Laser-induced incandescence measurements in turbulent ethylene diffusion flames

Instantaneous, spatially-resolved measurements of soot within turbulent diffusion flames is necessary for model development and testing. Laser-induced incandescence was used to carry out quantified soot volume fraction measurements within turbulent ethylene-air diffusion flames. Flow velocity dramatically increased with increasing O₂ ambient concentration. The spatial extent of soot containing regions also increased with increased volume fraction, causing a decrease in the soot intermittency. The soot containing region experienced both an increase and contraction. The proximity of the reaction front to the shear layer induced turbulent mixing had a dramatic effect on soot loading, fluctuation, and spatial distribution. Increasing the stoichiometric mixture fraction by increasing the O₂ ambient concentration resulted in the laminarization of the potential core. However, the locally higher concentrations of hot combustion products accelerated soot inception and growth and offset the reduced shear layer mixing, increasing the volume fraction. The radial variation in the volume fraction indicated intermittent and random turbulent mixing as measured by soot inception and growth.