JPH03287026A - Method and device for simultaneous measurement of temperature and emissivity of body - Google Patents

Abstract

PURPOSE:To remove the influence of an unknown stray light noise from the internal wall of a furnace and to measure the temperature of a body to be measured simultaneously with spectral emissivity by detecting two kinds of spectral radiation brightness signals which differ in one of the wavelength, polarization, and measured angle of heat radiation from the surface of the body to be measured and performing arithmetic. CONSTITUTION:The surface of a slab 6 which is stationary or conveyed at a slow speed in a high-temperature furnace like a slab heating furnace is irradiated with a known spectral radiation brightness signal from a reference radiation source 1 and a spectral radiometer 2 detects the two kinds of spectral radiation brightness signal components 7 and 8 which differ in one of the wavelength, polarization, and measured angle of the heat radiation from the surface of the slab 6 from each other. The components 7 and 8 are the direct heat radiant light component from the slab 6 and the stray noise signal component from the reference radiation source 1 and two equations represented as the sums of those components and an equation showing the relation between two spectral emissivity values corresponding to the spectral radiation brightness signals, i.e. three equations are solved by an arithmetic processor 3 to measure the temperature and spectral emissivity of the slab 6 at the same time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is an object of the present invention to accurately measure the surface temperature of an object such as a slab that is conveyed stationary or at low speed in a high-temperature heating furnace such as a slab heating furnace in the steel industry. Radiation temperature measurement technology, which measures temperature without adversely affecting objects, can be applied not only to the steel industry but also to many other fields such as non-ferrous metals, ceramics, electronic materials, etc., where the temperature of objects in heating furnaces is measured.

[Conventional technology Taking a varnished slab heating furnace as an example, the most common method of controlling the temperature of the slab inside the heating furnace is to measure the atmosphere temperature inside the furnace with a thermocouple in a protective tube, and thereby adjust the temperature of the slab. It was estimated that With this method, it is difficult to accurately estimate the temperature of the slab, so there are problems in energy cost management, such as requiring a long baking time and setting a high temperature. On the other hand, it is possible to non-contactly measure the surface temperature of an object inside the heating furnace by radiation thermometry, but in this case, removing stray light noise from the inside wall of the heating furnace, etc. becomes a problem. As a radiation thermometry method that can deal with stray light noise, for example, the literature by Benuchi et al.
1, No. 8, pp. 2076-2087), there is a method using a water-cooled shielding plate, but when this method is applied to temperature measurement of objects that are stationary or transported at low speed, such as slabs in a heating furnace, There was a problem in that the water-cooled shield plate cooled the object to be measured, which adversely affected quality.

In addition, as in JP-A-55-155218, unknown stray light noise from the reactor inner wall is removed using a non-water-cooled shielding plate, while the effect of known stray light noise from the non-water-cooled shielding plate is corrected to improve the surface of the slab. There is also a method of measuring temperature, but this method requires complicated calculations for correction, and the emissivity of the slab surface changes due to the generation of scale, which increases the contribution rate of stray light noise from non-water-cooled shielding plates. There were problems such as a risk of measurement errors occurring if the temperature changed.

[Problem to be solved by the invention]

The purpose of the present invention is to measure the temperature of an object to be measured that is stationary or transported at low speed in a high-temperature furnace such as a slab heating furnace, while eliminating the influence of unknown stray light noise from the furnace inner wall, and by measuring the emissivity of the object. The object of the present invention is to propose a method and apparatus for simultaneously measuring

[Means to solve the problem]

The simultaneous temperature and emissivity measurement method of the present invention irradiates the surface of the object to be measured with a known spectral radiance signal using a reference radiation source, and detects any one of the wavelength, polarization, and measurement angle of the thermal radiation from the surface of the object to be measured. Two types of spectral radiance signals that are different from each other are detected, and each of these spectral radiance signals is expressed as the sum of the spectral radiance signal component emitted by the object to be measured and the stray light noise signal component from the reference radiation source. The temperature of the object to be measured and the two spectral emissivities are determined by solving a total of three equations: one equation representing the relationship between the two spectral emissivities corresponding to the spectral radiance signal. It is something.

The simultaneous temperature and emissivity measurement device of the present invention also includes a reference radiation source that irradiates the surface of the object to be measured with a known spectral radiance signal, and a wavelength, polarization, and
Are any of the measurement angles different from each other? means for detecting two types of spectral radiance signals, a calculation device for calculating two corresponding spectral emissivities and temperatures from the two spectral radiance signals, and a temperature of the object to be measured determined by the calculation, 2. and means for inputting parameters for defining a functional relationship between the two spectral emissivities into the arithmetic device, and the arithmetic device receives each spectral radiance signal. 2 expressed as the sum of the spectral radiance signal component emitted by the measurement object and the stray light noise signal component from the reference radiation source.
A total of 3 equations: one equation and one expressing the relationship between two spectral emissivities
This method is characterized by calculating the temperature of the object to be measured and two spectral emissivities by solving two equations.

[For production]

When detecting two types of spectral radiance signals that differ in wavelength, polarization, or measurement angle from the heat radiation from the surface of an object in the furnace, they are calculated using the following formula % formula % () (1) ( ) (2) Where, T: Temperature of the object to be measured Tr: Apparent temperature of the reference radiation source L: Spectral radiance,; Blackbody spectral radiance (known function of temperature) ε: Spectral emissivity x, y: Wavelength, The first term on the right side of the subscripts (1) and (2) expressing the difference in polarization and measurement angle is the direct thermal radiation component from the object to be measured, and the second term is the stray light noise ring from the reference radiation source. .

When the surface properties of the object to be measured change due to oxidation, etc., the three spectral emissivities corresponding to each spectral radiance signal also change, but the formula % (3) expressing the relationship between these two spectral emissivities is known. If so, equations (1) to (3) can be solved numerically, and the three unknowns T, ε8·ε, can be obtained.

This method uses a reference radiation source to create a known stray light noise atmosphere even in an environment where unknown stray light noise exists, such as in a heating furnace, and can be applied to an object whose emissivity fluctuates due to surface oxidation, such as a slab. The temperature and spectral emissivity of the object to be measured can be easily and accurately measured.

When a thermal radiation source is used as a reference radiation source, its temperature T,
Lbx (T, ) is measured using a thermocouple or the like.

The spectral radiance Lby ("rr) of the source surface can be directly referenced using a spectroradiometer.
.

A method of measuring Lby("rr"), etc. can be used.

In addition, when using a reflector such as a mirror as a reference radiation source, the equations (1) and (2> are respectively expressed as -ε8・Lb,
I (T)+ρrX・(1−εX)・Lb, (T)(4
) Ly−ε=′ Lby (T>+ρ, y−(1−εy
) ・Lby (T>(5) However, ρrX' ρ, y: Represented by the effective spectral reflectance of the reflector. Therefore, (3), (4), (
5) Temperature and two spectral emissivities can be determined by solving the equations. The effective spectral reflectance of the reflector may be determined in advance through experiments or the like.

[Examples: Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram conceptually showing a specific example of a measurement system for measuring the temperature of a slab in a heating furnace using the method of the present invention. l is a reference radiation source, 2 is a spectroradiometer for detecting the spectral radiance L8 ・Ly due to two different i, 3
is an arithmetic processing unit, 4 is an input device such as a keyboard for inputting parameters etc. for expressing the functional relationship (3) to the arithmetic processing unit 3, and 5 is the temperature of the object to be measured and the spectral emissivity obtained by the calculation. 6 is the slab that is the object to be measured, 7 is the first right-hand side of equations (1) and (2).
The direct radiance component from the slab, 8, is expressed by the term (1
), (2) is the stray light noise component from the reference radiation source expressed as the second term on the right side of equations (4) and (5).

Although a slab heating furnace is shown in FIG. 1, the reference radiation source may be located within the furnace or outside the furnace. When using a thermal radiation source as a reference radiation source, it is relatively easy to install it inside the furnace, and by increasing the solid angle at which the reference radiation source is viewed from the measurement point, unknown stray light noise from the furnace inner wall can be reduced. It also makes it easier to increase the effect of shielding components. When using a reflector as a reference radiation source, it is desirable to install it outside the reactor in order to keep the effective spectral reflectance of its surface high and constant.

In order to select the wavelength in the spectroradiometer described in 2, there is a method of using, for example, an interference filter5), and to select the polarization component, for example, a polarizing beam splitter or the like can be used. If the measurement angles are different, each radiometer is installed at a different direction and angle, but if the wavelength or polarization is only different, as in the example shown in Figure 1, they are housed in the same housing. You can also do that. Of course, photoelectric conversion elements such as Si, Ge, and PbS can be used depending on the wavelength band. It goes without saying that spectral radiance can also be measured using an optical fiber as a waveguide.

The relational expression between the spectral emissivities was experimentally determined in advance and described using a simple mathematical expression using a polynomial. of course,
Various methods can be used to solve equations, such as using another functional expression or a numerical table.

[Effects of the Invention 2] As described above, according to the present invention, even if an object is conveyed stationary or at low speed in a high-temperature furnace and whose emissivity varies due to changes in surface properties, the object will not be affected by adverse effects such as cooling. Accurate temperature measurements can be taken without overheating. This kind of temperature measurement is expected to be applied to many areas such as slab heating furnaces, continuous annealing furnaces, and high brightness annealing furnaces in the steel industry alone, as well as in the furnaces of non-ferrous metal manufacturing industries, ceramic manufacturing industries, electronic material manufacturing industries, etc. If you also consider its application to temperature measurement, the effects of improving product quality, managing pickled vegetables, saving energy, etc. are immeasurable.

[Brief explanation of drawings]

FIG. 1 is a diagram conceptually showing a specific example of a measurement system for measuring the temperature of a slab in a heating furnace using the method of the present invention. The numbers in the figure are as follows. 1... Reference radiation source, 2... Spectroradiometer, 3
...Arithmetic processing device, 4...Arithmetic parameter input device, 5...Output device, 6...Slab, 7...
・Direct radiation component, 8... Stray light noise component.

Claims (1)

[Claims] 1. The surface of the object to be measured is irradiated with a known spectral radiance signal by a reference radiation source, and the thermal radiation from the surface of the object to be measured has a different wavelength, polarization, or measurement angle. 2. Two equations that detect various types of spectral radiance signals and express each of the spectral radiance signals as the sum of the spectral radiance signal component emitted by the object to be measured and the stray light noise signal component from the reference radiation source; The temperature of the object and the equation representing the relationship between the two spectral emissivities corresponding to the spectral radiance signal, and the temperature of the object to be measured and the two spectral emissivities are determined by solving a total of three equations. Simultaneous emissivity measurement method. 2. A reference radiation source that irradiates a known spectral radiance signal onto the surface of the object to be measured, and two types of spectral radiance signals that differ in wavelength, polarization, or measurement angle among thermal radiation from the surface of the object to be measured. a calculation device for calculating two corresponding spectral emissivities and temperatures from the two spectral radiance signals, and a means for outputting the temperature of the object to be measured and the two spectral emissivities obtained by the calculations. and means for inputting parameters for defining a functional relationship between two spectral emissivities into the arithmetic device, and the arithmetic device calculates each spectral radiance signal from the spectral radiance emitted by the object to be measured. The measured object temperature and A device for simultaneously measuring the temperature and emissivity of an object, characterized by calculating two spectral emissivities. 3. The device for simultaneously measuring the temperature and emissivity of an object according to claim 2, wherein a thermal radiation source is used as the reference radiation source. 4. Simultaneous measurement of temperature and emissivity of an object according to claim 2, characterized in that a reflector is used as the reference radiation source to cause the spectral radiance signal emitted by the object to be measured to re-enter the surface of the object to be measured. measuring device.