Three-dimensional reconstruction of flame temperature and emissivity through tomographic imaging and pyrometric measurement

This paper presents the reconstruction of 3-D (three-dimensional) flame temperature and emissivity distributions using tomographic imaging and pyrometric techniques. An imaging system comprising eight optical imaging fiber bundles and two RGB CCD (Charged-couple Device) cameras is used to acquire flame images simultaneously from eight different directions. A combined LFBP (Logical Filtered Back-Projection) and SART (Simultaneous Iterative Reconstruction and Algebraic Reconstruction Technique) algorithm is applied to the 3-D reconstruction of gray-level intensity for the two primary color (red and green) images. The temperature distribution of the flame is determined from the ratios of the reconstructed gray-levels intensity and then the emissivity is estimated from the ratio of the gray-level of a primary color of the images to that of a blackbody source at the same temperature. The system calibration was conducted on a blackbody furnace. Experimental results on a gas fired combustion test rig demonstrate that the proposed technical approach performs well in the measurement of the 3-D temperature and emissivity distributions of the flame.