JPH0697187B2 - Flame monitoring device using optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a flame monitoring device using an optical fiber.

<Prior art and its problems> It is extremely important from the viewpoint of economy and safety to accurately detect the combustion state of various combustion devices including large boilers at business establishments. Taking a large boiler for a power plant as an example, the number of burners installed increases with the capacity of the boiler, the number of burner ignitions and the number of extinguishments increases with the intermediate load operation of the large boiler, and combustion that reduces nitrogen oxides (NOx) Due to the implementation of the method and the change in combustion behavior due to the diversification of fuels, further improvement in the reliability of flame detection of burners is desired.

Here, the flame detector detects the flame by detecting any of the heat, light, and electrical properties of the flame, but the method of detecting the flame by detecting the light is simply the presence or absence of the flame. It is basically possible not only to detect the above, but also to analyze the properties of the flame by analyzing the frequency of the light emitted by the flame, etc., so that a lot of information about the formed flame can be obtained.

The conventional optical flame detector has a heat-resistant mirror or lens arranged at the tip of the head, which is a tubular body, and guides the light detected by these mirrors to the outside of the boiler via the head.
The presence or absence of flame was detected. However, this method
The field of view is limited to one by the angle at which the mirror or lens is attached, and although it is possible to detect a part of the flame, it is not possible to detect the brightness distribution of the entire flame, and to detect the nature of the flame. Was virtually impossible. Further, the narrow field of view makes it difficult to distinguish the light from other flames from the light of the fire of the burner to be detected, and often causes a detection error. Furthermore, due to the implementation of low NOx combustion, a considerable amount of unburned matter floats near the flame formation part, which lowers the permeability of the entire furnace, further reducing the reliability of conventional equipment with a single field of view. It is the actual situation.

<Object of the present invention> In view of the above-mentioned problems, the present invention provides a flame monitoring device capable of accurately detecting a flame and maintaining the device favorably.

<Outline of the Present Invention> In short, the present invention is a flame monitoring apparatus for detecting a wide range of flame light by a plurality of optical fibers and transmitting the light to a predetermined device. And an optical fiber consisting of a cladding part on the outside of the optical fiber. In addition, the lighting fiber is set so that the tip facing the flame is oriented in multiple directions. Is a flame monitoring device using an optical fiber, characterized in that it is configured to fit in the core portion of the rear end of a large diameter optical fiber.

First, prior to describing the embodiments of the present invention, a flame monitoring device capable of suitably implementing the present invention (the present inventors separately apply)
The structure will be specifically described.

In FIG. 2, reference numeral 1 is an outer cylinder constituting the main body of the apparatus, 2
Is a daylighting head mounted in the outer cylinder 1 in the vicinity of the tip through a support member 3. At the tip of the daylighting head 2, three grooves are formed at different angles toward the tip opening 2a, and three daylighting fibers (4a, 4b,
4c), each shown as 4c), and each line 5
It is arranged so as to have a constant visual field centering on a, 5b, and 5c.

Next, reference numeral 6 is an inner cylinder arranged in the outer cylinder 1 through a certain space, 7 is a connector arranged in the inner cylinder 6, and the three light-collecting optical fibers 4 are connected to the outer cylinder via the connector 7. It is taken out through the wind box 8 attached to the base of No. 1. Further, the cooling air A is supplied from the window box 8 to the main body 1 side to cool the optical fiber.

<Examples> Examples of the present invention will be specifically described below.

In FIG. 1, reference numeral 10 is a light-collecting optical fiber (corresponding to those shown as reference numerals 4a, 4b, 4c in FIG. 1) attached to the light-collecting head, and has the largest outer diameter of all the optical fibers, for example, the core. The outer diameter of the cladding 10b formed around 10a is about 800 μm. Next, reference numeral 11 is a relay optical fiber housed in an outer cylinder 1 (see FIG. 1) that constitutes the main body of the monitoring device, and has an outer diameter smaller than that of the daylighting optical fiber 10,
For example, the outer diameter of the cladding 11b is about 500 μm. Here, the diameter of the light-collecting optical fiber is set to be large, in addition to increasing the amount of light to be collected, it is possible to easily connect to the relay optical fiber 11 having a small core that follows, As a result, even if the relay optical fiber is affected by vibration and heat transfer, the end face to which the relay optical fiber 11 is connected is located within the connection side end face of the daylighting optical fiber 10 and enters the daylighting optical fiber. The light is transmitted not to the total amount but to the relay optical fiber at a constant rate depending on the area ratio of the end face of the connection portion, corrects the flame monitoring process by this optical signal, and does not cause malfunction. In other words, these optical fibers are in and out of the device,
Since there is a risk of damage due to heat stress, etc., divide it and connect the end of each fiber, and if damage occurs,
The connection portion of the optical fiber is separated so that only the damaged optical fiber can be replaced. In this case, the replacement work is not always performed in a place where the working environment is good, and if the diameters of the optical fibers are different, the end of the small-diameter optical fiber is the core of the end of the large-diameter optical fiber. Even if the cores are displaced, the contact area between the end portions of both optical fibers is always constant, and the amount of transmitted light is reduced, but the succeeding optical fiber always has the entire connection end surface of the optical fiber ( Since the signal is transmitted via a constant area), the signal becomes highly reliable, so strict centering of both is unnecessary, and the connection work can be simplified. A protective layer 11c made of ethylene tetrafluoride (PTFE) or the like may be formed on the outer peripheral portion of the relay optical fiber 11. Incidentally, since the light-collecting optical fiber 10 receives a considerable amount of heat radiation from the flame, it is desirable not to form a protective layer having not so high heat resistance. Also in the illustrated case, the structure does not have a protective layer.

Next, reference numeral 12 is an optical fiber following the optical fiber 11 for relay, which is smaller in diameter (minimum diameter) than the optical fiber for relay for the same reason as described above. 12a is a protective layer made of synthetic resin such as nylon formed around the optical fiber.

In this way, the optical fibers whose diameters change from large to medium and small are connected to form a unit optical fiber.

It should be noted that this optical fiber is usually composed of a plurality of cables (three in the case of the device of FIG. 1) and is configured as a cable.
It is configured to increase strength.

<Effects> By implementing the present invention, even if a part of the optical fiber is damaged, only the damaged optical fiber can be replaced, which is economical, and the diameter of each fiber is different. Therefore, the connection can be facilitated, the ignition, the combustion, and the misfire of the burner flame can be accurately grasped by the optical signal, and the suitable transmission of the optical signal has the effect of increasing the reliability of the flame monitoring. .

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an optical fiber showing an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a flame monitoring device. 10 …… Optical fiber for lighting 11 …… Optical fiber for relay 12 …… Optical fiber for minimum diameter

Claims (1)

[Claims] 1. A flame monitoring device for detecting flame light at a wide angle by a plurality of optical fibers and transmitting the light to a predetermined device, wherein each optical fiber has a central core portion and a cladding outside the core portion. And a light-collecting optical fiber whose light-receiving tip of each optical fiber faces a flame, and a subsequent optical fiber connected to the light-collecting optical fiber. The fiber is set so that the tip facing the flame is directed in multiple directions, the diameter of the light-collecting optical fiber is made larger than the diameter of the following optical fiber, and the tip of the small-diameter optical fiber is
A flame monitoring device using an optical fiber, characterized in that it is configured so that it can be fitted into the core portion of the rear end of a large-diameter optical fiber.