Evaluation of nonlinear regime two-line atomic fluorescence (NTLAF) in sooty flames

Abstract

Nonlinear excitation regime two-line atomic fluorescence (NTLAF) is a laser-based thermometry technique that enables temperature measurements in sooty conditions. However, the NTLAF technique might be affected by soot interferences and fluorescence, when the soot level within the flame is high. To examine this effect, both on- and offwavelength measurements are presented and compared in this paper. The measurements indicate that the spurious scattering and laser-induced incandescence from soot are not significant for the present flame of interest. The measurements also suggest that the fluorescence from the condensed species (CS) could be responsible for the observed off-wavelength signal. The usage of an additional camera with an optical filter, centred at an off-resonance wavelength, to account for the extraneous signal is demonstrated to be feasible.