JP2006058165A - Flame detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame detector for reducing cost by a large amount and preventing optical fiber from being damaged, by simplifying the structure of the optical fiber at a lighting section and composing the flame detector by a single optical fiber having the same diameter regarding the transmission direction of light. <P>SOLUTION: The flame detector comprises a lighting section for receiving the flame light of a combustion apparatus, having a plurality of burners via a plurality of optical fibers, and a transmission section made up of an optical fiber for transmitting light from the optical fiber of the lighting section to an analyzer. In the flame detector, the plurality of optical fibers of the lighting section comprise a central optical fiber and a plurality of optical fibers, in which the tip section is bent radially toward the flame light to the central axis of the optical fiber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flame detector, and more particularly to a multi-view type flame detector using a plurality of optical fibers used in a combustion apparatus such as a business boiler.

A flame detector is a device that determines whether a burner is ignited or extinguished in a combustion apparatus such as a business boiler. It accurately diagnoses the presence / absence of a flame, the degree of combustion, and the determination of the state of combustion. Is important. For example, in the case of determination of the presence or absence of a flame, if a flame is already formed in the combustion furnace, but it is determined that there is no flame, the supply of fuel to the boiler is stopped and the fire is extinguished. On the other hand, when it is determined that a flame is formed even though there is no flame, fuel is supplied to the boiler, and there is a risk of combustion explosion. As described above, the performance of the flame detector greatly affects the combustion control.
In the case of flame detectors for large boilers for power plants, increase the number of burners as the capacity of the boiler increases, increase the number of burner ignition / extinguishment associated with intermediate load operation, and implement a combustion method that reduces nitrogen oxides (NOx) Furthermore, further improvement in the performance of the burner flame detector is desired due to changes in combustion behavior accompanying the diversification of fuel.

  Under such circumstances, a flame detection apparatus using a plurality of optical fibers is known as a conventional technique, and this apparatus is compared with a flame detector that receives a flame only from a single direction in the past. Excellent in terms of reliability and performance.

  FIG. 5 shows a flame detector using a plurality of optical fibers according to the prior art. This flame detector includes a flame detector main body 16 that detects the flame light 19 of the burner 18 with an optical fiber, a daylighting unit 17 provided at the tip thereof, and an optical fiber that transmits light collected by the daylighting unit 17. 15 and an analyzer 21 connected to the optical fiber 15 via a transmission optical fiber cable 20. The optical fiber 15 is inserted into the flame detector main body 16, and the tip of the optical fiber is located in the daylighting unit 17. The analysis device 21 includes a photoelectric converter 22 that converts an optical signal into an electrical signal, an amplifier 23 that amplifies the electrical signal, and an arithmetic circuit 24 that detects the presence or absence of a flame based on the electrical signal, and outputs the presence or absence of a flame. Is configured to do.

6A and 6B are explanatory diagrams of the flame detector main body 16, in which FIG. 6A is an enlarged view of the optical fiber of the daylighting unit 17, and FIG. 6B is a view of the connector part of the optical fiber daylighting unit and the transmission unit. A cross-sectional view is shown. As shown in FIG. 6A, the optical fiber in the daylighting unit 17 has an angle sequentially with θ1 and θ2 with respect to a single optical fiber without bending so that light can be collected at a wide angle. It is comprised from the optical fiber 15a, 15b, 15c bent into.
Moreover, the diameter of the optical fiber used by the lighting part 17 and the flame detector main body 16 is different as shown in FIG. 6 (b). A fiber 26 is used, and an optical fiber 27 having a small diameter is used in the optical transmission unit. As described above, the conventional flame detector has a configuration in which a connector is used to connect a plurality of optical fibers so that the diameter of the optical fiber is sequentially reduced with respect to the light transmission direction. In addition, 26a, 26b, and 26c show the flame light structurally.
Japanese Patent Publication No. 3-74775 Japanese Patent Publication No. 6-97187

  However, the conventional flame detector using a plurality of optical fibers has a complicated structure as described above and is expensive, so it is only used in large-scale power generation plants. Other unreliable flame detectors are used. Some of these plants are operated with the flame detection function excluded due to misdetection of the flame, which is an operational problem. Therefore, in small and medium-sized power plants, there is a long-awaited flame detector that reduces costs and improves performance by simplifying the structure of high-performance flame detectors that use multiple optical fibers. It had been.

In the conventional flame detector, as shown in FIG. 6 (a), the plurality of optical fibers arranged in the daylighting portion of the flame detector give a function of detecting the flame over a wide angle, so that there is no bending. The optical fibers 15a and 15b bent to have an angle of θ1 and θ2 (> θ1) with the 0 ° optical fiber 15c as a reference are arranged. For this reason, an optical fiber bent at a large angle, such as θ2, has a higher transmission loss than the optical fiber that has not been bent, and the strength of the bent portion is reduced. When air is not supplied and, for example, the lighting part is exposed to a high temperature, the bent part is easily damaged. In addition, thermal processing is mainly used to bend the optical fiber. In this case, as the bending angle increases, the processing operation becomes difficult, resulting in a large loss in the manufacturing process.
Further, in the above-described prior art, since the optical fibers 26 and 27 having different diameters are connected to each other, the structure becomes complicated, an expensive cost is required, and transmission loss at the connection portion increases. Further, in a flame detector used in the vicinity of a high-temperature burner, the connection portion of these optical fibers is easily damaged.

  The object of the present invention is to simplify the optical fiber structure of the daylighting unit while maintaining the same functions as in the past, and to construct a single optical fiber having the same diameter in the light transmission direction. It is an object of the present invention to provide a flame detector which can be reduced and less susceptible to damage to optical fibers.

The above object is achieved by a flame detector having the following characteristics.
(1) A transmission comprising a daylighting unit that collects flame light from a combustion apparatus having a plurality of burners via a plurality of optical fibers, and an optical fiber that transmits light from the optical fiber of the daylighting unit to the analyzer. A plurality of optical fibers of the daylighting unit, the optical fiber serving as the center, and the distal end portion of the optical fiber with respect to the central axis of the optical fiber is radially bent toward the flame light. A flame detector comprising a plurality of optical fibers.
(2) The flame detector according to (1), wherein the radially bent optical fiber is arranged symmetrically with respect to the central optical fiber.

(3) The flame detector according to (1) or (2), wherein the flame detector is configured by optical fibers having substantially the same diameter from the daylighting unit to the subsequent transmission unit.
(4) The analyzer includes a flame determination unit having a photoelectric conversion element that detects a flame property of each burner, and is configured by optical fibers having substantially the same diameter from the daylighting unit to the flame determination unit. The flame detector according to any one of (1) to (3).

[Action]
In this flame detector, the burner flame light collected in the daylighting section at the detector front end is transmitted to the photoelectric converter through the same diameter optical fiber. In the daylighting unit, it is possible to detect the flame light at a wide angle with the minimum bending angle of the optical fiber. Thereby, the stress applied to the bent portion of the optical fiber can be suppressed, and the optical transmission loss due to the bending can be minimized. In addition, by adopting the same-diameter optical fiber, there is no optical transmission loss at the connection portion as in the conventional case, so that more accurate flame detection is possible.

  According to the present invention, in a flame detection device that detects a burner flame using a plurality of optical fibers, the transmission loss of light is greatly reduced compared to the conventional case, and the stress on the bent portion of the optical fiber is reduced. Therefore, the strength can be improved and the reliability as a product can be further improved.

Examples of the present invention will be specifically described below.
FIG. 1 is an explanatory diagram of a flame detector showing an embodiment of the present invention. 6 differs from the conventional apparatus of FIG. 6 in that the bent portions 5a and 5c of the daylighting optical fiber of the daylighting unit 17 are radially (wide angle) toward the flame light around the straight optical fiber 5b (of the optical fiber 5b). The optical fibers 5a, 5b, and 5c are arranged with cables 5 having the same diameter, as shown in FIG. 2, and the optical fibers 5a and 5b are arranged symmetrically with respect to the central axis. The protective coating material 8a is removed only at the tip of 5c.

  The outer cylinder 1 of the detector body 16 is made of a corrosion-resistant and heat-resistant material, such as stainless steel, having sufficient heat resistance to hold the member housed therein from the high heat generated by the burner flame. The outer cylinder 1 has a daylighting head 2 attached to the outer cylinder 1 via a support member 3 in the vicinity of the tip thereof. The support member 3 also plays a role of protecting the daylighting head 2 from high heat, and is made of ceramics or the like from the viewpoint of heat resistance. Further, three grooves are formed at different angles toward the distal end opening 4 at the distal end of the daylighting head 2, and three optical fibers for light collection (5a, 5b, 5c) are provided in each groove. The optical fibers 5a and 5b are symmetrically arranged on both sides of the optical fiber 5b so as to maintain angles θ1 and θ2 from the central axis and have a constant field of view. 6a, 6b, and 6c schematically show the flame light of the burner. Further, as shown in FIG. 2, each of these optical fibers is composed of one cable having the same diameter, and only the tip portion is not provided with the protective covering material 8a. This protective covering material 8a is a covering layer for maintaining the bending and tensile strength of the optical fiber, and is made of tetrafluoroethylene (PTFE) or the like. In these protective coating materials, even those having high heat resistance are around 250 ° C., and therefore, in the daylighting portions where heat resistance of 400 to 500 ° C. or more is required, as shown in FIG. Therefore, it is desirable to use only the core portion 8b and the cladding portion 8c that can withstand temperatures of 1000 ° C. or higher.

  Next, these optical fibers 5 reach the window box 7 (FIG. 1) attached to the base of the outer cylinder 1 as it is, are connected to an optical cable, and flame information is sent to the subsequent photoelectric converter and analyzer. It has become. The overall structure is shown in FIG. The wind box 7 is used for supplying cooling air, and the cooling air A that has partially entered the wind box 7 passes through the outer cylinder 1, partly from the surroundings of the daylighting head 2, and the other is supported by the daylighting head. The air is blown out from the periphery of the member 3 to cool the main body and the optical fiber housed inside. Further, by storing the photoelectric converter 10 in the window box 7, each optical signal transmitted by each optical fiber in the box is converted into an electric signal, and the subsequent flame determination is performed up to the amplifier 11. It is good also as a structure which employ | adopts the electric wire cable 12 to the apparatus 13, and outputs with an electrical signal.

Here, each optical fiber (6a, 6b, 6c) arranged in the daylighting unit has an optical fiber 6b whose center is bent at 0 ° and an optical fiber 6a which is bent at an angle θ1 symmetrically in the lateral (or vertical) direction. By disposing 6c, a wide-angle flame detector is possible.
By simplifying the structure and reducing the bending angle of the optical cable in this way, more efficient daylighting is possible, and the same bent optical fiber can be manufactured and no connection part is required. A significant reduction in terms of area is possible.

  A comparison between the present invention and conventional lighting efficiency and cost is shown in FIGS. FIG. 4A shows a comparison of the daylighting efficiencies of the optical fibers 5a, 5b and 5c of FIG. 1 with the daylighting efficiencies of the conventional optical fibers 15a, 15b and 15c of FIG. It can be seen that the daylighting efficiency of the optical fiber of the present invention is higher in average than the conventional optical fiber, and the equipment cost is significantly reduced as shown in FIG.

  It is useful as a multi-view flame detector for combustion equipment such as commercial boilers.

Sectional drawing of the flame detector which shows the Example of this invention. Sectional drawing of the lighting part optical fiber currently used for FIG. The system diagram which shows the usage example of this invention apparatus. The comparison figure of this invention and the conventional lighting efficiency and cost. The system diagram of the conventional flame detector. Sectional drawing of the flame detector main body and lighting part optical fiber used in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder, 2 ... Daylighting head, 3 ... Supporting member, 4 ... End opening part, 5a, 5b, 5c ... Optical fiber for lighting, 6a, 6b, 6c ... Flame light, 7 ... Wind box, 8a ... Protective coating Material: 8b ... Core part, 8c ... Cladding part, 10 ... Photoelectric converter, 11 ... Amplifier, 13 ... Analyzer, 16 ... Flame detector main body, 17 ... Daylighting part.

Claims (4)

A daylighting unit for collecting flame light of a combustion apparatus including a plurality of burners through a plurality of optical fibers, and a transmission unit including an optical fiber for transmitting light from the optical fiber of the daylighting unit to the analyzer In the flame detector provided, the plurality of optical fibers of the daylighting unit include an optical fiber that is a center, and a plurality of optical fibers whose distal end portions are bent radially toward the flame light with respect to the central axis of the optical fiber. A flame detector comprising an optical fiber of a book. The flame detector according to claim 1, wherein the radially bent optical fiber is disposed symmetrically with respect to the central optical fiber. The flame detector according to claim 1, wherein the flame detector is configured by optical fibers having substantially the same diameter from the daylighting unit to the subsequent transmission unit. The analysis apparatus includes a flame determination unit having a photoelectric conversion element that detects a flame property of each burner, and is configured by optical fibers having substantially the same diameter from the daylighting unit to the flame determination unit. Item 4. The flame detector according to any one of Items 1 to 3.

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