Propagation and quenching of premixed flames in narrow channels

Abstract

The shape and propagation of unsteady premixed flames in narrow channels with adiabatic and isothermal walls are numerically investigated in the present study. The flame chemistry is modelled by an one-step overall reaction, which simulates the reaction of a stoichiometric acetylene-air mixture. The numerical results show that both ignition methods and thermal boundary conditions affect flame formation and its shape. The flame keeps a single tulip shape in the whole process of propagating through the channel if plane ignition is used and a single mushroom shape if spark ignition is used. For isothermal cold walls, the flame cannot keep a single tulip shape or mushroom shape all the time. Under plane ignition, a transition from a tulipshaped flame to a mushroom-shaped flame occurs as flames propagate from one end of channel to the other. Under spark ignition, the process is just the contrary. It is also shown that the heat loss at the cold walls has a dual effect on the formation of a tulip-shaped flame. Flame propagation and quenching in narrow channels of different heights are analyzed systematically, and a criterion is proposed to judge the flame states of partial extinction and total extinction. It is called the criterion of flame propagation and quenching in narrow channels.

An experimental study of methane–oxygen–carbon dioxide premixed flame dynamics in non-adiabatic cylinderical meso-scale reactors with the backward facing step

“…He showed that flame shape in meso-scale reactors can be asymmetric due to the effect of free convection on the flame surface. The numerical study of the shape and propagation of unsteady premixed flames in small channels under adiabatic and isothermal wall conditions was conducted by Song et al [14]. They maintained that both the ignition methods and the thermal boundary conditions have great influence on flame shape in small scale channels.…”

Investigation on quenching characteristics of parallel narrow channels for deflagration flames

“…Jafargholi et al 18 found that the flame was frontally quenched on the horizontal wall, then propagated to the sidewall affected by the sidewall quenching, and finally triggered thermal diffusion instability along the front. Song et al 19,20 systematically analyzed the flame propagation and quenching in parallel narrow channels of different heights, and proposed criteria for judging the state of partially extinguished and completely extinguished flames. Wang et al 21 used twodimensional numerical simulation to study the effects of hydrogenation, inlet temperature, wall thermal conductivity, and wall thickness on the coupling of propane/air flame and wall.…”