Recovery of Temperature and Species Concentration Profiles in Flames Using Low-Resolution Infrared Spectroscopy

Abstract

The temperature and species distributions in semi-transparent gaseous axisymmetric objects are retrieved by carrying out the inversion of their directional low-resolution spectral transmission and/or spectral emission in the infrared by using methods based on the solution of the radiative transfer equation. The validity domains of the hypothesis on which the low resolution inversion methods are based are discussed by comparison with the corresponding exact radiative properties generated by line-by-line descriptions. A propane-air laminar premixed flame is experimentally studied. The infrared data are collected for the (ν3) band of CO2, either by a directional scanning (at a fixed frequency) or by a frequency scanning (in a fixed direction). Depending on the data acquisition methods, two different reconstruction techniques are used. For spatial scanning, a generalized Abel transformation or the regularized Murio’s method, is utilized. For spectral scanning the recovered results are carried out by the Chahine-Smith method. For both techniques, profile reconstructions are worked out accounting for a spectral data bank based on the narrow statistical band model. Finally, thermal and CO2 concentration mappings of the premixed flame are presented.