Abstract: Systems and methods for controlling a gas turbine are disclosed. The gas turbine can include a compressor oversized in airflow capacity and one or variable blade rows to control the airflow into the compressor. The position of the variable blade rows can be controlled according to a nominal variable blade row schedule that is defined to throttle down the variable blade rows to provide nominal flow into the compressor. The positions of the variable blade rows can be adjusted from the nominal positions set forth in the variable blade row schedule pursuant to a request to operate the gas turbine system in either a controlled output mode or in a frequency compensation mode.

Abstract: A power generation system (100) and a method of generating power. In one embodiment of the system shown in FIG. 1, a gasification subsystem (1) is configured to convert a carbonaceous fuel to fuel suitable for combustion in a gas turbine (48). A first power generation cycle (2) includes the gas turbine (48) coupled to receive fuel from a gasifier (24). A first Rankine cycle (3) is coupled to receive thermal energy from at least the first power generation cycle (2) and generate power with a first vapor turbine (58). A second Rankine cycle (4) is coupled to receive thermal energy from the gasification subsystem (1) or the first power generation cycle (2) and generate power with a second vapor turbine (82). In an associated method, syngas (26) is generated and processed to remove components therein. Power is generated in a first turbine (48) with the processed syngas (33). Power is generated in a second turbine (58) with heat recovered from exhaust produced by the first turbine (48).

Abstract: Various technologies pertaining to tuning composition of a fluid mixture in a supercritical Brayton cycle power generation system are described herein. Compounds, such as Alkanes, are selectively added or removed from an operating fluid of the supercritical Brayton cycle power generation system to cause the critical temperature of the fluid to move up or down, depending upon environmental conditions. As efficiency of the supercritical Brayton cycle power generation system is substantially optimized when heat is rejected near the critical temperature of the fluid, dynamically modifying the critical temperature of the fluid based upon sensed environmental conditions improves efficiency of such a system.

Abstract: Gas turbine, software and method for controlling an operating point of the gas turbine that includes a compressor, a combustor and at least a turbine is provided. The method includes determining a turbine exhaust pressure at an exhaust of the turbine; measuring a compressor pressure discharge at the compressor; determining a turbine pressure ratio based on the turbine exhaust pressure and the compressor pressure discharge; calculating an exhaust temperature at the exhaust of the turbine as a function of the turbine pressure ratio; identifying a reference exhaust temperature curve in a plane defined by the exhaust temperature and the turbine pressure ratio; and controlling the gas turbine to maintain the operating point on the reference exhaust temperature curve.

Abstract: Methods and apparatus are provided for selectively controlling the rotational speed of a gas turbine engine that drives a load compressor having movable inlet guide vanes and that is coupled to receive fuel at a fuel flow rate up to a maximum fuel flow rate. The rotational speed of the gas turbine engine, and the fuel flow rate to the gas turbine engine, are both sensed. If the sensed rotational speed of the gas turbine engine is less than a predetermined value and the sensed fuel flow rate to the gas turbine engine equals or exceeds the maximum fuel flow rate, the position of the inlet guide vanes is controlled to reduce load compressor mechanical load on the gas turbine engine.

Abstract: A gas turbine engine comprises a high spool, a low spool and an intermediate spool. The high spool comprises a high pressure turbine coupled to a high pressure compressor. The intermediate spool comprises an intermediate pressure turbine coupled to a ducted fan. The low spool comprises a low pressure turbine coupled to an open-rotor propeller. A variable area turbine section positioned between the intermediate pressure turbine and the low pressure turbine variable turbine section is configured to vary an expansion ratio across the intermediate pressure turbine to control rotational speeds of the low spool and the intermediate spool.

Abstract: A twin-shaft gas turbine, which has a gas generator including a compressor, a combustor, and a high-pressure turbine, is configured to make a first control mode and a second control mode selectively useable for control of the gas generator. In addition, in the first control mode, an IGV angle in the compressor is controlled in accordance with a corrected shaft rotation speed of the gas generator, and in the second control mode, the IGV angle is controlled to maintain a constant gas generator shaft rotation speed. Furthermore, the first control mode is used to start, to stop, and to operate the turbine under fixed or lower load conditions, and that the second control mode is used under operational states other than those to which the first control mode is applied.

Abstract: Apparatus for reducing air mass flow through the compressor in a single shaft gas turbine engine having an extended operating range including part load conditions, to provide low emissions combustion. The apparatus includes one or more nozzles positioned for injecting compressed air into the inlet region of the compressor. The nozzles are oriented to direct the compressed air tangentially to, and in the same angular direction as, the direction of rotation to create a swirl in the inlet air flow to the compressor inducer. The apparatus also includes conduits in flow communication between the compressor diffuser and the nozzles, one or more valves operatively connected to control the flow of compressed air from the diffuser to the nozzles, and a controller operatively connected to the valves to cause compressed air flow to the nozzles during operation at part load conditions.

Abstract: A gas turbine engine control system comprises a data acquisition and analysis system for receiving a signal from a combustion dynamics sensor and providing an output signal and a combustion dynamics control system for controlling combustion dynamics based on the output signal. The control system is associated with a purge-air flow and comprises an acoustic driver, or a flow-manipulating device, or both to perturb the purge-air flow entering the combustor can for controlling combustion dynamics.

Abstract: A method for assembling a gas turbine engine to prevent rotor over-speeding is described. The method includes serially coupling a first fuel system interface to a second fuel system interface, such that at least one of the first fuel system interface and the second fuel system interface is coupled to the gas turbine engine. The method also includes coupling a control system to the first fuel system interface and to the second fuel system interface. The control system is configured to identify an occurrence of an over-speed condition. The method also includes programming the control system to discontinue fuel flow to the engine when both the first fuel system interface and the second fuel system interface indicate an over-speed condition has occurred.

Abstract: The present application and the resultant patent provide a gas turbine engine. The gas turbine engine may include a compressor for compressing a flow of air, a combustor for combusting the flow of air and a flow of fuel to create a flow of combustion gases, a turbine driven by the flow of combustion gases, a rotor driven by the turbine and driving the compressor, a rotor speed sensor, and a gas turbine shut down controller. The gas turbine shut down controller varies the flow of fuel to the combustor based upon a rotational speed of the rotor as determined by a dynamic target trajectory schedule.

Abstract: Gas turbine and method for controlling an operating point of the gas turbine that includes a compressor, a combustor and at least a turbine. The method includes calculating an exhaust temperature reference curve of the turbine as a function of a turbine pressure ratio; determining whether condition IGVmin+?IGV1?IGVset point?IGVmax+?IGV2, and condition ttx?ttxh+?ttx3, are true; and changing, if both conditions are true, a split fuel quantity from a first value to a second value or otherwise maintaining the first value, the first value characterizing a lean-lean steady state mode and the second value characterizing a premixed secondary mode of a premixed mode.

Abstract: A method can protect a gas turbine engine (10), which includes a compressor (11), a combustor (13), and a turbine (12), against high dynamical process values, especially in combustor/flame pulsations. Effective protection against high dynamical process values, especially in combustor/flame pulsations, can be achieved by: a) measuring the pulsations of the combustor (13) with a suitable sensor (18), b) dividing the frequency spectrum of the measured pulsation signal up into pre-defined band pass sections, c) computing the rms (root mean square) of the signal for each band, d) weighting the computed frequency/frequency band rms with predetermined weighting factors, e) cumulating the weighted frequency/frequency band rms values to get a Pulsation Limit Criterion (PLC) value, f) comparing the PLC value with at least one reference value (23), and g) operating the gas turbine engine (10) according to the result of the comparison.

Abstract: In order to regulate a power plant (105) having a gas generator (1) and a free turbine (3) to drive a rotary wing, a first speed of rotation (NTL) of the free turbine (3) is regulated on a first setpoint value (NTL*) equal either to a regulation term (NRc) or to a predetermined setpoint threshold (NTL*). The regulation term (NRc) is a function of a third speed of rotation (NR) of said rotary wing in accordance, where NRc=NR*(1?d), “d” representing a non-zero constant lying in the range 0 to 1.

Abstract: A method of stabilizing combustion in a gas turbine engine includes the steps of observing a combustor flame from a location upstream from said flame to detect spectral characteristics indicative of a condition affecting combustion stability, and tuning the engine to stabilize combustion based upon an indicated condition affecting combustion stability.

Abstract: A controller for a turbine power plant that is operable to identify a failure condition and measure a shutoff valve performance.

Abstract: In a method of operating a gas turbine during shut down, the gas turbine is decelerated and closure of compressor inlet guide vanes (1) is initiated at a shaft speed at least 5% above the shaft speed where a vibration peak occurs. The compressor inlet guide vanes (1) are closed by an angle in the range from 15°-35°, preferably at a rate between 5° and 10° per second. The method effects a reduction of the risk of rotational stall.

Abstract: A system and method to reduce the gas fuel supply pressure requirements of a gas turbine, which results in an increased operability range and a reduction in gas turbine trips. According to the method, the gas turbine is allowed to start and operate at supply pressures determined as a function of ambient conditions and gas turbine compressor pressure ratio. This increases the operability window, and reduces or eliminates the need for gas fuel compressors.

Abstract: The present application and the resultant patent provide a combustor for mixing a flow of air and a flow of fuel. The combustor may include an air path for the flow of air, a number of fuel injectors positioned in the air path for the flow of fuel, and a crossfire tube positioned within the air path upstream of the fuel injectors. The crossfire tube may include a number of purge holes positioned on a downstream side thereof to reduce a wake in the flow of air caused by the crossfire tube in the air path.

Abstract: A method of actively controlling pattern factor in a gas turbine engine includes the steps of issuing fuel into a combustion chamber of a gas turbine engine through one or more circumferentially disposed fuel injectors, determining an initial circumferential pattern factor in the combustion chamber, and adjusting fuel flow through one or more selected fuel injectors based on the initial circumferential pattern factor, to yield a modified circumferential pattern factor in the combustion chamber. The step of determining the circumferential pattern factor can include the steps of detecting a chemiluminescent signature within the combustor, correlating the chemiluminescent signature to an equivalence ratio, and computing the initial circumferential pattern factor based on the equivalence ratio.

Abstract: Compensation is provided for a fuel demand signal of a gas turbine controller during transition between operating modes. The compensation adjusts fuel demand to account for combustion efficiency differences between the starting and ending operating mode that otherwise can lead to severe swings in combustion reference temperature and lean blowout.

Abstract: A gas turbine engine including an electrical assembly operable as at least one of an electric motor and a generator, with an electromagnetic rotor formed in part by a portion of one of a main shaft concentrically and drivingly connected to at least one turbine rotor and a tower shaft directly driven by the main shaft and extending generally radially therefrom.

Abstract: A fuel flow system for a gas turbine engine includes a first pump, a second pump, a bypass loop, an integrating bypass valve and a pilot valve. The first pump connects to an actuator and a metering valve. The second pump connects to the metering valve and is arranged in parallel with the first pump. The bypass loop recycles fuel flow from the first pump and the second pump to inlets of the first pump and second pump integrating bypass valve includes first and second windows. The first window regulates fuel from the first pump through the bypass loop and the second window that regulates fuel from the second pump through the bypass loop. The pilot valve controls the size of the first and second windows.

Abstract: A method for ground control of proper operation of an aeronautical turbine engine for a plane. A test includes carrying out, on the operating turbine engine and from a predetermined speed, a quick reduction in fuel flow according to a programmed decrease to evaluate flame-out resistance of the combustion chamber of the turbine engine during a quick inflight deceleration maneuver of the speed thereof.

Abstract: The present invention relates to a load control device for an engine and to a method for controlling the load. The load control device comprises a compressor for compressing air in an intake system of the engine; an exhaust gas line for discharging an exhaust gas mass flow from the engine; a turbine that is driven by an exhaust gas mass flow supplied by the exhaust gas line and that drives the compressor; a bypass line that branches off the exhaust gas line upstream of the turbine, wherein a first valve is disposed in the bypass line for controlling the mass flow in the bypass line; and an active cooling device that is disposed upstream of the valve.

Abstract: Control systems and a method for controlling a load point of a gas turbine engine are provided. A control system includes a controller that receives a temperature signal and a pressure signal associated with exhaust gases from the gas turbine engine. The controller is further configured to generate the fuel control signal. The controller is further configured to generate an actuator control signal such that flow restriction member is moved from the first operational position to the second operational position to restrict the flow path such that the exhaust gases have a temperature level within a desired turndown temperature range, the pressure level in the exhaust gases is less than a threshold pressure level, and the load point of the gas turbine engine is adjusted to toward a target load point.

Abstract: A method for assembling a gas turbine engine is described. The method includes coupling a first fuel system interface (FSI-1) to a second fuel system interface (FSI-2), and coupling one of the FSI-1 and the FSI-2 to the engine. The method includes coupling a first control system and a second control system to the FSI-1 and to the FSI-2. The first control system includes a first driver A and a second driver A, and the second control system includes a first driver B and a second driver B. The method includes configuring the first control system and the second control system to apply a first over-speed logic algorithm and a second over-speed logic algorithm to determine operation of the first driver A, the second driver A, the first driver B, and the second driver B.

Abstract: A method for operating a gas turbine includes supplying fuel via at least one control valve regulated using an open-loop control system based on a predetermined load setpoint value. A valve stroke control command (scmd) is generated based on a fuel mass flow control command (mcmd) using a mass flow-valve stroke converter. The valve stroke control command (scmd) is compared with a valve stroke limit value (min{slim1, slim2}) using a variable pressure regulator. A load limit value is generated if the valve stroke control command (scmd) exceeds the valve stroke limit value (min{slim1, slim2}) to reduce the load setpoint value. Operation of the gas turbine is stabilized using a low limit value (xlim) of a pressure drop ratio (x), wherein the pressure drop ratio (x) is a quotient of a pressure drop (dp) which occurs at the control valve and of a pressure (p1) upstream of the control valve.

Abstract: A fuel controller, and associated method, provides a fuel control output signal to a fuel control actuator to control operations. The fuel controller determines the fuel control output signal based on rotational speed error. A combustion air controller provides a combustion air control output signal to a combustion air control actuator to control operations. A cross channel controller is in communication with the fuel controller and the combustion air controller. The cross channel controller provides a combustion air control modification signal to the combustion air controller. The combustion air control modification signal is determined from the fuel control output signal using an air versus fuel model. The combustion air controller determines a preliminary combustion air control signal based on an exhaust temperature error, and further determines the combustion air control output signal based on both of the preliminary combustion air control signal and the combustion air control modification signal.

Abstract: A combined-cycle system includes a compressor, a gas turbine, a steam turbine, and an electric generator, which are coupled to the same shaft. A method of controlling the system envisages detecting a current compression ratio of the compressor, calculating a normalized compression ratio on the basis of the current compression ratio, and determining a load condition of the gas turbine on the basis of the normalized compression ratio. Moreover, a setpoint is selected, for at least one operating quantity of the gas turbine, and regulating signals are applied to actuators of the gas turbine so that the operating quantity of the gas turbine tends to reach the setpoint.

Abstract: A method for meeting both base-load and peak-load demand in a power production facility. By integrating a Fischer-Tropsch (FT) hydrocarbon production facility with an electrical power generating facility, peak-load power demand can be met by reducing the temperature of the FT reactor thereby increasing the quantity of tail gases and using FT tail gases to fuel a gas turbine generator set. The method enables rapid power response and allows the synthesis gas generating units and the FT units to operate with constant flow rates.

Abstract: A main air compressor delivers a compressed ambient gas flow with a compressed ambient gas flow rate to a turbine combustor. A fuel stream with a flow rate is delivered to the turbine combustor and mixed with the compressed ambient gas flow and an exhaust gas flow and burned with substantially stoichiometric combustion to form the exhaust gas flow and drive a turbine, thus operating the power plant at a first load. A portion of the exhaust gas flow is recirculated from the turbine to the turbine compressor and a portion is delivered to an exhaust path. The fuel stream flow rate and the compressed ambient gas flow rate are reduced, and substantially stoichiometric combustion is maintained and the power plant is operated at a second load. The fuel stream flow rate is further reduced and lean combustion is achieved and the power plant is operated at a third load.

Abstract: A coordinated air-fuel controller and associated method provide a fuel controller, a combustion air controller and a steady-state air versus fuel model. The fuel controller generates a fuel control output signal and the combustion air controller generates a combustion air control output signal. The fuel controller determines a preliminary fuel control signal based on at least one of first and second loop control signals, and determines the fuel control output signal based on the preliminary fuel control signal. The steady-state air versus fuel model processes the preliminary fuel control signal to determine an expected steady-state combustion air control signal. The combustion air controller determines a preliminary combustion air control signal based on at least one of a third loop control signal and a fourth loop control signal, and determines the combustion air control output signal based on the preliminary combustion air control signal and the expected steady-state combustion air control signal.

Abstract: A method for controlling a gas turbine, including during transient operating states, and such a gas turbine are provided. The gas turbine includes a compressor for compressing inducted combustion air, a combustion chamber for generating hot gas by combusting a fuel with the aid of the compressed combustion air, and a multistage turbine for expanding the generated hot gas and performing work. The controlling of the gais turbine is carried out in accordance with the hot gas temperature which is derived from a plurality of other measured operating variables of the gas turbine. A reliable controlling of the gas turbine is achieved, even during rapid changes, by pressure measurements being gathered exclusively at different points of the gas turbine for derivation of the hot gas temperature.

Abstract: A method and system for preventing or reducing the risk of combustion instabilities in a gas turbine includes utilizing a turbine controller computer processor to compare predetermined and stored stable combustion characteristics, including rate of change of the characteristics, with actual operating combustion characteristics. If the actual operating combustion characteristics are divergent from stable combustion characteristics then the controller modifies one or more gas turbine operating parameters which most rapidly stabilize the operation of the gas turbine.

Abstract: A method of manufacturing a wind turbine rotor blade is provided. Anticipated primary load paths within the rotor blade are predicted. Fibers of reinforcing material are dispensed onto a mold, having an orientation pattern of the fibers which is selected in dependence on the predicting step. Resin is also dispensed into the mold. A wind turbine rotor blade is provided. The blade comprises fibers of reinforcing material which are embedded in resin. The fibers are short, say in the range of 5 to 200 mm, and are orientated in dependence on an anticipated structural loading pattern of the rotor blade.

Abstract: A method of operating an electronic engine control to compensate for speed changes. The method includes receiving a fuel flow request, sensing actual engine rotor speed, calculating a fuel flow correction factor, establishing a final fuel flow request based on the fuel flow correction factor, and adjusting the actual set point of the MV to compensate for the actual engine rotor speed.

Abstract: Systems and methods for controlling combustion emission parameters associated with a gas turbine combustor. The method can include providing an optical path through a gas turbine exhaust duct, propagating light along the optical path, measuring exhaust species absorption of the light within the gas turbine exhaust duct, and controlling at least one of the combustion parameters based at least in part on the measured exhaust species absorption.

Abstract: There is described a method for operating an automation system which comprises at least two measuring modules, each connected to a higher order processing unit in order to communicate therewith. The higher order processing unit is informed of an event that is recorded by one of the at least two measuring modules. The processing unit then informs any available measuring module of the event.

Abstract: Methods of managing fuel temperatures in fuel injectors for gas turbine engines include cooling fuel circuits by initiating fuel flow therethrough using opened, closed, and semi-open control techniques. A fuel injector for a gas turbine engine includes a feed arm having a fuel inlet fitting for delivering fuel to at least one fuel conduit extending through the feed arm. A nozzle body depends from the feed arm and has at least one fuel circuit extending therethrough. The fuel circuit is configured and adapted to receive fuel from the feed arm and to issue fuel from an exit orifice of the nozzle body. Sensing means are provided adjacent to the at least one fuel circuit. The sensing means are configured and adapted to provide temperature feedback in order to control fuel flow in the at least one fuel circuit to maintain fuel temperature within a predetermined range.

Abstract: A method and algorithm are provided to operate a gas turbine at baseload in an emission compliant capable mode to avoid combustion dynamics while operating with cold fuel and hot fuel combustion hardware. The method includes performing a gas turbine operational sequence such as a startup to an emission compliant capable mode. A gas fuel temperature is measured. The gas turbine is operated in the emissions compliant capable mode according to a designated fuel split for avoiding combustion dynamics when a temperature for a gas fuel is below a designated value. A determination is made whether a modified wobbe index for the gas fuel is below an emissions compliant value. An alarm is activated if the modified wobbe index is below the emissions compliant value to notify the operator of a potential emissions shift.

Abstract: A method for controlling a gas turbine engine includes: generating model parameter data as a function of prediction error data, which model parameter data includes at least one model parameter that accounts for off-nominal operation of the engine; at least partially compensating an on-board model for the prediction error data using the model parameter data; generating model term data using the on-board model, wherein the on-board model includes at least one model term that accounts for the off-nominal operation of the engine; respectively updating one or more model parameters and one or more model terms of a model-based control algorithm with the model parameter data and model term data; and generating one or more effector signals using the model-based control algorithm.

Abstract: Control systems and a method for controlling a load point of a gas turbine engine are provided. A control system includes a controller that receives a temperature signal and a pressure signal associated with exhaust gases from the gas turbine engine. The controller is further configured to generate the fuel control signal. The controller is further configured to generate an actuator control signal such that flow restriction member is moved from the first operational position to the second operational position to restrict the flow path such that the exhaust gases have a temperature level within a desired turndown temperature range, the pressure level in the exhaust gases is less than a threshold pressure level, and the load point of the gas turbine engine is adjusted to toward a target load point.

Abstract: A method of optimizing the use of an aircraft power plant having at least one engine (1, 1?) operating within a performance envelope covering at least a first rating and a second rating, said first rating presenting a first power (P1) usable over a predetermined first time interval (D1), said second rating presenting a second power (P2) greater than said first power (P1), the second power (P2) being usable continuously over a predetermined second time interval (D2). Thus, while the engine (1, 1?) is developing a third power (P3) that is both greater than the first power (P1) and less than or equal to the second power (P2), a potential first duration of utilization (?T) of continuous use of said second power (P2) is determined and displayed, said first duration of utilization (?T) elapsing at a speed that is variable and that depends on said third power (P3).

Abstract: A combustion chamber and method for operating a combustion chamber are disclosed. The combustion chamber having at least a mixing device connected to a combustion device. The mixing device has a first fuel feeding stage, to inject fuel into the mixing device and mix the fuel with an oxidizer to then burn the fuel in the combustion device. The combustion device has a second fuel feeding stage to inject fuel into the combustion device. The fuel of the second stage is mixed with only an inert fluid to form a mixture that is then injected into the combustion chamber.

Abstract: An auxiliary power unit has a speed sensor for sensing a speed of operation of the auxiliary power unit. The speed sensor sends a signal to an electronic control box. The electronic control box is operable to control the auxiliary power unit. A branch line is for communicating the speed signal to a health monitoring system. The branch passes through an electronic component that will isolate the speed signal as it passes beyond the component and to the downstream use, such that corruption at a downstream use will not pass back upstream to corrupt the signals used in the electronic control box.

Abstract: At least one main air compressor makes a compressed ambient gas flow. The compressed ambient gas flow is delivered to both master and slave turbine combustors at a pressure that is greater than or substantially equal to an output pressure delivered to each turbine combustor from each turbine compressor as at least a first portion of a recirculated gas flow. A fuel stream is delivered to each turbine combustor, and combustible mixtures are formed and burned, forming the recirculated gas flows. A master and slave turbine power are produced, and each is substantially equal to at least a power required to rotate each turbine compressor. At least a portion of the recirculated gas flow is recirculated through recirculation loops. At least a second portion of the recirculated gas flow bypasses the combustors or an excess portion of each recirculated gas flow is vented or both.

Abstract: At least one main air compressor makes a compressed ambient gas flow. The compressed ambient gas flow is delivered to a turbine combustor at a pressure that is greater than or substantially equal to an output pressure delivered to the turbine combustor from a turbine compressor as at least a first portion of a recirculated gas flow. A fuel stream is delivered to the turbine combustor, and a combustible mixture is formed and burned, forming the recirculated gas flow. A turbine power is produced that is substantially equal to at least a power required to rotate the turbine compressor. At least a portion of the recirculated gas flow is recirculated through a recirculation loop. An excess portion of the recirculated gas flow is vented or a portion of the recirculated gas flow bypasses the turbine combustor or both.

Abstract: Provided are a combustor control method and a combustor controller capable of calculating the combustion air flow and the fuel flow in multi-shafts gas turbine with high precision and without the need of performing complicated calculations and thereby calculating a fuel-air ratio necessary for stable combustion control. The multi-shaft gas turbine is made up of a gas generator turbine and a power turbine. Combustors includes a diffusive combustion units and a plurality of premixed combustion units.

Abstract: A method of transitioning from a first operating mode to a second operating in a gas turbine engine. An amount of fuel provided to a primary fuel injection system of the combustor apparatus is reduced. An amount of fuel provided to a secondary fuel/air injection system of the combustor apparatus is reduced, wherein the secondary fuel/air injection system provides fuel to a secondary combustion zone downstream from a main combustion zone. A total amount of air provided to the combustor apparatus is reduced, wherein portions of the air are provided to each of the injection systems. Upon reaching operating parameters corresponding to the second operating mode, the amount of fuel provided to the primary fuel injection system is increased, the amount of fuel provided to the secondary fuel/air injection system is reduced, and the total amount of air provided to the combustor apparatus is increased.