Counterflow diffusion flames

Laminar counterflow diffusion flames are generally referred to as the pure diffusion flame. This paper reviews experimental studies of these counterflow diffusion flames and presents a detailed summary of our present understanding of them. The paper begins by classifying these laminar counterflow diffusion flames into four types: (I) the counterflow diffusion flame between two opposed jets, (II) the flat, counterflow diffusion flame between two opposed matrix burners, (III) the counterflow diffusion flame in the forward stagnation region of a spherical or hemispherical porous burner, and (IV) the counterflow diffusion flame in the forward stagnation region of a cylindrical porous burner. Next, the characteristics of these counterflow diffusion flames are presented, and these flames are then shown as being suitable for a fundamental study of diffusion flame and its combustion characteristics, especially, (1) for a detailed study of the structure of a laminar diffusion flame and of high-temperature flame kinetics, (2) for an accurate study of combustion characteristics closely related to flame-extinction phenomena (e.g. dilution limits of diffusion flames, the overall reaction rates for fuel-oxidant combinations, and the effectiveness of inhibitors), and (3) for a careful study of the various properties of a flame in an electric field.