In situ measurement of cross-section temperature field of pulverized coal boiler based on solving radiative transfer equation using a single image sensor

This study introduces flame image processing techniques to extract both the temperature and radiation parameters in the furnace. Additionally, a two-dimensional rectangular furnace system is established with emitting and reflecting walls and emitting and scattering spatial media. The radiation imaging model, developed through the distributions of ratios of energy scattered or reflected method, establishes a quantitative functional relationship between monochromatic radiation intensity images of the flame at two wavelengths and internal furnace temperature and radiation parameters. The Tikhonov regularization algorithm is used to reconstruct the radiation source terms within the furnace. An optimization algorithm is used to reconstruct the temperature and radiation parameters within the furnace, assuming uniform absorption and scattering coefficients. Despite the non-uniform distribution of internal radiation parameters, reconstructing the furnace temperature distribution using uniform radiation parameters remains feasible. The maximum relative error in temperature reconstruction is 2.28 %, which meets industrial temperature measurement requirements. Moreover, experimental studies are conducted on a coal-fired boiler to simultaneously detect both furnace cross-sectional temperature and radiation parameters. A single detector is used to obtain data sequentially from eight observation ports. During this process, flame images are captured under stable boiler operating conditions. These data are used to reconstruct the cross-sectional temperature distribution and radiation parameters in the burnout air zone of the boiler under different load conditions. Experimental results indicate that as the boiler load increases from 147 to 159 MW, the furnace temperature, absorption coefficient, and scattering coefficient all increase. Notably, the flame imaging processing method serves as a reliable method for monitoring the cross-sectional temperature field and radiation parameters in the large coal-fired boilers and is crucial for obtaining the data required for numerical simulations of combustion in large furnaces.