Patent ID: 12253034

DETAILED DESCRIPTION

Hereinafter, a fuel control device for a gas turbine according to the embodiments of the present disclosure will be described with reference to the drawings. The embodiment to be described below indicates one aspect of the present disclosure, does not intend to limit the disclosure, and can optionally be modified within a range of a technical idea of the present disclosure.

Configuration of Fuel Control Device for Gas Turbine According to Embodiment of Present Disclosure

As shown inFIG.1, a gas turbine system10includes a gas turbine1that includes a combustor4for burning fuel to generate a combustion gas, a compressor2for supplying compressed air serving as combustion air to the combustor4, and a turbine6which shares a common rotational shaft5with the compressor2and is configured to be driven by the combustion gas generated by the combustor4. The rotational shaft5is connected to a motor generator7, and the motor generator7is configured to be electrically connectable to a power system8outside the gas turbine1. An inlet of the compressor2is provided with an inlet guide vane (IGV)3A for adjusting an intake air amount. The opening degree of the IGV3A is configured to be adjustable by an actuator3B (inlet guide vane control device). The actuator3B is electrically connected to the controller15.

The combustor4is configured to be supplied with fuel from a fuel supply source11via a fuel supply line12. The fuel supply line12is provided with a fuel control device20for regulating the flow rate (fuel supply amount) of the fuel supplied to the combustor4.FIG.2shows the configuration of the fuel control device20. Within the fuel control device20, the fuel supply line12branches into a main fuel supply line21and a pilot fuel supply line22that, respectively, communicate with a main nozzle and a pilot nozzle of the combustor4(seeFIG.1). The fuel control device20includes: a main fuel control valve23disposed on the main fuel supply line21and configured to adjust a fuel supply amount to the main nozzle; a pilot fuel control valve24disposed on the pilot fuel supply line22and configured to adjust a fuel supply amount to the pilot nozzle; a differential pressure gauge25,26configured to detect a differential pressure between an upstream side and a downstream side of each of the main fuel control valve23and the pilot fuel control valve24; a first valve27and a second valve28which are differential pressure regulating valves disposed in parallel with each other on the main fuel supply line21on the upstream side of the main fuel control valve23; and a differential pressure regulating valve29disposed on the pilot fuel supply line22on the upstream side of the pilot fuel control valve24.

The main fuel control valve23and the pilot fuel control valve24are electrically connected to the controller15, and the controller15is configured to adjust the respective opening degrees of the main fuel control valve23and the pilot fuel control valve24. The first valve27, the second valve28, and the differential pressure gauge25are electrically connected to the controller15, and the controller15is configured to adjust the respective opening degrees of the first valve27and the second valve28by PI control based on a set value of the differential pressure. The differential pressure regulating valve29and the differential pressure gauge26are electrically connected to the controller15, and the controller15is configured to adjust the opening degree of the differential pressure regulating valve29by PI control based on the set value of the differential pressure.

The controller15includes, for example, a Central Processing Unit (CPU), a Random Access Memory (RAM), a Read Only Memory (ROM), a computer-readable storage medium, and the like. Then, a series of processes for realizing various functions is stored in the storage medium or the like in the form of a program, as an example. The CPU reads the program out to the RAM or the like and executes processing/calculation of information, thereby realizing the various functions. A configuration where the program is installed in the ROM or another storage medium in advance, a configuration where the program is provided in a state of being stored in the computer-readable storage medium, a configuration where the program is distributed via a wired or wireless communication means, or the like may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

In the present embodiment, the first valve27and the second valve28differ from each other in relationship between the opening degree and the flow rate of fuel, that is, valve characteristics. As shown inFIG.3, the first valve27and the second valve28can control the fuel pressure between a minimum opening degree Ominand a maximum opening degree Omax, the flow rates of fuel flowing through the respective valves are minimum flow rates F1_minand F2_minwhen the opening degree is the minimum opening degree Omin, and the flow rates of fuel flowing through the respective valves are maximum flow rates F1_maxand F2_maxwhen the opening degree is the maximum opening degree Omax. In the present embodiment, F1_min<F2_maxand F1_max<F2_max.

InFIG.3, the minimum opening degree Ominof the first valve27and the minimum opening degree Ominof the second valve28are the same, and the maximum opening degree Omaxof the first valve27and the maximum opening degree Omaxof the second valve28are the same. However, they may be different from each other. Further. F1_max>F2_minholds inFIG.3, but F1_max≤F2_maxmay hold. Furthermore, inFIG.3, a slope of the valve characteristic of the first valve27is greater than a slope of the valve characteristic of the second valve28. However, the latter may be greater than the former, or the two may be the same. Moreover, although the respective valve characteristics of the first valve27and the second valve28are in a linear relationship, they may also be in a relationship represented by curve.

Operation of Gas Turbine System According to Embodiment of Present Disclosure

Next, an operation of the gas turbine system10according to an embodiment of the present disclosure will be described. As shown inFIG.1, the gas turbine system10can operate by appropriately switching between a normal operation mode which is an operation mode where the motor generator7is driven by the turbine6, and a reverse power operation mode which is an operation mode where the motor generator7provides rotational power to the gas turbine1.

In the normal operation mode, compressed air is supplied from the compressor2to the combustor4, and fuel is supplied from the fuel supply source11to the combustor4via the fuel supply line12, thereby burning the fuel to generate a combustion gas. The combustion gas is supplied to the turbine6to drive, that is, to rotate the turbine6, the rotation of the turbine6is transmitted to the motor generator7via the rotational shaft5, and the motor generator7is driven as a generator. The electric power generated by the motor generator7is supplied to the power system8.

On the other hand, in the reverse power operation mode, electric power is supplied to the motor generator7from the power system8outside the gas turbine1, whereby the motor generator7is driven as the motor. The rotational power generated by the motor generator7is provided to the gas turbine1to assist the operation of the gas turbine1. Therefore, the reverse power operation mode generally consumes less fuel than the normal operation mode.

Operation of Fuel Control Device for Gas Turbine According to Embodiment of Present Disclosure

Next, an operation of the fuel control device20for the gas turbine1will be described with reference toFIGS.1to3and a timing chart ofFIG.4. The timing chart ofFIG.4shows temporal changes of various items when the gas turbine system10transitions from the normal operation mode to the reverse power operation mode. Until time t0, the gas turbine system10operates at a prescribed load L0in the normal operation mode. At the time t0, an operator of the gas turbine system10starts a preparation to start switching to the reverse power operation mode at time t2described later.

Based on the operation of the operator at the time t0, the controller15changes over time a fuel flow rate set value which is a parameter used to control the fuel supply amount to the combustor4, thereby decreasing the fuel flow rate set value from a fuel supply amount F0in a case where the gas turbine system10operates at the load L0to a fuel supply amount Fminin a case where the gas turbine system10operates at a minimum load Lmindescribed later. Further, the controller15controls the main fuel control valve23and the pilot fuel control valve24based on the fuel flow rate set value and a set value of the pilot ratio, thereby decreasing the opening degree of each fuel control valve to respond to the decrease in the fuel flow rate set value. Specifically, the controller15calculates, based on the fuel flow rate set value and the pilot ratio, the respective fuel supply amounts to be supplied to the main nozzle and the pilot nozzle, and transmits signals which indicate the opening degrees corresponding to the respective fuel supply amounts to the main fuel control valve23and the pilot fuel control valve24, respectively. Based on the signals, the opening degrees of the main fuel control valve23and the pilot fuel control valve24are controlled. Further, the opening degree of the second valve28and the opening degree of the differential pressure regulating valve29are adjusted, respectively, such that respective detected values of the differential pressure gauges25and26become the set values. Specifically, the appropriate opening degrees are calculated by performing PI control based on the differences between the set values and the detected values of the respective differential pressure gauges, and signals indicating said opening degrees are transmitted to the second valve28and the differential pressure regulating valve29. By thus controlling the fuel supply to the combustor4with the controller15, the fuel supply amount is decreased from the initial fuel supply amount F0toward the minimum supply amount Fmindescribed later, while controlling the pressure of the fuel supplied to the main nozzle and the pilot nozzle. As a result, the load of the gas turbine system10decreases and becomes the minimum load Lminat the time t1. Herein, the operation at the minimum load Lminis a no-load constant-speed operation, and means an operation in a state where the fuel supply amount to the combustor4in the normal operation mode is set to the minimum value, that is, the minimum supply amount Fmin.

In the present embodiment, from the time t0to the time t2, the controller15maintains the opening degree of the first valve27at an initial opening degree O1_0and decreases the opening degree of the second valve28from the initial O2_0to O2_1at time the t1, thereby controlling the pressure of the fuel supplied to the main nozzle to the set value. Further, along with decreasing the fuel supply amount to each of the main nozzle and the pilot nozzle at the time t0, the controller15starts increasing the pilot ratio (the ratio of the fuel supply amount to the pilot nozzle to the fuel supply amount to the combustor4) from the initial Pilot ratio R0. Consequently, even if the fuel supply amount to the combustor4decreases, a state is possible in which the combustor4is more unlikely to misfire. Before reaching the time t1, the pilot ratio increases from R0to R1. Further, at the time t0, the controller15may control the actuator3B, thereby adjusting the opening degree of the IGV3A to such an opening degree at which the combustor4does not misfire.

The operating condition at the time t1is maintained from the time t1to the time t2. The operation period from the time t1to the time t2is a time for receiving a command signal from the operator, or a command signal from the gas turbine system10or another system connected to the gas turbine system10, as to switching of the operation mode. At the time t2, for example, the operator of the gas turbine system10presses an operation mode switch button to start switching from the normal operation mode to the reverse power operation mode. At the time t2, the controller15starts increasing the pilot ratio while maintaining the fuel supply amount to the combustor4at the minimum supply amount Fmin, and sets the pilot ratio to R2at the time t3.

In order to increase the pilot ratio from R1to R2while maintaining the fuel supply amount to the combustor4at the minimum supply amount Fmin, the controller15decreases the opening degree of the main fuel control valve23and increases the opening degree of the pilot fuel control valve24. At this time, the controller15increases the opening degree of the first valve27from the time t2to the time t3and decreases the opening degree of the second valve28substantially synchronously, such that the detected value of the differential pressure gauge25becomes the set value. At the time t1when the pilot ratio is R2, the opening degree of the second valve28decreases to O2_2and the opening degree of the first valve27increases to O1_1. Further, between the time t2and the time t3, the controller15may control the actuator3B, thereby controlling the opening degree of the IGV3A to such an opening degree suitable for the reverse power operation mode.

From the time t3to time t5, the controller15controls the fuel flow rate set value to the combustor4, thereby decreasing the fuel supply amount from Fminto a supply amount FGMfor the reverse power operation mode. The controller15transmits, based on the fuel flow rate set value and the value of the pilot ratio, signals indicating information on the opening degrees to the main fuel control valve23and the pilot fuel control valve24, respectively. Further, the opening degree of the first valve27and the opening degree of the differential pressure regulating valve29are adjusted, respectively, such that respective detected values of the differential pressure gauges25and26become target differential pressure set values.

Specifically, after the time t3, the controller15keeps the opening degree of the second valve28constant at O2_2(including keeping the second valve28fully closed) and regulates the differential pressure between the upstream side and the downstream side of the main fuel control valve23only by adjusting the opening degree of the first valve27, thereby regulating the pressure of the fuel supplied to the main nozzle. Although not shown inFIG.4, in the normal operation mode before the time t0, the fuel supply amount to the combustor4is large relative to the reverse power operation mode, and thus a regulation target for regulating the pressure of the fuel supplied to the main nozzle is the second valve28. Therefore, the controller15changes the regulation target for regulating the pressure of the fuel supplied to the main nozzle from the second valve28to the first valve27after the time t3.

Although the load of the gas turbine system10becomes zero at time t4, the fuel supply amount to the combustor4is decreased by further decreasing the fuel flow rate set value. After the time t4, electric power is supplied from the power system8to the motor generator7. Therefore, after the time t4, the motor generator7is driven as the motor, and the rotational power generated by the motor generator7is provided to the gas turbine1. At the time t5, the fuel supply amount to the combustor4reaches the fuel supply amount FGMfor the reverse power operation mode, and the switching operation to the reverse power operation mode is completed. At this time, the opening degree of the first valve27decreases to O1_2. Although O1_2>O1_0holds inFIG.4, O1_2≤O1_0can be established depending on the magnitude of the opening degree O1_0of the first valve27in the normal operation mode.

In the present embodiment, the pressure of the fuel supplied to the main nozzle is regulated only by adjusting the opening degree of the first valve27, in the reverse power operation mode. Therefore, the discontinuity of the fuel supply amount based on valve characteristics is eliminated by the absence of switching between the first valve27and the second valve28in the reverse power operation mode, making it possible to suppress fluctuation in operation of the gas turbine1and making it possible to appropriately control the fuel supply to the gas turbine1during operation in the reverse power operation mode.

Modified Example of Operation of Fuel Control Device for Gas Turbine According to Embodiment of Present Disclosure

In the present embodiment, the regulation target for regulating the pressure of the fuel supplied to the main nozzle is changed from the second valve28to the first valve27by the time t3, that is, by the time when the load of the gas turbine system10starts to decrease from the minimum load Lmin. However, the present disclosure is not limited to this form. Such a change may be made at least by the time t5, that is, by the time when the switching operation to the reverse power operation mode is completed by decreasing the fuel supply amount to the combustor4to FGM. Thus, such a change can also be made before the time t3, for example, before the fuel supply amount to the combustor4is decreased to the flow rate for no-load constant-speed operation, that is, by the time t1. By doing so, it is possible to appropriately control the fuel supply to the gas turbine even during switching from the normal operation mode to the reverse power operation mode.

In the present embodiment, when switching from the normal operation mode to the reverse power operation mode, the opening degree of the first valve27is made to be larger than the opening degree in the normal operation mode and the opening degree of the second valve28is made to be smaller than the opening degree in the normal operation mode, and then the regulation target for regulating the fuel pressure is changed from the second valve28to the first valve27, but this operation is not essential. However, by performing such operation, it is possible to more appropriately control the fuel supply to the combustor in the reverse power operation mode.

In the present embodiment, the opening degree of the second valve28has the constant value after the regulation target for regulating the pressure of the fuel supplied to the main nozzle is changed from the second valve28to the first valve27. However, the present disclosure is not limited to this form. A state may be possible in which the opening degree of the second valve28fluctuates within a very narrow range regardless of the regulation of the pressure of the fuel supplied to the main nozzle. However, if the opening degree of the second valve28is maintained at the constant value, the regulation target for regulating the fuel pressure in the reverse power operation mode can completely be only the first valve27, making it possible to more appropriately control the fuel supply to the combustor4in the reverse power operation mode.

In the present embodiment, the two valves having different valve characteristics, that is, the first valve27and the second valve28are used as the differential pressure regulating valves for regulating the pressure of the fuel supplied to the main nozzle. However, the present disclosure is not limited to this form, and two valves having the same valve characteristics may be used. In this modified example, the regulation target for regulating the pressure of the fuel supplied to the main nozzle is the two valves in the normal operation mode, and the regulation target for regulating the pressure of the fuel supplied to the main nozzle is only one of the two valves in the reverse power operation mode. Also in this modified example, the discontinuity of the fuel supply amount is eliminated by the absence of switching of the number of regulation target valves in the reverse power operation mode, making it possible to suppress fluctuation in operation of the gas turbine1and making it possible to appropriately control the fuel supply to the combustor4.

In this modified example, the number of valves is not two, but may be any number of not less than three. In this case, the same technical effect can be obtained by setting the regulation target for regulating the pressure of the fuel supplied to the main nozzle to at least two valves among not less than three valves in the normal operation mode and setting the regulation target for regulating the pressure of the fuel supplied to the main nozzle to any one of not less than three valves in the reverse power operation mode.

In the present embodiment, electric power is supplied from the power system8to the motor generator7in the reverse power operation mode. However, the present disclosure is not limited to this form. The motor generator7may be supplied with electric power that is excessive in another plant or the like.

In the present embodiment, only the regulation of the pressure of the fuel supplied to the main nozzle has been described. However the pressure of the fuel supplied to the pilot nozzle can also be regulated by performing the same control with the configuration where the differential pressure regulating valve29is formed of the first valve and the second valve.

The contents described in the above embodiments would be understood as follows, for instance.

[1] A fuel control device for a gas turbine according to one aspect is a fuel control device (20) for a gas turbine (1), the gas turbine (1) including a compressor (2) for producing compressed air, a combustor (4) for burning fuel with the compressed air, and a turbine (6) driven by a combustion gas generated by burning the fuel in the combustor (4), and being switchable between a normal operation mode which is an operation mode where a motor generator (7) is driven by the turbine (6) and a reverse power operation mode which is an operation mode where the motor generator (7) provides the rotational power to the gas turbine (1), the fuel control device (20) including: a first valve (27) capable of regulating a pressure of the fuel supplied to the combustor (4) within a flow rate range of a first lower limit value (F1_min) and a first upper limit value (F1_max); and a second valve (28) capable of regulating the pressure of the fuel supplied to the combustor (4) within a flow rate range of a second lower limit value (F2_min) larger than the first lower limit value (F1_min) and a second upper limit value (F2_max) larger than the first upper limit value (F1_max). A regulation target for regulating the pressure of the fuel is changed from the second valve (28) to the first valve (27) before a flow rate of the fuel is decreased to a flow rate for the reverse power operation mode, when switching from the normal operation mode to the reverse power operation mode.

With the fuel control device for the gas turbine according to the present disclosure, the discontinuity of the fuel supply amount based on valve characteristics is eliminated during operation in the reverse power operation mode by the absence of switching between the first valve and the second valve in the reverse power operation mode, making it possible to suppress fluctuation in operation of the gas turbine and making it possible to appropriately control the fuel supply to the combustor.

[2] A fuel control device for a gas turbine according to another aspect is the fuel control device for the gas turbine of [1], wherein the regulation target for regulating the pressure of the fuel is changed from the second valve (28) to the first valve (27) before the flow rate of the fuel is decreased to a flow rate (Fmin) for no-load constant-speed operation, when switching from the normal operation mode to the reverse power operation mode.

With such configuration, it is possible to appropriately control the fuel supply to the combustor even during switching from the normal operation mode to the reverse power operation mode.

[3] A fuel control device for a gas turbine according to still another aspect is the fuel control device for the gas turbine of [1] or [2], wherein the regulation target for regulating the pressure of the fuel is changed from the second valve (28) to the first valve (27) after an opening degree of the first valve (27) is made to be larger than an opening degree in the normal operation mode and an opening degree of the second valve (28) is made to be smaller than the opening degree in the normal operation mode, when switching from the normal operation mode to the reverse power operation mode.

With such configuration, since the amount of the decrease in fuel flow rate by the first valve can be increased, it is possible to more appropriately control the fuel supply to the combustor in the reverse power operation mode.

[4] A fuel control device for a gas turbine according to yet another aspect is the fuel control device for the gas turbine of any of [1] to [3], wherein an opening degree of the second valve (28) is maintained at a constant value after the regulation target for regulating the pressure of the fuel is changed from the second valve (28) to the first valve (27).

With such configuration, the regulation target for regulating the fuel pressure during operation in the reverse power operation mode can completely be only the first valve, making it possible to more appropriately control the fuel supply to the combustor during operation in the reverse power operation mode.

[5] A fuel control device for a gas turbine according to one aspect is a fuel control device (20) for a gas turbine (1), the gas turbine (1) including a compressor (2) for producing compressed air, a combustor (4) for burning fuel with the compressed air, and a turbine (6) driven by a combustion gas generated by burning the fuel in the combustor (4), and being switchable between a normal operation mode which is an operation mode where a motor generator (7) is driven by the turbine (6) and a reverse power operation mode which is an operation mode where the motor generator (7) provides the rotational power to the gas turbine (1), the fuel control device (20) including a plurality of valves capable of regulating a pressure of the fuel supplied to the combustor (4). A regulation target for regulating the pressure of the fuel is at least two valves among the plurality of valves, in the normal operation mode. The regulation target for regulating the pressure of the fuel is changed to one valve among the plurality of valves before a flow rate of the fuel is decreased to a flow rate for the reverse power operation mode, when switching from the normal operation mode to the reverse power operation mode.

With the fuel control device for the gas turbine according to the present disclosure, the discontinuity of the fuel supply amount based on valve characteristics is eliminated during operation in the reverse power operation mode by the absence of switching between the first valve and the second valve in the reverse power operation mode, making it possible to suppress fluctuation in operation of the gas turbine and making it possible to appropriately control the fuel supply to the combustor.

REFERENCE SIGNS LIST

1Gas turbine2Compressor4Combustor6Turbine7Motor generator10Gas turbine system20Fuel control device27First valve28Second valve