Mid‐infrared multiline absorption tomography for in situ analysis of thermochemical structure in natural gas‐fired cooker flame

Abstract A mid‐infrared laser absorption tomography technique was developed to quantify the nonuniform thermochemical structures of flames stabilized on a natural gas‐fired cooker. Multispectral absorption spectroscopy coupled with Tikhonov‐regularized three‐point Abel inversion was used to resolve the spatially resolved temperature and species concentration. A tunable interband cascade laser (ICL) near 4.2 μm was used to access multiple CO 2 absorption lines in the fundamental vibration band. Multiline Voigt fitting strategy was used to improve the fitting of the overlap absorption features. Comprehensive measurements at a different height above the cooker were performed and assembled to display the contour of temperature and CO 2 concentrations, resolving the nonuniform thermochemical structure of the high‐temperature combustion field. The measurement uncertainty analysis for temperature and CO 2 concentration was also discussed. The current technique is demonstrated to be capable of quantitatively distinguishing flame conditions under different fuel supply modes.