Pulsating mode of flame propagation in two-dimensional channels

Flame propagation in channels and cracks is a problem of considerable interest with applications in many practical combustion devices, in fire hazard scenarios, and in the emerging micropropulsion technologies. Understanding the dynamics and stability characteristics of flame propagation in channels is, therefore, important both for fundamental research as well as for practical applications. In this work, we examine the propagation of a premixed flame front in a two-dimensional channel in the presence of a Poiseuille flow. Our primary objective is to determine within the flammable regions the structure of the flame front and the conditions that result in steady propagation and those leading to a pulsating mode of propagation. Special attention is given to the difference between propagation in narrow and wide channels, heat losses to the channel's walls, and an imposed flow that either supports or opposes the propagation. In general, flame oscillations are found to occur in mixtures for which the effective Lewis number is sufficiently large. They are more likely to occur in narrow or wide channels and particularly at near-extinction conditions where the critical Lewis number is reduced to physically accessible values.