JPS6278437A - Exhaust temperature control system for gas turbine - Google Patents

Abstract

PURPOSE:To improve the output of a gas turbine by controlling an exhaust temperature according to a combustor gas temperature on the basis of both the amount of water or steam injection to prevent decrease in the maximum output of the gas turbine caused by increase in delivery pressure and air-fuel ratio, when water or steam is injected into the combustor. CONSTITUTION:Air-fuel ratio is obtained by a computing element 10 operating on detecting signals delivered by a fuel flow rate detector 8 in a gas turbine combustor and an air flow rate detector 9 in a compressor. Mw/Mf is obtained by a multiplier 13 operating on detecting signals delivered by the fuel flow rate detector 8 and a water or steam flow rate detector 11, and a temperature drop in exhaust temperature is calculated by the multiplier 13 on the output of both the computing element 10, 12. Secondly, after compensated by a computing element 15 for the output of the delivery pressure detector 14 of the compressor, the exhaust temperature is compensated for the above temperature drop by a multiplier 16, and established as its set value A. Thus deviation between the set value A and the exhaust temperature detected by a detector 17 is obtained by an adder 18, and used as a control signal for the regulating valve 6 of fuel flow rate through a proportional integrator 19.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an exhaust temperature control method for a gas turbine, and in particular, the exhaust temperature is set by controlling the water or steam injection flow rate by using the air-fuel ratio and the water or steam flow rate as control parameters. This invention relates to a gas turbine exhaust temperature control method that sets the temperature to the maximum regardless of the situation.

[Background of the invention]

The output of a gas turbine increases as the combustion gas temperature increases, but due to the resistance of high-temperature components (combustor, turbine drive, and silent blade 9) to high-temperature combustion gas, if the combustion gas temperature exceeds a certain allowable value, the lifespan of the high-temperature components may increase. Therefore, the maximum output of the gas turbine should be controlled using the maximum temperature of the combustion gas, but even if the combustion gas temperature is directly measured, the temperature of the combustion gas at the measuring part will be Because the distribution varies widely (general KI 000 or more).

Measuring the average combustion temperature is difficult.

For this reason, as described in Japanese Patent Publication No. 46-18203, the turbine exhaust temperature and compressor discharge pressure are detected using this maximum temperature rule, and the combustion gas temperature is thereby indirectly determined and the allowable value is determined. When this is reached, the PC performs control to suppress the output.

On the other hand, in recent years, water or steam injection type gas turbines that inject water or steam into a combustor have been put into practical use as a measure against pollution or to increase output.

As shown in Figure 3, the device that uses the water injection method is
A water injection hole 100 is provided in the center of the injection nozzle, and the water is sprayed from inside the flow of fuel 102 in the form of particles, so that the water becomes fine particles and cools the flame. FIG. 4 shows the state of flame formation by this fuel injection nozzle and the state of cooling by water injection. The solid line in FIG. 4 is the flow of flame, that is, the fuel particle group, and the broken line is the flow of atomized water. Also, parts A and B in FIG. 4 are high temperature parts.

This causes the water droplets to flow like a flame and cool the hot parts, thereby reducing the amount of NOx produced, which is mainly dominated by the temperature of the hot parts.

Next, the relationship between the temperature drop due to water injection and the amount of water injected will be explained based on FIG. 5.

Calculating the temperature drop due to water injection assumes that all of the injected water evaporates in the combustor, and calculates it from the thermal energy balance. It shows that the temperature drop is determined by the air-fuel ratio (ratio of air and fuel) and the amount of injected water. ing.

However, since the maximum temperature control is the same as the conventional method, there is a frequent problem that the water injection causes a temperature drop and the efficiency decreases. The conventional control method will be described below.

FIG. 6 shows the main equipment configuration of the gas turbine power plant. In the figure, the air flowing in from the atmosphere is compressor 1.
is compressed by the combustor 2 and introduced into the combustor 2. Here, the fuel introduced from the fuel regulating valve is ignited and combusted. Water or steam added due to pollution control etc. is guided to the combustor 2 via the water (steam) injection regulating valve 7, expanded by the turbine 3, and this energy is directly connected to the combustion engine 1! Transmitted to machine 4, ii! The energy is converted into air energy and transmitted to the grid via the circuit breaker 5. In addition, when controlling a gas turbine, as shown in Fig. 7, there is startup control that controls the gas turbine from startup to rated speed, and speed, load control, and gas turbine combustion that controls during load operation. The fuel regulating valve is controlled by selecting one control mode from three control modes of exhaust temperature control that have protective elements so as to operate within a gas temperature tolerance range.

Next, the thermodynamic cycle of the gas turbine is shown in FIG.

In FIG. 8, the temperature of the inhaled air increases as it is compressed. Then, the gas that exploded in the combustor 2 becomes high-temperature gas and moves to the combustor 2 outlet side, and the turbine 3
The expanded gas is exhausted. Therefore, the amount of transition from the temperature on the combustor outlet side to the exhaust temperature is the work of the gas turbine i:
(output), and the higher the allowable combustion temperature T3, the more the output increases. At this time, as the intake air temperature decreases to A-+B-+C, the amount of transition from the temperature on the combustor outlet side to the exhaust temperature increases.

Next, FIG. 9 shows the relationship between the second compressor discharge pressure P2 and the exhaust temperature setting T4s. In FIG. 9, since the thermodynamic cycle of the gas turbine changes depending on the intake air temperature, the change in the atmosphere is detected by the discharge pressure of the compressor 1, and this value is used as a parameter to keep the allowable combustion temperature T3 constant. The characteristic of the exhaust gas temperature T4 obtained from the figure is the characteristic shown in FIG. Therefore, the exhaust gas temperature control shown in FIG. 7 sets the exhaust temperature with respect to the compressor discharge pressure P2 from FIG. 9 and prevents it from exceeding this value.

Next, FIGS. 10 and 11 show changes in compressor discharge pressure and exhaust temperature at the maximum allowable combustion gas temperature when the amount of water or steam injected is gradually increased.

In Fig. 1O, when the atmospheric temperature is B, when the amount of water or steam injected is increased from I to mouth to /..., the compressor discharge pressure P2 increases to
The exhaust temperature T4 increases as shown in →B'→C'.
→・It descends like J. This is because the water injected into the combustor is vaporized and mixed with the combustion gas, resulting in an increase in the combustion gas flow rate, which causes an increase in the discharge pressure (i'
→Ro′→Ha′)? By bringing.

472 mouths', .

Figure 1 shows the results by applying ``, `` to Figure 9, and similarly applying each point in the case of atmospheric temperatures A and B to Figure 9.
Figure 1.

In FIG. 11, as the water or steam injection amount increases from A to B to C, the exhaust temperature setting T4s becomes higher.

In this way, in conventional equipment, such as exhaust temperature control,
For control when there is no flow of water or steam.

For example, if the setting is set in (a), even if the amount of water or steam injected is 1 or 3, it will be controlled by the control line in (a), which has the disadvantage that the fuel will be suppressed before the maximum combustion temperature of the gas turbine is reached. Ta.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an exhaust gas temperature control system for a gas turbine that can increase the output of the gas turbine according to the gas temperature of the combustor. It is in.

[Summary of the invention]

In order to achieve the above object, the present invention provides a method for adjusting the combustor gas temperature based on the amount of water or steam injection and the air-fuel ratio in order to prevent a drop in the maximum output of the gas turbine due to an increase in discharge pressure when water or steam is injected. The feature is that the exhaust temperature is controlled accordingly.

[Embodiments of the invention]

A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a preferred embodiment of the present invention. In FIG. 1, an air-fuel ratio is determined by a calculator 10 based on a signal detected by a fuel flow rate detector 8 and a signal detected by a flow rate detector 9. On the other hand, based on the signals detected by the fuel flow rate detector 8 and the water or steam flow rate detector 11, and the fuel flow rate signal.

The arithmetic unit 12 calculates MW/Mf, and the multiplier 13 calculates the signal from the arithmetic unit 10.12 to calculate the exhaust gas temperature drop as shown in FIG.

Further, based on the signal detected by the compressor discharge pressure detector 14, the arithmetic unit 15 corrects the exhaust temperature.

The multiplier 16 corrects the temperature drop due to the water injection flow rate from the multiplier 13, and uses this to control the exhaust temperature (maximum allowable output).
The settings are as follows.

Further, the signal detected by the exhaust temperature detector 17 is sent to the adder 1.
8, and a proportional integrator 19 uses the fuel flow rate g as a control signal for the valve. At this time, the control characteristics of the output signal A (exhaust temperature set value) of the multiplier 16 and the feedback signal are shown in FIG.

Water or steam injection flow rate MW with respect to compressor discharge pressure P,
Although the output decreases due to water injection due to the air flow rate Ma+fuel flow rate Mf, the maximum output can be achieved by increasing the exhaust temperature setting.

[Effects of the Invention] As explained above, according to the present invention, the combustion temperature becomes the maximum allowable value regardless of the amount of water or steam injected, so the output of the gas turbine can be maximized. You can get the same effect.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between compressor discharge pressure and exhaust temperature setting, and FIG. 3 is a sectional view of a conventional water injection fuel nozzle. Figure 4 is a diagram to explain the flame formation and flow of water droplets by a conventional fuel nozzle, Figure 5 is a diagram to explain the temperature drop due to water injection, and Figure 6 is the main part of the conventional device. The configuration diagram, Figure 7 is a diagram for explaining the conventional antibacterial method, Figure 8 is a diagram showing the relationship between enthalpy and temperature, and Figures 9 and 9 are diagrams showing the relationship between compressor discharge pressure and exhaust temperature settings. Diagram showing the relationship between. FIG. 10 is a diagram showing the relationship between enthalpy and temperature. FIG. 11 is a diagram showing the relationship between compressor discharge pressure and exhaust temperature setting, 1...Compressor, 2...Combustor, 3...Turbine,
4... Generator, 5... Circuit breaker, 6... Fuel regulating valve, 7... Water or steam injection regulating valve, 8... Fuel flow rate detector, 9... Air flow rate detector , 10... Arithmetic unit, 1
1... Water or steam flow rate detector, 12... Arithmetic unit, 1
3... Multiplier, 14... Compressor discharge pressure detector, 1
5... Arithmetic unit, 16... Multiplier, 17... Exhaust temperature detector, 18... Adder. 19...Proportional integrator.

Claims (1)

[Claims] 1. For gas turbines that have a device that injects water or steam into the combustor, determine the set value of the exhaust temperature to maintain the gas turbine at maximum output from the discharge pressure of the compressor, and determine the air-fuel ratio and the flow rate of water or steam. Find the temperature at which the exhaust temperature drops due to water or steam injection, find the fuel flow rate to raise the exhaust temperature that has dropped from this temperature to the set value, and operate the gas turbine based on this fuel flow rate. Characteristic gas turbine exhaust temperature control method.