Gas turbine control method

Abstract

To inexpensively eliminate drain stagnation in a fuel supply line to which fuel is not supplied.SOLUTION: This invention relates to a method for controlling a gas turbine including a combustor that has a fuel injection nozzle with a premixed fuel injection hole for injecting fuel supplied from a fuel supply system as premixed fuel for combustion in a premixing method and a diffusion fuel injection hole for injecting the fuel as diffusion fuel for combustion in a diffusion method. In the method, in a low-load operating region in which a load of the gas turbine is first load or smaller, the premixed fuel is supplied to the premixed fuel injection hole at a first flow rate and the diffusion fuel is supplied to the diffusion fuel injection hole at a second flow rate larger than the first flow rate.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a gas turbine control method. [Background technology]

[0002] A gas turbine can generate power by driving a turbine using combustion gas produced by a combustor. The combustor has fuel injection nozzles for injecting fuel into a combustion chamber to combust the fuel supplied from a fuel supply system. The fuel injection nozzles provided in a combustor typically include a pilot nozzle and a main nozzle. The pilot nozzle combusts the injected fuel to generate a flame that serves as a pilot for combustion by the main nozzle.

[0003] These fuel injection nozzles are provided with multiple fuel injection holes for injecting fuel supplied from a fuel supply system via a fuel supply line. When different types of fuel injection holes are provided depending on the application, a configuration may be used in which the fuel supplied via the fuel supply line can be branched and supplied independently to each fuel injection hole. For example, a pilot nozzle, which is one type of fuel injection nozzle, may have premix fuel injection holes for injecting premixed fuel for premixed combustion and diffusion fuel injection holes for injecting diffusion fuel for diffusion combustion. In this case, the fuel from the fuel supply system is branched and supplied to the premix fuel injection holes as premixed fuel and to the diffusion fuel injection holes as diffusion fuel.

[0004] In a fuel injection nozzle having fuel supply lines that can supply fuel independently, if a period of time continues in which fuel is not supplied to some of the fuel supply lines, drainage may accumulate in those lines. Patent Document 1 discloses a gas turbine that is equipped with drainage treatment means for discharging drainage that has accumulated in such fuel supply lines that are not supplied with fuel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-73783 Summary of the Invention [Problem to be solved by the invention]

[0006] In each of the above Patent Documents 1, a drain treatment means is additionally provided to the gas turbine in order to discharge drainage accumulated in the fuel supply line where fuel is not being supplied. However, the additional provision of such a drain treatment means is a factor in increasing the equipment cost.

[0007] At least one embodiment of the present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a gas turbine control method that can eliminate, at low cost, drain accumulation in a fuel supply line to which fuel is not supplied. [Means for solving the problem]

[0008] In order to solve the above problem, a gas turbine control method according to at least one embodiment of the present disclosure includes: A gas turbine control method for controlling a gas turbine equipped with a combustor including a fuel injection nozzle having premixed fuel injection holes for injecting fuel supplied from a fuel supply system as premixed fuel for combustion in a premixed system, and diffusion fuel injection holes for injecting fuel as diffusion fuel for combustion in a diffusion system, the method comprising: In a low load operating region where the load of the gas turbine is equal to or less than a first load, the premixed fuel is supplied to the premixed fuel injection holes at a first flow rate, and the diffusion fuel is supplied to the diffusion fuel injection holes at a second flow rate greater than the first flow rate. [Effects of the Invention]

[0009] According to at least one embodiment of the present disclosure, it is possible to provide a gas turbine control method that can eliminate drain accumulation in a fuel supply line to which fuel is not supplied at low cost. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic configuration diagram of a gas turbine according to an embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram showing a fuel injection nozzle provided in the combustor of FIG. [Figure 3] 10 is a graph showing the flow rates of premixed fuel and diffusion fuel relative to the load of the gas turbine in a gas turbine control method according to a comparative example. [Figure 4] 1 is a graph illustrating premixed fuel and diffusion fuel flow rates versus gas turbine load in an embodiment of a method for controlling a gas turbine. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the configurations described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0012] First, a gas turbine 1 that is a control target of a gas turbine control method according to at least one embodiment of the present disclosure will be described. Fig. 1 is a schematic configuration diagram of a gas turbine 1 according to one embodiment.

[0013] The gas turbine 1 includes a compressor 2, a combustor 4, and a turbine 6. The compressor 2 generates compressed air as combustion air A by compressing air drawn in from the outside. The combustor 4 generates combustion gas Gc by mixing and burning fuel F supplied from a fuel supply system 8 with the combustion air A supplied from the compressor 2. The combustion gas Gc generated in the combustor 4 is sent to the turbine 6, thereby driving the turbine 6. The compressor 2 and the turbine 6 are connected to each other by a common rotating shaft 5.

[0014] The fuel supply system 8 is configured to be able to supply fuel F from a fuel supply source 12 to the combustor 4 via a fuel supply line 10. A flow rate control valve 14 for adjusting the amount of fuel F supplied to the combustor 4 and a shutoff valve 16 for shutting off the fuel F are respectively arranged on the fuel supply line 10.

[0015] The gas turbine 1 having such a configuration may form a gas turbine combined plant (not shown) together with, for example, a heat recovery boiler and a steam turbine driven by steam generated by the heat recovery boiler. In this case, in the gas turbine combined plant, the gas turbine 1 is used as a topping cycle, and the heat recovery boiler and the steam turbine are used as a bottoming cycle.

[0016] Fig. 2 is a schematic configuration diagram showing the fuel injection nozzles 20 included in the combustor 4 of Fig. 1. The combustor 4 is equipped with a plurality of fuel injection nozzles 20 for injecting fuel F supplied from a fuel supply system 8 into a combustion chamber (not shown) for mixing and burning the fuel F with combustion air A supplied from the compressor 2.

[0017] The combustor 4 includes a pilot nozzle 20a and a main nozzle 20b as the multiple fuel injection nozzles 20. The multiple main nozzles 20b are arranged circumferentially around the outer periphery of the pilot nozzle 20a. The pilot nozzle 20a is a fuel injection nozzle for forming a flame used as a spark for combustion by the main nozzles 20b. The fuel supply line 10 described above with reference to FIG. 1 branches into a pilot nozzle fuel supply line 22 and a main nozzle fuel supply line 28, which are connected to the pilot nozzle 20a and the main nozzle 20b, respectively.

[0018] The pilot nozzle 20a has a plurality of pilot nozzle fuel supply lines 22 branching off from the fuel supply line 10, a pilot nozzle body 24 containing the plurality of pilot nozzle fuel supply lines 22, and a pilot nozzle injection hole (injection hole) 26 provided at the downstream tip of the pilot nozzle body 24.

[0019] The pilot nozzle body 24 is disposed along the flow direction of the combustion air A in the combustor 4. The multiple pilot nozzle fuel supply lines 22 contained within the pilot nozzle body 24 include a premixed fuel supply line 22a used in the premixing method and a diffusion fuel supply line 22b used in the diffusion method.

[0020] The premixed fuel supply line 22a is supplied with fuel F from the fuel supply system 8 as premixed fuel F1. A premixed fuel injection hole 26a for injecting the premixed fuel F1 is provided at the downstream end of the premixed fuel supply line 22a. The diffusion fuel supply line 22b is supplied with fuel F from the fuel supply system 8 as diffusion fuel F2. A diffusion fuel injection hole 26b for injecting the diffusion fuel F2 is provided at the downstream end of the diffusion fuel supply line 22b. The premixed fuel injection hole 26a is provided upstream of the diffusion fuel injection hole 26b in the airflow inside the combustor 4.

[0021] As described above, the fuel F from the fuel supply line 10 of the fuel supply system 8 is branched and supplied to the premixed fuel supply line 22a and the diffusion fuel supply line 22b as premixed fuel F1 and diffusion fuel F2, respectively. The flow rate of the premixed fuel F1 supplied to the premixed fuel supply line 22a and the flow rate of the diffusion fuel F2 supplied to the diffusion fuel supply line 22b can be adjusted independently of each other.

[0022] The main nozzle 20b injects the fuel F from the fuel supply system 8 as main fuel F3 into the airflow in the combustor 4. The main nozzle 20b has a main-nozzle fuel supply line 28 that branches off from the fuel supply line 10 of the fuel supply system 8, a main-nozzle body 30 that contains the main-nozzle fuel supply line 28, and a main-nozzle injection hole 32 formed on the downstream side of the main-nozzle body 30.

[0023] The main nozzle body 30 is disposed on the outer circumferential side of the pilot nozzle body 24 along the airflow direction within the combustor 4. A main nozzle fuel supply line 28 contained within the main nozzle body 30 supplies the fuel F branched off from the fuel supply system 8 as the main fuel F3 used in the premixing system. Within the main nozzle body 30, the downstream end of the main nozzle fuel supply line 28 branches into multiple branches, each of which is provided with multiple main nozzle injection holes 32 for injecting the main fuel F3 guided from the main nozzle fuel supply line 28. These main nozzle injection holes 32 are disposed upstream in the airflow within the combustor 4 of the premix fuel injection holes 26a and the diffusion fuel injection holes 26b, which are the pilot nozzle injection holes described above. The main fuel F3 injected from the main nozzle fuel supply line 28 into the airflow burns using the flame generated by the pilot nozzle 20a as a pilot flame.

[0024] Next, a control method for controlling the gas turbine 1 having the above configuration will be described. As described above, the pilot nozzle 20a of the combustor 4 of the gas turbine 1 has the premixed fuel injection holes 26a to which premixed fuel F1 for premixed combustion is supplied, and the diffusion fuel injection holes 26b to which diffusion fuel F2 for diffusion combustion is supplied. The flow rates of the premixed fuel F1 and the diffusion fuel F2 are controlled based on the load L of the gas turbine 1.

[0025] 3 is a graph showing the flow rates of the premixed fuel F1 and the diffusion fuel F2 relative to the load L of the gas turbine 1 in a gas turbine control method according to a comparative example. In the comparative example, in a region where the load L is less than a first load L1, the flow rate of the premixed fuel F1 is controlled to zero, and the flow rate of the diffusion fuel F2 is controlled to decrease monotonically in accordance with the load L. On the other hand, in a region where the load L is equal to or greater than the first load L1, the flow rate of the premixed fuel F1 is controlled to decrease monotonically in accordance with the load L, and the flow rate of the diffusion fuel F2 is controlled to zero. In this way, in the comparative example, control is performed to switch between the premixed fuel F1 and the diffusion fuel F2, with the first load L1 as the boundary.

[0026] If the load L is in a low-load operating region defined as between a first load L1 and a second load L2 that is smaller than the first load L1, and this operating state continues for a long period of time, drainage may accumulate in the premixed fuel supply line 22a, through which the premixed fuel F1 does not flow. Such drainage accumulation can be suitably eliminated by the control method described below.

[0027] FIG. 4 is a graph showing the flow rates of premixed fuel F1 and diffusion fuel F2 relative to the load L of the gas turbine 1 in a gas turbine control method according to one embodiment. In this embodiment, when the load L of the gas turbine 1 is in a low-load operating range, premixed fuel F1 is supplied to the premixed fuel injection holes 26a, and diffusion fuel F2 is supplied to the diffusion fuel injection holes 26b. At this time, the flow rate of premixed fuel F1 (first flow rate) is controlled to be smaller than the flow rate of diffusion fuel F2 (second flow rate). That is, in the comparative example described above, only diffusion fuel F2 was supplied in the low-load operating range, and premixed fuel F1 was not supplied, which could cause drain retention in the premixed fuel supply line 22a. In contrast, in this embodiment, not only diffusion fuel F2 but also premixed fuel F1 is supplied, albeit at a relatively small flow rate. As a result, even if the load L of the gas turbine 1 continues to remain within the low load operating region for a long period of time, by supplying the premixed fuel F1 to the premixed fuel supply line 22a at a small flow rate, it is possible to effectively prevent drainage from accumulating in the premixed fuel supply line 22a.

[0028] In the low load operation region, the first flow rate of the premixed fuel F1 supplied to the premixed fuel supply line 22a may be 3% or less of the total flow rate of the fuel F supplied from the fuel supply system 8 to the combustor 4. By minimizing the flow rate of the premixed fuel F1 supplied to the premixed fuel injection holes 26a in this way, the influence on the operation of the gas turbine 1 in the low load operation region can be reduced, and drainage accumulation in the premixed fuel supply line 22a can be suitably prevented.

[0029] In the present embodiment, an example is illustrated in which the low-load operation region is defined by a preset first load L1 and second load L2. However, such a low-load operation region may be qualitatively defined as a region where drain stagnation may occur in the premixed fuel supply line 22a when the operation state stagnates on the low-load side, based on the operation status of the gas turbine 1. In this case, the low-load operation region can be appropriately set based on the planned data or past performance data indicating the operation status of the gas turbine 1. Generally, the load L of the gas turbine 1 can vary in various operation patterns. For example, when the load L of the gas turbine 1 exhibits a behavior of decreasing over time, if drain stagnation is likely to occur, the low-load operation region may be set hysteretically when the load L decreases.

[0030] Also, when the load L of the gas turbine 1 is below the second load L2 (<L1) corresponding to the lower limit load value defining the low-load operation region, the supply of the premixed fuel F1 to the premixed fuel injection hole 26a may be stopped. In the operation region where the load L is below the second load L2, since drain stagnation hardly occurs in the premixed fuel supply line 22a, unnecessary fuel consumption can be suppressed by stopping the supply of the premixed fuel F1 to the premixed fuel injection hole 26a.

[0031] Incidentally, the first load L1 corresponding to the upper limit load value of the low-load operation region may be set, for example, between 30% and 40% of the rated load of the gas turbine. Also, the second load L2 corresponding to the lower limit load value of the low-load operation region may be set between 20% and 30% of the rated load of the gas turbine 1.

[0032] In addition, without departing from the spirit of the present disclosure, it is possible to appropriately replace the components in the above-described embodiment with well-known components, and the above-described embodiments may also be appropriately combined.

[0033] The content described in each of the above embodiments is understood, for example, as follows.

[0034] (1) The gas turbine control method according to one aspect is A gas turbine control method for controlling a gas turbine equipped with a combustor including a fuel injection nozzle having premixed fuel injection holes for injecting fuel supplied from a fuel supply system as premixed fuel for combustion in a premixed system, and diffusion fuel injection holes for injecting fuel as diffusion fuel for combustion in a diffusion system, the method comprising: In a low load operating region where the load of the gas turbine is equal to or less than a first load, the premixed fuel is supplied to the premixed fuel injection holes at a first flow rate, and the diffusion fuel is supplied to the diffusion fuel injection holes at a second flow rate greater than the first flow rate.

[0035] According to the above aspect (1), a fuel injection nozzle provided in a combustor of a gas turbine is provided with premixed fuel injection holes for injecting premixed fuel for premixed combustion and diffusion fuel injection holes for injecting diffusion fuel for diffusion combustion. When the operating state of the gas turbine is in the low-load operating range, diffusion fuel is mainly supplied to the diffusion fuel injection holes. At this time, premixed fuel is supplied to the premixed fuel injection holes at a first flow rate that is less than the second flow rate of the diffusion fuel to the diffusion fuel injection holes. As a result, even when the gas turbine continues to operate in the low-load operating range, a considerable amount of premixed fuel is supplied to the fuel supply line connected to the premixed fuel injection holes, thereby effectively preventing drain from accumulating in the line.

[0036] (2) In another embodiment, in the above embodiment (1), The low load operating region is defined as an operating region in which the load of the gas turbine remains equal to or lower than the first load for a predetermined period of time or more.

[0037] According to the above aspect (2), the low-load operating region is defined as a region in which an operating state in which the load of the gas turbine is equal to or less than a first load continues for a predetermined period of time or more. When an operating state in which the load of the gas turbine is equal to or less than the first load continues for a predetermined period of time or more, if the supply of premixed fuel to a fuel supply line connected to the premixed fuel injection holes is completely stopped, drainage is likely to accumulate in the line. In this aspect, by supplying at least a small amount of premixed fuel to the fuel supply line connected to the premixed fuel injection holes in such a case, drainage can be effectively prevented from accumulating in the line.

[0038] (3) In another aspect, in the above aspect (1) or (2), The low load operating region is defined as an operating region in which the load on the gas turbine decreases over time.

[0039] According to the aspect (3) above, the low-load operating region is defined as a region in which the load of the gas turbine becomes equal to or less than a first load as the load of the gas turbine decreases over time. If the load of the gas turbine decreases over time and becomes equal to or less than the first load, completely stopping the supply of premixed fuel to a fuel supply line connected to the premixed fuel injection holes would result in drain accumulation in the line. In this aspect, by supplying at least a small amount of premixed fuel to the fuel supply line connected to the premixed fuel injection holes in such a case, drain accumulation in the line can be effectively prevented.

[0040] (4) In another embodiment, in any one of the above (1) to (3), The first load is set to between 30% and 40% of the rated load of the gas turbine.

[0041] According to the above aspect (4), the upper limit load value of the low load operation region is set between 30 and 40% of the rated load.

[0042] (5) In another embodiment, in any one of the above (1) to (4), The first flow rate is 3% or less of the total flow rate of the fuel supplied from the fuel supply system to the combustor.

[0043] According to the above aspect (5), in the low load operating range, the flow rate of premixed fuel supplied to the premixed fuel injection holes is kept to 3% or less of the total flow rate of fuel supplied from the fuel supply system. By keeping the flow rate of premixed fuel supplied to the premixed fuel injection holes to a minimum in this way, it is possible to effectively prevent drainage from remaining in the line for supplying the fuel flow rate to the premixed fuel injection holes while suppressing the effect on the operation of the gas turbine in the low load operating range.

[0044] (6) In another embodiment, in any one of the above (1) to (5), When the load of the gas turbine is equal to or less than a second load which is smaller than the first load, the supply of the premixed fuel to the premixed fuel injection holes is stopped.

[0045] According to the above aspect (6), in the operating range where the load of the gas turbine is equal to or less than the second load, drain is less likely to accumulate in the line that supplies premixed fuel to the premixed fuel injection hole, and therefore, by stopping the supply of premixed fuel to the premixed fuel injection hole, unnecessary fuel consumption can be suppressed.

[0046] (7) In another embodiment, in the above embodiment (6), The second load is set to between 20% and 30% of the rated load of the gas turbine.

[0047] According to the above aspect (7), in an operating range where the gas turbine is operating at 20 to 30% or less of the rated load, the supply of the premixed fuel to the premixed fuel injection holes is stopped, thereby making it possible to suppress unnecessary fuel consumption.

[0048] (8) In another embodiment, in any one of the above (1) to (7), The fuel injection nozzle is a pilot nozzle for forming a flame used as a spark for combustion by the main nozzle.

[0049] According to the above aspect (8), in the pilot nozzle for forming a flame used as a spark for combustion by the main nozzle, it is possible to suitably prevent drain retention in the line for supplying fuel flow to the premixed fuel injection hole in the low load operating range.

[0050] (9) In another embodiment, in any one of the above (1) to (8), The gas turbine, together with a heat recovery steam generator and a steam turbine driven by steam generated by the heat recovery steam generator, constitutes a combined cycle plant.

[0051] According to the above aspect (9), in a gas turbine constituting a combined cycle plant, it is possible to effectively prevent drainage from remaining in a line for supplying fuel flow rate to a premixed fuel injection hole in a low load operating region. [Explanation of symbols]

[0052] 1. Gas turbine 2 Compressor 4 Combustor 5 Rotation Axis 6 Turbine 8 Fuel supply system 10 Fuel supply line 12 Fuel supply source 14 Flow control valve 16. Shut-off valve 20 fuel injection nozzle 20a Pilot Nozzle 20b Main nozzle 22 Pilot nozzle fuel supply line 22a Premix fuel supply line 22b Diffusion fuel supply line 24 Pilot nozzle body 26a Premix fuel injection hole 26b Diffusion fuel injection hole 28 Main nozzle fuel supply line 30 Main nozzle body 32 Main nozzle injection hole A Combustion air F fuel F1 premixed fuel F2 diffusion fuel F3 Main Fuel Gc Combustion gas L1 1st load L2 2nd load

Claims

1. A gas turbine control method for controlling a gas turbine equipped with a combustor including a fuel injection nozzle having premixed fuel injection holes for injecting fuel supplied from a fuel supply system as premixed fuel for combustion in a premixed system, and diffusion fuel injection holes for injecting fuel as diffusion fuel for combustion in a diffusion system, the method comprising: a first flow rate of the premixed fuel to the premixed fuel injection holes and a second flow rate of the diffusion fuel to the diffusion fuel injection holes, the second flow rate being greater than the first flow rate, in a low load operation region where a load of the gas turbine is equal to or less than a first load.

2. 2. The gas turbine control method according to claim 1, wherein the low load operating region is defined as an operating region in which a state in which the load of the gas turbine is equal to or lower than the first load continues for a predetermined period of time or more.

3. 3. The gas turbine control method according to claim 1, wherein the low load operating region is defined as an operating region in which the load of the gas turbine decreases with time.

4. 3. The gas turbine control method according to claim 1, wherein the first load is set to between 30% and 40% of a rated load of the gas turbine.

5. 3. The gas turbine control method according to claim 1, wherein the first flow rate is 3% or less of a total flow rate of the fuel supplied from the fuel supply system to the combustor.

6. 3. The gas turbine control method according to claim 1, further comprising the step of: stopping supply of the premixed fuel to the premixed fuel injection holes when a load of the gas turbine is equal to or less than a second load that is smaller than the first load.

7. 7. The gas turbine control method according to claim 6, wherein the second load is set to between 20% and 30% of a rated load of the gas turbine.

8. 3. The gas turbine control method according to claim 1, wherein the fuel injection nozzle is a pilot nozzle for forming a flame used as a spark for combustion by a main nozzle.

9. 3. The gas turbine control method according to claim 1, wherein the gas turbine forms a combined cycle plant together with a heat recovery boiler and a steam turbine driven by steam generated by the heat recovery boiler.

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