JPH076412B2 - Gas turbine combustion temperature control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention measures a gas turbine compressor discharge air pressure and a gas turbine exhaust gas temperature, and uses these measured values to control a gas turbine combustion temperature. The present invention relates to a combustion temperature control method.

[Conventional technology]

Since high temperature gas is used in the gas turbine, control of its combustion temperature is the most important issue for ensuring the life of the high temperature member of the turbine. There are several methods for controlling the gas turbine combustion temperature, but direct measurement of the turbine combustion temperature is not a good idea because the temperature is too high, the temperature distribution is not constant, etc. The method of estimating the combustion temperature from the air pressure and the gas turbine exhaust gas temperature is common.

FIG. 2 is an explanatory diagram showing a schematic configuration of a single-shaft gas turbine as an example of a gas turbine to which the present invention is applied for temperature control. Further, FIG. 3 shows a control conceptual diagram of such a gas turbine. The single-shaft gas turbine shown in FIG. 2 includes a gas turbine compressor 21, a combustor 22, a gas turbine 23, a load 24 such as a generator, a fuel supply system including a fuel cutoff valve 25 and a fuel flow rate adjusting valve 26. Have The conventional gas turbine control system shown in FIG. 3 includes a low value selector 27, and VCE indicates a gas turbine control signal. The elements for controlling the combustion flow rate supplied to the combustor 22 (Fig. 2) are the combustion gas or exhaust gas temperature and the start control signal in the startup state, and the combustion gas or exhaust gas temperature and the speed control in the loaded state. It is a signal. In a gas turbine for a generator, it is necessary to keep the rotation speed constant, and therefore the fuel flow rate is controlled by speed control in the partial load state. However, the speed control alone cannot suppress the life consumption of the gas turbine high temperature member due to the combustion temperature that inevitably rises when the load increases. For that reason,
A certain fixed gas turbine combustion temperature upper limit value is set and controlled so as not to exceed this value. This is temperature control.

FIG. 4 shows a typical gas turbine state diagram. In FIG. 4, 28 is a gas turbine compressor inlet, 29 is a gas turbine compressor outlet, 30 is a gas turbine inlet, and 31 is a gas turbine outlet. Here, as described above, the combustion temperature of the gas turbine is generally estimated from the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature, but this is estimated based on the state diagram of FIG. Considering that, there is a certain relationship between the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature and the combustion temperature.
Here, since the enthalpy on the vertical axis of FIG. 4 is almost 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 between the gas turbine compressor discharge air pressure, the gas turbine exhaust gas temperature, and the combustion temperature. In FIG. 5, it is assumed that the gas turbine is operated at a certain temperature upper limit value, that is, 28 → 29 → 30 → 31. Next, due to some change in operating conditions, the gas turbine compressor discharge air pressure rises,
Let's say At this time, if the fuel flow rate does not change, 2
8 ′ → 29 ′ → 30 ″ → 31 ″, and the combustion temperature becomes the upper limit value T _F lim
Will exceed. Therefore, if the fuel flow rate is reduced so that the combustion gas temperature reaches the 30 'point, the form becomes 28 → 29 ′ → 30 ′ → 31 ′.

Now, various operating conditions of the gas turbine (atmospheric temperature, load,
Etc.) under the gas turbine compressor discharge air pressure
The plot of the relationship between P _CD , gas turbine exhaust gas temperature T _X and combustion temperature T _{F is} as shown in Fig. 6, and finally, the combustion temperature is expressed by the formula T _F = (P _CD , T _X ). Can be calculated. In this example, if the gas turbine compressor air pressure P _CD is 29 ′ and the gas turbine exhaust gas temperature is 31 ′, the calculated combustion temperature value exceeds the combustion temperature upper limit value T _F lim, so reduce the fuel flow rate. , And is controlled to return to the combustion temperature upper limit value T _F lim.

FIG. 7 shows a conventional gas turbine combustion gas control system. In this control system, the gas turbine compressor discharge air pressure P _CD measured by a detector (not shown) installed at the gas turbine compressor outlet is controlled by the function unit 32 as a control gas temperature signal indicating the gas turbine exhaust gas temperature. It becomes T _X.
On the other hand, assuming a time pressure detector failure, outputs control the exhaust gas temperature upper limit signal T _XMAX by signal generator 3, low value selector either low values of the control gas signal T _X control the exhaust gas temperature upper limit signal T _XMAX The gas turbine exhaust gas temperature control value T _XL is selected by the device 33 and output.

On the other hand, the gas turbine exhaust gas temperature signals T _X1 ...... T _XN measured by a plurality of temperature detectors (not shown) installed at the gas turbine exhaust port enter the intermediate value selector 4
T _XM is output. Also, the temperature control value T _XL and the intermediate value T _XM
Is input to the comparator 8, the difference is output, and the proportional integrator 9 outputs the gas turbine fuel control signal so that the intermediate value T _XM becomes the temperature control value T _XL . At that time, the output signal of the temperature increase rate limiter 5 is also compared with respect to the output temperature increase rate, and the output signal is controlled so as not to exceed the limit value. This conventional gas turbine combustion temperature control system is advantageous in that the control is simplified.

Note that, as a device related to this type, there is, for example, JP-A-60-247014 "Gas turbine combustion gas temperature control method and device".

[Problems to be solved by the invention]

The fuels to which the conventional combustion temperature control method described above can be applied are as follows.

(1) Gas fuel with high calorific value (methane, propane, etc.) (2) Liquid fuel These fuels have the characteristic that the calorific value fluctuation is relatively small (about 10%). For these fuels,
Ratio of fuel flow rate to air flow rate at maximum combustion temperature (/ a)
Becomes / a≈2 / 100, and even if the heat value fluctuates by ± 10% in this state, the ratio (/ a) becomes /a≈1.8 to 2.2 / 100, which is very small overall.

Therefore, the combustion temperature control was maintained with sufficient accuracy by the above equation T _F = (P _CD , T _X ).

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 of that of conventional high calorific value fuel, and / a is becoming / a≈2 / 100 with this.

Furthermore, it is said that the calorific value fluctuates greatly depending on the coal type and operating conditions. Currently, ± 10 to ± 20%
Is expected to fluctuate.

Here, a graph showing the relationship between the gas turbine compressor discharge air pressure P _CD and the exhaust gas temperature T _X when three types of fuels having large calorific values are burned at a constant combustion temperature is as shown in FIG. Become. This figure, as the calorific value is low, P _CD -T _X
This means that the curve shifts to the right. (Increase in fuel gas flow rate → Increase in combustion gas amount → Higher pressure ratio) That is, the same as the curve and the same as the curve are located on the right side.

Also, the lower the calorific value, the more severe the fluctuation of the P _CD -T _X curve (constant combustion temperature) when the calorific value varies. For example, in the case of / a = 30/100, when it becomes ± 10%, / a = 27〜
It becomes 33/100, and the variation range of the gas amount becomes large.

From the above, some problems occur when the conventional one control line T _F = (P _CD , T _X ) cannot control the combustion temperature constant.

In addition to low calorific value fuels such as coal gas, other high heat value fuels (light oil, methane, etc.) for start-up or backup purposes.
In a so-called dual fuel gas turbine that uses
If a conventional single control line T _F = (P _CD , T _X ) cannot be used to control the combustion temperature at a constant level, problems will occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to control the fuel without making it particularly complicated, regardless of the heat generation amount of the used fuel (heat generation amount of the used fuel). It is an object of the present invention to provide a control method capable of maintaining the combustion temperature of a gas turbine at an optimum temperature (even when the temperature changes).

[Means for solving problems]

The method of the present invention created in order to achieve the above object detects the gas turbine fuel calorific value and uses the gas turbine fuel calorific value to control the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature by the fuel calorific value. Calculate the change of the curve, correct the control curve based on this calculated value,
By comparing this value as the gas turbine exhaust gas temperature control value with the actual measured value of the gas turbine exhaust gas, and performing control so as to minimize the difference, the gas turbine combustion temperature can be determined regardless of the fuel of the gas turbine. Control so that the set value is reached.

Based on the above-mentioned principle, as a specific configuration for applying this to a practical aspect, the method of the present invention includes: a. Detecting the calorific value of the gas turbine fuel; and b. Using the calorific value detection value, The change in the exhaust gas temperature characteristic with respect to the discharge air pressure of the gas turbine compressor is calculated, c. The exhaust gas temperature characteristic is corrected by the above calculated value, and d. The corrected value is compared with the measured value of the exhaust gas temperature, e. Adjust the fuel flow rate to minimize the difference in the above comparison.

[Action]

According to the above method, the calorific value of the used fuel is incorporated in the control element, and the characteristic value is corrected based on the measured calorific value. I can keep it.

〔Example〕

An embodiment 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 carrying out the present invention.

1 is a first function unit. A compressor outlet air pressure signal P _CD measured by a pressure detector (not shown) provided at the gas turbine compressor outlet is input to the first function unit 1.

Reference numeral 2 is a second function unit, to which a heat generation amount signal LHV measured by a fuel heat generation amount detector (not shown) provided in the fuel system is input.

Reference numeral 3 is a signal generator that operates when the pressure detector fails.

The output signal of the first function unit 1 and the second function unit 2
Is output to the arithmetic unit 6 and its output T _X is input to the low value selector 7 together with the output T _XMAX of the signal heater 3.

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

The gas turbine compressor discharge air pressure P _CD measured by the pressure detector installed at the gas turbine compressor outlet is
The first function unit 1 provides the control exhaust gas temperature signal T _XO for the reference fuel (arbitrarily set). Further, the fuel calorific value signal LHV installed in the fuel system becomes the gas turbine exhaust gas change control signal ΔT _X at the time of the fuel calorific value LHV by the second function unit 2. These signals T _XD and ΔT _X are calculated by the calculator 6 and become the control exhaust gas temperature signal T _X at the time of the fuel heat generation amount LHV.

On the other hand, assuming that the pressure detector is in an accident, the signal generator 3 outputs the control exhaust gas temperature signal T _XMAX, and the low value selector selects the lower one of the control exhaust gas temperature signal T _X and the control exhaust gas upper limit signal T _XMAX . 7 is selected and the gas turbine exhaust gas control value T _XL of the fuel heating value LHV is output.

On the other hand, the gas turbine exhaust signal T _X1 ...... T measured by a plurality of temperature detectors installed in the gas turbine exhaust
_XN enters the intermediate selector 4, and the intermediate value T _XM is output. The intermediate value T _XM of the gas turbine exhaust gas temperature control value T _XL and the gas turbine exhaust gas temperature enters the comparator 8, and the difference is output, and the intermediate value T _XM of the gas turbine exhaust gas temperature is the gas turbine exhaust gas temperature control value T _XL. Then, the gas turbine control signal VCE is output from the proportional integrator 9 to control the gas turbine exhaust gas temperature. At this time, the temperature rise rate output from the temperature rise rate unit 5 is also compared by the comparator 8 and controlled so as not to exceed the control value.

〔The invention's effect〕

According to the present invention, the combustion temperature of the gas turbine is controlled to the set value regardless of the heat value of the fuel.
The effect is that the gas turbine combustion temperature can be optimally controlled irrespective of the heat generation amount of the fuel without impairing the control simplicity, and thus the output that requires the gas turbine can be reliably controlled. The effect is to maintain the high temperature gas life of the gas turbine.

In particular, the present invention is applied to a gas turbine using a low calorific value fuel such as coal gas and a dual fuel consisting of a low calorific value fuel and a high calorific value fuel (for start-up, backup, etc.) and exerts a great practical effect.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a control device configured to carry out 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 control conceptual diagram for explaining a gas turbine combustion temperature control method in the prior art. Fourth
FIG. 5 is a diagram showing the state of the gas turbine, FIG. 5 is a diagram showing changes in the state of the gas turbine, and FIG. 6 is a diagram showing the relationship between the gas turbine compressor discharge air pressure and the gas turbine exhaust gas temperature and combustion temperature. FIG. 7 is a control system diagram of a gas turbine in the related 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 large calorific values are burned at a constant combustion temperature. 1 ... 1st function device, 2 ... 2nd function device, 3 ... signal generator, 4 ... intermediate value selector, 6 ... calculator, 7 ... low value selector, 8 ... Comparator, 9 ... Proportional integrator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naga Hasegawa 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Factory (56) References JP-A-61-40432 (JP, A)

Claims (1)

[Claims] 1. A method for measuring a discharge air pressure of a gas turbine compressor and a temperature of a gas turbine exhaust gas, and controlling a gas turbine fuel flow rate based on these measured values to control a combustion temperature. Detect the calorific value of the fuel, b. Calculate the change in the exhaust gas temperature characteristic with respect to the discharge air pressure of the gas turbine compressor by using the detected calorific value, and c. Correct the exhaust gas temperature characteristic with the calculated value. Then, d. The above correction value and the measured value of the exhaust gas temperature are compared, and e. The fuel flow rate is adjusted so as to minimize the difference in the above comparison, a gas turbine combustion temperature control method.