2D 2-Colour time-Resolved laser induced incandescence sizing of ultra-fine soot particles in a methane diffusion flame

Planar, two-dimensional, two-colour, time-resolved laser-induced incandescence (2D-2C-TiRe-LII) is employed to investigate the formation of soot in a standard methane laminar diffusion flame for the first time. The work builds on previous developments in 2D LII by time-resolving the signal decay by shifting the gating time of ICCD cameras. The two-colour configuration allows application of the technique to extract the initial temperature of soot particles immediately after the laser pulse, instead of relying on estimates of the soot absorption coefficient, thus allowing higher accuracy in the determination of very small particle sizes produced in methane flames, using a minimum error approach. The technique is combined with a previous work on Continuous Wave Laser Cavity Extinction (CW-LCE) to allow absolute measurements of sub-ppm low soot volume fractions with very small particle sizes.