Reconstruction and analysis of non-premixed turbulent swirl flames based on kHz-rate multi-angular endoscopic volumetric tomography

Abstract

The development of laser and sensor technologies have provided unprecedented opportunities for the extended applications of volumetric tomography. The recent progresses in computed tomography of chemiluminescence (CTC) have facilitated the understanding of turbulent flows and combustion instability. However, the current demonstrations of CTC can only provide either an instantaneous measurement with a good number of projections to achieve a good spatial resolution or time-resolved measurements (kHz-rate) but with a reduced number of projections which may cause a failure in resolving small details of the flames. In this work, we aim to develop a time-resolved endoscopic CTC system with 17 projections to achieve both good spatial and temporal resolutions. A new method was proposed here to calibrate projections that cover a field of view larger than 180 degrees. The system was then applied to a non-premixed turbulent swirl flame to reconstruct its time-resolved 3D structures. The experimental studies have shown that when only nine projections were used, parts of the flame structures would be lost. To fully recover the flame structures, a minimum of 16 projections should be used. Proper orthogonal decomposition and dynamical mode decomposition were then applied to analyze the time serious of 3D structures of a turbulent swirl flame.