Research On Multi-parameters Measurement Of Burning Particles Based On Radiation Spectroscopy And Imaging Method

The combustion of particulate fuel widely exists in the field of energy and power.The parameters including temperature,emissivity and size of burning particles are the important indicators to reflect the combustion state,and the measurement method is one of important tools to research the combustion mechanism of particles.As a non-contact measurement method,radiation spectroscopy and image method can obtain the spectral information and spatial distribution information of burning particles without disturbing the flow field,which is of great significance for the multi-parameter measurement of burning particles with transient,high temperature and strong spontaneous emission.Based on the radiation spectroscopy and imaging method of burning particles,this paper focuses on the combustion of coal particles in boiler,aluminum particles in solid propellant and magnesium particles in high temperature environment.The radiation characteristics of burning particles are mainly studied,and the corresponding emissivity model is obtained to solve the key problems such as the inversion of the radiation spectrum parameters,the imaging and multi-spectral restoration,and the synchronous measurement of multi-parameters of burning particles.The multi-parameter synchronous measurement method of burning particles is developed,and corresponding radiation spectrum inversion and image processing algorithms are formed and the synchronous measurement of size,temperature,emissivity of burning particles is realized.The research result can provide support for the combustion mechanism of boiler coal particles and solid propellant aluminum,magnesium particles.The main research work includes:(1)Based on the generation mechanism of radiation spectrum of burning particles,the measurement method of burning particle temperature and emissivity based on Plank law is studied.Aiming at the influence of the emissivity on radiation spectroscopy,the polynomial fitting and the two-color gray judgment method of the emissivity model are established.On this basis,considering the stability and singal-to-noise ratio of spectral response coefficients at different temperatures and bands,the fitting bands of radiation spectral parameters are optimized to effectively improve the inversion accuracy of temperature and emissivity.In addition,the radiaition spectrum of typical burning particles such as pulverized coal particles,aluminum particles and magnesium particles are taken as examples to analyze the radiation spectra characteristics of different burning particles.Besides,the emissivity model of typical particle combustion is established by polynomial fitting and two-color gray judgment method.(2)Aiming at the thermal deviation problem of the final reheater in the crossover pass of a typical tangential fired 660 MW ultra-supercritical pulverized coal boiler,a multi-parameter measurement system for the burning particle is designed based on the principle of radiation spectroscopy measurement method,which is applied to the experimental measurement of final reheater in crossover pass.The emission spectral characteristics of coal burning particles are discussed,and the distribution of flue gas temperature,burning coal particle temperature and emissivity in different sections in the final reheater area are obtained.The results shows that the coal burning particles at the inlet of the crossover pass still have high radiation intensity and the radiation heat transfer at this position cannot be ignored.The over-fire air can not eliminate residual rotation and can not effectively prevent the single-side accumulation of coal burning particles.Combined with the delayed burn-out,the uneven radiation heat transfer on the heating surface is the main reason for the deviation of temperature rise on the steam side of the final reheater.In addition,by adjusting the angle of over-fire air in the horizontal and vertical directions,the phenomenon of single-side accumulation of high-temperature particles can be significantly reduced,the deviation of radiation intensity on both sides can be balanced,and the thermal deviation on steam side of final reheater can be effectively controlled.(3)The measurement method of temperature and emissivity distribution of burning particles based on RGB radiation image is studied.The blackbody furnace is used as the standard radiation source.Combined with the R,G and B response characteristics of the camera,the algorithm of temperature and emissivity distribution based R and G dual bands is established,and the corresponding experimental verification and influencing factors are studied.On this basis,the parameters of burning aluminum,magnesium particles are measured using the high temperature combustion experimental system,and the temperature and emissivity distribution of the burning particles are obtained.In order to solve the influence of radiation characteristics of different components of burning particles on the measurement results,the measurement method of multi-spectral imaging is studied.The measurement error of temperature and emissivity distribution is reduced.Aiming at the problems of low spectral resolution of RGB images and low spatial resolution of multi-spectral images,a dual-camera image registration method based on beam-splitting mode and a spectral reconstruction method based an artificial neural network are proposed.The experimental system for synchronous acquisition of RGB and multi-spectral radiation images is built,and the synchronous acquisition and texture registration of RGB and spectral radiation images are realized.The multi-spectral reconstruction of RGB radiation images is realized by using the neural network model.This method can satisfy the characteristics of multispectral resolution and high spatial resolution simultaneously.(4)Aiming at the problem of synchronous measurement of particle size and radiation parameters in particle combustion process,a dual-camera synchronous measurement method combining blue backlight and radiation image is studied.In the beam split mode,the blue light backlight method is used to obtain the backlight image of burning particles,which can effectively eliminate the influence of particle radiation signal on particle size measurement.A band-pass filter is used to obtain the radiation image of the burning particles,so as to realize the synchronous acquisition of particle size information and radiation information.An optimization algorithm of defocused particle size analysis based on gray gradient is proposed.On this basis,the dual-camera synchronous measurement method combining the blue backlight and radiation images is applied to measure the combustion process of aluminum particles in solid propellant.In this way,the backlight image and radiation image of aluminum particles are obtained simultaneously,and the agglomeration process of aluminum particles on the burning surface of solid propellant is analyzed.