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

Abstract

Without any cooling mechanism, the temperature of the swept air is lowered to a level where the fuel gas will not self-ignite. [Solution] The fuel supply control unit selects between a first switching process, which stops the supply of fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplies air flowing out of the air compressor as sweep air to the predetermined fuel supply path, and a second switching process, which stops the supply of sweep air to the predetermined fuel supply path and supplies fuel gas to the predetermined fuel supply path. The IGV control unit performs a process as a preprocessing step when the fuel supply control unit selects between the first and second switching processes, which involves adjusting the IGV opening degree according to the IGV opening degree specified based on a characteristic that indicates the IGV opening degree for each ambient temperature, wherein the sweep air temperature is set to a predetermined self-ignition prevention temperature for the fuel gas, and the ambient temperature measured by a temperature sensor.

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] There is known a dual-fuel fired gas turbine that can switch the fuel to be burned in a combustor between fuel gas and fuel oil while continuing operation. In this gas turbine, when oil-fired operation is performed, there is a risk that high-temperature combustion gas may flow backward through the injection holes of the pilot nozzles where the injection of fuel gas has been stopped, burning out the pilot nozzles. Therefore, by supplying the air extracted from the cabin of the combustor as sweep air to the fuel supply path of the pilot nozzles that guide fuel gas, the backward flow of combustion gas is prevented so that the pilot nozzles are not burned out.

[0003] By the way, when switching from fuel gas to fuel oil and when switching from fuel oil to fuel gas, there is a timing at which the sweep air and the fuel gas come into contact in the fuel supply path of the pilot nozzles that guide fuel gas. If the temperature of the sweep air becomes equal to or higher than the autoignition temperature of the fuel gas when they come into contact, there is a risk that the fuel gas may ignite. Therefore, it is necessary to lower the temperature of the sweep air to a temperature at which the fuel gas does not autoignite. For example, in Patent Document 1, a technique of cooling the sweep air extracted from the cabin of the combustor using cooling means is disclosed.

Prior Art Documents

[0006] 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 can lower the temperature of the sweep air to a temperature at which the fuel gas does not self-ignite without providing a cooling means. [Means for solving the problem]

[0007] To solve the above problems, the gas turbine control device according to the present disclosure includes a fuel supply control unit that selects and performs a first switching process which stops the supply of fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplies air flowing out of the air compressor as sweep air to the predetermined fuel supply path, and a second switching process which stops the supply of sweep air to the predetermined fuel supply path and supplies fuel gas to the predetermined fuel supply path. The fuel supply control unit includes an IGV control unit that performs a preprocessing step when selecting to perform the first switching process and the second switching process, which involves adjusting the opening of the IGV according to the opening of the IGV determined based on a characteristic that indicates the opening of the IGV for each ambient temperature, wherein the temperature of the sweep air is set to a predetermined autoignition prevention temperature for the fuel gas, and the ambient temperature measured by a temperature sensor.

[0008] The gas turbine control method according to this disclosure involves selecting between a first switching process, which involves stopping the supply of fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplying air flowing out of an air compressor as sweep air to the predetermined fuel supply path, and a second switching process, which involves stopping the supply of sweep air to the predetermined fuel supply path and supplying fuel gas to the predetermined fuel supply path. As a preprocessing step when selecting between the first and second switching processes, the method involves adjusting the opening degree of the IGV according to the opening degree of the IGV, which is determined based on a characteristic indicating the opening degree of the IGV for each ambient temperature, which sets the temperature of the sweep air to a predetermined autoignition prevention temperature for the fuel gas, and the ambient temperature measured by a temperature sensor.

[0009] The program relating to this disclosure is a program for causing a computer to function as a fuel supply control means that selects between a first switching process, which stops the supply of the fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplies air flowing out of an air compressor as sweep air to the predetermined fuel supply path, and a second switching process, which stops the supply of the sweep air to the predetermined fuel supply path and supplies the fuel gas to the predetermined fuel supply path. The program also includes an IGV control means that, as a preprocessing step when the fuel supply control means selects to perform the first switching process and the second switching process, performs a process of adjusting the opening of the IGV according to the opening of the IGV, which is determined based on a characteristic that indicates the opening of the IGV for each ambient temperature, which sets the temperature of the sweep air to a predetermined self-ignition prevention temperature for the fuel gas, and the ambient temperature measured by a temperature sensor. [Effects of the Invention]

[0010] According to the gas turbine control device, gas turbine control method, and program of this disclosure, the temperature of the sweep air can be reduced to a temperature at which the fuel gas does not self-ignite without the need for a cooling means. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing an example configuration of a gas turbine power plant according to the present disclosure. [Figure 2] This is a schematic diagram of a pilot nozzle and a main nozzle according to an embodiment of the present disclosure. [Figure 3] This graph shows the relationship between atmospheric temperature and IGV opening degree according to the embodiment of this disclosure. [Figure 4] This flowchart shows an example of the operation of a control device when switching from fuel gas to fuel oil according to the embodiment of this disclosure. [Figure 5] This flowchart shows an example of the operation of a control device when switching from fuel oil to fuel gas according to the embodiment of this disclosure. [Figure 6] This is a block diagram showing an example of the configuration of a pilot nozzle according to a modified embodiment of the present disclosure. [Figure 7] This is a schematic block diagram showing the configuration of a computer according to at least one embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, the control device, gas turbine control method, and program of the gas turbine according to the embodiments of this disclosure will be described with reference to the figures. In each figure, the same or corresponding components are given the same reference numerals, and their descriptions will be omitted as appropriate.

[0013] (Example of a gas turbine power plant configuration) Figure 1 is a block diagram showing an example configuration of a gas turbine power plant 1 according to one embodiment of the present disclosure. The gas turbine power plant 1 comprises a control device 2, a fuel gas supply device 3, a fuel oil supply device 4, a power meter 5, a temperature sensor 6, a gas turbine 10, and flow control valves 30, 31-P, 31-M, 32-P, and 32-M. In Figure 1, solid connecting lines indicate the piping routes through which fuel gas, fuel oil, or sweep air flows, and dotted connecting lines indicate the wiring routes through which electrical signals are transmitted and received.

[0014] The fuel gas supply device 3 stores fuel gas such as natural gas, for example, and supplies fuel gas to the gas turbine 10 via the flow control valves 31-P and 31-M. The fuel oil supply device 4 stores fuel oil such as heavy oil, for example, and supplies fuel oil to the gas turbine 10 via the flow control valves 32-P and 32-M.

[0015] The flow control valve 31-P is connected to the fuel gas supply device 3 via a pipe at one end and to the fuel supply line 41-P at the other end. The flow control valve 31-M is connected to the fuel gas supply device 3 via a pipe at one end and to the fuel supply line 41-M at the other end. The flow control valves 31-P and 31-M are electrically connected to the control device 2 and, when receiving a valve opening command signal from the control device 2, open and close the valve so as to have the valve opening shown in the received valve opening command signal, thereby adjusting the flow rate of the fuel gas.

[0016] The flow control valve 32-P is connected to the fuel oil supply device 4 via a pipe at one end and to the fuel supply line 42-P at the other end. The flow control valve 32-M is connected to the fuel oil supply device 4 via a pipe at one end and to the fuel supply line 42-M at the other end. The flow control valves 32-P and 32-M are electrically connected to the control device 2 and, when receiving a valve opening command signal from the control device 2, open and close the valve so as to have the valve opening shown in the received valve opening command signal, thereby adjusting the flow rate of the fuel oil.

[0017] The gas turbine 10 includes an air compressor 11, a combustor 12, a turbine 13, a rotor 14, and a generator 15. The air compressor 11 inhales and compresses air from the outside as indicated by the dashed arrow due to the rotation of the rotor 14 that penetrates the air compressor 11 and the turbine 13, and the compressed air flows out to the combustor 12.

[0018] The combustor 12 includes a combustor chamber 18 into which the air flowing out from the air compressor 11 flows, and a combustor inner cylinder 19 into which the air flowing out from the combustor chamber 18 flows. The air flowing into the combustor inner cylinder 19 flows from the upper side of the combustor inner cylinder 19 to which the fuel supply paths 41-P, 41-M, 42-P, and 42-M are connected, as indicated by the dashed arrow, toward the lower side of the combustor inner cylinder 19 provided with an opening through which the combustion gas flows out toward the turbine 13.

[0019] As shown in FIG. 2, the combustor inner cylinder 19 includes a pilot nozzle 50 and a main nozzle 60 inside. In FIG. 2, the direction of the arrow indicated by AF is the direction in which the air flows inside the combustor inner cylinder 19 (hereinafter referred to as the air flow direction AF). The pilot nozzle 50 and the main nozzle 60 have a shape having a longitudinal direction, and FIG. 2 is a view of a plane parallel to the longitudinal direction and including the central axis of each, schematically showing a cross section when each of the pilot nozzle 50 and the main nozzle 60 is cut. The pilot nozzle 50 and the main nozzle 60 are arranged such that the longitudinal direction, that is, the direction of the central axis, is along the air flow direction AF of the combustor inner cylinder 19.

[0020] The fuel supply paths 41-P and 42-P are connected to the pilot nozzle 50. The fuel supply paths 41-M and 42-M are connected to the main nozzle 60. Inside the pilot nozzle 50, two pipes connected to each of the fuel supply paths 41-P and 42-P are provided. These pipes and the fuel supply paths 41-P and 42-P connected to each of these pipes are physically separate entities. However, here, for the sake of convenience of explanation, the pipe inside the pilot nozzle 50 connected to the fuel supply path 41-P is described as being included in the fuel supply path 41-P, and the pipe inside the pilot nozzle 50 connected to the fuel supply path 42-P is described as being included in the fuel supply path 42-P. For each of the pipes inside the main nozzle 60, similar to the case of the pilot nozzle 50, it is described as being included in the fuel supply paths 41-M and 42-M connected to each.

[0021] The pilot nozzle 50 has fuel gas injection holes 51-1 and 51-2, and fuel oil injection hole 52. The fuel supply passage 41-P leads to injection holes 51-1 and 51-2, and the fuel supply passage 42-P leads to injection hole 52. Note that Figure 2 is a schematic diagram, and in reality, there are not only two injection holes for injecting fuel gas, but multiple injection holes, namely injection holes 51-1 and 51-2. However, here we will explain assuming that there are at least two injection holes 51-1 and 51-2.

[0022] The main nozzle 60 has injection holes 61-1 and 61-2 for fuel gas and injection holes 62-1 and 62-2 for fuel oil. The fuel supply passage 41-M leads to injection holes 61-1 and 61-2. The fuel supply passage 42-M leads to injection holes 62-1 and 62-2. Note that Figure 2 is a schematic diagram, and in reality, there are not only two injection holes for injecting fuel gas, but multiple injection holes, and not only two injection holes, 61-1 and 61-2, but also multiple injection holes for injecting fuel oil, not just two injection holes, 62-1 and 62-2. However, here we will explain assuming that there are at least two injection holes 61-1 and 61-2 for fuel gas and at least two injection holes 62-1 and 62-2 for fuel oil.

[0023] Let's assume that fuel gas is supplied from fuel supply passages 41-P and 41-M. In this case, when fuel gas is injected from the injection holes 51-1 and 51-2 of the pilot nozzle 50 into the air flowing inside the combustor inner cylinder 19, the 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 19, the injected fuel gas burns using the flame obtained from the combustion of the fuel gas injected from injection holes 51-1 and 51-2 as a pilot ignition.

[0024] Let's assume that fuel oil is supplied from fuel supply passages 42-P and 42-M. In this case, when fuel oil is injected from the injection hole 52 of the pilot nozzle 50 into the air flowing inside the combustor inner cylinder 19, the injected fuel oil burns. Furthermore, when fuel oil is injected from the injection holes 62-1 and 62-2 of the main nozzle 60 into the air flowing inside the combustor inner cylinder 19, the injected fuel oil burns using the flame obtained from the combustion of the fuel oil injected from injection hole 52 as a pilot ignition.

[0025] As shown in Figure 1, the combustion gas generated in the combustor cylinder 19 by the combustion of fuel gas or fuel oil flows out through an opening provided at the bottom of the combustor cylinder 19, 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.

[0026] 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 19, 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. However, the positions of the injection holes 61-1, 61-2, 62-1, and 62-2 of each of the multiple main nozzles 60 are all located upstream in the airflow direction AF from the positions of the injection holes 51-1, 51-2, and 52 of the pilot nozzle 50.

[0027] When the combustor inner cylinder 19 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, 32-M and fuel supply passages 41-M, 42-M corresponds to the number of groups. Each of the fuel supply passages 41-M, 42-M assigned to one group branches out and connects to each of the multiple main nozzles 60 included in that group, and fuel gas or fuel oil with a flow rate regulated for each group is supplied.

[0028] The IGV (Inlet Guide Vane) 17 is located inside the air compressor 11 and is installed near the air intake port of the air compressor 11. The IGV 17 is electrically connected to the control device 2, and when it receives an IGV opening command signal from the control device 2, it opens and closes its guide vanes to adjust the amount of air drawn in by the air compressor 11 so that the IGV opening is the value indicated in the received IGV opening command signal.

[0029] The power meter 5 measures the amount of power generated by the generator 15 at regular intervals and transmits the measured amount of power to the control device 2. The temperature sensor 6 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.

[0030] As explained with reference to Figure 2, the injection holes 61-1, 61-2, 62-1, and 62-2 of the main nozzle 60 are all located upstream in the airflow direction AF compared to the injection holes 51-1, 51-2, and 52 of the pilot nozzle 50. In other words, among the fuel gas injection holes 51-1, 51-2, 61-1, and 61-2 of the pilot nozzle 50, the fuel gas injection holes 51-1 and 51-2 of the pilot nozzle 50 are located at the downstream end of the airflow direction AF. Therefore, if the fuel gas supply to the pilot nozzle 50 and the main nozzle 60 is stopped and fuel oil is supplied instead, the high-temperature combustion gas generated by the combustion of the fuel oil may flow back through the fuel gas injection holes 51-1 and 51-2 of the pilot nozzle 50, potentially burning out the pilot nozzle 50.

[0031] To prevent burnout of the pilot nozzle 50, a flow control valve 30 and a sweep air supply passage 40 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-P at the other end. The sweep air supply passage 40 is connected to the combustor chamber 18, and extracts air from the combustor chamber 18, guiding the extracted air as sweep air towards the flow control valve 30. 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 in the received valve opening command signal to adjust the flow rate of the sweep air. As a result, when the flow control valve 30 is opened while the flow control valve 31-P is closed, swept air flows into the fuel supply passage 41-P, and swept air is injected from the fuel gas injection holes 51-1 and 51-2 of the pilot nozzle 50, thereby preventing backflow of high-temperature combustion gas.

[0032] 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, consisting of a combination of hardware such as the computer and software such as programs executed by the computer, includes a fuel supply control unit 21, an IGV control unit 22, and a storage unit 23, as shown in Figure 1. The fuel supply control unit 21 performs various controls related to fuel supply by transmitting valve opening command signals to the flow control valves 30, 31-P, 31-M, 32-P, and 32-M. Examples of the various controls performed by the fuel supply control unit 21 include the controls shown below.

[0033] The fuel supply control unit 21 controls the fuel supplied to the combustor 12, switching between fuel gas and fuel oil, while the gas turbine 10 continues to operate. Generally, the main fuel supplied to the combustor 12 is fuel gas, and fuel oil is positioned as a backup fuel used in case of any problems with the supply or combustion of fuel gas. Therefore, control is performed to switch from fuel gas to fuel oil, and then, once the problem with the fuel gas is resolved, control is performed to switch from fuel oil to fuel gas.

[0034] The fuel supply control unit 21 maintains a constant calorific value of the fuel supplied to the combustor 12 while proportionally distributing the calories between the fuel gas and fuel oil, and performing a stepwise switch when switching from fuel gas to fuel oil or from fuel oil to fuel gas. For example, when switching from fuel gas to fuel oil, the fuel supply control unit 21 gradually changes the ratio of calories of fuel gas to fuel oil from 100:0 to 70:30, 50:50, 30:70, and 0:100. In the intermediate states of the switch, such as 70:30, 50:50, and 30:70, the fuel gas and fuel oil are co-fired in the combustor 12. Theoretically, the combustion temperature should not increase because the calorific value of the fuel is maintained constant even during co-fired combustion. However, in reality, differences in the combustion state of fuel gas and fuel oil can cause the combustion state to become unstable, leading to an increase in combustion temperature and the occurrence of combustion oscillations.

[0035] The fuel supply control unit 21 controls the load on the gas turbine 10 to a predetermined load range by referring to the amount of power generated by the generator 15 measured by the power meter 5 when switching from fuel gas to fuel oil and when switching from fuel oil to fuel gas. In this case, the load on the gas turbine 10 refers to the output of the gas turbine 10, that is, the amount of power generated by the generator 15. The reason for reducing the load on the gas turbine 10 to a predetermined load range is to lower the combustion temperature in the combustor 12 and suppress combustion oscillations that occur when fuel gas and fuel oil are mixed and burned together as much as possible.

[0036] When switching from fuel gas to fuel oil, the fuel supply control unit 21 completely closes the flow control valve 31-P to stop the supply of fuel gas to the fuel supply passage 41-P, and opens the flow control valve 30 to supply sweep air to the fuel supply passage 41-P. When switching from fuel oil to fuel gas, the fuel supply control unit 21 completely closes the flow control valve 30 to stop the supply of sweep air to the fuel supply passage 41-P, and opens the flow control valve 31-P to supply fuel gas to the fuel supply passage 41-P.

[0037] The IGV control unit 22 adjusts the opening of the IGV 17 by transmitting an IGV opening command signal to the IGV 17 indicating the IGV opening degree according to the operating state of the gas turbine 10. When a fuel switch is performed, the IGV control unit 22 identifies an IGV opening degree that will lower the sweep air temperature to a predetermined autoignition prevention temperature of the fuel gas. Here, the following temperature is predetermined as the autoignition prevention temperature of the fuel gas. 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, when the fuel gas is natural gas, a temperature of about 420°C is predetermined as the autoignition prevention temperature.

[0038] Incidentally, during the process of switching fuel from fuel gas to fuel oil, and during the process of switching fuel from fuel oil to fuel gas, as described above, there are times when fuel gas and fuel oil are mixed-combusted in the combustor 12, and combustion vibrations may occur during this mixing. As described above, these combustion vibrations can be suppressed to some extent by reducing the load of the gas turbine 10 to a predetermined load range, but they cannot be suppressed sufficiently. In this case, it is known that combustion vibrations can be further suppressed by increasing the opening of the IGV 17, thereby increasing the amount of air drawn in by the air compressor 11 and lowering the combustion temperature in the combustor 12.

[0039] On the other hand, as the amount of air drawn in by the air compressor 11 increases, the air pressure in the air compressor 11 increases, and as this pressure increases, the temperature of the air rises, so the temperature of the air flowing into the combustor chamber 18, i.e., the temperature of the sweep air, also rises. Therefore, it is necessary to take into account the amount of air drawn in by the air compressor 11, so that the temperature of the sweep air does not exceed the autoignition prevention temperature of the fuel gas, and so that combustion oscillations during co-firing can be suppressed as much as possible.

[0040] In addition, if the temperature of the air intake by the air compressor 11, i.e., the ambient temperature, is high, the temperature of the air flowing into the combustor chamber 18, i.e., the sweep air temperature, will also rise accordingly. Therefore, it is necessary to take the ambient temperature into consideration so that the sweep air temperature does not exceed the autoignition prevention temperature of the fuel gas, and so that combustion oscillations during co-firing can be suppressed as much as possible.

[0041] Since the amount of air drawn in by the air compressor 11 is determined by the opening of the IGV 17, the two considerations mentioned above can be expressed in terms of the relationship between the IGV opening and the ambient temperature. Furthermore, the combustion temperature at which combustion oscillations can be suppressed during co-firing is a temperature that can be predetermined, and this combustion temperature will be referred to below as the combustion oscillation suppression temperature.

[0042] The graph shown in Figure 3 is an example of the relationship between the IGV opening and ambient temperature when the load on the gas turbine 10 is reduced to the predetermined load range described above. In the graph shown in Figure 3, the horizontal axis represents the magnitude of ambient temperature, and the temperature increases in the direction of the arrow on the horizontal axis. The vertical axis represents the IGV opening, and the IGV opening increases in the direction of the arrow on the vertical axis.

[0043] The line indicated by reference numeral 71 is a characteristic curve (hereinafter referred to as characteristic curve 71) that shows the relationship between ambient temperature and IGV opening degree when the load of the gas turbine 10 is reduced to a predetermined load range and the gas turbine 10 is operating at a constant load.

[0044] Hereinafter, the operating state in which the gas turbine 2 operates at a constant load while the load of the gas turbine 10 has been reduced to a predetermined load range in order to switch fuels will be referred to as the second normal operating state. In contrast, the operating state in which the gas turbine 10 operates at a constant load that can obtain the required amount of power generation requested by, for example, a power transmission company will be referred to as the first normal operating state.

[0045] As shown by characteristic curve 71, when the gas turbine 10 is operating in the second normal operating state, the IGV opening remains almost constant regardless of the ambient temperature. Furthermore, the combustion temperature when the gas turbine 10 is operating in the second normal operating state is higher than the combustion oscillation suppression temperature.

[0046] The line indicated by symbol 72 is a characteristic curve (hereinafter referred to as characteristic curve 72) that shows the relationship between ambient temperature and IGV opening when the sweep air temperature is set to the autoignition prevention temperature. As shown in characteristic curve 72, when maintaining the sweep air temperature at the autoignition prevention temperature, it is necessary to decrease the IGV opening as the ambient temperature increases. This is because as the ambient temperature increases, the temperature of the air in the combustor chamber 18 increases accordingly, so it is necessary to reduce the amount of air drawn in by the air compressor 11 to lower the sweep air temperature.

[0047] The line indicated by symbol 73 is a characteristic curve (hereinafter referred to as characteristic curve 73) that shows the relationship between ambient temperature and IGV opening when the combustion temperature during co-firing is set to the combustion oscillation suppression temperature. As shown in characteristic curve 73, when maintaining the combustion temperature during co-firing at the combustion oscillation suppression temperature, it is necessary to increase the IGV opening as the ambient temperature increases. This is because, as the ambient temperature increases, the density of air decreases, so it is necessary to increase the IGV opening compared to when the ambient temperature is low to increase the amount of air supplied to the combustor 12 and maintain the combustion temperature during co-firing at the combustion oscillation suppression temperature.

[0048] As shown in Figure 3, characteristic curves 72 and 73 intersect at the position of temperature TC, where the ambient temperature is. In the range where the ambient temperature is below temperature TC, the IGV opening on characteristic curve 73 is smaller than the IGV opening on characteristic curve 72. Therefore, by setting the IGV opening according to characteristic curve 73, the temperature of the sweep air does not exceed the autoignition prevention temperature of the fuel gas, and combustion oscillations during co-firing can be suppressed.

[0049] In contrast, in the range where the ambient temperature exceeds temperature TC, the IGV opening on characteristic curve 72 becomes smaller than the IGV opening on characteristic curve 73. Therefore, if the IGV opening is determined according to characteristic curve 73, combustion oscillations during co-firing can be suppressed, but the temperature of the sweep air will exceed the autoignition prevention temperature of the fuel gas. Consequently, in the range where the ambient temperature exceeds temperature TC, it is necessary to determine the IGV opening according to characteristic curve 72 in order to prevent autoignition of the fuel gas.

[0050] Therefore, the characteristics of the atmospheric temperature interval in which the IGV opening is smaller are selected from characteristic curves 72 and 73, and the IGV opening is determined according to the characteristic curve indicated by the dotted line of reference numeral 74 (hereinafter referred to as characteristic curve 74), which is obtained by combining the characteristics of the selected atmospheric temperature interval and the characteristics at temperature TC. By adjusting the opening of IGV 17 to achieve the IGV opening determined in this way, it becomes possible to prevent the temperature of the sweep air from exceeding the autoignition prevention temperature of the fuel gas, and to suppress combustion oscillations during co-firing as much as possible.

[0051] The memory unit 23 stores a function representing the characteristic curve 71 and a function representing the characteristic curve 74 so that the IGV control unit 22 can identify an appropriate IGV opening when fuel switching occurs. The reason for storing the function representing the characteristic curve 71 in the memory unit 23 is as follows: The example shown in Figure 3 is an example where a predetermined load range is used, and in this example, the characteristic curve 71 shows that the IGV opening is almost constant regardless of the magnitude of the ambient temperature. In this case, for example, the IGV opening corresponding to the average ambient temperature can be identified from the characteristic curve 71, and this identified IGV opening can be used as the opening of the IGV 17 in the second normal operating state. On the other hand, when a load range different from the example shown in Figure 3 is used as the predetermined load range, the characteristic curve 71 may show a tendency for the IGV opening to fluctuate according to the ambient temperature. In this case, it is necessary to identify an appropriate IGV opening according to the ambient temperature in the second normal operating state, and the memory unit 23 is configured to store a function representing the characteristic curve 71 so that this appropriate IGV opening can be identified.

[0052] (Processing by the control device) Referring to Figures 4 and 5, the process by which the control device 2 switches fuels will be explained.

[0053] (Conversion process from fuel gas to fuel oil) Figure 4 is a flowchart showing the process flow when switching fuel from fuel gas to fuel oil. Before the process shown in Figure 4 is performed, the flow control valves 30, 32-P, and 32-M are in a fully closed state. The opening of the flow control valves 31-P and 31-M, and the opening of the IGV 17 are set to the opening that brings the operating state of the gas turbine 10 to the first normal operating state.

[0054] The operator of the gas turbine power plant 1 supplies command signals to the fuel supply control unit 21 and the IGV control unit 22 to switch from fuel gas to fuel oil. Upon receiving the command signal to switch from fuel gas to fuel oil, the IGV control unit 22 immediately receives the ambient temperature from the temperature sensor 6. After receiving the ambient temperature, the IGV control unit 22 reads a function representing the characteristic curve 71 from the memory unit 23 and applies the acquired ambient temperature to the read function representing the characteristic curve 71 to determine the IGV opening. The IGV control unit 22 transmits an IGV opening command signal indicating the determined IGV opening to the IGV 17. Upon receiving the IGV opening command signal transmitted by the IGV control unit 22, the IGV 17 adjusts its opening to match the IGV opening indicated by the received IGV opening command signal. As a result, the opening of the IGV 17 becomes the opening that sets the operating state of the gas turbine 10 to the second normal operating state.

[0055] When the fuel supply control unit 21 receives a command signal to switch from fuel gas to fuel oil, it performs a process to reduce the load on the gas turbine 10 to a predetermined load range, that is, a process to transition the operating state of the gas turbine 10 from a first normal operating state to a second normal operating state. Based on the predetermined load range and the amount of power generated sequentially measured and output by the power meter 5, the fuel supply control unit 21 calculates the valve opening of each of the flow control valves 31-P and 31-M. The fuel supply control unit 21 transmits each of the valve opening command signals indicating the calculated valve opening to the respective flow control valves 31-P and 31-M. Each of the flow control valves 31-P 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.

[0056] The fuel supply control unit 21 repeatedly adjusts the opening of the flow control valves 31-P and 31-M until the load of the gas turbine 10, indicated by the amount of power generated sequentially measured and output by the power meter 5, reaches a predetermined load range. When the load of the gas turbine 10 decreases to a predetermined load range and the operating state of the gas turbine 10 enters the second normal operating state, the fuel supply control unit 21 outputs a temperature control start signal to the IGV control unit 22 (Sa1).

[0057] When the IGV control unit 22 receives a temperature control start signal from the fuel supply control unit 21, it immediately acquires the ambient temperature received from the temperature sensor 6. After acquiring the ambient temperature, the IGV control unit 22 reads a function representing the characteristic curve 74 from the memory unit 23, and applies the acquired ambient temperature to the read function representing the characteristic curve 74 to determine the IGV opening (Sa2).

[0058] The IGV control unit 22 transmits an IGV opening command signal to the IGV 17 indicating the specified IGV opening. When the IGV 17 receives the IGV opening command signal transmitted by the IGV control unit 22, it adjusts its opening to the IGV opening indicated by the received IGV opening command signal. After transmitting the IGV opening command signal to the IGV 17, or after such transmission, the IGV control unit 22 waits for the time required for the IGV 17 to adjust its opening before outputting a temperature control completion signal to the fuel supply control unit 21 (Sa3).

[0059] When the fuel supply control unit 21 receives a command signal to switch from fuel gas to fuel oil, and receives a temperature control completion signal from the IGV control unit 22, it maintains the calorific value of the fuel supplied to the combustor 12 at that time, i.e., the calorific value in the second normal operating state, and proportionally distributes the calories between the fuel gas and fuel oil to perform a stepwise switch from fuel gas to fuel oil. The fuel supply control unit 21 calculates the valve openings corresponding to each of the flow control valves 31-P, 31-M, 32-P, and 32-M from the respective calorific values ​​of the fuel gas and fuel oil corresponding to each stage. The fuel supply control unit 21 generates four valve opening command signals indicating each of the calculated valve openings and transmits each of the four generated valve opening command signals to the corresponding flow control valves 31-P, 31-M, 32-P, and 32-M. The time between one stage and the next stage is predetermined, and the fuel supply control unit 21 waits for that time before transmitting the valve opening command signal corresponding to the next stage (Sa4).

[0060] When the flow control valves 31-P and 31-M are fully closed, the fuel supply control unit 21 transmits a valve opening command signal to the flow control valve 30, indicating a predetermined valve opening, in order to open the flow control valve 30. The predetermined valve opening for the flow control valve 30 may be a valve opening indicating full opening, or it may be a valve opening corresponding to a predetermined flow rate of sweep air supplied to the fuel supply passage 41-P. As a result, the sweep air extracted from the combustor chamber 18 is guided to the flow control valve 30 by the sweep air supply passage 40, passes through the flow control valve 30, and is supplied to the fuel supply passage 41-P. The sweep air supplied to the fuel supply passage 41-P is injected from the injection holes 51-1 and 51-2 of the pilot nozzle 50 (Sa5).

[0061] The fuel supply control unit 21 outputs a command signal to the IGV control unit 22 to set the operating state of the gas turbine 10 to the second normal operating state. When the IGV control unit 22 receives this command signal from the fuel supply control unit 21, it performs the same processing as when it receives a command signal to switch from fuel gas to fuel oil, as explained in the processing of Sa1. As a result, the opening degree of the IGV 17 becomes the degree to which the operating state of the gas turbine 10 is set to the second normal operating state (Sa6). Note that the calorific value of the combustion oil supplied to the combustor 12 is already at the calorific value of the second normal operating state. Therefore, at the timing of processing Sa6, the fuel supply control unit 21 does not need to perform processing to change the flow rate of fuel oil in order to set the operating state to the second normal operating state.

[0062] The operator of the gas turbine power plant 1 sends a command signal to the fuel supply control unit 21 and the IGV control unit 22 to transition from the second normal operating state to the first normal operating state. Upon receiving the command signal to transition from the second normal operating state to the first normal operating state, the fuel supply control unit 21 repeatedly calculates the valve openings of the flow control valves 32-P and 32-M until the generator 15 is generating the required amount of power in the first normal operating state. Each time the valve opening is calculated, the fuel supply control unit 21 transmits a valve opening command signal indicating the calculated valve opening to the corresponding flow control valves 32-P and 32-M.

[0063] When the IGV control unit 22 receives a command signal to transition from the second normal operating state to the first normal operating state, it repeatedly calculates the IGV opening until the generator 15 is generating the required amount of power in the first normal operating state. Each time the IGV opening is calculated, the IGV control unit 22 sends an IGV opening command signal indicating the calculated IGV opening to the IGV 17. As a result, the operating state of the gas turbine 10 transitions from the second normal operating state to the first normal operating state (Sa7), and the process ends. As a result, the gas turbine 10 completely switches from a fuel gas-fired state to a fuel oil-fired state.

[0064] (Conversion process from fuel oil to fuel gas) Figure 5 is a flowchart showing the process flow when switching fuel from fuel oil to fuel gas. Before the process shown in Figure 5 is performed, the flow control valves 31-P and 31-M are in a fully closed state. The opening of flow control valve 30 is set to a predetermined valve opening as explained in the process of Sa5, and the openings of flow control valves 32-P and 32-M, and the opening of IGV 17 are set to the openings that bring the operating state of the gas turbine 10 to the first normal operating state.

[0065] The operator of the gas turbine power plant 1 sends a command signal to the fuel supply control unit 21 and the IGV control unit 22 to switch from fuel oil to fuel gas. When the IGV control unit 22 receives the command signal to switch from fuel oil to fuel gas, it performs the same processing as when it receives a command signal to switch from fuel gas to fuel oil, as explained in the processing of Sa1. As a result, the opening degree of the IGV 17 becomes the degree to which the operating state of the gas turbine 10 is set to the second normal operating state.

[0066] When the fuel supply control unit 21 receives a command signal to switch from fuel gas to fuel oil, it performs the same processing as when it receives a command signal to switch from fuel gas to fuel oil, as described in processing Sa1, but with the flow control valve 31-P replaced with flow control valve 32-P and flow control valve 31-M replaced with flow control valve 32-M (Sb1). As a result, the fuel supply control unit 21 supplies a temperature control start signal to the IGV control unit 22.

[0067] The IGV control unit 22 performs the same processing as Sa2 for Sb2, and performs the same processing as Sa3 for Sb3.

[0068] When the fuel supply control unit 21 receives a command signal to switch from fuel gas to fuel oil, and receives a temperature control completion signal from the IGV control unit 22, it sends a valve opening command signal indicating a fully closed valve opening to the flow control valve 30, thereby closing the flow control valve 30 completely. This stops the supply of sweep air to the fuel supply passage 41-P (Sb4).

[0069] After the fuel supply control unit 21 transmits a valve opening command signal to the flow control valve 30, in the process of Sa4, it performs a process to swap fuel gas and fuel oil, switching the fuel supplied to the combustor 12 from fuel oil to fuel gas (Sb5).

[0070] The fuel supply control unit 21 and the IGV control unit 22 perform the same processing as for Sa6 for Sb6. Note that the calorific value of the combustion gas supplied to the combustor 12 is already at the calorific value of the second normal operating state. Therefore, at the timing of processing Sb6, the fuel supply control unit 21 does not need to perform any processing to change the flow rate of the fuel gas in order to reach the second normal operating state.

[0071] The process for Sb7 is the same as that for Sa7, but with the flow control valve 32-P replaced by the flow control valve 31-P and the flow control valve 32-M replaced by the flow control valve 31-M. As a result, the gas turbine 10 completely switches from a fuel oil-fired state to a fuel gas-fired state.

[0072] (Effects of the embodiment) In the above embodiment, the IGV control unit 22 determines the IGV opening degree based on a function representing a characteristic line 74, which is determined from a characteristic line 72 that sets the temperature of the sweep air to the autoignition prevention temperature of the fuel gas and a characteristic line 73 that sets the combustion temperature during co-firing to the combustion oscillation suppression temperature, as well as the ambient temperature measured by the temperature sensor 6, as a pre-processing step for the fuel supply control unit 21 to switch the fuel supplied to the combustor 12, and sets the opening degree of the IGV 17 to the determined IGV opening degree.

[0073] In the process of switching from fuel gas to fuel oil, before the Sa5 process of supplying sweep air to the fuel supply passage 41-P is performed, the opening degree of the IGV 17 has already been set by the Sa3 process to the IGV opening degree determined by the ambient temperature measured by the temperature sensor 6 and the function representing the characteristic curve 74. Therefore, the temperature of the sweep air is below the autoignition prevention temperature when the ambient temperature is below temperature TC, and at the autoignition prevention temperature when the ambient temperature is above temperature TC. Consequently, even if fuel gas remains in the fuel supply passage 41-P and the sweep air supplied to the fuel supply passage 41-P by the Sa5 process comes into contact with this remaining fuel gas, the fuel gas will not autoignite.

[0074] In the process of switching from fuel oil to fuel gas, before the Sb5 process, which supplies fuel gas to the fuel supply passage 41-P, is performed, the Sb3 process has already set the IGV opening to the IGV opening determined by the ambient temperature measured by the temperature sensor 6 and the function representing the characteristic curve 74. Therefore, the temperature of the sweep air is below the autoignition prevention temperature when the ambient temperature is below temperature TC, and at the autoignition prevention temperature when the ambient temperature is above temperature TC. Consequently, even if sweep air remains in the fuel supply passage 41-P and the fuel gas supplied to the fuel supply passage 41-P by the Sb5 process comes into contact with this remaining sweep air, the fuel gas will not autoignite.

[0075] Therefore, in both the switching from fuel gas to fuel oil and the switching from fuel oil to fuel gas, the temperature of the swept air can be lowered to a temperature at which the fuel gas does not self-ignite, without the need for a cooling means.

[0076] Furthermore, in the above embodiment, when the ambient temperature is below temperature TC, the IGV 17 opening is set to an IGV opening that makes the combustion temperature during co-firing a combustion oscillation suppression temperature, thus making it possible to suppress combustion oscillations during co-firing. When the ambient temperature is above temperature TC, the IGV 17 opening is set to an IGV opening that makes the combustion temperature during co-firing a combustion oscillation suppression temperature, so combustion oscillations during co-firing are not completely suppressed, but it is possible to suppress combustion oscillations to the maximum extent possible when the combustion gas does not self-ignite.

[0077] Furthermore, in the processing of Sa3 and Sb3, when the ambient temperature is below temperature TC, the IGV control unit 22 may adopt an IGV opening that is not directly determined by applying the ambient temperature to the function representing the characteristic curve 74, but rather as follows: That is, it may adopt any IGV opening that is greater than or equal to the determined IGV opening, and less than or equal to the IGV opening determined based on the ambient temperature and the characteristic curve 72. When this adopted IGV opening is applied to IGV 17, the temperature of the sweep air can be set to a temperature below the autoignition prevention temperature, and the combustion temperature during co-firing can be set to a temperature below the combustion oscillation suppression temperature. As a result, the combustion gas will not autoignite and combustion oscillations will be suppressed, but there is a risk that the combustion temperature will drop excessively, and the temperature of the exhaust gas discharged from the turbine 13 may also drop excessively along with the decrease in combustion temperature. If the gas turbine power plant 1 is, for example, a combined cycle that generates electricity using the heat of the exhaust gas downstream of the gas turbine 10, an excessive drop in the temperature of the exhaust gas may affect the power generation downstream. If there is a risk of such an effect, the IGV control unit 22 preferably uses the IGV opening degree determined based on the ambient temperature and the function representing the characteristic curve 74 as is.

[0078] (Modified examples of the embodiment) The gas turbine 10 shown in Figure 1 is equipped with a dual-fuel combustor 12, but a gas turbine equipped with a fuel gas-fired combustor supplied only with fuel gas is known, and is equipped with a premixed pilot nozzle 80 as shown in Figure 6. In order to explain the case in which sweep air is used in this pilot nozzle 80, we will assume a configuration in which the pilot nozzle 80 is provided in place of the pilot nozzle 50 in the combustor inner cylinder 19 of the gas turbine 10 shown in Figure 1. Furthermore, since the gas turbine power plant 1 equipped with this configuration of gas turbine 10 is fuel gas-fired, it will not be equipped with a fuel oil supply device 4, flow control valves 32-P, 32-M, and fuel supply passages 42-P, 42-M. In addition, the main nozzle 60 will be assumed to be a nozzle that injects only fuel gas and does not have injection holes 62-1, 62-2 for injecting fuel oil.

[0079] The premixed pilot nozzle 80 has a longitudinal shape, and Figure 6 schematically shows a cross-section of the pilot nozzle 80 when it is cut by a plane parallel to the longitudinal direction and containing the central axis. The pilot nozzle 80 is positioned so that its longitudinal direction, i.e., the direction of the central axis, is aligned with the direction AF of airflow in the combustor inner cylinder 19.

[0080] The pilot nozzle 80 is provided with two fuel supply passages: a diffusion fuel supply passage 41-P and a premixing fuel supply passage 45-P. Inside the pilot nozzle 80 are two pipes connected to the fuel supply passages 41-P and 45-P, respectively. Although these pipes and the fuel supply passages 41-P and 45-P connected to them are physically separate, as with the pilot nozzle 50, the pipe inside the pilot nozzle 80 connected to the fuel supply passage 41-P will be described as being included in the fuel supply passage 41-P, and the pipe inside the pilot nozzle 80 connected to the fuel supply passage 45-P will be described as being included in the fuel supply passage 45-P.

[0081] The pilot nozzle 80 includes injection holes 81-1 and 81-2 for injecting diffusion fuel gas, and injection holes 82-1 and 82-2 for injecting premixing fuel gas. The fuel supply passage 41-P leads to injection holes 81-1 and 81-2. The fuel supply passage 45-P leads to injection holes 82-1 and 82-2. Note that Figure 6 is a schematic diagram, and in reality, there are not limited to just two injection holes 81-1 and 81-2 for diffusion, but multiple injection holes. Similarly, there are not limited to just two injection holes 82-1 and 82-2 for premixing, but multiple injection holes. However, here we will explain assuming that there are at least two injection holes 81-1 and 81-2 for diffusion, and at least two injection holes 82-1 and 82-2 for premixing.

[0082] A flow control valve 35-P is also provided, which is connected to the fuel gas supply device 3 via piping at one end and to the fuel supply line 45-P at the other end. Like the flow control valve 31-P, the flow control valve 35-P 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 in the received valve opening command signal to adjust the flow rate of the fuel gas.

[0083] When the gas turbine 10 is operating in a low-load operation state, which generates power corresponding to a low load below a predetermined high / low switching load, the pilot nozzle 80 injects fuel gas from the diffusion injection holes 81-1 and 81-2, but does not inject fuel gas from the premixing injection holes 82-1 and 82-2. Conversely, when the gas turbine 10 is operating in a high-load operation state, which generates power corresponding to a high load above a predetermined high / low switching load, the pilot nozzle 80 injects fuel gas from the premixing injection holes 82-1 and 82-2, but does not inject fuel gas from the diffusion injection holes 81-1 and 81-2.

[0084] The diffusion injection holes 81-1 and 81-2 are located at the downstream end of the airflow direction AF among all the nozzles present in the combustor inner cylinder 19, including the pilot nozzle 80 and the main nozzle 60. Therefore, when the gas turbine 10 is operating under high load conditions, there is a risk that high-temperature combustion gas may backflow through the diffusion injection holes 81-1 and 81-2, which do not inject fuel gas, and burn out the pilot nozzle 80. To prevent this burnout of the pilot nozzle 80, a flow control valve 30 and a sweep air supply passage 40 are provided, similar to the embodiment described above. By providing these, when the flow control valve 31-P is opened while it is closed, sweep air flows into the fuel supply passage 41-P, and sweep air is injected from the diffusion injection holes 81-1 and 81-2 of the pilot nozzle 80, thereby preventing the backflow of high-temperature combustion gas.

[0085] In this case as well, similar to the embodiment described above, there are moments when the swept air and fuel gas come into contact in the fuel supply passage 41-P when switching from a high-load operating state to a low-load operating state and when switching from a low-load operating state to a high-load operating state. Therefore, it is necessary to keep the swept air at a temperature below the autoignition prevention temperature.

[0086] However, in the case of fuel gas-fired operation, unlike dual-fuel-fired operation, the fuel gas and fuel oil do not co-fire in the combustor 12, and combustion vibrations do not occur. Therefore, since there is no need to consider combustion vibrations, the IGV opening can be determined based on the characteristic curve 72 when the load of the gas turbine 10 is a predetermined high / low switching load. For this reason, the memory unit 23 stores a function that represents the characteristic curve 72 when the load of the gas turbine 10 is a predetermined high / low switching load. The following describes the processing by the control device 2 when switching from a low-load operating state to a high-load operating state and when switching from a high-load operating state to a low-load operating state.

[0087] (Switching process from low-load operation state to high-load operation state) The operator of the gas turbine power plant 1 supplies a command signal to the fuel supply control unit 21 to switch from a low-load operating state to a high-load operating state. Upon receiving the command signal to switch from a low-load operating state to a high-load operating state, the fuel supply control unit 21 outputs a temperature control start signal to the IGV control unit 22. Upon receiving the temperature control start signal from the fuel supply control unit 21, the IGV control unit 22 performs the same processing as Sa2 and Sa3 in Figure 4, but with characteristic line 74 replaced by characteristic line 72.

[0088] When the fuel supply control unit 21 receives a command signal to switch from a low-load operating state to a high-load operating state, and receives a temperature control completion signal from the IGV control unit 22, it calculates the valve openings of the flow control valves 31-P, 35-P, and 31-M based on the calories of the fuel gas supplied in the high-load operating state. In this case, the valve opening of the flow control valve 31-P becomes a valve opening that represents a fully closed state. The fuel supply control unit 21 transmits each of the valve opening command signals indicating the calculated valve opening to the corresponding flow control valves 31-P, 35-P, and 31-M. As a result, the opening of the flow control valve 31-P becomes fully closed, and the injection of fuel gas from the diffusion injection holes 81-1 and 81-2 stops.

[0089] When the flow control valve 31-P is fully closed, the fuel supply control unit 21 transmits a valve opening command signal to the flow control valve 30, indicating a predetermined valve opening, in order to open the flow control valve 30. As a result, the swept air extracted from the combustor chamber 18 is guided to the flow control valve 30 by the swept air supply passage 40, passes through the flow control valve 30, and is supplied to the fuel supply passage 41-P. The swept air supplied to the fuel supply passage 41-P is injected from the injection holes 81-1 and 81-2 of the pilot nozzle 80.

[0090] In this case, the opening of IGV17 is set to the IGV opening determined by the ambient temperature measured by the temperature sensor 6 and the function representing the characteristic curve 72. Therefore, the temperature of the sweep air is at the autoignition prevention temperature, and fuel gas remains in the fuel supply passage 41-P. Even if the sweep air supplied to the fuel supply passage 41-P comes into contact with this remaining fuel gas, the fuel gas will not autoignite.

[0091] (Switching process from high-load operation state to low-load operation state) The operator of the gas turbine power plant 1 sends a command signal to the fuel supply control unit 21 to switch from a high-load operating state to a low-load operating state. Upon receiving the command signal to switch from a high-load operating state to a low-load operating state, the fuel supply control unit 21 outputs a temperature control start signal to the IGV control unit 22. Upon receiving the temperature control start signal from the fuel supply control unit 21, the IGV control unit 22 performs the same processing as in Sa2 and Sa3, but with characteristic line 74 replaced by characteristic line 72.

[0092] When the fuel supply control unit 21 receives a command signal to switch from a high-load operating state to a low-load operating state, and receives a temperature control completion signal from the IGV control unit 22, it sends a valve opening command signal indicating a fully closed valve opening to the flow control valve 30, thereby fully closing the flow control valve 30. This stops the supply of sweep air to the fuel supply passage 41-P.

[0093] The fuel supply control unit 21 transmits a valve opening command signal to the flow control valve 30, and then calculates the valve openings of the flow control valves 31-P, 35-P, and 31-M based on the calories of the fuel gas supplied during low-load operation. In this case, the valve opening of the flow control valve 35-P is set to a fully closed position. The fuel supply control unit 21 transmits each of the valve opening command signals indicating the calculated valve opening to the corresponding flow control valves 31-P, 35-P, and 31-M. This initiates the supply of fuel gas to the fuel supply line 41-P.

[0094] In this case, the opening of IGV17 is set to the IGV opening determined by the ambient temperature measured by the temperature sensor 6 and the function representing the characteristic curve 72. Therefore, the temperature of the sweep air is at the autoignition prevention temperature, and sweep air remains in the fuel supply passage 41-P. Even if the sweep air supplied to the fuel supply passage 41-P comes into contact with this remaining sweep air, the fuel gas will not autoignite.

[0095] Therefore, in both situations where the operating state of the gas turbine 10 is switched from a low-load operating state to a high-load operating state, and when it is switched from a high-load operating state to a low-load operating state, it becomes possible to lower the temperature of the sweep air to a temperature at which the fuel gas does not self-ignite without the need for cooling means.

[0096] Furthermore, unlike the embodiments described above, in this modified example, combustion vibration does not need to be considered. Therefore, the IGV control unit 22 may set the IGV opening to a value less than or equal to the IGV opening determined by the ambient temperature measured by the temperature sensor 6 and the function representing the characteristic curve 72. In this case, it becomes possible to set the temperature of the sweep air to a temperature below the autoignition prevention temperature.

[0097] In addition, a premixed pilot nozzle may also be used in a dual-fuel gas turbine 10. This pilot nozzle has an injection hole 52 at the tip of the pilot nozzle 80 that injects fuel oil similar to that of the pilot nozzle 50, and a fuel supply passage 42-P to which this injection hole 52 is connected. Even in the case of a dual-fuel gas turbine 10 equipped with such a pilot nozzle, by applying the modified embodiment described above, the temperature of the sweep air can be reduced when switching from a low-load operating state to a high-load operating state, and when switching from a high-load operating state to a low-load operating state, while supplying fuel gas, in order to prevent the fuel gas from self-igniting.

[0098] (Supplementary 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.

[0099] In the above embodiment, multiple predetermined load ranges may be set for switching fuels. In this case, the storage unit 23 stores in advance functions representing characteristic lines 71 and characteristic lines 74 for each of the multiple predetermined load ranges. The command signals for switching from fuel gas to fuel oil and the command signals for switching from fuel oil to fuel gas supplied to the IGV control unit 22 include the predetermined load ranges for which the switching is performed. When the IGV control unit 22 receives either a command signal for switching from fuel gas to fuel oil or a command signal for switching from fuel oil to fuel gas, it reads from the storage unit 23 the functions representing characteristic lines 71 and characteristic lines 74 corresponding to the predetermined load ranges included in the received command signal.

[0100] The load band is, for example, a certain range represented by α±β[MW], where α[MW (Mega Watt)] is the central value and β[MW] is the acceptable range for positive and negative values. In this case, α[MW] becomes the representative value for this load band, and this representative value indicates the load level, which indicates the magnitude of the load. Therefore, for example, when it is possible to set multiple predetermined load bands as described above, each of the multiple predetermined load bands is identified by its corresponding load level. The memory unit 23 is pre-stored a function representing the characteristic curve 71 for each load level and a function representing the characteristic curve 74 for each load level. The command signal for switching from fuel gas to fuel oil and the command signal for switching from fuel oil to fuel gas may also be configured to include the load level.

[0101] In a modified version of the above embodiment, multiple predetermined high / low switching loads may be set when switching the operating state of the gas turbine 10. In this case, each of the multiple predetermined high / low switching loads will represent the load level described above, so the storage unit 23 stores in advance a function representing the characteristic curve 72 for each load level. The command signal for switching from a low-load operating state to a high-load operating state and the command signal for switching from a high-load operating state to a low-load operating state include the load level. When the IGV control unit 22 receives either a command signal for switching from a low-load operating state to a high-load operating state or a command signal for switching from a high-load operating state to a low-load operating state, it reads from the storage unit 23 a function representing the characteristic curve 72 corresponding to the load level included in the received command signal.

[0102] In the above embodiment and modified embodiments, the fuel supply control unit 21 performs a process (hereinafter referred to as the first switching process) in which it completely closes the flow control valve 31-P to stop the supply of fuel gas to the fuel supply passage 41-P, and then opens the flow control valve 30 to supply sweep air to the fuel supply passage 41-P. The fuel supply control unit 21 also performs a process (hereinafter referred to as the second switching process) in which it completely closes the flow control valve 30 to stop the supply of sweep air to the fuel supply passage 41-P, and then opens the flow control valve 31-P to supply fuel gas to the fuel supply passage 41-P. In the above embodiment and modified embodiments, it is explained that the load level at which the first switching process and the second switching process are performed is the same, but the load levels for the first switching process and the second switching process may be different.

[0103] As described above, Figure 3 shows an example of characteristic curves 71, 72, and 73 in a given load range. As explained above, the characteristics of characteristic curve 71 change with different load ranges, and the characteristics of characteristic curves 72 and 73 also change with different load ranges. However, characteristic curve 72 shows a characteristic in all load ranges where the IGV opening decreases as the ambient temperature increases. Characteristic curve 73 intersects characteristic curve 72 at one point in all load ranges. The ambient temperature at this intersection point corresponds to the temperature TC shown in the example in Figure 3. Characteristic curve 73 shows a characteristic in all load ranges where the IGV opening is smaller than that of characteristic curve 72 in the range below the ambient temperature at the intersection point, and larger than that of characteristic curve 72 in the range above the ambient temperature at the intersection point.

[0104] In the process of Sb4 in Figure 5 of the above embodiment, and in the switching process from a high-load operating state to a low-load operating state in a modified example of the embodiment, when the fuel supply control unit 21 receives a temperature control completion signal from the IGV control unit 22, it sends a valve opening command signal indicating a fully closed valve opening to the flow control valve 30 to fully close the flow control valve 30. In this process, in the following cases, the fuel supply control unit 21 may send a valve opening command signal indicating a fully closed valve opening to the flow control valve 30 after a certain period of time has elapsed since receiving the temperature control completion signal. For example, suppose the length of the fuel supply passage 41-P is such that it is expected to take a certain amount of time for the temperature of the sweep air flowing through the fuel supply passage 41-P to reach a temperature below the autoignition prevention temperature after the IGV opening is changed. In this case, the expected time may be measured and determined in advance, and the fuel supply control unit 21 may send a valve opening command signal indicating a fully closed valve opening to the flow control valve 30 after this predetermined time has elapsed since receiving the temperature control completion signal from the IGV control unit 22. This allows the temperature of the swept air remaining in the fuel supply line 41-P to be uniform and below the autoignition prevention temperature.

[0105] In the above embodiments and modified embodiments, the fuel supply passage for supplying sweep air was described as the fuel supply passage 41-P leading to the injection holes 51-1 and 51-2 of the pilot nozzle 50, and the fuel supply passage 41-P leading to the injection holes 81-1 and 81-2 of the pilot nozzle 80. This is because the injection holes 51-1, 51-2, 81-1, and 81-2 are located at the downstream end of the airflow direction AF among all the nozzles present in the combustor inner cylinder 19, and there is a risk of high-temperature combustion gas flowing back. In the current general configuration, the pilot nozzles 50 and 80 have injection holes for injecting fuel gas, which may be susceptible to backflow of high-temperature combustion gas. Therefore, the above explanation has been given using the pilot nozzles 50 and 80 as an example. However, in the future, if there is a risk of backflow of high-temperature combustion gas in the injection holes of nozzles other than the pilot nozzles, sweep air may be supplied to the fuel supply passage leading to the injection hole, and the process for controlling the temperature of the sweep air described in the above embodiment and the modified embodiment may be applied.

[0106] In the above embodiments and modified embodiments, the storage unit 23 stores, for example, a function representing the characteristic curve 74. However, if the characteristic curve 74 is a characteristic that is difficult to represent with a function, a table representing the characteristic curve 74 may be stored using each of a plurality of atmospheric temperatures and the corresponding IGV opening. In this case, instead of using the IGV opening determined by applying the atmospheric temperature measured by the temperature sensor 6 to the function stored in the storage unit 23, the IGV control unit 22 detects an atmospheric temperature in the table that matches or is closest to the atmospheric temperature measured by the temperature sensor 6, and uses the IGV opening of the record corresponding to the detected atmospheric temperature.

[0107] In the above embodiments and modified embodiments, an example is shown in which the gas turbine 10 is equipped with one combustor 12. However, multiple combustors 12 may be arranged in a ring shape around the rotor 14. When multiple combustors 12 are provided, the processes of the above embodiments and modified embodiments are carried out in parallel in each of the multiple combustors 12.

[0108] (Computer configuration) Figure 7 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 100 includes 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 fuel supply control unit 21 and the IGV control unit 22, 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 23 in the main memory 102 or storage 103 according to the program. In accordance with the program, the processor 101 connects the fuel supply control unit 21 to the flow control valves 30, 31-P, 31-M, 32-P, 32-M and the power meter 5 via interface 104, and connects the IGV control unit 22 to the temperature sensor 6 and the IGV 17 via interface 104.

[0109] 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.

[0110] 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.

[0111] <Note> The control device 2 of the gas turbine 10 described in the embodiment of this disclosure can be understood, for example, as follows:

[0112] (1) The control device 2 according to the first embodiment performs a first switching process in which it stops the supply of fuel gas to a predetermined fuel supply passage (e.g., fuel supply passage 41-P) leading to the fuel gas injection holes (e.g., injection holes 51-1, 51-2, 81-1, 81-2) of the nozzles (e.g., pilot nozzles 50, 80) of the combustor 12, and supplies air flowing out of the air compressor 11 as sweep air to the predetermined fuel supply passage, and stops the supply of sweep air to the predetermined fuel supply passage, and supplies the fuel gas to the predetermined fuel The system includes a fuel supply control unit 21 that selects and performs a second switching process to supply fuel to a supply line, and an IGV control unit 22 that performs a process to adjust the opening of the IGV according to the opening of the IGV, which is determined based on a characteristic that indicates the opening of the IGV for each ambient temperature and sets the temperature of the sweep air to a predetermined temperature at which the fuel gas does not self-ignite, and the ambient temperature measured by the temperature sensor 6, as a preprocessing step when the fuel supply control unit selects and performs the first switching process and the second switching process. According to this embodiment and the following embodiments, the temperature of the sweep air can be lowered to a temperature at which the fuel gas does not self-ignite without providing a cooling means.

[0113] (2) The control device 2 according to the second embodiment is the control device of (1), wherein the gas turbine can switch the fuel to be burned in the combustor to either fuel gas or fuel oil while continuing operation, and the characteristics are defined as follows: the first characteristic (for example, the characteristic shown by characteristic line 72) is the characteristic of setting the temperature of the sweep air to the autoignition prevention temperature; the second characteristic (for example, the characteristic shown by characteristic line 73) is the characteristic of setting the combustion temperature when the fuel gas and fuel oil are mixed-combusted in the combustor during the process of switching the fuel supplied to the nozzle to either the fuel gas or the fuel oil to a predetermined combustion oscillation suppression temperature; the characteristics of the ambient temperature range in which the opening degree of the IGV becomes smaller are selected from each of the first characteristic and the second characteristic, and the characteristics obtained by combining the characteristics of the selected ambient temperature range and the characteristics of the point where the first characteristic and the second characteristic intersect are defined (for example, the characteristic shown by characteristic line 74). According to this embodiment, in a dual-fuel gas turbine 10, the temperature of the sweep air can be lowered to a temperature at which the fuel gas does not self-ignite without a cooling means, while suppressing combustion vibrations that occur when the fuel gas and fuel oil co-fire during the fuel switching process.

[0114] (3) The control device 2 according to the third embodiment is the control device of (2), wherein the first characteristic is that the opening of the IGV decreases as the ambient temperature increases, and the second characteristic intersects with the first characteristic at one point, and in the range below the ambient temperature at that point the opening of the IGV becomes smaller than that of the first characteristic, and in the range above the ambient temperature at that point the opening of the IGV becomes larger than that of the first characteristic.

[0115] (4) The control device 2 according to the fourth embodiment is the control device of (2) or (3), wherein the fuel supply control unit performs the first switching process when switching the fuel supplied to the nozzle from the fuel gas to the fuel oil, and performs the second switching process when switching the fuel supplied to the nozzle from the fuel oil to the fuel gas, and the IGV control unit performs a process to adjust the opening of the IGV so that the opening of the IGV is determined by applying the ambient temperature measured and output by the temperature sensor to the characteristics. According to this embodiment, in a dual-fuel-fired gas turbine 10, when the first switching process and the second switching process are selected to be performed, the temperature of the sweep air can be lowered to a temperature at which the fuel gas does not self-ignite without a cooling means, and combustion vibrations that occur when the fuel gas and fuel oil co-fire during the fuel switching process can be suppressed to the maximum extent possible in a state where the combustion gas does not self-ignite.

[0116] (5) The control device 2 according to the fifth embodiment is the control device of (1), wherein the nozzle is a premixed nozzle (for example, a pilot nozzle 80), the fuel supply control unit performs the first switching process when switching the operating state of the gas turbine from a low-load operating state to a high-load operating state, and the second switching process when switching the operating state of the gas turbine from the high-load operating state to the low-load operating state, and the IGV control unit performs a process to adjust the opening degree of the IGV within a range less than or equal to the opening degree of the IGV determined by applying the ambient temperature measured and output by the temperature sensor to the characteristics. According to this embodiment, in the premixed pilot nozzle 80, when switching from a low-load operating state to a high-load operating state, and when switching from a high-load operating state to a low-load operating state, the temperature of the sweep air can be reduced to a temperature at which the fuel gas does not self-ignite without the provision of a cooling means.

[0117] (6) The control device 2 according to the sixth embodiment is any one of the control devices from (1) to (5), wherein the characteristics exist for each load level when the first switching process or the second switching process is performed, and the IGV control unit selects the characteristics corresponding to the load level and performs a process to adjust the opening degree of the IGV according to the opening degree of the IGV determined based on the selected characteristics and the ambient temperature measured by the temperature sensor. According to this embodiment, it becomes possible to arbitrarily select the load of the gas turbine 10 when performing the first switching process and the load of the gas turbine 10 when performing the second switching process within a range in which load levels are defined.

[0118] (7) The control device 2 according to the seventh embodiment is any one of (1) to (6), wherein a plurality of nozzles are provided in the combustor along the direction of airflow within the combustor, and the predetermined fuel supply passage is a fuel supply passage to an injection hole in the plurality of nozzles that injects the fuel gas, the injection hole being located at the downstream end in the direction of airflow within the combustor. According to this embodiment, sweep air can be discharged from the injection hole that injects the fuel gas, which is closest to the high-temperature combustion gas and where the combustion gas is likely to flow back, thereby preventing burnout of the nozzle having the injection hole. [Explanation of Symbols]

[0119] 1…Gas turbine power plant 2…Control device 3…Fuel gas supply device 4…Fuel oil supply device 5…Power meter 6…Temperature sensor 10... Gas turbine 11…Air compressor 12… Combustor 13... Turbine 14…Rota 15…Generator 17…IGV 18... Combustion chamber 19...Inner cylinder of the combustion chamber 21…Fuel supply control unit 22…IGV Control Unit 23…Storage section 30,31-P,31-M,32-P,32-M…Flow control valve 50…Pilot nozzle 51-1,51-2,52…Injection hole 60... Main nozzle 61-1,61-2,62-1,62-2…Injection hole

Claims

1. A fuel supply control unit that selects between a first switching process, which stops the supply of the fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplies air flowing out of the air compressor as sweep air to the predetermined fuel supply path, and a second switching process, which stops the supply of the sweep air to the predetermined fuel supply path and supplies the fuel gas to the predetermined fuel supply path. The fuel supply control unit performs a preprocessing step when selecting to perform the first switching process and the second switching process, which includes an IGV control unit that adjusts the IGV opening degree according to the IGV opening degree determined based on the IGV opening degree, which is A control device for a gas turbine equipped with [a specific feature / feature].

2. The gas turbine is capable of switching the fuel burned in the combustor between fuel gas and fuel oil while continuing operation. The aforementioned characteristics are, The first characteristic is that the temperature of the sweep air is set to the self-ignition prevention temperature, and the second characteristic is that the combustion temperature when the fuel gas and fuel oil are mixed in the combustor during the process of switching the fuel supplied to the nozzle to either the fuel gas or the fuel oil is set to a predetermined combustion oscillation suppression temperature. From each of the first and second characteristics, the characteristic of the ambient temperature range in which the opening of the IGV becomes smaller is selected, and the characteristic is a composite of the selected ambient temperature range and the characteristic at the intersection of the first and second characteristics. The control device for a gas turbine according to claim 1.

3. The first characteristic is that the opening of the IGV decreases as the ambient temperature increases, and the second characteristic intersects with the first characteristic at one point, wherein the opening of the IGV is smaller than that of the first characteristic in the range below the ambient temperature at that point, and the opening of the IGV is larger than that of the first characteristic in the range above the ambient temperature at that point. The control device for a gas turbine according to claim 2.

4. The fuel supply control unit, When switching the fuel supplied to the nozzle from the fuel gas to the fuel oil, the first switching process is performed, and when switching the fuel supplied to the nozzle from the fuel oil to the fuel gas, the second switching process is performed. The IGV control unit is The process involves adjusting the IGV opening to determine the IGV opening by applying the ambient temperature measured and output by the temperature sensor to the aforementioned characteristics. The control device for a gas turbine according to claim 2.

5. The nozzle is a premixing type nozzle, The fuel supply control unit, When switching the operating state of the gas turbine from a low-load operating state to a high-load operating state, the first switching process is performed, and when switching the operating state of the gas turbine from the high-load operating state to the low-load operating state, the second switching process is performed. The IGV control unit is The process involves applying the ambient temperature measured and output by the temperature sensor to the aforementioned characteristics and adjusting the IGV opening within a range less than or equal to the IGV opening determined by this adjustment. The control device for a gas turbine according to claim 1.

6. The aforementioned characteristics exist for each load level when the first switching process or the second switching process is performed. The IGV control unit is The process involves selecting the characteristic corresponding to the load level and adjusting the opening of the IGV according to the opening of the IGV determined based on the selected characteristic and the ambient temperature measured by the temperature sensor. The control device for a gas turbine according to claim 1.

7. Multiple nozzles are provided in the combustor along the direction of airflow within the combustor. The predetermined fuel supply passage is a fuel supply passage that leads to an injection hole in a plurality of nozzles that injects the fuel gas, the injection hole being located at the downstream end in the direction of airflow within the combustor. A control device for a gas turbine according to any one of claims 1 to 6.

8. Selectively perform a first switching process which involves stopping the supply of the fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplying air flowing out of the air compressor as sweep air to the predetermined fuel supply path, and a second switching process which involves stopping the supply of the sweep air to the predetermined fuel supply path and supplying the fuel gas to the predetermined fuel supply path. As a preprocessing step when selecting to perform the first switching process and the second switching process, the opening degree of the IGV is adjusted according to the opening degree of the IGV, which is determined based on a characteristic that indicates the opening degree of the IGV for each ambient temperature, wherein the temperature of the sweep air is set to a predetermined autoignition prevention temperature for the fuel gas, and the ambient temperature measured by a temperature sensor. A method for controlling a gas turbine.

9. Computers, A fuel supply control means that selects between a first switching process, which stops the supply of the fuel gas to a predetermined fuel supply path leading to the fuel gas injection hole of the combustor nozzle and supplies air flowing out of the air compressor as sweep air to the predetermined fuel supply path, and a second switching process, which stops the supply of the sweep air to the predetermined fuel supply path and supplies the fuel gas to the predetermined fuel supply path. The fuel supply control means performs, as a preprocessing step when selecting to perform the first switching process and the second switching process, an IGV control means that adjusts the IGV opening degree according to the IGV opening degree determined based on the IGV opening degree, which is A program designed to function as such.

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