Transfer functions of laminar premixed flames subjected to forcing by acoustic waves, AC electric fields, and non-thermal plasma discharges

The responses of laminar CH₄-air flames to forcing by acoustic waves AC electric fields and nanosecond repetitively pulsed glow discharges were investigated. Conical M-shaped and V-shaped flames were considered. For forcing by acoustic waves and plasma the geometry of the flame plays a major role in the response of the combustion while the flame shape did not affect the response of the combustion to electric field forcing. The flame response to acoustic forcing of about 10% of the incoming flow was similar to those previously obtained. The flames were responsive to an AC electric field across the whole range of frequencies. The gain of the transfer function obtained for plasma forcing was up to 5 times higher than for acoustic forcing. A forcing mechanism based on the generation of ionic wind is proposed along with a possible mechanism of plasma forcing.