JPS6280523A - Method and circuit for detecting flame in gas turbine combustor - Google Patents

Abstract

PURPOSE:To detect only either fire selectively by paying attention only to the light emission wavelength of a chemical species that fires feature and monitoring a change in the lapse of time in light emission intensity or a light emission intensity value of each wavelength, etc. CONSTITUTION:A light beam sampled by a fire flame sampling head 6 is inputted to an interference filter 7 through an optical fiber 13. The interference filter 7 transmits only a light beam required for selective fire detection. Then, a filtered light beam is guided to a photodetector 8 through the optical fiber 13 and converted into an electric signal 14, which is monitored by a time-wise judging circuit 11 with time through an amplifier 9 and an integration circuit 10 and the compared with a set value. For example, the integral value of the light emission intensity of 3,880Angstrom generated by the secondary fire occurrence after an ignition time t0 is comapred with a set value and a fire detection signal is generated at time t1 when the integral value exceeds the set value. Then the electric signal 14 is transmitted to a fire occurrence judging circuit 12 to judge whether a fire occurs or not.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a flame detection method and a flame detection circuit in a gas turbine combustor, particularly when a diffusion flame and a premix flame exist simultaneously in the combustor. Alternatively, the present invention relates to a method and a circuit for selectively detecting only one of the flames when a bright flame and a non-bright flame exist at the same time.

[Background of the invention]

Flames radiate wave energy that produces heat and light rays. Approximately 90% of the total radiant energy is consumed by oil combustion, and approximately 90% by gas combustion.
5% belongs to the infrared region of invisible light and is used as heat. The energy in the short wavelength ultraviolet region is 1% or less. Also, it should be noted that objects heated by heat rays also emit visible and infrared rays. A flame detector that detects flame within a gas turbine combustor must distinguish between light emitted from this red-hot object (eg, the combustor inner cylinder) and light emitted from the combustion flame. Therefore, using a gas turbine flame detector in the visible light region or infrared region will result in a loss of operational safety of the gas turbine. The detection methods of flame detectors according to the prior art can be broadly classified into the following six methods.

(1) Bimetal method: The presence of combustion flame is detected by gas temperature.

(2) CdS cell method: The presence of flame is detected as a resistance change due to light.

(3) PbS cell method: The presence of flame is detected as a change in resistance value due to infrared rays.

(4) Phototube method: The presence of flame is detected as the amount of photoelectrons emitted by an object due to light.

(5) Flame Rondo method: The presence of flame is detected as a current value using its properties as a conductor.

(6) Ultra vision method: The presence of flame is detected as the amount of energy only in the ultraviolet region.

The relative sensitivities of these methods by wavelength are shown in FIG.

The flame detection method in the gas turbine combustor is
The ultravision method described in section 6) is commonly used (wavelength: 1900 to 2000 people).

Figure 2 shows the gas turbine combustor flame detection circuit conventionally used in this system. The flame present in the combustor is
The ultraviolet light is sampled directly by the ultraviolet phototube 1 and turned into an electrical signal, which is then sent to a philip-flop circuit 2 to emit a rectangular wave. Then, it is converted into a DC signal by the rectifying circuit 3, integrated by the next integrating circuit 4, and guided to the flame presence/absence judgment circuit 5.
The presence of flame is detected.

Now, in recent years, the world's interest in environmental issues has continued to increase, and the regulatory values for NO8 in exhaust gas released into the atmosphere from gas turbines are no exception, and are becoming increasingly strict.

In order to follow this trend, each company is developing gas turbine combustors with low NO
He's struggling to make it into an x-gen. As a result, the conventional single combustion method has been replaced by a multiple combustion method. A typical example is a low NO8 combustor that uses both diffusion combustion and premix combustion. Therefore, a diffusion flame and a premixed flame (or a bright flame and a non-bright flame) exist simultaneously in the combustor, but the ignition timings of the flames are different for optimization of control. In this case, one of the two flames is present, and it is necessary to confirm the establishment of the other flame in this state, but gas turbine combustors are limited by their high heat capacity and miniaturization.

Since it is compact and both flames are mixed, the conventional technology is affected by one flame and cannot confirm the establishment of the other flame.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks, and also has the same function as the conventional flame detection circuit, so that it can be used in a gas turbine combustor where a diffusion flame and a premixed flame, or a bright flame and a non-bright flame exist simultaneously. flame on either side (e.g.
An object of the present invention is to provide a flame detection method and circuit that can selectively detect only a premixed flame.

[Summary of the invention]

The gist of the present invention is that when two types of flames with different combustion characteristics (diffusion flame and premix flame, or bright flame and non-bright flame) exist simultaneously in a gas turbine combustor, the flame Characteristically having a single or plural chemical species (for example, ○H, CH.

By focusing only on the emission wavelength (3,000 to 6,000 people) of C2, etc.) and monitoring the temporal change in the integrated value of the emission intensity, the emission intensity value for each wavelength, or both, it is possible to detect either one of them. devised a method and detection circuit that can selectively detect flames.

[Embodiments of the invention]

In a gas turbine low NO8 combustor that aims to reduce NOx by distributing the diffusion flame and premixed flame, the chemical species of the premixed flame (○H,
Figure 3 shows typical characteristics of the wavelength and emission intensity of CH, Cx ), and Figure 4 shows typical characteristics of the wavelength and emission intensity of diffusion flame chemical species (○H, CH, Cx ). . Comparing Figures 3 and 4, the premixed flame has a wavelength of 3880
It can be seen that the human CH and the diffusion flame have the characteristic at the wavelength 5160 human 02. Therefore, by monitoring the luminescence intensity of the chemical species, the presence of the flame can be detected.

If the above premixed flame is filtered using an interference filter having a transmittance as shown in FIG. 5, the emission characteristics shown in FIG. 6 can be obtained. Conversely, for a diffusion flame, an interference filter as shown in FIG. When filtering is performed, the emission characteristics shown in FIG. 8 are obtained. When comparing luminescent flames and non-luminous flames, the most important feature that distinguishes them is that luminous flames have luminescent properties emitted from Cz chemical species with a wavelength of 5160 people, which is close to visible light. That's what it means.

FIG. 9 shows typical luminescent characteristics of a luminescent flame, and FIG. 10 shows typical luminescent characteristics of a non-luminescent flame. Therefore, for the above luminous flame.

If an interference filter having a maximum transmittance characteristic near 5160 people is used, it becomes possible to detect the presence of a luminous flame. If this method is applied, it becomes possible to detect one of the flames with different light emission characteristics.6 Figure 11 shows a typical structural diagram of a low NO8 combustor for natural gas firing. The inner cylinder 16 is disposed inside the combustor casing 20, the outer cover 21, and the front cover 22, and is composed of a head combustion chamber 17, a rear combustion chamber 18, and a cone 23, and is connected to the tail cylinder 19 on the downstream side. The fuel nozzles are connected to each other, and have a primary fuel nozzle 24 and a secondary fuel nozzle 25 as fuel nozzles.As for flame characteristics, the primary flame is a diffusion flame, and the secondary flame is a premixed flame. As a flame detector.

A frame sampling head (having an optical lens, an optical fiber, and a cooling mechanism if necessary) 6 is installed at the rear of the outer cylinder 21, and an optical fiber 13 is connected thereto. The location where the flame detector is installed is just an example, and is not limited to this location.

In the combustor, fuel control as shown in FIG. 12 is performed to optimize N08 control. The primary fuel F1 is injected into the gas turbine at a rotational speed of 20% and ignited by the ignition plug.

The gas turbine is operated up to 25% load. The length of this primary flame varies depending on the combustion state, and the flame exists up to the wake. At a gas turbine load of 25%, secondary fuel Fz is injected, heated to a temperature higher than the self-ignition temperature by the secondary flame, and ignited. The establishment of this secondary flame (premixed flame) is detected by the present invention.

FIGS. 13, 14, and 15 show representative examples of the gas turbine combustor flame detection circuit according to the present invention. In FIG. 13, sampled by flame flame sampling head 6, the beam is introduced through optical fiber 13 to interference filter 7. The interference filter 7 is
Chemical species C characteristically possessed by secondary flame (premixed flame)
It has the function of transmitting only the 3880 wavelengths of light that H has.

Only the light beam necessary for selective flame detection is transmitted to the wake. The filtered light beam passes through the optical fiber 13 (although it is not necessarily necessary to pass through the optical fiber), is guided to the light receiver 8, and is converted into an electrical signal 14. This signal 14 is amplified by an amplifier 9, integrated by an integrating circuit 10, and firstly, the integrated amount is monitored over time by a temporal judgment circuit 11 and compared with a set value. Temporal judgment circuit 11
The monitoring function is shown in FIG. 16. In this embodiment, there is a function for detecting the secondary flame fz (premix flame) generated by the secondary fuel F2, and the ignition time t.

The integral amount of emission intensity of 3880 wavelengths generated by the establishment of the secondary flame of the paper machine is compared with a set value, and a flame detection signal is generated at time t1 when the set value is exceeded.

This electric signal 14 is transmitted to the flame presence/absence judgment circuit 12, and a judgment is made as to whether or not there is a flame.

In FIG. 14, the electric signal 14 that has been processed in the same manner as in FIG. 13 enters the wavelength-specific judgment circuit 15 from the amplifier 9, and the corresponding light emission intensity is determined by wavelength (in this example, the light emission intensity of 3880 people with a wavelength) is monitored and compared with the set value. The monitoring function of the wavelength-based judgment circuit 15 is shown in FIG. 17. In this embodiment, the monitoring function of the wavelength-specific judgment circuit 15 is shown in FIG. The light emission intensity value generated after establishment is compared with the set value, and when the set value is exceeded, a flame detection signal is issued. This electric signal 14 is transmitted to the flame presence/absence judgment circuit 12, and a judgment is made as to whether or not there is a flame.

FIG. 15 shows a flame detection circuit that improves the reliability of flame detection by using both the circuits shown in FIGS. 13 and 14 in combination. It is also possible to selectively detect only the primary flame (diffusion flame) using the same method and circuit (monitoring the 5160-wavelength light beam of the chemical species Cz). The same applies to a method and a circuit for selectively detecting only one of flames in a gas turbine combustor where flames and non-luminous flames exist at the same time.

〔Effect of the invention〕

Lower NOx can be achieved by distributing the diffusion flame and the premix flame. Not only in gas turbine low NOx combustors, but also in gas turbine combustors where bright flame and non-bright flame exist at the same time.
It is now possible to selectively detect only one of the required flames, which has the effect of dramatically improving the safety of gas turbine operation.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relative sensitivity of various flame detectors according to the prior art to each wavelength, Figure 2 is a diagram of a conventional flame detection circuit in a gas turbine combustor, and Figure 3 is a diagram of a premixed flame detection circuit. Figure 4 is a typical characteristic diagram of each wavelength and emission intensity of chemical species possessed by a diffusion flame. Figure 5 is an interference filter used for premix flame detection. Figure 6 is a characteristic diagram showing the relationship between the wavelength of the light beam filtered by the interference filter and the emission intensity. Figure 7 is the transmittance characteristic diagram of the interference filter used for diffusion flames. Figure 8 is the transmittance characteristic diagram of the interference filter used for diffusion flame. is a characteristic diagram showing the relationship between the wavelength of the light beam filtered by the interference filter and the emission intensity,
Figure 9 is a typical characteristic diagram of each wavelength and luminescence intensity of chemical species possessed by a luminescent flame, Figure 10 is a representative characteristic diagram of each wavelength and luminescence intensity of chemical species possessed by a non-luminous flame, and Figure 11 is a representative characteristic diagram. low NOx
A cross-sectional view showing the structure of the combustor, Figure 12 is a typical low-N
Fuel control schedule diagram of Ox combustor, Fig. 13, Fig. 1
4 and 15 are block diagrams of the flame detection circuit in the gas turbine combustor according to the present invention, FIG. 16 is an explanatory diagram of the operation of the temporal judgment circuit according to the present invention, and FIG. 17 is the wavelength diagram according to the present invention. FIG. 6 is an explanatory diagram of the operation of the separate determination circuit. 6... Frame sampling head, 7... Interference filter, 8... Light receiver, 9... Amplifier, 10...
Integral circuit, 11... Judgment circuit, 16... Inner cylinder, 17
...Head combustion chamber, 18...Rear combustion chamber, 24...
Primary fuel nozzle, 25... secondary fuel nozzle.

Claims (1)

[Claims] 1. In a gas turbine low NO_x combustor that aims to achieve low NO_x by distributing diffusion flames and premixed flames, when both flames exist, one of the flames A method for detecting a flame in a gas turbine combustor, characterized in that the intensity of light having a characteristic emission wavelength of a chemical species is detected and compared with a predetermined set value to determine the presence or absence of the flame. 2. The light sampled from the frame sampling head is transmitted through an optical fiber, filtered by an interference filter that matches the emission wavelength band of a characteristic single or multiple chemical species, and then converted into a received light signal by a light receiver and amplified. After being amplified by a filter, the gas is transmitted to an integrating circuit, the integrated amount of the emitted light intensity is led to a time-dependent judgment circuit, and the presence or absence of a flame is detected by comparing the integrated amount with respect to time and a set value. Turbine combustor flame detection circuit.