JPS6298117A - Flame detector - Google Patents

Abstract

PURPOSE:To enable detection of a burner flame and an ignition torch flame through a single flame detector with high precision, by a method wherein a photo signal from a light guiding part having a plurality of detecting visual fields is photoelectrically converted by a plurality of wavelengths, and with regard to each signal, the presence of flame classified by a visual field is judged. CONSTITUTION:A flame detector head part 8 is so set that, by the use of a flame detector having a plurality of different visual fields 7, at least one visual field can detect an ignition torch flame 4 and at least one visual field can detect a burner flame 2 without being interfered by the ignition torch flame 4. The head part 8 has a mount part 6 to which an optical fibre 6 is mounted. In a photo signal guided through the optical fibre 6 from two or more different visual fields 7, its short wavelength component is first absorbed by an Si photo diode 12 at an upper layer, a long wavelength component permeates and is absorbed by a PbS photo conductor 13 at a lower layer. As noted above, a photo signal is converted into two electric signals classified by wavelength by means of photoelectric conversion elements 2 and 3, and are inputted to a computing part having decision logic, and flame can be sharply distinguished for highly precise detection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion device, and particularly relates to a flame detector that can determine the flames of both burners and ignition torches with a single detector when the types of fuel are different. It is something.

[Conventional technology and problems to be solved] In recent years, the need for low NOx combustion has increased in power utility boilers, and strong swirling is often applied to the secondary and tertiary air of combustion burners. There is a tendency for mutual interference between flames to increase and positional fluctuations of flames to be detected to increase. In particular, if the main burner and ignition torch use different types of fuel, the emission wavelength range and emission intensity will vary depending on the fuel type.
Interference with other burner flames (particularly the ignition torch flame) due to changes in the position of the flame greatly affects the detection accuracy of the flame detector.

For example, if the main burner's fuel type is gas and the ignition torch's fuel type is light oil, then comparing the light emission intensities of the gas and light oil flames by light emission wavelength using the flame flicker characteristics:
As shown in Figures 7 and 8, the emission intensity (42) of gas is very low in the visible wavelength range compared to the emission intensity (41) of diesel oil, making it impossible to detect gas flames in the visible wavelength range. (7th Fi, /l), and in the infrared wavelength range, although the gas flame generation intensity (42) increases compared to the visible wavelength range, the light oil flame emission intensity (41) is still greater. (Figure 6).

The light receiving elements for each wavelength range are Si (silicon photodiode) for the visible wavelength range and P6S for the infrared wavelength range.
A photoconductor is used.

In this way, the emission intensity of the ignition torch flame is greater than the emission intensity of the burner flame over the visible to infrared wavelength range, so if the ignition torch flame is present in the field of view of the burner flame detector due to the flame position change, , there is a risk that a false signal indicating ignition may be output even when the burner is extinguished.

Therefore, even when the burner and ignition torch have different types of combustion, especially when the emission intensity of the ignition 1--1 flame is greater than the emission intensity of the burner flame, each flame can be detected accurately. A detector is required.

The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to provide a burner and an ignition torch in which the fuel types are different.

In particular, even when the emission intensity of the ignition torch flame is greater than the emission intensity of the burner flame, each flame can be clearly distinguished and detected with high accuracy. An object of the present invention is to provide a flame detector capable of making a flame determination.

[Means for solving problems]

In order to achieve the above object, the flame detector according to the present invention includes:
Optical signals from a light guide having a plurality of detection fields of view are photoelectrically converted for each of a plurality of wavelengths, and the presence or absence of a flame is determined for each detection field of view for each signal after photoelectric conversion.

The present invention will be explained in detail below based on examples.

〔Example〕

The positional relationship between the burner flame and the ignition torch flame in the combustion device is generally as shown in FIG. here,
The fuel type of the ignition torch 3 is light oil, and the fuel type of the burner 1 is gas.

First, in order to detect the flames of both the burner 1 and the ignition torch 3 (burner flame 2 and ignition torch flame 4), a flame detector head with two or more different fields of view 7 as shown in FIG. 1 is used. As shown in FIG. 3, at least one of the two or more different fields 7 can see the ignition torch flame 4, and at least one field can see the burner flame 2 without interference from the ignition torch flame 4. Set the flame detector rad part 8 so that it can be detected. An optical fiber 6 is attached to the mount section 6 of the head section 8 .

The optical signals guided by the optical fiber 6 from two or more different fields of view 7 are transferred to a photoelectric conversion element for visible wavelengths (Si photodiode) and a photoelectric conversion element for infrared wavelengths, as shown in FIG. By using a photoelectric conversion element with a stacked structure of PbS photoconductor), the short wavelength component is first absorbed by the Si photodiode 12 in the upper layer, and the long wavelength component is transmitted and transmitted to the PbS light in the lower layer. It is absorbed by the conductor 13.

In this way, the optical signal is converted into two wavelength-specific electric signals by the photoelectric conversion element 2.3, and then, by the determination logic shown in FIG. The electrical signal is detected in the comparator 16 and in the infrared wavelength range, i.e. in the PbS photoconductor 1.
The electrical signal converted by 3 is compared with a threshold value in a comparator 17. The threshold value compared by the comparator 16 is a signal level in the visible wavelength range for determining whether the ignition torch is turned on or extinguished, while the threshold value compared by the comparator 17 is used to determine whether the burner is turned on or extinguished. This is the signal level in the infrared wavelength range for FIG. 8 shows the threshold value (27) and current value (30) for the visible wavelength range, and the threshold value (28) and current value (29) for the infrared wavelength range. This threshold (27), (28)
The signal compared with is converted into an ON/OFF signal which is 1 if it is larger than the threshold value and 0 if it is smaller than the threshold value.

First, the logic for determining whether to turn on or off the ignition torch at 0UTI (Figure 5) is based on visible and infrared wavelength signals for each field of view (for example, visible signal 5i (21) and infrared signal R (24)).
If there is even one field of view where both are larger than the threshold value 27.28, the AND circuit 18 outputs an ignition signal via the OR circuit 20.

Therefore, as shown in FIG. 6, the ignition torch ignition signal is output only when both the infrared and visible signals take values greater than their respective thresholds.

In addition, the logic for determining whether to turn on or extinguish the burner in 0UT2 (Fig. 5) is based on the fact that the flickering output of the gas flame in the visible wavelength range is almost equal to zero, as shown in Fig. 7. For example, visible signal 52 (22)
) is lower than the threshold value 27 and if there is even one field of view where the signal in the infrared wavelength range (for example, the infrared signal R, (25)) is higher than the threshold value 28, the NOT circuit 19 ,A
An ignition signal is output by an ND circuit 18 and an OR circuit 20. Therefore, as shown in FIG. 6, the burner ignition signal is output only when only the signal in the infrared wavelength range exceeds the threshold value.

In addition, both infrared and visible signals (for example, visible signal S,
(23) and the infrared signal R, (26)) take values smaller than their respective threshold values (see FIG. 6), it is easily determined that neither of the above cases is the case.

In this way, when the burner and ignition torch have different types of combustion, especially when the emission intensity of the ignition torch flame is greater than the emission intensity of the burner flame, it is possible to use a photoelectric conversion element that can discriminate between multiple fields of view and multiple wavelength ranges. By using the arithmetic unit and having the determination logic, it is possible to distinguish between the flames of both the burner and the ignition torch with a single flame detector and detect them with high accuracy.

〔Effect of the invention〕

As described in detail above, according to the present invention, when using different types of fuels that often cause erroneous detection due to interference with other burner flames, especially when the emission intensity of the ignition torch flame is greater than the emission intensity of the burner flame, the burner It becomes possible to accurately distinguish and detect the flame and the ignition torch flame. Also,
Conventionally, two flame detectors were required, one for the burner and one for the ignition torch, but it is now possible to detect both flames with one flame detector, which is economical.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a flame detector head in an embodiment of the present invention, Fig. 2 is a diagram showing the positional relationship between the ignition torch flame and burner flame, and Fig. 3 is a diagram showing the detection field of view in the flame detector head. FIG. 4 is a cross-sectional view showing the photoelectric conversion element in the flame detector head, FIG. 5 is a diagram showing the flame determination logic in the above embodiment, and FIG. 6 is a diagram showing the visible wavelength range and infrared wavelength range. FIGS. 7 and 8 are diagrams showing the flicker characteristics of a passing flame and a gas flame, respectively. 1... Burner, 2... Burner flame, 3... Ignition torch, 4... Ignition torch flame, 5... Optical fiber,
6... Mount part, 7... Field of view, 8... Flame detector head part, 11... Optical signal, 12
...Si photodiode, 13...pbs photoconductor, 16.17... comparator,
18...AND circuit, 19...NOT circuit, 20.
...OR circuit, 21.22.23...visible signal. 24.25.26...Infrared signal, 27.28...Threshold value, 29.3o...Current value.

Claims (1)

[Scope of Claims] 1. A flame detector for determining whether to turn on or off a burner flame and an ignition torch flame of a combustion device using one detector, which comprises an optical transmission line having at least two or more different detection fields of view. A photoelectric conversion section having a light guide section and converting an optical signal from the optical transmission line into an electrical signal in two or more different wavelength ranges, and determining the presence or absence of flame for each signal after photoelectric conversion according to the detection field of view. A flame detector characterized in that it is equipped with an arithmetic processing unit that performs. 2 Among the two or more different detection fields, at least one detection field is set at a position where the ignition torch flame can be detected, and at least one detection field is set at a position where the burner flame can be detected without interference from the ignition torch flame. The flame detector according to claim 1, wherein the flame detector is set at a position where it can be detected. 3. When the fuels of the ignition torch and the burner are different, the arithmetic processing unit utilizes the difference in the emission intensity and emission wavelength range of each, and uses the wavelength-specific signals compared by the wavelength-specific thresholds. 2. The flame detector according to claim 1, wherein the flame detector is configured to determine flame by field of view.