Visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra
Disclosed in the present invention is a visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra. Image detectors can be directly inserted into observation holes of a boiler to acquire flame image data, so that when the detection system is applied to a power station boiler, extra holes are not required to be drilled, and therefore, there is no risk that the strength of a furnace wall of the boiler is reduced by drilling holes. According to cross-section temperature fields of a furnace measured by the detection system, the state of combustion in the furnace can be accurately judged, which can play an accurate and effective guiding role in boiler combustion control, and reduce the temperature deviation in each combustion area of the boiler so as to keep the boiler running smoothly, thereby improving the combustion efficiency of the boiler.
1. A visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra, comprising:
synchronously acquiring flame radiation images and spectra in a furnace respectively by image detectors and a spectrometer;
correcting a temperature of a flame image according to an emissivity ratio obtained by an analysis on flame radiation spectra, and according to a reconstruction algorithm based on a radiation intensity imaging model; and
reconstructing simultaneously a temperature distribution and an absorption coefficient distribution in the furnace.
2. The visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra according to claim 1 , wherein a dual-narrow-band pass color filter is installed in front of the image detectors, two central wavelengths λ G and λ R of the dual-narrow-band pass color filter correspond to peaks of spectral response curves of G and R channels of an industrial camera respectively, a half-band width is less than 20 nm, and the emissivity ratio is a ratio ε λ G /ε λ R of emissivities of a flame at central wavelengths of λ G and λ R .
3. The visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra according to claim 1 , wherein the reconstruction algorithm based on the radiation intensity imaging model comprises the following steps:
1) dividing a cross-section of the furnace into m space medium units and n wall units;
2) constructing the radiation intensity imaging model;
3) reconstructing a monochromatic blackbody radiation intensity distribution by using a regularization algorithm, and in a process of calculation, introducing the emissivity ratio obtained by a spectrum analysis to correct a cross-section temperature field reconstruction matrix;
4) updating an absorption coefficient and a scattering coefficient by using a Newton iteration algorithm, and calculating a temperature distribution when a residual is extremely small; and
5) calculating an absorption coefficient distribution by taking the scattering coefficient as a known parameter.
4. The visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra according to claim 1 , wherein there are four image detectors disposed at observation holes on a same layer of the furnace, the four image detectors are perpendicular to an external façade of the furnace and penetrates an inner side of a water-cooled wall, and the four image detectors communicate with a computer equipped with a control software.
5. The visual monitoring method for cross-section temperature fields and radiation characteristics of boiler furnaces by combining radiation images and spectra according to claim 1 , wherein the spectrometer is bundled together with any one of the image detectors, and communicates with a computer through a data line, and a collimating lens is disposed at a front end of an optical fiber of the spectrometer, and the collimating lens is perpendicular to an external façade of the furnace.