JPS6125897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine control device, and particularly to a gas turbine control device that estimates a turbine inlet gas temperature with high precision and controls the operation of a gas turbine based on the temperature estimate. The present invention relates to a gas turbine control device capable of efficient operation.

FIG. 1 shows a control system diagram of a gas turbine 100 and a gas turbine control device 200 used for its operation. During operation, the compressor 1 takes in air from an air intake port 2, compresses it, and sends it into the combustor 4 through the compressed air delivery port 3. On the other hand, fuel delivered by the fuel supply device 5 is taken into the combustor 4 and combusted together with the compressed air, and the generated combustion gas is guided to the turbine 7 through the combustion gas passage 6. The combustion gas guided to the turbine 7 rotates the turbine, and the compressor 1 and the generator 8 are mechanically connected to the turbine 7.
After driving, it is released into the atmosphere from the exhaust duct 9 as exhaust gas.

A fuel control device 10 is provided as a connecting end from the gas turbine control device 200 for operating the above gas turbine to adjust the fuel flow rate from the fuel supply device 5. Further, as detection ends, an exhaust gas temperature detector 11, a turbine speed detector 12, and a compressor discharge pressure detector 13 are provided.

In this type of gas turbine control, when the turbine inlet gas temperature exceeds the temperature set value, the turbine speed or load control is suppressed and the turbine inlet gas temperature is controlled to be below the temperature set value. is necessary. On the other hand, in order to maximize the efficiency of the gas turbine, it is desirable to operate the turbine with the gas temperature at the inlet of the turbine as high as possible, so the temperature setting value is determined in relation to the service life.

The detailed configuration and operation of the gas turbine control device 200 will be described below.

First, the speed/load control system detects the rotational speed of the turbine 7 with a speed detector 12 such as an electromagnetic pickup, and combines this detection signal, that is, the turbine speed signal N and the speed setting signal N _S set in the speed setting device 14. According to the speed deviation ΔN, the speed adjustment rate setter 15
A load request signal L _D is generated based on a speed regulation rate preset in the proportional controller ₁₆ .
is converted into a fuel demand signal _GNL for speed/load control and output to the low value selector 17. Therefore,
When the output end of the generator 8 is connected in parallel to the power system, the speed setter 14 becomes a load setter.

On the other hand, since the temperature distribution of the inlet gas temperature of the turbine 7 is uneven, the temperature control system conventionally uses the exhaust gas temperature signal _T From the compressor discharge pressure signal P _CD detected by the pressure detector 13 installed at the outlet 3, an estimated turbine inlet gas temperature T _F is determined using the turbine inlet gas temperature estimating device 18, and the estimated turbine inlet gas temperature T F is calculated. _F
and the temperature setting signal T _FS set in the temperature setting device 19.
The temperature deviation ΔT _F with respect to the temperature control signal G TF is input to the proportional-integral controller 20 , and the proportional-integrator 20 generates a temperature control fuel request signal G _TF and outputs it to the low value selector 17 . The low value selector 17 compares the speed/load control fuel demand signal _GNL and the temperature control fuel demand signal _GFT , and selects the lowest value signal among them as the fuel demand signal _GFLD for fuel control. provided to the device 10.

Next, the function of the turbine inlet temperature estimation device is
This will be explained using figures. FIG. 2 shows a T-S diagram of the Brayton cycle, where T represents the absolute temperature and S represents the entropy of the working fluid. The ideal characteristics of compressor 1 and turbine 7 with no loss are 1-
Although it is 2-3-4, it actually becomes 1-2'-3-4' because it involves a loss. P ₁ indicates atmospheric pressure and P ₂ indicates compressor discharge pressure. Here, if the turbine inlet gas temperature is estimated and controlled only by the exhaust gas temperature T ₄ ', the characteristic when the compressor discharge pressure P ₂ increases by ΔP ₂ to P ₂ ' is 1-2''-3'-4 ', and the turbine 7 will be operated at a place where the turbine inlet temperature is higher by ΔT _3. Therefore, in order to operate at the original turbine inlet temperature T ₃ , the exhaust gas temperature must be lower than T ₄ '. It is necessary to drive at a lower location by ΔT ₄ .

Regarding this point, the conventional method estimates the turbine inlet gas temperature using the following method. That is, as is clear from FIG. 2, if the exhaust gas temperature is T _x ,
When the compressor discharge pressure is P _CD , the estimated turbine inlet gas temperature T _F is given by the following equation.

T _{F =} A・_T 2″−3″−4″, and the turbine inlet temperature can theoretically be maintained at T ₃ .

However, as a gas turbine is operated for a long period of time, the characteristics of the compressor, combustor, and turbine deteriorate over time, and in particular, the efficiency of the turbine decreases. will occur.
In other words, when the turbine efficiency decreases, the gas expansion process within the turbine is as shown in Figure 3.
3"-4" to 3-4", and thus the turbine inlet gas temperature was being operated at T3, which was lowered by _{ΔT3 '} .

This is a drawback of the gas turbine control device according to the prior art, and due to aging, the efficiency of the gas turbine decreases by 5 to 10%, making it impossible to maintain high efficiency operation for a long period of time. This is the reason why the gas turbine requires more frequent maintenance and cannot operate continuously for a long period of time.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the drawbacks of the prior art described above and to provide a gas turbine control device that can control and maintain gas turbine efficiency at a value as high as possible regardless of whether turbine efficiency has deteriorated over time. .

That is, the control device of the present invention estimates the estimated value of the turbine inlet gas temperature based on a thermodynamic relational expression using the state value before the combustor. The gas turbine is configured to maintain the gas temperature at a set value and maintain high efficiency operation of the gas turbine.

FIG. 4 shows a gas turbine 100 and a gas turbine device 20 according to the present invention used for its operation.
0' control system diagram is shown. In this figure, the same symbols as in FIG. 1 represent the same things. Hereinafter, differences from FIG. 1 will be explained. The turbine inlet gas temperature estimating device 18', which is a feature of the present invention, includes compressor inlet air pressure detected by a compressor inlet air pressure detector 21 installed at the air intake port 2 of the compressor 1 and a compressor inlet air temperature detector 22. Signal P ₁ , compressor inlet temperature signal T ₁ , compressor discharge pressure detector 13 installed at the compressed air outlet 3, compressor discharge pressure signal P ₂ detected by compressor discharge temperature detector 23, compressor discharge temperature signal T ₂ , The fuel flow rate signal G _FL detected by the fuel flow rate detector 24 and the turbine speed signal N are input, and the estimated turbine inlet gas temperature T _F is determined using these operating state values.

Next, an estimation method of the turbine inlet gas temperature estimation device 18' according to the present invention will be explained. first,
Since the discharge flow rate G of the compressor 1 changes significantly depending on the atmospheric conditions, the corrected flow rate G _c and the corrected speed N _c are respectively expressed as corrected values converted to values under standard atmospheric conditions. It can be expressed as Here, T _1R and P _1R are reference values of atmospheric temperature and pressure. Further, the corrected flow rate G _c can be expressed as a function of the compression ratio R _c and the corrected speed N _c as follows: G _c =f(R _c , N _c ) (4). Here, R _c =P ₂ /P ₂ +1.

Next, the static energy balance equation at the turbine inlet can be expressed by the following equation.

H _F・{G・(1−m)+G _FL }=Q _F・{H ₂・G(1−m)+H _FL・G _FL } ...(5) Here, m is the bleed air from compressor 1, Compressor discharge flow rate loss coefficient considering leakage, etc.
H ₂ is the compressor discharge air enthalpy and is given by a function of compressor discharge air temperature T ₂ H ₂ =g _H (T ₂ ). H _FL is the calorific value of the fuel, H _F is the gas enthalpy at the turbine inlet, and Q _F is the combustor efficiency, which is expressed as a function of the fuel-air ratio R _FC , Q _F =h(R _FC ), and
The fuel-air ratio is given by R _FC =G _FL /{G(1-m)}.

Therefore, the estimated turbine inlet gas temperature T _F
can be obtained as a function T _F =g _T (H _F ) of the turbine inlet gas enthalpy H _F obtained from equation (5).

FIG. 5 is a calculation flow diagram when the above-mentioned turbine inlet gas temperature estimating device 18' is applied to a digital computerized control device. The calculation flow diagram is managed by the computer system program as one control program. The constant setting function 51 for setting the constants necessary for the following calculations operates only the first time, and from the second time onwards, it follows the periodic activation command periodically generated by the system program, and estimates the turbine inlet gas temperature as shown in the figure. A value T _F is calculated. In FIG. 5, 52 is a detection signal capture function 53 for capturing a detection signal from a process input device, and 54 is an ignition determination function for calculating an estimated value of turbine inlet gas temperature after ignition, and 54 is a compressor inlet air temperature T ₁ 55 is a compression ratio calculation function for determining the compression ratio R _C from the compressor inlet air pressure P ₁ and discharge pressure P ₂ , 56 is _{the modified speed N C and} The corrected flow rate calculation function is used to determine the corrected flow rate G _C from the compression ratio R _C , and a characteristic curve as shown in FIG. 6 is set using a data table formula or polynomial approximation. 57 is a compressor discharge flow rate calculation function for determining the compressor discharge flow rate G from the compressor inlet air pressure P ₁ , the same temperature T ₁ and the corrected flow rate G _C ; 58 is the compressor discharge temperature
The air enthalpy calculation function is used to determine the compressor discharge enthalpy from _T2 , and a characteristic curve (n=∞) as shown in FIG. 7 is set using a data table formula or polynomial approximation. 59 is the fuel flow rate G _FL
and a fuel-air ratio calculation function for determining the fuel-air ratio R _FC from the compressor discharge flow rate G; 60 is the fuel-air ratio R _FC
The combustor efficiency calculation function is used to determine the combustor efficiency Q _F from the combustor efficiency, and a characteristic curve as shown in Fig. 8 is set using a data table formula or polynomial approximation. 61
are compressor discharge flow rate G, fuel flow rate G _FL , compressor discharge enthalpy H ₂ and combustor efficiency Q _F
Turbine inlet gas enthalpy calculation function from 62
63 is a turbine inlet for calculating the estimated turbine inlet gas temperature T _F from the turbine inlet gas enthalpy H _F and the excess air ratio _n . Using the gas temperature calculation function, a characteristic curve as shown in FIG. 7 is set using a data table formula or polynomial approximation. 64 is the estimated turbine inlet gas temperature T _F
It is an output function to output.

As is clear from the above, according to the present invention, the state value before the combustor is taken in and the turbine inlet gas temperature is accurately estimated. Since the set value can be maintained accurately, the gas turbine can be operated with high efficiency. This can bring about excellent economical effects, such as lowering the frequency of gas turbine maintenance and enabling long-term continuous operation.

[Brief explanation of the drawing]

Figure 1 is a control system diagram of a conventional gas turbine and its control device, Figure 2 is a T-S diagram showing fluctuations in operating characteristics during compressor discharge pressure fluctuations in the Brayton cycle, and Figure 3 is a Brayton cycle diagram. A T-S diagram showing the fluctuations in operating characteristics when the turbine efficiency fluctuates in a cycle, FIG. 4 is a control system diagram of the gas turbine according to the present invention and its control device, and FIG. 5 is a diagram showing the turbine inlet gas temperature according to the present invention. A calculation flowchart of the estimation device, FIG. 6 shows the characteristic curve of the compressor, FIG. 7 shows the relationship between the temperature of the working fluid and enthalpy, and FIG. 8 shows the relationship between the fuel-air ratio and combustor efficiency. 100...Gas turbine, 200...Gas turbine control device, 1...Compressor, 2...Air intake port, 3...Compressed air outlet, 4...Combustor,
5...Fuel supply device, 6...Combustion gas passage, 7...
... Turbine, 8 ... Generator, 9 ... Exhaust duct,
10...Fuel control device, 11...Exhaust gas temperature detector, 12...Turbine speed detector, 13...Compressor discharge pressure detector, 14...Speed setter,
15... Speed regulation rate setter, 16... Proportional controller, 17... Low value selector, 18... Turbine inlet gas temperature estimation device, 19... Temperature setting device, 20...
...proportional-integral controller.

Claims (1)

[Scope of Claims] 1. A speed/load control fuel request signal for controlling the speed or load of the gas turbine to a predetermined value, and a temperature control fuel for controlling the estimated inlet gas temperature of the gas turbine to a temperature set value. In a device for controlling the amount of fuel supplied to a combustor of a gas turbine using a signal having a lower value among a request signal and a signal having a lower value, A first step that takes as input the inlet temperature, inlet pressure, outlet temperature, outlet pressure, turbine speed, and fuel flow rate of a compressor that sends air, and calculates the enthalpy possessed by the air flowing into the combustor of the gas turbine from the outlet temperature of the compressor. a second means for calculating the enthalpy of the gas discharged from the combustor from the enthalpy of the air, the enthalpy of the fuel flowing into the combustor, and the air flow rate and fuel flow rate;
and a third means for converting the enthalpy possessed by the gas discharged from the combustor into the temperature of the gas at the combustor outlet and outputting this as an estimated gas temperature at the inlet of the gas turbine. Characteristic gas turbine control device.