Quantitative NO-LIF imaging in high-pressure flames
Planar laser-induced fluorescence (PLIF) images of NO concentration are reported in premixed laminar flames from 1-60 bar exciting the A - X(0, 0) band. The influence of O2 interference and gas compostition, the variation with local temperature, and the effect of laser and signal attenuation by UV light absorption are studied. Despite choosing a NO excitation and detection scheme with min. O2-LIF contribution, this interference produces errors of up to 25% in a slightly lean 60 bar flame. The overall dependence of the inferred NO number density with temperature in the relevant (1200-2500 K) range is low (< +-15%) because different effects cancel. The attenuation of laser and signal light by combustion products CO2 and H2O is frequently neglected, yet such absorption yields errors of up to 40% in the expt. despite the small scale (8 mm flame diam.). Understanding the dynamic range for each of these corrections provides guidance to minimize errors in single shot imaging experiments at high pressure.
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