JPH05256166A - Gas turbine control method - Google Patents

Abstract

PURPOSE:To prevent the unstable combustion of a burner generated by the slippage of an air-feel ratio at the decreasing time of fuel flow by outputting the opening degree closing command signal of an inlet guide vane only at the decreasing time of fuel flow so as to control the air flow of an air compressor in the throttled direction. CONSTITUTION:A fuel flow command signal 9 outputted from a control device 10 is passed through a primary delay element 30 so as to be made into a fuel flow command signal 31 including primary delay, and this fuel flow command signal 31 is added as the minus value together with the fuel flow command signal 9 by an adder 32. As a result, the fuel flow is discriminated whether to have a decreasing, constant or increasing tendency according to whether the added value is the negative, zero or positive value. When the fuel flow command signal 9 has a decreasing tendency, the opening degree closing command signal 33 of an inlet guide vane 7 corresponding to this decreasing tendency is interposed as the differential value of a proportional plus integrator- differentiator 27 and set as an inlet guide vane opening command signal 28 to operate an inlet guide vane drive unit 29. This enables the high-speed follow-up of the inlet guide vane 7 to the decrease of fuel flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a gas turbine, and more particularly to a method for controlling a fuel-air ratio in a premixed combustion section of a gas turbine.

[0002]

2. Description of the Related Art An example of a conventional technique relating to a gas turbine control method will be described with reference to the drawings. FIG. 3 is an explanatory diagram of a conventional gas turbine control method, in which 1 is air, 2 is an air compressor, 3a and 3b are fuels, 4 is a combustor, 5 is combustion gas, 6 is a turbine section, and 7 is Inlet guide vanes, 8 load command signal, 9 fuel flow command signal, 10 control device, 11 fuel flow control valve, 12 exhaust gas, 13 first stage combustion section,
14 is the second-stage combustion section, 15 is air to the second-stage combustion section, 1
6 is a fuel nozzle, 17 is a mixer, 18 is an air flow rate control mechanism, 19 is compressed air, 20 is air to the first stage combustion section, 2
1 is cooling air, 22 is a temperature or pressure signal of compressed air, 23 is a function generator, 24 is an exhaust gas temperature set value signal, 25 is a comparator, 26 is a control value signal, 27 is proportional-integral-derivative Reference numeral 28 denotes an inlet guide vane opening command signal, and 29 denotes an inlet guide vane drive device.

The gas turbine includes an air compressor 2 for compressing air 1 taken from the outside air, and a fuel 3 mixed with the air 1.
a turbine section 6 that is rotated and works by a combustor 4 that combusts a and 3b and a combustion gas 5 that is generated at this time.
Composed of and.

Regarding the flow rates of the fuels 3a and 3b, the required flow rate command signal 8 causes the control apparatus 10 to issue the fuel flow rate command signal 9 to control the fuel flow rate control valve 11 so that the required amount flows into the combustor 4. To be done.

As the combustor 4, a premixed combustion type low NOx combustor designed to reduce NOx is adopted.
Is composed of a first-stage combustion section 13 and a second-stage combustion section 14, and fuel 3a is supplied to the first-stage combustion section and fuel 3b is supplied to the second-stage combustion section.

The second-stage combustion section 14 is of a premixing type in which the air 15 to the second-stage combustion section and the fuel 3b from the fuel nozzle 16 are mixed in the mixer 17.

The air 1 flowing into the air compressor 2 is sucked through an inlet guide vane 7 provided at the inlet of the air compressor 2, and the air flow rate to the air compressor 2 is controlled by the inlet guide vane 7. It

That is, the blade opening of the inlet guide vane 7 is variable, the blade opening is changed as necessary, and the flow rate of the air 1 flowing into the air compressor 2 is controlled.

The air 1 is pressurized by the air compressor 2, becomes compressed air 19 and is guided to the combustor 4, where it is mixed with the fuel 3 and burned, and the combustion gas 5 generated at this time is generated by the turbine section 6. Flow into.

The compressed air 19 is the air 2 to the first stage combustion section.
The air 15 and the cooling air 21 are separately supplied to the 0th and second stage combustion sections.

The flow rate of the air 15 to the second stage combustion section is controlled by the air flow rate control mechanism 18 and the inlet guide vanes 7 so as to have a predetermined fuel-air ratio according to the flow rate of the fuel 3b.

That is, the flow rate of the air 15 to the second stage combustion section is controlled by the air flow rate control mechanism 18 by the fuel flow rate command signal 9.
Is operated and controlled locally, and the air flow rate to the air compressor 2 is controlled so that the combustion gas 5 at the outlet of the combustor 4 has a predetermined temperature.

In the above, the temperature of the combustion gas 5 in the combustor 4 changes due to the change in the flow rate of the fuel 3a, 3b.
Due to the restriction of heat resistant temperature of the components of the turbine unit 6, the turbine unit 6
When the turbine section 6 reaches the upper limit temperature, the inlet guide vanes 7 operate to control the flow rate of the air 1 at the inlet of the air compressor 2, and the turbine section 6
Is controlled to be below the upper limit temperature.

Particularly in the case of a combined cycle power plant combining a gas turbine and a steam turbine, exhaust gas 1
Since maintaining the temperature of 2 higher will lead to higher efficiency of the plant, the inlet air guide blades 7 will be throttled as much as possible to increase the fuel-air ratio (fuel flow rate / air flow rate) and the temperature of the turbine section 6 will be increased. Consideration is given to approaching the limit temperature as close as possible. Specifically, instead of the temperature of the combustion gas 5, the temperature of the exhaust gas 12 having a close relationship with the temperature of the combustion gas 5 is measured and controlled.

When the load command signal 8 is issued, the fuel flow control valve 11 is controlled to an appropriate opening in a very short time, and 2
The flow rate of the air 15 to the stage combustion section is quickly controlled by the air flow rate control mechanism 18 as in the case of the fuel flow rate control valve 11.

On the other hand, the opening degree of the inlet guide vanes 7 is such that the exhaust gas 1
The temperature of 2 is measured and controlled based on this temperature. That is, a change in the flow rate of the fuel 3a, 3b causes a change in the temperature of the combustion gas 5 and then a change in the temperature of the exhaust gas 12, and the temperature of the exhaust gas 12 is measured. 15, and each flow rate of the air 20 to the first stage combustion section is controlled.

Specifically, the upper limit value of the temperature of the exhaust gas 12 is set in advance by the signal 22 of the temperature or pressure of the compressed air, and this is incorporated as a function generator 23 to output the exhaust gas temperature set value signal. 24 is emitted.

The deviation between this set value and the actual temperature of the exhaust gas 12 is compared by the comparator 25, the deviation value is output as the control value 26, and the inlet guide vane opening is output via the proportional-integral-differentiator 27. In response to the command signal 28, the inlet guide vane drive device 29 is operated.

The technique related to the present invention is, for example,
It is disclosed in Japanese Patent Laid-Open No. 58-38328.

[0020]

As described above, in the conventional technique, the air flow rate is changed after the change of the fuel flow rate, and the fuel-air ratio temporarily shifts. For this reason, the fuel-air ratio tends to be low, especially when the load fluctuates when the load is in a reduced state.
Combustion becomes unstable in the Ox combustor.

An object of the present invention is to secure stable combustion in a gas turbine having a low NOx combustor, which tends to become unstable when the fuel-air ratio becomes small when the load changes and the load changes. It is to improve so that it can be done.

[0022]

The above object can be achieved as follows.

(1) In the method of controlling a gas turbine, which controls each flow rate of fuel and air flowing into the combustor and receives the inlet guide vane opening command signal to control the air flow rate to the air compressor, Only when the flow rate decreases, generate the inlet guide vane opening close command signal to control the air flow rate to the air compressor.

(2) In (1), the decrease in the flow rate of fuel is detected by using a combination of a temporary delay unit and an adder.

[0025]

[Function] The fuel flow rate command signal is taken in through a circuit with a temporary delay, and further the fuel flow rate command signal is directly taken in. If the fuel flow rate command signal indicates that the fuel flow rate is in a decreasing state due to the difference between the two signals, this state is set. The detection is made by using a combination of a temporary delay unit and an adder.

Therefore, the opening degree of the inlet guide vanes of the air compressor can be controlled in the closing direction in advance according to the magnitude of the difference between the two signals, and combustion is unstable due to a temporary decrease in the fuel-air ratio. Can be prevented.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an explanatory diagram of a gas turbine control method of the present invention, and FIG. 2 is a comparative diagram of the present invention and a conventional example relating to gas turbine control. Reference numeral 30 is a temporary delay device, and 31 is a temporary delay device. Included fuel flow rate command signal, 32 is adder, 33
Indicates a command signal to close the opening of the inlet guide vane, and the other symbols are the same as those mentioned above.

The fuel flow rate command signal 9 issued from the control unit 10 is made into a fuel flow rate command signal 31 including a temporary delay through a temporary delay unit 30, and this is set as a negative value to be a plus value of the fuel command signal 9 from the control unit 10. Adder 32
Is added using.

If the added value is a negative value, the fuel flow rate tends to decrease, if it is zero, the fuel flow rate is constant, and if it is a positive value, the fuel flow rate tends to increase. There is. When the fuel flow rate command signal 9 indicates a decrease in the fuel flow rate, the opening degree close command signal 33 for the inlet guide vanes, the opening degree of which is set in advance to correspond to the amount of decrease, is transmitted to the exhaust gas 12
Control value signal 2 generated from the deviation from the set temperature of the
Before 6 is output, it intervenes as a differential value of the proportional-integral-differentiator 27, and becomes the inlet guide vane opening command signal 28 to operate the inlet guide vane drive device 29.

In this case, the command signal 3 for closing the opening of the inlet guide vanes
Since 3 is input as the differential value of the proportional-integral-differentiator 27, the control speed of the inlet guide vane 7 becomes faster, and as a result, the opening degree of the inlet guide vane 7 follows the decrease of the fuel flow rate faster.

That is, the air flow rate decreases corresponding to the fuel flow rate, and the deviation of the fuel-air ratio can be prevented.

Next, a comparison between the present invention and the conventional example relating to the control of the gas turbine will be described with reference to FIG.

As shown in FIG. 2, when the fuel flow rate command signal based on the load command changes over time and the fuel flow rate command signal indicates a decrease in the fuel flow rate, the opening of the inlet guide vane is In the present invention, as indicated by the solid line, the air flow rate changes substantially in synchronization with the fuel flow rate command signal, and the air flow rate can be reduced.

Therefore, it is possible to suppress the decrease in the fuel-air ratio and prevent the entry into the unstable combustion region.

When the fuel flow rate command signal indicates an increase in the fuel flow rate, the follow-up of the inlet guide vanes is the same as in the conventional case, but the fuel-air ratio tends to increase and combustion is on the stable side, and operation is continued. There is no problem.

On the other hand, in the conventional example, when the state shown by the broken line in the figure is reached and the fuel flow rate command signal indicates a decrease in the fuel flow rate, the follow-up of the opening control of the inlet guide vanes is delayed, so the fuel flow rate is delayed. The decrease of the air flow rate with respect to the decrease of the air-fuel ratio is slow, and the fuel-air ratio tends to temporarily enter the combustion unstable region.

[0038]

According to the present invention, in a gas turbine having a low NOx combustor, when the fuel flow rate decreases, it is possible to prevent combustion instability of the combustor caused by the difference in the fuel-air ratio, and to stabilize the combustion. The continued operation can be continued.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a gas turbine control method according to an embodiment of the present invention.

FIG. 2 is a comparison diagram of the present invention and a conventional example regarding control of a gas turbine.

FIG. 3 is an explanatory diagram of a conventional gas turbine control method.

[Explanation of symbols]

1 ... Air, 2 ... Air compressor, 3a, 3b ... Fuel, 6 ... Turbine part, 9 ... Fuel flow rate command signal, 30 ... Temporary delay device,
32 ... Adder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minoru Takaba, Inventor Minoru 1-1 1-1, Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Masae Takahashi 5-2, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Incorporated company Hitachi, Ltd. Omika factory (72) Inventor Koji Takahashi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (2)

[Claims] 1. A method for controlling a gas turbine, wherein each flow rate of fuel and air flowing into a combustor is controlled, and an air flow rate to an air compressor is controlled by receiving an inlet guide vane opening command signal. A method of controlling a gas turbine, wherein an inlet guide vane opening close command signal is generated only when the flow rate is reduced, and the air flow rate to the air compressor is controlled in a direction to reduce the flow rate. 2. The decrease in the flow rate of the fuel is detected by using a combination of a temporary delay unit and an adder.
A method for controlling a described gas turbine.