Abstract

This work aims to advance understanding of the coupling between temperature and soot. The ability to image temperature using the two-line atomic fluorescence (TLAF) technique is demonstrated. Previous TLAF theory is extended from linear excitation into the nonlinear fluence regime. Nonlinear regime two-line atomic fluorescence (NTLAF) provides superior signal and reduces single-shot uncertainty from $250\mathrm{K}$ for conventional TLAF down to $100\mathrm{K}$. NTLAF is shown to resolve the temperature profile across the stoichiometric envelope for hydrogen, ethylene, and natural gas flames, with deviation from thermocouple measurements not exceeding $100\mathrm{K}$, and typically $\lesssim 30\mathrm{K}$. Measurements in flames containing soot demonstrate good capacity of NTLAF to exclude interferences that hamper most two-dimensional thermometry techniques.

© 2009 Optical Society of America

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