Flame growth and wrinkling in a turbulent flow

High-speed planar laser-induced fluorescence (PLIF) and 3-D large eddy simu lations (LES) are used to study turbulent flame kernel growth, wrinkling an d the formation of separated flame pockets in methane/air mixtures. Turbule nce was effected by a set of rotary fans situated in a cylindrical enclosur e. Flame wrinkling was followed on sequential 2-D OH images captured at kHz repetition rates. Under stoichiometric conditions and low turbulence level s the flame kernel remains singly connected and close to spherical in shape . By increasing turbulence or reducing the stoichiometry of the mixture the formation of separated pockets could be observed and studied. The mechanis ms behind these phenomena are investigated qualitatively by LES of a level- set G-equation describing the flame surface propagation in turbulent flows.