Premixed flame propagating into a narrow channel at a high speed, part 1: Flame behaviors in the channel

This paper deals with the transient behavior of a flame flowing into a narrow channel from a chamber filled with a propaneair mixture. The flame was observed through direct or schlieren high speed photography, and at the same time the arrival at the entrance and exit of the channel were detected by ion gaps. From the experimental results it was found that in some cases the flame extinguished or hesitated in the channel before passing through. These behaviors were dependent on the equivalence ratio of the mixture, the channel width, and the flame inflow velocity. Flame standstill in the channel is assumed to be caused by continuous quenching of hot reacting gas due to turbulent mixing with cold unburned gas at the contraction region established near the entrance of the channel. For any specific mixture, when the channel entrance is rounded or the inflow velocity is low, the minimum width of the channel for which a flame will run through without any retardation becomes smaller compared with the case of a sharp-edged entrance or a high inflow velocity. On the contrary, the minimum width of the channel for which a flame cannot pass through does not depend on the corner roundness of the channel entrance or the inflow gas velocity.