The Measurement Of Temperature Field Of Flame Based On The Study Of Multispectral Thermometry

Flame temperature is an important parameter that reflects the combustion reaction process.And it is also critical to understand the heat produced in the combustion process and the heat transfer occurred in a certain space.Thermal radiation problem must be considered in the flame of supercharged boiler,the real-time monitoring of furnace temperature and the boiler performance evaluation.At the same time the heat resistance performance around the furnace wall must be considered in the combustion process.Therefore,the cognition of the heat transfer in the furnace,the temperature field and the radiation characteristics is the foundation of the boiler design.And it's the key to optimize the combustion parameters and to increase the combustion efficiency.The solution to all of these problems can not do without the measurement of the flame temperature.The most effective way to measure the temperature field of the flame is to use the multispectral analysis.The true temperature of flame is not clear in the actual combustion process because the spectral emissivity of the flame is unknown.In this paper,a spectrometer is used to measure the radiation spectrum of hydrocarbon flame,and a multispectral analysis method is used to analyse and obtain the change law of spectral emissivity vs.wavelength and temperature,and then calculate the temperature of the flame.The research work was summarized as follows.(1)Inversion algorithm research on the multispectral radiation thermometryThe spectral emissivity of tested object must be known in order to obtain the true temperature,which is the key problem of the multispectual radiation thermometry.In this paper,a novel iterative algorithm which is no need to assume the spectral emissivity is proposed on the basis of the mathematical model of the second measurement method based on the reference temperature,and the simulation calculation with variety of emissivity assumption models were carried on in different cases,which established a foundation to improve the accuracy of measurement.(2)Temperature compensation algorithm research based on Mie scatteringThe light scattering generated by CO2,H2O and Soot etc would influence the spectrum,which would actually influence the result of temperature.So we need to correct the result.In this paper,a calculation model of temperature compensation is proposed on the basis of the Mie scattering characteristics of particulate matter.At the same time the simulation of different models were carried on.(3)Reconstruction algorithm research on temperature field of flameThe temperature measuring system just can get part of informations radiated by flame in locale.How to improme the reconstruction accuracy is the key problem to solve in the condition of little projective data.A novel iteration reconstruction algorithm is proposed based on the advantage of SIRT,TVM and DART reconstruction algorithm,which established a foundation to reconstruct the temperature field quickly and exactly.(4)Research on instrument and experimentThe calibration of the multispectral thermometry system is the key problem to increase the whole system's accuracy in actual test process.The pyrometer wavelength function(PWF)of the multispectral thermometry system is tested in order to avoid the troublesome field calibration,and we get the normalized PWF that made it possible to realize the one-time calibration of the multispectral thermometry system.The system was used to measure the temperature at different heights on the axis of flame of the optical fiber taper machine,and the temperature field distribution at different height levels were reconstructed combining SIRT-TVM-DART join reconstruction algorithm through two orthogonal projection direction(front and side).Then a 1.5 t/h supercharged boiler under different working conditions were tested,and the temperature at the center of the observation hole was calculated.The experimental results were coincident with theoretical studies,which provided the application foundation of the measurement system of multispectral radiation thermometry.