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

The effects, which an electric held exerts on flames, have been observed an d reported in the literature for a long time. Burning velocity, dame stabil ity flame shape, flame luminosity, extinction limit, and soot formation, ar e among the effects that have been observed. Most of the studies in this fi eld 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 o ur ability to use electric field as a means to control the combustion proce ss, are restricted, In the present work, co-flowing diffusion methane/air f lames and candle-type methane/air flames under the electric field effect ha ve been observed experimentally. A numerical model, which considers the mor e important physical and chemical phenomena associated with the flame-field interaction process, has been developed to explain the experimental observ ations. The model employs a two-dimensional cylindrical coordinate system a nd assumes axial symmetry. A simplified chemical reaction scheme for a meth ane-air mixture, which contains 19 chemical species and 31 reactions is emp loyed. It combines existing methane oxidation mechanisms with a series of c hemiionization, ion-molecule, and dissociative-recombination reactions, whi ch are important for the ionic species. The mass, momentum, species and ene rgy conservation equations are solved numerically by an integrated version of the PHOENICS and CHEMKIN;IN computer codes. It is concluded that the eff ects of an electric field on the flame behavior are mainly due to ionic win d effects. (C) 2000 Elsevier Science Inc. All rights reserved.