JPS61258929A - Fuel controller for gas turbine - Google Patents

Abstract

PURPOSE:To restrain a load variation from occurring, by installing a fuel pressure regulating valve and a fuel flow control valve each in each branch pipe line, in case of a two-stage combustion system combining both premix and diffuse combustion systems in one. CONSTITUTION:Both first and second branch pipe lines 20 and 30 branched off from a basic fuel pipe line 10 each are set up in both first- and second-stage combustion chambers formed in a head part of a fueler 2 and at the afterflow side. In the first branch pipe line 20, there are provided with a first orifice 101, a first pressure regulating valve 103 and a first flow control valve 104. In the second branch pipe line 30, there are provided with a second orifice 106, a second pressure regulating valve 108 and a second flow control valve 109. With this constitution, a variation in fuel feed after selection from diffuse combustion to premix combustion is prevented from occurring, thus a load variation is restrainable.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a fuel control device for a gas turbine, and in particular to a gas turbine fuel that can suppress the generation of nitrogen oxides (hereinafter referred to as NOx), etc., which are air pollutants. Regarding a control device.

[Background of the invention]

The ninth step to reducing NOx generated in gas turbine combustors is to achieve uniform low-temperature combustion by equalizing the mixture of fuel and air during the combustion process, or by shortening the IM of the generation time of FX NOx. It is necessary to do this.

As the ninth means to establish this combustion mode, there are two methods: a method in which fuel and air are mixed in advance and supplied to the combustor (premix combustion method), and a method in which fuel is diffusely combusted in the combustor (diffusion combustion method). A method having a two-stage combustion structure in which combustion is performed in combination is known (see t# Publication No. 57-41524).

Here, the reason for using the two-stage combustion structure will be explained below.

First, Figure 5 shows the main equipment configuration of a gas turbine power plant. Air compressor 1, combustor 2. The power generated by the gas turbine power plant, which is composed of a turbine 3 and a generator 4, is supplied to the power transmission system through a circuit breaker 5't-. Power control in this gas turbine power plant is performed by a fuel regulating valve 6.

Next, FIG. 6 shows the relationship between the ratio of fuel and air (air-fuel ratio) supplied to the combustor 2 and the amount of NOx generated.

In normal diffusion combustion, even if there is a lot of air surrounding the injected fuel, only enough air is used for stable combustion, and the remaining air is used for dilution. Although this diffusion combustion allows stable combustion even at low fuel/air ratios, it generates a lot of NOx. On the other hand, in premix combustion, fuel is mixed with air in advance, so the degree of mixing between fuel and air is improved, the air-fuel ratio can be made lean, and NOx can be reduced.

Therefore, in an actual combustor, we use diffusion combustion, which is highly stable in the low air-fuel ratio region, and add premix combustion, which can reduce NOx in the high air-fuel ratio region, to reduce NOx from the low air-fuel ratio region to the high air-fuel ratio region.
A method is adopted in which the amount of x is suppressed to a certain value or less. FIG. 7 shows such a control system using the air-fuel ratio as a parameter.

In FIG. 7(b), sFl represents a change in fuel for performing diffusion combustion, and F2fl represents a change in fuel for performing premix combustion. As can be seen from FIGS. 7(a) and 7(b), the amount of NOx generated increases as the air-fuel ratio increases due to diffusion combustion in the low air-fuel ratio region. Therefore,
At a critical point in the amount of NOx to be regulated, a portion of the supplied fuel is switched to premix combustion. The ratio is set to about 1/2 in FIG. 7(a). By this switching, as shown in FIG. 7(b), the amount of NOx generated in the high air-fuel ratio region can be lowered to below the regulation value.

By the way, in such a combustor with a two-stage combustion structure for reducing NOx, the combustion chamber is divided into two, the front stage side and the rear stage side, and the main fuel pipe is branched into two to connect each combustion chamber. It is configured to be installed in a room. In this case, conventionally, one fuel flow rate adjustment valve was provided in the main fuel pipe, and this fuel flow rate adjustment valve controlled the fuel and therefore controlled the power generation 4i. Ninth, 'When the second stage (latter stage) fuel is injected, the opening area for the second stage fuel nozzle increases, which affects the fuel flow rate and, as a result, causes load fluctuations to the power system. It's a thing.

Note that the above-mentioned known technology is a NOx reduction technology for a single combustor, and the fuel system and its specific control method when installed in a power plant and performs load control as part of the power system have not been studied. do not have.

[Purpose of the invention]

An object of the present invention is to provide a fuel control device that does not cause load fluctuations to the electric power system in a gas turbine that uses two combustion methods, diffusion combustion and premix combustion, and has a secondary combustor. .

[Summary of the invention]

To achieve the above object, a first invention provides a fuel control device for branching a main fuel pipe into two systems and supplying fuel to each combustion chamber of a combustor of a gas turbine having a two-stage combustion structure. By independently providing a fuel pressure regulating valve and a fuel flow regulating valve in each of the branch pipes, fluctuations in fuel supply can be prevented when transitioning from diffusion combustion to premix combustion and thereafter. This is what I did.

A second invention provides a fuel control device that branches a main fuel pipe into two systems to supply fuel to each combustion chamber of a gas turbine having a two-stage combustion structure, in which a fuel pressure regulating valve is provided in the main fuel pipe. By providing a fuel flow rate regulating valve and a fuel flow rate regulating valve on either one of the branch pipes, it is possible to prevent fluctuations in fuel supply due to input of premix combustion into diffusion combustion.

[Embodiments of the invention]

Next, embodiments of each invention of the present application will be described based on the drawings.

First Invention First, FIG. 1 shows an embodiment of the first invention. As shown in FIG. 1, a first stage combustion chamber is provided at the head of the combustor 2, and a second stage combustion chamber is formed on the downstream side thereof. Although not shown, the first. Each second combustion chamber is provided with a fuel injection nozzle.

Then, each fuel injection nozzle has 1. A second branch pipe 20.30 is provided.

The first branch pipe 20 has a first orifice 10 on the upstream side.
1 and a first flow rate oscillator 102, a first pressure regulating valve 103, a first pressure oscillator 105, and a first flow rate regulating valve 104.

Similarly, the second branch pipe 30 includes a flowmeter K, a second orifice 106 and a second flow oscillator 107 on the upstream side, a second pressure regulating valve 108.1!2 pressure oscillator 109, and a second flow regulating valve. 110 are provided respectively.

In the above configuration, the fuel flow rate (total fuel value) fed from the main fuel pipe 10 is set to F(1% first branch pipe 2
0 and is injected from the injection nozzle of the first stage combustion chamber (hereinafter referred to as the first stage fuel value). The fuel flow rate for premix combustion (hereinafter referred to as the second stage fuel value) is F
, denoted by .

In such a system, there is only one so-called governor signal, which is the total required value of the fuel amount, so the governor signal is set to the fuel value F! on the first stage side. and the fuel value F on the second stage side! need to be allocated to. FIG. 2 shows a control block diagram of the fuel system.

In Figure 2, the total fuel demand value F・
The calculation element 130 calculates the air-fuel ratio based on the measured air amount. The function is f4 (indicated by →. From the obtained air-fuel ratio, the calculation element 121 calculates the second stage fuel value F.
1 and the first stage fuel value F ratio (Ft /F*)'. Here, the air-fuel ratio is optimal for calculating the sF+/F snow, but if the accuracy of the exhaust NOx amount is not a concern, the power generation output can be used instead of the air-fuel ratio.

This function is the same as the fuel ratio in FIG. Next, the calculation element 122 calculates only the second stage fuel value FB from the total fuel value Fo and F't/Ft.

This calculated second stage fuel value FB is the second flow rate adjustment increase XX.
This becomes a fuel amount request signal for O. Here, the calculation element 122
The arithmetic expression in is expressed by equation a).

Next, the calculation element 123 calculates the fuel amount request signal Fs for the first flow rate regulating valve 104 based on the total fuel value Fo and the first stage fuel value F3 calculated above using the following formula.

FB = Fo Pa "" (2) These fuel requirement values F1. F meaning is addition operator 124.127
, the actual flow rates F, , F! are detected by the respective flow rate oscillators 102 and 107. compared to The obtained deviation value is calculated by proportional [F]-integral α) by calculating units 125 and 128, and the control signal thereof is given to servo valve drivers 126 and 129.

The first operation signal is activated by the operation signal. Second fuel adjustment valve 104°1
10 is controlled.

The first pressure regulating valve 103 is the first flow regulating valve 104 at startup.
Ninth, increase the valve opening to improve controllability.The first flow rate is proportional to the gas turbine rotation speed! ! li! Valve adjustment 10
4. It performs afterpressure control. N indicates the actual rotational speed of the gas turbine, a proportional calculation is performed by the calculating unit 141 (K is the proportional gain), and a bias is added by the addition element 142, and the result is set as the pressure setting value. This set value is the first flow rate regulating valve 1.
The adding element 143 compares the actual pressure P21 detected by the pressure oscillator 105 after 04. The obtained deviation value is subjected to a proportional integral calculation by the calculator 144, and the obtained control signal is converted into an operation signal by the servo valve driver 145 to control the first pressure regulating valve 103.

The second pressure regulating valve may be a constant value control for controlling the second flow regulating valve 110 after the gas turbine reaches the rated rotation speed. The pressure set value is set by the setter 151 (8G is a constant), detected by the pressure oscillator 109 of the second pressure regulating valve 108, and compared with the actual pressure Ps3 by the addition element 152. The obtained deviation value is subjected to proportional integral calculation by the calculating unit 153.

The control signal is converted into an operation signal by the servo valve driver 154 to control the second pressure regulating valve 108t.

According to this embodiment, the first pressure regulating valve 103. Since the after pressure of the second pressure regulating valve 108 is controlled respectively, the first stage fuel value F1s second stage fuel value F! can be controlled independently,
1st stage fuel value during load operation! The second
Since the F1 flow rate is not affected by the increase in the nozzle opening area of the stage combustion chamber, it is possible to reduce NOx without causing load fluctuations.

1. Second invention - Next, an embodiment of the second invention is shown in FIG. In FIG. 3, combustor 2, combustor 1. The second stage combustion chamber, the arrangement of each injection nozzle, and the configuration of the fuel piping are the same, and the same parts are given the same reference numerals and detailed explanations thereof will be omitted.

The main fuel pipe 10 includes a first orifice 20 from the upstream side.
1 and a first flow oscillator 205, a pressure regulating valve 202, a pressure excavator 206, and a first flow regulating valve 203 are provided.

The second branch pipe 30 includes a second orifice 204 and @
Flow meter consisting of two flow rate oscillators 207, the second flow is controlled by a regulating valve 2
08 is provided. In addition, these @2 orifice 2
04, the second flow rate oscillator 207 and the second flow rate regulating valve 208 may be provided in the first branch pipe 20. Fo is the total fuel value sFt is the first stage fuel value, F2 is the second stage fuel value,
The first stage fuel value F1 is for diffusion combustion, and the second stage fuel value F2 is for premix combustion, which is the same as in the embodiment shown in FIG.

FIG. 4 shows a control block diagram of this fuel control system. In this embodiment, the first flow regulating valve 203 controls the total fuel flow fFo, and the second flow regulating valve 208 controls the first stage fuel value F1 and the first stage fuel value F! control fuel splitting.

First, control of the second flow rate regulating valve 208 will be explained.

The calculation element (function gs(x)) 221 is the actual total fuel F
The air-fuel ratio is calculated from o and the actual air flow rate A0.

Next, the calculation element (function g1 (→) 220 calculates the ratio (Fl/Ft) between the first stage fuel value F1 and the first stage fuel value Fz from the calculated air-fuel ratio. Alternatively, the generator output can be used. This function is
It is the same as the fuel ratio in the figure.

The calculation element (function gz'') 222 calculates only the second stage fuel value F2 from the actual total fuel Fo and F'l/F.
z (→ is expressed by the above-mentioned equation (2). The second stage fuel flow value F2 is compared with the actual fuel flow rate F2 in the addition element 223, and is subjected to proportional and integral calculations by the calculator 224, and the servo valve driver 225 is The second flow rate regulating valve 208 is controlled via the second flow rate regulating valve 208.

As a result, since Ft = Fo Fz, the second stage fuel value Fl is automatically determined by controlling the total fuel 1INF o @second stage fuel value F2.

In the fuel system of this embodiment, when the second flow rate adjustment valve 208 opens during load operation, the afterpressure of the first flow rate adjustment valve 208 increases as the nozzle opening area increases by the second stage fuel value F2. Go down. The total flow rate Fo is determined by the back pressure of the pressure regulating valve 202, the back pressure of the first flow rate control valve 203, and its opening degree.When the back pressure of the first flow rate control valve 203 decreases, the total flow rate Fo increases and the load voltage It causes To prevent this, the pressure regulating valve 202 makes a correction based on the actual fuel flow rate F2 of the second flow regulating valve 203. Note that this correction can also be made by adjusting the opening degree of the second flow rate regulating valve 203 instead of the actual fuel flow rate F2.

The pressure regulating valve 202 is controlled as follows. The calculation element 226 performs a proportional calculation (K
l-1: Proportional gain), and add a calculation element (function g
3(x)) 228, the set value of the rear pressure of the pressure regulating valve 202 is obtained by adding correction based on the actual fuel flow tF1 described above. Then, this set value and the actual pressure P2 are compared by the addition element 230. The calculation unit 231 performs a proportional integral calculation on the deviation value, and the pressure regulating valve 202 is controlled via the servo valve driver 232.

In order to control the total flow rate Fo, the first flow rate regulating valve 203 may use a conventional governor control signal and is controlled by a servo valve driver 253.

According to this embodiment, the second pressure regulating valve 108 on the front side of the second flow regulating valve (FIG. 1), which was necessary in the first embodiment, is unnecessary. Furthermore, the conventional governor control signal can be used as is. Moreover, load fluctuations during second-stage fuel injection can be suppressed.

[Effects of the Invention] According to the present invention, there is an effect of reducing NO'x in exhaust gas without worrying about load fluctuation.

[Brief explanation of the drawing]

Fig. 1 is a fuel system diagram of an embodiment of the first invention, Fig. 2 is a control block diagram of an embodiment of the first invention, Fig. 3 is a fuel system diagram of an embodiment of the second invention, and Fig. 4 is a control block diagram of the embodiment of the second invention, FIG. 5 is a main equipment configuration diagram of the gas turbine power plant, and FIG. 6 is an explanatory diagram showing the air-fuel ratio and the amount of NOx generated.
FIG. 7 is an explanatory diagram showing an outline of control. DESCRIPTION OF SYMBOLS 1... Air compressor, 2... Combustor, 3... Turbine, 4... Generator, 5... Circuit breaker, 6... Fuel adjustment valve, 101... First orifice , 102...first
Flow rate transmitter, 103...first pressure regulating valve, 104...
・First flow rate adjustment valve, 105...first pressure transmitter, 10
6... Second orifice, 107... Second flow rate transmitter, 108... Second pressure regulating valve, 109... Second pressure transmitter, 110... Second flow rate regulating valve, 121. ...Arithmetic element, 122...Arithmetic element, 123...Arithmetic element, 124...Addition element. 125... Proportional integral calculator, 126... Servo valve driver, 127... Addition point, 128... Proportional integral calculator. 129... Servo valve driver, 130... Arithmetic element, 141... Proportional calculator, 142... Addition element, 1
43... Addition element, 144... Proportional integral operation, 14
5... Servo valve driver, 151... Setting device, 15
2... Addition element, 153... Proportional-integral calculator, 15
4... Servo valve driver, 201... First orifice, 202... Pressure regulating valve, 203... First flow regulating valve, 204... Second orifice, 205... Second
Flow rate transmitter, 206...Second pressure transmitter, 207...
・Second flow rate transmitter, Tate 220...Calculation element, 221・
... calculation element, 222 ... calculation element, 223 ... addition element, 224 ... proportional integral calculation unit, 225 ... servo valve driver, 226 ... proportional calculation element, 227.
... addition element, 228 ... calculation element, 229 ... addition element, 230 ... addition element, 231 ... proportional integral calculation element, 232 ... servo valve driver, 233 ...
・Servo valve driver.

Claims (1)

[Scope of Claims] 1. In a fuel control device that branches a main fuel pipe into two systems and supplies fuel to each combustion chamber of a combustor of a gas turbine having a two-stage combustion structure, A fuel control device for a gas turbine, characterized in that a fuel pressure regulating valve and a fuel flow regulating valve are independently provided. 2. In a fuel control device that branches a main fuel pipe into two systems and supplies fuel to each combustion chamber of a gas turbine having a two-stage combustion structure, a fuel pressure regulating valve and a fuel flow rate regulator are installed in the main fuel pipe. A fuel control device for a gas turbine, characterized in that a valve is provided, and a fuel flow valve is provided on either one of the branch pipes.