Effects of electric fields on stabilized lifted propane flames

The effects that various charged electrodes, and associated electric fields, have on lifted propane flames have been investigated. Two electrodes were used to provide an electric field with potentials ranging from 0 to 11,000 V. The primary electrode was around the flame and the secondary electrode was the fuel nozzle. Electrode polarity and primary electrode location with various flame field locations (near, mid, far) were varied, resulting in a variety of flame behavior. Results show that the body force resultant from the bulk flow of formed ions, from a positively charged fuel nozzle, and grounded ring electrode, will increase flame liftoff height and, eventually, cause blowout. However, for the opposite polarity (positively charged ring electrode and grounded fuel nozzle), the flame progresses toward reattachment with increasing potentials. Observing the narrow window of flame blowout or reattachment (varying with polarity), it was observed that the lifted flame height fluctuations were increased with the presence of the grounded ring electrode, but reduced when the polarity was shifted to positive configuration (positively charged primary electrode). Flame hysteresis was observed when the ring electrode was positively charged and it was found that the hysteresis regime increased when the potential of the ring electrode was increased to 1500 V but had little changes at lower potentials. While the ring electrode was positively charged, a distinct hole was observed in the center of the flame. Several images are presented that show these flame holes that are present when the electrodes are charged. Copyright © 2014 by ASME.