JP5670845B2 - Gas turbine fuel control method and fuel control apparatus - Google Patents

Description

  The present invention relates to a fuel control method for a gas turbine for controlling the flow rate of fuel supplied to a combustor of a gas turbine, and in particular, black smoke generated in exhaust during start-up while ensuring sufficient ignition reliability. The present invention relates to a fuel control method and a fuel control apparatus for a gas turbine that can reduce fuel consumption.

  Patent Document 1 listed below discloses an invention relating to a fuel control device for a gas turbine that can achieve low NOx in a regeneration cycle gas turbine. As shown in FIG. 1 of the same document, the fuel control device 31 is a device that supplies fuel to the combustor 9 of the regenerative cycle gas turbine, and a main fuel supply system 39 that supplies main fuel to the combustor 9; A pilot equivalence ratio is determined in accordance with a load signal, and a pilot fuel supply system 41 that variably controls the flow rate of pilot fuel supplied to the combustor 9 based on the equivalence ratio is provided.

JP 2005-147136 A

  In a conventional gas turbine as disclosed in Patent Document 1, a high fuel pressure is required to inject fuel in a good state by a pressure injection nozzle, and reliability with respect to ignition delay is ensured. In general, the amount of fuel that is input tends to increase in order to be able to ignite even if this occurs. For this reason, unburned or incompletely burned fuel is generated at the time of starting, and a large amount of black smoke may be discharged.

  FIG. 7 is a graph showing a fuel control method for a gas turbine previously invented by the present inventor. The horizontal axis represents the time t after the start command, and the vertical axis is allocated with the gas turbine rotation speed, gas turbine exhaust temperature, and fuel flow rate from the top as three quantities that change over time. The change with respect to each time is displayed in three graphs.

  As shown in FIG. 7, when starting the gas turbine, the shaft of the gas turbine is driven by the starter simultaneously with the start command to increase the rotation speed, and the fuel starts almost simultaneously with the start of acceleration of the rotor. Is also performed. The fuel flow rate is constant until the exhaust temperature rises by a predetermined amount (for example, 30 degrees) after ignition in order to obtain a good spray state by the pressure injection nozzle and to enable ignition even if ignition delay occurs. It was controlled so as to increase with the increase of the rotation speed (that is, with the increase of the air amount). For this reason, as shown by the hatched rectangular area in FIG. 7, a large amount of fuel is injected, and black smoke is generated at the start due to unburned or incomplete combustion of this fuel. it is conceivable that.

  FIG. 8 shows the ignition limit line LM of the gas turbine superimposed on the graph of the fuel control method of the gas turbine shown in FIG. 7 in order to explain the reliability against the ignition delay. The ignition limit line LM represents an ignition limit fuel flow rate determined by the structure of the gas turbine and its associated combustor and its operation method, and the upper side of this line is the ignition region, and the lower side is It is a non-ignition area.

  As described above, in this gas turbine, the fuel is supplied at a constant fuel flow rate immediately after the start of startup, and the fuel flow rate is increased after ignition. However, if ignition is not performed at the illustrated ignition point, As shown by the middle broken line, the fuel supply at a constant fuel flow rate is continued, and the exhaust temperature does not rise while maintaining the constant temperature at the start. The time T from the start of fuel supply until the time when this constant fuel flow line crosses the ignition limit line LM is a time range within which ignition is possible, and this inventor has given time margin when ignition is delayed. Considered as a guideline to express, it is called “tolerance for ignition delay”. The longer the tolerance for this ignition delay, the greater the chance of ignition, the higher the possibility of ignition without mistakes, and the higher the reliability of ignition.

  In the case where fuel is supplied at a constant fuel flow rate immediately after the start of startup as in this gas turbine, in order to increase the tolerance (T) to the ignition delay, a constant value of the fuel flow rate supplied immediately after the start of startup is set. Even if the ignition limit line LM rises after a lapse of time, the time at which a constant fuel flow rate crosses the ignition limit line LM and enters the lower non-ignition region is as late as possible. do it. In this gas turbine, while obtaining a good spray state by the pressure injection nozzle and securing the reliability against such ignition delay, a large amount of fuel is introduced at a constant fuel flow rate. Therefore, as described above, it is considered that unburned or incompletely burned fuel was generated at the time of starting and a large amount of black smoke was discharged.

  In order to solve the problem of black smoke generated at the start of the gas turbine, if the constant fuel flow rate of the fuel to be input immediately after the start is set to a smaller value, the amount of unburned or incompletely burned fuel is reduced. Smoke is also expected to decrease, but simply reducing the fuel flow rate will cause the horizontal constant supply line to translate downward in the fuel flow graph shown in the lower part of FIG. The time t at the point of intersection with the limit line LM becomes earlier, and as a result, the tolerance (T) with respect to the ignition delay is shortened and the reliability of ignition is lowered.

  The present invention solves the above problems, and provides a fuel control method and a fuel control device for a gas turbine capable of reducing black smoke generated in exhaust during start-up while sufficiently ensuring the reliability of ignition. It is intended to be realized.

The fuel control method for a gas turbine according to claim 1 comprises:
In a fuel control method for a gas turbine for controlling a flow rate of fuel supplied to a combustor to generate combustion gas for driving a gas turbine,
Assuming an ignition limit line LM that divides the region showing the relationship between the flow rate and time into a fuel ignition region and a non-ignition region at the time of starting the gas turbine in which the rotation speed of the gas turbine increases with the passage of time. A first supply line indicating the relationship between the flow rate and time when fuel is supplied to the engine is set along the ignition limit line LM in the ignition region, and fuel is supplied to the combustor according to the first supply line. It is characterized by.

According to the fuel control method for a gas turbine according to claim 2, the fuel control method for a gas turbine according to claim 1,
Assuming a constant supply line having a predetermined length of ignition possible time and maintaining the flow rate constant until ignition,
The rotation speed of the gas turbine corresponding to the start of fuel supply by the first supply line is set larger than the rotation speed of the gas turbine corresponding to the start of fuel supply by the constant supply line;
The rotational speed of the gas turbine corresponding to when the first supply line crosses the ignition limit line LM is made larger than the rotational speed of the gas turbine corresponding to the constant supply line crossing the ignition limit line LM. It is characterized by being set to.

The fuel control method for a gas turbine according to claim 3 is the fuel control method for a gas turbine according to claim 2,
The control of the flow rate by the first supply line is a control in which the flow rate increases in direct proportion to the proportional coefficient a as time elapses, and after ignition, the flow rate becomes proportional coefficient b as time elapses. Control is performed along a second supply line that increases in direct proportion to (a> b).

A fuel control device for a gas turbine according to claim 4 is provided.
In a fuel control device for a gas turbine for controlling a flow rate of fuel supplied to a combustor via a fuel control valve in order to generate combustion gas for driving the gas turbine,
When starting a gas turbine using a starter in which the rotational speed of the gas turbine increases with the passage of time, an ignition limit line LM that divides the region indicating the relationship between the flow rate and time into a fuel ignition region and a non-ignition region is provided. Assume that a first supply line indicating the relationship between the flow rate and time when fuel is actually supplied is set along the ignition limit line LM in the ignition region, and fuel is supplied to the combustor according to the first supply line. The fuel control valve is controlled to supply the fuel.

  According to the fuel control method for a gas turbine described in claim 1 and the fuel control device for a gas turbine described in claim 4, when the gas turbine is started, the rotational speed of the gas turbine is increased with time. The ignition limit line LM gradually rises with the increase, but the fuel is supplied in accordance with the first supply line set along the ignition limit line LM in the ignition region, so that the fuel is supplied at a constant fuel flow rate after starting. Compared to supply, the amount of fuel input before ignition can be reduced as much as possible, and any ignition within the ignition range will result in ignition close to the ignition limit, making it as lean as possible. Since the combustion is performed under conditions, the amount of unburned or incompletely burned fuel is reduced, and black smoke generated in the exhaust during start-up can be reduced.

  According to the fuel control method for a gas turbine according to claim 2, the fuel supply to the combustor is started according to the first supply line after the fuel supply start of the constant supply line having a constant fuel flow rate. In addition, the fuel supply mode can be set so that the first supply line intersects the ignition limit line LM after the constant supply line intersects the ignition limit line LM. Therefore, compared with the case where fuel is supplied at a constant fuel flow rate after starting, fuel supply start is delayed, the amount of fuel input before ignition can be reduced, and the fuel flow rate shifts to a non-ignition region. Since the time point is also slower than the case of a constant fuel flow rate, it is possible to set the time range in which ignition is possible (tolerance to the ignition delay) to be equal to or greater than that in the case of a constant supply line. The reliability of ignition equal to or higher than that can be secured. That is, it is possible to reduce black smoke generated in the exhaust during start-up while sufficiently ensuring the reliability of ignition.

  According to the fuel control method for a gas turbine described in claim 3, after the gas turbine is started, the fuel flow rate increases linearly in proportion to time in accordance with the first supply line, but can be ignited. When ignition is performed within the time range (tolerance to the ignition delay), the fuel flow rate is supplied with a smaller increase amount according to the second supply line having a smaller slope than the first supply line, so that the first supply line is maintained as it is. As compared with the case where the fuel is supplied along the line, the amount of fuel supply can be reduced while maintaining the combustion state appropriately, and the effect of further suppressing the generation of black smoke can be obtained.

It is a block block diagram which shows the structure and control system of the gas turbine apparatus which concern on embodiment of this invention. It is sectional drawing which shows the structure of the fuel control valve provided in the gas turbine apparatus which concerns on embodiment of this invention. It is sectional drawing in the AA cutting line of FIG. 2, and is a figure which each shows the fully closed state and fully open state of a valve. It is a figure which shows the drive state of the gas turbine apparatus which concerns on embodiment of this invention with the change of the rotation speed of the rotor with respect to time, and the operation state of each part of an apparatus. It is a diagram showing a fuel control method of a gas turbine according to an embodiment of the present invention, the horizontal axis takes time after the start command, the vertical axis is the gas turbine rotational speed that changes with the passage of time, It is the figure which took the gas turbine exhaust temperature and the fuel flow rate, and displayed the change with respect to time of each quantity with three graphs. (A) is the photograph which shows the exhaust condition at the time of start of the gas turbine which concerns on embodiment of this invention, (b) is the exhaust condition at the time of start by the fuel control method of the gas turbine which this inventor invented previously. It is a photograph shown. It is a figure which shows the fuel control method of the gas turbine which this inventor invented previously, Comprising: The time after start command is taken on a horizontal axis, and the gas turbine rotation speed which changes with progress of time on a vertical axis | shaft FIG. 3 is a diagram showing gas turbine exhaust temperature and fuel flow rate, and the change of each amount with respect to time is displayed in three graphs. It is the figure which overlapped and showed the ignition limit line LM of this gas turbine on the graph of the fuel control method of the gas turbine shown in FIG.

The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.
First, with reference to FIG. 1, the whole structure of the electric power generating apparatus using the gas turbine of this embodiment is demonstrated. The gas turbine 1 includes a compressor 3 and a turbine 4 attached to a common rotor 2 that is freely rotatable, and a combustor 5 that supplies combustion gas for driving to the turbine 4. The combustor 5 includes a fuel pump 6 for sending fuel, a fuel control valve 7 for controlling the flow rate of the fuel sent from the fuel pump 6, and a flow path between the fuel control valve 7 and the combustor 5 as required. A fuel supply system indicated by a broken line constituted by a fuel cutoff valve 8 that opens and closes is connected. The fuel pump 6 in this fuel supply system is driven by a battery (not shown) when the gas turbine 1 is started, and fuel supply in a state where the gas turbine 1 is operated at the rated speed is performed by a main pump described later. Done. The combustor 5 is also connected with an air flow path 9 that guides compressed air from the compressor 3. And the ignition plug 10 is provided in the combustor 5, and it can ignite and burn the fuel-air mixture supplied to the combustor 5, and can produce combustion gas. The combustor 5 and the turbine 4 are connected by a combustion gas passage 11, and the combustion gas generated by the combustor 5 is guided to the turbine 4 through the combustion gas passage 11 to drive the rotor 2. Can be rotated.

  A generator 13 is connected to the rotor 2 of the gas turbine 1 configured as described above via a speed reducer 12. When the gas turbine 1 is driven, the rotational force of the rotor 2 is converted to an appropriate rotational speed by the speed reducer 12, and the generator 13 can be driven to obtain electric power. The speed reducer 12 is connected to a starter 14 that is an electric motor that drives the rotor 2 when the gas turbine 1 is started, and is also provided with a rotation speed detection means 15.

  The power generator including the gas turbine 1 and the generator 13 is controlled as a whole by a control unit 20 having a function as a fuel control device. That is, as shown in FIG. 1, the fuel pump 6, the fuel control valve 7, the fuel cutoff valve 8, the spark plug 10, the starter 14, the rotation speed detecting means 15 and the like are connected to the control unit 20, and the control unit Reference numeral 20 denotes a fuel pump 6, a fuel control valve 7, a fuel shut-off valve 8, a spark plug in response to information on the rotational speed obtained from the rotational speed detection means 15, information from other sensors (not shown), and instructions from the outside. 10, each part of the apparatus such as the starter 14 is appropriately controlled, and the fuel flow rate is controlled as described later, so that the power generation by the gas turbine 1 can be performed. Although not shown, as described above, the speed reducer 12 is connected to the main pump that is driven by the rotational force of the rotor 2. The main pump is configured to supply fuel to the combustor 5 in a state where the gas turbine 1 is operated at the rated rotational speed.

  Next, the fuel control valve 7 that supplies fuel to the combustor 5 of the gas turbine 1 will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, an inside of the valve box 25 of the fuel control valve 7 includes an inlet-side flow path 26 connected to the fuel pump 6, and a substantially cylindrical valve chamber 27 communicating with the inlet-side flow path 26. An outlet-side flow path 28 that allows the valve chamber 27 and the fuel cutoff valve 8 to communicate with each other is formed. Inside the valve chamber 27, as shown in FIG. 3, a semi-columnar valve body 29 is provided that is substantially the same shape as the valve chamber 27 and has a slightly smaller cylinder vertically cut in half. The valve body 29 is rotatable about its axis, and is driven by a 4 to 20 mA current signal supplied via the control unit 20 as schematically shown in FIG. The actuator is set at an arbitrary position between the fully open position and the fully closed position, as shown in FIG. 3, and the opening degree of the flow paths 26 and 28 can be arbitrarily adjusted. That is, in this fuel control valve 7, each pressure in the inlet-side flow path 26 and the outlet-side flow path 28 is constant, and the fuel flow rate is continuously adjusted by adjusting the opening degree of the flow path by the valve element 29. It can be adjusted freely.

  As shown in FIG. 2, the flow rate control is stably performed in the valve box 25 of the fuel control valve 7 even when each pressure in the inlet-side flow path 26 and the outlet-side flow path 28 fluctuates due to some load or the like. A pressure compensation mechanism is provided in order to perform the above. A pressure compensation valve 31 is movably provided in the pressure compensation chamber 30, and a bypass pressure PB equal to the pressure P1 of the inlet side flow path 26 is applied to one side thereof, and an outlet side flow is provided to the other side. A pressure P2 in the passage 28 is applied. According to this configuration, the differential pressure between the pressure P1 of the inlet side channel 26 and the pressure P2 of the outlet side channel 28 is controlled to be constant. For example, when the throttle of the fuel valve or the like downstream of the outlet side flow path 28 becomes narrow for some reason, the pressure P2 of the outlet side flow path 28 increases. Therefore, the bypass pressure PB decreases, the amount of fuel bypass decreases, and the fuel flow rate can be kept constant.

  Next, with reference to FIG. 4, the outline of the operation state from the start of the gas turbine 1 to the rated operation in the embodiment will be described. When a start start instruction (start command) is input, the control unit 20 starts the starter 14 with the battery and starts to drive the rotor 2 of the gas turbine 1, and also starts the fuel pump 6 and the spark plug 10 for starting with the battery. Start. When the rotational speed of the rotor 2 rises to a predetermined rotational speed (N% with respect to the rated rotational speed of 100%), the air-fuel mixture in the combustor 5 is ignited, and then the fuel cutoff valve 8 is operated to start. The fuel coming from the system of the fuel pump 6 is cut off. Thereafter, the starter 14, the starting fuel pump 6 and the spark plug 10 are stopped at an appropriate time, but the operation is continued by supplying fuel to the combustor 5 by a main pump (not shown) linked to the speed reducer 12. When the rotational speed is up to 100%, the fuel flow rate is increased in accordance with the amount of air. After the rotational speed reaches 100%, the fuel flow rate is controlled so as to maintain the rotational speed of 100%.

Next, fuel control at the start of the gas turbine 1 described with reference to FIG. 4 will be described in detail with reference to FIG.
In the coordinate system of the graph showing the fuel control method of the present embodiment shown in FIG. 5, the horizontal axis indicates the time t after the start command, and the vertical axis indicates three quantities that change with the passage of time. The gas turbine rotation speed, the gas turbine exhaust temperature, and the fuel flow rate are taken and the change of each quantity with respect to time t is displayed in three graphs. An ignition limit line LM of the combustor 5 of the gas turbine 1 is also shown superimposed on the fuel flow rate graph. This figure is a diagram at the time of starting in which the starter 14 performs control to increase the rotational speed of the rotor 2 of the gas turbine 1, so that the rotational speed of the gas turbine 1 increases as the time t on the horizontal axis increases. The gas turbine exhaust temperature, which was constant after startup, also increases after the ignition point.

  As shown in FIG. 5, when the gas turbine 1 is started, the shaft of the gas turbine 1 is driven by the starter 14 simultaneously with the start command to increase the rotation speed, and the rotation of the rotor 2 is accelerated and rotated. Fuel injection starts after the number rises to some extent. In the case of the prior invention of the present inventor shown in FIG. 7, as described above, the supply of fuel is started almost at the same time as the rotation of the rotor starts to be accelerated and the air amount is relatively small. It was. On the other hand, in the present embodiment, the fuel supply is started after the time t1 when the air amount is higher than that at the later time.

  Thus, in the present embodiment, the fuel supply start time is delayed compared to the case of the inventor's prior invention, and the fuel supply is started at time t1 when the rotation speed is higher and the air amount is larger. Fuel that tends to become unburned when supplied with a small amount of air is reduced, and black smoke is less likely to be generated.

  As shown in FIG. 5, in the present embodiment, an actual fuel is supplied by assuming an ignition limit line LM that divides a region indicating a relationship between an elapsed time after start of start and a fuel flow rate into a fuel ignition region and a non-ignition region. The first supply line L1 indicating the relationship between the flow rate and the time to be set was set as a straight line (with an inclination a) along the ignition limit line LM in the ignition region. The first supply line L1 has a constant flow rate at the last part and becomes horizontal, and intersects the ignition limit line LM. The time interval between the time t2 at the intersection and the time t1 at which the fuel supply is started is ignited. Tolerance to delay (T). This margin (T) is equivalent to the case of the prior invention of the present inventor whose fuel supply starts earlier than the present embodiment, and the reliability of ignition is sufficiently ensured.

  The power generator using the gas turbine 1 as in the present embodiment is often installed for emergency use, and in that case, in view of the urgency of the application, it is ignited as much as possible at the start and immediately starts power generation. Performance is required. That is, the temporal ignition possible range is wide, the tolerance (T) to the ignition delay is long, and the reliability for ignition is important. According to this embodiment, it can be said that it has ignition reliability that can sufficiently meet such demands and expectations.

  As described above, in this embodiment, although the timing of fuel supply is delayed, the tolerance (T) to the ignition delay is equivalent to that of the prior invention and sufficient reliability is provided. This is because the fuel flow rate of the embodiment is not constant, and the flow rate control along the first supply line L1 in which the flow rate linearly increases along the ignition limit line LM in the ignition region is employed.

  In addition, according to the present embodiment, the first supply line L1 whose flow rate increases linearly along the ignition limit line LM in the ignition region is adopted as the fuel control schedule. Regardless of the ignition point, the ignition is always performed under a lean condition close to the ignition limit, so that there is an effect of reducing black smoke.

  Further, according to the present embodiment, as described above, the fuel supply is started after the rotation speed increases and the air amount increases, and the fuel is further supplied according to the first supply line L1 along the ignition limit line LM. Therefore, while ensuring the margin (T) equivalent to that of the preceding invention, the total amount of fuel injected before ignition is smaller than in the conventional case, as shown by the hatched trapezoidal region in FIG. As described above, in addition to the fact that the amount of fuel supplied in a state where there is little air is small and that the ignition is always performed by lean combustion, the fuel supply amount before ignition itself within the ignitable time range (tolerance (T)) is Since it is less than that of the prior invention, the amount of unburned / incompletely burned fuel is reduced in this respect as well, and the generation of black smoke is reduced.

  As shown in FIG. 5, in the present embodiment, after the ignition point, the fuel control according to the first supply line L1 is maintained until the exhaust temperature rises by a predetermined amount (for example, 30 degrees). The fuel flow rate is controlled according to the second supply line L2, which has a lower rate of increase in fuel flow rate than the first supply line L1. That is, the second supply line L2 indicates a fuel control schedule in which the flow rate increases in direct proportion to the proportionality coefficient b (a> b).

  According to the present embodiment, after the gas turbine 1 is started, the fuel flow rate increases linearly in proportion to the time according to the first supply line L1, but the time range in which ignition is possible (the tolerance for the ignition delay). In the case of ignition within (degree (T)), the fuel flow rate is supplied with a smaller increase amount in accordance with the second supply line L2 having a smaller slope than the first supply line L1. There is no problem even if the second supply line L2 enters the non-ignition region below the ignition limit line LM since it is once ignited. Therefore, compared with the case where the fuel is supplied as it is along the first supply line L1, it is possible to reduce the amount of fuel supplied while maintaining the combustion state appropriately. can get.

  The ignition limit line LM in the embodiment described above is a characteristic that can vary depending on the gas turbine, the operation method, and the like. Therefore, for example, the structure of the duct in the gas turbine 1 is changed, so that the resistance of air supply or exhaust changes, or the temperature of the fuel when supplied to the combustor 5 fluctuates and the degree of atomization fluctuates. A case where the ignition limit line LM itself that has become the basic data for setting the first supply line L1 changes may be considered. Accordingly, if the first supply line L1 is set too close to the ignition limit line LM, if the ignition limit line LM fluctuates as described above for any reason, the actual fuel flow rate will become the ignition limit line LM. It is conceivable that an ignition mistake will occur below this value. Therefore, the first supply line L1 is not provided so as to be close to the ignition limit line LM over the entire range of the tolerance T in the ignition region, but is separated from the ignition limit line LM as time elapses from the start of supply. You may set to go. Or you may perform control which increases a fuel flow rate gradually, seeing the generation | occurrence | production state of the black smoke after ignition.

  As described above, according to the present embodiment, the fuel supply start by the first supply line L1 is delayed as compared with the case of the prior invention, and the fuel supply is started at a higher rotational speed (a larger air amount). The first supply line L1 that is a fuel control line is a line that increases along the ignition limit line LM in the ignition region, so that the time when the first supply line L1 intersects the ignition limit line LM The final stage of the margin (T) for the ignition delay of the first supply line L1 was set to a higher rotational speed (a larger amount of air) than in the case of the prior invention. For this reason, with respect to the ignition delay, while securing a sufficient value as in the case of the prior invention, the fuel supply in a state with less air is reduced, the total amount of fuel input until ignition is reduced, and the ignition is reduced. Since the condition that is always performed in a lean condition was adjusted, the effect of reducing unburned and incomplete combustion and reducing black smoke at the start was obtained.

  FIG. 6 is a photograph showing the state of the flue when the gas turbine 1 is operated at a rotation speed of 20% of the rated fuel using special A heavy oil, and FIG. 6A is a fuel control method according to the embodiment. The black smoke is not seen at all in the exhaust from the flue. FIG. 4B is a photograph showing the case of the fuel control method according to the inventor's prior invention, in which black smoke is discharged from the flue.

DESCRIPTION OF SYMBOLS 1 ... Gas turbine 5 ... Combustor 7 ... Fuel control valve 14 ... Starter 20 ... Control part as a fuel control device LM ... Ignition limit line L1 ... 1st supply line L2 ... 2nd supply line

Claims (4)

In a fuel control method for a gas turbine for controlling a flow rate of fuel supplied to a combustor to generate combustion gas for driving a gas turbine,
Assuming an ignition limit line that divides the region showing the relationship between the flow rate and time into a fuel ignition region and a non-ignition region at the start of the gas turbine, where the rotational speed of the gas turbine increases with the passage of time. A first supply line indicating the relationship between the flow rate and time when fuel is supplied is set along the ignition limit line in the ignition region, and fuel is supplied to the combustor according to the first supply line. A gas turbine fuel control method. Assuming a constant supply line having a predetermined length of ignition possible time and maintaining the flow rate constant until ignition,
The rotation speed of the gas turbine corresponding to the start of fuel supply by the first supply line is set larger than the rotation speed of the gas turbine corresponding to the start of fuel supply by the constant supply line;
The rotation speed of the gas turbine corresponding when the first supply line intersects the ignition limit line is set to be larger than the rotation speed of the gas turbine corresponding when the constant supply line intersects the ignition limit line. The fuel control method for a gas turbine according to claim 1, wherein: The control of the flow rate by the first supply line is a control in which the flow rate increases in direct proportion to the proportional coefficient a as time elapses, and after ignition, the flow rate becomes proportional coefficient b as time elapses. 3. The fuel control method for a gas turbine according to claim 2, wherein control is performed along a second supply line that increases in direct proportion to (a> b). In a fuel control device for a gas turbine for controlling a flow rate of fuel supplied to a combustor via a fuel control valve in order to generate combustion gas for driving the gas turbine,
Assuming an ignition limit line that divides the region showing the relationship between the flow rate and time into a fuel ignition region and a non-ignition region when starting a gas turbine using a starter in which the rotational speed of the gas turbine increases with time. Then, a first supply line showing the relationship between the flow rate and time when fuel is actually supplied is set along the ignition limit line in the ignition region, and fuel is supplied to the combustor according to the first supply line. A fuel control device for a gas turbine, characterized in that the fuel control valve is controlled as described above.