Flame Propagation in Stratified Methane-Air Mixtures

Abstract

This paper describes the results of an experimental investigation aimed at establishing the nature of flame propagation within stratified mixtures of methane and air in circular tubes. Flames propagating upwards, horizontally, and downwards through concentration gradients of up to 3 percent by volume of methane per meter were studied. The velocities of decelerated flames were observed to be up to 70% higher than the corresponding flame velocities under homogeneous mixture conditions. Empirical correlations were then developed for flame velocities within stratified mixtures in terms of corresponding velocities under homogeneous conditions, concentration gradients, and homogeneous flame velocities corresponding to mixture concentrations at the ignition point.