JPH01285627A - Gas turbine fuel control device - Google Patents

Abstract

PURPOSE:To prevent failure in ignition of a combustor by a method wherein, in a device which has an upper lower limit limiter to limit the upper and the lower limit value of a flow rate of fuel to a combustor, a function generator is provided for computing the lower limit value of a flow rate of fuel according to an atmospheric temperature and outputting a lower limit value correction value signal. CONSTITUTION:During the starting of a gas turbine, from either of a starting control part 1, an exhaust gas temperature control part 2, and an acceleration control part 3, an optimum control signal is selected by a selection circuit 5 according to a running state to output it, and the rotation speed of the gas turbine is increased. When the speed is increased to a rated value, a control signal from a speed and addition control part 4 is selected by the selection circuit 5 to complete the starting of the gas turbine. Thereafter, the rise and fall of a turbine load are effected by means of a load increase command and a load decrease command 7. In this case, a function generator 10 to input an output signal from an atmospheric temperature gauge 14, where a temperature-corrected fuel flow rate limit value (b) is calculated. The calculating result is inputted as a lower limit value to an upper lower limit limiter 9 on starting/ stop process conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control device for a gas turbine for power generation or for mechanical beating, and particularly to a gas turbine fuel control device suitable for preventing misfires in a combustor.

[Conventional technology]

The control of conventional gas turbine fuel control devices can be roughly divided into startup control, exhaust temperature control, acceleration control, and speed/load control.

Start-up control controls the amount of fuel according to a defined start-up pattern and automatically speeds up the gas turbine.

Exhaust temperature control limits the exhaust temperature and the rate of change in the exhaust temperature at startup in order to manage the life of the material in the high temperature section.

Acceleration control controls acceleration at startup.

Speed/load control is controlled by a set speed regulation rate depending on the amount of deviation between the rated speed and the actual gas turbine speed.
Controls gas turbine output.

The gas turbine fuel control device has a circuit that selects an optimal control signal from each control unit that performs the control according to the operating state, and serves as a control system that outputs a fuel control command through the circuit. There is.

On the other hand, in recent years, gas turbine exhaust nitrogen oxides (NO
x) for the purpose of reducing the concentration.

Multi-nozzle combustors have been used, and two-stage or multi-stage combustion systems have come into use.

An example of a related control device for a multi-nozzle type combustor is disclosed in Japanese Patent Application Laid-Open No. 61-241425.

[Problem to be solved by the invention]

In the above conventional technology, a multi-stage combustion method using a multi-nozzle combustor is used for the purpose of reducing NOx.
It is necessary to ensure a minimum fuel flow rate.

However, conventional fuel control devices have a problem in that they do not take into consideration a control method for ensuring this flow rate in response to atmospheric temperature.

An object of the present invention is to provide a gas turbine fuel control device that prevents misfires in a combustor using a multi-stage combustion method.

[Means to solve the problem]

In order to achieve the above object, the gas turbine fuel control device of the present invention includes an upper and lower limit limiter that limits the upper and lower limits of the fuel flow rate to the combustor of the gas turbine. temperature measuring means for measuring temperature and outputting an atmospheric temperature signal; and a function generator for inputting the atmospheric temperature signal, calculating a correction value for the lower limit value of the fuel flow rate, and outputting a lower limit value correction value signal to the upper and lower limit limiter. It is equipped with a container.

[Effect]

Regarding the relationship between the gas turbine load, fuel flow rate, and atmospheric temperature, if the load is the same, the fuel flow rate is expressed as a function of the atmospheric temperature; when the atmospheric temperature is high, the fuel flow rate is low, and conversely, when the atmospheric temperature is low, the fuel flow rate is high. Become.

The function generator sets the function for the minimum fuel flow rate required to prevent the combustor from misfiring.

The temperature measuring means measures the atmospheric temperature and outputs an atmospheric temperature signal corresponding to the atmospheric temperature, and the function generator receives the atmospheric temperature signal and calculates the lower limit value of the fuel flow rate based on the function. The upper/lower limit limiter outputs a value correction value signal, inputs the lower limit value correction value signal, and uses the correction value as a lower limit value to respond to a load increase/decrease command to the gas turbine.

〔Example〕

Embodiments of the present invention regarding a two-stage combustion system will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows a fuel control block diagram of a gas turbine as a first embodiment.

During startup of the gas turbine, the startup control unit 1. Exhaust temperature control section 2
．． With a fuel control command outputted from one of the acceleration control units 3 via a control signal selection circuit 5 that selects an optimal control signal depending on the operating state.

The gas turbine speeds up.

When the rated speed is reached, the speed/load control section 40 control signal is selected by the control signal selection circuit 5.

Startup of the gas turbine is completed.

From then on, the load increase or decrease of the turbine load is controlled by load increase command 6.
This is done in response to the load reduction command 7.

In the case of a load increase, the signal value from the analog memory 8 is increased by the load increase command 6, and is inputted to the speed/load control section 4 as a load setting value via the upper and lower limit limiter 9, and the fuel control command is issued. Increasingly, the load on the turbine rises. When the load reaches a predetermined ratio of the load increase command, the second stage combustor is ignited to reduce the amount of NOx in the exhaust gas.

In the case of a load drop, the signal value from the analog memory 8 decreases according to the load range command 7, and passes through the upper and lower limit limiter 9.
This is input as a load setting value to the speed/load control unit 4, and the fuel control command decreases, causing the turbine load to drop.

Here, in order to secure a prescribed minimum fuel flow rate that will prevent the second stage combustor from misfiring, the function generator 10 calculates a temperature-corrected combustion flow rate limit value based on the atmospheric temperature signal from the atmospheric thermometer 14, and calculates a correction value. output a signal.

This correction value signal and the signal a from the signal generator 11 that sets the load limit value for the start/stop process of operation under no-load conditions are input to the switch 12, and the signal is switched according to the start/stop process conditions. By inputting the fuel flow rate limit value as the lower limit value of the upper and lower limit limiter 9, the load setting value of the upper and lower limit limiter 9 can be limited so as to ensure a specified minimum flow rate.

Further, the signal from the signal generator 13 for setting the load upper limit value is inputted as the upper limit setting value of the upper and lower limit limiter 9 to limit the upper limit of the load setting value.

FIG. 2 shows the relationship between gas turbine load and fuel flow rate using atmospheric temperature as a parameter.

According to FIG. 2, it can be seen that for the same load, the higher the atmospheric temperature, the smaller the required fuel flow rate, and the lower the atmospheric temperature, the larger the required fuel flow rate.

FIG. 3 shows the relationship between the atmospheric temperature and the fuel flow rate, with the minimum load 20 to prevent the second-stage combustor from misfiring shown in FIG. 2 as a parameter.

The curve a shown in FIG. 3 is fixed at y by the function generator 10 shown in FIG. can.

According to the turbine fuel control device of the first embodiment, the function generator corrects the lowest fuel flow rate at which the combustor will not misfire, relative to the atmospheric temperature, and issues a fuel control command, so that misfires in the combustor can be prevented.

When the turbine fuel control device of the first embodiment is applied to a combined cycle power plant consisting of a gas turbine, a steam turbine, and an exhaust heat recovery boiler, the following effects can be obtained.

In other words, when reducing the load of a combined cycle power plant, even if the load setting is ultimately set to exceed the minimum fuel flow limit value for the gas turbine, during the load reduction, transient There is a delay in the load response of the steam turbine due to a delay in the response of the exhaust heat recovery boiler, so in order to compensate for this delay, the host controller issues a load reduction command to the gas turbine to bring it below the minimum fuel flow limit value.
It may be emitted. However, even in such cases,
According to the turbine fuel control device of this embodiment.

Since a lower limit value is set for the load reduction command, the load setting value will not be set below the minimum fuel flow rate.
Misfires in the combustor can be prevented.

FIG. 4 is a diagram showing a second embodiment of the present invention.

In the first embodiment, the minimum fuel flow rate is regulated for the increase command 6 or the decrease command 7, but in the second embodiment, the minimum fuel flow rate is regulated for the fuel control command from the control signal selection circuit 5. . Therefore, although the circuit configuration is slightly different, the regulation of the minimum fuel flow rate is practically the same as the first embodiment. Therefore, a description of the same parts as in the first embodiment will be omitted, and only the different parts of the circuit configuration will be described.

The first difference is that a signal generator 11 is directly connected to the upper/lower limit limiter 9 for setting a load limit value for the start/stop process as its lower limit set value. The second difference is that a new upper/lower limit limiter 16 is provided on the output side of the control (number selection circuit 5), and the lower limit value of the upper/lower limit limiter 16 is the signal of the switch 12, which will be explained next. In other words, the function generator 10 calculates a temperature-corrected fuel flow rate limit value based on the atmospheric temperature signal from the atmospheric thermometer 14 and outputs a correction value signal, and the correction value signal and signal A signal from the generator 15 is input to the switch 12, and a signal No. 43 from the switch ri15 is input to the upper and lower limit setter 16.

In the case of an increase or decrease in the load of the turbine due to the increase command 6 or decrease command 7, the settings of the signal generator 15 are as follows.

The condition of the start/stop process is used as the switching condition of the switch 12, and when the start/stop process is in progress, the signal generator 15 is set to zero.
Select start/stop signal a. By inputting the output of this switch 12 as the minimum fuel flow rate limit value to the upper/lower limiter 16 that limits the fuel control command, the fuel flow command ensures the minimum fuel flow rate.

According to the second embodiment, the minimum fuel flow rate limit value is actually effective only in speed/load control.

Although the circuit configuration is different, the fuel restriction is ultimately performed in exactly the same way as in the first embodiment.

〔Effect of the invention〕

According to the present invention, since the function generator corrects the minimum fuel flow rate at which the combustor does not misfire according to the atmospheric temperature and sets the lower limit value of the upper and lower limit limiter corresponding to the load range command to the gas turbine, Even if the temperature changes or the load range command falls below the minimum fuel flow rate, misfires in the combustor can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of the first embodiment, Fig. 2 is a gas turbine load/fuel flow curve with atmospheric temperature as a parameter, Fig. 3 is an atmospheric temperature/fuel flow curve for preventing combustor misfires, FIG. 4 is a control block diagram of the second embodiment. 6...Load increase command, 7...Load range command. 9... Upper and lower limit limiter, 10... Function generator, 1
4... Atmospheric thermometer.

Claims (1)

[Claims] 1. In a gas turbine fuel control device equipped with an upper and lower limit limiter that limits the upper and lower limits of a fuel flow rate to a combustor of a gas turbine, a temperature measuring means that measures atmospheric temperature and outputs an atmospheric temperature signal; A fuel control device for a gas turbine, comprising: a function generator that inputs an atmospheric temperature signal, calculates a lower limit value of the fuel flow rate, and outputs a lower limit correction value signal to the upper and lower limit limiter.