Experimental study of premixed single edge-flame in a counterflow field

Abstract

A single premixed edge-flame established in a counterflow field of a combustible mixture and an inert nitrogen was experimentally investigated by using twin rectangular burners which were misaligned by a few degrees. The stretch-rate gradient was quantitatively defined as a function of the angle between the two burners and the distance from the edge of the burner. The flame weakly curved at the edge toward the stagnation plane and the shape of the flame edge did not depend on the composition of the mixture. The response of edge-flames to changes in flow conditions, such as the equivalence ratio of the mixture or the injection velocity at the burner exit, was basically determined by the Damkohler number of the mixture. The ratio of the local stretch rate at the flame edge and the extinction stretch rate for a single planar flame with the same composition was slightly smaller than unity, though the extinction stretch rate for the planar flame was about half of that for the twin planar flame due to large heat conduction to the opposing inert gas. This ratio of stretch rates for the single edge-flame was larger than that for twin edge-flames in a previous work, and this result agreed with the previous theoretical analysis by Buckmaster et al. and the previous experimental results of Ronney et al. Moreover, the effect of the stretch-rate gradient on the characteristics of the edge-flame did not appear for the single edge-flame.