JP2005195502A - Optical fiber type temperature measuring apparatus and temperature measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber type temperature measuring apparatus, which can be applied to even a narrow and small section to be measured. <P>SOLUTION: The optical fiber type temperature measuring apparatus which measures temperature values of the section to be measured, is equipped with a light source device 2 which emits pulse light from one edge of an optical fiber 4; a detecting system which detects backscattering light generated at each portion of the optical fiber 4; and a processing section 18 which determines the temperature value of each portion of the optical fiber, based on output signals from the detecting system. In the temperature measuring apparatus, a heat pipe 5 which is used as a thermosensitive member, has a thermosensitive section 5A at its portion contacting with the section to be measured, and the optical fiber 4 is brought to contact with the heat pipe 5 over a prescribed length in the remaining portion of the heat pipe. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber temperature measuring device that measures temperature using an optical fiber.

  Temperature measurement under conditions where a large number of parts to be measured exist in a wide range, heat generation monitoring, for example, heat generation monitoring of equipment such as pumps, motors, bearings, etc. in the combustible manufacturing process, as well as coal belt conveyor fires at thermal power plants An optical fiber type temperature measuring device is sometimes used to monitor bearing heat generation, which is considered to be the main cause.

  As such an apparatus, a specific portion in the longitudinal direction of the optical fiber is arranged at a measurement site, pulse light is projected from one end of the optical fiber, and backscattered light is detected to detect the measurement site. An apparatus for measuring temperature is known from US Pat.

  In such temperature measurement using an optical fiber, the measurement accuracy (distance resolution) depends on the pulse width of the optical pulse, and the measurement temperature is an average temperature corresponding to the pulse width. Therefore, the optical fiber corresponds to the pulse width of the pulse light. Therefore, it was necessary to be kept under the temperature to be measured over the length of the measurement, and it was not suitable for measuring a substantially spot-like narrow part. Therefore, in Patent Document 1, the optical fiber is wound a plurality of times under the removal of the protective material, and the temperature is measured so that the above length is obtained within the smallest possible range and the equivalent pulse width is the same temperature. ing.

  As shown in FIGS. 3 to 4 of the accompanying drawings, the device of Patent Document 1 exposes the optical fiber C1 by exposing the optical fiber cable C over a certain length and removing the protective coating such as the metal tube. The optical fiber C <b> 1 is wound into a coil shape a plurality of times, and this coil is stored in the corresponding annular groove 52 of the support member 51. A drawing groove 53 extending in the tangential direction is formed in communication with the annular groove 52, and the cable C is drawn out of the support member 51. A lid member 54 is attached to the support member 51.

  The support member 51 is made of a highly heat conductive material and is attached to a desired measurement site of the measurement object. Therefore, the coil of the optical fiber C1 has a temperature that approximates the temperature of the measurement site over the entire length of the coil.

According to such an apparatus of Patent Document 1, the pulsed light incident on the measurement optical fiber propagates through the optical fiber, and backscattered light is generated at each part of the optical fiber. The intensity of the backscattered light has a value corresponding to the temperature of each part of the optical fiber. The generated backscattered light propagates in a direction opposite to the conduction direction of the pulsed light, that is, in the incident direction, is separated from the projection light, and further separated into Stokes light and anti-Stokes light due to Raman scattering. The Stokes light and the anti-Stokes light generate output signals corresponding to the intensity of the Stokes light and the intensity of the anti-Stokes light, respectively, and these output signals are sent to a processing circuit (not shown) for arithmetic processing, The temperature of each part of the fiber is obtained.
Japanese Patent No. 3300288

  In such a temperature measuring device of the type of Patent Document 1, the length (heating length) of the heated portion of the optical fiber in the measurement site needs to be at least the length corresponding to the pulse width of the incident pulsed light. is there. Therefore, in Patent Document 1, an optical fiber is wound in a coil shape a plurality of times in order to ensure the length.

  Although the optical fiber can be wound as described above, the loss increases as the winding radius decreases. Therefore, there is a limit to reducing the winding radius, and the optical fiber must be wound with a relatively large radius. This means that the support member of the heat-conductive material that accommodates the optical fiber becomes large, and even though it can be somewhat reduced in size, it is still unsuitable for measurement in a spot-like narrow part. .

  Since such a support member cannot be sufficiently reduced in size, not only handling becomes inconvenient, but also the measurement target part of the measurement object to which the support member is attached is naturally limited to a narrow part or a specific point. Cannot be measured.

  In addition, the accuracy of the optical fiber decreases as the measurement range placed under the temperature of the measurement site is shorter than the pulse width. Since there is a correlation between measurement length and measurement accuracy (distance resolution), true temperature can be estimated by correction even if the length is insufficient. However, the smaller the measurement range, the larger the correction amount and its reliability. Will decline.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber type temperature measuring apparatus that enables measurement in a narrow part or a specific point using an optical fiber.

  An optical fiber type temperature measuring device according to the present invention includes a light source device that projects pulsed light from one end of an optical fiber, a detection system that detects backscattered light generated at each part of the optical fiber, and an output signal from the detection system. And a processing unit for determining the temperature of each part of the optical fiber based on the above.

  In such an optical fiber type temperature measuring device, the present invention has a heat pipe as a heat sensitive member, the heat pipe has a heat sensitive part in contact with a part to be measured, and the optical fiber is the remaining part of the heat pipe. It is characterized by being held in contact with the heat pipe over a predetermined length.

  According to such an apparatus of the present invention, a part of the heat pipe is arranged as a heat sensitive part at the measurement site of the measurement object. Therefore, even if the part to be measured is narrow, a part of the heat pipe as the heat sensitive part is sufficiently small in size so that attachment is possible.

  When there is a change in temperature at the part to be measured, the temperature is raised and lowered almost immediately to the temperature of the heat sensitive part through the heat sensitive part of the heat pipe over the entire length of the heat pipe. On the other hand, since the optical fiber is in direct or indirect contact with the heat pipe over a predetermined length, the temperature of the measurement site is maintained over the contact range length. That is, although the heat-sensitive part of the heat pipe is a small part, the optical fiber reaches the temperature of the measurement site over a predetermined length.

  As in the conventional method disclosed in Patent Document 1, the measurement in the optical fiber is performed by making pulse light incident from one end of the optical fiber and using the backscattered light to produce Stokes light and anti-Stokes by Raman scattering. The temperature is calculated by processing an output signal that is separated and based on these intensities. At this time, correction is performed when the contact length between the optical fiber and the heat pipe is shorter than the pulse width of the incident pulse and there is a measured temperature difference between adjacent portions.

  In the present invention, the heat pipe may have a substantially annular portion, and the optical fiber may be wound a plurality of times in contact with the annular portion. In this way, the heat sensitive part at one end of the heat pipe may be kept small, while the optical fiber is wound a plurality of times along the substantially annular part to thereby reduce the pulse width of the incident pulse light. Long enough to contact the heat pipe.

  In the present invention, it is desirable that the optical fiber and the heat pipe are covered with a heat insulating material over the length of the contact range. By providing this heat insulating material, the optical fiber is more approximate to the temperature of the heat pipe and its responsiveness is further improved.

  Furthermore, in the present invention, when the contact range length between the optical fiber and the heat pipe is shorter than the pulse width of the pulsed light and there is a difference between the measured temperature in the range and the measured temperature at the adjacent portion, the temperature difference It is preferable that the processing unit has a correction unit that corrects the temperature based on the ratio between the pulse width and the heating length.

  In the present invention, as described above, a part of the heat pipe is arranged as a heat sensitive part at a measurement site of an object to be measured, and an optical fiber is brought into contact with the remaining part of the heat pipe for a predetermined length. Since measurement was performed, measurement was possible even in a narrow part to be measured, and the length of the optical fiber could be secured for measurement using an optical fiber. Not only the measurement application field expanded, but also the accuracy and certainty of measurement were improved. .

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.

  1 is an overall configuration diagram of an optical fiber type temperature measuring device of the present embodiment.

  The apparatus according to the present embodiment includes a measurement element 1, a measurement device main body 2, and a display device 3.

  In the present embodiment, a plurality of measuring elements 1 are connected in series with one optical fiber 4. Each measuring element 1 has a heat pipe 5 in contact with the optical fiber 4 as a heat sensitive member. The heat pipe 5 is formed by bending one end of a straight pipe, and the one end forms a heat sensitive part 5A. The straight portion of the heat pipe 5 forms a heat transfer portion 5B and is in contact with the optical fiber 4 so that the heat of the heat pipe 5 is transferred to the optical fiber 4 as it is. Here, the optical fiber 4 is usually protected by a metal tube or the like because it is outside the measuring apparatus main body 2. Therefore, in this case, the optical fiber 4 receives heat from the heat transfer section 5B through a metal tube or the like that is a good heat conductive material. The heat sensitive part does not need to be one end of the heat pipe and may be a part of the intermediate part.

  The heat transfer section 5B of the heat pipe 5 and the optical fiber 4 in a range corresponding to the heat transfer section 5B are surrounded by a heat insulating material 6. The heat insulating material 6 has a function of blocking heat exchange with the outside and securely contacting the heat transfer portion 5B and the optical fiber 4 in that state.

  The measurement element 1 is appropriately attached to each measurement site P of the measurement object, for example, by making a measurement hole or the like and inserting the heat sensitive part 5A, or fixing with a support. Further, when the number of measurement sites P increases, the number of the measurement sites P can be increased by contacting and attaching the heat pipe 5 to the optical fiber 4 extending long at the corresponding position.

  The apparatus main body 2 includes a laser light source 7 as a light source device that emits pulsed light and a first directional coupler 9 connected by an optical fiber 8, and the optical fiber 4 is connected to the first directional coupler 9. Is done. The first directional coupler 9 includes incident light that is incident on the optical fiber 4 from the laser light source 7 and backscattered light that is scattered in the optical fiber 4 in the direction opposite to the incident direction after being scattered. And has a function of separating.

  A second directional coupler 11 is connected to the first directional coupler 9 by an optical fiber 10. The second directional coupler 11 receives the backscattered light separated by the first directional coupler 9 through the optical fiber 10 and separates it into Stokes light and anti-Stokes light due to Raman scattering, These are connected to transmit them to the narrow band filters 14 and 15 via separate optical fibers 12 and 13.

  The narrow band filters 14 and 15 are respectively provided with a first photodetector 16 and a second photodetector 17 in close proximity to form a detection system, and Stokes light transmitted through the narrow band filters 14 and 15. Anti-Stokes light is detected. The first photodetector 16 and the second photodetector 17 are connected to a processing unit (signal processing circuit) 18, and the intensity ratio between the Stokes light and the anti-Stokes light is measured at each measured site by a known method. Calculate the temperature. The processing unit 18 is also connected to the laser light source 7 in order to determine the timing of the pulsed light from the laser light source 7. Further, the display unit 3 is connected to the processing unit 18 so as to display the calculated temperature.

  The processing unit 18 also includes a correction unit 18A that performs correction as necessary. The correction in the correction unit 18A is performed when the heat transfer unit 5B of the heat pipe 5 is shorter than the pulse width of the pulsed light and there is a measured temperature difference between the adjacent units. Since the temperature calculation is performed as an average value of the signal intensity with a length corresponding to the pulse width, if the contact range length in the heat transfer section 5B is short, it is calculated as a value lower than the actual temperature. Therefore, in such a case, the difference between the temperature at the portion other than the heat transfer section 5B and the temperature at the heat transfer section 5B is corrected by multiplying the ratio of the pulse width and the contact range length.

  For example, when the temperature of the measured region is 115 ° C. and the temperature of the adjacent portion is 15 ° C., the pulse width of the pulsed light is x, the length of the optical fiber in contact with the heat transfer unit is y, and the contact is made when y ≧ x Since the range length is longer than the distance resolution, the measurement temperature may be 115 ° C., and the temperature T of the measurement site may be adopted as T = 115 ° C. as it is. Next, when y <x, the contact range length is shorter than the distance resolution, so that it becomes lower than the measured temperature. For example, when y = x / 2, if the measurement temperature is 65 ° C. and the temperature at the adjacent part outside the measurement site is 15 ° C., the temperature T of the measurement site is T = 15 + (65 −15) × [x / (x / 2)], that is, T = 15 + 50 × 2 = 115 (° C.), and the corrected temperature T of the measured region is obtained.

  In this embodiment of the apparatus having such a configuration, the temperature measurement for the measurement site is performed as follows.

  (1) First, the heat sensitive part 5A of the measuring element 1 is inserted and attached to an attachment hole or the like formed in the measurement site of the measurement object. The heat sensitive part 5A is fixed with a good heat transfer adhesive or the like.

  (2) When there is a temperature change in the measurement site, the heat medium in the heat pipe 5 immediately flows, and the heat transfer section 5B has the same temperature as the heat sensitive section 5A and is in contact with the heat transfer section 5B. The temperature of the heat transfer part 5B also becomes the fiber 4 in the contact area.

  (3) Pulse light is emitted from the laser light source 7 and enters the measurement optical fiber 4 through the optical fiber 8. The pulsed light incident on the optical fiber 4 propagates through the optical fiber 4, and backscattered light is generated at each part including the part corresponding to the heat transfer section 5 </ b> B of the optical fiber 4. The intensity of the backscattered light has a value corresponding to the temperature of each part of the optical fiber.

  (4) The generated backscattered light propagates in the direction opposite to the conduction direction of the pulsed light, that is, in the incident direction, enters the first directional coupler 9, and is projected from the projection light by the first directional coupler. The light is separated and enters the second directional coupler 11 through the optical fiber 10.

  (5) Thereafter, the backscattered light is separated into Stokes light and anti-Stokes light due to Raman scattering by the second directional coupler 11, and these Stokes light and anti-Stokes light are transmitted through the narrow band filters 14 and 15, respectively. Then, the light enters the first photodetector 16 and the second photodetector 17, respectively.

  (6) The first photodetector 16 and the second photodetector 17 generate output signals corresponding to the intensity of Stokes light and the intensity of anti-Stokes light, respectively, and send these output signals to the processing unit 18. Since the ratio between the intensity of Stokes light due to Raman scattering and the intensity of anti-Stokes light becomes a value corresponding to the temperature of each part of the measurement optical fiber 4, the first photodetector 16 and the second detector 16 in the processing unit 18. An output signal from the light detector 17 is arithmetically processed to determine the temperature of the part of the measurement element 1 of the optical fiber. Further, the processing unit 18 is configured so that each part from the incident end of the optical fiber is based on the emission timing of the pulsed light from the laser light source 2 and the generation time of the output signals from the first photodetector 16 and the second photodetector 17. Find the distance to. Further, when the length of the heat transfer section 5B in the measurement element 1 is shorter than the pulse width of the pulsed light and there is a measured temperature difference between the adjacent sections, the calculation is performed by the correction section 18A based on the principle described above. Correct the temperature.

  (7) Thus, the distance from the incident end of the measurement optical fiber and the temperature at the position of the distance are output from the processing unit 18, and this output is displayed on the display device 3.

  The present invention is not limited to the form shown in FIG. 1 and can be modified. For example, when the heat transfer portion of the heat pipe cannot be sufficiently long with respect to the pulse width, in order to ensure a large heating length of the optical fiber here, as shown in FIG. 2, the heat transfer portion 5B of the heat pipe 5 Is formed as a substantially annular portion, and the optical fiber 4 can be wound a plurality of times while being in contact with the heat transfer portion 5B. If the winding amount is longer than the pulse width, the measurement length can be secured longer than the distance resolution, so that the measurement temperature need not be corrected. In this case, although depending on the number of turns and the radius, the optical fiber 4 may be removed from a protective material such as a metal tube. However, also in this case, it is preferable that the wound optical fiber 4 and the heat transfer section 5B are surrounded by the heat insulating material 6 to be thermally shielded from the outside. Thus, according to the example of FIG. 2, the heat sensitive part is one end of the heat pipe as in FIG. 1, and measurement in a spot-like narrow part is possible, as well as contact with the heat transfer part of the heat pipe. The length of the optical fiber to be measured can be sufficiently secured with respect to the pulse width of the pulse light for measurement.

It is a schematic block diagram which shows one Embodiment of this invention. It is a figure which shows the modification about a measurement element. It is a top view when the cover member about a conventional apparatus is removed. 3 is a perspective view showing the lid member of the apparatus separately.

Explanation of symbols

2 Light source device (laser light source)
4 Optical fiber 5 Thermal member (heat pipe)
5A heat sensitive part 6 heat insulating material 16, 17 detection system (first photodetector, second photodetector)
18 Processing unit

Claims (6)

  A light source device that projects pulsed light from one end of the optical fiber, a detection system that detects backscattered light generated at each part of the optical fiber, and the temperature of each part of the optical fiber is determined based on an output signal from the detection system In the optical fiber type temperature measuring device for measuring the temperature of the part to be measured, the heat pipe has a heat pipe as a heat sensitive member, and the heat pipe partially has a heat sensitive part in contact with the part to be measured. An optical fiber type temperature measuring apparatus, wherein the optical fiber is held in a state of being in direct or indirect thermal contact with the heat pipe over a predetermined length in the remaining portion of the heat pipe.   The optical fiber type temperature measuring device according to claim 1, wherein the optical fiber is protected by a metal tube.   The optical fiber type temperature measuring apparatus according to claim 1 or 2, wherein the heat pipe has a substantially annular portion, and the optical fiber is wound a plurality of times in contact with the annular portion.   The optical fiber type temperature measuring device according to any one of claims 1 to 3, wherein the optical fiber and the heat pipe are covered with a heat insulating material over a range of mutual contact length.   When the contact range length between the optical fiber and the heat pipe is shorter than the pulse width of the pulsed light and there is a difference between the measured temperature at the contact range length and the measured temperature at the adjacent portion, the processing unit 6. The optical fiber type temperature measuring device according to claim 1, further comprising a correction unit that corrects the temperature based on a ratio between the pulse width and the contact range length.   In a temperature measurement method for projecting pulsed light from one end of an optical fiber, detecting backscattered light generated in each part of the optical fiber, and determining the temperature of each part of the optical fiber based on the detected output signal. The contact range length between the heat pipe and the pulse width of the pulsed light is compared, the measured temperature at the contact range length is compared with the measured temperature at the adjacent portion, and the contact range length is greater than the pulse width. A temperature characterized in that, when there is a difference between the measured temperature at the contact range length and the measured temperature at the adjacent portion, the temperature difference is corrected based on the ratio of the pulse width to the contact range length. Measurement method.

Images