Method of controlling a burner

Abstract

A method for controlling a combustor of a gas turbine engine, the method comprising the steps of: supplying a total fuel quantity to the combustor according to the load of the gas turbine engine, the total fuel quantity being divided into an ignition fuel quantity and a main fuel quantity by a pre-arranged ignition fuel quantity, the ignition fuel quantity being a percentage of the ignition fuel quantity in the total fuel quantity; monitoring combustion instability; applying a steady-state active ignition share compensation to the pre-arranged ignition fuel quantity to generate a steady-state ignition fuel quantity when a predetermined temperature of the combustor is exceeded and / or a predetermined value of combustion instability is exceeded; monitoring the gas turbine engine's influence on the air / fuel ratio in the combustor; disabling the steady-state active ignition share compensation when the gas turbine engine's condition indicates a transient condition and when a threshold of combustion instability is exceeded; and applying a transient active ignition share compensation to the steady-state ignition fuel quantity while maintaining a total fuel quantity supply at any point in time, wherein the transient active ignition share compensation and the steady-state active ignition share compensation generate a total share compensation, the total share compensation being greater than the steady-state active ignition share compensation, and the rate of change of the transient active ignition share compensation being faster than the rate of change of the steady-state active ignition share compensation.

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. Inside the combustion chamber, the pilot flame and main flame are distinct, although they interact, as is well 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 pre-programmed 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 pre-arranged 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 accommodate changes in conditions experienced during steady-state operation, i.e., constant load demand. Such changes 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 proportion of main fuel supply and ignition fuel supply to the burner based on signals based on burner temperature and pressure and 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 line 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 time occupied by compensation applied to the pilot fuel portion, increase the rate of compensation applied to the pilot fuel portion, improve combustor dynamics and reduce pressure fluctuations in the combustion chamber, improve combustion stability and limit combustion component temperature, thereby reducing the impact of transient combustion instability on the steady-state emissions, especially nitrogen oxides, of gas turbine engines. Furthermore, the present invention reduces the adverse effects on emissions under steady-state operation in the period following a transient event and can reduce instability or flame failure events during load transients or recovery from load transients.

[0009] The above objective is achieved by a method for controlling the combustor of a gas turbine engine, the method comprising the following steps:

[0010] The total fuel quantity supplied to the combustor is determined based on the gas turbine engine load. This total fuel quantity is divided into an ignition fuel quantity and a main fuel quantity by controlling a pre-arranged ignition fuel share. The pre-arranged ignition fuel share is the predetermined proportion of fuel supplied to the ignition fuel supply and the main fuel supply. The pre-arranged ignition fuel share is the initial proportion of the total fuel supplied during steady-state operation to minimize emissions and maximize efficiency under ideal and stable conditions. Here, the main flame is as lean as possible, i.e., the air / fuel ratio is as high as possible, while minimizing the ignition flame to ensure combustion stability. The ignition flame is more richly burned than the main flame; in other words, the ignition flame has a lower air / fuel ratio. The ignition fuel share is the proportion of the ignition fuel quantity to the total fuel quantity.

[0011] - Monitor combustion instability,

[0012] When the burner's predetermined temperature and / or the predetermined value for combustion instability are exceeded, a steady-state active ignition share compensation is applied to the ignition fuel share to generate a steady-state ignition fuel share. The steady-state active ignition share compensation is automatically adjusted.

[0013] - Monitor the effects of the gas turbine engine on the air / fuel ratio in the combustor.

[0014] - When the gas turbine engine condition indicates a transient condition and the combustion instability threshold is exceeded, the adjustment of the steady-state active ignition share compensation is disabled, and

[0015] - A transient active ignition share compensation is applied to the steady-state ignition fuel share while maintaining the total fuel supply at any point in time. The transient active ignition share compensation and the steady-state active ignition share compensation result in a total share compensation.

[0016] -The total share compensation is greater than the share compensation for active ignition in a stable state, and

[0017] - The rate of change of transient active ignition share compensation is faster than the rate of change of steady-state active ignition share compensation. In other words, if steady-state active ignition share compensation remains active, the rate of change of transient active ignition share compensation is faster than the rate of change of steady-state active ignition share compensation.

[0018] The threshold for combustion instability in transient active ignition share compensation and the predetermined value for steady-state active ignition share compensation are implemented as separate values, even though they are both set to the same actual value. This allows the transient condition response to be tuned to a higher or lower value if necessary to improve combustion stability without affecting steady-state emission control.

[0019] The following points should be noted:

[0020] -The steady-state ignition fuel share is the sum of the pre-arranged ignition fuel share and the steady-state active ignition share compensation;

[0021] -The ignition fuel share is the sum of the steady-state ignition fuel share and the transient active ignition share;

[0022] - The pre-scheduled ignition fuel share is never disabled. This is merely an adjustment to the active ignition share compensation during a steady-state condition, not a complete elimination of compensation. This method stops adjusting the steady-state compensation for combustion instability / for reducing emissions or for high burner temperatures (e.g., burner tip temperatures).

[0023] - Steady-state share compensation is adjusted in response to high burner temperatures or combustion instability, and steady-state compensation is always present.

[0024] Preferably, when the condition of the gas turbine engine indicates a stable state or when the combustion instability is below a predetermined value for combustion instability, the transient active ignition share compensation is reduced to zero, and the adjustment of the stable state active ignition share compensation is reactivated to adjust the ignition fuel share while maintaining the total fuel supply at any point in time.

[0025] The conditions affecting the air / fuel ratio in the combustor of a gas turbine engine 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-off valve, the fuel energy input rate, the engine rotation speed requirement, and the load requirement value.

[0026] The maximum value of the ignition fuel share with steady-state active ignition share compensation and / or transient active ignition share compensation can be in the range of 2% to 85%, preferably in the range of 40% to 85%, and more preferably in the range of 60% to 65%.

[0027] The pre-arranged ignition fuel share can range from 2% to 80%, preferably from 5% to 25%, and more preferably from 5% to 15%.

[0028] The active ignition share compensation in steady state can be in the range of -5% to 5%, preferably in the range of -2% to 2%.

[0029] When combustion instability exceeds a threshold, the transient active ignition share compensation can be in the range of 0.01% to 25%, preferably in the range of 1% to 25%, and more preferably in the range of 2% to 10%.

[0030] By applying transient active ignition share compensation to a pre-arranged ignition fuel share while maintaining a total fuel supply at any point in time, transient active ignition share compensation can keep the ignition fuel share in the range of 2% to 80%, preferably in the range of 5% to 15%.

[0031] The transient active ignition share compensation is applied at a rate ranging from 0.1% to 5% per second, preferably at a rate ranging from 0.5% to 1.0% per second.

[0032] When combustion instability exceeds a threshold, there is a confirmation delay before active ignition share compensation control and transient active ignition share compensation are applied to the ignition fuel share overshoot steady state, while maintaining the total fuel supply at any point in time. The confirmation delay is in the range of 0.1 mbar-second to 10 mbar-second, preferably 4 mbar-second to 5 mbar-second, and the confirmation delay is an inverse error-time delay, wherein the delay decreases as the overshoot exceeds the threshold.

[0033] The threshold for combustion instability can be the amplitude of pressure fluctuations within a set frequency band of combustion. The threshold for combustion instability can be a value between 15 mbar and 50 mbar, preferably between 24 mbar and 34 mbar.

[0034] The method includes the following steps: when combustion instability is below a threshold, setting a ramp reduction delay before reducing the transient active ignition share compensation. Preferably, this step occurs when combustion instability has fallen below the threshold after already being above it.

[0035] The ramp reduction delay can be a value between 0.1 seconds and 5 seconds, preferably between 2 seconds and 3 seconds.

[0036] The method includes the following steps: reducing the transient active ignition share compensation at a rapid ramp descent rate when the transient active ignition share remains above a slow ramp descent rate activation threshold, and / or reducing the transient active ignition share compensation at a slow ramp descent rate when the transient active ignition share compensation is below a slow ramp descent rate activation threshold.

[0037] The rapid slope reduction rate can be in the range of 0.1% to 5% per second, preferably in the range of 0.5% to 1.0% per second.

[0038] The slow ramp descent rate can be in the range of 0.01% to 1% per second, preferably in the range of 0.2% to 0.3% per second.

[0039] The slow ramp reduction rate activation threshold can be in the range of 1% to 10%, preferably in the range of 2% to 5%.

[0040] The method may include the following steps: when both the transient share compensation and the transient active ignition share compensation used for transient conditions are no longer higher than the maximum amount used for the active ignition share in steady state, the active ignition share in steady state is enabled. Attached Figure Description

[0041] The above-mentioned 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 burner and operating method disclosed herein will be better understood.

[0042] Figure 1 A portion of the turbine engine is shown in cross-sectional view, and the combustion system according to this disclosure is incorporated into the turbine engine.

[0043] Figure 2 This is a schematic cross-section of the burner through the combustion system of the gas turbine according to the present invention.

[0044] 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.

[0045] 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

[0046] Figure 1 This is a schematic 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 comprises 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.

[0047] The terms radial, circumferential, and axial are relative to the engine's axis of rotation 26, or, as otherwise stated, 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.

[0048] Compressor 14 includes an axially arranged series of stator blades and rotor blades mounted in a conventional manner. As is well known, stator or compressor blades can be fixed or have variable geometry to improve airflow to the downstream rotor or compressor blades. Each turbine 28, 30 includes an axially arranged series of stator blades and rotor blades. The stator blades can be mounted to a radial housing or radial inner cylinder. The rotor blades are mounted via rotor disks arranged and operated in a conventional manner. The rotor assembly includes blades or annular arrays of rotor blades and rotor disks.

[0049] Each burner 36 consists of two walls—an inner wall 37 and an outer wall 39—defining a generally annular space or pressurized chamber 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, which will be described in more detail later. Following the swirler 40 is a pre-combustion 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.

[0050] 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 into 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 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.

[0051] 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.

[0052] Reference Figure 1The 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, twin-shaft, and triple-shaft engines used in marine, industrial, and aerospace applications.

[0053] Figure 2 This is a cross-sectional view through a portion of one of the combustors 36 in a group of combustors of the turbine engine 10 according to the invention described above. The radial vortex 40 includes an annular array of blades 46 arranged around a combustor axis 44, and the annular array of blades 46 is at a tangential angle relative to the combustor axis 44 to impart a vortex flow 55 to the mixed air and fuel, as is well known. Figure 2 As seen, the vortex flow 55 rotates around 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.

[0054] 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.

[0055] 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.

[0056] Figure 3 This 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 through 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 can be controlled by a controller 86. Each burner 36 has at least one combustion monitor 84, and these combustion monitors 84 are each connected to the controller 36.

[0057] Controller 86 is connected to, monitors, and controls the positions of the variable guide vane, the blow-through valve, and the bleed-through valve. The positions of the variable guide vane, the blow-through valve, and the bleed-through valve are continuously monitored by controller 86. These positions are pre-programmed according to engine conditions and are generally operated routinely. Controller 86 is connected to the engine and continuously monitors the load demand value and engine rotational speed. All these parameters indicate changes in the air / fuel ratio in the combustor and transient engine conditions that may lead to combustion instability. In a preferred embodiment, control unit 86 is programmed with pre-programmed demand positions for the variable guide vane 90, the blow-through valve 92, the bleed-through valve 94, and the demanded fuel energy input rate, the demanded rotational speed, and the load demand value. In another embodiment, the physical positions of the variable guide vane 90, the blow-through valve 92, and the bleed-through valve 94 can be used. However, using the demand positions provides earlier intervention by compensation for transient active ignition compared to using feedback from the monitored positions.

[0058] 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.

[0059] 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, representing the amount of power required. 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.

[0060] 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.

[0061] Now refer to Figure 4 , Figure 4A flowchart of a method for controlling a burner 100 according to the present invention is shown. As mentioned in the introduction, existing active ignition control—such as that disclosed in EP1974139B1—depends on a steady-state compensation or trimming of the pre-arranged ignition fuel share based on engine load and is designed to accommodate variations in environmental or field conditions or manufacturing tolerances. Active ignition control cannot adequately control the ignition fuel flow / main fuel flow during load transients. Active ignition control uses burner temperature, but because temperature is unstable and due to the hysteresis in the temperature response to load changes, active ignition control may even adjust the ignition fuel share / main fuel share incorrectly. This means that after a load transient, the ignition fuel share / main fuel share requires a longer time to recover to its proper level, resulting in increased emissions over a longer period. In conjunction with the active ignition control disclosed in EP1974139B1, the control device of EP2486328B1 is operable such that the control device changes the fuel supplied to the burner, i.e., the ignition fuel share, based on a signal based on the burner's 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 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 total fuel supply in the fuel supply line to the equipment. The compensation applied to the ignition fuel share in EP2486328B1 is referred to herein as "intelligent control compensation." Both 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 applied to the ignition fuel share.

[0062] This invention overrides or disables adjustments to steady-state compensation, such as those imposed by the steady-state active ignition share compensation control of EP1974139B1 or the intelligent control device of EP2486328B1, during transient engine conditions and when combustion instability thresholds are exceeded. When steady-state engine conditions are evident, or when combustion instability is below the threshold, the transient active ignition share compensation for the pre-arranged ignition fuel share is overridden or disabled, thereby enabling steady-state active ignition share compensation control.

[0063] "Steady-state active ignition compensation" is a steady-state compensation applicable to a pre-arranged ignition fuel share used in the existing active ignition control of EP1974139B1.

[0064] "Transient share compensation" is a compensation applied in addition to steady-state compensation as an active measure to prevent combustion instability in gas turbine engines under transient conditions.

[0065] "Transient active ignition share compensation" is a compensation applied in addition to steady-state active ignition share compensation as an active measure to reduce combustion instability in the following situations: when combustion instability is detected after the above transient share compensation has been applied; and when the combustion instability exceeds a set threshold, in which case intervention by existing steady-state active ignition share compensation control is no longer effective or desirable.

[0066] This method of controlling the burner is generally indicated as 100. Initially, as... Figure 4 As shown, the method includes the following steps: supplying a total fuel quantity to the burner, and applying a steady-state active ignition share compensation to a pre-arranged ignition fuel share when the burner's predetermined temperature and / or predetermined combustion instability is exceeded. Due to the control of the ignition fuel share, the total fuel quantity is divided into an ignition fuel quantity and a main fuel quantity. The ignition fuel share is the percentage of the ignition fuel quantity to the total fuel quantity at any given time.

[0067] The predetermined temperature is the burner temperature and indicates the state of the combustion flame. Predetermined values ​​for combustion instability range from 15 mbar to 50 mbar, with typical values ​​ranging from 24 mbar to 34 mbar. These values ​​are absolute values. This predetermined value can be at a predetermined frequency of combustion pressure fluctuations. This predetermined value is within combustion chamber 38, but if monitored outside the combustion chamber, such as within pressurization chamber 35, it can be a relative value.

[0068] Method 100 monitors the conditions affecting the air / fuel ratio in the combustor of a gas turbine engine. As described above, these conditions 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 blow-off valve, the engine's rotational speed and load requirements, or the fuel energy input rate, which can be calculated based on the fuel's calorific value and the required total fuel flow rate. This monitoring is continuous and real-time.

[0069] In steps 110 and 112, transient active ignition control is activated when the gas turbine engine condition indicates a transient condition and when combustion instability exceeds an instability threshold. The transient condition is indicated by transient share compensation, which is applied for multiple conditions of the gas turbine engine that may affect the air-fuel ratio in the combustor, and when the transient share compensation exceeds a transient share compensation threshold for steady-state active ignition control. The transient condition of the gas turbine engine may be indicated by any one or more of the following:

[0070] The position of the variable guide vane is opening, meaning the variable guide vane is in a more open position, and the "demand" for the variable guide vane is decreasing.

[0071] The air blowing valve is closing, meaning it's in a more closed position, and the demand for air is decreasing.

[0072] The vent valve is closing, meaning it's in a more closed position, and the demand for vent valve power is decreasing.

[0073] The fuel energy input rate, measured in kW / s, is decreasing, and the engine's rotational speed requirement is decreasing; and

[0074] The load demand is decreasing.

[0075] The instability threshold for combustion instability ranges from 15 mbar to 50 mbar, with typical values ​​ranging from 24 mbar to 34 mbar. Combustion instability is the fluctuation of pressure within the combustion chamber. Although pressure can be measured outside the combustion chamber, in this case, as will be apparent to a technician, the pressure fluctuation outside the combustion chamber is relative to the pressure fluctuation within the combustion chamber.

[0076] The transient share compensation threshold for enabling transient active ignition control is in the range of 0.01% to 5%, with a preferred value in the range of 0.01% to 2%. For example, the pre-arranged ignition fuel share can be 25% when steady-state compensation is applied; if the transient share compensation threshold is, for example, 2%; therefore, the threshold for enabling transient active ignition control is a 27% ignition fuel share.

[0077] The pre-arranged ignition fuel share has a practical range of 2% to 80%, although most engines will typically have a pre-arranged ignition fuel share in the range of 5% to 25%, with the most frequent operations in the range of 5% to 15%. Steady-state active ignition share compensation is in the range of -5% to 5%, preferably in the range of -2% to 2%. Transient active ignition share compensation is in the range of 1% to 25%, and most commonly in the range of 2% to 10%. In extreme cases, transient active ignition share compensation can be in the range of 0.01% to 25%. When transient active ignition share compensation is applied to the pre-arranged ignition fuel share, the ignition fuel share can be in the range of 2% to 80%, but most commonly in the range of 5% to 15%.

[0078] After enabling transient active ignition control, there is a delay in steps 114 and 116 to confirm that the instability is real and persistent, thus requiring the application of an additional ignition fuel fraction. If the instability falls below the instability threshold within this delay, active ignition fraction control does not require intervention. The confirmation delay is in the range of 0.1 mbar-second to 10 mbar-second, preferably 4 mbar-second to 5 mbar-second; the confirmation delay is an inverse error-time delay, wherein the delay decreases as the overshoot exceeds the threshold, in order to respond more quickly to larger instabilities.

[0079] When the delay is confirmed in step 116, if the transient active ignition share compensation in step 118 is lower than the current transient share compensation applicable to the transient situation, then in step 120 the transient active ignition share compensation is initialized to the current transient share compensation.

[0080] While maintaining combustion instability above a threshold in step 112, transient active ignition share compensation is then increased at a fixed rate in step 122, thereby increasing the ignition fuel share to improve combustion stability. This fixed rate ranges from 0.1% / s to 5% / s, with a preferred value in the range of 0.5% / s to 1% / s. Simultaneously, control of steady-state active ignition share compensation is disabled in step 122.

[0081] Transient engine conditions have been detected, and transient active ignition share compensation has been set to adjust the total ignition fuel share to the correct value very quickly to reduce the effects of transient combustion instability and vibrations that may subsequently cause flame failure.

[0082] Once the combustion instability is no longer above the threshold of intervention by transient active ignition share compensation in step 112, method 100 waits for a set delay in steps 126 and 128 to allow time for the combustion to acceptably stabilize before reducing the transient active ignition share compensation, so as to return to normal stable operation. This delay before reducing the transient active ignition share compensation ranges from 0.1 seconds to 5 seconds, and is typically in the range of 2 seconds to 3 seconds.

[0083] Once the set delay is completed in step 128, the transient active ignition share compensation is gradually reduced to zero to restore the normal stable operation of the gas turbine engine 10.

[0084] In step 130, this gradual reduction to zero of the transient active ignition share compensation can be performed at a rapid ramp-down rate (step 132) or a slow ramp-down rate (step 134) – as determined by whether the transient active ignition share compensation is greater than a slow ramp-down rate activation threshold. The slow ramp-down rate activation threshold has a value ranging from 1% to 10% of the total fuel quantity, with a typical value ranging from 2% to 5%, for example, 2.5% of the total fuel quantity.

[0085] In step 132, when the transient active ignition share compensation is greater than the slow ramp descent rate activation threshold, the fast ramp descent rate is in the range of 0.1% / s to 5% / s, with a typical value in the range of 0.5% / s to 1% / s.

[0086] In step 134, when the transient active ignition share compensation is less than or equal to the slow ramp reduction rate activation threshold, the slow ramp reduction rate is in the range of 0.01% / s to 1% / s, with a typical value in the range of 0.2% / s to 0.3% / s.

[0087] The slow ramp reduction threshold for any gas turbine engine can be set during engine commissioning and for the specific characteristics of any single engine, and can be adjusted during use.

[0088] Once the transient active ignition share compensation is reduced below the maximum compensation used for steady-state operation in step 110 by the reduction that occurred in step 132 or 134, steady-state active ignition share compensation control is reactivated in step 124.

[0089] In step 136, the maximum share compensation is determined at any given moment for any share of compensation to be limited. The maximum share compensation is the lower of the following two:

[0090] a) A predetermined maximum or fixed maximum for transient active ignition share compensation, and it is in the range of 10% to 25%, with a typical value in the range of 15% to 20%, and

[0091] b) The maximum ignition fuel share compensation is determined by the difference between the currently pre-arranged share with which steady-state active ignition share compensation is applied and the allowed set maximum ignition share with which transient active ignition share compensation is also applied, and it is in the range of 40% to 85%, with a typical value in the range of 60% to 65%.

[0092] In step 138, the transient active ignition share compensation is compared with the maximum share compensation.

[0093] In step 140, if the transient active ignition share compensation is higher than the maximum share compensation in step 138, then the maximum share compensation is applied to the transient active ignition share compensation. The determination and application of the maximum share compensation has the effect of reducing the allowable maximum value of the transient active ignition share compensation at a higher pre-arranged ignition fuel share, while the transient ignition fuel share compensation applied to the pre-arranged ignition fuel share at a higher pre-arranged ignition fuel share has a smaller effect. A higher pre-arranged ignition fuel share occurs at lower gas turbine engine output, for example, below 40% of the maximum engine output power.

[0094] The pre-arranged ignition fuel share has an absolute minimum and maximum range of 2% to 80%, with the most frequent range being 5% to 25%, and the most frequent range being 5% to 15%.

[0095] Since the control should never impose a negative ignition fuel share compensation, a minimum limit of zero is imposed on the transient active ignition share compensation in step 142.

[0096] Method 100 is repeated continuously, starting at 110 and starting again once step 142 is completed.

[0097] 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.

[0098] 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.

[0099] 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 fuel quantity supplied to the combustor is determined according to the load of the gas turbine engine. This total fuel quantity is divided into an ignition fuel quantity and a main fuel quantity through a pre-arranged ignition fuel share. The ignition fuel share is the percentage of the ignition fuel amount to the total fuel amount. Monitoring combustion instability, 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 the pre-arranged ignition fuel share to generate a steady-state ignition fuel share. The steady-state active ignition share compensation is automatically adjusted. Its features are, The gas turbine engine is monitored to assess its impact on the air / fuel ratio in the combustor. When the gas turbine engine condition indicates a transient condition and exceeds a combustion instability threshold, the adjustment of the steady-state active ignition share compensation is disabled. A transient active ignition share compensation is applied to the steady-state ignition fuel share while maintaining the total fuel supply at any point in time. The transient active ignition share compensation and the steady-state active ignition share compensation produce a total share compensation. The total share compensation is greater than the steady-state active ignition share compensation, and The rate of change of the transient active ignition share compensation is faster than the rate of change of the steady-state active ignition share compensation.

2. The method for controlling the combustor of a gas turbine engine according to claim 1, wherein, When the condition of the gas turbine engine indicates a stable state or when the combustion instability is below a predetermined value for combustion instability, The transient active ignition share compensation is reduced to zero, and the steady-state active ignition share compensation adjustment is reactivated to adjust the pre-arranged ignition fuel share while maintaining the total fuel supply at any point in time.

3. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The gas turbine engine's influence on the air / fuel ratio in the combustor is any one or more of the following: The position of the variable guide vane, The location of the air blowing valve, The location of the vent valve, Fuel energy input rate, The required rotational speed of the engine, Load requirement value.

4. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The maximum value of the ignition fuel share with the applied steady-state active ignition share compensation and / or the transient active ignition share compensation is in the range of 2% to 85%.

5. The method for controlling the combustor of a gas turbine engine according to claim 4, wherein, The maximum value of the ignition fuel share with the applied steady-state active ignition share compensation and / or the transient active ignition share compensation is in the range of 40% to 85%.

6. The method for controlling the combustor of a gas turbine engine according to claim 5, wherein, The maximum value of the ignition fuel share with the applied steady-state active ignition share compensation and / or the transient active ignition share compensation is in the range of 60% to 65%.

7. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The pre-arranged ignition fuel share is in the range of 2% to 80%.

8. The method for controlling the combustor of a gas turbine engine according to claim 7, wherein, The pre-arranged ignition fuel share is in the range of 5% to 25%.

9. The method for controlling the combustor of a gas turbine engine according to claim 8, wherein, The pre-arranged ignition fuel share is in the range of 5% to 15%.

10. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The active ignition share compensation in the steady state is in the range of -5% to 5%.

11. The method for controlling the combustor of a gas turbine engine according to claim 10, wherein, The active ignition share compensation in the steady state is in the range of -2% to 2%.

12. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, When combustion instability exceeds the threshold, the transient active ignition share compensation is in the range of 0.01% to 25%.

13. The method for controlling the combustor of a gas turbine engine according to claim 12, wherein, The transient active ignition share compensation is in the range of 1% to 25%.

14. The method for controlling the combustor of a gas turbine engine according to claim 13, wherein, The transient active ignition share compensation is in the range of 2% to 10%.

15. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, Includes the following steps: A transient active ignition share compensation is applied to the pre-arranged ignition fuel share, while maintaining the total fuel supply at any given time. The transient active ignition share compensation keeps the ignition fuel share in the range of 2% to 80%.

16. The method for controlling the combustor of a gas turbine engine according to claim 15, wherein, The transient active ignition share compensation keeps the ignition fuel share in the range of 5% to 15%.

17. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The transient active ignition share compensation is applied at a rate ranging from 0.1% to 5% per second.

18. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The transient active ignition share compensation is applied at a rate ranging from 0.5% to 1.0% per second.

19. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, When combustion instability exceeds the threshold, there is a confirmation delay before the active ignition share compensation control of the stable state is relaxed and transient active ignition share compensation is applied to the pre-arranged ignition fuel share, while maintaining the supply of the total fuel amount at any point in time. The confirmation delay is in the range of 0.1 mbar-second to 10 mbar-second, and the confirmation delay is an inverse error-time delay, wherein the delay decreases as the overshoot exceeds the threshold.

20. The method for controlling the combustor of a gas turbine engine according to claim 19, wherein, The confirmation delay is in the range of 4 mbar-second to 5 mbar-second.

21. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The threshold for combustion instability is the amplitude of pressure fluctuations within a set frequency band of combustion.

22. The method for controlling the combustor of a gas turbine engine according to claim 21, wherein, The threshold for combustion instability is a value between 15 mbar and 50 mbar.

23. The method for controlling the combustor of a gas turbine engine according to claim 22, wherein, The threshold for combustion instability is a value between 24 mbar and 34 mbar.

24. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The method includes the following steps: When the combustion instability is below the threshold, a ramp reduction delay is set before reducing the transient active ignition share compensation.

25. The method for controlling the combustor of a gas turbine engine according to claim 24, wherein, The ramp reduction delay is a value between 0.1 seconds and 5 seconds.

26. The method for controlling the combustor of a gas turbine engine according to claim 25, wherein, The slope reduction delay is a value between 2 and 3 seconds.

27. The method for controlling the combustor of a gas turbine engine according to claim 24, wherein, The method includes the following steps: When the transient active ignition fuel share remains above the slow ramp descent rate activation threshold, the transient active ignition share compensation is reduced at a fast ramp descent rate, and / or When the transient active ignition share compensation is lower than the slow ramp descent rate activation threshold, the transient active ignition share compensation is reduced at the slow ramp descent rate.

28. The method for controlling the combustor of a gas turbine engine according to claim 27, wherein, The rapid slope descent rate is in the range of 0.1% to 5% per second, and The slow slope descent rate is in the range of 0.01% to 1% per second, and The slow ramp reduction rate activation threshold is a value in the range of 1% to 10%, which is higher than the steady-state ignition fuel share.

29. The method for controlling the combustor of a gas turbine engine according to claim 28, wherein, The rapid slope descent rate is in the range of 0.5% to 1.0% per second. The slow ramp descent rate is in the range of 0.2% to 0.3% per second, and / or The slow ramp reduction rate activation threshold is a value in the range of 2% to 5%, which is higher than the steady-state ignition fuel share.

30. The method for controlling the combustor of a gas turbine engine according to any one of claims 1 to 2, wherein, The method includes the following steps: When both the transient active ignition share compensation and the transient share compensation used for the transient situation are no longer higher than the maximum amount used for the steady-state active ignition share control, the steady-state active ignition share is activated.

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