CN117848512A - Method and system for detecting temperature distribution of heating surface of boiler based on infrared spectrum - Google Patents
Method and system for detecting temperature distribution of heating surface of boiler based on infrared spectrum Download PDFInfo
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Abstract
The invention belongs to the field of temperature detection, and particularly discloses a method and a system for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum, wherein the method comprises the following steps: s1, collecting infrared spectrum signals and infrared thermal radiation images in a heating surface area of a boiler; s2, converting the infrared spectrum signal into spectrum radiation intensity, and separating spectrum radiation intensity absorbed by a combustion gas medium in the furnace from the spectrum radiation intensity; s3, calculating infrared emissivity of the heating surface based on the spectrum radiation intensity; s4, converting the infrared thermal radiation image into a wave band radiation intensity image, and combining the spectral radiation intensity absorbed by the combustion gas medium in the furnace to obtain an infrared wave band radiation intensity image from the heating surface; s5, obtaining the temperature distribution of the heating surface of the boiler according to the infrared band radiation intensity image from the heating surface and the infrared emissivity of the heating surface. The invention can realize the accurate on-line measurement of the temperature distribution of the heating surface of the boiler.
Description
Technical Field
The invention belongs to the field of temperature detection, and particularly relates to a method and a system for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum.
Background
The boiler heating surface of the thermal power plant mainly comprises a water cooling wall, a superheater, a reheater, an economizer and the like, and is used for absorbing heat from flue gas in the boiler so as to obtain steam with specified parameters (temperature and pressure) and quality. When the combustion in the furnace is unstable, the local heat load in the furnace is too high, and the flame center moves upwards or deflects, the overheat of the heating surface is easily caused; in the same way, when foreign matters are blocked or the scale is too much in the heat exchange tube of the heating surface, uneven steam-water distribution and poor steam-water circulation can be caused, thereby affecting the heat transfer performance, obviously increasing the temperature of the tube wall of the heating surface, and causing the problem of overheat explosion of the tube of the heating surface when serious. Therefore, the real-time on-line monitoring of the temperature of the heating surface is of great significance for preventing the overtemperature of the pipe wall.
The detection of the temperature distribution of the heating surface is mainly two types, namely, a plurality of contact point temperature measuring devices such as thermocouples, optical fiber temperature sensors and the like are arranged on the back fire side of the heating surface, and the overtemperature condition of the heating surface on the fire side in the furnace is indirectly judged; the other type is to directly obtain an infrared thermal radiation image of the heating surface in the furnace by adopting a non-contact optical measurement method, and obtain the temperature of the heating surface through processing the infrared image, such as a widely-used thermal infrared imager. However, it should be noted that, in the application of temperature measurement, the thermal infrared imager needs to know the emissivity of the measured object in the infrared temperature measurement band to obtain the accurate temperature, while the emissivity of the heated surface is unknown and can change with the temperature when the boiler is in operation, and meanwhile, particles and gas mediums in the combustion flame in the boiler can emit strong heat radiation in the infrared band and are superimposed on the infrared radiation emitted by the heated surface of the hearth, so that the temperature result of the heated surface detected by the thermal infrared imager has larger error. In order to solve this problem, patent 202211282353.6 proposes to build a detection model of radiation intensity of the heating surface and radiation intensity of flame to obtain radiation information of the heating surface through flame, and this method requires a large amount of accurate radiation imaging calculation, and in particular, it is difficult to determine the energy share of the three of the heating surface emitted by the boiler, the heating surface emitted by the flame scattered, the heating surface emitted by the flame directly received by the photosensitive element, and it is also difficult to obtain the energy share of the three of the heating surface emitted by the boiler, the flame emitted by the flame scattered, and the flame emitted by the flame directly received by the photosensitive element, and is not suitable for industrial application of online monitoring of wall temperature distribution of the heating surface in the boiler field environment.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a method and a system for detecting the temperature distribution of a heating surface of a boiler based on infrared spectrum, and aims to realize accurate online measurement of the temperature distribution of the heating surface of the boiler.
In order to achieve the above object, according to an aspect of the present invention, there is provided a method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum, comprising the steps of:
s1, collecting infrared spectrum signals and infrared thermal radiation images in a heating surface area of a boiler;
s2, converting the infrared spectrum signal into spectrum radiation intensity, and separating spectrum radiation intensity absorbed by a combustion gas medium in the furnace from the spectrum radiation intensity;
s3, calculating infrared emissivity of the heating surface based on the spectrum radiation intensity;
s4, converting the infrared thermal radiation image into a wave band radiation intensity image, and combining the spectral radiation intensity absorbed by the combustion gas medium in the furnace to obtain an infrared wave band radiation intensity image from the heating surface;
s5, obtaining the temperature distribution of the heating surface of the boiler according to the infrared band radiation intensity image from the heating surface and the infrared emissivity of the heating surface.
As a further preferred, step S2 comprises the steps of:
converting an infrared spectral signal into a spectral radiation intensity I b1 (lambda) and determining the wavelength range of the absorption peak as (lambda) from the intensity of the spectral radiation `1 ,λ 2 )；
Spectral radiation intensity I 'of heated surface after being absorbed by combustion gas medium in furnace' q1 The method comprises the following steps:
intensity of spectral radiation I absorbed by gaseous medium in furnace q1 The method comprises the following steps:
wherein λ is the wavelength, (λ) a ,λ b ) A detection wavelength range when a spectrum signal is collected for the spectrometer; i' b1 (lambda) is the spectral radiant intensity of the heated surface not absorbed by the gaseous medium in the furnace, and is determined by: at (lambda) `a ,λ `1 ) And (lambda) `2 ,λ `b ) Near lambda in two intervals `1 And lambda is `2 The spectrum radiation intensity corresponding to a plurality of wavelengths is selected from the sides, and fourth polynomial fitting is carried out, and I 'is obtained according to the fourth polynomial obtained by fitting' b1 (λ)。
As a further preferred, step S3 comprises the steps of:
the monochromatic emissivity epsilon (lambda) of the heating surface of the hearth at the measuring point of the spectrometer is expressed as:
wherein I (λ) is the spectral radiation intensity at wavelength λ:
I b (lambda, T) is the blackbody spectrum radiation intensity at the heating surface temperature T at the measuring point:
wherein C is 1 Is Planck first constant, C 2 A planck second constant;
at (lambda) a ,λ b ) Taking M wavelengths in the range to obtainTo M pieces of monochromatic emissivity data, and further obtaining the infrared emissivity of the heating surface through statistical average
Wherein ε i And (lambda) is the monochromatic emissivity of the heating surface of the hearth corresponding to the ith wavelength.
As a further preferred step S3, the monochromatic emissivity ε is calculated i (lambda) relative mean square error sigma ε If the value is smaller than the preset threshold value, continuing the subsequent steps; otherwise, the spectrometer station position is changed and the process returns to step S1.
As a further preferred, step S4 comprises the steps of:
establishing a function model of chromaticity information and band radiation intensity of an infrared thermal radiation image:
wherein I is b2 Gray' is the chromaticity information of the infrared thermal radiation image, b m Fitting coefficients for a polynomial of the model; m represents the order of the function model;
converting the collected infrared thermal radiation image into a wave band radiation intensity image I according to a function model b2 ；
And then image I according to the wave band radiation intensity b2 Intensity of spectral radiation I combined with absorption by gaseous medium in combustion in furnace q1 Obtaining an infrared band radiation intensity image I 'from the heating surface' b2 。
As a further preference, step S4, the polynomial fitting coefficients b of the model are determined m The method of (1) is as follows:
presetting a series of temperatures, and acquiring blackbody furnace infrared thermal radiation images with multiple integration times and initial chromaticity information of the blackbody furnace infrared thermal radiation images at each preset temperature;
performing linear fitting on each integration time at each preset temperature and the corresponding initial chromaticity information to obtain the following linear fitting function:
Gray k (T)＝at+ε
wherein Gray k The chromaticity information corresponding to different integration time of the kth calibration experiment at the preset temperature T is obtained, and T is the integration time; a is a slope and represents standard chromaticity information obtained by a single calibration experiment; epsilon is the intercept and represents dark noise;
denoising the chrominance information according to the following formula to obtain denoised chrominance information Gray' k (T)：
Further calculating denoising chromaticity information Gray 'of n calibration experiments at each preset temperature' k The average value of the (T) is the standard chromaticity information Gray' (T) of the infrared thermal radiation image of the blackbody furnace;
substituting standard chromaticity information Gray' (T) and band radiation intensity at corresponding temperature T into a function model of chromaticity information and band radiation intensity of the infrared thermal radiation image, and solving to obtain a polynomial fitting coefficient b of the function model m 。
As a further preferred aspect, in step S5, the calculation formula of the temperature distribution of the heating surface of the boiler is:
wherein T (x, y) is the temperature of the pixel point (x, y), C 1 Is Planck first constant, C 2 Is the Planck second constant, lambda is the wavelength; i' b2 (x, y) is the infrared band radiation intensity from the pixel point (x, y) in the infrared band radiation intensity image of the heated surface,is heated to be redExternal emissivity.
According to another aspect of the present invention, there is provided a detection system for implementing the above-mentioned infrared spectrum-based method for detecting temperature distribution of a heated surface of a boiler, including an information acquisition module and a data storage calculation module, wherein:
the information acquisition module is used for realizing the step S1; the data storage computing module comprises a processor, a memory and a computer program stored in the memory and capable of running in the processor, wherein the steps S2-S5 are realized when the processor executes the computer program, and the data after the computing processing is stored in the memory.
As a further preferred aspect, the information acquisition module includes an infrared imaging lens, a spectroscope, a collimator lens, a spectrometer, and a thermal infrared imager, wherein:
the optical axis of the infrared imaging lens is perpendicular to the heating surface of the boiler, and the infrared thermal imager is arranged at the position of outputting imaging by the optical path of the infrared imaging lens; the spectroscope is arranged between the infrared imaging lens and the infrared thermal imager, and the optical axis of the spectroscope and the optical axis of the infrared imaging lens are 45 degrees; the spectrometer is arranged in the light splitting direction of the spectroscope.
As a further preferred option, a display module is also included which displays the temperature distribution of the heating surface of the boiler in the form of pseudo-colors and/or contours.
In general, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. according to the invention, the infrared spectrum signal and the infrared thermal radiation image are combined, the emissivity of the heating surface in the measurement wavelength range is obtained on line through infrared spectrum analysis, and then emissivity data is output to an infrared thermal imaging temperature measurement method, so that the rapid and accurate on-line measurement of the temperature distribution of the heating surface is realized.
2. Based on infrared spectrum information, a discontinuous spectrum part from an in-furnace combustion gas medium and a continuous spectrum part from a heating surface are separated, so that the spectrum radiation intensity absorbed by the in-furnace combustion gas medium is obtained, and then an infrared band radiation intensity image from the heating surface is obtained by combining an infrared thermal radiation image; the influence of the combustion gas in the boiler on the spontaneous radiation absorption of the heating surface of the boiler can be reduced, and the accuracy of the temperature detection of the heating surface of the boiler is improved.
3. The invention combines the advantages of high spectral resolution of the spectrometer with the advantages of large imaging range and temperature measurement technology of the infrared camera, can realize industrial application and simultaneously remarkably improves the calculation precision of the temperature of the heating surface of the boiler. Meanwhile, the invention does not need a large amount of radiation imaging process calculation, the measuring device has simple structure, is easy to realize, is suitable for accurately detecting the temperature distribution of the heating surface of the boiler of the thermal power plant, and can realize the observation and the measurement of the temperature distribution of the heating surface of the boiler.
Drawings
FIG. 1 is a flow chart of a method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum in an embodiment of the invention;
FIG. 2 is a schematic diagram of a structure of an information acquisition module according to an embodiment of the present invention;
FIG. 3 is a graph showing the radiation intensity distribution of the short-wave infrared spectrum of the heating surface of the boiler according to the embodiment of the invention;
FIG. 4 is a graph showing the spectral radiant intensity distribution of the heated surface of the boiler with the influence of the absorption of the combustion gas in the boiler subtracted in accordance with an embodiment of the present invention;
FIG. 5 is a fourth order polynomial fit of the intensity of IR radiation versus standard gray level according to an embodiment of the invention;
FIG. 6 is a graph showing the spectral radiant intensity distribution of the heated surface of a boiler fitted by a fourth order polynomial after subtracting the influence of the absorption of the combustion gas in the furnace according to the embodiment of the present invention;
fig. 7 is a schematic structural diagram of a detection system according to an embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The method for detecting the temperature distribution of the heating surface of the boiler based on the infrared spectrum provided by the embodiment of the invention, as shown in fig. 1, comprises the following steps:
s1, collecting infrared spectrum signals and infrared thermal radiation images in a heating surface area of a boiler.
Specifically, an infrared thermal imaging device is used for collecting infrared thermal radiation images of a heating surface of a boiler, the position of an infrared thermal imaging lens is adjusted to be aligned with the heating surface of the boiler to be detected, the integral time of a camera is adjusted to ensure that the images are free from saturation, and the infrared thermal radiation images under different integral times are shot. Meanwhile, the infrared spectrum signal of the heating surface of the boiler is collected by utilizing a spectrometer, in the embodiment, the collected spectrum signal is in a short wave infrared band, and the wavelength range is (lambda) a ,λ b )，λ a ＝1150nm，λ b ＝1650nm。
S2, converting the infrared spectrum signal into spectrum radiation intensity I b1 (lambda) and thus the spectral radiation intensity I of the absorption of the combustion gas in the furnace q1 。
S21, converting the infrared spectrum signal into spectrum radiation intensity I b1 (λ)。
Calibrating a spectrometer by using a blackbody furnace as a standard radiation heat source, and converting short-wave infrared spectrum signal data of the spectrometer into spectrum radiation intensity data to obtain a calibration coefficient f 1 (lambda). Spectral radiation intensity I b1 (lambda) can be determined from the spectral signal data I (lambda) of the spectrometer and the calibration factor f 1 (lambda) obtained:
I b1 (λ)＝f 1 (λ)×I(λ)
s22, according to the spectral radiation intensity I b1 (lambda) determining the wavelength range of the absorption peak, dividing the spectral radiation intensity distribution, and further determining the spectral radiation intensity I of the absorption of the combustion gas in the furnace q1 。
The heated surface of the boiler can be regarded as an ash body and has continuous spectral emission characteristics. The gas radiation has a strong selectivity for wavelength, having radiation and absorption capacity only in specific wavelength regions. Emitted by the heated surface of the boilerThe spectrum radiation is absorbed by the medium of the combustion gas in the furnace before being accepted by the spectrometer, and the obtained spectrum radiation intensity data has obvious absorption peak with the wavelength range of (lambda) because the combustion gas has specific absorption spectrum wavelength `1 ,λ 2 )。λ `1 And lambda is `2 The spectrum radiation intensity data in between is the discontinuous spectrum radiation intensity distribution after being absorbed by the combustion gas medium in the furnace, lambda `1 And lambda is `2 The other spectral radiant intensity data are continuous spectral radiant intensity distributions from the heated surfaces of the boiler. In this embodiment, the spectral radiant intensity distribution of the heating surface of the boiler is shown in FIG. 3, and lambda can be seen `1 ＝1318.96nm，λ `2 ＝1493.74nm。
The spectral radiation intensity of the heated surface after being absorbed by the combustion gas medium in the furnace is represented by lambda `1 And lambda is `2 The integral of the band radiation intensity between the two is obtained:
in the above, I' q1 The subscript 1 indicates that the data is from the spectrometer for the spectral radiant intensity of the heated surface after absorption by the combustion gas medium in the furnace.
The spectral radiation intensity of the combustion gas absorption in the furnace is:
in the above, I q1 The spectrum radiation intensity of the gas absorbed by the combustion gas in the furnace is 1150-1650 nm in the detection range of short wave infrared by a spectrometer;indicating the heating surface of the boiler at lambda 1 ～λ 2 Spectral radiation intensity not absorbed by the combustion gas in the furnace in between,/->The spectrum radiation intensity received by the spectrometer except the combustion gas absorption band in the short wave infrared range is represented.
Further, I' b1 The determination method of (lambda) is as follows:
subtracting lambda from continuous spectrum signal obtained by spectrometer `1 And lambda is `2 Signal data therebetween, and performing a polynomial fitting operation on the remaining spectral signal data, e.g. subtracting λ in fig. 3 `1 And lambda is `2 And obtaining the signal data in the figure 4, and performing polynomial fitting on the spectrum signal data and the wavelength in the figure 4.
The specific method comprises the following steps: at (1150, lambda) `1 ) And (lambda) `2 1650) near lambda in two intervals `1 And lambda is `2 15-20 spectrum radiation intensity data are selected from each side to carry out fourth polynomial fitting, so that the heating surface lambda of the boiler can be obtained `1 ～λ `2 Spectral radiant intensity I 'not absorbed by combustion gases in the furnace' b1(λ) At lambda `1 ～λ `2 Fitting formulas between them as shown in fig. 6.
The resulting fourth order polynomial fit formula is:
I′ b1 ＝I 0 +B 1 λ+B 2 λ 2 +B 3 λ 3 +B 4 λ 4 (λ 1 ≤λ≤λ 2 )
in order to ensure the accuracy of the subsequent calculation, the above formula is only applied to the range of lambda 1 ≤λ≤λ 2 Can be used in the formula I 0 Intercept for polynomial fitting of degree four (unit W/(m) 3 ×sr))，B 1 ,B 2 ,B 3 ,B 4 For the fourth order polynomial coefficients, I' b1 Is the spectral radiant intensity (unit W/(m) 3 ×sr))。
S3, calculating emissivity distribution of the heating surface in a short-wave infrared band, and obtaining the short-wave infrared emissivity of the heating surface through statistical average
S31, calculating emissivity distribution of the heating surface in a short wave infrared band:
calculating the temperature of a heating surface of a hearth at a measuring point of a spectrometer by using a multi-wavelength method:
in the above formula: t is the temperature of a heating surface of the hearth, the unit is Kelvin (K), and M is the wavelength number used for calculation; c (C) 2 The second constant of Planck is 1.4388 ×10 -16 In watts per square meter (W/m) 2 )；λ i For the i-th wavelength, in nanometers (nm), i=1, 2 … M; Δλ is the increase in wavelength in nanometers (nm).
According to the wien's law of displacement:
I(λ,T)＝ε(λ)I b (λ,T)
the single-color emissivity epsilon (lambda) of the heating surface of the hearth at the measuring point of the spectrometer can be expressed by the ratio of the radiation intensity to the blackbody radiation intensity at the same temperature T:
in the above formula, I (λ) is the spectral radiation intensity at wavelength λ:
I b (λ, T) is the blackbody spectral radiant intensity at the wavelength λ and the determined temperature T:
s32, obtaining the shortwave infrared emissivity of the heating surface through statistical average
According to the method in S31, M wavelengths are taken at equal intervals in the short-wave infrared wavelength range of (1150,1650), and M monochromatic emissivity epsilon of a heating surface of a hearth at a measuring point of a spectrometer is correspondingly calculated i (lambda) data, and thus the average value thereofAnd the relative mean square error sigma ε ：
In the above-mentioned method, the step of,namely the statistical average value sigma of the shortwave infrared emissivity of the heating surface ε Is the relative mean square error of ε (λ), if σ ε Below a preset threshold (set to 5% in this embodiment), it is considered that in the short-wave infrared range of (1150,1650), the radiation of the heated surface of the boiler can be regarded as gray-body radiation, and the following steps can be continued if σ ε And if the measured point is more than or equal to 5%, the measured point position of the spectrometer needs to be replaced, and the step S1 is repeated.
S4, converting the infrared thermal radiation image into a wave band radiation intensity image, and combining the spectral radiation intensity of the combustion gas absorption in the furnace to eliminate the influence of the combustion gas medium absorption in the furnace so as to obtain the infrared wave band radiation intensity image from the heating surface.
S41, calibrating the infrared thermal imager through a blackbody furnace, and further converting the infrared thermal radiation image into a wave band radiation intensity image I b2 ：
S411, establishing infrared thermal radiation image chromaticity information Gray' and band radiation intensity I obtained by an infrared thermal imager b2 The functional model of (2) is as follows:
in the above, b m And fitting coefficients for polynomials of the first initial function model, wherein m is a positive integer and represents the order of the function model.
S412, setting a series of preset temperatures, and obtaining blackbody furnace short-wave infrared images with multiple integration times and initial chromaticity information of each short-wave infrared image at each preset temperature of the blackbody furnace through an infrared thermal imager. The preset temperature is 600-2200 deg.c, and includes basically all the temperatures of the heated surface of the boiler.
For each preset temperature: a series of integration times (typically 8) are set, and each integration time is subjected to a plurality of repeated experiments (typically 3 times); performing linear fitting on each integration time and the corresponding initial chromaticity information to obtain a linear fitting function of the integration time and the initial chromaticity information at each preset temperature:
Gray k (T)＝at+ε
in the above, gray k And (T) is chromaticity information corresponding to different integration time of the kth calibration experiment at the set temperature T, T is the integration time, a is the slope, and represents standard chromaticity information obtained by a single calibration experiment, epsilon is the intercept, and represents dark noise.
Subtracting the intercept of the fitting function corresponding to the corresponding preset temperature from each piece of initial chromaticity information, and dividing the intercept by the integral time corresponding to the initial chromaticity information to obtain denoising chromaticity information:
calculating the average value of denoising chromaticity information of all calibration experiments at a preset temperature, and taking the average value as standard chromaticity information of a near infrared image of a blackbody furnace at a corresponding preset temperature:
in the above formula, n is the total number of calibration experiments at each preset temperature.
Then, a plurality of groups of standard chromaticity information corresponding to the preset temperature T are obtained through the method.
S413, standard chromaticity information Gray' (T) of the blackbody furnace near-infrared image obtained in S412 is processed to obtain corresponding band radiation intensity I b2 (T) (obtained according to the temperature T and the corresponding wavelength at the maximum response of the infrared thermal imager) is substituted into the function model of S411, and the polynomial fitting coefficient b of the function model is obtained by solving m As shown in fig. 5; further converting the infrared thermal radiation image acquired by the S1 into a wave band radiation intensity image I according to a function model b2 。
S42, according to the wave band radiation intensity image I b2 And intensity of spectral radiation I absorbed by combustion gases in the furnace q1 Determining an infrared band radiation intensity image I 'from a heated surface' b2 。
Adding the radiation intensity of each pixel point of the infrared thermal radiation image shot by the short-wave infrared thermal imager to the radiation intensity of the combustion gas medium in the furnace to obtain short-wave infrared band radiation intensity image data of each pixel point from a heating surface:
I′ b2 (x,y)＝I b2 (x,y)+I q1
in the above, I' b2 (x, y) is the band radiation intensity from the heating surface of the pixel point (x, y) of the infrared thermal radiation image, I b2 And (x, y) is the band radiation intensity of the pixel points (x, y) without deducting the influence of the absorption of the combustion gas medium in the furnace.
According to the corresponding wave band radiation intensity I 'of each pixel point' b2 (x, y) to obtain the radiation intensity of the whole short-wave infrared image frame of the heating surface of the boiler, namely the infrared band radiation intensity image I 'from the heating surface' b2 。
S5, obtaining the temperature distribution of the heating surface of the boiler according to the infrared band radiation intensity image from the heating surface and the infrared emissivity of the heating surface.
Based on the infrared heat radiation law, a quantitative relation between the radiation intensity of the short-wave infrared band and the short-wave infrared emissivity and the temperature is established.
In the short-wave infrared wavelength range of (1150,1650), there are, according to wien's law of displacement:
then the expression of the temperature of the pixel point (x, y) in the short wave infrared image can be obtained by inverse solution from the above expression:
the radiation intensity image data I (x, y) =I 'of the heating surface short wave infrared band obtained in the step S4' b2 (x, y) and the shortwave infrared emissivity of the heating surface obtained in the step S3Substituting the temperature distribution of the heating surface of the boiler into the above formula to obtain the temperature distribution of the heating surface of the boiler:
in the above formula, T (x, y) is the temperature of the pixel point (x, y), C 1 The Planck first constant is 3.7X10 -16 In watts per square meter (W/m) 2 )，C 2 The second constant of Planck is 1.4388 ×10 -16 In watts per square meter (W/m) 2 )。
The embodiment of the invention also provides a detection system for realizing the method for detecting the temperature distribution of the heating surface of the boiler based on the infrared spectrum, as shown in fig. 7, the detection system comprises an information acquisition module, a data storage calculation module and a display module, wherein:
the information acquisition module is used for realizing the step S1;
the data storage computing module comprises a processor, a memory and a computer program which is stored in the memory and can run in the processor, wherein the steps S2-S5 are realized when the processor executes the computer program, and the data after the computing processing is stored in the memory;
the display module displays the temperature distribution of the heating surface of the boiler in a pseudo-color and/or contour line mode.
Further, as shown in fig. 2, the information acquisition module includes an infrared imaging lens, a spectroscope, a collimating lens, a spectrometer and a thermal infrared imager fixed on a substrate, wherein:
the infrared imaging lens is arranged on the outer side of the heating surface of the boiler, and the infrared thermal imager is arranged at the position of the optical path output imaging of the infrared imaging lens; the spectroscope is arranged between the infrared imaging lens and the infrared thermal imager, and the optical axis of the spectroscope and the optical axis of the infrared imaging lens form 45 degrees; the spectrometer is arranged in the light splitting direction of the spectroscope; by the arrangement, the same beam of light from the heating surface is received by the spectrometer and the infrared thermal imager. In addition, in order to ensure that the signal received by the spectrometer is the self-emission spectrum of the heating surface of the boiler along the sight line direction, a collimating lens provided with an optical fiber is connected in front of an inlet slit of the spectrometer, so that the spectrometer can obtain the self-emission short-wave infrared spectrum intensity of the heating surface of the boiler. The spectrometer and the infrared thermal imager are respectively connected with the data storage calculation module through a spectrometer interface and an infrared thermal imager interface.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. The method for detecting the temperature distribution of the heating surface of the boiler based on the infrared spectrum is characterized by comprising the following steps of:
s1, collecting infrared spectrum signals and infrared thermal radiation images in a heating surface area of a boiler;
s2, converting the infrared spectrum signal into spectrum radiation intensity, and separating spectrum radiation intensity absorbed by a combustion gas medium in the furnace from the spectrum radiation intensity;
s3, calculating infrared emissivity of the heating surface based on the spectrum radiation intensity;
s4, converting the infrared thermal radiation image into a wave band radiation intensity image, and combining the spectral radiation intensity absorbed by the combustion gas medium in the furnace to obtain an infrared wave band radiation intensity image from the heating surface;
s5, obtaining the temperature distribution of the heating surface of the boiler according to the infrared band radiation intensity image from the heating surface and the infrared emissivity of the heating surface.
2. The method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum according to claim 1, wherein the step S2 comprises the steps of:
converting an infrared spectral signal into a spectral radiation intensity I b1 (lambda) and determining the wavelength range of the absorption peak as (lambda) from the intensity of the spectral radiation `1 ,λ 2 )；
Spectral radiation intensity I 'of heated surface after being absorbed by combustion gas medium in furnace' q1 The method comprises the following steps:
intensity of spectral radiation I absorbed by gaseous medium in furnace q1 The method comprises the following steps:
wherein λ is the wavelength, (λ) a ,λ b ) A detection wavelength range when a spectrum signal is collected for the spectrometer; i' b1 (lambda) is the spectral radiant intensity of the heated surface not absorbed by the gaseous medium in the furnace, and is determined by: at (lambda) `a ,λ `1 ) And (lambda) `2 ,λ `b ) Near lambda in two intervals `1 And lambda is `2 The side selects the spectrum radiation intensity corresponding to a plurality of wavelengths and carries outFitting a fourth polynomial, and obtaining I 'according to the fourth polynomial obtained by fitting' b1 (λ)。
3. The method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum according to claim 2, wherein the step S3 comprises the steps of:
the monochromatic emissivity epsilon (lambda) of the heating surface of the hearth at the measuring point of the spectrometer is expressed as:
wherein I (λ) is the spectral radiation intensity at wavelength λ:
I b (lambda, T) is the blackbody spectrum radiation intensity at the heating surface temperature T at the measuring point:
wherein C is 1 Is Planck first constant, C 2 A planck second constant;
at (lambda) a ,λ b ) Taking M wavelengths in the range to correspondingly obtain M monochromatic emissivity data, and further obtaining the infrared emissivity of the heating surface through statistical average
Wherein ε i And (lambda) is the monochromatic emissivity of the heating surface of the hearth corresponding to the ith wavelength.
4. The method for detecting temperature distribution of heating surface of boiler based on infrared spectrum as set forth in claim 3, wherein step S3, the single-color emissivity epsilon is calculated i (lambda) relative mean square error sigma ε If the value is smaller than the preset threshold value, continuing the subsequent steps; otherwise, the spectrometer station position is changed and the process returns to step S1.
5. The method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum according to claim 1, wherein the step S4 comprises the steps of:
establishing a function model of chromaticity information and band radiation intensity of an infrared thermal radiation image:
wherein I is b2 Gray' is the chromaticity information of the infrared thermal radiation image, b m Fitting coefficients for a polynomial of the model; m represents the order of the function model;
converting the collected infrared thermal radiation image into a wave band radiation intensity image I according to a function model b2 ；
And then image I according to the wave band radiation intensity b2 Intensity of spectral radiation I combined with absorption by gaseous medium in combustion in furnace q1 Obtaining an infrared band radiation intensity image I 'from the heating surface' b2 。
6. The method for detecting temperature distribution of a heating surface of a boiler based on infrared spectrum as set forth in claim 5, wherein step S4, a polynomial fitting coefficient b of a model is determined m The method of (1) is as follows:
presetting a series of temperatures, and acquiring blackbody furnace infrared thermal radiation images with multiple integration times and initial chromaticity information of the blackbody furnace infrared thermal radiation images at each preset temperature;
performing linear fitting on each integration time at each preset temperature and the corresponding initial chromaticity information to obtain the following linear fitting function:
Gray k (T)＝at+ε
wherein Gray k The chromaticity information corresponding to different integration time of the kth calibration experiment at the preset temperature T is obtained, and T is the integration time; a is a slope and represents standard chromaticity information obtained by a single calibration experiment; epsilon is the intercept and represents dark noise;
denoising the chrominance information according to the following formula to obtain denoised chrominance information Gray' k (T)：
Further calculating denoising chromaticity information Gray 'of n calibration experiments at each preset temperature' k The average value of the (T) is the standard chromaticity information Gray' (T) of the infrared thermal radiation image of the blackbody furnace;
substituting standard chromaticity information Gray' (T) and band radiation intensity at corresponding temperature T into a function model of chromaticity information and band radiation intensity of the infrared thermal radiation image, and solving to obtain a polynomial fitting coefficient b of the function model m 。
7. The method for detecting temperature distribution of a heated surface of a boiler based on infrared spectrum according to any one of claims 1 to 6, wherein in step S5, the calculation formula of the temperature distribution of the heated surface of the boiler is:
wherein T (x, y) is the temperature of the pixel point (x, y), C 1 Is Planck first constant, C 2 Is the Planck second constant, lambda is the wavelength; i' b2 (x, y) is the infrared band radiation intensity from the pixel point (x, y) in the infrared band radiation intensity image of the heated surface,is the infrared emissivity of the heating surface.
8. A detection system for implementing the infrared spectrum-based method for detecting the temperature distribution of the heated surface of a boiler according to any one of claims 1 to 7, comprising an information acquisition module and a data storage calculation module, wherein:
the information acquisition module is used for realizing the step S1; the data storage computing module comprises a processor, a memory and a computer program stored in the memory and capable of running in the processor, wherein the steps S2-S5 are realized when the processor executes the computer program, and the data after the computing processing is stored in the memory.
9. The detection system of claim 8, wherein the information acquisition module comprises an infrared imaging lens, a beam splitter, a collimating lens, a spectrometer, and a thermal infrared imager, wherein:
the optical axis of the infrared imaging lens is perpendicular to the heating surface of the boiler, and the infrared thermal imager is arranged at the position of outputting imaging by the optical path of the infrared imaging lens; the spectroscope is arranged between the infrared imaging lens and the infrared thermal imager, and the optical axis of the spectroscope and the optical axis of the infrared imaging lens are 45 degrees; the spectrometer is arranged in the light splitting direction of the spectroscope.
10. The detection system according to claim 8 or 9, further comprising a display module displaying the boiler heating surface temperature distribution in pseudo-color and/or contour.
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