Single-shot, Time-Resolved planar Laser-Induced Incandescence (TiRe-LII) for soot primary particle sizing in flames

Abstract

Two dimensional measurements of the size of soot primary particles, in both laminar and unsteady sooty C2H4/air flames, have been demonstrated in the present work. This is achieved using single-shot, time-resolved laser-induced incandescent (TiRe-LII) technique. The soot primary size is determined from the ratio of different signals obtained from four sequential images together with a theoretical relationship of the LII temporal decays. A laser fluence of 0.30J/cm2 was chosen for its relevance to application in turbulent sooty flames where both laser fluence attenuation and beam steering are significant. Planar measurements are firstly demonstrated in a flat laminar flame and the results are found to be in good agreement with time-resolved single-point-measurements using a photomultiplier tube. A typical uncertainty of ±9nm is estimated for the single-shot, planar measurements. Finally, planar measurements in an unsteady sooty flame reveal that the size of soot primary particles is very sensitive to local flame conditions.