Patent Description:
In at least some known rotary machines, energy extracted from a gas stream in a turbine is used to power a mechanical load. Specifically, the rotary machine includes a compressor section, a combustor section, and a turbine section arranged in a serial flow arrangement. The compressor section compresses air for combustion with fuel within the combustor section, and the turbine section extracts energy from the combustion gases generated in the combustion section. At least some known combustion sections include Axial Fuel Staging (AFS) technology including axial (sequential) staging of combustion in at least two zones. More specifically, the combustion section may include a plurality of first stage fuel nozzles positioned upstream of a plurality of second stage fuel nozzles. A first flow of fuel is channeled into the combustor by the first stage fuel nozzles, and a second flow of fuel is channeled into the combustor by the second stage fuel nozzles. The intra-combustor temperature of the combustion gases generated by the combustion of the first flow of fuel is the T<NUM> temperature. Controlling the T<NUM> temperature and the air from the compressor section enables an operator to control the emissions generated by the rotary machine. More specifically, carbon monoxide emissions generated by the rotary machine are typically controlled through control of the T3. <NUM> temperature.

Additionally, rotary machines typically have a Minimum Emissions Compliance Load (MECL) that is the lowest load on the rotary machine in which the rotary machine can operate while still in compliance with emissions standards. More specifically, traditional MECL is the lowest load on the rotary machine in which the combustor temperature facilitates maintaining compliance with emissions standards. When grid operators request that the operator of the rotary machine reduce operation of the rotary machine such that the rotary machine is operating below the MECL, the operator of the rotary machine turns off the rotary machine to maintain compliance with emission standards. As such, a rotary machine with a high MECL will result in the rotary machine ceasing operations more often than a rotary machine with a lower MECL, resulting in lost revenue for the operator of the high MECL rotary machine.

<CIT> relates to a combustor assembly for a gas turbine engine. The combustor includes a combustor endcover having at least one fuel circuit and mounted thereto a plurality of pre-mixers and at least one control valve. The at least one control valve is fluidly connected to the at least one fuel circuit and operatively connected to a controller. The controller selectively operates the at least one control valve to deliver fuel through the at least one fuel circuit to the plurality of pre-mixers in order to achieve an enhanced level of operational flexibility by providing individual combustion chamber control.

In one aspect, a method of operating a rotary machine below a traditional minimum emissions compliance load in a response mode is provided. The rotary machine includes a combustor including a first combustion zone and a second combustion zone. The method includes i) reducing a fuel split to zero. The fuel split apportions a total flow of fuel to the combustor between the first combustion zone and the second combustion zone. The method also includes ii) determining a current operating temperature of the first combustion zone using a digital simulation of the rotary machine. The method further includes iii) determining a target operating temperature of the first combustion zone. The target operating temperature enables the rotary machine to operate below a traditional Minimum Emissions Compliance Load (MECL) while still in compliance with emissions standards. The method also includes iv) channeling a first flow of fuel to the first combustion zone. The first flow of fuel decreases the temperature of the first combustion zone to the target operating temperature. The method further includes v) iterating steps i through iv until the rotary machine is operating below the traditional MECL and complying with emission standards.

In another aspect, a method of operating a rotary machine below a traditional minimum emissions compliance load in a standby mode is provided. The rotary machine includes a combustor including a first combustion zone and a second combustion zone. The method includes i) reducing a fuel split to zero. The fuel split apportions a total flow of fuel to the combustor between the first combustion zone and the second combustion zone. The method also includes ii) determining a current operating temperature of the first combustion zone using a digital simulation of the rotary machine. The method further includes iii) determining a target operating temperature of the first combustion zone. The target operating temperature enables the rotary machine to operate below a traditional Minimum Emissions Compliance Load (MECL) while still in compliance with emissions standards. The method also includes iii) determining a target operating temperature of the first combustion zone. The target operating temperature enables the rotary machine to operate below a traditional Minimum Emissions Compliance Load (MECL) while still in compliance with emissions standards. The method further includes iv) channeling a first flow of fuel to the first combustion zone. The first flow of fuel decreases the temperature of the first combustion zone to the target operating temperature and decreases a temperature of exhaust gases from the rotary machine below a minimum exhaust temperature for operation of a power plant. The method also includes v) iterating steps i through iv until the rotary machine is operating below the traditional MECL and complying with emission standards.

In yet another aspect, a rotary machine is provided. The rotary machine includes a compressor configured to compress a flow of inlet air, a combustor, and a computing device. The combustor includes a first combustion zone, a second combustion zone, at least one first fuel nozzle, and at least one second fuel nozzle. The at least one first fuel nozzle is configured to channel a first flow of fuel to the first combustion zone, and the at least one second fuel nozzle is configured to channel a second flow of fuel to the second combustion zone. The combustor is configured to receive the flow of inlet air. A fuel split is a fraction of a total flow of fuel that is channeled to the second combustion zone. The computing device includes a digital simulation of the rotary machine and is configured to operate the rotary machine in a response mode. The computing device is configured to reduce the fuel split to zero and determine a current operating temperature of the first combustion zone using the digital simulation of the rotary machine. The computing device is also configured to determine a target operating temperature of the first combustion zone. The target operating temperature enables the rotary machine to operate below a traditional Minimum Emissions Compliance Load (MECL) while still in compliance with emissions standards. The computing device is further configured to channel a first flow of fuel to the first combustion zone. The first flow of fuel decreases the temperature of the first combustion zone to the target operating temperature. The computing device is also configured to iterate until the rotary machine is operating below the traditional MECL and complying with emission standards.

Unless otherwise indicated, approximating language, such as "generally," "substantially," and "about," as used herein indicates that the term so modified may apply to only an approximate degree, as would be recognized by one of ordinary skill in the art, rather than to an absolute or perfect degree. Accordingly, a value modified by a term or terms such as "about," "approximately," and "substantially" is not to be limited to the precise value specified. Here and throughout the specification and claims, range limitations may be identified. Such ranges may be combined and/or interchanged and include all the sub-ranges contained therein unless context or language indicates otherwise. Additionally, unless otherwise indicated, the terms "first," "second," etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, for example, a "second" item does not require or preclude the existence of, for example, a "first" or lower-numbered item or a "third" or higher-numbered item.

As used herein, the terms "axial" and "axially" refer to directions and orientations extending substantially parallel to a longitudinal axis of a rotary machine. Moreover, the terms "radial" and "radially" refer to directions and orientations extending substantially perpendicular to the longitudinal axis of the rotary machine. In addition, as used herein, the terms "circumferential" and "circumferentially" refer to directions and orientations extending arcuately about the longitudinal axis of the rotary machine. Further, as used herein, the term "upstream" refers to a forward or inlet end of a rotary machine, and the term "downstream" refers to an aft or exhaust end of the rotary machine. When discussing a flow of fluid through a component, the direction from which the fluid flows is described as "upstream," and the direction in which the fluid flows is described as "downstream.

The methods and systems described herein relate to a method for emissions compliant operation of a combustor of a gas turbine engine below a traditional MECL. More specifically, the gas turbine engine includes a combustor including a first combustion zone, a second combustion zone, at least one first fuel nozzle, and at least one second fuel nozzle. The at least one first fuel nozzle channels a first flow of fuel to the first combustion zone, and the at least one second fuel nozzle channels a second flow of fuel to the second combustion zone. A fuel split is a fraction of a total flow of fuel that is channeled to the second combustion zone. A digital simulation simultaneously determines a current operating temperature of the first combustion zone, and at least one sensor measures a current operating temperature of an exhaust of the combustor. Additionally, inlet guide vanes control a flow of air to the combustor. When the demand on the gas turbine engine is reduced (i.e., when an operator of an electrical grid requests that an operator of the gas turbine engine reduce the generation of electricity), the operator of the gas turbine engine may place the gas turbine engine in response mode and/or standby mode.

In response mode, the operator of the gas turbine engine reduces the fuel split to zero (i.e., turns off the second combustion zone) to reduce the current operating temperature of the combustor for carbon monoxide emissions compliance and controls the flow of air to the combustor with the inlet guide vanes to maintain the exhaust temperature of the gas turbine engine at or above a minimum exhaust temperature, typically the minimum exhaust temperature required for operation of a heat exchanger used to operate an associated steam turbine of the power plant. Response mode allows the gas turbine engine to continue to operate at a reduced, but non-zero, power generation level while maintaining compliance with carbon monoxide emissions requirements.

In standby mode, the operator of the gas turbine engine reduces the fuel split to zero (i.e., turns off the second combustion zone) to reduce the current operating temperature of the combustor for carbon monoxide emissions compliance and controls the flow of air to the combustor with the inlet guide vanes to maintain the exhaust temperature of the combustor below the minimum exhaust temperature for operation of the steam generation system of the power plant. Standby mode allows the gas turbine engine to continue to operate without generating power while maintaining compliance with carbon monoxide emissions requirements.

Both response mode and standby mode allow the gas turbine engine to remain in emissions compliant operation during periods of reduced demand for electricity. As such, when the demand for electricity increases and the operator of the grid requests more electrical generation, the gas turbine engines described herein will still be operational, i.e., will not require an extended start-up procedure, and will be one of the first electrical generators requested to increase generation. In some embodiments, the elimination of a start-up delay in returning such gas turbine engines to increased power production increases revenues for the operator of the gas turbine engine. Accordingly, the systems and methods described herein provide emissions compliant operation of a combustor of a gas turbine engine below the traditional MECL throughout a time period in which the demand for electricity has decreased and the operator of the grid has requested less electrical generation.

<FIG> is a schematic view of an exemplary rotary machine <NUM>, i.e., a turbomachine, and more specifically a turbine engine. In the exemplary embodiment, rotary machine <NUM> is a gas turbine engine. Alternatively, rotary machine may be any other turbine engine and/or rotary machine, including, without limitation, a gas turbofan aircraft engine, other aircraft engine. In the exemplary embodiment, gas turbine engine <NUM> includes an intake section <NUM>, a compressor section <NUM> that is coupled downstream from intake section <NUM>, a combustor section <NUM> that is coupled downstream from compressor section <NUM>, a turbine section <NUM> that is coupled downstream from combustor section <NUM>, and an exhaust section <NUM> that is coupled downstream from turbine section <NUM>. Turbine section <NUM> is coupled to compressor section <NUM> via a rotor shaft <NUM>.

It should be noted that, as used herein, the term "couple" is not limited to a direct mechanical, thermal, electrical, and/or flow communication connection between components, but may also include an indirect mechanical, thermal, electrical, and/or flow communication connection between multiple components. In the exemplary embodiment, combustor section <NUM> includes a plurality of combustors <NUM>. Combustor section <NUM> is coupled to compressor section <NUM> such that each combustor <NUM> is in flow communication with the compressor section <NUM>. Rotor shaft <NUM> is further coupled to a load <NUM> such as, but not limited to, an electrical generator and/or a mechanical drive application. In the exemplary embodiment, each of compressor section <NUM> and turbine section <NUM> includes at least one rotor assembly <NUM> that is coupled to rotor shaft <NUM>.

In this embodiment, intake section <NUM> includes at least one inlet guide vane <NUM> that is controlled by an inlet guide vane controller <NUM>. Inlet guide vanes <NUM> control a flow of inlet air <NUM> that intake section <NUM> channels from the atmosphere to compressor section <NUM>. Specifically, inlet guide vanes <NUM> may include variable or fixed airfoils <NUM> that direct inlet air <NUM> to compressor section <NUM>. Additionally, airfoils <NUM> of inlet guide vanes <NUM> may be variable, i.e., an angle of airfoils <NUM> relative to compressor section <NUM> may be changed, to vary the angle of flow of inlet air <NUM> and increase the efficiency of compressor section <NUM> during different operating conditions.

In the exemplary embodiment, combustors <NUM> include Axial Fuel Staging (AFS) technology including axial (sequential) staging of combustion in at least two zones. Specifically, one or more of combustors <NUM> is an axially staged combustor that includes a first combustion zone <NUM>, a second combustion zone <NUM>, at least one first fuel nozzle <NUM>, and at least one second fuel nozzle <NUM>. The at least one first fuel nozzle <NUM> is positioned upstream of the at least one second fuel nozzle <NUM> and channels a first flow of fuel into first combustion zone <NUM>, which is correspondingly upstream of second combustion zone <NUM>. The at least one second fuel nozzle <NUM> is positioned downstream of the at least one first fuel nozzle <NUM> and first combustion zone <NUM> and channels a second flow of fuel into second combustion zone <NUM>. First combustion zone <NUM> and second combustion zone <NUM> stage the combustion of a total flow of fuel to the combustor to control the combustion dynamics within combustors <NUM>. In the exemplary embodiment, a single first fuel nozzle <NUM> and a single second fuel nozzle <NUM> are illustrated in <FIG>. However, one or more of combustors <NUM> may include a plurality of first fuel nozzles <NUM> and/or a plurality of second fuel nozzles <NUM>.

In alternative embodiments, combustor <NUM> is a single staged combustor including a plurality of combustion zones and a plurality of nozzle arrays that channel fuel to each combustion zone within the single staged combustor. Accordingly, the nozzle arrays stage the flow of fuel to the single stage combustor. In another alternative embodiment, rotary machine <NUM> includes two turbines, a high pressure turbine (not shown) and a low pressure turbine (not shown). The high pressure turbine is positioned between a first combustor (not shown) and a second combustor (not shown), and the low pressure turbine is positioned downstream of the second combustor. The high pressure turbine recovers energy from combustion gases discharged from the first combustor, and the combustion gases are discharged to the second combustor. The second combustor mixes the combustion gases with fuel and ignites the combustion gases with the fuel. The combustion gases are then discharged from the second combustor to the low pressure turbine, and the low pressure turbine recovers energy from combustion gases discharged from the second combustor. In yet another alternative embodiment, combustor <NUM> includes more than two combustors and/or combustion zones and more than two nozzle arrays, including three or more combustors and/or combustion zones and three or more nozzle arrays.

Rotary machine <NUM> also includes a fuel supply system <NUM> including at least one valve <NUM> that controls a fuel split of the total flow of fuel. The fuel split corresponds to an apportionment of a total fuel flow to combustor <NUM> between the first flow of fuel and the second flow of fuel. In the exemplary embodiment, the fuel split is represented as the fraction of the total flow of fuel that is channeled to the at least one second fuel nozzle <NUM> (i.e., the second flow of fuel divided by the sum of the first and second flow of fuel). Alternatively, the fuel split is represented in any suitable fashion. Specifically, fuel supply system <NUM> channels the total flow of fuel to combustors <NUM>. More specifically, fuel supply system <NUM> channels the total flow of fuel to first fuel nozzle <NUM> and second fuel nozzle <NUM> which, in turn, channel the total flow of fuel to first combustion zone <NUM> and second combustion zone <NUM> respectively. Valve <NUM> is controllable to split the total flow of fuel into the first flow of fuel and the second flow of fuel according to the selected fuel split.

Rotary machine <NUM> further includes a computing device <NUM> that controls at least one operating parameter of rotary machine <NUM>. More specifically, in the exemplary embodiment, computing device <NUM> controls the fuel split of the total flow of fuel to combustors <NUM> by controlling valve <NUM>. Additionally, computing device <NUM> may also send control signals to inlet guide vane controller <NUM> and/or directly control inlet guide vanes <NUM> to control flow of inlet air <NUM> that is channeled to combustors <NUM>. Accordingly, computing device <NUM> controls the stoichiometry of the combustion reaction within combustors <NUM> by controlling both the fuel split and flow of inlet air <NUM> to combustors <NUM>.

Computing device <NUM> also is programmed to execute a digital simulation of rotary machine <NUM> that accurately determines at least one temperature within combustor <NUM>, such as a temperature that is not, and/or cannot be, directly measured with reliable accuracy. More specifically, the digital simulation accurately determines the T<NUM> and the T<NUM> temperatures within combustor <NUM>, such as in the absence of a direct temperature sensor measurement within first combustion zone <NUM> and second combustion zone <NUM>. The T<NUM> temperature is the temperature within combustor <NUM> that is within first combustion zone <NUM> and axially upstream of second fuel nozzle <NUM> and second combustion zone <NUM>. The T<NUM> temperature is the temperature within combustor <NUM> within second combustion zone <NUM> and axially downstream of second fuel nozzle <NUM>. As will be discussed in greater detail below, computing device <NUM> controls the fuel split and flow of inlet air <NUM> to combustors <NUM> to control the T<NUM> temperature using the digital simulation.

During operation, intake section <NUM> channels inlet air <NUM> towards compressor section <NUM>. Computing device <NUM> and/or inlet guide vane controller <NUM> control inlet guide vanes <NUM> to control flow of inlet air <NUM>. Compressor section <NUM> compresses inlet air <NUM> to higher pressures prior to discharging compressed air <NUM> towards combustor section <NUM>. Compressed air <NUM> is channeled to combustor section <NUM> where it is mixed with fuel (not shown) and burned to generate high temperature combustion gases <NUM>. Computing device <NUM> controls the fuel split to first fuel nozzle <NUM> and second fuel nozzle <NUM> to control the T<NUM> temperature within combustors <NUM> using the digital simulation. Combustion gases <NUM> are channeled downstream towards turbine section <NUM> and impinge upon turbine blades (not shown), converting thermal energy to mechanical rotational energy that is used to drive rotor assembly <NUM> about a longitudinal axis <NUM>. Often, combustor section <NUM> and turbine section <NUM> are referred to as a hot gas section of turbine engine <NUM>. Exhaust gases <NUM> then discharge through exhaust section <NUM> to ambient atmosphere or to a steam turbine (not shown), if the rotary machine <NUM> is a gas turbine that is part of a combined cycle power plant.

<FIG>, <FIG>, <FIG>, and <FIG> are a flow diagram of an exemplary method <NUM> of emissions compliant operation of rotary machine <NUM> below a traditional MECL. <FIG> is a graph <NUM> of a relationship between an exhaust temperature of rotary machine <NUM> and an electrical load of rotary machine <NUM>. Method <NUM> includes operating <NUM> rotary machine <NUM> in a normal operating mode, i.e., at a load above a Minimum Emissions Compliance Load (MECL) <NUM> and in which power is supplied to the electrical grid. Rotary machine <NUM> has MECL <NUM> that is the lowest load on rotary machine <NUM> in which rotary machine <NUM> can traditionally normally operate while still in compliance with emissions standards. More specifically, MECL <NUM> is the lowest load on rotary machine <NUM> in which the T<NUM> temperature is maintained at a temperature that maintains compliance with emissions standards, both first combustion zone <NUM> and second combustion zone <NUM> are operating, and exhaust gases <NUM> are maintained at or above a minimum exhaust temperature for operation of the combined cycle power plant.

Graph <NUM> includes a plurality of lines <NUM>, <NUM>, <NUM>, and <NUM> that illustrate potential paths of rotary machine <NUM> during operations. Specifically, graph <NUM> includes a historic path <NUM>, an example first response mode path <NUM>, an example second response mode path <NUM>, and an example standby mode path <NUM>. Graph <NUM> also includes a target T<NUM> temperature line <NUM> and a target exhaust temperature line <NUM>. Historic path <NUM> is the path that has historically been followed during start-up, operation, and shut-down of rotary machine <NUM>. First response mode path <NUM> and second response mode path <NUM> are examples of a response mode that enables rotary machine <NUM> to continue to operate at a reduced power generation level while maintaining compliance with carbon monoxide emissions requirements, i.e., to reach an operating point that lies on target T<NUM> temperature line <NUM>. Specifically, in response mode, the operator of rotary machine <NUM> reduces the fuel split to zero (i.e., turns off the second combustion zone <NUM>) and controls the flow of air to combustor <NUM> with inlet guide vanes <NUM> to reduce the T<NUM> temperature of first combustion zone <NUM> and combustor <NUM>, e.g., along one of first response mode path <NUM> and second response mode path <NUM> for carbon monoxide emissions compliance, and to maintain exhaust gases <NUM> at or above target exhaust temperature line <NUM>. i.e., the minimum exhaust temperature for operation of the power plant at a reduced, but non-zero, load. Standby mode path <NUM> allows rotary machine <NUM> to continue to operate without generating power while maintaining compliance with carbon monoxide emissions requirements. Specifically, in standby mode, the operator of rotary machine <NUM> reduces the fuel split to zero (i.e., turns off the second combustion zone) and controls the flow of air to the combustor with inlet guide vanes <NUM> to reduce the T<NUM> temperature of first combustion zone <NUM> and combustor <NUM> for carbon monoxide emissions compliance, i.e., to reach an operating point that lies on target T<NUM> temperature line <NUM>, and to maintain exhaust gases <NUM> below target exhaust temperature line <NUM>, the minimum exhaust temperature for operation of the power plant. Both response mode and standby mode allow rotary machine <NUM> to remain in emissions compliant operation during periods of reduced demand for electricity. As such, when the demand for electricity increases and the operator of the grid requests more electrical generation, rotary machines <NUM> described herein will still be operational and will be one of the first electrical generators requested to increase generation, increasing revenues for the operator of rotary machine <NUM>. Accordingly, the systems and methods described herein provide emissions compliant operation of a combustor of rotary machine <NUM> below MECL <NUM> when the demand for electricity decreases and the operator of the grid requests less electrical generation.

Method <NUM> also includes receiving <NUM> a request to reduce generation of electricity below MECL <NUM>. In the exemplary embodiment, a controller of the electrical grid determines that excess electricity is being generated and requests that one or more generators reduce generation of electrical power. In alternative embodiment, rather than receiving a request to reduce generation of electricity, rotary machine <NUM> may be required to reduce generation of electricity for other reasons such as, without limitation, emergencies and/or maintenance requirements associated with rotary machine <NUM>, the combined cycle power station, and/or the electrical grid.

Method <NUM> further includes reducing <NUM> the fuel split to zero. The operator of rotary machine <NUM> reduces the fuel split to zero to stop combustion within second combustion zone <NUM>. First fuel nozzle <NUM> continues to channel the first flow of fuel to into first combustion zone <NUM> while second fuel nozzle <NUM> stops channeling the second flow of fuel to into second combustion zone <NUM>. More specifically, computing device <NUM> controls valve <NUM> to reduce the second flow of fuel to zero while maintaining the first flow of fuel. As such, first combustion zone <NUM> is the only combustion zone in operation and the total flow of fuel is not staged to control the combustion dynamics within combustors <NUM>. In an alternative embodiment, the first flow of fuel to into first combustion zone <NUM> is also reduced to control the T<NUM> temperature.

Method <NUM> also includes operating <NUM> rotary machine <NUM> in a response mode, such as first response mode <NUM> and/or second response mode <NUM>. In response mode, the operator of rotary machine <NUM> reduces the fuel split to zero (i.e., turns off the second combustion zone) and controls the flow of air to combustor <NUM> with inlet guide vanes <NUM> to reduce the T<NUM> temperature of first combustion zone <NUM> and combustor <NUM> for carbon monoxide emissions compliance, and to maintain exhaust gases <NUM> at or above a minimum exhaust temperature for operation of the power plant. Rotary machine <NUM> then begins to operate along, for example, first response mode path <NUM> illustrated in graph <NUM>. As shown in graph <NUM>, first response mode path <NUM> deviates from historic path <NUM> because second combustion zone <NUM> is turned off and the combustor temperature is controlled by manipulation of combustor inlet airflow. More specifically, the exhaust temperature and the T<NUM> temperature are reduced because second combustion zone <NUM> is turned off and the T<NUM> temperature is controlled using Inlet Guide Vanes. As such, the load, the exhaust temperature, and T<NUM> temperature are simultaneously reduced along first response mode path <NUM> that is different from historic path <NUM>.

Operating <NUM> rotary machine <NUM> in the response mode includes determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> using the digital simulation of rotary machine <NUM>. The digital simulation is a model of rotary machine <NUM>. Specifically, the digital simulation is any suitable model that accurately determines the operating state of a plurality of operating parameters within rotary machine <NUM> in real time during operation of rotary machine <NUM> based on control inputs to computing device <NUM> and/or feedback from suitable sensors (not shown) positioned throughout rotary machine <NUM>. More specifically, the digital simulation is a thermodynamic and fluid dynamic model that accurately determines the operating state of the plurality of operating parameters within rotary machine <NUM> in real time during operation of rotary machine <NUM>. The plurality of operating parameters that the digital simulation determines includes, among many other parameters, the T<NUM> and the T<NUM> temperatures within combustor <NUM>, which typically cannot be directly measured by sensors within the combustion zones. Accordingly, the digital simulation determines the T<NUM> and the T<NUM> temperatures within combustor <NUM> in real time during operation of rotary machine <NUM>. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously. In alternative embodiments, determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> may include determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> using a non-physics based model of rotary machine <NUM> such as a state variable model or a neural network.

Operating <NUM> rotary machine <NUM> in the response mode includes determining <NUM> a target operating T<NUM> temperature. In the exemplary embodiment, determining <NUM> the target operating T<NUM> temperature includes determining <NUM> the target operating T<NUM> temperature using the digital simulation. The digital simulation may determine the target operating T<NUM> temperature on an iterative basis, simultaneously with determining <NUM> the actual temperature of first combustion zone <NUM>, using the digital simulation of rotary machine <NUM>. More specifically, the target operating T<NUM> temperature is determined based on emissions standards to ensure that rotary machine <NUM> operates in compliance with emissions standards. For example, conditions may change (i.e., the operator of the grid requests that rotary machine <NUM> increase power generation to a level below MECL <NUM>, the ambient temperature, pressure, and/or humidity may change, and/or the fuel temperature may change) that require updating of the target operating T<NUM> temperature in order for rotary machine <NUM> to meet load and emissions requirements. For example, the requirements on load <NUM> may increase or decrease, and, as such, the operating conditions of rotary machine <NUM> may change to accommodate the changing requirements on load <NUM>. Specifically, to accommodate the changing requirements on load <NUM>, the target T<NUM> operating temperature may change. However, in alternative embodiments, the target operating T<NUM> temperature may be determined by an operator or by some other method, rather than by the digital simulation, and/or may not be updated iteratively with every control cycle. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the response mode includes determining <NUM> a current temperature of exhaust gases <NUM> using at least one sensor (not shown) configured to measure the current operating temperature of exhaust gases <NUM>. The sensor determines the current temperature of exhaust gases <NUM> in real time during operation of rotary machine <NUM>. Additionally, the temperature of exhaust gases <NUM> may be sent to the digital simulation and used as an input into determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> and/or determining <NUM> the target operating T<NUM> temperature. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the response mode includes determining <NUM> a target temperature of exhaust gases <NUM>. In the exemplary embodiment, determining <NUM> the target temperature of exhaust gases <NUM> includes determining <NUM> the target operating T<NUM> temperature using the digital simulation and/or computing device <NUM>. The digital simulation and/or computing device <NUM> may determine the target temperature of exhaust gases <NUM> on an iterative basis, simultaneously with determining <NUM> the current temperature of exhaust gases <NUM>, using the digital simulation and/or computing device <NUM> of rotary machine <NUM>. More specifically, the target temperature of exhaust gases <NUM> is determined based on the minimum exhaust temperature for operation of the power plant. For example, conditions may change (i.e., the operator of the grid requests that rotary machine <NUM> increase power generation to a level below MECL <NUM>) that require updating of the target temperature of exhaust gases <NUM> in order for rotary machine <NUM> to meet load requirements. For example, the requirements on load <NUM> may increase or decrease, and, as such, the operating conditions of rotary machine <NUM> may change to accommodate the changing requirements on load <NUM>. Specifically, to accommodate the changing requirements on load <NUM>, the temperature of exhaust gases <NUM> may change. However, in alternative embodiments, the target temperature of exhaust gases <NUM> may be determined by an operator or by some other method (such as a plant controller separate from a rotary machine controller), rather than by the digital simulation and/or computing device <NUM>, and/or may not be updated iteratively with every control cycle. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the response mode further includes comparing <NUM> the current operating T<NUM> temperature and the target operating T<NUM> temperature. If the current operating T<NUM> temperature and the target operating T<NUM> temperature are different, computing device <NUM> controls the first flow of fuel and flow of inlet air <NUM> to change the current operating T<NUM> temperature to the target operating T<NUM> temperature as described below. Comparing <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the response mode further includes comparing <NUM> the current temperature of exhaust gases <NUM> and the target temperature of exhaust gases <NUM>. If the current temperature of exhaust gases <NUM> and the target temperature of exhaust gases <NUM> are different, computing device <NUM> controls the first flow of fuel and flow of inlet air <NUM> to change the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> as described below. Comparing <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the response mode further includes calculating <NUM> a target first flow of fuel that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> using the digital simulation and/or computing device <NUM>. In the exemplary embodiment, the digital simulation and/or computing device <NUM> may calculate the target first flow of fuel that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> by running an additional digital simulation of rotary machine <NUM>.

Operating <NUM> rotary machine <NUM> in the response mode further includes calculating <NUM> a target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> using the digital simulation and/or computing device <NUM>. In the exemplary embodiment, the digital simulation may calculate the target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> by running an additional digital simulation of rotary machine <NUM>. Alternatively, computing device may calculate the target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM>.

Operating <NUM> rotary machine <NUM> in the response mode further includes controlling <NUM> the first flow of fuel and flow of inlet air <NUM> to change the current operating T<NUM> temperature to the target operating T<NUM> temperature and the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM>. Specifically, computing device <NUM> controls valve <NUM> to control the first flow of fuel and inlet guide vanes <NUM> to control flow of inlet air <NUM>. Computing device <NUM> controls valve <NUM> to adjust the first flow of fuel to the target first flow of fuel, and controls control inlet guide vanes <NUM> to adjust flow of inlet air <NUM> to the target flow of inlet air <NUM>. Computing device <NUM> and the digital simulation control flow of inlet air <NUM> and the first flow of fuel to first combustion zone <NUM> to control the stoichiometry of first combustion zone <NUM>. After the current operating T<NUM> temperature has been changed to the target operating T<NUM> temperature and the current temperature of exhaust gases <NUM> has been changed to the target temperature of exhaust gases <NUM>, the operating state of rotary machine <NUM> changes and the digital simulation and/or computing device <NUM> iterates method <NUM> as necessary in order to maintain compliance with emissions requirements and maintain the temperature of exhaust gases <NUM> at or above the minimum exhaust temperature for operation of the power plant.

As shown in graph <NUM>, an example second response mode path <NUM> extends from first response mode path <NUM> and may be used, for example, when a temperature of flow of inlet air <NUM> is relatively high. More specifically, when the temperature of flow of inlet air <NUM> is above <NUM> °F (<NUM>,<NUM>) for example, second response mode path <NUM> may be followed by controlling for a target burner tube velocity for first fuel nozzle <NUM>. For example, the target burner tube velocity is the burner tube velocity above which a flame from first fuel nozzle <NUM> is pushed out into first combustion zone <NUM> to avoid flashback or auto-ignition.

Method <NUM> also includes operating <NUM> rotary machine <NUM> in a standby mode. In standby mode, the operator of rotary machine <NUM> reduces the fuel split to zero (i.e., turns off the second combustion zone) and controls the flow of air to combustor <NUM> with inlet guide vanes <NUM> to reduce the T<NUM> temperature of first combustion zone <NUM> and combustor <NUM> for carbon monoxide emissions compliance, and to maintain exhaust gases <NUM> below the minimum exhaust temperature for operation of the power plant, e.g., for operation of a heat exchanger used to generate steam for a steam turbine from the residual heat in exhaust gases <NUM>. The operator operates rotary machine <NUM> in standby mode rather than response mode because the operator of the grid has requested that the operator reduce generation of electricity below the power generation of response mode. In some embodiments, rotary machine <NUM> is operating in response mode first, and then in response to a subsequent request from the grid operator for reduced generation, further reduces power generation by operating in standby mode. Rotary machine <NUM> then begins to operate along, for example, standby mode path <NUM> illustrated in graph <NUM>. As shown in graph <NUM>, standby mode path <NUM> deviates from historic path <NUM> because second combustion zone <NUM> is turned off and the combustor temperature is controlled by manipulation of combustor inlet airflow. More specifically, the exhaust temperature and the T<NUM> temperature are reduced because second combustion zone <NUM> is turned off and the T3. <NUM> temperature is controlled using inlet guide vanes <NUM>. As such, the load, the exhaust temperature, and T<NUM> temperature are simultaneously reduced along standby mode path <NUM> that is different from historic path <NUM>.

Operating <NUM> rotary machine <NUM> in the standby mode includes determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> using the digital simulation of rotary machine <NUM> as described in determining <NUM> above. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode includes determining <NUM> a target operating T<NUM> temperature. In the exemplary embodiment, determining <NUM> the target operating T<NUM> temperature includes determining <NUM> the target operating T<NUM> temperature using the digital simulation. The digital simulation may determine the target operating T<NUM> temperature on an iterative basis, simultaneously with determining <NUM> the temperature of first combustion zone <NUM>, using the digital simulation of rotary machine <NUM>. More specifically, the target operating T<NUM> temperature is determined based on emissions standards to ensure that rotary machine <NUM> operates in compliance with emissions standards. For example, conditions may change (i.e., the operator of the grid requests that rotary machine <NUM> increase power generation to a level below MECL <NUM>) that require updating of the target operating T<NUM> temperature in order for rotary machine <NUM> to meet load and emissions requirements. For example, the requirements on load <NUM> may increase or decrease, and, as such, the operating conditions of rotary machine <NUM> may change to accommodate the changing requirements on load <NUM>. Specifically, to accommodate the changing requirements on load <NUM>, the target T<NUM> operating temperature may change. However, in alternative embodiments, the target operating T<NUM> temperature may be determined by an operator or by some other method, rather than by the digital simulation, and/or may not be updated iteratively with every control cycle. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode includes determining <NUM> a current temperature of exhaust gases <NUM> using at least one sensor (not shown) configured to measure the current operating temperature of exhaust gases <NUM>. The sensor determines the current temperature of exhaust gases <NUM> in real time during operation of rotary machine <NUM>. Additionally, the temperature of exhaust gases <NUM> may be sent to the digital simulation and used as an input into determining <NUM> the current operating T<NUM> temperature of first combustion zone <NUM> and/or determining <NUM> the target operating T<NUM> temperature. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode includes determining <NUM> a target temperature of exhaust gases <NUM>. In the exemplary embodiment, determining <NUM> the target temperature of exhaust gases <NUM> includes determining <NUM> the target operating T<NUM> temperature using the digital simulation and/or computing device <NUM>. The digital simulation and/or computing device <NUM> may determine the target temperature of exhaust gases <NUM> on an iterative basis, simultaneously with determining <NUM> the current temperature of exhaust gases <NUM>, using the digital simulation and/or computing device <NUM> of rotary machine <NUM>. More specifically, the target temperature of exhaust gases <NUM> is determined based on the physical operating limits of rotary machine <NUM> and the best heat rate. Determining <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode further includes comparing <NUM> the current operating T<NUM> temperature and the target operating T<NUM> temperature. If the current operating T<NUM> temperature and the target operating T<NUM> temperature are different, computing device <NUM> controls the first flow of fuel and flow of inlet air <NUM> to change the current operating T<NUM> temperature to the target operating T<NUM> temperature as described below. Comparing <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode further includes comparing <NUM> the current temperature of exhaust gases <NUM> and the target temperature of exhaust gases <NUM>. If the current temperature of exhaust gases <NUM> and the target temperature of exhaust gases <NUM> are different, computing device <NUM> controls the first flow of fuel and flow of inlet air <NUM> to change the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> as described below. Comparing <NUM> may occur continuously while other steps of method <NUM> are occurring simultaneously.

Operating <NUM> rotary machine <NUM> in the standby mode further includes calculating <NUM> a target first flow of fuel that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> using the digital simulation and/or computing device <NUM>. In the exemplary embodiment, the digital simulation may calculate the target first flow of fuel that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> by running an additional digital simulation of rotary machine <NUM>. Alternatively, computing device may calculate the target first flow of fuel that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM>.

Operating <NUM> rotary machine <NUM> in the standby mode further includes calculating <NUM> a target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> using the digital simulation and/or computing device <NUM>. In the exemplary embodiment, the digital simulation may calculate the target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM> by running an additional digital simulation of rotary machine <NUM>. Alternatively, computing device may calculate the target flow of inlet air <NUM> that changes the current operating T<NUM> temperature to the target operating T<NUM> temperature and that changes the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM>.

Operating <NUM> rotary machine <NUM> in the standby mode further includes controlling <NUM> the first flow of fuel and flow of inlet air <NUM> to change the current operating T<NUM> temperature to the target operating T<NUM> temperature and the current temperature of exhaust gases <NUM> to the target temperature of exhaust gases <NUM>. Specifically, computing device <NUM> controls valve <NUM> to control the first flow of fuel and inlet guide vanes <NUM> to control flow of inlet air <NUM>. Computing device <NUM> controls valve <NUM> to adjust the first flow of fuel to the target first flow of fuel, and controls control inlet guide vanes <NUM> to adjust flow of inlet air <NUM> to the target flow of inlet air <NUM>. Computing device <NUM> and digital simulation control flow of inlet air <NUM> and the first flow of fuel to first combustion zone <NUM> to control the stoichiometry of first combustion zone <NUM>. After the current operating T<NUM> temperature has been changed to the target operating T<NUM> temperature and the current temperature of exhaust gases <NUM> has been changed to the target temperature of exhaust gases <NUM>, the operating state of rotary machine <NUM> changes and the digital simulation and/or computing device <NUM> iterates method <NUM> as necessary in order to maintain compliance with emissions requirements and maintain the temperature of exhaust gases <NUM> below the minimum exhaust temperature for operation of the power plant.

Method <NUM> also includes receiving <NUM>, while operating in the response mode or the standby mode, a request to increase generation of electricity above MECL <NUM>. In the exemplary embodiment, a controller of the electrical grid determines that too little electricity is being generated and requests that one or more generators increase generation of electrical power. In alternative embodiment, rather than receiving a request to increase generation of electricity, rotary machine <NUM> may be required to increase generation of electricity for other reasons such as, without limitation, emergencies and/or maintenance requirements associated with rotary machine <NUM>, the combined cycle power station, and/or the electrical grid.

Method <NUM> further includes increasing <NUM> the fuel split from zero to a level consistent with normal operations. The operator of rotary machine <NUM> increases the fuel split and reignites combustion within second combustion zone <NUM>. First fuel nozzle <NUM> and second fuel nozzle <NUM> channel the first and second flows of fuel into first combustion zone <NUM> and second combustion zone <NUM>, respectively. More specifically, computing device <NUM> controls valve <NUM> to increase the second flow of fuel while maintaining the first flow of fuel. As such, first combustion zone <NUM> and second combustion zone <NUM> are both operating and the total flow of fuel is staged to control the combustion dynamics within combustors <NUM>. In an alternative embodiment, the first flow of fuel into first combustion zone <NUM> is also increased to control the T<NUM> temperature.

Method <NUM> also includes operating <NUM> rotary machine <NUM> in a normal operating mode, such as in response to the request to increase generation of electricity. In the normal operating mode, the operator of rotary machine <NUM> increases the fuel split to maintain the T<NUM> temperature in compliance with emissions requirements and controls the flow of air to combustor <NUM> with inlet guide vanes <NUM> to maintain exhaust gases <NUM> at or above a minimum exhaust temperature for operation of the power plant. Rotary machine <NUM> then begins to operate along historic path <NUM> illustrated in graph <NUM>.

Method <NUM> may be implemented with rotary machines <NUM> with alternative combustor <NUM> arrangements. For example, method <NUM> may be implemented with combustors <NUM> including a single staged combustor including a plurality of nozzle arrays as described above. Additionally, method <NUM> may be implemented with rotary machine <NUM> including a high pressure turbine positioned between a first combustor and a second combustor, and a low pressure turbine positioned downstream of the second combustor as described above. Moreover, method <NUM> may be implemented with any combustor <NUM> arrangement that enables rotary machine <NUM> operate as described herein.

The above described systems and methods relate to a method for emissions compliant operation of a combustor of a gas turbine engine below a traditional MECL. More specifically, the gas turbine engine includes a combustor including a first combustion zone, a second combustion zone, at least one first fuel nozzle, and at least one second fuel nozzle. The at least one first fuel nozzle channels a first flow of fuel to the first combustion zone, and the at least one second fuel nozzle channels a second flow of fuel to the second combustion zone. A fuel split is a fraction of a total flow of fuel that is channeled to the second combustion zone. A digital simulation simultaneously determines a current operating temperature of the first combustion zone, and at least one sensor measures a current operating temperature of an exhaust of the gas turbine. Additionally, inlet guide vanes control a flow of air to the combustor. When the demand on the gas turbine engine is reduced (i.e., when an operator of an electrical grid requests that an operator of the gas turbine engine reduce the generation of electricity), the operator of the gas turbine engine may place the gas turbine engine in response mode and/or standby mode.

In response mode, the operator of the gas turbine engine reduces the fuel split to zero (i.e., turns off the second combustion zone) and controls the flow of air to the combustor with the inlet guide vanes to reduce the current operating temperature of the combustor for carbon monoxide emissions compliance and to maintain the exhaust temperature of the combustor at or above a minimum exhaust temperature for operation of a steam generation system of the power plant. Response mode allows the gas turbine engine to continue to operate at a reduced power generation level by the combined cycle power plant, while maintaining compliance with carbon monoxide emissions requirements.

In standby mode, the operator of the gas turbine engine reduces the fuel split to zero (i.e., turns off the second combustion zone) and controls the flow of air to the combustor with the inlet guide vanes to reduce the current operating temperature of the combustor for carbon monoxide emissions compliance, and to maintain the exhaust temperature of the combustor below the minimum exhaust temperature for operation of the steam generation system of the power plant. Standby mode allows the gas turbine engine to continue to operate without the combined cycle power plant generating power, while maintaining compliance with carbon monoxide emissions requirements.

Both response mode and standby mode allow the gas turbine engine to remain in emissions compliant operation during periods of reduced demand for electricity. As such, when the demand for electricity increases and the operator of the grid requests more electrical generation, the gas turbine engines described herein will still be operational and will be one of the first electrical generators requested to increase generation, increasing revenues for the operator of the gas turbine engine. Accordingly, the systems and methods described herein provide emissions compliant operation of a combustor of a gas turbine engine below the traditional MECL when the demand for electricity decreases and the operator of the grid requests less electrical generation.

Additionally, an exemplary technical effect of the systems and methods described herein includes at least one of: (a) controlling a temperature of a first combustion zone of a combustor; (b) controlling an electrical load generated by a gas turbine engine; and (c) controlling a flow of air to a compressor and a combustor.

Exemplary embodiments of systems and methods for emissions compliant operation of a combustor of a gas turbine engine below a traditional MECL are described above in detail. The methods and systems are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the method may also be used in combination with other rotary machines, and are not limited to practice only with the gas turbine engines as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other rotary machine applications.

Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in others, this is for convenience only.

Claim 1:
A method (<NUM>) of operating a rotary machine (<NUM>) below a traditional minimum emissions compliance load (<NUM>) in a response mode (<NUM>), the rotary machine (<NUM>) including a combustor (<NUM>) including a first combustion zone (<NUM>) and a second combustion zone (<NUM>), said method (<NUM>) comprising:
i) reducing (<NUM>) a fuel split to zero, wherein the fuel split apportions a total flow of fuel to the combustor (<NUM>) between the first combustion zone (<NUM>) and the second combustion zone (<NUM>);
ii) determining (<NUM>) a current operating temperature of the first combustion zone (<NUM>) using a digital simulation of the rotary machine (<NUM>);
iii) determining (<NUM>) a target operating temperature of the first combustion zone (<NUM>), wherein the target operating temperature enables the rotary machine (<NUM>) to operate below the traditional Minimum emissions compliance load (MECL) (<NUM>) while still in compliance with emissions standards;
iv) channeling a first flow of fuel to the first combustion zone (<NUM>), wherein the first flow of fuel decreases the temperature of the first combustion zone (<NUM>) to the target operating temperature; and
v) iterating steps i through iv until the rotary machine (<NUM>) is operating below the traditional MECL (<NUM>) and complying with emission standards.