JP3464731B2 - Gas temperature measuring device having a light guide with black body film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas temperature measuring device in a combustion apparatus such as a boiler furnace, and more particularly to a gas temperature measuring apparatus having a light guide section with a black body film suitable for measuring the gas temperature near the burner of the combustion apparatus. Regarding measuring equipment.

[0002]

2. Description of the Related Art Measuring gas temperature in a combustion apparatus such as a boiler furnace is to monitor combustion in a combustion apparatus such as a boiler furnace.
This is an extremely important matter for efficient operation of control.
Conventionally, a radiation (optical) thermometer or the like has been used for this purpose, but there is a problem that it is difficult to specify the measurement region. As a method of solving this problem, in recent years, for example, a light guide part with a black body film 11 as shown in FIG. 4 in which a black body film (emissivity is close to 1) is provided at the tip of the light guide part is used. Gas temperature measuring devices have come into use. The light guide part 11 with a black body film is characterized in that the temperature of the peripheral part of the black body film 12 at the tip can be measured. In general, the environment for measuring the gas temperature is corrosive, and the life of the black body film 12 is particularly shortened. Therefore, in order to protect the environment, the light guide unit 11 with the black body film of the gas temperature measuring unit is exposed to light. A transparent protective cylinder 13 is provided. In FIG. 4, gas 1 around the tip of the light guide section
Radiation from 8 is a light-transmitting protective cylinder 13, space (air layer)
After passing through 15, the radiant heat is transferred to and absorbed in the black body film 12. There is a certain relationship between the gas temperature and the radiation intensity absorbed by the black body film 12. Therefore, the radiant intensity absorbed by the black body film 12 is guided to the outside from the light guide portion 11 with a black body film made of, for example, sapphire, which is heat resistant and has a small optical transmission loss, and is connected to the relay optical fiber connection portion 17 and The temperature is displayed after being guided to the temperature calculation unit through the optical fiber for relay and photoelectrically converted. Here, the radiation intensity absorbed by the black body film 12 includes the following temperature rise due to convective heat transfer.

Temperature rise due to heat transfer from gas convection on the outer surface of the light-transmitting protective cylinder 13. The amount of temperature increase due to convective heat transfer in the space (air layer) 15 between the light-transmitting protective cylinder 13 and the light guide portion 11 with the black body film. With respect to the above, if a material having a high thermal conductivity (for example, sapphire, diamond, etc.) is selected as the material of the light-transmitting protective cylinder 13, an extreme temperature difference from the ambient gas temperature does not occur, and therefore it is based on that. The increase in radiation intensity is small. On the other hand, the above is convective heat transfer with the black body film 12 (the response speed is smaller than that of radiant heat transfer), so the response speed of direct radiant heat transfer from the external gas temperature to be measured is apparently small. There is a problem such as increase in noise and noise (accompanying turbulence of convection). There is a gas flow in a combustion apparatus such as a boiler furnace, and the gas temperature generally changes momentarily, and a fast response speed is required also in measuring the gas temperature corresponding to this. In particular, when measuring the gas temperature in the vicinity of the burner of the combustion device, the flame may come into direct contact with the light-transmissive protective cylinder 13 of the light guide portion, and the effect of convective heat transfer described above is ignored. There are problems such as not being able to. In addition, as described above, in the conventional light guide 11 with a black body film, sufficient consideration has not been given in terms of response speed, and particularly in measurement of flame or gas temperature near burner flame. There was a problem in terms of accuracy and response speed in measuring the gas temperature at a location where the temperature changes drastically.

[0004]

As described above, in the prior art, since an air layer exists between the light guide part with a black body film and the light-transmissive protective cylinder that protects it, this air layer is used. However, there is a problem that the response speed and the measurement accuracy are deteriorated due to the convective heat transfer.

It is an object of the present invention to suppress the influence of convective heat transfer in the above-mentioned prior art, and to improve the gas temperature response speed and the measurement accuracy. To provide.

[0006]

In order to achieve the above-mentioned object of the present invention, the present invention has a constitution as set forth in the claims. That is, according to the present invention, as described in claim 1, a gas thermometer having a black body film provided at the tip of the light guide part and having a light guide part with a black body film for measuring the temperature around the black body film.
In the measuring device, the space between the light guide part with the black body film and the light-transmissive protective cylinder that houses and protects the light guide part with the black body film is kept at a pressure of atmospheric pressure or less. It is a gas temperature measuring device which has a light guide part with a black body film. The present invention also provides claim 2.
As set forth in claim 1, in claim 1, the space between the light guide with black body film and the light-transmissive protective cylinder for protecting the light guide with black body film inside is enlarged. It is a gas temperature measuring device having a light guide part with a black body film, which is provided with a vacuum exhaust system for maintaining the pressure below atmospheric pressure. Further, according to the present invention, as described in claim 3, in claim 1 or 2, the light guide part with a black body film and the light transmission for accommodating and protecting the light guide part with the black body film inside. It is a gas temperature measuring device having a light guide part with a black body film in which the pressure in the space between the property protection cylinder and the pressure protection part is kept at a pressure of 1 mm of mercury or less.

[0007]

According to the present invention, as described in claim 1, the air existing between the light guide part with the black body film and the light-transmissive protection cylinder for housing and protecting it (or other The same applies to gas)
By removing the layer and reducing the pressure to a vacuum or a pressure significantly lower than the atmospheric pressure, the collision probability between gas molecules existing in the light-transmitting protective cylinder is extremely reduced, so that the convective heat transfer is zero ( (0: vacuum) or significantly reduced compared to the case of atmospheric pressure. As a result, the radiant heat transfer (heat radiation) from the high-temperature combustion gas outside via the light-transmitting protective cylinder can be directly transferred to the black body film, preventing a decrease in response speed and measurement accuracy. There is an effect that can be done. Further, according to a second aspect of the present invention, in the first aspect, a light guide part with a black body film, and a light-transmissive protective tube for accommodating and protecting the light guide part with the black body film inside are provided. Since a vacuum exhaust system for maintaining the space between them at a pressure equal to or lower than the atmospheric pressure is provided, the space can be appropriately vacuum exhausted, and the response speed of radiation heat transfer and the measurement accuracy can be improved. There is an effect that can be improved. The present invention also provides claim 3.
The space between the light guide part with a black body film and the light-transmissive protective cylinder for housing and protecting the light guide part with a black body film according to claim 1 or 2. By maintaining the pressure of the part at a pressure of 1 mm of mercury (1 Torr ... about 1/1000 atm) or less, radiant heat transfer (heat radiation) from the high temperature combustion gas outside can be directly transmitted via the light-transmissive protective cylinder. Since it is transmitted to the black body film, there is an effect that the response speed and the measurement accuracy can be improved.

[0008]

1 is a schematic diagram showing an example of the structure of a gas temperature measuring device having a light guide section with a black body film according to an embodiment of the present invention. In the figure, the heat resistant temperature is high,
Light guide part 11 with black body film made of sapphire (crystalline alumina) with high thermal conductivity and low optical transmission loss (about 1.3
φ) black body film 12 made of platinum / rhodium alloy at the tip of
(Emissivity is almost 1). This black body film 12
Since it is vulnerable to corrosive environment, it has a structure that it is housed inside a light-transmitting protective cylinder 13 (outer diameter of about 4 mm) made of sapphire for protection. A space 15 exists between the protective cylinder 13 and the inner wall thereof. The light guide 11 with the black body film made of sapphire and the light-transmitting protective cylinder 13 made of sapphire are coaxially held by the support 14. A vacuum exhaust pipe 16 is provided which penetrates a part of the support portion 14 and communicates with the space 15. FIG. 2 shows an example of a case where the gas temperature measuring device having the light guide part 11 with a black body film of the present invention is attached to the combustion device 31. The heat radiation from the gas 21 in the combustion device around the black body film 12 is absorbed by the black body film 12 through the light-transmitting protective cylinder 13, and the absorbed heat radiation is the radiation law of the black body film ( According to Planck's radiation law,
The light is radiated to the light guide section 11 with the black body film made of sapphire. This radiation is guided to the temperature calculation unit 23 by the relay optical fiber 22 through the black body film-attached light guide unit 11, where it is converted into an electric signal by photoelectric conversion, and the temperature measurement value is displayed. In addition, in general, the temperature is calibrated using the radiant light from a standard blackbody furnace. The vacuum exhaust pipe 16 is connected to the vacuum exhaust pump 24, and during the temperature measurement, the space 15 is constantly evacuated to a pressure of atmospheric pressure or less, for example, a pressure of about 1 Torr or less. 3A, 3 </ b> B, 3 </ b> C, and 3 </ b> D are enlarged cross-sectional views showing the detailed structure of the support portion 14 to which the vacuum exhaust pipe 16 is attached. FIG. 3A shows a portion that coaxially supports the light guide portion 11 with the black body film and the light-transmitting protection cylinder 13, and the black sleeve is attached to the metal sleeve 32 for the light guide portion 11 with the black body film. The end of the light guide unit with film 11 is inserted and fixed by the adhesive layer 37.
In this state, the connection cover shown in FIG. 3C is attached from the left side. Next, the light-transmissive protection cylinder 13 is inserted into the metal sleeve 33 for the light-transmission protection cylinder 13, and the metal sleeve 32 for the light guide part 11 with a black body film is included in the metal sleeve 33 shown in FIG. As described above, the adhesive layer 37 is used for fixing. The metal sleeve 33 also serves as a support portion for attachment to a combustion device or the like. The metal sleeve 32 is provided with at least one through hole 34 formed so as to communicate with the space 15. The connection cover shown in FIG. 3C is connected to the optical fiber relay section 40 shown in FIG. 3B with a screw A38. Each connecting portion has a structure sealed by a packing 36 for sealing. Further, the through hole 35 is also provided in the optical fiber relay section 40. The through hole 35 is connected to a vacuum exhaust pump, and is provided for the purpose of reducing the pressure of the space 15 to an arbitrary pressure equal to or lower than the atmospheric pressure via the through hole 34 with the space 15. Figure 3
The connection cover shown in (d) is for connecting the end portion of the relay optical fiber 22 shown in FIG. 2 to the end portion 41 of the light guide portion with a black body film 11, and the optical fiber is screwed with a screw B39. It is connected to the relay unit 40. The relay optical fiber 22 is
It is attached through a hole 42 for the end of the relay optical fiber. As shown in FIGS. 3 (a), 3 (b), 3 (c), and 3 (d), each component of the support portion has a structure in which the sealing packing 36 and the adhesive layer 37 block the outside air. The gas temperature measuring device having the light guide part with the black body film of the present invention can be easily attached to a combustion device or the like, and at the time of temperature measurement, the space 15 inside the light-transmitting protective cylinder 13 is evacuated by the vacuum exhaust pump. Since the pressure can be appropriately reduced to any pressure lower than the atmospheric pressure, the convective heat transfer in the space 15 can be significantly reduced, and the accuracy of temperature measurement and the response speed can be improved.

[0009]

According to the gas temperature measuring device having the light guide part with the black body film of the present invention, the burner flame of the combustion device is provided in the light-transmissive protective cylinder for protecting the light guide part with the black body film in vacuum. Even if it comes into direct contact, the radiant heat from the burner flame is directly transmitted to the black body film provided inside the light-transmitting protective cylinder, so that the measurement accuracy and response speed can be improved. Also,
In the conventional light guide unit with a black body film that has an air layer, when used for a long time in a high-temperature combustion gas atmosphere, the temperature of the air layer trapped inside rises and the light guide unit with a black body film and the light transmission A crack or the like occurs in the support portion that adheres and supports the sex protection cylinder coaxially, and this damages and damages the light guide portion with a black body film having a small mechanical strength. However, according to the gas temperature measuring device of the present invention, since the inside of the light-transmissive protective cylinder is in a vacuum, it is possible to prevent damage due to the temperature rise of the conventional air layer, and only the support portion is covered with, for example, a metal reflection member. Only by using a combination structure of a membrane and a heat insulating material, it is possible to protect from radiant heat and to realize temperature measurement of high temperature combustion gas for a long time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a structure of a light guide unit with a black body film of a gas temperature measuring device exemplified in an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a pattern in which a gas temperature measuring device having a light guide unit with a black body film illustrated in the embodiment of the present invention is arranged in a combustion device.

FIG. 3 is a schematic diagram showing a structure of a support portion of the light guide portion with a black body film illustrated in the embodiment of the present invention.

FIG. 4 is a schematic diagram showing a structure of a light guide unit with a black body film of a conventional gas temperature measuring device.

[Explanation of symbols]

11 ... Light guide part with black body film 12 ... Black body membrane 13 ... Light-transmitting protective tube 14 ... Supporting part 15 ... Space 16 ... Vacuum exhaust pipe 17 ... Optical fiber connection for relay 18 ... Gas around the tip 21 ... Gas in the combustion device 22 ... Relay optical fiber 23 ... Temperature calculation unit 24 ... Vacuum pump 31 ... Combustion device 32 ... Metal sleeve for light guide with black body film 33 ... Metal sleeve for light-transmitting protective cylinder 34 ... Through-hole with space 15 35 ... through hole 36 ... Seal packing 37 ... Adhesive layer 38 ... Screw A 39 ... Screw B 40 ... Optical fiber repeater 41 ... Edge of light guide 42 ... Hole for end of optical fiber for relay

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-136348 (JP, A) JP-A-63-100340 (JP, A) Actual opening 5-11031 (JP, U) Actual opening Sho-62- 148928 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 5/00-5/62

Claims (3)

(57) [Claims] 1. A gas thermometer having a black body film-provided light guide portion for measuring the temperature around the black body film.
In the measuring device, the space between the light guide part with the black body film and the light-transmissive protective cylinder for protecting the light guide part with the black body film inside is kept at a pressure of atmospheric pressure or less. A gas temperature measuring device having a light guide part with a black body film. 2. The atmospheric pressure in the space between the light guide part with a black body film and the light-transmissive protective cylinder for accommodating and protecting the light guide part with a black body film according to claim 1. A gas temperature measuring device having a light guide part with a black body film, characterized in that a vacuum exhaust system for maintaining the following pressure is provided. 3. The space portion between the light guide part with a black body film and the light-transmissive protection tube for housing and protecting the light guide part with a black body film according to claim 1 or 2. Is maintained at a pressure of 1 mm or less of a mercury column, and a gas temperature measuring device having a light guide section with a black body film.