JPH11237287A - Temperature distribution measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the temperature at a local high temperature part of an object by winding an optical fiber sensor, obtained by bonding a single optical fiber onto a supporting member in ring shape, around an object and measuring the backscattering light of the optical fiber. SOLUTION: An optical fiber 1 is coiled by several turns with diameter D of about 60 mm and bonded onto a thin plate 7 of copper, nickel, or the like, having width W of about 70 mm at an interval L of about 600 mm in the longitudinal direction to form an optical fiber sensor 8. The sensor 8 is then wound round a high temperature piping (object) A at a specified interval and backscattering light is measured thus measuring temperature distribution at each position of the piping A by means of a temperature distribution meter 2. When a sensor 8 comprising an optical fiber 1 turned twice with diameter D of about 60 mm is used, for example, total length of the fiber 1 exceeds 3 m at a local high temperature part (hot spot) 6 of 100 deg.C and a highest temperature part of about 100 deg.C can be detected. Temperature can be measured even when the area of high temperature part of object A is small and the temperature increases locally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature distribution measuring device for measuring the temperature of each part of an optical fiber by analyzing Raman scattered light of the optical fiber.

[0002]

2. Description of the Related Art In this type of temperature distribution measuring device, laser pulse light is incident from one end of an optical fiber. Then, Raman scattered light is generated in the optical fiber, and returns to the incident end again as back scattered light. The relationship of the following equation (1) is established between the intensity ratio and the temperature of the Stokes light and the anti-Stokes light of the backscattered light.

T = −hcv / k · log (Ias / αIs) (1) T: absolute temperature, h: Planck constant, c: speed of light in vacuum,
k: Boltzmann's constant, Ias: anti-Stokes light intensity, Is: Stokes light intensity, α: correction coefficient, ν: Raman shift amount The time from when the pulsed light is incident until the scattered light returns is the pulsed light. The measurement position can be known from that time. This relationship is given by the following equation (2).

L = C0 t / 2n (2) L: distance, C0: speed of light in vacuum, n: refractive index of optical fiber t: delay time from pulse incident to receiving scattered light Here, distance L The resolution can be improved by measuring a small interval of the delay time t from the incidence of the pulse to the reception of the scattered light. For this purpose, the width of the pulse incident light may be reduced, but in this case, the intensity of the scattered light is reduced, so that the distance resolution is limited.

FIG. 4 is a diagram showing a test situation of a distance resolution with respect to the temperature of an optical fiber by a temperature distribution measuring device using the above principle. In FIG. 4, 1 is an optical fiber,
2 denotes a temperature distribution measuring instrument, and 3 denotes a constant temperature furnace. The inside temperature of the constant temperature furnace 3 is controlled to be constant at 100 ° C., and the length between l 1 and l 2 of the optical fiber 1 inserted into the constant temperature furnace 3 is 3 m.
2m, 1m and 0.5m, temperature distribution measuring instrument 2
Is used to measure the temperature distribution at each length.

FIG. 5 is a diagram showing the results of the distance resolution test. The horizontal axis represents the measurement position with the center of the optical fiber 1 in the constant temperature furnace 3 as 0 point, and the vertical axis represents the optical fiber 1 in the constant temperature furnace 3. The temperature measurement results when the lengths are 3 m, 2 m, 1 m and 0.5 m are indicated by 3 L, 2 L, 1 L and 0.5 L, respectively. As can be seen from FIG. 5, the center of the optical fiber 1 shows 100 ° C. only when the optical fiber 1 is placed 3 m into the constant temperature furnace 3 (3 L). The value is lower than 100 ° C. Thus, it can be seen that the optical fiber 1 has poor local temperature detection ability.

FIG. 6 is a diagram showing an apparatus for monitoring abnormalities in a high-temperature pipe, which is an application example of a conventional temperature distribution measuring method using an optical fiber. In FIG. 6, 4 is a steel tube, 5 is a heat-resistant material, G
Denotes a high-temperature gas, and 6 denotes a local high-temperature portion (hereinafter, referred to as a hot spot). In FIG. 6, since the high-temperature gas G flows inside the high-temperature pipe A, the steel pipe 4 is protected by attaching the heat-resistant material 5. However, if the heat-resistant material 5 is cracked or peeled, the steel tube 4 is damaged.
Is wrapped around a steel tube 4, and the temperature of the high-temperature pipe is monitored by the temperature distribution measuring device 2.

[0008]

When a crack or peeling occurs in the heat-resistant material 5 of the high-temperature pipe A shown in FIG. 6, a hot spot 6 is generated on the surface of the steel pipe 4. An abnormality is detected by measuring the rise in the temperature of the optical fiber 1 in that portion with the temperature distribution measuring device 2. However, when the area of the hot spot is small and the temperature is locally increased, the optical fiber 1 has a poor local temperature detection capability as described above.
There is a problem of overlooking abnormalities. An object of the present invention is to provide a temperature distribution measurement device capable of measuring the temperature of a local high-temperature portion of a measurement target.

[0009]

Means for Solving the Problems To solve the above problems and achieve the object, a temperature distribution measuring device of the present invention is configured as follows. (1) A temperature distribution measuring device according to the present invention includes: an optical fiber sensor formed by forming one optical fiber into a plurality of rings and affixing the optical fiber sensor to a support member;
Measuring means for measuring the temperature distribution with respect to the position of the measurement target by measuring the backscattered light of the optical fiber. (2) The temperature distribution measuring device according to the present invention is the device described in (1) above, wherein the optical fiber sensor is formed by winding the optical fiber into a ring shape having a predetermined diameter and a predetermined number of times. Attached at predetermined intervals along the direction.

[0010]

FIG. 1 is a diagram showing a configuration in which a temperature distribution measuring device according to an embodiment of the present invention is applied to abnormal monitoring of a high-temperature pipe. In FIG. 1, the same parts as those in FIG. 6 are denoted by the same reference numerals. In the high-temperature pipe A shown in FIG. 1, a heat-resistant material 5 is attached to the inner surface of the steel pipe 4. An optical fiber sensor 8 in the form of a ribbon cable is provided on the outer surface of the steel tube 4.
Are wound at predetermined intervals in the longitudinal direction of the steel tube 4. The optical fiber 1 is wound around the optical fiber sensor 8 so as to have a plurality of loops as described later, and the end of the optical fiber 1 is connected to the temperature distribution measuring device 2.

FIG. 2 is a diagram showing the configuration of the optical fiber sensor 8. As shown in FIG. In FIG. 2, the width (W) is made of copper, nickel, or the like.
The optical fiber 1 is wound several times (twice in FIG. 2) with a diameter (D) of about 60 mm on a thin plate 7 having a diameter of about 70 mm, and an interval (L) of about 60 mm in the longitudinal direction of the thin plate 7. Is attached with an adhesive or the like. It is desirable that the optical fiber be wound with a diameter (D) of 60 mm or more because the transmitted light is attenuated when the bending diameter is reduced, and the accuracy of temperature measurement is reduced. The number of turns is determined in consideration of the relationship with the temperature detection sensitivity.

The relationship between the hot spot and the detected temperature will be described below. In the conventional method shown in FIG. 6, the diameter of the hot spot 6 at 100.degree.
Is laid at the center of the hot spot 6.
In this case, since the length of the optical fiber 1 on the hot spot 6 is about 0.5 m, the measurement temperature is about 45 ° C. at the highest part as shown in FIG. 5, and the hot spot 6 at 100 ° C. can be detected. Absent.

On the other hand, like the optical fiber sensor 8 according to the present embodiment, the optical fiber 1 has a diameter of about 60 mm.
For example, when a wire wound twice is used and the diameter of the hot spot 6 at 100 ° C. is 0.5 m, the total length L of the optical fiber 1 is as shown in the following equation (3).

[0014]

(Equation 1) That is, since the total length L of the optical fiber 1 exceeds 3 m,
From FIG. 5, about 100 ° C. can be detected at the highest part, and the hot spot 6 at 100 ° C. can be detected.

FIG. 3 is a diagram showing a configuration of an optical fiber sensor 8 'which is a modified example of the optical fiber sensor 8. As shown in FIG. 3, the same parts as those in FIG. 2 are denoted by the same reference numerals. In FIG. 3, the optical fiber 1 is wound on the thin plate 7 once with a diameter (D) of about 60 mm, and is wound about 6 mm in the longitudinal direction of the thin plate 7.
It is stuck every 0 mm with an adhesive or the like. In this case as well, the detection of the hot spot 6 at 100 ° C. becomes possible as described above.

It takes a lot of work to directly lay the optical fiber 1 several times with a diameter of about 60 mm around the high temperature pipe A which is the object to be measured. Therefore, as in the case of the optical fiber sensors 8 and 8 ', a ribbon cable having the diameter and the number of turns of the optical fiber 1 suitable for the detection purpose is manufactured in advance and wound around the high-temperature pipe A, thereby simplifying the operation. be able to.

The present invention is not limited to the above-described embodiment, but can be implemented with appropriate modifications without departing from the scope of the invention. For example, the diameter, the number of turns, and the winding method of the optical fiber 1 can be appropriately modified according to the purpose of detection.

(Summary of Embodiment) The configuration, operation and effect shown in the embodiment are summarized as follows. [1] The temperature distribution measuring device shown in the embodiment has an optical fiber sensor (8, 8 ') formed by forming one optical fiber 1 into a plurality of rings and affixing it to a support member (7). Optical fiber sensors (8, 8 ') are provided on the measurement target (A),
Measuring means (2) for measuring the temperature distribution with respect to the position of the measurement target (A) by measuring the backscattered light of the optical fiber 1.

Therefore, according to the temperature distribution measuring device, even when the area of the high temperature portion (6) of the measurement object (A) is small and the temperature locally rises, the temperature can be measured, and the measurement object (A) can be measured. The abnormality of A) can be detected. [2] The temperature distribution measuring device described in the embodiment is the device described in the above [1], and the optical fiber sensor (8) has a ring shape in which the optical fiber 1 is wound with a predetermined diameter a predetermined number of times. Were attached at predetermined intervals along the longitudinal direction of the support member (7). Therefore, according to the temperature distribution measuring device, the optical fiber 1 can be laid on the measurement target (A) by a simple operation.

[0020]

According to the temperature distribution measuring apparatus of the present invention, even when the area of the high-temperature portion to be measured is small and the temperature locally rises, the temperature can be measured and the abnormality of the measuring object can be detected. it can. ADVANTAGE OF THE INVENTION According to the temperature distribution measuring device of this invention, an optical fiber can be laid to a measuring object by simple operation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration in which a temperature distribution measuring device according to an embodiment of the present invention is applied to monitoring of abnormalities in a high-temperature pipe.

FIG. 2 is a diagram showing a configuration of an optical fiber sensor according to the embodiment of the present invention.

FIG. 3 is a diagram showing a modification of the optical fiber sensor according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a test situation of a distance resolution with respect to an optical fiber temperature by a temperature distribution measuring device according to a conventional example.

FIG. 5 is a diagram showing a result of a distance resolution test according to the embodiment of the present invention and a conventional example.

FIG. 6 is a diagram showing an abnormality monitoring apparatus for a high-temperature pipe according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical fiber 2 ... Temperature distribution measuring device 3 ... Constant temperature furnace 4 ... Steel tube 5 ... Heat resistant material 6 ... Local high temperature part 7 ... Thin plate 8, 8 '... Optical fiber sensor A ... High temperature piping G ... High temperature gas

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[Procedure amendment]

[Submission date] December 14, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

On the other hand, like the optical fiber sensor 8 according to the present embodiment, the optical fiber 1 has a diameter of about 60 mm.
If in using that wound for example, twice the diameter of the 100 ° C. hot spot 6 is assumed to be 0.5 m, hot
The total length L of the optical fiber 1 at the spot 6 is given by the following equation (3).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Sugimura 5-717-1 Fukabori-cho, Nagasaki-shi, Nagasaki Sanishi Heavy Industries Co., Ltd. Nagasaki Research Institute (72) Inventor Masazumi Tsukano 1-1-1, Akunoura-cho, Nagasaki-shi, Nagasaki No.Mitsubishi Heavy Industries, Ltd.Nagasaki Shipyard

Claims (2)

[Claims] An optical fiber sensor in which one optical fiber is formed in a plurality of loops and attached to a support member, and the optical fiber sensor is provided on an object to be measured, and backscattered light of the optical fiber is measured. A temperature distribution measuring device for measuring a temperature distribution with respect to the position of the measurement target. 2. The optical fiber sensor according to claim 1, wherein the optical fiber sensor is formed by attaching a ring-shaped optical fiber wound a predetermined number of times with a predetermined diameter along the longitudinal direction of the support member at a predetermined interval. The described temperature distribution measuring device.