The effect of an electric field on the shape of co-flowing and candle-type methane-air flames

The effects, which an electric field exerts on flames, have been observed and reported in the literature for a long time. Burning velocity, flame stability, flame shape, flame luminosity, extinction limit, and soot formation, are among the effects that have been observed. Most of the studies in this field were experimental observations. There is fairly limited information in the literature on numerical studies in the area of electric field and flame interaction. Therefore, our fundamental understanding of the process and our ability to use electric field as a means to control the combustion process, are restricted. In the present work, co-flowing diffusion methane/air flames and candle-type methane/air flames under the electric field effect have been observed experimentally. A numerical model, which considers the more important physical and chemical phenomena associated with the flame-field interaction process, has been developed to explain the experimental observations. The model employs a two-dimensional cylindrical coordinate system and assumes axial symmetry. A simplified chemical reaction scheme for a methane-air mixture, which contains 19 chemical species and 31 reactions is employed. It combines existing methane oxidation mechanisms with a series of chemiionization, ion-molecule, and dissociative-recombination reactions, which are important for the ionic species. The mass, momentum, species and energy conservation equations are solved numerically by an integrated version of the PHOENICS and CHEMKIN computer codes. It is concluded that the effects of an electric field on the flame behavior are mainly due to ionic wind effects.