4D imaging of turbulent flames with improved multi-camera calibration method and processing speed

4D imaging measurements in turbulent flames have been long desired to better understand the complex phenomena involved in the combustion process. Such 4D measurements provide the information of turbulent flames in all three spatial coordinates and time sequences. Tomographic reconstruction has been recently demonstrated as a promising approach for 4D flame diagnostics. However, two critical issues remain in the current 4D tomographic measurements: the accuracy of multi-camera calibration and the processing time of the tomographic program. Therefore, this work aims to address the two issues by developing a new multi-camera calibration method and a parallel tomographic reconstruction program. As shown in this work, the new multi-camera calibration method can significantly improve the angle calibration accuracy; and the parallel program reduces the processing time for 1000 tomographic reconstructions from 10 days to similar to 12 h. Such enhanced accuracy and processing speed are expected to benefit a range of combustion researches, and a specific example is demonstrated involving 4D imaging of a subsonic diffusion flame.