Visualization of three-dimensional temperature distributions a large-scalefurnace via regularized reconstruction from radiative energy images: numerical studies

In this paper, the possibility of visualization of three-dimensional (3-D) temperature distributions in large-scale boiler furnaces from radiative ene rgy images captured by multiple charge-coupled device (CCD) cameras mounted around the furnace is studied numerically. For the calculation of the radi ative energy image formation, a fast algorithm proposed by the authors for pinhole imaging is used in this paper, which is based on the Monte Carlo me thod and combined with a concept of angular factor effective for image form ation. This algorithm is applicable for the emitting, absorbing, and isotro pic scattering medium. For the inversion of the 3-D temperature distributio ns which is an ill-posed problem, a modified Tikhonov regularization method is improved, where the finite difference regularizer is defined and can be used in 3-D cases, and the optimal regularization parameter is suggested t o be selected by using a post-treatment method. For a 3-D unimodal temperat ure distribution, the numerical simulation results show that the reconstruc tion errors for the 3-D temperature distribution can be maintained at level s similar to the measurement error and the visualization quality of the tem perature distribution is satisfactory. For a kind of bimodal temperature di stribution, the reconstruction errors are higher than those for the unimoda l distribution, but the bimodal feature of the temperature distribution can also be reproduced clearly. (C) 2001 Elsevier Science Ltd. All rights rese rved.