JPS63183230A - Control method for combustion temperature of gas turbine - Google Patents

Abstract

PURPOSE:To maintain an optimum combustion temperature by calculating changes in exhaust gas temperature characteristics from the amount of heat generated with fuel, compensating the exhaust gas temperature characteristics, and controlling fuel flow rate so that the differential between the compensation value and the exhaust gas temperature measurement is reduced. CONSTITUTION:An air pressure signal PCD at a compressor outlet is inputted to a 1st function device 1 and a generated heat signal LHV is inputted to a 2nd function device. Output signals from the function devices 1, 2 are inputted to an operation device 6 and an output TX from the operation device 6, together with an output TXMAX from a signal generator 3, is inputted to a low value selector 7. A low value signal TXL selected with the low value selector 7 is compared with an output signal TXM of a medium value selector 4 in a comparator 8. The comparator 8 outputs the differential between the control value TXL of exhaust gas of a gas turbine and the medium value TXM to control the exhaust gas temperature of the gas turbine by outputting a gas turbine control signal VCE from a proportional integrator 9 so that the medium value TXM becomes equal to the control value TXL.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas turbine that measures gas turbine compressor discharge air pressure and gas turbine exhaust gas temperature, and uses these measured values to control gas turbine combustion temperature. The present invention relates to a combustion temperature control method.

[Traditional technique]

Because gas turbines use high-temperature gas.

Controlling the combustion temperature is the most important issue in order to ensure the service life of the high-temperature turbine parts. There are several methods for controlling gas turbine combustion temperature, but it is not a good idea to directly measure turbine combustion temperature because the temperature is too high and the temperature distribution is not constant. A common method is to estimate combustion temperature from air pressure and gas turbine exhaust gas temperature.

FIG. 2 is an explanatory diagram showing the structural configuration of a -shaft type gas turbine as an example of a gas turbine to which the present invention is applied to perform temperature control. Furthermore, a conceptual diagram of the control of such a gas turbine is shown in FIG. 3, and a shaft-type gas turbine is shown in FIG.

Gas turbine compressor 21. Combustor 22. gas turbine 2
39 Loads such as generators 24. It has a fuel supply system including a fuel cutoff valve 25 and a fuel flow rate adjustment valve 6. In addition, the conventional gas turbine control system shown in Fig. 3 has a low value selection 9.
27, the VCE indicates a gas turbine control signal, and the elements for controlling the combustion flow rate supplied to the combustor 22 (FIG. 2) are the combustion gas or exhaust gas temperature in the startup state, and the startup control signal; In addition, in a loaded state, the combustion gas or exhaust gas temperature and the speed control signal are required to keep one rotational speed constant in a gas turbine for two generators, so in a partial load state, the fuel flow rate is controlled by speed control. However, speed control alone cannot suppress the life consumption of gas turbine high-temperature components due to the combustion temperature that inevitably rises when the load increases. Therefore, a certain upper limit value of gas turbine combustion temperature is set. It is controlled so that it does not exceed this value. This is temperature control.

FIG. 4 shows a typical gas turbine state diagram.

In FIG. 4, 28 is the gas turbine compressor inlet.

29 indicates the gas turbine compressor height 0.30 indicates the gas turbine inlet, and 31 indicates the gas turbine outlet.As mentioned above, the combustion temperature of the gas turbine is determined by the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature. It is common to estimate this, but if we consider this based on the state diagram in Figure 4, there is a certain relationship between the gas turbine compressor discharge air pressure, the gas turbine exhaust gas temperature, and the combustion temperature. It turns out that there is something. Here, since the enthalpy on the vertical axis in FIG. 4 is approximately proportional to the temperature, the vertical axis can be considered to be the temperature.

FIG. 5 shows a gas turbine state change diagram, and FIG. 6 shows the relationship among gas turbine compressor discharge air pressure, gas turbine exhaust gas temperature, and combustion temperature. In FIG. 5, at a certain upper temperature limit of the gas turbine, that is, 28 → 29 → 30
→ Assuming that it is being operated at 31, 6th, due to some change in operating conditions.

Assume that the gas turbine compressor discharge air pressure increases to 29'. At this time, if the fuel flow rate does not change, 28
' → 29' → 30'' → 311, and the combustion temperature exceeds the upper limit value TF, so the fuel flow rate is reduced,
If the combustion gas temperature is set to 30' point, 28 → 29
The shape is '→30'→31'.

Now, various operating conditions of gas turbines (atmospheric temperature.

When the relationship between the gas turbine compressor discharge air pressure Pco, the gas turbine exhaust gas temperature Tx, and the combustion temperature TF is plotted under a load 9, etc.), it becomes as shown in Fig. 6,
Finally, the combustion temperature can be calculated using the formula expressed as TF=f (Pan, Tx). In this example, the gas turbine compressor discharge air pressure Pco is 29
', if the gas turbine exhaust gas temperature is 31', the calculated combustion temperature value exceeds the combustion temperature upper limit value TF11m, so the fuel flow rate is throttled and the combustion temperature upper limit value T F A I
It is controlled to return to II.

FIG. 7 shows a conventional gas turbine combustion gas control system. In this control system, the gas turbine compressor discharge air pressure is measured by a detector (not shown) installed at the gas turbine compressor outlet. The PCD becomes a controlled exhaust gas temperature signal Tx, which is the gas turbine exhaust gas temperature, by the function unit 32. on the other hand.

Assuming that the pressure detector fails, the signal generator 3 outputs the controlled exhaust gas temperature upper limit signal TXHAX, and the lower value of either the controlled exhaust gas signal Tx or the controlled exhaust gas temperature upper limit signal TXM^X is selected by the low value selector 33. and outputs the gas turbine exhaust gas temperature control value Txt.

On the other hand, the gas turbine exhaust gas temperature signal 'I'' The temperature control value TXL and the intermediate value T (H) enter the comparator 8, the difference between them is output, and the intermediate value 'I''xs is output from the proportional integrator 9 as the temperature control value TXL. The gas turbine fuel control signal is output so that the At this time, the output signal of the temperature rise rate limiter 5 is also compared with respect to the output temperature rise rate, and is controlled so as not to exceed the limit value. This conventional gas turbine combustion temperature control system is advantageous in that control is simplified.

Note that related devices of this type include, for example, Japanese Patent Application Laid-open No. 60-247014 "Gas Turbine Combustion Gas Temperature Control Method and Apparatus".

[Problem that the invention seeks to solve]

The following fuels are applicable to the conventional combustion temperature control method described above.

(1) Gaseous fuel with high calorific value (methane, propane, etc.) (2
)Liquid fuels These fuels have the feature that the fluctuation in the calorific value per unit is relatively small (about 10%). For these fuels,
At the highest combustion temperature, the ratio of fuel flow rate to air flow rate (f/a
) becomes f/a 42/100, and even if the calorific value fluctuates by ±10% in this state, the ratio (J/a) is f/a''
Fla ~2.2/100, which is very small overall.

Therefore, the combustion temperature control is determined by the previously mentioned formula % formula %) Sufficient accuracy was maintained.

In recent years, low calorific value fuels such as coal gasification have been in the spotlight. The calorific value of these fuels is about 1/10 that of conventional high calorific value fuels.

Due to double, f/a is f / a press 20 / 100 It's becoming more common.

A further problem is that the calorific value is said to vary greatly depending on the type of coal and operating conditions, which is the current situation.

Variations of ±10 to ±20% are expected to occur.

If three types of fuel with greatly different calorific values are combusted at a constant combustion temperature, the relationship between the gas turbine compressor discharge air pressure Pco and the exhaust gas temperature Tx will be graphed as shown in Figure 8. This diagram is.

This indicates that the lower the calorific value, the more the Pan-Tx curve shifts to the right. (Increase in fuel gas flow rate → Increase in amount of combustion gas → Larger pressure ratio) In other words, the same curve
The same ■ are located to the right of each other.

Also, the lower the 1 calorific value, the lower the Pco-T when the calorific value fluctuates.
For example, when f / a = 30 / 100, the fluctuation of the x curve (constant combustion temperature) becomes severe. =±10
%, f/a = 27~33/100
As a result, the range of change in gas amount increases.

From the above, one conventional control line TF = f (Pans
Tx) has the problem that it is not possible to control the combustion temperature to be constant.

Furthermore, in addition to low calorific value fuels such as coal gas, other high calorific value fuels (light oil, methane, etc.) are used for startup or backup purposes.
Even in so-called dual fuel gas turbines that use
Conventional single control line TF = f (Pco+Tx)
However, the problem arises that it is not possible to control the combustion temperature to be constant.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to avoid complicating fuel control, regardless of the calorific value of the fuel used (the calorific value of the fuel used). An object of the present invention is to provide a control method that can maintain the combustion temperature of a gas turbine at an optimum temperature even if the combustion temperature changes.

Means for Solving Problem C] The method of the present invention created to achieve the above object detects the gas turbine fuel calorific value, and uses the gas turbine fuel calorific value to perform gas turbine compression according to the fuel calorific value. Calculates changes in machine discharge air pressure and gas turbine exhaust gas temperature control curve, corrects the aforementioned control curve based on this calculated value,
This value is used as the gas turbine exhaust gas temperature control value and is compared with the gas turbine exhaust gas actual value, and by controlling the difference to minimize it, the gas turbine combustion temperature is set to the set value regardless of the gas turbine fuel. Control so that it becomes familiar.

Based on the above-mentioned principle, the method of the present invention is a concrete configuration for applying the same to a practical aspect.

a. Detect the calorific value of the gas turbine fuel; b. Calculate the change in exhaust gas temperature characteristics with respect to the discharge air pressure of the gas turbine compressor using the detected calorific value; C0 Calculate the exhaust gas temperature characteristics by the above calculated value. d. Compare the above correction value with the actual measured value of exhaust gas temperature.

e. Adjust the fuel flow rate so as to minimize the difference in the above comparison.

[Effect]

According to the above method, the calorific value of the fuel used is incorporated into the control element, and the characteristic values are corrected based on the measured calorific value, so even if the calorific value of the fuel used changes, the combustion temperature can be maintained at the optimum value. can be kept.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 is a control system diagram showing an embodiment of a gas turbine combustion temperature control device for implementing the present invention.

1 is the first function unit. This first function unit 1 includes a compressor outlet air pressure signal Pan measured by a pressure detector (not shown) provided at the gas turbine compressor outlet.
is input.

Reference numeral 2 denotes a second function unit, into which a calorific value signal LHV measured by a fuel calorific value detector (not shown) provided in the fuel system is input.

3 is a signal generator that is activated when the pressure sensor fails.

The output signal of the first function unit 1 and the second function unit 2
The output signal of is input to the arithmetic unit 6, and its output Tx is input to the low value selector 7 together with the output TXH^X of the signal generator 3.

Low value signal TXL selected by the low value selector 7
is compared with the output signal TXM of the intermediate value selector 4 in the comparator 8.

The gas turbine compressor discharge air pressure Pco measured by a pressure detector installed at the gas turbine compressor outlet is determined by the first function unit 1 as a controlled exhaust gas temperature signal Tx in the case of a reference fuel (arbitrarily set).

Also, the fuel calorific value signal L installed in the fuel system
HV becomes the gas turbine exhaust gas change control signal ΔTx when the fuel heat generation is 1 LllV by the second function generator 2. These signals Txo+ΔTx are calculated by the calculator 6 and become the control exhaust gas temperature signal 'rx when the fuel heat generation is 1LHV.

On the other hand, assuming a pressure detector accident, the signal generator 3 outputs the controlled exhaust gas temperature signal TxnAx, and the low value selector 7 selects the lower value of either the controlled exhaust gas temperature signal Tx or the controlled exhaust gas upper limit signal TXM^. and select the fuel calorific value L.
The HV gas turbine exhaust gas control value Txt is output.

On the other hand, the gas turbine exhaust gas signal Txx・measured by a plurality of temperature sensors installed in the gas turbine exhaust gas
...TXN enters the intermediate selector 4, and the intermediate value Tx-
is output. The gas turbine exhaust gas temperature control value TX
The intermediate value TXM between the gas temperature and the gas turbine exhaust gas temperature is determined by the comparator 8.
The difference is output, and the intermediate value TXM of the gas turbine exhaust gas temperature becomes the gas turbine exhaust gas temperature control value Txt.
, the gas turbine control signal V is output from the proportional integrator 9 so that
CE is output and the gas turbine exhaust gas temperature is controlled. At this time, the comparator 8 also compares the temperature increase rate output from the temperature increase rate meter 5, and controls it so that it does not exceed the control value.

〔Effect of the invention〕

According to the present invention, the combustion temperature of the gas turbine is controlled to the set value regardless of the fuel calorific value, so the simplicity of control is not impaired, and regardless of the fuel calorific value, the combustion temperature of the gas turbine is controlled to the set value. This has the effect of being able to optimally control the gas turbine combustion temperature, which in turn has the effect of reliably controlling the required output of the gas turbine, and has the effect of maintaining the high source gas life of the gas turbine.

In particular, the present invention has great practical effects when applied to gas turbines that use low calorific value fuels such as coal gas and dual fuels such as low calorific fuels and high calorific fuels (for startup, backup, etc.).

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a control device configured to implement the control method of the present invention. FIG. 2 is an explanatory diagram of a single-shaft gas turbine shown as an example of an object to which the method of the present invention is applied. FIG. 3 is a conceptual control diagram for explaining a conventional gas turbine combustion temperature control method. Fourth
5 is a diagram showing the state of the gas turbine, FIG. 5 is a chart showing changes in the state of the gas turbine, and FIG. 6 is a chart showing the relationship between gas turbine compressor discharge air pressure, gas turbine exhaust gas temperature, and combustion temperature. FIG. 7 is a control system diagram of a gas turbine in the prior art. FIG. 8 is a chart showing the relationship between the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature when three types of fuels having largely different calorific values are combusted at a constant combustion temperature. 1...first function unit, 2...second function unit, 3...
- Signal generator, 4... Intermediate value selector, 6... Arithmetic unit, 7... Low value selector, 8... Comparator, 9... Proportional integrator.

Claims (1)

[Claims] 1. A method of measuring the discharge air pressure of a gas turbine compressor and the gas turbine exhaust gas temperature, and controlling the combustion temperature by controlling the gas turbine fuel flow rate based on these measured values, comprising: a. , detect the calorific value of the gas turbine fuel; b. calculate the change in exhaust gas temperature characteristics with respect to the discharge air pressure of the gas turbine compressor using the detected calorific value; c) determine the exhaust gas temperature using the calculated value. d. Comparing the corrected value with an actual measured value of exhaust gas temperature; e. Adjusting the fuel flow rate so as to minimize the difference in the comparison. Control method.