JP2891599B2 - Combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus applied to a two-stage premixed combustor for a gas turbine having a bypass valve for adjusting the amount of compressed air for combustion.

[0002]

2. Description of the Related Art FIG. 8 is a structural view showing an example of a conventional typical two-stage combustion type premixed combustor. In the figure, reference numeral 1 is a pilot combustor, 2 is a main combustor, 3 is a bypass valve, 4
Represents a bypass curved pipe, 5 represents a pilot fuel supply pipe, and 6 represents a main fuel supply pipe.

[0003] This type of combustor is a pilot combustor 1
And a main combustor 2 for generating high-temperature gas mainly at the pilot combustor 1 at the time of low output, and generating high-temperature gas at both the pilot combustor 1 and the main combustor 2 at the time of high output. The bypass valve 3 regulates the air used for combustion, that is, regulates the air supplied to the combustor by bypassing a part of the air to the gas turbine, whereby the ratio between fuel and air is adjusted appropriately. And a stable combustion state is obtained.

In a combustor having such a structure, the ratio between the pilot fuel and the main fuel (referred to as a pilot ratio) and the degree of opening of the bypass valve are properly given to provide
Nitrogen dioxide (NOx) and unburned gas components (UH) in exhaust gas
C) and fluctuations in pressure are kept small, and a good combustion state is maintained.

[0005]

Incidentally, such a combustion state is adjusted at regular inspections, but if the combustion conditions change during operation, a good combustion state cannot be maintained. Changes in combustion conditions include changes in temperature, changes in fuel components, changes in distribution of combustion air (for example, due to changes in the size of the premix nozzle over time), and when these changes occur,
The combustion state may deteriorate, and parts may be damaged due to an increase in harmful gases such as nitrogen dioxide and unburned gas components, and an increase in pressure fluctuation.

The present invention has been made in view of the above circumstances, and even if the combustion conditions change during operation, the combustion is adjusted according to the change to maintain a good combustion state. It is intended to provide a device.

[0007]

According to the present invention, there is provided, in accordance with the present invention, a combustion control apparatus for a two-stage premixed combustor having a bypass valve for adjusting the amount of compressed air for combustion. A pressure fluctuation measuring device for measuring fluctuations, an exhaust gas component measuring device for measuring nitrogen dioxide and unburned gas components in exhaust gas, and a bypass valve when the measured pressure fluctuation, nitrogen dioxide or unburned gas components are above a set value. A signal for controlling the opening degree, a signal for controlling the fuel ratio of the two-stage premixed combustor when the opening degree of the bypass valve exceeds the set width, and a signal for restricting the operation when the fuel ratio exceeds the set width are output. A combustion control device is provided that includes a diagnostic and control signal generator.

[0008]

According to the above means, the pressure fluctuation in the combustor and the nitrogen dioxide and unburned gas components in the exhaust gas are monitored, and when these exceed a set value, the opening of the bypass valve is changed. If the degree exceeds the set range, the fuel ratio is then changed, and if the fuel ratio exceeds the set range, the operation is forcibly limited to maintain good combustion.

[0009]

1 shows an example of the configuration of a combustion control device according to the present invention used in a two-stage combustion type premixed combustor. The combustion control device 10 includes a pressure fluctuation measurement device 11, an exhaust gas component measurement device 12, and a diagnosis and control signal generation device 13.

The pressure fluctuation measuring device 11 can have, for example, the configuration shown in FIG. That is, a conduit 14 having one end communicating with the inside of the pilot combustor 1 at a pressure fluctuation measurement point, and a valve 15 provided at the other end of the conduit 14.
And a pressure sensor 16 attached to the end of the valve 15.
, A preamplifier 17 and a main amplifier 18 for amplifying the output signal of the pressure sensor 16, and a frequency analyzer 19. Valve 15 is a pressure sensor 16
It is arranged so that it can be removed during operation, and may not be necessary.

[0011] The length L of the conduit 14 is as L ≦ c / 6f _H. Here, c is the sound velocity, the f _H is the focused pressure fluctuation frequency (RF). As a result, the length of the conduit 14 is suppressed so that the frequency of the columnar resonance of the conduit 14 becomes 1.5 times or more the frequency of interest, and the measurement accuracy of the high-frequency pressure fluctuation is improved. Can be. And
By using the frequency analyzer 11, a pressure fluctuation level of a dominant frequency is detected.

Returning to FIG. 1, a general nitrogen dioxide meter and an unburned gas component meter are used as the exhaust gas component measuring device 12 of the combustion control device 10. These instruments are attached to a gas turbine exhaust duct, and respectively detect nitrogen dioxide components and unburned gas components in exhaust gas.

The diagnostic and control signal generator 13 comprises, for example, a fast Fourier transformer 20, an analog / digital converter 21, a central processing unit 22, and a digital / analog converter 23. The fast Fourier transformer 20 analyzes the frequency of the pressure fluctuation measured by the pressure fluctuation measuring device 11, and the analog / digital converter 21 converts the nitrogen dioxide component and the unburned gas component measured by the exhaust gas component measuring device 12. This is a device for digitizing levels. The fast Fourier transformer 20 and the analog / digital converter 21 have a diagnostic function together with the central processing unit 22. The state quantities relating to the combustion state obtained by the fast Fourier transformer 20 and the analog / digital converter 21 are shown in FIG. Central processing unit 22 according to the flow shown
And the combustion state is diagnosed. As a result of the diagnosis, a digital / analog converter 23 outputs a bypass valve opening signal 24, a pilot ratio signal 25, and a load signal 26 as control signals for changing operation parameters.

The diagnostic function of the diagnostic and control signal generator 13 will be described with reference to FIG. The diagnostic parameters are nitrogen dioxide NOx, high frequency of pressure fluctuation (for example, 80 to 150).
Hz), the unburned gas component UHC, and the low-frequency (for example, 50 Hz or less) component of the pressure fluctuation.

A threshold value is set for each of these diagnostic parameters, and if the level is equal to or less than the set value, the measurement of the diagnostic parameters is repeated, and good operation is continuously confirmed. If at least one of the diagnostic parameters exceeds the threshold, a bypass valve opening signal 24 for changing the opening of the bypass valve is output as a control signal, and combustion control is performed so that the diagnostic parameter falls within the threshold. .

If the opening of the bypass valve cannot be adjusted within the set width, a pilot ratio signal is output as a control signal, and the pilot ratio is changed to perform the same combustion control.
If the diagnosis parameter does not fall within the threshold value even in the combustion control attempted, the load signal 26 is used as the control signal.
Is output and the operation control is performed so that the diagnostic parameter is suppressed to within a threshold value.

As described above, the combustion state of the two-stage combustion type premixed combustor is monitored using the four parameters, and the combustion state can be adjusted to an optimum state by strictly controlling the ratio of fuel and air. .

As a specific event, as shown in FIGS. 4 and 5, when the air is excessive, the low-frequency pressure pulsation of 10 to 20 Hz increases together with the unburned gas component UHC, while the air becomes insufficient. In this case, the flame temperature rises, the nitrogen dioxide NOx increases, and high-frequency pressure pulsation occurs. Thus, it can be seen that the combustion is inconvenient even if the air amount is large or small. According to the present invention,
The fuel-air ratio (fuel / air ratio) is controlled by the bypass valve opening signal 24 and the pilot ratio signal 25, and a good combustion state is realized.

FIGS. 6 and 7 show data obtained by changing the bypass valve opening and the pilot ratio under an atmospheric pressure state and an 80% load, and almost the same characteristics can be obtained in the actual machine. Thus, the effects of the combustion control device of the present invention are supported.

[0020]

According to the present invention, operating parameters such as a bypass valve and a pilot ratio are continuously measured during operation to measure pressure fluctuations of the combustor, nitrogen dioxide and unburned gas components so as to optimize these parameters. Harmful exhaust gas components such as nitrogen dioxide and unburned gas components can be minimized, and pressure fluctuations in the combustor are reduced, contributing to improved component reliability and longer life. I do.

Further, since the pressure fluctuation of the combustor is continuously measured, it can be used for diagnosis of abnormality of the combustor.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a combustion control device according to the present invention.

FIG. 2 is a system diagram showing an example of a pressure fluctuation measuring device.

FIG. 3 is a flowchart illustrating an example of a diagnostic function of the diagnostic and control signal generator.

FIG. 4 is an explanatory diagram of an optimum operation range showing a change in pressure fluctuation with respect to a fuel-air ratio.

FIG. 5 is an explanatory diagram of an optimum operation range showing a change in exhaust gas with respect to a fuel-air ratio.

FIG. 6 is a diagram of experimental data showing a change in a combustion state with respect to a bypass valve opening adjustment.

FIG. 7 is a diagram of experimental data showing a change in combustion state with respect to pilot ratio adjustment.

FIG. 8 is a structural diagram showing a two-stage combustion type premixed combustor to which the combustion control device according to the present invention is applied.

[Explanation of symbols]

 Reference Signs List 10 Combustion control device 11 Pressure fluctuation measurement device 12 Exhaust gas component measurement device 13 Diagnosis and control signal generation device 14 Conduit 15 Valve 16 Pressure sensor 17 Preamplifier 18 Main amplifier 19 Frequency analyzer 20 Fast Fourier converter 21 Analog / Digital converter 22 Central Processor 23 Digital / analog converter 24 Bypass valve opening signal 25 Pilot ratio signal 26 Load signal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23N 1/02 F23N 1/02 K F23R 3/00 F23R 3/00 E 3/28 3/28 A 3/30 3/30 ( 58) Field surveyed (Int.Cl. ⁶ , DB name) F23R 3/26 F23R 3/00 F23R 3/28 F23R 3/30 F02C 9/00 F02C 9/52

Claims (1)

(57) [Claims] 1. A combustion control device for a two-stage premixed combustor having a bypass valve for adjusting the amount of compressed air for combustion, a pressure fluctuation measuring device for measuring a pressure fluctuation in a pilot combustor, and nitrogen dioxide in exhaust gas. And an exhaust gas component measuring device for measuring unburned gas components, and a signal for controlling the opening of the bypass valve when the measured pressure fluctuation, nitrogen dioxide or unburned gas component is above a set value, and the opening of the bypass valve is set. A diagnostic and control signal generator for outputting a signal for controlling the fuel ratio of the two-stage premixed combustor when the fuel ratio exceeds the width and a signal for restricting operation when the fuel ratio exceeds the set width. Combustion control device.