JP2001263095A - Method for controlling gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow continuous evasion operation while suppressing load fluctuation of a gas turbine to the minimum, when abnormal combustion such as a counterflow of flame and misfiring is generated in the gas turbine having a two-stage type low NOX combustor. SOLUTION: A ratio of a fuel flow rate supplied to the second stage combustion part to total fuel flow rate supplied to the combustor is changed to continue the operation, when the abnormal combustion is detected, while monitoring a combustion state of the combustor or the gas turbine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage combustion unit having a first stage combustion unit performing diffusion combustion and a second stage combustion unit performing premix combustion.
The present invention relates to a method for controlling a gas turbine including a staged combustor.

[0002]

2. Description of the Related Art A gas turbine having a plurality of two-stage combustors, which is generally employed, is a first type in which diffusion combustion is performed.
It has a stage combustion unit and a second stage combustion unit in which premix combustion is performed. One of the features of this type of gas turbine combustor is the fuel-air ratio from startup to rated load,
That is, the change range of the ratio between the fuel amount and the air amount is very wide.

[0003] A gas turbine having a two-stage combustor is a system capable of achieving low NOx even in this very wide range of changes in the fuel-air ratio. And that is achieved by fuel control. That is, in the first stage combustion section used from the start to the rated load,
A diffusion combustion system with a wide operating range is adopted, and thereafter, from single combustion in the first stage combustion section to simultaneous combustion in the second stage combustion section and the first stage combustion section in order to reduce NOx even in a high load area. And the combustion state is shifted.

[0004] In the second stage combustion section where the amount of generated NOx is small, the change in the NOx concentration is sensitive to the fuel-air ratio and the stable combustion range is narrow. Is finely controlled.

[0005] However, the combustion is delicately changed due to a difference in the individual combustors, a change in the temperature and humidity of the combustion air, or a change in the calorific value and composition of the fuel. In particular, when disturbance such as a transient foreign substance is mixed in the fuel or air supplied to the combustor, the combustion state of the combustor transiently changes greatly, and a stable combustion state may not be maintained. .

In such a case, even if the secondary fuel, which is the fuel of the second-stage combustion section, is injected into the second-stage combustion section, the fire from the first-stage combustion section to the second-stage combustion section is prevented. There was a risk that the secondary fuel would not ignite due to the transfer failure, or the flame of the second stage combustion section would be lost. Conversely, there is also a risk that the flame of the second-stage combustion section may flow backward, causing the section to burn out.

[0007] As a method of avoiding such abnormal combustion, hitherto, as shown in Japanese Patent Application Laid-Open No. 7-54671, for example, a backflow flame detection sensor is installed in a premixing duct and a second stage ( Main) A configuration in which the downstream of the fuel distribution valve of the fuel system is branched, a fuel switching valve is provided in each of the branched flow paths, and a spare fuel hole for ejecting the switching fuel is provided in the first stage (pilot) fuel nozzle. When the backflow flame is detected, the fuel switching valve is controlled so that at least a part of the second-stage fuel passes through the branch flow path and is injected from the spare fuel hole of the first-stage fuel nozzle, and the extinguishing of the backflow flame is detected. Then, a control method is known in which the set value is changed so as not to reproduce the flashback equivalent ratio and return to normal operation.

[0008]

In the above-mentioned prior art, not only the structure of the fuel system and the structure of the first-stage fuel nozzle become complicated, but also when a flashback is detected, a branch which has not been used before. Since new fuel is supplied to the pipes and fuel nozzle holes, the time delay before the branch fuel starts burning (the time when the branch pipe is filled with fuel and the ignition time of the branch fuel) and the failure of the branch fuel ignition For example, there is a possibility that a load change will occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a gas turbine control method capable of suppressing a load fluctuation of a gas turbine even when abnormal combustion occurs. To provide.

[0010]

In order to achieve the above object, a method of operating a gas turbine according to the present invention comprises a first stage combustor having a plurality of combustors, wherein the combustors perform diffusion combustion. A method for controlling a gas turbine comprising a second stage combustion section performing mixed combustion, wherein a combustion state of a combustor or a gas turbine is monitored, and when abnormal combustion is detected, all fuels supplied to the combustor. The operation is continued by changing the ratio of the flow rate of the fuel supplied to the second stage combustion section to the flow rate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of a gas turbine according to one embodiment of the present invention.

As shown in FIG. 1, the two-stage combustor 1 has a first-stage combustion unit 2 for performing diffusion combustion and a second-stage combustion unit 3 for performing premix combustion. In the gas turbine having the two-stage combustor as in the present embodiment, even when the change in the fuel-air ratio from the start to the rated load, that is, the change in the ratio of the fuel amount and the air amount is very wide, , Low NOx can be achieved. That is, in the present embodiment, in order to achieve low NOx, the first stage combustion unit 2 used from the start to the rated load employs a diffusion combustion system having a wide operating range. Single combustion by the first stage combustion section 2 and then low NO even in a high load range
In order to achieve x, the combustion state is shifted to the simultaneous combustion of the second stage combustion unit 3 and the first stage combustion unit 2 employing the premixed combustion system.

In controlling the fuel-air ratio, the fuel side includes a first-stage combustion fuel valve 4a and a second-stage combustion fuel valve provided in a fuel system for charging the two-stage combustor 1 with fuel. 4
adjusted by b. The first-stage combustion fuel valve 4a
Is installed in a first-stage combustion section fuel supply system 4x for supplying fuel to the first-stage combustion section 2 of the two-stage combustor 1, and the second-stage combustion fuel valve 4b is Is installed in the second stage combustion section fuel supply system 4y that supplies fuel to the fuel cell.

On the other hand, the air side is implemented by a variable blade called an inlet guide blade 6 provided on the inlet side of the air compressor 5. Normally, during the gas turbine load operation, the fuel valves 4a, 4b and the inlet guide vanes 6 are adjusted by a signal from the control device 7 according to the required amount of required load, and a stable combustion state can be maintained. The fuel / air ratio is adjusted. However, as described above, while it is necessary to appropriately adjust the fuel-air ratio over a wide range, combustion depends on the individual differences in the combustor, changes in the temperature and humidity of the combustion air, or the calorific value and components of the fuel. Changes subtly due to the change of. In particular, when disturbance such as a transient foreign substance is mixed in the fuel or air supplied to the combustor, the combustion state of the combustor is greatly changed transiently, and the backflow or flame of the second stage combustion section is increased. An abnormal combustion state such as loss may occur.

These abnormal combustion states are measured by a plurality of exhaust gas temperature measuring thermocouples 9 installed in the circumferential direction on the exhaust side of the turbine section 8 shown in FIG. The temperature can be obtained from the measurement result based on the output of the combustor metal temperature measuring thermocouple 11, the combustor internal pressure sensor 12, or the generator 13 installed in the premixer 10 located in the combustion section 3. In addition to the above, as means for confirming the abnormal combustion state, there are gas temperature in the combustor, gas temperature in the pipe around the combustor, metal temperature in the pipe around the combustor, which have the same tendency as the above measurement site. Can be

The signal from the detector is sent to the control device 7 to be used for judging an abnormal combustion state. When it is determined that the backflow of the flame has occurred in the second stage combustion unit 3 due to the signal of the detector exceeding the allowable value, the first stage combustion fuel valve 4a and the second stage combustion fuel valve 4b , The ratio of the fuel flow rate supplied to the second stage combustion section 3 to the total fuel flow rate supplied to the combustor is reduced, and the operation is continued with the same load setting. Conversely, when it is determined that flame loss has occurred in the second-stage combustion section 3, the valve openings of the first-stage combustion fuel valve 4a and the second-stage combustion fuel valve 4b are adjusted and supplied to the combustor. The ratio of the flow rate of the fuel supplied to the second stage combustion section 3 to the total flow rate of the fuel is increased, and the operation is continued with the same load setting. Thereafter, the state quantity returns to within the allowable value,
Alternatively, when a predetermined time has elapsed, the control amount is automatically returned to the pre-abnormality set value assuming that the control amount has been avoided from the abnormal state.

FIG. 2 is a block diagram for controlling the fuel ratio of the present embodiment in the control device 7 shown in FIG.

The fuel ratio control of the combustor is performed by premixing (second
Stage) The fuel ratio setting 18a is given as a function of the fuel control signal 14, and the premix fuel flow ratio reduction bias signal 42 and the premix fuel flow ratio increase bias signal 43 are corrected by the subtractor 15 and the adder 16. The fuel control signal 14 is further multiplied by a multiplier 17 to generate a second-stage fuel control signal 20. The first-stage fuel control signal 21 is created by subtracting the second-stage fuel control signal 20 from the fuel control signal 14 by the subtractor 15. Therefore, the second stage fuel control signal 20 and the first stage fuel control signal 21
Will always coincide with the fuel control signal 14.
Further, the first-stage combustion fuel valve opening signal 22 is provided by the function generator 18b as a function of the first-stage fuel control signal 21, and the second-stage combustion fuel valve opening signal 23 is provided by the second
Function generator 18 as a function of stage fuel control signal 20
given by c.

Referring to FIG. 1, a method of correcting the premixed fuel ratio during abnormal combustion will be described below. First, regarding the flame backflow, the thermocouple 1 attached to the second stage combustion part of each combustor was used.
Taking in the combustor metal temperature 24 detected by 1;
Any one of the permissible temperature, the fluctuation range, and the change rate of each of the actual measured values of the combustor metal temperature is calculated by the arithmetic unit 25.
When it is determined from a to 25c that the value exceeds the preset allowable value, it is regarded as abnormal combustion, and signals 26, 27, and 28 for detecting abnormal combustion are issued. Further, the arithmetic unit 29
, A high combustor metal temperature signal 30 is issued when a limit condition provided by transmission from any of the signals 26, 27, and 28 that detect abnormal combustion or a combination thereof is satisfied.

Similarly, a combustor gas temperature detected by a thermocouple attached to each combustor is taken in, and although not shown in FIG. If any of the rate of change is judged to exceed the allowable value, it is regarded as abnormal combustion, and if the limit condition provided by the transmission of the abnormal signal or the combination thereof is satisfied, the high combustor gas temperature signal Issue 31.

Similarly, a combustion oscillation signal detected by a combustor internal pressure sensor 12 attached to each combustor is fetched, and one of its absolute value, fluctuation width, and rate of change is calculated.
If it is judged that the allowable value has been exceeded, it is regarded as abnormal combustion,
When the limit condition provided by the transmission of the abnormal signal or the combination thereof is satisfied, a high combustor internal pressure fluctuation signal 32 is issued.

Further, a limit provided by the arithmetic unit 29 by transmission from any one of the high combustor metal temperature signal 30, the high combustor gas temperature signal 31, and the high combustor internal pressure fluctuation signal 32, or a combination thereof. When the condition is satisfied, a flame backflow determination signal 37 is issued. When the flame backflow determination signal 37 is transmitted, the premixed fuel flow ratio reduction bias signal 42 is switched by the switch 40 from the signal 0% from the signal generator 41 to the function of the fuel control signal 14 by the function generator 18d. The mixed fuel ratio is reduced by the amount of the premixed fuel flow ratio reduction bias signal 42.

Next, regarding the loss of the flame, the plurality of combustors installed in the circumferential direction on the exhaust side of the gas turbine and the gas temperature of the combustor detected by the thermocouple 11 attached to the second stage combustion section of each combustor. The exhaust gas temperature detected by the exhaust gas temperature measuring thermocouple 9 and the generator output signal are taken in, and the absolute value, the fluctuation width, and the change rate are omitted in the same manner as the combustor metal temperature, which is omitted in FIG. Is determined to be an abnormal combustion, and if the limit condition provided by the transmission of the abnormal signal or the combination thereof is satisfied, the combustor metal temperature low signal 33, A low combustor gas temperature signal 34, a large gas turbine exhaust gas temperature deviation signal 35 and a low generator output signal 36 are issued.

Further, in the arithmetic unit 29, transmission from any one of the above-mentioned combustor metal temperature low signal 33, combustor gas temperature low signal 34, gas turbine exhaust gas temperature deviation large signal 35 and generator output low signal 36, or When the restriction condition provided by the combination is satisfied, a flame loss determination signal 38 is issued. Flame loss judgment signal 3
8, the premixed fuel flow ratio increase bias signal 43 is switched by the switch 40 from the signal 0% from the signal generator 41 to the function of the fuel control signal 14 by the function generator 18e, and the premixed fuel ratio is reduced. The amount is increased by the amount of the mixed fuel flow rate increase bias signal 43.

Here, if the premixed fuel ratio is adjusted by the bias, abnormal combustion is avoided, and the flame backflow judging signal 37 or the flame loss judging signal 38 is reset. In consideration of the setting, the timer is reset after being held for a predetermined time α by the time delay / off timer 39. When the signal is reset, the switch 40 switches from the function of the fuel control signal 14 by the function generators 18d and 18e to the signal 0% from the signal generator 41, and the premixed fuel flow ratio reduction bias signal 42
Alternatively, the premixed fuel ratio increase bias signal 43 becomes 0, and the premixed fuel ratio automatically returns to the pre-abnormal set value.

Further, as an extra protection in a case where abnormal combustion is not avoided even if the premixed fuel ratio is adjusted by the bias for some reason, the flame delay determination signal 37 or the flame backflow determination signal 37 is provided by the time delay / on timer 44 for a predetermined time β. If the flame loss determination signal 38 is not reset, a run-back signal 45 to the first stage independent combustion load is issued to lower the load and completely shut off the second stage combustion fuel.

As described above, according to the present embodiment, in a gas turbine having a two-stage combustor, when a combustion abnormality such as flame backflow and flame loss occurs, the second
By changing the ratio of the fuel supplied to the stage combustion section, abnormal combustion can be avoided while minimizing the load fluctuation of the gas turbine without complicating the fuel system configuration and the like.

In addition, since abnormal combustion such as flashback often occurs due to temporary disturbance such as mixing of foreign matter, in the prior art,
When the operation is performed with the set value changed so as to avoid the fuel flow condition in which the flashback occurs, there is a possibility that the tolerance for the loss of the flame may be reduced during the normal operation in which the disturbance is eliminated. On the other hand, in the present embodiment, in the above-mentioned operation state, the state quantity indicating the combustion state of the combustor or the gas turbine is monitored, and if it is confirmed that there is no problem in the device, the initial operation state is set back to the set value. It is possible to quickly return to the normal operation state.

From the above, there is an effect that the reliability and operability of the two-stage low NOx combustor are improved.

The backflow of the flame and the flame loss (blown out) in the premixed combustion occur due to an imbalance between the flow rate of the premixed gas and the combustion speed. In other words, when the combustion speed is high relative to the premixed gas flow velocity, the flame flows backward and reverses the flow of the premixed air. It is washed away and blows away. Therefore, it is possible to recover by reducing the fuel-air ratio of the premixed gas at the time of flame backflow and lowering the combustion speed, and conversely, it is possible to achieve stable combustion again by raising the fuel-air ratio and increasing the combustion speed. Become.

To eliminate flashback in the second stage combustion section, a second
When it is necessary to almost shut off the stage fuel and switch the majority of the second stage fuel to the first stage combustion section, a new fuel branch pipe as in the prior art is used due to the limitation of the capacity of the first stage combustion nozzle. Also, it is necessary to provide a spare fuel hole in the first stage fuel nozzle. However, when most of the second-stage fuel is switched to the first-stage combustion section, the NOx discharged from the gas turbine
The amount becomes very large, and it becomes necessary to reduce the load to reduce NOx, and it is difficult to continuously operate the load at the same load.

Therefore, as a result of examining the amount of change in the fuel-air ratio necessary for eliminating abnormal combustion, it was found that a change of about 10% was effective, and it was not necessary to add a new branch fuel system, and the fuel was not added. It has been found that the ratio can be changed. It should be noted that with such a change, the change in NOx is not large, and continuous operation is possible.

For the above reasons, in the present embodiment, in a gas turbine having a two-stage combustor, the first-stage combustion unit is used as a control method when a combustion abnormality occurs particularly in the second-stage combustion unit where combustion tends to be unstable. And the continuous operation with the flow rate ratio of the fuel supplied to the second stage combustion section changed, so that the total fuel flow rate does not change and further a new branch fuel system is not added. There is no time delay, and as a result, load fluctuations hardly occur.

When a flame backflow occurs, the fuel flow ratio in the second-stage combustion section is reduced, so that the fuel-air ratio in the second-stage combustion section is reduced and the combustion speed is reduced. It becomes possible. Conversely, when the flame is lost, increasing the fuel flow rate in the second-stage combustion section increases the fuel-air ratio in the second-stage combustion section and increases the combustion speed, thereby enabling stable combustion again. Here, although the fuel-air ratio also changes in the first stage combustion section due to the change in the fuel flow rate ratio, the stable combustion margin is wide due to diffusion combustion, and a stable combustion state can be maintained.

The detection of abnormal combustion is based on the detection of the backflow of the flame in the second stage combustion section, such as the rapid rise in metal temperature and gas temperature around the combustor (particularly in the premixer) and fluctuations in the combustor internal pressure (combustion oscillation). Due to an increase or the like, a change in the combustion state of the combustor can be detected.

Conversely, regarding the loss of flame in the second stage combustion section,
It is possible to detect a change in the combustion state of the combustor due to a sharp drop in the metal temperature and gas temperature around the combustor (particularly in the premixer), and to detect a part of a plurality of combustors provided in the gas turbine. In the case where flame loss occurs in the combustor, the combustion gas temperature of each combustor will vary, so the measurement values of a plurality of exhaust gas temperature measurement thermocouples installed in the circumferential direction on the turbine exhaust side It can be detected by a deviation (temperature difference between a thermocouple indicating the highest temperature and a thermocouple indicating the lowest temperature). Further, in the case where the flame loss occurs simultaneously in the second stage combustion sections of all the combustors, the deviation of the measured value of the thermocouple for measuring the exhaust gas temperature hardly increases, but the combustion efficiency decreases, so that the gas turbine output sharply increases. It can be detected by a significant decrease.

Conditions for judging an abnormal state include at least one of an absolute value, a fluctuation range or a change rate of the state quantity,
Alternatively, the determination can be made by using any combination thereof. Furthermore, since abnormal combustion is mainly caused by temporary disturbance, if the avoidance from abnormal combustion is confirmed by continuous operation after the above-mentioned fuel flow rate change, or if a predetermined time has elapsed, the control amount is reduced. By automatically returning to the set value before the occurrence of the abnormality, it is possible to quickly return to normal operation.

[0038]

As described above, according to the present invention, it is possible to provide a gas turbine control method capable of suppressing a load fluctuation of the gas turbine even when abnormal combustion occurs.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a gas turbine according to an embodiment of the present invention.

FIG. 2 is a control block diagram according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 2 stage type combustor, 2 ... 1st stage combustion part, 3 ... 2nd stage combustion part, 4a ... 1st stage combustion fuel valve, 4b ... 2nd stage combustion fuel valve, 5 ... air compressor, 6 inlet guide vane, 7 control device, 8 gas turbine, 9 exhaust gas temperature measurement thermocouple,
10: Premixer, 11: Thermocouple for measuring combustor metal temperature, 12: Combustor internal pressure sensor, 13: Generator, 14: Fuel control signal, 15: Subtractor, 16: Adder, 17: Multiplier, 18 Function generator 19 Second stage fuel flow ratio 2
0: second stage fuel control signal, 21: first stage fuel control signal,
22: first-stage combustion fuel valve opening signal, 23: second-stage combustion fuel valve opening signal, 24: combustor metal temperature, 25a-
25c arithmetic device, 26, 27, 28 signal, 29 arithmetic device, 30 high combustor metal temperature signal, 31 high combustor gas temperature signal, 32 high combustor internal pressure fluctuation high signal, 33
Combustor metal temperature low signal, 34 ... Combustor gas temperature low signal, 35 ... Gas turbine exhaust gas temperature deviation large signal, 36 ...
Generator output low signal, 37: flame backflow judgment signal, 38: flame loss judgment signal, 39: time delay / off timer,
Reference numeral 40: switch, 41: signal generator, 42: premixed fuel flow ratio decreasing bias signal, 43: premixed fuel flow ratio increasing bias signal, 44: time delay on timer, 45: run to single stage single combustion load Back signal.

Claims (9)

[Claims] A method for controlling a gas turbine, comprising: a plurality of combustors; a first stage combustor in which the combustors perform diffusion combustion; and a second stage combustion unit in which premix combustion is performed. If the abnormal combustion is detected by monitoring the combustion state of the gas turbine or the gas turbine, the operation is continued by changing the ratio of the fuel flow rate supplied to the second stage combustion section to the total fuel flow rate supplied to the combustor. A method for controlling a gas turbine. 2. A method for controlling a gas turbine, comprising a plurality of combustors, the combustor having a first stage combustor performing diffusion combustion, and a second stage combustion unit performing premix combustion. If the abnormal combustion is detected by monitoring the combustion state of the gas turbine or the gas turbine, the operation is continued by changing the ratio of the fuel flow rate supplied to the second stage combustion section to the total fuel flow rate supplied to the combustor. In addition, when the abnormal combustion is not detected while the operation is continued in that state, or when a predetermined time has elapsed in the above state, control is performed to return to the control state before the abnormal combustion was detected. A method for controlling a gas turbine, comprising: 3. A method for controlling a gas turbine, comprising: a plurality of combustors, wherein the combustor includes a first-stage combustor performing diffusion combustion and a second-stage combustion unit performing premix combustion. The state quantity of the combustion state of the burner or the gas turbine is monitored, and when the state quantity exceeds an allowable value, abnormal combustion is considered, and the second fuel flow rate to the total fuel flow supplied to the combustor is regarded as abnormal combustion.
When the operation is continued while changing the ratio of the fuel flow rate supplied to the stage combustion section, and when the state quantity returns within the allowable value while the operation is continued in that state, or when a predetermined time has elapsed in the above state In addition, control is performed such that the control amount of the fuel supplied to the first-stage combustor and the second-stage combustion unit is returned to a set value before the abnormal combustion is considered as being avoided from abnormal combustion. Gas turbine control method. 4. The gas turbine control method according to claim 2, wherein when it is determined that a flame backflow has occurred in the second stage combustion unit as abnormal combustion, the second stage combustion unit with respect to the total fuel flow supplied to the combustor. 4. The method according to claim 1, wherein control is performed to reduce a ratio of a flow rate of fuel supplied to the gas turbine. 5. The control method for a gas turbine according to claim 2, wherein when it is determined that flame loss has occurred in said second stage combustion section as abnormal combustion, said second stage combustion section relative to the total fuel flow supplied to said combustor. The control method for a gas turbine according to claim 1, 2 or 3, wherein control is performed to increase a ratio of a flow rate of fuel supplied to the gas turbine. 6. The gas turbine control method according to claim 1, wherein the state quantity includes a gas temperature or a metal temperature around the combustor or the combustor, a pressure fluctuation in the combustor, an exhaust gas temperature of the gas turbine, or a gas turbine. The method according to claim 3, wherein at least one of the outputs or a combination thereof is monitored. 7. The method for controlling a gas turbine according to claim 1, wherein the condition for determining the abnormal state of the state quantity is at least one of an absolute value, a fluctuation range, or a rate of change of the state quantity, or a combination thereof. The method for controlling a gas turbine according to claim 3, wherein: 8. A method for controlling a gas turbine, comprising: a combustor having a first stage combustor performing diffusion combustion and a plurality of second stage combustion units installed for performing premix combustion. The state quantity of the combustion state of the two-stage combustor is monitored, and when the state quantity of at least one of the second-stage combustors exceeds a permissible value, it is regarded as abnormal combustion and supplied to the combustor. The operation is continued by changing the ratio of the fuel flow rate supplied to the second stage combustion section to the total fuel flow rate to be performed, and when the state quantity returns to within the allowable value while the operation is continued in that state, or If a predetermined time has elapsed in the state, the first
A method for controlling a gas turbine, comprising: performing control for returning a control amount of fuel supplied to a stage combustor and a second stage combustion unit to a set value before the abnormal combustion is considered. 9. The method for controlling a gas turbine according to claim 1, wherein when a flame backflow is detected in said second stage combustion section as abnormal combustion,
When the ratio of the fuel supply amount to the first stage combustion unit to the total fuel supply amount to be supplied to the combustor is increased from the state before the detection of the flame backflow, when the flame loss is detected in the second stage combustion unit, The control method for a gas turbine according to claim 8, wherein control is performed such that a ratio of a fuel supply amount to the first stage combustion unit to a total fuel supply amount supplied to the first stage is reduced from a state before the flame loss detection.