Method of controlling a burner

Abstract

A method of controlling a combustor of a gas turbine engine is disclosed. The method comprises the steps of: supplying a total fuel quantity to the combustor depending on a load of the gas turbine engine, the total fuel quantity being distributed into a pilot fuel quantity and a main fuel quantity via a pilot fuel fraction; monitoring at least one signal of at least one condition of the gas turbine engine; generating a steady state value of the at least one signal indicative of a steady state of the gas turbine engine; detecting a change of the at least one signal relative to the steady state value. When the change of the at least one signal relative to the steady state value exceeds a predetermined limit, the method applies the steps of: generating a transient fraction compensation for the pilot fuel fraction according to a look-up table; and applying the transient fraction compensation to the pilot fuel fraction while maintaining the total fuel quantity supplied at any point in time.

Description

Technical Field

[0001] This invention relates to a method for controlling the combustion system of a gas turbine engine, and more particularly to a method for controlling the combustion system to improve reliability and / or reduce emissions during transient conditions of the gas turbine engine. Background Technology

[0002] In gas turbine engines, multiple fuel supply lines are used to introduce fuel into the combustion chamber from multiple injection points. Typically, fuel is fed through different fuel supply lines for primary fuel or pilot fuel and main fuel. Within the combustion chamber, the pilot flame and main flame are distinct, although their interaction is known to provide flame stability. The main flame has a relatively high air-fuel ratio and is a lean-burn flame that provides good efficiency and low emissions. The pilot flame has a lower air-fuel ratio and burns with a richer flame. The pilot flame is more stable than the main flame and helps stabilize the main flame. The engine control unit controls the share or ratio of total fuel in the pilot fuel and main fuel via multiple controllable valves. The amount of total fuel supplied to each of the pilot fuel injectors and main fuel injectors is planned and scheduled according to the gas turbine engine load.

[0003] Although the total fuel quantity is divided into pilot fuel quantity and main fuel quantity, and each has a pilot fuel share and a main fuel share, the fuel share is usually referred to as the pilot fuel share, which is the proportion or percentage of the pilot fuel quantity to the total fuel quantity. Generally, under higher engine loads, more fuel is supplied proportionally to the main fuel injectors, resulting in a lower pilot fuel share, while under lower engine loads, more fuel is supplied proportionally to the pilot fuel injectors, resulting in a higher pilot fuel share. Typically, the pilot fuel share is planned and scheduled according to the load of the gas turbine engine.

[0004] Variations in engine load, fuel calorific value, and environmental conditions can cause combustion instability. This combustion instability can lead to increased harmful emissions, increased component temperatures, pressure fluctuations detrimental to structural integrity, and blow-out. These are all significant adverse effects of combustion instability.

[0005] EP1974139B1 discloses active adjustment of the ignition fuel share and is designed to adapt to changes in conditions experienced during steady-state operation, i.e., constant load demands. Such changes in conditions include ambient temperature, manufacturing tolerances, and specific site requirements. However, considering emission restrictions, this active adjustment is set at a conservative level to ensure full burner operability, particularly managing combustion instability. The method of EP1974139B1 is referred to herein as active ignition.

[0006] EP2486328B1 discloses a control device arranged to change the proportions of the main fuel supply and the ignition fuel supply to the burner via signals based on the temperature and pressure of the burner 16 and based on the progress of time, i.e., by controlling the ignition fuel proportion. The control device is also configured such that the signal also represents load information indicating the load on the combustion equipment. The control device aims to maintain the burner temperature below a predetermined maximum temperature limit and to maintain pressure variations within the combustion volume below a predetermined maximum pressure variation limit, while maintaining a substantially constant overall fuel supply in the fuel supply lines to the equipment. The control device of EP2486328B1 is referred to as intelligent control.

[0007] The methods for controlling fuel share disclosed in EP1974139B1 and EP2486328B1, individually or in combination, provide good combustion operability and low emissions under steady-state conditions. However, there has been a desire to further improve combustion operability, reliability, and further reduce emissions. Summary of the Invention

[0008] The present invention has at least the following objectives, particularly during transient engine conditions, to reduce the likelihood of flame failure events and combustion instability during transient load changes and the recovery period following these transient events. Furthermore, the present invention reduces the likelihood of adverse effects of combustion instability on emissions during the period following a transient event under stable operating conditions.

[0009] The aforementioned objective is achieved by a method for controlling the combustor of a gas turbine engine, the method comprising the steps of: supplying a total fuel quantity to the combustor depending on the load of the gas turbine engine, the total fuel quantity being allocated into an ignition fuel quantity and a main fuel quantity via an ignition fuel share, the ignition fuel share being a percentage of the ignition fuel quantity to the total fuel quantity; monitoring at least one signal of at least one condition of the gas turbine engine; and generating a steady-state value of at least one signal indicating a steady-state of the gas turbine engine. The method further comprises the steps of: detecting a change in at least one signal relative to the steady-state value; generating a transient share compensation for the ignition fuel share according to a lookup table when the change in at least one signal relative to the steady-state value exceeds a predetermined limit; and applying the transient share compensation to the ignition fuel share while maintaining the total fuel quantity supplied at any given time.

[0010] At least one condition of a gas turbine engine is a step that enables it to indicate the state of the air / fuel ratio in the combustor, and in particular, changes in the air / fuel ratio. At least one condition can be any one or more of the following: the position of the variable guide vane, the position of the blow-off valve, the position of the bleed valve, the fuel energy input rate, the engine's rotational speed requirement, and the load requirement value.

[0011] The ignition fuel share can be a planned ignition fuel share or a planned ignition fuel share with a steady-state active ignition fuel share applied.

[0012] The method includes the following steps: monitoring combustion instability; monitoring the temperature of the burner; and applying a steady-state active ignition share compensation to adjust the planned ignition fuel share to create a steady-state ignition fuel share when the burner temperature exceeds a predetermined value and / or the combustion instability exceeds a predetermined value.

[0013] The step of generating a steady-state value of at least one signal indicating the steady-state of a gas turbine engine may include feeding at least one signal into a low-pass filter having a time constant of at least 1 second and preferably less than 10 seconds, preferably in the range of 5 to 7 seconds.

[0014] The method may include the following steps: selecting the largest transient share compensation among all generated transient share compensations; and applying transient share compensation to the ignition fuel share using the largest transient share compensation among all generated transient share compensations.

[0015] The step of applying transient ignition share compensation to the steady-state ignition fuel share may include immediately increasing the ignition fuel share.

[0016] The method gradually reduces transient ignition share compensation as the change of at least one signal relative to its steady-state value decreases from its peak value, such that if the required share compensation decreases to zero, the transient ignition share compensation is reduced to zero.

[0017] The step of gradually reducing the transient ignition share compensation may include a maximum reduction rate having a first maximum reduction rate and a second maximum reduction rate, wherein the first reduction rate is greater than the second reduction rate of the transient active ignition share compensation.

[0018] The lookup table can include a series of transient fuel share values ​​for each engine condition. A lookup table can exist for each transient fuel share value for each engine condition. This series of transient fuel share values ​​can be based on the gas turbine engine condition and can be linear or non-linear. The series of transient fuel share values ​​can be linearly interpolated between transient fuel share values.

[0019] A series of transient fuel share values ​​for each engine condition can have a maximum value that cannot be exceeded. Attached Figure Description

[0020] The above-described properties and other features and advantages of the present technology, as well as the ways of obtaining these properties and other features and advantages, will become more apparent from the following description of embodiments of the present technology taken in conjunction with the accompanying drawings, and the currently disclosed burner and operating method will be better understood.

[0021] Figure 1 A portion of the turbine engine is shown in cross-section, and a combustion system incorporated herein according to this disclosure is also included.

[0022] Figure 2 This is a schematic cross-section of the burner in the combustion system of a gas turbine according to the present invention.

[0023] Figure 3 This is a schematic diagram of a fuel supply system for a combustion system of a gas turbine, the fuel supply system including a controller programmed to control the burner according to the present invention.

[0024] Figure 4 This is a flowchart illustrating a method for controlling the burner of a gas turbine engine according to the present invention. Detailed Implementation

[0025] Figure 1 This is a schematic diagram and cross-sectional view of the overall arrangement of a turbine engine 10, which includes an inlet 12, a compressor 14, a combustor system 16, a turbine system 18, an exhaust duct 20, and twin shaft units 22 and 24. The turbine engine 10 is generally arranged around an axis 26, which is the axis of rotation for rotating components. The shafts of the twin shaft units 22 and 24 may have the same or opposite directions of rotation. The combustor system 16 includes an annular array of combustors or combustor canisters 36, with only one combustor or combustor canister 36 shown. In one example, there are six combustors 36 evenly spaced around the engine 10. The turbine system 18 includes a high-pressure turbine 28 driven to the compressor 14 via a first shaft 22 of the twin shaft unit. The turbine system 18 also includes a low-pressure turbine 30 driven to a load (not shown) via a second shaft 24 of the twin shaft unit.

[0026] The terms radial, circumferential, and axial are relative to the engine's axis of rotation 26, or as otherwise stated, such as relative to the combustor axis 44. The terms upstream and downstream are relative to the general direction of gas flow through the engine, such as... Figure 1 As shown, it is usually from left to right.

[0027] Compressor 14 includes an axially arranged series of stator blades and rotor blades mounted in a conventional manner. The stator or compressor blades may be fixed or have variable geometry to improve airflow to the downstream rotor or compressor blades, as is known. Each turbine 28, 30 includes an axially arranged series of stator blades and rotor blades. The stator blades may be mounted to a radial housing or radial inner cylinder. The rotor blades are mounted via rotor discs arranged and operated in a conventional manner. The rotor assembly includes an annular array of rotor blades or blades and rotor discs.

[0028] Each burner 36 consists of two walls—an inner wall 37 and an outer wall 39—defining a generally annular space or plenum 35 between the inner wall 37 and the outer wall 39. At the head of the burner 36 is a radial swirler 40, which includes swirl plates or base plates 45, an annular array of swirler blades 46, and fuel injection points, as described in more detail later. Following the swirler 40 is a pre-chamber 42, and then the main combustion chamber 38. These burner components 36 are generally arranged around a burner axis 44. The annular array of swirler blades 46 defines swirler slots 47 arranged around the base plate 45.

[0029] In operation, air 32 is drawn into the engine 10 through inlet 12 and enters the compressor 14, where the impellers and blades of the continuous stage compress the air 34 before it is delivered to the combustor system 16. The compressed air 34 flows through the booster chamber 35 and enters the cyclone separator 40. The cyclone separator 40 generates highly turbulent air into which fuel is injected. The air / fuel mixture is delivered to the pre-combustion chamber 42, where it continues to mix, and then to the main combustion chamber 38. In the combustion chamber 38, the compressed air and fuel mixture is ignited and burned. The resulting hot working gas stream is directed to the high-pressure turbine 28, causing it to expand and drive the high-pressure turbine 28, which in turn drives the compressor 14 via the first shaft 22. After passing through the high-pressure turbine 28, the hot working gas stream is directed to the low-pressure turbine 30, which drives the load via the second shaft 24.

[0030] The low-pressure turbine 30 can also be referred to as a power turbine, and the second shaft 24 can also be referred to as a power shaft. The load is typically an electric motor for generating electricity or a mechanical machine such as a pump or process compressor. Other known loads can be driven via the low-pressure turbine. The fuel can be in gaseous and / or liquid form.

[0031] Reference Figure 1 The turbine engine 10 shown and described is merely one example of many engines or turbomachinery into which the present invention can be incorporated. Such engines can be gas turbines or steam turbines, and include single-shaft, dual-shaft, and triple-shaft engines used in marine, industrial, and aerospace applications.

[0032] Figure 2 This is a cross-sectional view of a portion of one of the combustors 36 in a set of combustors of a turbine engine 10 according to the present invention. The radial vortex 40 includes an annular array of blades 46 arranged around a combustor axis 44, and this annular array of blades 46 is tangentially angled relative to the combustor axis 44 to impart a vortex flow 55 to the mixed air and fuel, as is known in the art. Figure 2 As seen, the vortex flow 55 rotates about the burner axis 44 and flows in a generally left-to-right direction. Swirl impellers 46 form an array of mixing channels or swirl slots 47 between each successive swirl impeller 46. The swirler 40 also includes main fuel injectors 48A, 48B for injecting the main fuel and an ignition fuel injector 50 for injecting ignition fuel. The swirler 40 includes a base plate 45 having an ignition surface 52 facing the pre-combustion chamber 42 and defining an upstream axial extent of the pre-combustion chamber. The pre-combustion chamber 42 is also defined by an annular wall 54 symmetrically arranged around the burner axis 44. The pre-combustion chamber 42 has an inlet 66 and an outlet 68. The outlet 68 is formed at or located at the lip 69 of the pre-combustion chamber 42 and defines the termination position of the pre-combustion chamber 42. Following the annular wall 54 of the pre-combustion chamber 42 is a generally annular wall 37 of the main combustion chamber 38. Downstream from the lip 69, the generally annular wall 37 is divergent and open to define the main combustion chamber 38. The main combustion chamber 38 has a cross-sectional area larger than that of the pre-combustion chamber 42.

[0033] Two distinct fuel / air mixtures and subsequent combustion flames exist within combustion chamber 38; the ignition flame 56 originates from the ignition fuel / air mixture, while the main flame 58 originates from the main fuel / air mixture. The lines indicating 56 and 58 show the flame front and the corresponding flames continuing downstream of the flame front. The ignition flame 56 and the main flame 58 differ from each other due to the location of their respective fuel injection points within or near the mixing channel 47 in the airflow 34A. The main fuel injectors 48A and 48B inject main fuel into the swirler slots or mixing channel 47, and are located further away from the burner axis 44, i.e., radially outside the burner axis 44, compared to the ignition fuel injector 50. Therefore, the corresponding fuel / air mixtures form significantly different flame regions, with the ignition flame 56 typically radially inside the main flame 58. In this example, the ignition fuel injector 50 is positioned through the substrate 45, and this ignition fuel injector 50 is radially inside the swirler 40.

[0034] As in the case here, a radial swirler has, or can be defined as having, a swirl number SN. The radial swirler 40 described above has an SN in the range of 0.5 to 0.8. As is known in the art, the swirl number can be calculated, and here it can be said that the swirl number can be defined by the relationship between the angular momentum flux and the linear momentum flux of the fuel / air mixture. That is, the angular momentum is related to the rotational velocity about the combustor axis 44, while the linear momentum is related to the velocity in the axial direction along the combustor axis 44. Therefore, SN is defined herein as the ratio of the tangential momentum to the axial momentum of the fluid or fuel / air mixture.

[0035] Figure 3This is a schematic diagram of a fuel supply device 70 for supplying fuel to the burners of the combustion system. The fuel supply device 70 includes a main fuel supply 72, an ignition fuel supply 74, a total fuel supply 76, a main fuel valve 80, an ignition fuel valve 82, a combustion monitor 84, and a controller 86. The controller 86 is part of the engine's electronic control unit (ECU), but the controller 86 can be a separate component. The controller 86 includes software programming, which is part of the overall engine control software. The controller 86 is connected to the main fuel valve 80, ignition fuel valve 82, and combustion monitor 84 of each burner 36. The combustion monitor 84 measures combustion instability via dynamic pressure fluctuations. As mentioned, the combustion system 16 has multiple burners 36; in this case, there are six burners 36 evenly spaced around the engine's axis 26. Each burner 36 has its own main fuel supply 70 controlled by a main fuel valve 80 and an ignition fuel supply 72 controlled by an ignition fuel valve 82, and each main fuel valve 80 and ignition fuel valve 82 is connected to and controlled by a controller 86. Each burner 36 has at least one combustion monitor 84, and each combustion monitor 84 is connected to the controller 36.

[0036] The controller 86 is connected to, monitors, and controls the positions of the variable guide vane, the blow-off valve, and the bleed valve. The positions of these three valves are continuously monitored by the controller 86. These positions are planned and generally operated routinely according to engine conditions. The controller 86 is connected to the engine and continuously monitors load demand and engine speed. All these parameters indicate changes in the air / fuel ratio in the combustor and transient engine conditions that may lead to combustion instability.

[0037] During the operation of the combustion system 16, the combustion monitor 84 monitors pressure fluctuations in the combustion chamber 38 and transmits the pressure fluctuation readings to the controller 86. The combustion monitor 84 continuously transmits the data to the controller 86.

[0038] When the engine starts, fuel is supplied to the ignition injectors 50 in one or more of the burners 36, and the fuel is ignited. The ignition fuel valve 82 is opened. The main fuel valve 80 is closed. When an ignition flame 56 is established in any of the burners 36, and there is a demand for increased engine power, fuel is then supplied to the main injectors 48A, 48B, and the main fuel valve 80 is opened by an amount representing the required power output. When a main flame 58 is established in each burner 36, the controller 86 determines the state of combustion stability in each burner 36, and if the combustion stability is less than a predetermined value, the ignition fuel valve 82 of that burner 36 begins to close and the ignition fuel supply is reduced. The total fuel supply 76 remains constant or has negligible variation, so what would have been the ignition fuel supply is now diverted to the main fuel supply and injected through the main fuel injectors 48A, 48B. Therefore, under constant demand output of combustion system 16 or gas turbine engine 10, when ignition fuel supply 72 is reduced to zero, the total fuel supplied and burned in combustion chamber 38 also remains constant or very close to constant. Each combustion monitor 84 monitors pressure fluctuations in each combustion chamber 38 and transmits the readings to controller 86. Alternatively, combustion monitor 84 monitors pressure fluctuations (burner stability) in the external pressure chamber 35 of combustion chamber 38. Controller 86 is programmed to adjust ignition fuel supply 74 by opening or closing ignition fuel valve 82, which depends in part on pressure fluctuations in each burner 36. Here, any one or more burners 36 can close or open their ignition fuel valve 82 based on their combustion instability. Thus, any one or more burners 36 can operate solely on their main fuel supply and main flame 58, while other burners 36 can operate with ignition fuel supply 72 and main fuel supply, where corresponding ignition flame 56 and main flame 58 are present. However, it is possible that a group of burners 36 or all burners 36 may shut off or open the ignition fuel supply 72 based on the combustion stability of any one or more burners. For example, when the ignition fuel valves of all of a group of burners 36 are closed and a combustion instability threshold or value is reached, all of the group's ignition fuel valves 82 may be opened.

[0039] A gas turbine engine's steady-state condition is characterized by a substantially constant load demand over a period of time, resulting in a substantially constant total fuel supply to the combustor. When the required power output or load changes, for example, by at least 1% of the engine's maximum power output or load, a transient state occurs in the gas turbine engine, and the total fuel supplied to the combustor changes accordingly.

[0040] Although this method of controlling the burner and the fuel flowing to the burner is described as an “additional” to the active ignition control of EP1974139B1 and / or the intelligent control of EP2486328B1, it is not necessary that any of these known methods have been applied, and other control systems to which this method can be applied may be used. As mentioned in the introduction, existing active ignition control—as disclosed in EP1974139B1 and particularly as described with reference to Figure 6 therein—is a steady-state compensation or adjustment for the planned arrangement of the ignition fuel share. The planned arrangement of the ignition fuel share depends on the engine load. Existing active ignition control is designed to accommodate variations in environmental or field conditions or manufacturing tolerances. Active ignition control cannot adequately control the ignition / main fuel flow during load transients. Active ignition control uses the burner temperature, but because temperature is unstable, it may even adjust the ignition / main fuel share incorrectly due to the hysteresis of the temperature response to load changes. This lag means that after a load transient, the ignition fuel share / main fuel share requires a longer time to recover to its level during steady-state conditions, resulting in increased emissions over a longer period. In conjunction with active ignition control as disclosed in EP1974139B1, the intelligent control device of EP2486328B1—particularly as described in Figures 6A and 6B therein—can operate such that the intelligent control device changes the fuel supplied to the burner, i.e., the ignition fuel share, via a signal based on burner temperature and pressure and based on the progress of time. The control device is also configured such that the signal also represents load information indicating the load on the combustion equipment. The intelligent control device aims to maintain the burner temperature below a predetermined maximum temperature limit and to maintain pressure variations within the combustion volume below a predetermined maximum pressure variation limit, while keeping the total fuel supply to the equipment's fuel supply lines substantially constant. The compensation applied to the ignition fuel share in EP2486328B1 is referred to herein as "intelligent control compensation." The steady-state active ignition share compensation control of EP1974139B1 and the intelligent control compensation of EP2486328B1 are referred to herein as "steady-state active ignition share compensation". Therefore, steady-state active ignition share compensation can be active ignition compensation and / or intelligent control compensation applicable to the ignition fuel share.

[0041] This method applies transient share compensation to the ignition fuel share, with or without the aforementioned intelligent control compensation or steady-state active ignition share compensation. The transient share compensation is applied immediately and is proactive in preventing combustion instability. In particular, this method for controlling the burner applies transient share compensation to the methods disclosed in EP1974139B1 and EP2486328B1, the disclosures of which are incorporated herein by reference.

[0042] Now refer to Figure 4 , Figure 4 A flowchart of a method for controlling a burner 100 according to the present invention is shown. Transient share compensation is based on multiple different signals 410 related to engine conditions, particularly multiple different signals 410 indicating transient engine conditions that may lead to an increase in the air-fuel ratio in the burner 16. An increase in the air-fuel ratio can lead to undesirable combustion instability. The application of transient share compensation to the ignition fuel share maintains stable combustion during transient engine conditions. Transient engine conditions are typically due to changes in required output or load and are a phase between a first required output (e.g., 90% of maximum output) and a second required output (e.g., 50% of maximum output), and can even continue after the engine has reached the second required output until combustion has stabilized. The maintenance of stable combustion reduces the likelihood of flame failure and high vibration levels caused by transient engine conditions and instability during the subsequent recovery period from combustion instability.

[0043] Signal 102 from the engine is continuously monitored and forwarded to the engine control unit 86 for processing. The condition of the air-fuel ratio in the combustor of the gas turbine engine is influenced by any one or more of the following: the position of the variable guide vane 90, the position of the blow-off valve 92, the position of the wastegate 94, the fuel energy input rate (in addition to being referred to as total fuel demand), the engine rotational speed demand, or the load demand value. In a preferred embodiment, the control unit 86 is programmed with a schedule for the required positions of the variable guide vane 90, the blow-off valve 92, the wastegate 94, and the required fuel energy input rate, rotational speed, and load demand values. In another embodiment, the physical positions of the variable guide vane 90, the blow-off valve 92, and the wastegate 94 can be used. However, using the required positions provides earlier intervention by transient ignition compensation compared to using feedback from the monitored positions.

[0044] This method of controlling the combustor generates a steady-state value for at least one signal 102 of the conditions listed above, and the one or more signals 102 indicate the steady-state of the engine. The steady-state of the engine can be when the combustor operates with a planned ignition fuel share, or when a steady-state active ignition share compensation is applied to the planned ignition fuel share. Generating the steady-state value of the signal involves feeding the signal into a low-pass or hysteresis filter 104, which has a time constant of at least 1 second, and preferably less than 10 seconds. In most cases, the time constant is in the range of 5 to 7 seconds. The time constant of any particular gas turbine engine can be empirically determined as a result of testing and / or in-service activities.

[0045] A steady-state filter with a smaller time constant than hysteresis filter 104 (e.g., a hysteresis of up to 1 second) can be applied to the total fuel demand step, i.e., before calculating the change in the filter's output relative to the steady-state filter output, in the step where the total amount of fuel supplied to the combustor depends on the gas turbine engine load. This smaller hysteresis filter aims to reduce the possibility of speed "noise" or fluctuations caused by small instabilities, preventing the need for share compensation when the engine operates at a fixed speed or load, especially during steady-state operation.

[0046] Engine control unit 86 continuously monitors engine condition signals 102 and detects changes in at least one signal 102 relative to a steady-state value. When the change in at least one signal 102 relative to a steady-state value exceeds a predetermined limit, engine control unit 86 generates a transient share compensation 108 for the ignition fuel share according to lookup table 106. A separate lookup table 106 exists for each engine condition. Engine control unit 86 then applies the transient share compensation 108 to the ignition fuel share while maintaining the total amount of fuel supplied at any given time. The transient share compensation is applied to the total fuel supply because the total fuel supply is allocated to the ignition fuel supply and the main fuel supply to all combustor units of the gas turbine engine.

[0047] As mentioned, the ignition fuel share is either the planned ignition fuel share or the planned ignition fuel share subject to steady-state active ignition fuel share compensation. When transient share compensation is generated, it is applied in addition to the planned ignition fuel share, or in addition to the planned ignition fuel share subject to steady-state active ignition fuel share compensation. Therefore, the transient share compensation plus the steady-state active ignition fuel share compensation results in the total share compensation. Of course, the total share compensation can be a separate transient share compensation.

[0048] Methods for controlling the burner may also include monitoring combustion instability, monitoring the burner temperature, and applying a steady-state active ignition share compensation to adjust the planned ignition fuel share when the burner temperature exceeds a predetermined value and / or the combustion instability exceeds a predetermined value, in order to create a steady-state ignition fuel share. This is as already discussed and is known from EP1974139B1 and EP2486328B1.

[0049] The method for controlling the combustor includes selecting the largest transient share compensation from all transient share compensations, which are generated based on signals from the gas turbine engine conditions discussed above. The largest transient share compensation is then applied to the ignition fuel share, with or without steady-state active ignition share compensation. Applying transient ignition share compensation involves immediately increasing the ignition fuel share.

[0050] As the difference between input 102 and steady-state signal 104 decreases, the share compensation 108 generated according to lookup table 106 decreases. To prevent the compensation 108 from decreasing too rapidly and causing combustion instability during the recovery period from the transient event due to insufficient ignition share, the maximum rate at which the transient ignition share compensation can be reduced is limited. Once the transient ignition share compensation is zero, the ignition fuel share is either the planned ignition fuel share or the planned ignition fuel share plus the steady-state active ignition share compensation. This rate-limited gradual reduction allows for flame stabilization. Furthermore, when gradually reducing the transient ignition share compensation to zero, it can be reduced at a relatively rapid first rate and then at a relatively slow second rate. This is advantageous because the reduction of the transient share compensation first rapidly limits the size or amount of the ignition flame, thereby limiting emissions, before the slower ramp-down to the steady-state ignition fuel share to prevent any abrupt changes in combustion behavior.

[0051] Lookup table 106 includes a series of transient fuel share values ​​for each engine condition, and this series of transient fuel share values ​​is based on the condition of the gas turbine engine and is linear or non-linear. This series of transient fuel share values ​​can be linearly interpolated between transient fuel share points or values. For example, the angular position of the variable stator blades in a compressor can have a series of transient fuel share values ​​associated with angular values ​​such as 5°, 10°, 15°, 20°, etc. In the case where the actual angular position of the variable stator blades is, for example, 12°, the transient fuel share value will be 40% of the difference between the values ​​at 10° and 15° from the 10° value (2° out of 5° between the corresponding points). A maximum limit can be imposed on the series of transient fuel share values ​​for each engine condition, which can be the smaller of the following: a fixed maximum compensation; and a value determined by the difference between a fixed maximum permissible ignition share with total share compensation and a currently planned ignition share with or without steady-state active ignition share compensation. This is to prevent transient fractional compensation from causing excessively high ignition fractions with little or no benefit, and in some cases, from causing high flame temperatures due to excessively high ignition fraction values, which could lead to long-term damage to engine components.

[0052] Transient share compensation, or in other words, its intervention, is used to maintain stable combustion under increased loads, particularly when bleed-to-inlet is installed, or for variable guide vane regulation in situations where compensation is not applied to the planned ignition fuel share to prevent unstable combustion during load transients. A bleed-to-inlet system includes piping between the compressor and the engine inlet to deliver compressed air to the engine inlet, either to heat the inlet air at very low ambient temperatures or to allow for increased combustion temperatures at lower engine loads, thereby reducing emissions.

[0053] Transient fractional ignition compensation, or in other words, its intervention, maintains stable combustion under reduced loads because the steady-state ignition fractional ignition scheme naturally lags behind engine response, resulting in a lower ignition fractional ignition at any load compared to what would typically be needed for steady-state operation. When the load decreases, emission controls also require time to raise the temperature to compensate, reducing the air-fuel ratio to help maintain stable combustion.

[0054] Transient share compensation responds proactively to prevent potential combustion instabilities and therefore acts according to what the engine needs to do or how the combustor or engine behaves, rather than reacting reactively to combustion instabilities. Consequently, this method of controlling the combustor using transient share compensation responds much faster to improve combustor reliability and reduces steady-state emissions for a period after a transient event compared to any known method, where combustion instabilities are controlled by active steady-state ignition without such transient share compensation during a transient event.

[0055] Another advantage of this method of controlling the burner using transient share compensation is that the total change in signal 102 relative to the steady-state value is received over a time period, rather than reacting to any instantaneous rate of change. This provides an improved response to slower changes in the signal. For example, the closing rate of a purge valve may be relatively slow and below the "rate of change" threshold, but this makes the change detectable over the current time period. This means that the method is less sensitive to noise while allowing for better tuning of the total share compensation for smaller and slower load change events.

[0056] Importantly, a major improvement offered by this method is in engine reliability during transient events that significantly affect the fuel-air ratio within the engine, without adversely impacting steady-state operation. This is particularly important during a wide load range (referred to as the turndown range) where engine emissions are maintained with the aid of a bleed system and / or variable guide vane adjustment, especially where NOx emissions need to be below 15 parts per million.

[0057] All features disclosed in this application (including any appended claims, abstract, and drawings) and / or all steps of any method or process disclosed thereby may be combined in any combination except for combinations in which at least some of such features and / or steps are mutually exclusive.

[0058] Unless otherwise expressly stated, each feature disclosed in this application (including any appended claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose. Therefore, unless otherwise expressly stated, each disclosed feature is merely one example of a general series of equivalent or similar features.

[0059] This invention is not limited to the details of the foregoing one or more embodiments. The invention extends to any novel feature or combination of novel features disclosed in this application (including any appended claims, abstract, and drawings), or to any novel method or process step or combination of novel method or process steps disclosed thereby.

Claims

1. A method for controlling the combustor of a gas turbine engine, The method includes the following steps: The total amount of fuel supplied to the combustor depends on the load of the gas turbine engine; this total fuel amount is allocated into an ignition fuel quantity and a main fuel quantity via an ignition fuel share. The ignition fuel share is the percentage of the ignition fuel amount to the total fuel amount. The method is characterized by comprising: At least one signal monitoring at least one condition of the gas turbine engine. Generate a steady-state value for the at least one signal that indicates the steady-state of the gas turbine engine. Detecting the change of the at least one signal relative to the steady-state value. When the change of the at least one signal relative to the steady-state value exceeds a predetermined limit A transient share compensation is generated for the ignition fuel share based on the lookup table. The transient share compensation is applied to the ignition fuel share while maintaining the total amount of fuel supplied at any point in time.

2. The method for controlling the combustor of a gas turbine engine according to claim 1, wherein, The step of monitoring at least one signal indicating at least one condition of the gas turbine engine is to make the state of the air / fuel ratio in the combustor an indication of the state of the at least one condition, which can be any one or more of the following: The position of the variable guide vane, Location of the vent valve The location of the vent valve, Fuel energy input rate, The required rotational speed of the engine, Load requirement value.

3. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The ignition fuel share is a planned ignition fuel share or a planned ignition fuel share with a stable state of active ignition.

4. The method for controlling the combustor of a gas turbine engine according to claim 3, the method comprising the following steps: Monitoring combustion instability, Monitor the temperature of the burner, and When the predetermined temperature of the burner is exceeded and / or the predetermined value of combustion instability is exceeded, a steady-state active ignition share compensation is applied to adjust the planned ignition fuel share in order to create a steady-state ignition fuel share.

5. The method for controlling the combustor of a gas turbine engine according to any one of claims 1, 2, and 4, wherein, The step of generating a steady-state value for the at least one signal indicating the steady-state of the gas turbine engine includes feeding the at least one signal into a low-pass filter having a time constant of at least 1 second.

6. The method for controlling the combustor of a gas turbine engine according to claim 5, wherein, The low-pass filter has a time constant of less than 10 seconds.

7. The method for controlling the combustor of a gas turbine engine according to claim 6, wherein, The low-pass filter has a time constant in the range of 5 to 7 seconds.

8. A method for controlling the combustor of a gas turbine engine according to any one of claims 1, 2, 4, 6, and 7, the method comprising the steps of: Select the maximum transient share compensation from all generated transient share compensations, and The following steps: The transient share compensation is applied to the ignition fuel share using the maximum transient share compensation among all generated transient share compensations.

9. The method for controlling the combustor of a gas turbine engine according to any one of claims 1, 2, 4, 6 and 7, wherein, The step of applying the transient share compensation to the ignition fuel share includes immediately increasing the ignition fuel share.

10. The method for controlling the combustor of a gas turbine engine according to any one of claims 1, 2, 4, 6 and 7, wherein, When the change of the at least one signal relative to the steady-state value decreases from its peak value The method gradually reduces the transient share compensation, so that if the required share compensation drops to zero, the transient share compensation is reduced to zero.

11. The method for controlling the combustor of a gas turbine engine according to claim 10, wherein the step of gradually reducing the transient share compensation includes a maximum reduction rate having a first maximum reduction rate and a second maximum reduction rate, the first maximum reduction rate being greater than the second maximum reduction rate of the transient active ignition share compensation.

12. The method for controlling the combustor of a gas turbine engine according to any one of claims 1, 2, 4, 6, 7, and 11, wherein, The lookup table includes a series of transient fuel share values ​​for each engine condition. The series of transient fuel share values ​​are based on the condition of the gas turbine engine and are linear or nonlinear.

13. The method for controlling the combustor of a gas turbine engine according to claim 12, wherein, The series of transient fuel share values ​​are linearly interpolated between transient fuel share values.

14. The method for controlling the combustor of a gas turbine engine according to claim 12, wherein, The series of transient fuel share values ​​for each engine condition have a maximum value that cannot be exceeded.

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