Opposed jet diffusion flames affected by velocity change were investigated to know why unsteady flames
survive at higher strain rates that are much larger than the steady extinction limit. Time-dependent maximum flame
temperature (Tmax) and OH radical (YOH) were measured over time using Rayleigh scattering method and OH laserinduced
fluorescence (LIF) respectively. In this experiment, unsteady extinction limits are much higher than the
steady extinction limits and values of the Tmax and YOH,max near the unsteady extinction limit were much lower than
those of the steady extinction. We found that both the unsteady response of the convective-diffusive zone and the
diffusive-reactive zone affect to the extension of the unsteady extinction limit.