JPH04128517A - Fuel control device for gas turbine - Google Patents

Abstract

PURPOSE:To intend to precisely control NOx and also to exclude danger such as repeating ignition and extinguishment by controlling a fuel flow command independently of a system frequency, in a changeover zone from diffusion combustion to premixed combustion. CONSTITUTION:An F0 operation circuit acts as follows. A signal corresponding to 100% speed from a signal generator 215 is subtracted based on a set value 212, and this is multiplied by gain 214 of a settling rate. The result hereof and a no load rated speed corresponding signal 219 are summed up together, and the result hereof is connected to a switch 216. The switch 216 chooses X1 during the F0 operation circuit governs F0, and chooses X2 in other cases. In this state X1 is chosen and connected to a low value choosing circuit 210 via an analog memory 217. Then start control, acceleration control, temperature control, and governor control are all brought in a waiting state, and as the result, F0 is controlled independently of a system frequency. Changeover conditions are chosen by switches 206, 216 to arbitrarily decide in which zone the F0 operation circuit is preferential to the governor control system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas turbine control method, and particularly to a gas turbine that can suppress the generation of nitrogen oxides (hereinafter referred to as NOx), which are air pollutants. This invention relates to a fuel control device.

[Conventional technology]

The basic configuration of a fuel control device aimed at reducing NOx is described in Japanese Patent Application Laid-Open No. 61-258929, but it does not mention the removal of the influence of system frequency to ensure reliable and smooth fuel switching. It wasn't.

[Problem to be solved by the invention]

Figure 1 shows the main equipment configuration of a gas turbine power plant. Air compressor 1. Combustor 2. Electric power generated in a gas turbine power plant composed of a turbine 32 and a generator 4 is supplied to the grid via a breaker 5. This power control is performed by a fuel adjustment valve 6. Next, the relationship between the ratio of fuel and air supplied to the combustor (fuel-air ratio) and the amount of NOx generated is determined as follows.
As shown in the figure. In diffusive combustion, when fuel is injected, even if there is a lot of air around it, the air necessary for stable combustion is used, and the remaining air is used for dilution. Diffusion combustion allows stable combustion even at low fuel-air ratios, but generates a lot of NOx. In premix combustion, the fuel and air are mixed in advance, so the degree of mixing of fuel and air is improved, and the fuel-air ratio is leaner. This makes it possible to reduce NOx. In an actual combustor, diffusion combustion with high combustion stability is used in the low fuel-air ratio region, and premixing that can reduce NOx is added in the high fuel-air ratio region, and the ratio is changed from the low fuel-air ratio region to the high fuel-air ratio region. Until NO
Keep the x amount below a certain value. FIG. 3 shows such a control method using the fuel/air ratio as a parameter.

Here, Fl is a fuel that performs diffusion combustion 2, and F2 is a fuel that performs premix combustion. The amount of NOx generated increases as the fuel-air ratio of diffusion combustion increases, but by premixing a portion of the fuel, the NOx value in a high fuel-air ratio region can be lowered.

As described above, in the low NOx combustor, premix combustion is added to the diffusion combustion, whereas conventionally only diffusion combustion is used, and two fuel systems corresponding to these are required.

In other words, for the purpose of load control, the total fuel command value (hereinafter abbreviated as Fo) is used to perform premix combustion with a command to the fuel system that performs diffusion combustion (hereinafter abbreviated as F) for the purpose of NOx control. It is necessary to divide the command into another fuel system command (hereinafter abbreviated as F2). In this division, it is important not to cause load fluctuations, to accurately determine the switching point from diffusion combustion to premix combustion, and to manage the amount of NOx generated within a limit value.

Generally, it is difficult to accurately measure the air flow rate of a gas turbine.
Dividing the fuel command value by using the fuel-air ratio as a parameter as shown in FIG. 3 is not very practical. For this reason, a fuel pressure regulating valve is installed in front of the fuel regulating valve and the fuel black regulating valve in each of the diffusive combustion fuel system and the 'f-mixed combustion fuel system, and is conventionally used as a load control signal for the generator. The fuel command signal that had been previously used was modified using parameters related to the gas turbine air amount.
The fuel command value for the diffusion combustion fuel system is determined based on the niobium t, and the difference between the previous fuel command signal and this fuel command value is used as the fuel command for the premix combustion fuel system.

Figure 8 shows the division of fuel command when atmospheric temperature is used as a parameter related to gas turbine air flow number J. The gas turbine air flow rate is determined by the gas turbine speed and atmospheric temperature, but switching between F+ and F2 is necessary for gas turbine power generation. This will be carried out after the aircraft has been annexed. Therefore, the gas turbine air flow rate at the time of switching is affected only by the atmospheric temperature; if the atmospheric temperature decreases, the air flow rate increases, and conversely, if the popular temperature increases, the air flow rate decreases. ■ indicates this relationship, and the popular temperature of 15°C is used as the standard, and the air flow rate at this time is standardized and expressed as "1". Note that the reference temperature may be any degree Celsius. (2) is for modifying the total fuel command value (governor control signal).

The calculation result of ■ is 273℃ + x℃, and if the atmospheric temperature rises above 15℃, Fo' becomes F
If it becomes smaller than o, or vice versa, Fo' becomes F.

Become bigger.

In (2), the fuel command is distributed to Fl and F2 based on Fo'. Here, A and B are switching points at an atmospheric temperature of 15°C. If the atmospheric temperature rises above 15℃, the switching point is YA.
, move to point YB, ie.

Since Y is smaller than 1, it will be a smaller value than the switching point when the atmospheric temperature is 15° C., and conversely, if the atmospheric temperature is several times lower, it will be a larger value. This is equivalent to switching between Fl and F2 depending on the fuel/air ratio.

From the above, it is not necessary to use the gas turbine air flow rate, which has a measurement error of ±10%, for switching between Fl and F2, and the amount of NOx generated at the time of switching can be managed with high accuracy.

In this case, the total fuel flow command value Fo is determined by the load control device, which is the control system at -F, or by the governor control operation based on the set value given by the operator's operation. to be influenced. As a result, it becomes difficult to identify the switching point, making it impossible to expect accurate NOx control, and there is a possibility that Fo will increase or decrease near the switching point, causing F2 to repeatedly ignite and extinguish.

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for eliminating the influence of system frequency in a fuel switching zone in order to prevent the above-mentioned problems.

[Means to solve the problem]

The above object is achieved by providing the Fo calculation circuit i3 which is not affected by the system frequency and placing the 5 governor control circuit in a standby state.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, FIG. 4 shows the fuel system of the present invention.

The fuel injected into the diffusion combustion area is shown as Fl, and the fuel injected into the premix combustion area is shown as F2. Fl is connected from the fuel supply port to the pressure regulating valve (PCVI) 103° and the pressure detector 105.
It is ejected from a nozzle via a flow rate control valve (FCVI) 104.

The fuel system of F2 is also the same as Fl.

FIG. 5 shows a control system for calculating the fuel flow rate command Fo. For explanations of startup control, acceleration control, and @degree control, see the known examples (
Since it is described in Japanese Patent Publication No. 46-18203), it will be omitted here. Furthermore, there are many known examples of the content of speed regulating control, and since it is not directly related to the present invention, a description thereof will be omitted.

Now, from gas turbine startup to merging, the startup control is controlled, and from merging to the fuel switching point (from diffusion combustion to premix combustion), the Fo calculation circuit, which is not affected by the system frequency, controls RFo.

The analog memory 202 is a setting I which sets the fuel flow rate in response to an increase or decrease command from a load control device or an operator.
212 is a governor control circuit and F;

It is connected to both of the arithmetic circuits, but immediately after the combination, the switch 206
selects the x2 side, a suppression bias is added to the governor control circuit, and the governor control circuit is in a standby state for the Fo calculation circuit.

The Fo calculation circuit operates as follows.

The 100% speed equivalent signal from the signal generator 215 is subtracted from the set value 212, and this is multiplied by the adjustment rate gain 2]4. This result is added to the no-load rated speed equivalent signal 219, and this result is connected to the switch 216. Switch 1!21
In 6, the Fo calculation circuit is F.

Select [X] while controlling, otherwise select x2
Select. In this state, xl is selected, and the signal is sent to the low value selection circuit (LVG) 21.0 via the analog memory 217.
connected to. In this state, startup control, acceleration control, temperature control, and governor control are all on standby (that is, the output of analog memory 217 is the closest value, and this controls Fo), and as a result, Fo is the system frequency. controlled regardless of the

By selecting the switching conditions of the switchers 206 and 216, it is possible to arbitrarily determine in which region the Fo calculation circuit is given priority over the governor control system.

FIG. 6 shows a block diagram of the fuel l1 control valve.

The atmospheric temperature detected by the temperature sensor 12 is connected to a function generator 122, and the output is F from this output.

is corrected by the multiplier 124. The function generator 125 determines the fuel ratio of Fl based on the modified fuel demand value Fo'. The thinking up to this point is supplemented with Figure 8.

A multiplier 126 calculates a fuel command of F] from the fuel ratio of Fl and Fo. F1 calculated by adder/subtracter 131
The electro-hydraulic converter 133 is operated according to the deviation between the fuel command and the fuel amount S lung apex opening 132 of Fl, thereby controlling the fuel iIl
! The valve 1 controls 114 nodes of the lung leaflet to control Fl, that is, the fuel flow rate to the diffusion combustion system.

The difference between the total fuel flow command Fo and the fuel command Fl is calculated by an adder/subtractor 127, thereby controlling F2, that is, the fuel flow rate to the premix combustion system.

Next, FIG. 7 shows a control block diagram of the fuel pressure regulating valve.

The pressure regulating valve (pevl) 103 controls the FCVl afterpressure in proportion to the gas turbine rotation speed in order to increase the opening degree of the FCV1 at startup and improve controllability. N is the gas turbine rotation speed, a proportional calculation is performed by the calculator 141, and the pressure set value is determined by adding a bias. This set value is compared with the actual pressure 105 after FCV l, a proportional integral calculation is performed by the calculator 144, and the servo valve driver 145 controls PCVI.

Since the pressure regulating valve (FCV2) controls the FCV2 after the gas turbine reaches its rated rotational speed, constant value control may be used. The pressure setting value is set by the setting device 1.51, matches the actual pressure 109 of the FCV 2, performs proportional integral calculation by the calculator] 53, and sets the pressure by the servo valve driver 154.
Control CV2.

〔Effect of the invention〕

According to the present invention, in the switching zone from diffusion combustion to premix combustion, the fuel flow rate command Fo can be controlled independently of the system frequency, so accurate NOx control can be expected and at the same time
The danger of repeated ignition and extinguishing in step 2 can be eliminated.

[Brief explanation of the drawing]

Figure 1 is a diagram of the main equipment configuration of a gas turbine power plant, Figure 2 is an explanatory diagram showing the fuel-air ratio and amount of NOx generated, Figure 3 is an explanatory diagram showing an overview of control, and Figure 4 is a fuel system diagram. , FIG. 5 is a control block diagram showing one embodiment of the present invention, FIGS. 6 and 7 are control block diagrams for explaining the operation, and FIG. 8 is a diagram for explaining the operation. Figure 2! Figure 5 Figure 7 CV2 Figure 8

Claims (1)

[Claims] 1. For the purpose of reducing NOx in exhaust gas, a fuel pressure regulating valve and a fuel flow regulating valve are installed in each of the two fuel control systems, and the control signal for the first stage fuel flow regulating valve is based on the total fuel flow command value. In a gas turbine fuel control system, the control signal for the second stage fuel flow control valve is calculated as the difference between the total fuel flow command value and the control signal for the first stage fuel flow control valve. A gas turbine fuel control device comprising means for controlling a fuel flow rate command value regardless of system frequency.