Local Stretch Rates at Non-stationary Non-premixed Edge Flames

Abstract

An experimental study about effects of unsteadiness on extinction behavior of counterflow non-premixed edge flame was conducted. The counterflow non-premixed edge flame was established in the flow field with non-uniform stretch rate distribution between inclined counterflow slot-jet burners. Changes in the flow velocity, fuel volume ratio and fuel mass flux at the burner exit resulted in propagation of the edge flame. The propagation velocity of the flame edge was measured and the local stretch rate at the flame edge of the non-stationary edge flame was compared to that of the stationary edge flame. Experimental results showed the propagation velocity of the edge flame was in proportion to the rate of change in flow conditions. There was no difference between ignition mode in which the edge flame propagated toward a high stretch side and extinction mode in which the edge flame propagated toward a low stretch side. The local stretch rate at the flame edge of the non-stationary edge flame was the same as that of the stationary edge flame in all experimental conditions. It was noted that these results were obtained in the flow field with a relatively small rate of change in the flow condition.