Outwardly propagating spherical flames with non-uniform AC electric fields in atmospheric pressure

The effects of AC electric fields on outwardly propagating premixed flames are investigated experimentally. The principle burning characteristics of a laminar premixed flame, comprising the flame speed, the laminar burning velocity, the mass burning rate, the stretch rate and Markstein numbers, are reported and discussed for methane and propane-air mixtures. Electric fields are generated by using a point source electric plug subjected to a wide range of high electrical potentials up to 9 kV at fixed frequency of 1 kHz. Simultaneous high speed schlieren imaging and combustion pressure measurement have been implemented. Local flame speeds at four different directions were measured after applying bidirectional electric potentials (ac) and compared with the conventional case (i.e.0 kV). The flame morphology develops an observable cracked structure appreciably under the influence of electric fields enhancing the burning rate of the combustible mixtures. Such enhancement was manifested in the advancement of pressure rise as the applied electric potential increases. The present findings proposed physical and chemical mechanisms to interpret the electric influence in enhancing the flame speed and destabilizing the flame front.