JPH06101501A - Method and device for fuel control in gas turbine - Google Patents

Abstract

PURPOSE:To provide a method and device for fuel control in a gas turbine which can effectively and certainly prevent damage of a ceramic material resulting from rapid change in the temp. of a working fluid even when the gas turbine undergoes a rapid change in the operating conditions. CONSTITUTION:A gas turbine of ceramic is equipped with adjustability for the rate of fuel flow supplied to a fuel injection valve 10 furnished on a combustor 2, wherein the flow path to the valve 10 is branched into two lines, and a main fuel shutoff valve 15 is connected with one of the flow paths while an aux. fuel control valve 16 is connected with the other flow path, and further an operation control means 17 is furnished to make control of the operations of these main fuel shutoff valve 15 and aux. fuel control valve 16. When the gas turbine undergoes a rapid change in its operating conditions. for example a turbine trip, the rate of fuel flow to the combustor 2 is controlled for controlling the temp. of the combustion gas flowing therefrom into the turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine equipped with ceramic moving blades and stationary blades, and more particularly to a gas turbine fuel for reducing unsteady thermal stress generated in ceramics when the gas turbine is rapidly changed in operating condition. The present invention relates to a control device and a fuel control method thereof.

[0002]

2. Description of the Related Art Generally, there is a gas turbine as shown in FIG. That is, the air compressed by the compressor 1 is supplied to the combustor 2, where the fuel passes through the fuel cutoff valve 3 and is driven by the fuel injection pump 6 driven by the drive device 5 connected to the rotating shaft 4 of the gas turbine. The pressure of the fuel is increased by the fuel bypass control valve 7 to return the fuel to the primary side of the fuel injection pump 6, and the remaining fuel passes through the flow distributor 8 and the check valve 9 to the fuel injection valve 6. 10 is supplied and burned. The high temperature, high pressure combustion gas generated as a result of combustion in the combustor 2 works in the turbine 11 to drive a driven machine such as the generator 12.

In this type of gas turbine, it is known that when the turbine inlet temperature is raised, the thermal efficiency of the gas turbine is improved. In order to enhance the thermal efficiency of the gas turbine, various measures are taken to raise the turbine inlet temperature. Has been. In order to raise the turbine inlet temperature, it is necessary for the components of the gas turbine to be designed to withstand the hot combustion gases.

Therefore, in recent years, it has been attempted to use ceramics having excellent heat resistance as the material of the moving blades / stator blades and the combustor 2 which are the main components of the gas turbine.

When the gas turbine trips, the fuel cutoff valve 3 is cut off and the fuel bypass control valve 7 is opened.
As shown in FIG. 5 (A), operation control for rapidly reducing the fuel flow rate Q is performed.

When such control is performed, the combustion gas temperature T changes abruptly as shown in FIG. 5 (B) when the operating conditions such as a trip of the gas turbine changes abruptly, and the turbine rotor blades forming the gas passage portion are changed. -The material of the stationary blades and the combustor 2 causes a sudden unsteady temperature gradient.

[0007]

As described above, in the conventional fuel control device for a gas turbine, the combustion gas temperature T is set so that the fuel flow rate Q is sharply cut off when the operating conditions change such as when the turbine trips. It will fall sharply. Since the material temperature of the gas turbine rotor blades / stator blades and the combustor 2 that constitute the gas passage portion through which the combustion gas passes mainly follows the combustion gas temperature T, a rapid unsteady temperature gradient occurs, and these Thermal stress is generated in the components.

Generally, a ceramic material has a characteristic that, unlike a metal material, it does not undergo plastic deformation and causes brittle fracture. Further, in the method of manufacturing a ceramic material, it is impossible to eliminate all the minute defects existing in the material. Therefore, even if the ceramic material has an instantaneous unsteady stress, it will be immediately destroyed when a stress exceeding the limit stress is applied.

Therefore, in the ceramic gas turbine using the ceramic material for the turbine rotor blades / stator blades constituting the gas passage and the combustor 2, the temperature of the ceramic material is unsteady when the temperature changes suddenly such as trip. There has been a problem that the temperature gradient becomes extremely large, the brittle fracture of the ceramic material, and a serious accident may occur.

The present invention has been made in consideration of the above circumstances, and it is possible to effectively and surely prevent damage to a ceramic material due to a sudden change in working fluid temperature even when the operating conditions of the gas turbine change suddenly. An object of the present invention is to provide a fuel control device for a gas turbine and a fuel control method thereof.

[0011]

In order to solve the above-mentioned problems, a fuel control device for a gas turbine according to the present invention is
In a ceramic gas turbine capable of adjusting a fuel flow rate supplied to a fuel injection valve provided in a combustor, a flow path to the fuel injection valve is branched into two systems, and a main fuel cutoff valve is connected to one flow path. Then, an auxiliary fuel control valve is connected to the other flow path, and operation control means for operating and controlling the main fuel cutoff valve and the auxiliary fuel control valve is provided, and the combustor is operated when the operating conditions change suddenly such as a turbine trip. The fuel flow rate to the turbine is controlled to control the temperature of the combustion gas flowing into the turbine from the combustor.

Further, in the fuel control method for a gas turbine according to the present invention, the trip condition of the gas turbine made of ceramics is divided into at least two types according to the degree of damage, and the combustor is operated under the first trip condition of the trip conditions. The main fuel supplied to the fuel cell was shut off, then the auxiliary fuel flow rate was gradually reduced, and both the main fuel and the auxiliary fuel were shut off under the second type trip condition.

[0013]

In the present invention having the above construction, the ceramic gas turbine uses the ceramic material for the turbine blades / stator blades and the combustor. It is considered that the temperature of the ceramics used for the moving and stationary blades of a gas turbine matches the combustion gas.

From this point of view, the fuel control device for a gas turbine according to the present invention controls the flow rate of fuel supplied to the combustor at the time of a sudden change in operating conditions such as a turbine trip of the gas turbine so that the combustor changes the turbine flow to the turbine. By controlling the temperature of the inflowing combustion gas, it is possible to suppress temporal changes in the temperature of the ceramics.

Further, in the fuel control method for a gas turbine according to the present invention, at the time of turbine trip, trip conditions are divided into at least two types. For example, when divided into two types, the first
Type 2 conditions are such that damage to turbines and combustors is relatively minor and damage is limited to the inside of equipment such as turbines, and Type 2 conditions are damage due to defects that are relatively severe, and equipment such as turbines. To the outside of the plant, that is, to the extent that the entire plant may be damaged.

When the turbine trips under the first type condition, the main fuel is shut off immediately after the trip, and then the auxiliary fuel is gradually reduced to suppress the temporal change of the temperature of the ceramics. Generation of thermal stress can be suppressed to a low level.

Further, when the turbine trips in the final condition, for example, the second type condition, the combustion gas temperature rapidly decreases to the discharge temperature from the compressor, so that thermal stress exceeding the allowable limit may occur in the ceramics. However, by rapidly stopping the turbine, it is possible to prevent the turbine trip from being adversely affected to other devices than the gas turbine, that is, the entire plant.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of a ceramics gas turbine provided with a first embodiment of a fuel control device for a gas turbine according to the present invention. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIG.

As shown in FIG. 1, in the gas turbine fuel system, a rotary shaft 4 of the gas turbine is provided downstream of the fuel cutoff valve 3.
A fuel injection pump 6 driven by a drive device 5 connected to the fuel injection pump 6 is provided, and a part of the flow rate is controlled by the fuel bypass control valve 7 to be returned to the primary side of the fuel injection pump 6.

Further, the secondary side of the fuel injection pump 6 is branched into two flow passages, one of which is connected to the main fuel cutoff valve 15 and the other of which is provided with an auxiliary fuel control valve 16. It is connected. Then, the fuel passes through the main fuel cutoff valve 15 and the auxiliary fuel control valve 16, respectively, merges again, passes through the flow rate distributor 8, passes through the check valve 9, is supplied to the fuel injection valve 10, and is burned.

The operation of the fuel cutoff valve 3, the fuel bypass control valve 7, the main fuel cutoff valve 15 and the auxiliary fuel control valve 16 is controlled by a control signal from a trip condition judging device 17 as an operation control means. The trip condition determination device 17 is divided into at least two types (two stages) according to the degree of the trip condition of the turbine trip, and the trip signal of the first type,
… It outputs the last type of trip signal.

Next, the operation of this embodiment will be described. In addition,
In the following description, for simplification, an example of dividing the trip condition into two types will be described.

The trip condition discriminating device 17 discriminates the trip condition by inputting detection signals such as a vibration level of the rotating shaft 4 of the gas turbine and an exhaust gas temperature measured by a sensor (not shown). Axis of rotation 4
When the vibration level (amplitude) of 10 is 100/100 mm, an alarm signal is output, and when it is 15/100 mm, the first type trip signal is output, and when it is 50/100 mm, the second type trip signal is output.

When detecting the exhaust gas temperature, an alarm signal is output when the exhaust gas temperature is, for example, 600 ° C., and a first signal is output when the exhaust gas temperature is 620 ° C.
The second type trip signal is output at 660 ° C., and the second type trip signal is output at 660 ° C. An alarm signal (not shown) is activated by an alarm signal from the trip condition determining device 17, while the main fuel shutoff valve 15 is shut off by a first type trip signal and the main fuel shutoff valve 15 is shut by a second type trip signal. Both the auxiliary fuel control valve 16 and the auxiliary fuel control valve 16 are shut off.

In addition to the vibration level of the rotating shaft 4 of the gas turbine and the exhaust gas temperature, the trip condition determining device 17
Some are shown in Table 1.

[0027]

[Table 1]

As shown in Table 1 above, the rotation speed of the rotary shaft 4, the bearing oil supply pressure of the rotary shaft 4, the bearing oil discharge temperature, the degree of internal failure of the generator, the open / close state of the generator circuit breaker, and the presence or absence of fire. Etc. may be detected to determine the first type and the second type trip conditions, or they may be comprehensively combined for determination.

Next, a first embodiment of a fuel control method for a gas turbine according to the present invention will be described.

During normal operation load of the gas turbine, the main fuel cutoff valve 15 and the auxiliary fuel control valve 16 are opened so that the auxiliary fuel control valve 16 has a constant opening and the required fuel flow rate is supplied by the fuel bypass control valve 7. . The main fuel cutoff valve 15 is closed at the time of the first type trip, and then the auxiliary fuel control valve 16
Is gradually narrowed down, the fuel flow rate is gradually reduced, and after a lapse of a certain time from the turbine trip or after the rotation speed falls below a certain value, the auxiliary fuel control valve 16 is closed. During the second type trip, the main fuel cutoff valve 15 and the auxiliary fuel control valve 16 are closed to cut off the fuel.

When the ceramics gas turbine trips under the first type trip condition during the rated operation, the fuel bypass control valve opening a is increased immediately after the turbine trip as shown in FIG. 2 (B). , The fuel flow rate is rapidly reduced to the auxiliary fuel flow rate, and thereafter the auxiliary fuel control valve opening degree b is gradually decreased.

At the stage where the auxiliary fuel control valve 16 is gradually narrowed down, as shown in FIG. 2 (A), the combustion gas temperature T
The rate of change is also small, the unsteady thermal stress of the generated ceramics is also small, and it is possible to prevent the ceramics from being damaged.

In general, the fuel control valve has a limit in the control range of the fuel flow rate, and one control valve cannot cover the low flow rate range after the trip. In the case of a ceramics gas turbine, it is especially important to prevent misfire, and in the present embodiment, the auxiliary fuel control valve 16 corresponding to the region where the fuel flow rate is small is used, so that the stability is high.

FIG. 3 shows a second embodiment of the fuel control device for a gas turbine according to the present invention, and the same parts as those of the first embodiment will be described with the same reference numerals.

The fuel control system for a gas turbine of this embodiment is basically different from the fuel control system shown in FIG. 1 in the structure of the fuel system for supplying fuel to the combustor 2. That is, the fuel is gas fuel whose pressure is sufficiently high, and the speed ratio control valve 2
It is controlled so that the secondary pressure is proportional to the speed of the gas turbine by 0, the secondary side is branched into two systems, the fuel control valve 21 is connected to one flow passage, and the other flow passage is connected to the other flow passage. The auxiliary fuel control valve 16 is connected. Then, the fuel passes through the fuel control valve 21 and the auxiliary fuel control valve 16, respectively, and merges again to be supplied to the fuel injection valve 10 and burned.

The speed ratio control valve 20, the fuel control valve 21, and the auxiliary fuel control valve 16 are operation-controlled by a control signal from the trip condition determining device 17.

Next, a second embodiment of the fuel control method for a gas turbine according to the present invention will be described.

During normal operation load of the gas turbine, the fuel control valve 21 and the auxiliary fuel control valve 16 are opened so that the auxiliary fuel control valve 16 has a constant opening and the required fuel flow rate is supplied by the fuel control valve 21. During the first type trip, the fuel control valve 21 is closed, then the auxiliary fuel control valve 16 is gradually narrowed down, the fuel flow rate is gradually reduced, and after a lapse of a certain time from the turbine trip or the rotation speed falls below a certain value. After that, the auxiliary fuel control valve 16 is closed.

During the second type trip, the fuel control valve 21 and the auxiliary fuel control valve 16 are closed to shut off the fuel. In this case, the fuel control valve 21 also has the function of the main fuel cutoff valve 15 in the fuel control device shown in FIG. 1, and since the other configurations and operations are the same as those in the first embodiment, the description thereof will be omitted. To do.

[0040]

As described above, according to the fuel control device for a gas turbine of the present invention, the fuel flow rate to the combustor is controlled when the operating condition changes abruptly, such as when the turbine trips. By controlling the temperature of the combustion gas flowing into the furnace, the unsteady temperature gradient of the ceramic material is reduced, brittle fracture of the ceramic material is effectively prevented, and the safety and reliability of the gas turbine are improved. Can be planned.

Further, in the fuel control method for a gas turbine according to the present invention, the trip condition of the turbine trip is divided into at least two types according to the degree of damage, and the main fuel is shut off immediately after the turbine trip under the first type trip condition. Then
Since the temperature of the combustion gas is gradually decreased by the auxiliary fuel, the unsteady thermal stress generated in the ceramic material during the turbine trip can be reduced as much as possible, and the ceramic gas turbine can be safely stopped in an emergency to minimize the damage. it can.

Furthermore, in the second type of trip condition, the main fuel and the auxiliary fuel are shut off immediately after the trip, and even if the ceramic material is damaged, the adverse effect of the damage is prevented from reaching the outside, and the overall The damage can be minimized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a ceramics gas turbine provided with a first embodiment of a fuel control device for a gas turbine according to the present invention.

2 (A) and 2 (B) are characteristic diagrams showing temporal changes in state quantities at the time of turbine trip in the embodiment of FIG.

FIG. 3 is a schematic configuration diagram showing a ceramics gas turbine including a second embodiment of the fuel control device for a gas turbine according to the present invention.

FIG. 4 is a schematic configuration diagram showing a fuel control device for a conventional gas turbine.

5 (A) and 5 (B) are characteristic diagrams showing temporal changes in state quantities when a conventional gas turbine trips.

[Explanation of symbols]

 1 Compressor 2 Combustor 3 Fuel cutoff valve 4 Rotating shaft 5 Drive device 6 Fuel injection pump 7 Fuel bypass control valve 8 Flow distributor 9 Check valve 10 Fuel injection valve 11 Turbine 12 Generator 15 Main fuel cutoff valve 16 Auxiliary fuel Control valve 17 Trip condition determination device (operation control means) 20 Speed ratio control valve 21 Fuel control valve

Claims (2)

[Claims] 1. In a ceramic gas turbine capable of adjusting a fuel flow rate supplied to a fuel injection valve provided in a combustor, a flow path to the fuel injection valve is branched into two systems, and one of the flow paths is mainly connected to the main flow path. A fuel cutoff valve is connected, an auxiliary fuel control valve is connected to the other flow path, and operation control means for controlling the operation of the main fuel cutoff valve and the auxiliary fuel control valve is provided to rapidly change operating conditions such as a turbine trip. A fuel control device for a gas turbine, wherein a fuel flow rate to the combustor is controlled at a time to control a temperature of combustion gas flowing into the turbine from the combustor. 2. The trip condition of the gas turbine made of ceramics is divided into at least two types according to the degree of damage, and the first type of trip conditions among them is used to shut off the main fuel supplied to the combustor, and then continue. A fuel control method for a gas turbine, characterized in that the auxiliary fuel flow rate is gradually reduced and the main fuel and the auxiliary fuel are shut off under a second type trip condition.