (e.g., the first flow of combustion gases <NUM>) may be the lowest temperature of any of any combustion gases within the combustion chamber <NUM> (e.g., lower than the combustion gases within the secondary combustion zone <NUM>). Operated in this way, the temperature of combustion gases within the primary combustion zone <NUM> may be a lower temperature than combustion gases in the secondary combustion zone <NUM>, which may advantageously enable the combustor <NUM> to operate on high amounts of hydrogen without creating potentially damaging flame holding and/or flashback conditions.

The forward casing <NUM> may be fluidly and mechanically connected to a compressor discharge casing <NUM>, which defines a high pressure plenum <NUM> around the combustion liner <NUM> and the outer sleeve <NUM>. Compressed air <NUM> from the compressor section <NUM> travels through the high pressure plenum <NUM> and enters the combustor <NUM> via apertures (not shown) in the downstream end of the outer sleeve <NUM> (as indicated by arrows near an aft frame <NUM>). Compressed air travels upstream through the annulus <NUM> and is turned by the end cover <NUM> to enter the fuel nozzles <NUM> and to cool the head end. In particular, compressed air <NUM> flows from high pressure plenum <NUM> into the annulus <NUM> at an aft end of the combustor <NUM>, via openings defined in the outer sleeve <NUM>. The compressed air <NUM> travels upstream from the aft end of the combustor <NUM> to the head end air plenum <NUM>, where the compressed air <NUM> reverses direction and enters the fuel nozzles <NUM>.

In the exemplary embodiment, a fuel injection assembly <NUM> is provided to deliver a second fuel/air mixture and/or a flow of pure fuel (e.g., <NUM>% fuel, such as hydrogen, not mixed with air) to a secondary combustion zone <NUM>. For example, a second flow of fuel and air may be introduced by one or more premix injectors <NUM> to the secondary combustion zone <NUM>, and a flow of supplemental fuel may be introduced by one or more supplemental or immersed injectors <NUM>.

The primary combustion zone <NUM> and the secondary combustion zone <NUM> may each be portions of the combustion chamber <NUM> and therefore may be defined by the combustion liner <NUM>. For example, the primary combustion zone <NUM> may be defined from an outlet of the fuel nozzles <NUM> to the premix injector <NUM>, and the secondary combustion zone may be defined from the premix injector <NUM> to the aft frame <NUM>. In this arrangement, the forward most boundary of the premix injector <NUM> may define the end of the primary combustion zone <NUM> and the beginning of the secondary combustion zone <NUM> (e.g., at an axial location where a second flow of fuel and air are introduced).

Such a combustion system having axially separated combustion zones is described as an "axial fuel staging" (AFS) system. The fuel injection assemblies <NUM> may be circumferentially spaced apart from one another on the outer sleeve <NUM> (e.g., equally spaced apart in some embodiments). In many embodiments, the combustor <NUM> may include four fuel injection assemblies <NUM> spaced apart from one another and configured to inject a second mixture of fuel and air into a secondary combustion zone <NUM> via the premix injector <NUM> and configured to inject a flow of pure fuel (e.g., a fuel mixture or pure hydrogen) via the immersed injector <NUM>, in order to increase the combustion gases <NUM> and temperature thereof. In other embodiments, the combustor <NUM> may include any number of fuel injection assemblies <NUM> (e.g., <NUM>, <NUM>, <NUM>, or up to <NUM>).

As shown in <FIG>, each fuel injection assembly <NUM> may include a premix injector <NUM>, an immersed injector <NUM>, a second fuel supply conduit <NUM> that supplies a second fuel (such as pure hydrogen or a natural gas and hydrogen mixture comprising greater than <NUM>% hydrogen) to the premix injector <NUM>, and a third fuel supply conduit <NUM> that supplies a pure fuel (e.g., a fuel mixture or pure hydrogen) to the immersed injector <NUM>. For example, each premix injector <NUM> may be in fluid communication, at least partially via the second fuel supply conduit <NUM>, with a second fuel supply <NUM> configured to supply a second fuel <NUM> to each premix injector <NUM>. In many embodiments, the second fuel <NUM> may be a fuel mixture containing natural gas (such as methane, ethane, propane, or other suitable natural gas) and hydrogen. In other embodiments, the second fuel <NUM> may be pure natural gas or pure hydrogen (e.g., <NUM>% hydrogen), such that the second fuel includes no other fuels mixed therein. Similarly, each immersed injector <NUM> may be in fluid communication, at least partially via the third fuel supply conduit <NUM>, with a third fuel supply <NUM> configured to supply a third fuel <NUM> to each immersed injector <NUM>. In exemplary embodiments, the third fuel <NUM> may be pure fuel (e.g., a fuel mixture or pure hydrogen), such that the third fuel includes no other fuels or air mixed therein.

Because the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM> are separately fueled (e.g., via the fuel supplies <NUM>, <NUM>, and <NUM>), they may allow the combustor a wide range of operational flexibility. For example, each of the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM> may be supplied with a different fuel or fuel mixture. Particularly, in exemplary embodiments, each of the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM> may be supplied pure hydrogen or a fuel mixture that contains mostly hydrogen (e.g., greater than <NUM>% hydrogen) and natural gas (such as methane, ethane, propane, or other natural gas). However, it should be appreciated that, in some embodiments, each of the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM> may be fueled by the same fuel supply, such that the same fuel mixture or pure fuel is supplied to all of the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM>.

As used herein, the term "premix" may be used to describe a component, passage, or cavity in which fuel and air are mixed together prior to being injected into the combustion chamber <NUM>. In many embodiments, each premix injector <NUM> may fluidly couple the high pressure plenum <NUM> to the secondary combustion zone <NUM>. For example, compressed air <NUM> from the high pressure plenum <NUM> may enter the premix injector <NUM> where it is mixed with the second fuel <NUM> prior to being injected into the secondary combustion zone <NUM>. For example, in exemplary embodiments, each premix injector <NUM> may extend through the outer sleeve <NUM>, the annulus <NUM>, and the combustion liner <NUM> and into the secondary combustion zone <NUM>. Specifically, the premix injectors <NUM> may each extend radially from the high pressure plenum <NUM>, through the outer sleeve <NUM>, the annulus <NUM>, and the combustion liner <NUM>, such that the premix injector <NUM> is capable of delivering a second flow of fuel and air to the secondary combustion zone <NUM>. The premix injectors <NUM> may be coupled to the combustion liner <NUM> and/or the outer sleeve <NUM>, such that each premix injector <NUM> introduces the second fuel/air mixture as a jet entering a cross-flow (such as at an angle, oblique, orthogonal, slantwise, diagonally, transverse, or nonparallel) of the combustion products <NUM> produced in the primary combustion zone <NUM>. The second fuel/air mixture(s) are ignited by the combustion products <NUM> from the primary combustion zone <NUM> and burn in the secondary combustion zone <NUM>.

The premix injector <NUM> may be coupled to the outer sleeve <NUM> and may extend through the outer sleeve <NUM> and the combustion liner <NUM>. In one embodiment, a boss (not shown) supporting the premix injector <NUM> functions as a fastener for securing the outer sleeve <NUM> to the combustion liner <NUM>. In other embodiments, the premix injector <NUM> may be coupled to the outer sleeve <NUM> in any suitable manner, and the outer sleeve <NUM> may have any suitable number of components coupled between the flange of the forward casing <NUM> and the turbine nozzle in any suitable manner that permits the fuel injection assembly <NUM> to function as described herein.

In exemplary embodiments, the second fuel <NUM> and compressed air <NUM> may mix together within the premix injectors <NUM> to form a second mixture of compressed air <NUM> and the second fuel <NUM> before being ejected (or injected) by the premix injectors <NUM> into the secondary combustion zone <NUM>. The second mixture of the second fuel <NUM> and compressed air <NUM> may be injected (e.g., as a cross-flow, such as generally radially) into the secondary combustion zone <NUM> and ignited to generate a second flow of combustion gases <NUM> having a second temperature.

The immersed injector <NUM> may extend radially through the premix injector (e.g., through the center of the premix injector <NUM>) and into the secondary combustion zone <NUM>. For example, the immersed injector <NUM> may extend radially into the secondary combustion zone <NUM> of the combustion chamber <NUM>, such that the immersed injector <NUM> is directly exposed to combustion gases during operation of the combustor <NUM>. As described above, although the immersed injector extends through the premix injector <NUM>, the immersed injector <NUM> may be fluidly isolated from the premix injector <NUM>. In this arrangement, the immersed injector <NUM> may separately inject a flow of third fuel <NUM> (e.g., a fuel mixture, such as hydrogen and natural gas, or entirely fuel, such as pure hydrogen not mixed with air or other oxidants) directly into the secondary combustion zone <NUM> to generate a third flow of combustion gases <NUM>. In this way, the third fuel <NUM> may be introduced by the immersed injector <NUM> (or supplemental injector) as a supplemental fuel that generates additional combustion gases <NUM> proximate the exit of the combustion chamber <NUM> (e.g., closer to the aft frame <NUM> than the end cover <NUM>), which may advantageously allow the combustor <NUM> to generate outlet combustion gases <NUM> having an outlet temperature without any potentially dangerous flashback or flame holding events. As should be appreciated, the third fuel <NUM> may be airless (or oxidant-less), such that no air or other oxidants are mixed therein. In this way, the third fuel <NUM> may be a pure fuel or pure hydrogen. In exemplary implementations, the first flow of combustion gases <NUM>, the second flow of combustion gases <NUM>, and the third flow of combustion gases <NUM> may mix together within the secondary combustion zone <NUM> to form outlet combustion gases <NUM> (<NUM> in <FIG>) having an outlet temperature. The outlet combustion gases <NUM> may exit the combustor <NUM> via the aft frame <NUM> and enter the turbine section <NUM> of the gas turbine <NUM>.

Although the immersed injector <NUM> in <FIG> extends radially through the premix injector <NUM> and into the secondary combustion zone <NUM>, it should be understood that the immersed injector <NUM> may be axially spaced apart and disposed downstream from the premix injector <NUM> with respect to the flow of combustion gases. For example, the immersed injector <NUM> may be disposed axially between the premix injector <NUM> and the aft frame <NUM> with respect to the axial centerline <NUM>. In such embodiments, the immersed injector <NUM> may extend independently through the outer sleeve <NUM>, the annulus <NUM>, the combustion liner <NUM>, and into the secondary combustion zone <NUM>.

During operation of the combustor <NUM> on a total fuel input that comprises a high amount of hydrogen (e.g., greater than about <NUM>%), the temperature of combustion gases within the secondary combustion zone (e.g., outlet combustion gases <NUM>) may be the highest temperature of any of any combustion gases within the combustion chamber. Specifically, the temperature of combustion gases <NUM>, <NUM> within the secondary combustion zone <NUM> may be a higher temperature than combustion gases <NUM> in the primary combustion zone <NUM>, which may advantageously enable the combustor <NUM> to operate on high amounts of hydrogen (or entirely on hydrogen) without experiencing potentially damaging flame holding and/or flashback conditions.

<FIG> provides a cross-sectional side view of a portion of a bundled tube fuel nozzle <NUM>. In exemplary embodiments, the one or more fuel nozzles <NUM> shown in <FIG> may each be a bundled tube fuel nozzle <NUM>. As shown in <FIG>, the bundled tube fuel nozzle <NUM> includes a fuel plenum body <NUM> having a forward or upstream plate <NUM>, an aft plate <NUM> axially spaced from the forward plate <NUM> and an outer band or shroud <NUM> that extends axially between the forward plate <NUM> and the aft plate <NUM>. A fuel plenum <NUM> is defined within the fuel plenum body <NUM>. In particular embodiments, the forward plate <NUM>, the aft plate <NUM> and the outer band <NUM> may at least partially define the fuel plenum <NUM>. In particular embodiments, the fuel supply conduit <NUM> may extend through the forward plate <NUM> to provide fuel (such as pure hydrogen or a fuel mixture comprising greater than <NUM>% hydrogen) to the fuel plenum <NUM>. In various embodiments, the bundled tube fuel nozzle <NUM> includes a cap plate <NUM> axially spaced from the aft plate <NUM>. A hot side <NUM> of the cap plate <NUM> is generally disposed adjacent or proximate to the primary combustion zone <NUM>. The cap plate <NUM> may be unique to each bundled tube fuel nozzle <NUM> or may be common among all the bundled tube fuel nozzles <NUM> (e.g., such as the cap plate <NUM> shown in <FIG>).

As shown in <FIG>, the bundled tube fuel nozzle <NUM> may include a tube bundle <NUM> comprising a plurality of premix tubes <NUM>. Each premix tube <NUM> may extend through the forward plate <NUM>, the fuel plenum <NUM>, the aft plate <NUM>, and the cap plate <NUM>. The premix tubes <NUM> are fixedly connected to and/or form a seal against the aft plate <NUM>. For example, the premix tubes <NUM> may be welded, brazed or otherwise connected to the aft plate <NUM>. Each premix tube <NUM> includes an inlet <NUM> defined at an upstream end <NUM> of each respective tube <NUM> and an outlet <NUM> defined at a downstream end <NUM> of each respective tube <NUM>. Compressed air from the head end <NUM> may enter each of the premix tubes <NUM> at the inlet and may be mixed with fuel before being expelled into the primary combustion zone. For example, each premix tube <NUM> defines a respective premix flow passage <NUM> through the bundled tube fuel nozzle <NUM>, in which fuel (such as pure hydrogen or a fuel mixture comprising greater than <NUM>% hydrogen) may be mixed with compressed air. In particular embodiments, one or more premix tubes <NUM> of the plurality of tubes <NUM> is in fluid communication with the fuel plenum <NUM> via one or more fuel ports <NUM> defined within the respective premix tube(s) <NUM>.

<FIG> illustrates an enlarged perspective view of a fuel injection assembly <NUM>, in accordance with embodiments of the present disclosure. As shown the fuel injection assembly <NUM> may include a premix injector <NUM>, an immersed injector <NUM>, a second fuel supply conduit <NUM> that supplies a second fuel to the premix injector <NUM>, and a third fuel supply conduit <NUM> that supplies a third fuel to the immersed injector <NUM>. The second fuel and the third fuel may be pure (i.e., unmixed) hydrogen or a mixture of natural gas and hydrogen with greater than <NUM>% hydrogen (e.g., diatomic hydrogen gas). The second fuel and the third fuel may be the same fuel or may be different fuels. In some embodiments (not shown), the fuel injection assembly <NUM> may only include a singular fuel supply conduit that supplies fuel to both the immersed injector <NUM> and the premix injector <NUM>. As shown, the premix injector <NUM> extend radially between a radially outer end <NUM> and a radially inner end <NUM>.

In exemplary embodiments, the premix injector <NUM> may include end walls <NUM> axially spaced apart from each other and side walls <NUM> extending between the end walls <NUM>. For example, the side walls <NUM> extend axially between the end walls <NUM> along the axial direction A. The end walls <NUM> of the premix injector <NUM> may include a forward end wall and an aft end wall disposed oppositely from one another. The side walls <NUM> may be spaced apart from one another and may each extend axially between the forward end wall and the aft end wall. In many embodiments, one set of walls (e.g., the side walls <NUM>) may be generally arcuate or curved, and the other set of walls (e.g., the end walls <NUM>) may be generally straight. In some embodiments, as shown, the end walls <NUM> and the side walls <NUM> may collectively define a geometric stadium shaped area, i.e., a rectangle with rounded ends, that outlines and defines a perimeter of the opening <NUM>. In other embodiments (not shown), the end walls <NUM> may be straight such that end walls <NUM> and the side walls <NUM> collectively define a rectangular shaped area.

An opening may be defined between the end walls <NUM> and the side walls <NUM> of the premix injector <NUM>. In many embodiments, the premix opening <NUM> may be longer in the axial direction A than in the circumferential direction C, thereby advantageously allowing the opening <NUM> to introduce a large amount of fuel and air into the combustion chamber <NUM> without having the premix injector <NUM> impede a large portion of the annulus <NUM> through which it extends. For example, in various embodiments, the opening <NUM> may have a variety of cross-sectional shapes, such as but not limited to a rectangle, oval, stadium shape (e.g., a rectangle having arced or curved ends), or other suitable shapes. Although the premix injector <NUM> and the opening <NUM> are illustrated as having a geometric stadium shape, it should be understood that the premix injector <NUM> and its opening <NUM> may have a different shape (e.g., a round shape) or that the opening <NUM> may have a shape that is different from the outermost perimeter of the premix injector <NUM>.

A plurality of ribs <NUM> may extend within the opening <NUM> of the premix injector <NUM> and may at least partially define a plurality of premix passages <NUM> each extending between an air inlet <NUM> disposed at the radially outer end <NUM> and an outlet <NUM> disposed at the radially inner end <NUM>. For example, the plurality of ribs <NUM> may include at least one axial rib <NUM> extending along the axial direction A between the end walls <NUM> (e.g., from the forward end wall to the aft end wall). Additionally, or alternatively, the plurality of ribs <NUM> may include circumferential ribs <NUM> axially spaced apart from one another and each extending between the side walls <NUM>. As shown in <FIG>, the at least one axial rib <NUM> and one or more of the circumferential ribs <NUM> may couple to the immersed injector <NUM> (e.g., at a base <NUM> of the immersed injector <NUM>). In many embodiments, the immersed injector <NUM> may be spaced apart from both the end walls <NUM> and the side walls <NUM> and may extend from within the opening <NUM> (e.g., from a center point of the opening <NUM>). The plurality of ribs <NUM> may couple to, and at least partially support or suspend, the immersed injector <NUM> within the opening <NUM> (e.g., at the base <NUM> of the immersed injector <NUM>).

Additionally, the immersed injector <NUM> may extend radially through the opening <NUM> (such as through a center point of the opening <NUM>) of the premix injector <NUM> and directly into the combustion chamber <NUM>. The immersed injector <NUM> may have a generally contoured aerodynamic shape (such as a teardrop shaped cross-section) in order to minimize disruption to flow of the combustion gases around the immersed injector <NUM> during operation of the combustor <NUM>. For example, the immersed injector <NUM> may define an airfoil <NUM> extending radially from a base <NUM> at the radially inner end <NUM> to a tip <NUM>. The entire airfoil <NUM> (e.g., from the base <NUM> to the tip <NUM>) may be disposed within the secondary combustion zone <NUM>. Additionally, the immersed injector <NUM> may include a leading edge <NUM>, a trailing edge <NUM>, and side surfaces <NUM> extending between the leading edge <NUM> and the trailing edge <NUM>. In many embodiments, the leading edge <NUM> and the trailing edge <NUM> may face the end walls <NUM> (but be spaced apart therefrom), and the side surfaces <NUM> may generally face the side walls <NUM> (but be spaced apart therefrom). During operation of the immersed injector <NUM>, the combustion gases may engage the airfoil <NUM> at the leading edge <NUM> and may travel along the side surfaces <NUM> to the trailing edge <NUM>.

One or more fuel ports <NUM> may be defined on the side surface(s) <NUM> to inject pure fuel (such as hydrogen) directly into the combustion chamber <NUM>. For example, the one or more fuel ports <NUM> may be in fluid communication with the third fuel supply <NUM>. In this way, the immersed injector <NUM> may receive fuel from the third fuel supply <NUM> and may expel (or inject) the fuel into the secondary combustion zone via the fuel ports <NUM>. In some embodiments, as shown in <FIG>, the fuel ports <NUM> may be arranged in a row and may be generally aligned (e.g., along a common axis) on the side surface <NUM> of the airfoil <NUM>. Contrary to both the fuel nozzles <NUM> and the premix injector <NUM>, in exemplary embodiments, the immersed injector <NUM> does not introduce (or inject) a premix flow of air and fuel into the combustion chamber <NUM>. Rather, the immersed injector <NUM> introduces pure fuel (such as pure hydrogen not mixed with air) into the combustion chamber <NUM>, which advantageously allows the combustor <NUM> to operate on high amounts of total hydrogen.

In exemplary embodiments, the immersed injector <NUM> is surrounded by one or more premix passages <NUM> of the plurality of premix passages <NUM>. For example, the immersed injector <NUM> may at least partially define a boundary of one or more of the premix passages <NUM>, such that the premix passages <NUM> surrounding the immersed injector are collectively defined by the plurality of ribs <NUM>, one of the side walls <NUM>, and the immersed injector <NUM>. Positioning the immersed injector <NUM> within the opening <NUM>, and surrounded by one or more of the premix passages <NUM>, advantageously allows the airfoil <NUM> to be cooled by the mixture <NUM> of air and fuel exiting the premix passages <NUM> of the premix injector <NUM>.

<FIG> is a graph <NUM> of flame temperature over outlet temperature (expressed as a percentage) vs. the percentage of hydrogen present in the total fuel input to the combustor <NUM>, in which line <NUM> is the temperature of outlet combustion gases <NUM>, line <NUM> is the temperature of the first flow of combustion gases <NUM> generated by the fuel nozzles <NUM>, and line <NUM> is the temperature of the second flow of combustion gases <NUM> generated by the fuel injection assemblies <NUM> (i.e., the premix injectors <NUM> and the immersed injectors <NUM>). The total fuel input may include all of the fuel that is supplied to the combustor <NUM> (including the fuel supplied to the fuel nozzles <NUM>, the premix injectors <NUM>, and the immersed injectors <NUM>). The horizontal line <NUM> may be the outlet temperature of the outlet combustion gases <NUM> (e.g., the combustor exit temperature of the combustion gases). As shown by the horizontal line <NUM>, the outlet temperature may be unchanged regardless of what percentage of the total fuel input consists of hydrogen. The line <NUM> may be the flame temperature at the outlet of the fuel nozzles <NUM> within the primary combustion zone <NUM>, e.g., the flame temperature of the first flow of combustion gases <NUM>. Additionally, the line <NUM> may be the flame temperature at the outlet of the premix injector <NUM> within the secondary combustion zone <NUM>, e.g., the flame temperature of the second flow of combustion gases <NUM>.

As shown, as the percentage of hydrogen present in the total fuel input supplied to the combustor increases above <NUM>%, the flame temperature of the second flow of combustion gases <NUM> may increase above the flame temperature of the first flow of combustion gases <NUM>, which advantageously allows the combustor to operate on high amounts of hydrogen without entering a flame holding or flashback condition.

In many embodiments, the outlet temperature of the outlet combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx. In other embodiments, the outlet temperature of the combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx. In some embodiments, the outlet temperature of the combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx.

<FIG> is a graph <NUM> of the percentage of total fuel input supplied to the immersed injectors <NUM> vs. the percentage of hydrogen present in the total fuel input to the combustor <NUM>, in which the line <NUM> represents the amount of fuel supplied to the immersed injectors <NUM>. As depicted, when the percentage of hydrogen in the total fuel input supplied to the combustor <NUM> is present at levels above <NUM>%, the immersed injectors <NUM> may be supplied with fuel (e.g., hydrogen) unmixed with air or other oxidants. When operating on <NUM>% hydrogen, about <NUM>% of the total fuel input may be supplied to the immersed injectors <NUM>. This advantageously allows the combustor <NUM> to maintain the required outlet temperature without causing the fuel nozzles <NUM> or the premix injectors <NUM> to enter flashback and/or flame holding conditions that could otherwise be caused by operating on high amounts of hydrogen.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> of operating a combustor <NUM> of a turbomachine <NUM> on a total fuel input that contains a concentration of hydrogen that is greater than about <NUM>% to generate outlet combustion gases <NUM> having an outlet temperature is illustrated in accordance with aspects of the present subject matter. In general, the method <NUM> will be described herein with reference to the combustor <NUM>, the bundled tube fuel nozzle <NUM>, the fuel injection assembly <NUM>, and the graphs <NUM>, <NUM> described above and with reference to <FIG>. However, it should be understood that the method <NUM> may be utilized with any suitable combustor for a turbomachine without deviating from the scope of the present disclosure. Additionally, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

As shown in <FIG>, the method <NUM> may include a step <NUM> of injecting, with at least one fuel nozzle <NUM>, a first mixture of air and a first fuel <NUM> containing hydrogen (e.g., diatomic hydrogen gas) into the primary combustion zone <NUM> of the combustor <NUM> to generate a first flow of combustion gases <NUM> having a first temperature. For example, the first mixture of compressed air <NUM> and the first fuel <NUM> may be delivered to the primary combustion zone <NUM> by the fuel nozzles <NUM> (which, in some embodiments, may be bundled tube fuel nozzles <NUM> in accordance with <FIG>). In various embodiments the first fuel <NUM> may be a mixture of natural gas (such as methane, ethane, propane, or other natural gas) and hydrogen. In exemplary embodiments, the first fuel <NUM> may include a high concentration of hydrogen (such as greater than about <NUM>% hydrogen), with the remainder of the first fuel <NUM> being one or more natural gases.

In exemplary embodiments, the method <NUM> may include a step <NUM> of injecting, with one or more premix injectors <NUM> disposed downstream of the fuel nozzles <NUM>, a second mixture of air and a second fuel <NUM> containing hydrogen (e.g., diatomic hydrogen gas) into the secondary combustion zone <NUM> of the combustor <NUM> as a cross-flow to generate a second flow of combustion gases <NUM> having a second temperature. For example, the second mixture of compressed air <NUM> and the second fuel <NUM> may be delivered to the secondary combustion zone <NUM> by the premix injectors <NUM>. In various embodiments, the second fuel <NUM> may be a mixture of natural gas (such as methane, ethane, propane, or other natural gas) and hydrogen (such as diatomic hydrogen gas). In exemplary embodiments, the second fuel <NUM> may include a high concentration of hydrogen (such as greater than about <NUM>% hydrogen), with the remainder of the second fuel <NUM> being one or more natural gases.

In exemplary implementations of the method <NUM>, the second temperature of the second flow of combustion gases <NUM> may be greater than the first temperature of the first flow of combustion gases <NUM>. This may advantageously allow the combustor <NUM> to operate on a total fuel input that contains a concentration of hydrogen that is greater than <NUM>% without experiencing flame holding and/or flashback conditions.

In many embodiments, the method <NUM> may further include a step <NUM> of separately injecting a third fuel <NUM> as a pure fuel (e.g., diatomic hydrogen gas) into secondary combustion zone <NUM>. The third fuel <NUM> ignites and mixes with the first flow and the second flow of combustion gases <NUM>, <NUM> to generate outlet combustion gases <NUM> (<NUM> in <FIG>) having a third temperature. In exemplary embodiments, the third temperature of the outlet combustion gases <NUM> may be greater than the first temperature of the first flow of combustion gases <NUM> (such as <NUM>%, <NUM>%, <NUM>%, or <NUM>%) greater, which advantageously allows the combustor <NUM> to operate on high amounts of hydrogen without entering potential flashback conditions. In some embodiments, the third temperature of the outlet combustion gases <NUM> may be generally equal to the outlet temperature of the combustor <NUM> (e.g., within ±<NUM>%). In various embodiments, the third fuel may be a fuel mixture, such as natural gas (e.g., methane, ethane, or propane) and hydrogen (e.g., diatomic hydrogen gas). For example, the third fuel may contain a high amount of hydrogen, such as <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% hydrogen.

In many implementations, the step <NUM> may be performed by the immersed injector <NUM> described above with reference to <FIG> and <FIG>. For example, in contrast with the fuel nozzles <NUM> and the premix injector <NUM>, which both deliver a mixture of fuel/air to the combustion chamber <NUM>, the immersed injector <NUM> may advantageously deliver only fuel (e.g., not mixed with air) to the combustion chamber <NUM>. The fuel may be a fuel mixture containing hydrogen and natural gas or may be only hydrogen not mixed with other fuels. In exemplary embodiments, as shown in <FIG> and <FIG>, the third fuel <NUM> may be injected at the axial location of the one or more premix injectors <NUM> into the secondary combustion zone <NUM>. For example, the immersed injector <NUM> may extend through a center point of the premix injector <NUM>.

Alternately, in other embodiments, the third fuel <NUM> may be injected downstream of the one or more premix injectors <NUM> into the secondary combustion zone <NUM>. For example, the immersed injectors <NUM> may be entirely separated from the premix injectors <NUM> and may extend into the combustion chamber <NUM> downstream of the premix injectors <NUM>.

In some implementations, the method <NUM> may include an optional step of increasing the concentration of hydrogen from about <NUM>% to about <NUM>% while maintaining the outlet temperature. In such a step, the combustor <NUM> may shift from operation on mostly hydrogen (with some natural gas mixed therein) to operation on entirely hydrogen (having no other fuels mixed therein). As a result of increasing the concentration of hydrogen from about <NUM>% to about <NUM>%, the first temperature of the first flow of combustion gases <NUM> may decrease and the second temperature of the second flow of combustion gases <NUM> may decrease while remaining equal to or above the first temperature.

In order to facilitate the transition from <NUM>% to <NUM>% hydrogen while maintaining the required outlet temperature and without creating a flame holding or flashback incident, as shown by <FIG>, an amount of hydrogen supplied to the immersed injector <NUM> may be simultaneously increased to substitute for the loss of temperature in the first and second flow of combustion gases <NUM>, <NUM>. For example, when operating the combustor <NUM> when the concentration of hydrogen available in the fuel has been increased from about <NUM>% to about <NUM>% (while maintaining the outlet temperature), the method <NUM> may include simultaneously increasing an amount of the third fuel <NUM> (e.g., hydrogen) injected into the secondary combustion zone without air such that the third fuel <NUM> comprises up to about <NUM>% of the total fuel input to the combustor <NUM>.

In some embodiments, the method <NUM> may further include a step of mixing the first flow of combustion gases <NUM>, the second flow of combustion gases <NUM>, and the third flow of combustion gases <NUM> within the secondary combustion zone to generate the outlet combustion gases <NUM> having the outlet temperature. For example, the outlet temperature of the outlet combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx. In other embodiments, the outlet temperature of the combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx. In some embodiments, the outlet temperature of the combustion gases <NUM> may be between about <NUM>°F (approx. <NUM>) and about <NUM>°F (approx.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> of operating a combustor <NUM> is illustrated in accordance with aspects of the present subject matter. In general, the method <NUM> will be described herein with reference to the combustor <NUM>, the bundled tube fuel nozzle <NUM>, the fuel injection assembly <NUM>, and the graphs <NUM>, <NUM> described above and with reference to <FIG>. However, it should be understood that the method <NUM> may be utilized with any suitable combustor for a turbomachine without deviating from the scope of the present disclosure. Additionally, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

In many embodiments, the method <NUM> may include a step <NUM> of injecting, with at least one fuel nozzle <NUM>, a first mixture of air and a first fuel <NUM> into a primary combustion zone <NUM> of the combustor <NUM> to generate a first flow of combustion gases <NUM> having a first temperature. For example, the first mixture of compressed air <NUM> and first fuel <NUM> (such as a fuel mixture containing natural gas and/or hydrogen, such as diatomic hydrogen gas) may be delivered to the primary combustion zone <NUM> by the fuel nozzles <NUM> (which, in some embodiments, may be bundled tube fuel nozzles <NUM> in accordance with <FIG>).

The method <NUM> may further include a step <NUM> of injecting, with one or more premix injectors <NUM> disposed downstream of the fuel nozzles <NUM>, a second mixture of air and a second fuel <NUM> into a secondary combustion zone <NUM> of the combustor as a cross-flow to generate a second flow of combustion gases <NUM> having a second temperature. Additionally, the method <NUM> may further include a step <NUM> of separately injecting a third fuel <NUM> as a pure fuel into secondary combustion zone, the third fuel igniting and mixing with the first flow and the second flow of combustion gases <NUM>, <NUM> to generate outlet of combustion gases <NUM> having a third temperature.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> of operating a combustor <NUM> of a turbomachine on a total fuel input that contains a <NUM>% concentration of hydrogen to generate outlet combustion gases <NUM> having an outlet temperature is illustrated in accordance with aspects of the present subject matter. In general, the method <NUM> will be described herein with reference to the combustor <NUM>, the bundled tube fuel nozzle <NUM>, the fuel injection assembly <NUM>, and the graphs <NUM>, <NUM> described above and with reference to <FIG>. However, it should be understood that the method <NUM> may be utilized with any suitable combustor for a turbomachine without deviating from the scope of the present disclosure. Additionally, although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

As shown, in exemplary embodiments, the method <NUM> may include a step <NUM> of injecting, with at least one fuel nozzle <NUM>, a first mixture of air and hydrogen into the primary combustion zone <NUM> of the combustor <NUM> to generate a first flow of combustion gases <NUM> having a first temperature. For example, the first mixture of compressed air <NUM> and hydrogen may be delivered to the primary combustion zone <NUM> by the fuel nozzles <NUM> (which, in some embodiments, may be bundled tube fuel nozzles <NUM> in accordance with <FIG>).

In many embodiments, the method <NUM> may include a step <NUM> of injecting, with one or more premix injectors <NUM> disposed downstream of the fuel nozzles <NUM>, a second mixture of air and hydrogen into the secondary combustion zone <NUM> of the combustor <NUM> as a cross-flow to generate a second flow of combustion gases <NUM> having a second temperature. For example, the second mixture of compressed air <NUM> and hydrogen may be delivered to the secondary combustion zone <NUM> by the premix injectors <NUM>.

Claim 1:
A method of operating a combustor of a turbomachine, the method comprising:
injecting, with at least one fuel nozzle (<NUM>, <NUM>), a first mixture of air (<NUM>) and a first fuel (<NUM>) containing diatomic hydrogen gas into a primary combustion zone (<NUM>) of the combustor (<NUM>) to generate a first flow of combustion gases (<NUM>) having a first temperature;
injecting, with one or more premix injectors (<NUM>) disposed downstream of the at least one fuel nozzle (<NUM>, <NUM>), a second mixture of air (<NUM>) and a second fuel (<NUM>) containing diatomic hydrogen gas into a secondary combustion zone (<NUM>) of the combustor (<NUM>) as a cross-flow to generate a second flow of combustion gases (<NUM>) having a second temperature; and
separately injecting a third fuel (<NUM>) as a pure fuel into secondary combustion zone (<NUM>), the third fuel (<NUM>) igniting and mixing with the first flow and the second flow of combustion gases (<NUM>, <NUM>) to generate outlet combustion gases (<NUM>, <NUM>) having a third temperature.