A Diffusion Combustor and Methane-Air Flame Propagation in Concentration Gradient Fields

Abstract

An experimental apparatus for the study of the fundamentals of flame propagation phenomena in the gas mixtures with concentration gradient has been developed. The combustor provides one (or two) horizontal combustible layer(s) with severe concentration gradients formed only by interdiffusion of two (or three) initially homogeneous and isolated gases. The preliminary experiments were conducted for methane-air systems in case of a single combustible layer. A new schlieren photographic technique has been employed to make records of the flame propagation processes instead of the conventional cinephotographic technique, by which simultaneous measurements of the flame characteristics in space and time are possible. The results show that the flame propagating perpendicular to concentration gradient decelerates and may even lead to extinction for certain conditions. It is found that ignition energy, concentration gradient, and local equivalence ratio play an important role in such flame quenching phenomena.