Gas turbine control device, gas turbine control method, and program

Abstract

Even as the temperature of the sweep air begins to rise, the goal is to prevent the gas turbine from tripping while avoiding self-ignition of the fuel gas. [Solution] The system includes a temperature acquisition unit that acquires the temperature of the sweep air supplied to a pilot nozzle when the pilot nozzle is performing premixed injection in the case of premixed combustion or diffusion injection in the case of diffusion combustion, when the pilot nozzle is performing premixed injection, a determination unit that determines whether or not to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition unit, and a fuel supply control unit that, if the determination unit determines not to maintain operation of the gas turbine based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition unit, reduces the load on the gas turbine within the range of the permissible operating load range that is permitted when operating the gas turbine.

Description

Technical Field

[0001] The present disclosure relates to a control device for a gas turbine, a control method for a gas turbine, and a program.

Background Art

[0002] In a gas turbine with fuel gas combustion, a gas turbine capable of switching between premixed combustion and diffusion combustion is known. In the pilot nozzle of this gas turbine, the injection holes for diffusion that inject fuel gas during diffusion combustion are provided near the tip of the pilot nozzle, so they are closest to the combustion gas generated by the combustion of the fuel gas.

[0003] During premixed combustion, the injection holes for diffusion in the pilot nozzle do not inject fuel gas. Therefore, there is a risk that high-temperature combustion gas will flow backward from these injection holes for diffusion and cause the pilot nozzle to burn out. Therefore, by supplying the air extracted from the combustion chamber of the combustor as sweep air to the fuel supply path leading to the injection holes for diffusion of the pilot nozzle, the sweep air is made to flow out from the injection holes for diffusion of the pilot nozzle to prevent the combustion gas from flowing backward.

[0004] When switching from diffusion combustion to premixed combustion, the supply of fuel gas to the fuel supply path leading to the injection holes for diffusion of the pilot nozzle is stopped and sweep air is supplied. Even when the supply of fuel gas is stopped, fuel gas remains in the fuel supply path. Therefore, there is a timing when the remaining fuel gas and the supplied sweep air come into contact.

[0005] When switching from premixed combustion to diffusion combustion, the supply of sweep air to the fuel supply path leading to the injection holes for diffusion of the pilot nozzle is stopped and fuel gas is supplied. Even when the supply of sweep air is stopped, sweep air remains in the fuel supply path. Therefore, in this case as well, there is a timing when the remaining sweep air and the supplied fuel gas come into contact.

[0006] At these times, if the temperature of the swept air is above the autoignition temperature of the fuel gas, there is a risk that the fuel gas will ignite when the swept air comes into contact with it. Therefore, it is necessary to lower the temperature of the swept air to a temperature at which the fuel gas will not autoignite. For example, Patent Document 1 discloses a technique for cooling the swept air extracted from the combustion chamber using a cooling means. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2012 / 057282 [Overview of the project] [Problems that the invention aims to solve]

[0008] When supplying the amount of electricity required by the power transmission system, it is common practice to operate a gas turbine continuously for a long period of time in a premixed combustion state. During this long period of operation, a malfunction may occur in the cooling system, such as a lack of cooling water flow, causing the temperature of the sweep air to exceed the autoignition temperature of the fuel gas. In this case, if the system is switched from premixed combustion to diffusion combustion, for example, to reduce the load on the gas turbine or to shut down the gas turbine, the fuel gas will autoignite.

[0009] To prevent the self-ignition of the fuel gas, for example, a mechanism can be used to automatically trip the gas turbine when it detects that the temperature of the sweep air exceeds the self-ignition temperature of the fuel gas. Here, tripping the gas turbine means immediately stopping the supply of fuel gas to the gas turbine, thereby stopping its operation as quickly as possible. By stopping the supply of fuel gas to the gas turbine, contact between the fuel gas and the sweep air is prevented, thus preventing the self-ignition of the fuel gas. However, tripping the gas turbine can damage the hot parts of the gas turbine, and the rapid reduction in the gas turbine's power generation has a significant impact on the power transmission system.

[0010] This disclosure has been made to solve the above problems and aims to provide a gas turbine control device, a gas turbine control method, and a program that prevent the gas turbine from tripping as much as possible while avoiding autoignition of the fuel gas even when the temperature of the sweep air begins to rise. [Means for solving the problem]

[0011] To solve the above problems, the gas turbine control device according to the present disclosure includes: a temperature acquisition unit that acquires the temperature of the sweep air supplied to a pilot nozzle when the pilot nozzle is performing either premixed injection in the case of premixed combustion or diffusion injection in the case of diffusion combustion; a determination unit that determines whether or not to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition unit; and a fuel supply control unit that, if the determination unit determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that it will not maintain operation of the gas turbine, reduces the load of the gas turbine within the range of the permissible operating load range that is permissible when operating the gas turbine.

[0012] The gas turbine control method according to this disclosure involves, when a pilot nozzle that injects fuel gas in either premixed injection for premixed combustion or diffusion injection for diffusion combustion is performing the premixed injection, acquiring the temperature of the sweep air supplied to the pilot nozzle, determining whether to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the acquired sweep air temperature, and if it is determined not to maintain operation of the gas turbine based on the operating feasibility determination temperature and the acquired sweep air temperature, reducing the load of the gas turbine within the range of the permissible operating load range that is permitted when operating the gas turbine.

[0013] The program relating to this disclosure causes a computer to function as a temperature acquisition means for acquiring the temperature of sweep air supplied to a pilot nozzle when the pilot nozzle, which injects fuel gas in either premixed injection in the case of premixed combustion or diffusion injection in the case of diffusion combustion, is performing the premixed injection; a determination means for determining whether or not to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition means; and a fuel supply control means for reducing the load of the gas turbine within the range of the permissible operating load range that is permissible when operating the gas turbine, if the determination means determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition means, that the operation of the gas turbine should not be maintained. [Effects of the Invention]

[0014] According to the gas turbine control device, gas turbine control method, and program of this disclosure, even when the temperature of the sweep air begins to rise, it is possible to avoid self-ignition of the fuel gas and prevent the gas turbine from tripping as much as possible. [Brief explanation of the drawing]

[0015] [Figure 1]It is a block diagram showing a configuration example of a gas turbine power generation plant according to an embodiment of the present disclosure. [Figure 2] It is a schematic diagram of a pilot nozzle and a main nozzle according to an embodiment of the present disclosure. [Figure 3] It is a diagram showing an example of data stored in a storage unit according to an embodiment of the present disclosure. [Figure 4] It is a flowchart (Part 1) showing an operation example of a determination unit according to an embodiment of the present disclosure. [Figure 5] It is a flowchart (Part 2) showing an operation example of a determination unit according to an embodiment of the present disclosure. [Figure 6] It is a schematic block diagram showing the configuration of a computer according to at least one embodiment.

Mode for Carrying Out the Invention

[0016] Hereinafter, a control device for a gas turbine, a control method for a gas turbine, and a program according to an embodiment of the present disclosure will be described with reference to each figure. In each figure, the same or corresponding configurations are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

[0017] (Configuration Example of Gas Turbine Power Generation Plant) FIG. 1 is a block diagram showing a configuration example of a gas turbine power generation plant 1 according to an embodiment of the present disclosure. The gas turbine power generation plant 1 includes a control device 2, a fuel gas supply device 3, an electric power meter 4, a cooler 5, a temperature sensor 6, a temperature sensor 7, a gas turbine 10, and flow control valves 30, 31-PD, 31-PP, 31-M. In FIG. 1, the solid connection lines indicate the paths of pipes through which either fuel gas or sweep air flows, and the dotted connection lines indicate the paths of wirings through which electrical signals are transmitted and received.

[0018] The fuel gas supply device 3 stores fuel gas such as natural gas, for example, and supplies the fuel gas to the gas turbine 10 via the flow control valves 31-PD, 31-PP, 31-M.

[0019] The flow control valve 31-PD is connected at one end to the fuel gas supply device 3 via a pipe, and at the other end to the fuel supply line 41-PD. The flow control valve 31-PP is connected at one end to the fuel gas supply device 3 via a pipe, and at the other end to the fuel supply line 41-PP. The flow control valve 31-M is connected at one end to the fuel gas supply device 3 via a pipe, and at the other end to the fuel supply line 41-M. The flow control valves 31-PD, 31-PP, and 31-M are electrically connected to the control device 2, and when receiving a valve opening command signal from the control device 2, they open and close the valve to the valve opening indicated by the received valve opening command signal to adjust the flow rate of the fuel gas.

[0020] The gas turbine 10 includes a compressor 11, a combustor 12, a turbine 13, a rotor 14, and a generator 15. The compressor 11 sucks in and compresses air from the outside as indicated by the dashed arrow due to the rotation of the rotor 14 that penetrates through the compressor 11 and the turbine 13, and the compressed air flows out to the combustor 12.

[0021] The IGV (Inlet Guide Vane) 16 is installed inside the compressor 11 near the air inlet of the compressor 11. The IGV 16 is electrically connected to the control device 2, and when receiving an IGV opening command signal from the control device 2, it opens and closes the guide vanes to the IGV opening indicated by the received IGV opening command signal to adjust the amount of air sucked in by the compressor 11.

[0022] The combustor 12 includes a combustor chamber 17 into which the air flowing out from the compressor 11 flows, and a combustor inner cylinder 18 into which the air flowing out from the combustor chamber 17 flows. The air flowing into the combustor inner cylinder 18 flows from the upper side of the combustor inner cylinder 18 to which the fuel supply lines 41-PD, 41-PP, and 41-M are connected toward the lower side of the combustor inner cylinder 18 provided with an opening through which the combustion gas flows out toward the turbine 13, as indicated by the dashed arrow.

[0023] As shown in Figure 2, the combustor inner cylinder 18 is equipped with a pilot nozzle 50 and a main nozzle 60 inside. In Figure 2, the direction of the arrow indicated by the symbol AF is the direction of airflow inside the combustor inner cylinder 18 (hereinafter referred to as the airflow direction AF). The pilot nozzle 50 and the main nozzle 60 have a longitudinal shape, and Figure 2 is a schematic diagram showing the cross-sections of the pilot nozzle 50 and the main nozzle 60 when they are cut by a plane parallel to the longitudinal direction and containing their respective central axes. The pilot nozzle 50 and the main nozzle 60 are positioned so that their longitudinal direction, i.e., the direction of their central axes, is aligned with the airflow direction AF in the combustor inner cylinder 18.

[0024] The pilot nozzle 50 is connected to fuel supply lines 41-PD and 41-PP. The main nozzle 60 is connected to fuel supply line 41-M. Inside the pilot nozzle 50, there are two pipes connected to fuel supply lines 41-PD and 41-PP, respectively. These pipes and the fuel supply lines 41-PD and 41-PP connected to them are physically separate entities. However, for the sake of explanation, the pipe inside the pilot nozzle 50 connected to fuel supply line 41-PD will be described as being included in fuel supply line 41-PD, and the pipe inside the pilot nozzle 50 connected to fuel supply line 41-PP will be described as being included in fuel supply line 41-PP. Similarly to the pilot nozzle 50, the pipe inside the main nozzle 60 will be described as being included in fuel supply line 41-M connected to the main nozzle 60.

[0025] The pilot nozzle 50 has diffusion injection holes 51-1 and 51-2 for injecting fuel gas when the fuel gas is diffusely combusted, and premixing injection holes 52-1 and 52-2 for injecting fuel gas when the fuel gas is premixed and combusted.

[0026] Fuel supply passage 41-PD leads to injection holes 51-1 and 51-2, and fuel supply passage 41-PP leads to injection holes 52-1 and 52-2. Note that Figure 2 is a schematic diagram, and in reality, there are not only two injection holes for diffusion, 51-1 and 51-2, but multiple injection holes. Similarly, there are not only two injection holes for premixing, 52-1 and 52-2, but multiple injection holes. However, here we will explain assuming that there are at least two injection holes 51-1 and 51-2 for diffusion, and at least two injection holes 52-1 and 52-2 for premixing.

[0027] In the pilot nozzle 50, the injection of fuel gas from the diffusion injection holes 51-1 and 51-2 will be hereinafter referred to as "diffusion injection," and the injection of fuel gas from the premixing injection holes 52-1 and 52-2 will be hereinafter referred to as "premixing injection."

[0028] The main nozzle 60 has injection holes 61-1 and 61-2. The fuel supply passage 41-M leads to injection holes 61-1 and 61-2. Note that Figure 2 is a schematic diagram, and in reality, there are not just two injection holes, 61-1 and 61-2, but multiple injection holes. However, here we will explain assuming that there are at least two injection holes, 61-1 and 61-2.

[0029] In Figure 2, one main nozzle 60 is shown to illustrate an example of the positional relationship between the pilot nozzle 50 and the main nozzle 60. However, generally, multiple main nozzles 60 are arranged around the pilot nozzle 50 in the combustor inner cylinder 18, with their respective longitudinal directions aligned with the airflow direction AF. Each of the multiple main nozzles 60 is positioned such that, for example, the curved surface containing its central axis forms a cylinder, and the central axis of the formed cylinder coincides with the central axis of the pilot nozzle 50. In this case, each of the multiple main nozzles 60 is positioned such that the positions of their respective injection holes 61-1, 61-2 are all located upstream in the airflow direction AF from the positions of the diffusion injection holes 51-1, 51-2 of the pilot nozzle 50.

[0030] When the combustor inner cylinder 18 is equipped with multiple main nozzles 60, the multiple main nozzles 60 are divided into, for example, multiple groups, and the number of flow control valves 31-M and fuel supply passages 41-M corresponds to the number of groups. The fuel supply passage 41-M assigned to one group branches out and connects to each of the multiple main nozzles 60 included in that group, supplying fuel gas with a flow rate adjusted for each group.

[0031] When diffusion combustion is performed in the combustor inner cylinder 18, fuel gas is supplied from fuel supply passages 41-PD and 41-M. In this case, diffusion injection is performed by the pilot nozzle 50 into the air flowing inside the combustor inner cylinder 18, and the diffusely injected fuel gas burns. Furthermore, when fuel gas is injected from the injection holes 61-1 and 61-2 of the main nozzle 60 into the air flowing inside the combustor inner cylinder 18, the injected fuel gas burns using the flame obtained from the combustion of the diffusely injected fuel gas as a pilot ignition.

[0032] When premixed combustion is performed in the combustor cylinder 18, fuel gas is supplied from fuel supply passages 41-PP and 41-M. In this case, premixed fuel gas is injected into the air flowing inside the combustor cylinder 18 by the pilot nozzle 50, and the premixed fuel gas burns. Furthermore, when fuel gas is injected into the air flowing inside the combustor cylinder 18 from the injection holes 61-1 and 61-2 of the main nozzle 60, the injected fuel gas burns using the flame obtained from the combustion of the premixed fuel gas as a pilot ignition.

[0033] As shown in Figure 1, the combustion gas generated in the combustor cylinder 18 by the combustion of fuel gas flows out through an opening provided at the bottom of the combustor cylinder 18, as indicated by the dashed arrow. This flowing combustion gas enters the turbine 13, causing the rotor 14 to rotate, and the rotation of the rotor 14 generates electricity in the generator 15. The power meter 4 measures the amount of electricity generated by the generator 15 at regular intervals, for example, and transmits the measured amount of electricity to the control device 2.

[0034] In the combustor cylinder 18, when the same calorific value of fuel gas is burned by premixed combustion and diffusion combustion, premixed combustion results in lower NOx emissions. However, premixed combustion cannot maintain a flame unless the combustion temperature exceeds a certain level. Therefore, for example, when starting operation of the gas turbine 10, it starts with diffusion combustion, which can maintain a flame even at low combustion temperatures, and when the combustion temperature rises to a level where it can switch to premixed combustion, the switch from diffusion combustion to premixed combustion occurs.

[0035] In the gas turbine 10, an increase in combustion temperature means an increase in the load on the gas turbine 10. Here, the load on the gas turbine 10 is a value derived from the output of the gas turbine 10, that is, the amount of electricity generated by the generator 15, and is expressed here as a percentage of the rated output of the gas turbine 10. In other words, when the rated output is obtained, the load on the gas turbine 10 is "100%".

[0036] The lowest combustion temperature at which a flame can be maintained in premixed combustion is the lowest combustion temperature at which premixed combustion and diffusion combustion can be switched to each other. The load on the gas turbine 10 corresponding to this lowest combustion temperature will be referred to below as the "switching load".

[0037] As described above, when switching from diffusion combustion to premixed combustion, the load on the gas turbine 10 during premixed combustion is greater than or equal to the load at the time of switching, while the load on the gas turbine 10 during diffusion combustion is less than or equal to the load at the time of switching. Therefore, in the following, operation of the gas turbine 10 during premixed combustion will be referred to as "high-load operation," and operation of the gas turbine 10 during diffusion combustion will be referred to as "low-load operation."

[0038] In order to supply the amount of electricity required by the power transmission system, the gas turbine 10 must be operated under high load. Furthermore, when the gas turbine 10 is operated continuously, exhaust gas regulations and other requirements must be met. To achieve NOx emissions that meet these exhaust gas regulations, the gas turbine 10 must be operated under high load conditions, with a load exceeding a predetermined load.

[0039] In other words, in order to supply the amount of electricity required by the power transmission system while meeting requirements such as exhaust gas regulations, the gas turbine 10 must be operated in a premixed combustion state, and the range of loads that can be allowed during operation must be set from below the "100%" load, which is the load when rated output is obtained, to above a predetermined load. This load range is the range of loads that can be allowed when operating the gas turbine 10, and is hereinafter referred to as the "operational allowable load range". Here, the predetermined load is, for example, a load of about "50%". If the load on the gas turbine 10 falls outside the operational allowable load range, it will become impossible to comply with exhaust gas regulations, etc., and the gas turbine 10 must be stopped.

[0040] As shown in Figure 2, the positions of the premixing injection holes 52-1 and 52-2 of the pilot nozzle 50, and the positions of the injection holes 61-1 and 61-2 of the main nozzle are located upstream in the airflow direction AF compared to the positions of the diffusion injection holes 51-1 and 51-2 of the pilot nozzle 50. In other words, among all the injection holes 51-1, 51-2, 52-1, 52-2, 61-1, and 61-2 of the pilot nozzle 50 and the main nozzle 60 provided in the combustor inner cylinder 18, the positions of the diffusion injection holes 51-1 and 51-2 of the pilot nozzle 50 are located furthest downstream in the airflow direction AF. Therefore, the diffusion injection holes 51-1 and 51-2 are closest to the high-temperature combustion gas. When premixing injection is performed in the pilot nozzle 50, fuel gas is not injected from the diffusion injection holes 51-1 and 51-2. Therefore, there is a risk that high-temperature combustion gases may flow back through the diffusion injection holes 51-1 and 51-2, potentially burning out the pilot nozzle 50.

[0041] To prevent burnout of the pilot nozzle 50, a flow control valve 30, a sweep air supply passage 40, and a cooler 5 are provided. The flow control valve 30 is connected to the sweep air supply passage 40 at one end and to the fuel supply passage 41-PD at the other end. The flow control valve 30 is electrically connected to the control device 2, and when it receives a valve opening command signal from the control device 2, it opens and closes the valve to the valve opening indicated by the received valve opening command signal to adjust the flow rate of sweep air. The sweep air supply passage 40 is connected to the combustor chamber 17, and extracts air from the combustor chamber 17, guiding the extracted air as sweep air towards the flow control valve 30. The cooler 5 is, for example, an air-cooled or water-cooled cooling means attached to the outer surface of the sweep air supply passage 40. The cooler 5 cools the temperature of the sweep air flowing through the sweep air supply passage 40 after it has passed the location where the cooler 5 is installed, to a temperature that ensures the fuel gas will not self-ignite.

[0042] When the flow control valve 30 is opened while the flow control valve 31-PD is closed, swept air flows into the fuel supply passage 41-PD, and swept air flows out from the diffusion injection holes 51-1 and 51-2 of the pilot nozzle 50. This prevents high-temperature combustion gas from flowing back into the diffusion injection holes 51-1 and 51-2 when the pilot nozzle 50 is performing premixed injection, thereby preventing burnout of the pilot nozzle 50.

[0043] When the pilot nozzle 50 switches from diffusion injection to premixed injection, the fuel gas remaining in the fuel supply passage 41-PD comes into contact with the sweep air supplied to the fuel supply passage 41-PD. Conversely, when the pilot nozzle 50 switches from premixed injection to diffusion injection, the sweep air remaining in the fuel supply passage 41-PD comes into contact with the fuel gas supplied to the fuel supply passage 41-PD. Even if these contacts occur, if the cooler 5 is operating normally, the sweep air is cooled by the cooler 5, so the fuel gas will not self-ignite.

[0044] The temperature sensor 6 measures the temperature of the swept air flowing between the flow control valve 30 and the cooler 5 in the swept air supply passage 40, i.e., the swept air after cooling, at regular intervals, and transmits the measured temperature of the swept air to the control device 2. The temperature sensor 7 is located outside the gas turbine 10, for example, near the intake of the air compressor 11, and measures the ambient temperature at its location at regular intervals, and transmits the measured ambient temperature to the control device 2.

[0045] The control device 2 can be configured using, for example, a computer such as a server, personal computer, or microcomputer, and peripheral devices for that computer. Its functional configuration, which consists of a combination of hardware such as the computer and software such as programs executed by the computer, includes a storage unit 20, a temperature acquisition unit 21, a determination unit 22, a fuel supply control unit 23, and an IGV control unit 24, as shown in Figure 1.

[0046] As shown in Figure 3, the memory unit 20 stores three predetermined temperature values: the self-ignition prevention temperature, the temperature for determining whether operation can be maintained, and the temperature for determining whether injection switching can be switched, as well as two predetermined load values: the load corresponding to the first load reduction command signal and the load corresponding to the second load reduction command signal.

[0047] The autoignition prevention temperature, the temperature for determining whether operation can be maintained, and the temperature for determining whether injection switching can be switched are predetermined, for example, as follows: The autoignition temperature of the fuel gas is known. For example, a temperature lower than this known autoignition temperature of the fuel gas is predetermined as the autoignition prevention temperature of the fuel gas, which makes the possibility of the fuel gas autoigniting extremely low, while not excessively lowering the combustion temperature. For example, if the fuel gas is natural gas, a temperature of "420°C" is predetermined as the autoignition prevention temperature.

[0048] The injection switching feasibility determination temperature is the maximum permissible sweep air temperature at the moment when the sweep air and fuel gas actually come into contact, such as when switching from diffusion injection to premixed injection and from premixed injection to diffusion injection. This temperature is set with even greater emphasis on safety than the autoignition prevention temperature. For example, if the autoignition prevention temperature is "420°C", the injection switching feasibility determination temperature is set at a temperature below the autoignition prevention temperature, such as "410°C".

[0049] The operating feasibility determination temperature is a temperature arbitrarily set within a range from below the self-ignition prevention temperature to above the injection switching feasibility determination temperature. In other words, the relationship is "self-ignition prevention temperature > operating feasibility determination temperature > injection switching feasibility determination temperature". For example, the average value of the self-ignition prevention temperature and the injection switching feasibility determination temperature is predetermined as the operating feasibility determination temperature. For example, if the self-ignition prevention temperature is "420°C" and the injection switching feasibility determination temperature is "410°C", the operating feasibility determination temperature will be "415°C".

[0050] The load corresponding to the first load reduction command signal is the target load when the fuel supply control unit 23 reduces the load of the gas turbine 10 upon receiving the first load reduction command signal. Here, as an example, the lower limit load of the allowable operating load range of the gas turbine 10 described above is predetermined as the load corresponding to the first load reduction command signal. The load corresponding to the second load reduction command signal is the target load when the fuel supply control unit 23 reduces the load of the gas turbine 10 upon receiving the second load reduction command signal. Here, as an example, the switching load of the gas turbine 10 described above is predetermined as the load corresponding to the second load reduction command signal.

[0051] As mentioned above, the load during switching is the load when switching between high-load operation and low-load operation. The permissible operational load range is the load range in which high-load operation is performed, and is the range from loads below "100%" to loads above a specified load. Therefore, the lower limit load of the permissible operational load range is the specified load. The specified load, which is the lowest load at which exhaust gas regulations can be complied with, is the load at which the flame can be maintained in a stable state during premixed combustion. In contrast, the load during switching is the lowest load at which the flame can be maintained during premixed combustion, and if the specified load is around "50%" as mentioned above, the load during switching will be around "30%". Therefore, generally, the relationship is "lower limit load of the permissible operational load range = specified load > load during switching".

[0052] The temperature acquisition unit 21 receives and acquires the temperature of the swept air measured and transmitted by the temperature sensor 6. The determination unit 22 compares the temperature of the swept air acquired by the temperature acquisition unit 21 with the self-ignition prevention temperature, the operating maintenance feasibility determination temperature, and the injection switching feasibility determination temperature stored in the memory unit 20, and outputs a command signal to the fuel supply control unit 23 according to the result of the comparison.

[0053] The fuel supply control unit 23 performs various controls related to the supply of fuel gas by transmitting various command signals and valve opening command signals indicating the valve opening degree corresponding to the load of the gas turbine 10, which are determined by the amount of power generated received from the power meter 4, to the flow control valves 30, 31-PD, 31-PP, and 31-M. These various controls include controlling the switching from diffusion injection to premixed injection and the switching from premixed injection to diffusion injection at the pilot nozzle 50.

[0054] The IGV control unit 24 determines the IGV opening degree according to the amount of power generated received from the power meter 4 and the ambient temperature received from the temperature sensor 7, and sends an IGV opening degree command signal indicating the determined IGV opening degree to the IGV 16 to adjust the opening degree of the IGV 16.

[0055] (Processing by the control device) The processing by the control device 2 will be explained with reference to Figures 4 and 5. Figures 4 and 5 are flowcharts showing examples of the operation of the determination unit 22 of the control device 2. The marks with "A" inside a circle and the marks with "B" inside a circle shown in Figures 4 and 5 indicate connection points where processing continues. The mark with "A" inside a circle means that after the processing in S9 in Figure 4, the processing in S10 in Figure 5 is performed. The mark with "B" inside a circle means that if the determination in the determination process in S12 in Figure 5 is "No", then the processing in S4 in Figure 4 is performed.

[0056] The processes shown in Figures 4 and 5 are performed when the gas turbine 10 is operating in a state where it is supplying the amount of electricity required by the power transmission system while also meeting requirements such as exhaust gas regulations. In other words, the processes are performed when premixed combustion is taking place in the combustor 12 of the gas turbine 10, and the load on the gas turbine 10 is within the operationally permissible load range.

[0057] Processing by the IGV control unit 24 is performed in parallel with the processing shown in Figures 4 and 5. The IGV control unit 24 has a function stored in its internal memory that determines the IGV opening degree from the load of the gas turbine 10 and the ambient temperature. The power meter 4 measures the amount of power generated by the generator 15 at regular intervals, and transmits the measured amount of power to the fuel supply control unit 23 and the IGV control unit 24 each time it measures. The temperature sensor 7 measures the ambient temperature at regular intervals, and transmits the measured ambient temperature to the IGV control unit 24 each time it measures.

[0058] Each time the IGV control unit 24 receives a power generation amount from the power meter 4, it calculates the load of the gas turbine 10 from the received power generation amount. Each time the load of the gas turbine 10 is calculated, the IGV control unit 24 calculates the IGV opening by substituting the ambient temperature immediately before the load calculation and the calculated load of the gas turbine 10 into a function stored in the internal memory area. Here, the ambient temperature immediately before the load calculation may be the ambient temperature received from the temperature sensor 7 immediately before the load calculation, or the ambient temperature received from the temperature sensor 7 immediately after the load calculation, or the ambient temperature with the smaller time difference between the time the load was calculated and the time it was received. The IGV control unit 24 transmits an IGV opening command signal indicating the calculated IGV opening to the IGV 16 to adjust the opening of the IGV 16.

[0059] For example, the fuel supply control unit 23 performs diffusion combustion in the combustor 12, then switches from diffusion combustion to premixed combustion, and then increases the load on the gas turbine 10. After maintaining the load on the gas turbine 10 at a load above the lower limit of the operational allowable load range for a predetermined first load maintenance time, the fuel supply control unit 23 outputs a processing start command signal to the determination unit 22. The first predetermined load maintenance time is predetermined considering the time it takes for the temperature of the sweep air to become approximately constant after the load on the gas turbine 10 has been maintained at a constant value. When the determination unit 22 receives the processing start command signal from the fuel supply control unit 23, it starts the processing shown in Figures 4 and 5.

[0060] The temperature sensor 6 measures the temperature of the swept air at regular intervals and transmits the measured temperature of the swept air to the temperature acquisition unit 21 each time it measures. The temperature acquisition unit 21 outputs the received temperature of the swept air to the determination unit 22 each time it receives the temperature of the swept air transmitted by the temperature sensor 6. The determination unit 22 waits for the temperature acquisition unit 21 to output the temperature of the swept air, and when the temperature acquisition unit 21 outputs the temperature of the swept air, it takes in the outputted temperature of the swept air (S1).

[0061] Furthermore, the determination unit 22 acquires the temperature of the swept air in the following manner to prevent multiple processes from S2 onward from being performed in parallel. When the determination unit 22 acquires one swept air temperature, if the temperature acquisition unit 21 outputs another swept air temperature before the determination unit 22 enters a state where it is waiting for the temperature acquisition unit 21 to output another swept air temperature, the determination unit 22 discards that other swept air temperature without acquiring it.

[0062] When the determination unit 22 receives the temperature of the swept air output by the temperature acquisition unit 21, it determines whether the temperature of the swept air exceeds the injection switching feasibility determination temperature stored in the storage unit 20 (S2). If the determination unit 22 determines that the temperature of the swept air exceeds the injection switching feasibility determination temperature (S2, Yes), it performs an alarm notification process (S3). Here, the alarm notification process by the determination unit 22 is, for example, to cause the output device connected to the control device 2 to display an indication that the temperature of the swept air exceeds the injection switching feasibility determination temperature, or to cause the notification device connected to the control device 2 to emit an alarm sound.

[0063] In the process of S2, if the determination unit 22 determines that the temperature of the swept air does not exceed the injection switching feasibility determination temperature (S2, No), it determines whether or not an alarm has been sounded (S4). If the determination unit 22 determines that no alarm has been sounded (S4, No), it performs the process of S1 again. On the other hand, if the determination unit 22 determines that an alarm has been sounded (S4, Yes), it performs the process of stopping the alarm sounding (S5), and then performs the process of S1 again.

[0064] After performing the process in S3, the determination unit 22 determines whether the temperature of the swept air exceeds the autoignition prevention temperature stored in the memory unit 20 (S6). If the determination unit 22 determines that the temperature of the swept air exceeds the autoignition prevention temperature (S6, Yes), it outputs a trip command signal to the fuel supply control unit 23 (S7) and terminates the process.

[0065] When the fuel supply control unit 23 receives a trip command signal from the determination unit 22, it transmits a valve opening command signal indicating a fully closed valve opening to the flow control valves 31-PD, 31-PP, and 31-M. Each of the flow control valves 31-PD, 31-PP, and 31-M receives the valve opening command signal and closes its valve to a fully closed state according to the fully closed valve opening indicated by the received valve opening command signal. As a result, fuel gas is no longer supplied to the combustor 12, and the gas turbine 10 stops operating.

[0066] In the process of S6, if the determination unit 22 determines that the temperature of the swept air does not exceed the self-ignition prevention temperature (S6, No), it determines whether the temperature of the swept air exceeds the operating feasibility determination temperature stored in the memory unit 20 (S8). If the determination unit 22 determines that the temperature of the swept air does not exceed the operating feasibility determination temperature (S8, No), it performs the process of S1 again. On the other hand, if the determination unit 22 determines that the temperature of the swept air exceeds the operating feasibility determination temperature (S8, Yes), it outputs a first load reduction command signal to the fuel supply control unit 23 (S9). In other words, in the determination process of S8, the determination unit 22 determines, based on the temperature of the swept air and the operating feasibility determination temperature, whether to maintain the operation of the gas turbine 10 at the load at the time of the determination process, or in other words, whether to maintain the operation of the gas turbine 10 without reducing the load on the gas turbine 10. In the determination process in S8, if the determination unit 22 determines "No," it means that it has determined that the operation of the gas turbine 10 can be maintained with the load at which the determination process is performed, that is, that the operation of the gas turbine 10 can be maintained without reducing the load. Conversely, if the determination unit 22 determines "Yes," it means that it has determined that the operation of the gas turbine 10 cannot be maintained with the load at which the determination process is performed, that is, that the operation of the gas turbine 10 cannot be maintained without reducing the load. Therefore, in the determination process in S8, if the determination unit 22 determines "Yes," the first load reduction command signal is output to the fuel supply control unit 23 in the process of S9. This attempts to reduce the load on the gas turbine 10 and to see if the temperature of the sweep air can be lowered while maintaining the operation of the gas turbine 10 with the reduced load.

[0067] When the fuel supply control unit 23 receives a first load reduction command signal from the determination unit 22, the combustor 12 is in a state of premixed combustion. That is, the flow control valve 31-PD is in a fully closed state, and the flow control valves 31-PP and 31-M are open to an extent corresponding to the load of the gas turbine 10. The flow control valve 30 is open, and sweep air flowing out from the combustor casing 17 is flowing out from the diffusion injection holes 51-1 and 51-2 of the pilot nozzle 50 via the sweep air supply passage 40, the flow control valve 30, and the fuel supply passage 41-PD.

[0068] When the fuel supply control unit 23 receives a first load reduction command signal from the determination unit 22, it sets the load corresponding to the first load reduction command signal stored in the memory unit 20, i.e., the lower limit load of the operationally permissible load range, as the first target load. The fuel supply control unit 23 performs a process to reduce the load of the gas turbine 10 to the first target load. The fuel supply control unit 23 receives the amount of power generated from the power meter 4 and calculates the load of the gas turbine 10 from the received amount of power generated. The fuel supply control unit 23 calculates the valve opening of each of the flow control valves 31-PP and 31-M so that the calculated load approaches the first target load. The fuel supply control unit 23 transmits each of the valve opening command signals indicating the calculated valve opening to the respective flow control valves 31-PP and 31-M. Each of the flow control valves 31-PP and 31-M receives the valve opening command signal and adjusts its opening to match the valve opening indicated by the received valve opening command signal.

[0069] The fuel supply control unit 23 adjusts the opening of the flow control valves 31-PP and 31-M in the procedure described above each time it receives power generation data from the power meter 4, until the load of the gas turbine 10, calculated from the power generation data received sequentially from the power meter 4, reaches the first target load. When the load of the gas turbine 10 drops to the first target load and the load of the gas turbine 10 is maintained at the first target load for a predetermined second load maintenance time, the fuel supply control unit 23 outputs a first load drop completion notification signal to the determination unit 22. The second predetermined load maintenance time is predetermined considering the time it takes for the temperature of the sweep air to become approximately constant after the load of the gas turbine 10 has been maintained at the first target load.

[0070] The processing by the IGV control unit 24 described above is performed in parallel until the fuel supply control unit 23 reduces the load on the gas turbine 10 to the first target load. The function pre-stored in the internal memory area of ​​the IGV control unit 24, with some exceptions, is, in principle, a function that exhibits the characteristic that the opening degree of the IGV 16 decreases as the load on the gas turbine 10 decreases. Therefore, as the load on the gas turbine 10 decreases and the opening degree of the IGV 16 decreases, the amount of air drawn in by the air compressor 11 decreases. As the amount of air drawn in by the air compressor 11 decreases, the temperature of the air flowing into the combustor casing 17 decreases, and thus the temperature of the sweep air also decreases.

[0071] Moving on to Figure 5, after processing in S9, the determination unit 22 waits for the fuel supply control unit 23 to output a first load reduction completion notification signal (S10). When the determination unit 22 receives the first load reduction completion notification signal output by the fuel supply control unit 23, it waits for the temperature acquisition unit 21 to output the sweep air temperature, similar to the process in S1. When the temperature acquisition unit 21 outputs the sweep air temperature, the determination unit 22 receives the outputted sweep air temperature (S11).

[0072] When the determination unit 22 receives the temperature of the swept air output by the temperature acquisition unit 21, it determines whether the temperature of the swept air exceeds the injection switching feasibility determination temperature stored in the storage unit 20 (S12). If the determination unit 22 determines that the temperature of the swept air does not exceed the injection switching feasibility determination temperature (S12, No), it performs the process of S4. On the other hand, if the determination unit 22 determines that the temperature of the swept air exceeds the injection switching feasibility determination temperature (S12, Yes), it outputs a second load reduction command signal to the fuel supply control unit 23 (S13). In other words, in the determination process of S12, the determination unit 22 determines, based on the temperature of the swept air and the injection switching feasibility determination temperature, whether to maintain the operation of the gas turbine 10 at the load during the determination process, or in other words, whether to maintain the operation of the gas turbine 10 without reducing the load on the gas turbine 10. In the determination process of S12, if the determination unit 22 determines "No," it means that it has determined that the operation of the gas turbine 10 can be maintained with the load at which the determination process is performed, that is, that the operation of the gas turbine 10 can be maintained without reducing the load. On the other hand, if the determination unit 22 determines "Yes," it means that it has determined that the operation of the gas turbine 10 cannot be maintained with the load at which the determination process is performed, that is, that the operation of the gas turbine 10 cannot be maintained without reducing the load. Therefore, in the determination process of S12, if the determination unit 22 determines "Yes," the process of S13 outputs a second load reduction command signal to the fuel supply control unit 23. This attempts to reduce the load on the gas turbine 10 and to see if the temperature of the sweep air can be lowered while maintaining the operation of the gas turbine 10 with the reduced load.

[0073] When the fuel supply control unit 23 receives a second load reduction command signal from the determination unit 22, it sets the load corresponding to the second load reduction command signal stored in the memory unit 20, i.e., the switching load, as the second target load. When the fuel supply control unit 23 receives a second load reduction command signal from the determination unit 22, the state of the combustor 12 is in a state of premixed combustion, similar to when it receives a first load reduction command signal from the determination unit 22. Therefore, the fuel supply control unit 23 performs the same processing as when it receives a first load reduction command signal from the determination unit 22, but with the first target load replaced by the second target load. When the load of the gas turbine 10 has decreased to the second target load and the load of the gas turbine 10 is maintained at the second target load for a predetermined third load maintenance time, the fuel supply control unit 23 outputs a second load reduction completion notification signal to the determination unit 22. The third predetermined load maintenance time is determined in advance, taking into account the time it takes for the temperature of the sweep air to become nearly constant after the load of the gas turbine 10 has been maintained at the second target load.

[0074] While the fuel supply control unit 23 reduces the load on the gas turbine 10 to the second target load, the processing by the IGV control unit 24 described above is performed in parallel. As a result of this processing, if the opening of the IGV 16 decreases, the temperature of the sweep air decreases.

[0075] After processing in S13, the determination unit 22 waits for the fuel supply control unit 23 to output a second load reduction completion notification signal (S14). When the determination unit 22 receives the second load reduction completion notification signal output by the fuel supply control unit 23, it waits for the temperature acquisition unit 21 to output the sweep air temperature, similar to the processing in S1. When the temperature acquisition unit 21 outputs the sweep air temperature, the determination unit 22 receives the outputted sweep air temperature (S15).

[0076] When the determination unit 22 receives the temperature of the swept air output by the temperature acquisition unit 21, it determines whether the temperature of the received swept air exceeds the injection switching feasibility determination temperature (S16). If the determination unit 22 determines that the temperature of the swept air exceeds the injection switching feasibility determination temperature (S16, Yes), it outputs a trip command signal to the fuel supply control unit 23 (S17) and terminates the process.

[0077] When the fuel supply control unit 23 receives a trip command signal from the determination unit 22, it performs the same processing as when it receives a trip command signal output by the determination unit 22 in the processing of S7 described above, and stops the operation of the gas turbine 10.

[0078] In the process of S16, if the determination unit 22 determines that the temperature of the swept air does not exceed the injection switching feasibility determination temperature (S16, No), it outputs an injection switching operation stop command signal to the fuel supply control unit 23 (S18) and terminates the process.

[0079] In other words, in the determination process of S16, the determination unit 22 determines, from a temperature perspective, whether or not it is possible to switch from premixed combustion to diffusion combustion, based on the temperature of the sweep air and the injection switching feasibility determination temperature, when the operation of the gas turbine 10 is maintained at a load during the determination process, in other words, a switching load that allows switching from premixed combustion to diffusion combustion. In the determination process of S16, if the determination unit 22 determines "Yes", it means that the temperature of the sweep air is above the injection switching feasibility determination temperature, and therefore it is determined that it is not possible to switch from premixed combustion to diffusion combustion. Since switching is not possible, the determination unit 22 outputs a trip command signal to the fuel supply control unit 23 to stop the operation of the gas turbine 10. On the other hand, if the determination unit 22 determines "No", it means that the temperature of the sweep air is not above the injection switching feasibility determination temperature, and therefore it is determined that it is possible to switch from premixed combustion to diffusion combustion. In this case, the determination unit 22 outputs an injection switching operation stop command signal to the fuel supply control unit 23 during processing S18. Therefore, when the fuel supply control unit 23 receives the injection switching operation stop command signal from the determination unit 22, the combustor 12 is in a state of premixed combustion, the load on the gas turbine 10 is at a switching load that allows switching from premixed combustion to diffusion combustion, and the temperature of the sweep air is at a temperature that allows switching from premixed combustion to diffusion combustion.

[0080] When the fuel supply control unit 23 receives a command signal from the determination unit 22 to stop injection switching operation, it performs the following processing to switch from premixed combustion to diffusion combustion. The fuel supply control unit 23 transmits a valve opening command signal indicating a fully closed valve opening to the flow control valves 30, 31-PP. The load of the gas turbine 10 is calculated to determine the valve opening of the flow control valves 31-PD, 31-M which will be the load at the time of switching, and each valve opening command signal indicating the calculated valve opening is transmitted to the respective flow control valves 31-PD, 31-M. Each of the flow control valves 30, 31-PD, 31-PP, and 31-M receives the valve opening command signal and opens and closes the valve according to the valve opening indicated by the received valve opening command signal. As a result, flow control valves 30 and 31-PP are fully closed, flow control valves 31-PD and 31-M are opened to the point where the load on the gas turbine 10 is set to the switching load, diffusion injection occurs in the pilot nozzle 50, and diffusion combustion occurs in the combustor 12.

[0081] Once the switch from premixed combustion to diffusion combustion is complete, the fuel supply control unit 23 performs a process to reduce the load on the gas turbine 10 to "0%". The fuel supply control unit 23 receives the amount of power generated from the power meter 4 and calculates the load on the gas turbine 10 from the received amount of power generated. The fuel supply control unit 23 calculates the valve opening of each of the flow control valves 31-PD and 31-M so that the calculated load approaches "0%". The fuel supply control unit 23 transmits each of the valve opening command signals indicating the calculated valve opening to the respective flow control valves 31-PD and 31-M. Each of the flow control valves 31-PD and 31-M receives the valve opening command signal and adjusts its opening to match the valve opening indicated by the received valve opening command signal.

[0082] The fuel supply control unit 23 adjusts the opening of the flow control valves 31-PD and 31-M in the above-described procedure each time it receives power generation data from the power meter 4, until the load on the gas turbine 10, calculated from the power generation data received sequentially from the power meter 4, becomes "0%". As a result, the load on the gas turbine 10 gradually decreases, and eventually the flow control valves 31-PD and 31-M are fully closed, so that fuel gas is no longer supplied to the combustor 12, the gas turbine 10 stops operating, and the load on the gas turbine 10 becomes "0%".

[0083] (An example of how the embodiment works) For example, suppose that while the gas turbine 10 is operating to supply the amount of electricity required by the power transmission system while also meeting requirements such as exhaust gas regulations, a malfunction occurs in the cooler 5, making it impossible to cool the sweep air. In this case, the temperature of the sweep air gradually rises. When the temperature of the sweep air exceeds the injection switching feasibility determination temperature, the determination unit 22 makes a "Yes" determination in the determination process S2 in Figure 4, and then performs an alarm notification process in the process S3.

[0084] If the malfunction of the cooler 5 is not resolved by the operator of the gas turbine power plant 1 after receiving an alarm notification, maintaining the operation of the gas turbine 10 at the current load may cause the temperature of the sweep air to continue to rise. Therefore, the determination unit 22 determines that if the temperature of the sweep air exceeds the operating feasibility determination temperature, even though it does not exceed the self-ignition prevention temperature, it will not maintain the operation of the gas turbine 10. In other words, the determination unit 22 makes a "Yes" determination in the determination process of S8 in Figure 4, and in the process of S9, outputs a first load reduction command signal to the fuel supply control unit 23, reducing the load of the gas turbine 10 to the lower limit load of the operating allowable load range. However, until the temperature of the sweep air exceeds the injection switching feasibility determination temperature and reaches the operating feasibility determination temperature, the determination unit 22 makes a "No" determination in the determination process of S8 and maintains the operation of the gas turbine 10 at the current load.

[0085] As the load decreases to the lower limit of the operationally permissible load range, the opening of the IGV16 decreases, causing the temperature of the sweep air to drop. If the temperature of the sweep air drops to a temperature below the injection switching feasibility determination temperature, the determination unit 22 determines to maintain the operation of the gas turbine 10. In other words, the determination unit 22 determines "No" in the determination process of S12 in Figure 5, determines "Yes" in the determination process of S4, and in the process of S5 stops the alarm notification, continuing the operation of the gas turbine 10 at the lower limit of the operationally permissible load range.

[0086] If the determination unit 22 determines "No" in the determination process of S12, the temperature of the sweep air is below the injection switching feasibility determination temperature, and the load on the gas turbine 10 is maintained at the lower limit of the allowable load range. Therefore, the gas turbine 10 is in a state where it can continue to operate in a way that meets the requirements of exhaust gas regulations, etc. Furthermore, the gas turbine 10 is in a state where it can continue to operate in a way that supplies the minimum amount of electricity required by the power transmission system. Moreover, since the temperature of the sweep air is below the injection switching feasibility determination temperature, the operator can switch from premixed combustion to diffusion combustion at any time without causing the fuel gas to self-ignite.

[0087] In these conditions, the operator can continue operating the gas turbine 10 while taking time to address any problems with the cooler 5. After the problem with the cooler 5 is resolved, the load on the gas turbine 10 can be increased again to return the gas turbine 10 to operation that can produce its rated output.

[0088] If the malfunction of the cooler 5 cannot be resolved by the operator's efforts, the operator and the power transmission system can coordinate in advance, for example, the date and time to shut down the gas turbine 10, in order to minimize the impact on the power transmission system. Then, the load on the gas turbine 10 can be reduced to the switching load, switching from premixed combustion to diffusion combustion, and after the switch, the load on the gas turbine 10 can be gradually reduced to shut down the gas turbine 10. For this reason, the determination unit 22 determines that the operation of the gas turbine 10 should be maintained if the temperature of the sweep air has dropped to a temperature below the injection switching feasibility determination temperature due to the load reduction to the lower limit load of the allowable operating load range.

[0089] In contrast, if the temperature of the sweep air does not drop to a temperature below the injection switching feasibility determination temperature, the operator will not be able to switch from premixed combustion to diffusion combustion and stop the gas turbine 10 at any time without causing the fuel gas to self-ignite. In this state, it is difficult to continue operating the gas turbine 10, so the determination unit 22 determines that it will not maintain the operation of the gas turbine 10. That is, the determination unit 22 makes a "Yes" determination in the determination process of S12 in Figure 5.

[0090] In this case, in order to avoid a large impact on the power transmission system, the determination unit 22 attempts to shut down the gas turbine 10 by performing the S13 process, i.e., outputting a second load reduction command signal to the fuel supply control unit 23. When the load of the gas turbine 10 is reduced to the switching load by the second load reduction command signal, the load of the gas turbine 10 falls outside the operational allowable load range, making it impossible to continue operating the gas turbine 10. However, if the opening of the IGV 16 is reduced by the load reduction to the switching load, the temperature of the sweep air can be lowered.

[0091] When the load is reduced during the switching process, if the temperature of the sweep air drops to a temperature below the injection switching feasibility determination temperature, it becomes possible to switch from premixed combustion to diffusion combustion. Therefore, the determination unit 22 determines that it is possible to switch from premixed combustion to diffusion combustion. In other words, the determination unit 22 determines "No" in the process of S16 in Figure 5, and outputs an injection switching stop command signal to the fuel supply control unit 23 in the process of S18. This allows the gas turbine 10 to be switched from premixed combustion to diffusion combustion without self-igniting the fuel gas, and after the switch, the load on the gas turbine 10 is gradually reduced, so that the gas turbine 10 is stopped in a way that does not have a large impact on the power transmission system.

[0092] In contrast, if the temperature of the sweep air does not drop below the injection switching feasibility determination temperature due to the load reduction on the load during switching, switching from premixed combustion to diffusion combustion may cause the fuel gas to self-ignite. Therefore, the determination unit 22 determines that it is not possible to switch from premixed combustion to diffusion combustion. That is, the determination unit 22 makes a "Yes" determination in the process of S16 in Figure 5, and as a final measure, outputs a trip command signal to the fuel supply control unit 23 in the process of S17.

[0093] (Effects of the embodiment) In the above embodiment, the load on the gas turbine 10 is reduced in two stages to attempt to lower the temperature of the sweep air, taking advantage of the correlation that reducing the load on the gas turbine 10 increases the likelihood of a decrease in the temperature of the sweep air. The first stage, a load reduction to the lower limit of the operational allowable load range, is a load reduction to attempt to continue operating the gas turbine 10. If, as a result of the first stage of load reduction, the temperature of the sweep air falls below the injection switching feasibility determination temperature, the operation of the gas turbine 10 is continued to improve the operating rate of the gas turbine 10. The second stage, a load reduction to the switching load, is a load reduction to attempt to stop the gas turbine 10 in order to minimize the impact on the power transmission system. If, as a result of the second stage of load reduction, the temperature of the sweep air falls below the injection switching feasibility determination temperature, the load on the gas turbine 10 is gradually reduced, allowing the gas turbine 10 to be stopped without significantly impacting the power transmission system or damaging the hot parts of the gas turbine 10.

[0094] In the above embodiment, the gas turbine 10 is tripped when the processes in S7 and S17 are performed. Process S7 is performed when the determination unit 22 determines "Yes" in the determination process in S6. This process is for emergency countermeasures, for example, in the case where the temperature of the sweep air rises rapidly in a short period of time. Process S17 is performed when there are no means other than tripping the gas turbine 10. In other words, the cases in which processes S7 and S17 are executed are quite limited. If we assume an example of operation where the determination unit 22 determines "No" in the determination process in S6 in Figure 4 and performs the process in S1 again, the probability of tripping the gas turbine 10 is lower in the operation example of the above embodiment compared to this example. Therefore, by using the control device 2, even when the temperature of the sweep air begins to rise, it is possible to avoid self-ignition of the fuel gas and prevent the gas turbine from tripping as much as possible.

[0095] (Supplemental configuration example of the embodiment) While embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include designs and other elements that do not depart from the gist of this disclosure.

[0096] In the above embodiment, the processes S6 and S7 in Figure 4 may be omitted, and the process S8 may be performed after the process S3. Even if the temperature of the sweep air rises rapidly in a short time, as long as the process is not switched from premixed combustion to diffusion combustion, the fuel gas and the sweep air will not come into contact, and the processes from the S8 onward can be performed.

[0097] If the processes in S6 and S7 are excluded, the operating maintenance feasibility determination temperature may be set to any temperature below the autoignition temperature of the fuel gas. For example, the autoignition prevention temperature may be set to the operating maintenance feasibility determination temperature, and the injection switching feasibility determination temperature may be set to any temperature below the operating maintenance feasibility determination temperature.

[0098] In the above embodiment, the reason why the fuel supply control unit 23 receives the first load reduction command signal and reduces the load of the gas turbine 10 to the lower limit of the operationally permissible load range is to attempt to reduce the sweep air temperature to the maximum extent possible. However, if the sweep air temperature falls below the injection switching feasibility determination temperature during the process of reducing the load of the gas turbine 10 to the lower limit of the operationally permissible load range, further load reduction is unnecessary and would result in an excessive reduction of power supplied to the power transmission system. Therefore, instead of reducing the load of the gas turbine 10 to the lower limit of the operationally permissible load range with a single first load reduction command signal, the load of the gas turbine 10 may be reduced in stages within the operationally permissible load range using multiple first load reduction command signals.

[0099] In this case, the determination unit 22 performs the processes S10, S11, and S12 in Figure 5 for each load reduction. If it determines "No" in the S12 process, it continues operating the gas turbine 10 without further load reduction. If the determination unit 22 determines "Yes" in the S12 process, it adds a process to determine whether the load on the gas turbine 10 is greater than the lower limit load of the operationally permissible load range. In this added determination process, if the determination unit 22 determines that the load on the gas turbine 10 is greater than the lower limit load of the operationally permissible load range, it performs the S9 process again. If it determines that the load on the gas turbine 10 is not greater than the lower limit load of the operationally permissible load range, it performs the S13 process.

[0100] The number of outputs of the first load reduction command signal and the amount of load reduction per first load reduction command signal may be determined as appropriate. For example, the number of outputs and the amount of load reduction per first load reduction command signal may be predetermined as fixed values. Alternatively, the determination unit 22 may determine, based on the load of the gas turbine 10 before the output of the first load reduction command signal, that is, immediately before the processing of the first S9, that the load reduction from the output of the final first load reduction command signal will match the lower limit load of the operational allowable load range. With such a configuration, it is possible to attempt to lower the temperature of the sweep air without excessively reducing the power supplied to the power transmission system.

[0101] In the above embodiment, the switching load is defined as the load of the gas turbine 10 corresponding to the lowest combustion temperature at which the flame can be maintained in premixed combustion, and the relationship "lower limit load of the operationally permissible load range = predetermined load > switching load" is assumed to hold. However, the switching load is not limited to the load of the gas turbine 10 corresponding to the lowest combustion temperature at which the flame can be maintained in premixed combustion. The switching load can be any load value as long as it is a combustion temperature at which the flame can be maintained in premixed combustion, and a combustion temperature at which premixed combustion and diffusion combustion can be switched to each other, and the relationship "lower limit load of the operationally permissible load range = predetermined load > switching load" holds. Furthermore, in the above embodiment, the load of the gas turbine 10 when switching from diffusion combustion to premixed combustion and the load of the gas turbine 10 when switching from premixed combustion to diffusion combustion are the same, and these two loads are defined as the "switching load". However, these two loads may be defined to be different. When the two loads are defined to be different, the term "switching load" refers to the load on the gas turbine 10 when switching from premixed combustion to diffusion combustion.

[0102] In the above embodiment, the sweep air is cooled by the cooler 5, but the sweep air may be cooled by means other than the cooler 5. Even in this configuration, by applying the control device 2, even if the temperature of the sweep air begins to rise, it is possible to avoid self-ignition of the fuel gas and prevent the gas turbine from tripping as much as possible.

[0103] In the above embodiment, three judgment criterion temperatures—a self-ignition prevention temperature, an operation maintenance feasibility determination temperature, and an injection switching feasibility determination temperature—stored in the memory unit 20 are used to determine whether the temperature of the swept air exceeds the respective judgment criterion temperature in each of the judgment processes S2, S6, S8, S12, and S16 in Figures 4 and 5. However, this judgment process is just one example, and depending on how the values ​​of the self-ignition prevention temperature, the operation maintenance feasibility determination temperature, and the injection switching feasibility determination temperature are determined, it may be replaced with a judgment process to determine whether the temperature of the swept air is equal to or greater than the judgment criterion temperature.

[0104] In the above embodiment, the first load reduction command signal and the second load reduction command signal may be command signals that utilize existing runback command signals or automatic stop command signals.

[0105] In the above embodiment, an example is shown in which the gas turbine 10 is equipped with one combustor 12, but multiple combustors 12 may be arranged in a ring shape around the rotor 14. In this case, the number of flow control valves 31-PD, 31-PP, 31-M and fuel supply passages 41-PD, 41-PP, 41-M will correspond to the number of combustors 12. When multiple combustors 12 are provided, the sweep air supply passage 40 between the cooler 5 and the flow control valve 30 branches to a number corresponding to the number of combustors 12, and the number of flow control valves 30 corresponding to the number of combustors 12 are installed at the branch ends. In other words, even when multiple combustors 12 are provided, the number of coolers 5 is one, and the number of temperature sensors 6 is also one. Therefore, since the temperature acquisition unit 21 receives the temperature of the sweep air from one temperature sensor 6, even when multiple combustors 12 are provided, the processing by the determination unit 22 is as shown in Figures 4 and 5. However, if multiple combustors 12 are provided, the number of flow control valves 30, 31-PD, 31-PP, and 31-M will match the number of combustors 12. Therefore, when the fuel supply control unit 23 receives a trip command signal, a first load reduction command signal, a second load reduction command signal, and an injection switching operation stop command signal from the determination unit 22, it will send a valve opening command signal to each of the flow control valves 30, 31-PD, 31-PP, and 31-M, in a number that matches the number of combustors 12, to adjust the opening degree of the flow control valves 30, 31-PD, 31-PP, and 31-M.

[0106] (Computer configuration) Figure 6 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 100 comprises a processor 101, main memory 102, storage 103, and interface 104. The control device 2 described above is implemented in the computer 100. The operation of each of the above-described processing units, namely the temperature acquisition unit 21, the determination unit 22, the fuel supply control unit 23, and the IGV control unit 24, is stored in the storage 103 in the form of a program. The processor 101 reads the program from the storage 103, loads it into the main memory 102, and executes the above processing according to the program. The processor 101 also reserves a storage area corresponding to the above-described storage unit 20 in the main memory 102 or storage 103 according to the program. The processor 101, in accordance with the program, connects the temperature acquisition unit 21 to the temperature sensor 6 via the interface 104, connects the fuel supply control unit 23 to the flow control valves 30, 31-PD, 31-PP, 31-M and the power meter 4 via the interface 104, and connects the IGV control unit 24 to the power meter 4, the temperature sensor 7 and the IGV 16 via the interface 104.

[0107] The program may be for implementing a part of the functions that the computer 100 is to perform. For example, the program may perform functions in combination with other programs already stored in the storage 103, or in combination with other programs implemented in other devices. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to, or instead of, the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. In this case, some or all of the functions implemented by the processor may be implemented by the integrated circuit.

[0108] Examples of storage 103 include HDD (Hard Disk Drive), SSD (Solid State Drive), magnetic disk, magneto-optical disk, CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), and semiconductor memory. Storage 103 may be an internal medium directly connected to the bus of computer 100, or an external medium connected to computer 100 via interface 104 or a communication line. Furthermore, if this program is distributed to computer 100 via a communication line, computer 100 that receives the distribution may expand the program into main memory 102 and execute the above processing. In at least one embodiment, storage 103 is a tangible storage medium that is not temporary.

[0109] <Note> The control device 2 described in the embodiment of this disclosure can be understood, for example, as follows:

[0110] (1) The control device 2 according to the first embodiment includes: a temperature acquisition unit 21 that acquires the temperature of the sweep air supplied to a pilot nozzle 50 that injects fuel gas in either premixed injection when premixed combustion is performed or diffusion injection when diffusion combustion is performed; a determination unit 22 that determines whether or not to maintain operation of the gas turbine 10 based on a predetermined operation maintenance feasibility determination temperature in a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition unit; and a fuel supply control unit 23 that, if the determination unit determines, based on the operation maintenance feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that operation of the gas turbine should not be maintained, reduces the load of the gas turbine within the range of the allowable operational load range that is permitted when operating the gas turbine. According to this embodiment and the following embodiments, even if the temperature of the sweep air begins to rise, it is possible to avoid autoignition of the fuel gas and prevent the gas turbine from tripping as much as possible.

[0111] (2) The control device 2 according to the second embodiment is the control device of (1), wherein the injection switching feasibility determination temperature is predetermined in a range below the autoignition temperature of the fuel gas, and the operation maintenance feasibility determination temperature is predetermined in a range below the autoignition temperature and above the injection switching feasibility determination temperature, and the determination unit determines whether or not to maintain the operation of the gas turbine based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit when the fuel supply control unit maintains the operation of the gas turbine with the load of the gas turbine reduced within the range of the allowable operational load band, and the fuel supply control unit reduces the load of the gas turbine to the switching load, which is the load when switching from the premixed combustion to the diffusion combustion, when the determination unit determines, based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that the operation of the gas turbine should not be maintained, and the fuel supply control unit reduces the load of the gas turbine to the switching load, which is the load when switching from the premixed combustion to the diffusion combustion. According to this embodiment, if the temperature of the sweep air decreases as a result of reducing the load of the gas turbine 10 within the range of the allowable operational load band, it is possible to determine whether or not to maintain the operation of the gas turbine 10 according to the reduced temperature of the sweep air. If it is determined that the operation of the gas turbine 10 should be maintained, the operation of the gas turbine 10 can be continued. If it is determined that the operation of the gas turbine 10 should not be maintained, the load of the gas turbine 10 can be further reduced to the switching load in an attempt to lower the temperature of the sweep air.

[0112] (3) The control device 2 according to the third embodiment is the control device of (2), wherein the determination unit determines whether it is possible to switch from premixed combustion to diffusion combustion based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit when the fuel supply control unit maintains operation of the gas turbine with the load of the gas turbine reduced to the switching load, and if the determination unit determines that it is possible to switch from premixed combustion to diffusion combustion, the fuel supply control unit switches the injection of the pilot nozzle from premixed injection to diffusion injection, and after the switch, reduces the load of the gas turbine and stops the operation of the gas turbine. According to this embodiment, if the temperature of the sweep air decreases as a result of reducing the load of the gas turbine 10 to the switching load, it is possible to determine whether it is possible to switch from premixed combustion to diffusion combustion according to the decreased temperature of the sweep air, and if it is determined that it is possible to switch from premixed combustion to diffusion combustion, the gas turbine 10 can be stopped without tripping.

[0113] (4) The control device 2 according to the fourth embodiment is the control device according to (3), wherein the fuel supply control unit stops supplying the fuel gas to the gas turbine and stops the operation of the gas turbine when the determination unit determines that it is not possible to switch the injection of the pilot nozzle from the premixed injection to the diffusion injection. According to this embodiment, if the temperature of the sweep air does not decrease sufficiently even with a two-stage load reduction, which is a load reduction within the range of the operational allowable load range and a load reduction up to the switching load, the gas turbine 10 can be tripped as a last resort.

[0114] (5) The control device 2 according to the fifth embodiment is any one of the control devices from (1) to (4), wherein the fuel supply control unit reduces the load of the gas turbine to the lower limit load of the permissible operating load range when the determination unit determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that the operation of the gas turbine should not be maintained. According to this embodiment, by reducing the load of the gas turbine 10 to the lower limit load of the permissible operating load range, an attempt can be made to reduce the sweep air temperature to the maximum extent possible.

[0115] (6) The control device 2 according to the sixth embodiment is any one of the control devices from (1) to (5), wherein the sweep air is supplied to the pilot nozzle via a cooling means (e.g., a cooler 5) that cools the sweep air, and the temperature acquisition unit acquires the temperature of the sweep air from a temperature sensor that measures the temperature of the sweep air after it has passed through the cooling means and before it flows into the pilot nozzle. According to this embodiment, for example, even if the temperature of the sweep air starts to rise due to a malfunction of the cooling means, it is possible to avoid self-ignition of the fuel gas and to prevent the gas turbine from tripping as much as possible. [Explanation of Symbols]

[0116] 1…Gas turbine power plant 2…Control device 3…Fuel gas supply device 4…Power meter 5...Cooler 6,7…Temperature sensor 10... Gas turbine 11…Air compressor 12… Combustor 13... Turbine 14…Rota 15…Generator 16…IGV 17… Combustion chamber 18...Inner cylinder of the combustion chamber 20...Storage section 21…Temperature acquisition section 22…Judgment section 23…Fuel Supply Control Unit 24…IGV Control Unit 30, 31-PD, 31-PP, 31-M… Flow control valves 50…Pilot nozzle 51-1,51-2,52-1,52-2…Injection hole 60... Main nozzle 61-1,61-2…Injection hole

Claims

1. A pilot nozzle that injects fuel gas in either premixed injection for premixed combustion or diffusion injection for diffusion combustion, and when the pilot nozzle is performing the premixed injection, a temperature acquisition unit acquires the temperature of the sweep air supplied to the pilot nozzle, A determination unit that determines whether or not to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition unit, If the determination unit determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that the operation of the gas turbine should not be maintained, the fuel supply control unit reduces the load on the gas turbine within the range of the permissible operating load range that is permitted when operating the gas turbine. A control device for a gas turbine equipped with [a specific feature / feature].

2. A temperature for determining whether injection switching is possible is predetermined within a range below the autoignition temperature of the fuel gas. The aforementioned temperature for determining whether operation can be maintained is, A range is predetermined that is below the self-ignition temperature and above the injection switching feasibility determination temperature, The determination unit, When the fuel supply control unit maintains the operation of the gas turbine with the load of the gas turbine reduced within the range of the permissible operational load band, it determines whether or not to maintain the operation of the gas turbine based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit. The fuel supply control unit, If the determination unit determines, based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that it will not maintain the operation of the gas turbine, it will reduce the load on the gas turbine to the switching load, which is the load when switching from the premixed combustion to the diffusion combustion. The control device for a gas turbine according to claim 1.

3. The determination unit, When the fuel supply control unit maintains the operation of the gas turbine with the load of the gas turbine reduced to the switching load, it determines whether or not it is possible to switch from the premixed combustion to the diffusion combustion based on the injection switching feasibility determination temperature and the temperature acquired by the temperature acquisition unit. The fuel supply control unit, If the determination unit determines that it is possible to switch from the premixed combustion to the diffusion combustion, it switches the injection of the pilot nozzle from the premixed injection to the diffusion injection, and after the switch, it reduces the load on the gas turbine and stops the operation of the gas turbine. The control device for a gas turbine according to claim 2.

4. The fuel supply control unit, If the determination unit determines that it is not possible to switch from the premixed combustion to the diffusion combustion, it stops the supply of the fuel gas to the gas turbine and stops the operation of the gas turbine. The control device for a gas turbine according to claim 3.

5. The fuel supply control unit, If the determination unit determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition unit, that the operation of the gas turbine should not be maintained, then the load of the gas turbine is reduced to the lower limit load of the operating allowable load range. The control device for a gas turbine according to claim 1.

6. The swept air is supplied to the pilot nozzle via a cooling means for cooling the swept air. The temperature acquisition unit is, The temperature of the swept air is obtained from a temperature sensor that measures the temperature of the swept air after it has passed through the cooling means and before it flows into the pilot nozzle. The control device for a gas turbine according to claim 1.

7. When a pilot nozzle that injects fuel gas in either premixed injection for premixed combustion or diffusion injection for diffusion combustion is performing the aforementioned premixed injection, the temperature of the sweep air supplied to the pilot nozzle is obtained. Based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the acquired sweep air temperature, a determination is made as to whether or not to maintain operation of the gas turbine. If, based on the temperature used for determining whether operation can be maintained and the acquired temperature of the swept air, it is determined that operation of the gas turbine should not be maintained, the load on the gas turbine is reduced within the range of the permissible operational load range that is permitted when operating the gas turbine. A method for controlling a gas turbine.

8. Computers, A pilot nozzle that injects fuel gas in either premixed injection for premixed combustion or diffusion injection for diffusion combustion is performing the aforementioned premixed injection, and a temperature acquisition means for acquiring the temperature of the sweep air supplied to the pilot nozzle. A determination means that determines whether or not to maintain operation of the gas turbine based on a predetermined operating feasibility determination temperature within a range below the autoignition temperature of the fuel gas and the temperature acquired by the temperature acquisition means. If the determination means determines, based on the operating feasibility determination temperature and the temperature acquired by the temperature acquisition means, that the operation of the gas turbine should not be maintained, then the fuel supply control means reduces the load on the gas turbine within the range of the permissible operating load range that is permitted when operating the gas turbine. A program designed to function as such.

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