DYNAMIC STABILIZATION ZONE STRUCTURE OF JET DIFFUSION FLAMES FROM LIFTOFF TO BLOWOUT

Structures of methane and propane jet diffusion flames under liftoff to blowout conditions are studied. The focus of this investigation is on the dynamic, time-varying features of flame propagation and stabilization near the flame base. The turbulent velocity and length scales of the name motion were directly measured using the thin-filament pyrometry (TFP) technique at high sampling rates. A significant change in the turbulent velocity and length scales of the measured flame was observed as the jet velocity increased, approaching the blowout condition. The deduced turbulent diffusivity displayed over one order of magnitude increase from liftoff to blowout. The strain rate, however, never exceeded approximately 600 1/s. Near blowout, the flame base became very broad.