Soot and nanoparticle concentrations in a turbulent non-premixed ethylene/air flame from laser induced emission measurements at 213nm

Fluorescence (LIF) and incandescence (LII) measurements induced by the fifth harmonics of a pulsed Nd-YAG laser at 213nm have been used for the determination of the volume fractions of particulate in a turbulent non-premixed flame of ethylene. The use of a low wavelength light source allows to the detection of fluorescent nano-sized particles, which have a large absorption band between 200 and 250nm. The high energy light source selected enhances the fluorescence of NOC particles, which exhibit a large absorption band between 200 and 250nm, and also allows soot particles heating-up and incandescence emission. Laser induced scattering measurements have been performed on the same flame in order to estimate the mean sizes of both the fluorescent particles and soot. Nano-sized particles are formed in the inner part of the flame immediately downstream of the burner outlet. Their concentrations level increases along the flame axis and decreases in correspondence of the massive formation of the soot. Typical sizes of the particles is of the order of 3nm whereas soot particles are of about 20nm.