Deduction of the two-dimensional distribution of temperature in a cross section of a boiler furnace from images of flame radiation

This paper presents a novel instrumentation system for deducing the two-dimensional (2-D) distribution of temperature across a cross section of a furnace fired with pulverized coal. The system consisted of four flame image detectors, a frame-maker, and a microcomputer with a frame-grabber. Four colored images were captured by the four detectors, which were mounted in the four corners of a tangentially fired furnace. A radiation model was established to relate the flame images with the 2-D temperature distribution. A revised Tikhonov regularization method was used to reconstruct the 2-D temperature distribution from the flame radiation images. The experiment was done in a 1025 t/h boiler furnace of a 300-MW power generation unit. The 2-D temperature distribution in 100 discrete meshes in the cross section above the burner zone was deduced continuously using this instrumentation. The experimental results show that the 2-D temperature distribution appears typically to have single-peak shape with temperatures higher in the center and lower near the wall. Results obtained over a range of combustion conditions demonstrated that the average temperature of the cross section changed in direct proportion to the load of the furnace. The updating time for the visualization is less than 2 s, and the method is practically suitable for the on-line monitoring of combustion in a furnace.