JPH0615824B2 - Gas turbine fuel controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control device for a power generation or mechanical drive gas turbine, and more particularly to a gas turbine fuel control device suitable for preventing misfire of a combustor.

[Conventional technology]

The conventional gas turbine fuel control device is roughly classified into start control, exhaust temperature control, acceleration control, and speed / load control.

The start-up control controls the fuel amount according to a predetermined start-up pattern to automatically accelerate the gas turbine.

The exhaust gas temperature control limits the rate of change of the exhaust gas temperature and the exhaust gas temperature at startup in order to manage the life of the material in the high temperature part.

The acceleration control controls the acceleration at the time of starting.

In the speed / load control, the gas turbine output is controlled by the set speed regulation ratio according to the amount of deviation between the rated speed and the actual gas turbine speed.

The gas turbine fuel control device has a circuit for selecting an optimal signal for the control signal from each control unit that performs the above-mentioned control, and becomes 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 (hereinafter referred to as NO
For the purpose of reducing the concentration (referred to as x), a multi-nozzle type combustor has been used, and a two-stage or multi-stage combustion system has come to be used.

As a control device for a multi-nozzle type combustor, there is, for example, JP-A-61-241425.

[Problems to be Solved by the Invention]

The above-mentioned conventional technique uses a multi-stage combustion system using a multi-nozzle system combustor for the purpose of reducing NOx. However, in the case of the multi-stage combustion system, in order to prevent misfire of the combustor,
It is necessary to secure the minimum fuel flow rate.

However, the conventional fuel control device has a problem in that it does not consider a control method that secures this flow rate according to the atmospheric temperature.

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

[Means for Solving the Problems]

In order to achieve the above object, a fuel control device for a gas turbine according to the present invention is a fuel control device for a gas turbine, which includes an upper and lower limit limiter for limiting upper and lower limits of a fuel flow rate to a multi-stage combustion type combustor of the gas turbine. In the apparatus, temperature measuring means for measuring the atmospheric temperature and outputting an atmospheric temperature signal, a function generator for inputting the atmospheric temperature signal to calculate a lower limit value of the fuel flow rate and outputting a lower limit correction value signal, The signal of the function generator is switched from the start control when the gas turbine load rises to a predetermined value, and is output to the upper and lower limit limiter.

[Action]

In the relationship between the load of the gas turbine, the fuel flow rate, and the 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 when the atmospheric temperature is low, the fuel flow rate is high. Become. The function generator sets the function for the minimum required fuel flow rate so that the combustor does not misfire.

The temperature measuring means measures the atmospheric temperature and outputs an atmospheric temperature signal corresponding to the atmospheric temperature, and the function generator inputs the atmospheric temperature signal and calculates the lower limit value of the fuel flow rate based on the function to calculate the lower limit. A value correction value signal is output, and the switching device ignites the lower limit value correction value signal of the function generator when the gas turbine load rises to a predetermined value, that is, by igniting the combustor after the second stage and NOx of the exhaust gas. When the amount is reduced, it outputs to the upper and lower limit limiter, and the upper and lower limit limiter inputs the lower limit value correction value signal and uses the correction value as the lower limit value to correspond to the increase / decrease load command to the gas turbine.

〔Example〕

An embodiment of the present invention for a two-stage combustion system will be described below with reference to FIGS.

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

During gas turbine startup, a fuel control command output from any one of the startup control unit 1, the exhaust gas temperature control unit 2, and the acceleration control unit 3 via the control signal selection circuit 5 that selects the optimal control signal according to the operating state. At, the gas turbine speeds up.

When the rated speed is reached, the control signal of the speed / load control unit 4 is selected by the control signal selection circuit 5, and the startup of the gas turbine is completed.

After that, the load increase command 6,
It is performed by the load reduction command 7.

When the load is increased, the signal value from the analog memory 8 is increased by the load increase command 6, and is input to the speed / load control unit 4 as a load set value via the upper and lower limit limiter 9, and the fuel control command is issued. Increasing, the turbine load increases. When a certain ratio of the load to the load increase command is reached, the second stage combustor is ignited to reduce the NOx amount of the exhaust gas.

In the case of a load drop, the signal value from the analog memory 8 is reduced by the load reduction command 7, and the signal value is passed through the upper / lower limit limiter 9.
It is input to the speed / load control unit 4 as a load set value, the fuel control command is decreased, and the load of the turbine is decreased.

Here, in order to secure a specified minimum fuel flow rate at which the second-stage combustor does not misfire, the function generator 10 calculates the temperature-corrected combustion flow rate limit value b by the atmospheric temperature signal of the atmospheric thermometer 14 and corrects it. A signal is output, and this correction value signal and the signal a from the signal generator 11 that sets the load limit value for the start / stop process that operates under no-load conditions are input to the switch 12 to start / stop the process. Fuel flow rate limit value b
By inputting as the lower limit value of the upper and lower limiter 9,
The load set value of the upper and lower limiter 9 can be limited so as to secure a specified minimum flow rate.

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

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

It can be seen from FIG. 2 that the higher the atmospheric temperature, the smaller the required fuel flow rate, and the lower the atmospheric temperature, the higher the fuel flow rate under the same load.

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

The curve a shown in FIG. 3 is set by the function generator 10 shown in FIG. 1, and the minimum fuel flow rate limit value is calculated using the curve a, whereby the influence of the change in atmospheric temperature can be corrected.

According to the turbine fuel control apparatus of the first embodiment, the function generator corrects the minimum fuel flow rate at which the combustor does not misfire with respect to the atmospheric temperature and issues the fuel control command, so that misfire of the combustor can be prevented.

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

That is, when reducing the load of the combined cycle power plant, even if the load setting is finally set to be equal to or higher than the minimum fuel flow rate limit value for the gas turbine, transiently when the load is reduced. Since there is a load response delay of the steam turbine due to a response delay of the exhaust heat recovery boiler, in order to compensate for this delay, a command to reduce the load to the gas turbine below the minimum fuel flow rate limit value is issued from the host controller.
May be issued. But even in this case,
According to the fuel limiter for the turbine of the present embodiment, the lower limit limit value is set for the load reduction command.The load set value is not set to the minimum fuel flow rate or less, and the misfire of the combustor does not occur. It can be prevented.

FIG. 4 is a diagram showing a second embodiment of the present invention. The first
In the embodiment, the minimum fuel flow rate is regulated in response to the increase command 6 or the decrease command 7, but in the second embodiment, the minimum fuel flow rate is regulated in response to 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 actually exactly the same as that of the first embodiment. Therefore, the description of the same parts as those in the first embodiment will be omitted, and only the parts having different circuit configurations will be described.

The first difference is that the signal generator 11 for setting the load limit value in the start / stop process as the lower limit set value is directly connected to the upper and lower limit limiter 9. The second difference is that an upper / lower limit limiter 16 is newly provided on the output side of the control signal selection circuit 5, and the signal of the switching device 12 described below is set as the lower limit limit value of the upper / lower limit limiter 16. Is what you are doing. That is, 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 the signal from the signal generator 15 are switched. Enter in 12,
The signal from the switch 15 is input to the upper / lower limit setter 16.

In the case where the turbine load is increased or decreased by the increase command 6 or the decrease command 7, the signal generator 15 is set to zero, and the start / stop process condition is used as the switching condition of the switcher 12 during the start / stop process. In this case, the start / stop signal a of the signal generator 15 is selected. By inputting the output of the switch 12 as the minimum fuel flow rate limit value to the upper / lower limit device 16 that limits the fuel control command, the fuel flow rate command ensures the minimum fuel flow rate.

According to the second embodiment, the minimum fuel flow rate limit value is actually effective only in the speed / load control, so that although the circuit configuration is different, the same fuel limitation as in the first embodiment is eventually performed.

〔The invention's effect〕

According to the present invention, the function generator sets the lower limit value of the upper and lower limit limiter corresponding to the load reduction command to the gas turbine by correcting the minimum fuel flow rate at which the combustor does not misfire according to the atmospheric temperature. Even if the temperature changes, and even if the load reduction command falls below the minimum fuel flow rate, it is possible to prevent misfire of the combustor and reduce NOx in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a control block diagram of the first embodiment, FIG. 2 is a load / fuel flow curve of a gas turbine with atmospheric temperature as a parameter, FIG. 3 is an atmospheric temperature / fuel flow curve for preventing misfire of a combustor, and FIG. FIG. 4 is a control block diagram of the second embodiment. 6 ... Load increase command, 7 ... Load decrease command, 9 ... Upper / lower limit limiter, 10 ... Function generator, 14 ... Atmosphere thermometer.

Claims (1)

[Claims] Claim: What is claimed is: 1. A gas turbine fuel control device comprising an upper and lower limit controller for limiting upper and lower limit values of a fuel flow rate to a multi-stage combustion type combustor of a gas turbine, and measuring an atmospheric temperature to output an atmospheric temperature signal. Temperature measuring means, a function generator that inputs the atmospheric temperature signal, calculates a lower limit value of the fuel flow rate, and outputs a lower limit value correction value signal, and outputs a signal of the function generator to a gas turbine load with a predetermined value. A gas turbine fuel control device, comprising: a switching device that switches from startup control when the value rises to a value and outputs the switching to the upper and lower limiter.