Three-dimensional reconstruction for flame chemiluminescence field using a calibration enhanced non-negative algebraic reconstruction technique

The three-dimensional optical diagnostic method has received extensive attention from researchers because of its ability to provide three-dimensional physical information for reactive flow studies such as combustion. Computed tomography of chemiluminescence (CTC) has become a commonly used technique for three-dimensional, transient flame reconstruction purposes. However, due to view number limitations and considerable computational costs, the spatial resolution achieved and accuracy of the reconstruction are less satisfactory compared with applications such as in the medical fields. This investigation focuses on a few methods for improving the experimental and numerical performance of the CTC methods. Firstly, a cylindrical ChArUco calibration target was introduced and a multi-camera calibration method considering the position constraints of cameras was proposed to eliminate the registration error due to the rotation of the calibration target. Furthermore, a sub-voxel method was adopted to improve the spatial resolution of flame reconstructions. Finally, a non-negative algebraic reconstruction technique (NNART) was developed. The algorithm was verified with a simulated jet flame and then was tested against a diffusion jet flame and a swirl flame experimentally.