An Experimental Study on the Unsteady Extinction Limit Extension of a Counter-flow Diffusion Flame Affected by Velocity Change

Abstract

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.