Gas turbine engine and method for controlling emissions from a gas turbine engine

Abstract

To provide systems and methods of controlling emissions from a gas turbine engine having axial fuel staging (AFS) multi-stage combustors.SOLUTION: A gas turbine engine (100) includes a stage of guide vanes (104), a compressor (106) downstream from the stage of guide vanes (104), and a combustor (108) downstream from the compressor (106). The combustor (108) is an axial fuel staging multi-stage combustor. A controller (126) is communicatively coupled with the stage of guide vanes (104). The controller (126) is configured to monitor an intra-stage temperature of the multi-stage combustor (108), and selectively open and close the guide vanes to maintain the intra-stage temperature within a predefined temperature range.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to gas turbine engines, and more particularly, to systems and methods for controlling emissions from a gas turbine engine having an axial fuel staging (AFS) multi-stage combustor.

Background Art

[0002] Many known combustion turbine engines combust a fuel-air mixture within a combustor assembly to produce a combustion gas flow that is directed to a turbine assembly. The turbine assembly converts the energy of the combustion gas flow into work that can be used to power a machine such as a generator. Typically, when the turbine is operated at a relatively high load, the combustor exit temperature of the gas flow is high, and emissions of carbon monoxide (CO) and / or unburned hydrocarbons (UHC) can be effectively controlled. However, when the combustion process is not fully complete, undesirable levels of CO and / or UHC can be present in the turbine exhaust system. In a typical combustion turbine engine, the ability of hydrocarbon fuel to burn completely is based at least in part on the lower limit of the combustor exit temperature. As the turbine load decreases (often referred to as "turn-down"), in many gas turbines, it is necessary to reduce the combustor exit temperature, which can have the undesirable result of increasing the levels of CO and UHC being formed. Therefore, it is desirable to maintain a high combustor temperature when the turbine engine reduces its load.

Summary of the Invention

[0003] In one aspect, a gas turbine engine is provided. The gas turbine engine includes a stage of guide vanes, a compressor downstream of the stage of guide vanes, and a combustor downstream of the compressor. The combustor includes a primary combustion zone and a secondary combustion zone downstream of the primary combustion zone. The primary combustion zone includes an outlet configured to direct combustion gases toward the secondary combustion zone. A controller is communicatively coupled to the stage of guide vanes and is configured to selectively open and close the guide vanes to monitor the temperature at the outlet of the primary combustion zone and to facilitate maintaining the temperature within a predefined temperature range.

[0004] In another aspect, a gas turbine engine is provided. The gas turbine engine includes a stage of guide vanes, a compressor downstream of the stage of guide vanes, and a combustor downstream of the compressor. The combustor includes a primary combustion zone and a secondary combustion zone downstream of the primary combustion zone. The primary combustion zone includes an outlet configured to direct combustion gases toward the secondary combustion zone. A controller is communicatively coupled to the stage of guide vanes and is configured to selectively open and close the guide vanes to monitor the temperature at the outlet of the primary combustion zone, identify the combustion mode in which the combustor is operating, and facilitate maintaining the temperature at a temperature threshold associated with the combustion mode in which the combustor is operating.

[0005] In yet another aspect, a method of controlling emissions from a gas turbine engine including a compressor and a combustor is provided. The method includes monitoring the temperature within the combustor of the gas turbine engine, the combustor including a primary combustion zone and a secondary combustion zone downstream of the primary combustion zone, the temperature being monitored at the outlet of the primary combustion zone. The method also includes identifying the combustion mode in which the combustor is operating and selectively opening and closing guide vanes upstream of the compressor to facilitate maintaining the temperature at a temperature threshold associated with the combustion mode in which the combustor is operating. BRIEF DESCRIPTION OF THE DRAWINGS

[0006]

Figure 1

Figure 2

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0007] The embodiments described herein relate to systems and methods for controlling emissions from a gas turbine engine having an axial fuel staging (AFS) multi-stage combustor. For example, emissions can be controlled by adjusting the inlet guide vanes or variable guide vanes of the compressor of the gas turbine engine, thereby adjusting the air flow to the multi-stage combustor. By adjusting the air flow, it becomes easier to control the in-stage temperature of the multi-stage combustor, which is an important factor in emissions control. In an exemplary embodiment, the selective positioning of the guide vanes is automatically controlled by a proportional-integral (PI) controller. A detailed physics-based model for the gas turbine engine is used to calculate and / or estimate the temperature at the exit of the primary combustion zone of the multi-stage combustor, and this specified temperature is provided to a closed-loop controller. Thus, the desired exit temperature can be dynamically imposed by adjusting the guide vanes. The desired exit temperature may be a constant value or may be changed according to a schedule corresponding to the physical state within the combustor. By controlling and maintaining the desired temperature within a predefined range, it becomes easier to enhance emissions control, such as when the gas turbine engine is in a transient operating state. Additionally, the selective adjustment of the guide vanes may be used to operate the combustor at a reduced temperature in order to reduce thermal distortion on the combustion system and extend the component life.

[0008] Unless otherwise indicated, words such as "generally", "substantially", and "approximately" used in this specification to indicate approximation mean that the term so modified is applicable only to the approximate degree recognized by those skilled in the art, rather than to an absolute or complete degree. Thus, a value modified by one or more terms such as "approximately", "about", and "substantially" should not be limited to the specified exact value. In at least some instances, the words indicating approximation can correspond to the accuracy of the instrument used to measure the value. Further, unless otherwise indicated, terms such as "first", "second", etc. are used in this specification merely as labels and do not impose an order, position, or hierarchical requirement on the items they refer to. Moreover, for example, a reference to a "second" item does not require or preclude the existence of, for example, a "first" or smaller numbered item, or a "third" or larger numbered item.

[0009] Figure 1 is a schematic diagram of an exemplary gas turbine engine 100. In an exemplary embodiment, gas turbine engine 100 includes an inlet duct 102, a stage of guide vanes 104, a compressor 106, a combustor 108, and a turbine section 110, which are coupled in a serial relationship. Inlet air 112 is directed through duct 102 and the stage of guide vanes 104 before being directed toward compressor 106. Compressor 106 compresses inlet air 112 and discharges compressed air 114 toward combustor 108. Fuel injection system 116 supplies fuel 118 to combustor 108, and the resulting fuel-air mixture is ignited within combustor 108. Combustion gases 120 are discharged from combustor 108 and directed toward turbine section 110 where the thermal energy of combustion gases 120 is converted into work. A portion of the work is used to drive compressor 106, and the remaining work is used to drive generator 122 to generate electricity.

[0010] In an exemplary embodiment, the gas turbine engine 100 includes the gas turbine engine 100, a generator 122, and a plurality of sensors 124 for detecting various conditions of the ambient environment. Exemplary sensors 124 include temperature sensors, pressure sensors, and the like. The temperature sensor can monitor the compressor discharge temperature, the turbine exhaust gas temperature, and / or other temperature measurements of the gas flow through the gas turbine engine 100. The pressure sensor can monitor the static pressure level and the dynamic pressure level at the inlet and outlet of the compressor, the turbine exhaust, and / or other locations within the gas turbine engine 100. The sensors 124 may also include, but are not limited to, a flow rate sensor, a speed sensor, a flame detector sensor, a valve position sensor, a guide vane angle sensor, etc., that detect various parameters related to the operation of the gas turbine engine 100. Typically, the pressure, temperature, flow rate, speed, guide vane angle, and many other sensors on a gas turbine are reliable, require infrequent calibration and maintenance, and are relatively inexpensive. However, due to the harsh characteristics of the combustion gas, it is generally difficult to directly monitor the combustion gas temperature or the combustor discharge temperature using, for example, a thermocouple. As described above, the combustor temperature is an important factor in emissions control.

[0011] In an exemplary embodiment, the controller 126 receives the feedback transmitted from the sensor 124 and controls the operation of the gas turbine engine 100 based on the feedback. The controller 126 may be a computer system having a processor that executes a program to control the operation of the gas turbine engine 100. The operation may be controlled using sensor feedback, instructions from a human operator, and / or a combustor temperature estimate that may be determined based on the sensor feedback. In one embodiment, the controller 126 uses a physics-based model that receives sensor feedback as an input to estimate and / or calculate the combustion gas temperature or the combustor discharge temperature. The estimate of the combustion gas temperature or the combustor discharge temperature may be based at least on the air flow output from the compressor 106, the fuel flow input to the combustor 108, and / or the operating state of the inlet bleed heating (IBH) system 128. The air flow output from the compressor 106 depends at least in part on the angle of the inter-stage guide vanes 104 that adjust the air flow to the compressor 106.

[0012] In a combustion system having a single combustion stage, the model assumes that all of the fuel is burned in a single combustion chamber. In axial fuel staging, the current model uses data on valve position and fuel pressure to determine the fuel flow rate and thus the ratio between the primary combustion fuel flow rate and the secondary combustion fuel flow rate. Thus, the model is such that a specific percentage of the fuel is burned in the first combustion chamber with the first determined air flow rate and the remaining percentage of the fuel is then burned in the second combustion chamber with the second determined air flow rate. The second determined air flow rate may include some additional air flow (such as a cooling flow) that is supplied to the second combustion chamber without passing through the first combustion chamber.

[0013] During operation, the controller 126 adjusts the total fuel flow rate, the relative position of the inlet guide vanes (or, alternatively and / or additionally, the variable guide vanes within the compressor 106), the operating state of the IBH system 128 (i.e., the air flow extraction rate from the compressor 106), and the combustor fuel split to achieve the desired cycle match point (i.e., to produce the desired power output and heat rate while observing the operating boundaries). The total fuel flow rate and the guide vane position are important factors in achieving the desired results. A typical part load or transient control mode involves setting the fuel flow rate and the guide vane angle to meet the load (generator output) demand while monitoring the exhaust temperature profile (temperature control curve). When base load or steady state operation is achieved, the guide vanes are typically positioned at those angles that are at their maximum physical limits for directing the air flow through the guide vanes. At base load, the fuel flow rate adjustment and the combustion split are generally adjusted to achieve the exhaust temperature profile required to meet the emissions limits and other gas turbine operating limits.

[0014] For example, the controller 126 is selectively operable to maintain the NOx and CO emissions in the turbine exhaust within certain predefined limits and to maintain the combustor temperature within a predefined temperature range. The predefined temperature range may be based on the current physical state within the combustor. For example, the controller 126 can selectively control various parameters of the gas turbine engine 100, including those described above, to maintain the estimated combustion gas or combustor discharge temperature within one of a plurality of predefined temperature ranges. The predefined values of the physical state, or the ranges of the predefined values, can correspond to the respective predefined temperature ranges. Additionally, the combustor 108 is operable in one of a plurality of combustion modes based on the current physical state of the gas turbine engine 100. By maintaining the combustor temperature within the respective predefined temperature ranges, the combustor 108 can operate in a combustion mode for producing a reduced dynamic response and reduced emissions with respect to the current physical state of the gas turbine engine 100. When the gas turbine engine 100 is in the start operating mode or the turn-down transient operating mode, the controller 126 may be operable to dynamically adjust the combustion temperature accordingly.

[0015] In an exemplary embodiment, as described in more detail below, the combination of compressor discharge pressure and temperature at the outlet of the primary combustion zone is used to initiate a mode transition. For example, as the turbine load increases, the outlet temperature is controlled by opening the guide vanes, thereby increasing the compressor discharge pressure. When a threshold of the compressor discharge pressure is met, a transition to a higher combustion mode is initiated and the turbine load is controlled based on the new outlet temperature value. As the turbine load decreases, the guide vanes are closed and the outlet temperature begins to drop, thereby initiating a transition to a lower combustion mode. In an alternative embodiment, the opening and closing of the guide vanes for outlet temperature control may be used in some but not all combustion modes. For example, it may be desirable to control the outlet temperature for an active combustion mode in the lower 50% of the load range of the gas turbine engine 100. The IBH system 128 may also be used to manipulate the cycle conditions of the combustor and the outlet temperature from the primary combustion zone. For example, as the turbine load decreases, the IBH system 128 may be selectively activated to modify the compressor discharge pressure, thereby providing another form of control for maintaining the desired outlet temperature from the primary combustion zone.

[0016] FIG. 2 is a schematic view of an exemplary combustor 108. In an exemplary embodiment, the combustor 108 includes a head end 130, an exhaust end 132, and a combustion chamber 134 defined therebetween. The head end 130 includes a primary fuel injector 136 for supplying fuel from the fuel injection system 116 to the combustion chamber 134. The fuel is mixed with air from the compressor 106 (shown in FIG. 1), and the fuel-air mixture is combusted within the primary combustion zone 138. In an exemplary embodiment, the primary combustion zone 138 includes an outlet 140 that defines a boundary between the primary combustion zone 138 and the secondary combustion zone 142. The combustion gas 144 is discharged from the primary combustion zone 138 through the outlet 140 and directed to the secondary combustion zone 142.

[0017] Within the secondary combustion zone 142, the combustor 108 includes a plurality of secondary (i.e., axial fuel staging (AFS)) injectors that are circumferentially spaced around the combustor 108 and radially directed with respect to the axis of the combustion chamber 134. The secondary fuel injectors 146 supply fuel from the fuel injection system 116 for mixing with the combustion gas 144. Additional fuel is burned within the secondary combustion zone 142, and the combustion gas 120 is discharged from the discharge end 132.

[0018] In some embodiments, the additional fuel injected into zone 142 may be supplied from a secondary fuel source, in which case the secondary fuel may be more volatile than the fuel supplied to the primary combustion zone 138 (e.g., but not limited to, any suitable gaseous fuel or liquid fuel such as natural gas, liquefied natural gas (LNG), synthesis gas, associated petroleum gas, methane, ethane, butane, propane, biogas, sewage gas, landfill gas, coal mine gas, gasoline, diesel, naphtha, kerosene, methanol, biofuel, and / or any combination thereof). In some embodiments, the secondary fuel may be the same fuel as the primary fuel. By supplying fuel to both the primary combustion zone 138 and the secondary combustion zone 142, more complete combustion can be achieved, thereby facilitating the reduction of certain emissions (e.g., NOx emissions) discharged from the gas turbine engine 100.

[0019] As described above, by maintaining the combustor temperature within each of the predefined temperature ranges, the combustor 108 is able to operate in a combustion mode while generating a reduced dynamic response and reduced emissions with respect to the current physical state of the gas turbine engine 100 (shown in FIG. 1). In an exemplary embodiment, the controller 126 continuously calculates (i.e., monitors) the temperature at the outlet 140 of the primary combustion zone 138, identifies the combustion mode in which the combustor 108 is operating, and controls the operation of the stage 104 of the guide vanes to facilitate maintaining the monitored temperature within each of the predefined temperature ranges associated with the identified combustion mode. By controlling the operation of the guide vanes, the airflow supplied to and / or directed through the compressor 106 is adjusted, and thus the airflow supplied to the combustor 108 is adjusted. Reducing the airflow to the combustor 108 generally causes the combustor temperature to increase, and increasing the airflow to the combustor 108 when the fuel supply remains constant generally causes the combustor temperature to decrease.

[0020] Each of the predefined temperature ranges is defined by a minimum temperature threshold and a maximum temperature threshold. Generally, emissions are more readily reduced at higher combustion temperatures. Thus, in one embodiment, the controller 126 controls the operation of the guide vanes to maintain the monitored temperature at or near the maximum temperature threshold of each of the predefined temperature ranges. In other words, the guide vanes are controlled to maintain the monitored temperature closer to the maximum temperature threshold than the minimum temperature threshold. Alternatively, the guide vanes are controlled to maintain the monitored temperature at a desired temperature threshold within the predefined temperature range to achieve desired emissions or kinetic characteristics.

[0021] FIG. 3 is a flow diagram illustrating an exemplary method 200 for controlling emissions from a gas turbine engine. Method 200 includes monitoring 202 the temperature within a combustor of the gas turbine engine, the combustor including a primary combustion zone and a secondary combustion zone downstream from the primary combustion zone, the temperature being monitored at the outlet of the primary combustion zone. Method 200 also includes identifying 204 the combustion mode in which the combustor is operating and selectively opening and closing guide vanes upstream of a compressor to maintain the temperature at a temperature threshold associated with the combustion mode in which the combustor is operating 206.

[0022] The embodiments described herein relate to systems and methods for controlling emissions from a gas turbine engine. The emissions are controlled by monitoring the outlet temperature of the primary combustion zone of a multi-stage combustor and dynamically imposing, by controlling the air flow to the combustor via guide vane control. Thus, the systems and methods described herein facilitate providing better emissions control, lower turndown, and reduced thermal distortion to high temperature gas path components.

[0023] The foregoing description is intended only to be illustrative, and those skilled in the art will recognize that modifications may be made to the described embodiments without departing from the scope of the disclosed invention. For example, the process steps described herein may be modified, for example, in duration, temperature, or time between cycles. Further other modifications that fall within the scope of the present invention will be apparent to those skilled in the art in light of the present disclosure, and such modifications are intended to fall within the scope of the appended claims.

[0024] Exemplary embodiments of a system and method for controlling emissions from a gas turbine engine have been described in detail above. The method is not limited to the specific embodiments described herein. Rather, the steps of the method may be utilized separately and independently of the other steps described herein. For example, the method described herein is not limited to practice in the industrial gas turbine engines described herein. Rather, the exemplary embodiments can be implemented and utilized in connection with many other applications.

[0025] Certain features of the various embodiments of the present invention may be shown in some drawings and not in others, but this is merely for convenience. Moreover, references to "one embodiment" in the foregoing description are not to be construed as excluding the existence of additional embodiments that also incorporate the recited features. According to the principles of the present invention, any feature of any drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0026] Although the present invention has been described with respect to various specific embodiments, those skilled in the art will recognize that the present invention can be practiced with modifications within the spirit and scope of the claims.

Description of the Reference Numerals

[0027] 100 Gas turbine engine 102 Inlet duct 104 Stage of guide vanes 106 Compressor 108 Combustor 110 Turbine section 112 Intake 114 Compressed air 116 Fuel injection system 118 Fuel 120 Combustion gas 122 Generator 124 Sensor 126 Controller 128 Inlet Bleed Heating (IBH) system 130 Head end 132 Discharge end 134 Combustion chamber 136 Primary fuel injector 138 Primary combustion zone 140 Outlet 142 Secondary combustion zone 144 Combustion gas 146 Secondary fuel injector 200 Method

Claims

1. a stage (104) of a guide vane, a compressor (106) downstream from the stage (104) of the guide vane, a combustor (108) downstream from the compressor (106), wherein the combustor (108) includes a primary combustion zone (138) and a secondary combustion zone (142) downstream from the primary combustion zone (138), wherein the primary combustion zone (138) includes an outlet (140) defining a boundary between the primary combustion zone (138) and the secondary combustion zone (142), and the outlet (140) is configured to direct combustion gas (144) exiting the primary combustion zone (138) toward the secondary combustion zone (142), the combustor (108), a controller (126) communicably coupled to the stage (104) of the guide vane, wherein the controller (126) monitors a temperature at the outlet (140) of the primary combustion zone (138), determines a combustion mode in which the combustor (108) is operating, and selectively opens and closes the guide vane to facilitate maintaining the temperature within a predefined temperature range associated with the combustion mode in which the combustor (108) is operating configured controller (126) and A gas turbine engine (100) comprising.

2. The gas turbine engine (100) according to claim 1, wherein the combustor (108) is operable in a plurality of combustion modes, and the controller (126) is further configured to facilitate maintaining the temperature within respective predefined temperature ranges associated with each combustion mode.

3. The gas turbine engine (100) according to claim 2, wherein each respective predefined temperature range is defined by a respective maximum temperature threshold, and the controller (126) is further configured to selectively open and close the guide vane to maintain the temperature at the respective maximum temperature threshold.

4. The gas turbine engine (100) according to claim 1, wherein the controller (126) is configured to calculate the temperature at the outlet (140) of the primary combustion zone (138).

5. The gas turbine engine (100) according to claim 4, wherein the controller (126) is further configured to calculate the temperature based on an air flow output from the compressor (106), a fuel flow rate input to the combustor (108), and an operating state of the inlet air extraction heating system (128).

6. The gas turbine engine (100) according to claim 4, wherein the controller (126) is further configured to calculate the temperature using a physics-based model.

7. The gas turbine engine (100) according to claim 1, further comprising a fuel injection system (116) including a primary fuel injector (136) configured to supply fuel (118) to the primary combustion zone (138) and a secondary fuel injector (146) configured to supply fuel (118) to the secondary combustion zone (142).

8. The gas turbine engine (100) according to claim 1, wherein the controller (126) comprises at least one of a proportional controller or a proportional-integral (PI) controller.

9. The gas turbine engine (100) according to claim 1, wherein the combustor (108) is operable in a plurality of combustion modes.

10. The gas turbine engine (100) according to claim 9, wherein the controller (126) is further configured to facilitate maintaining the temperature within a respective predefined temperature range associated with each combustion mode.

11. The gas turbine engine (100) according to claim 9, wherein the controller (126) is further configured to calculate the temperature at the outlet (140) of the primary combustion zone (138).

12. The gas turbine engine (100) according to claim 11, wherein the controller (126) is further configured to calculate the temperature based on an air flow output from the compressor (106), a fuel flow rate input to the combustor (108), and an operating state of the inlet air extraction heating system (128).

13. A gas turbine engine (100) according to claim 9, further comprising a fuel injection system (116) including a primary fuel injector (136) configured to supply fuel (118) to the primary combustion zone (138) and a secondary fuel injector (146) configured to supply fuel (118) to the secondary combustion zone (142).

14. A method (200) for controlling emissions from a gas turbine engine (100) including a compressor (106) and a combustor (108), the method comprising: monitoring a temperature at an outlet (140) defining a boundary between the primary combustion zone (138) and the secondary combustion zone (142) downstream of the primary combustion zone (138), the combustor (108) including the primary combustion zone (138) and the secondary combustion zone (142); identifying an operating combustion mode of the combustor (108); selectively opening and closing guide vanes upstream of the compressor (106) to facilitate maintaining the temperature at a temperature threshold associated with the operating combustion mode of the combustor (108). A method (200) comprising the steps of:

15. The method (200) according to claim 14, further comprising controlling the operation of an inlet air heating system (128) to facilitate maintaining the temperature at the temperature threshold.

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