Effect of Electrode Distance on Combustion Behavior of Fuel Droplet in Vertical DC Electric Field

Flames are affected by external electric fields because they contain ions and electrons. The movement of ions and electrons affects the external electric field owing to their charge. In this context, this paper discusses the change in the electric field on the basis of experimental results obtained at different electrode distances. Employing one-dimensional (1D) steady-state analysis, we assume that if the electric field is changed spatially, the effect of the electric field on combustion behavior is aligned with V2/L3, where V is the applied voltage between the electrodes and L is the distance between the electrodes. Because a flame deforms to a cathode owing to electric body force in an electric field, the change in the flame shape of burning ethanol droplets observed in a vertical DC electric field and the electric current during combustion are measured as flame characteristics. The results reveal that applied electric voltage exists where the flame becomes vertically symmetrical to balance the buoyancy due to the electric body force. The relationship between m and n of Vm/Ln for flame symmetry is around n/m = 1.5. On the basis of these results, all experimental results for different electrode distances are rearranged with eV2/L3, which is a representative electric body force, and it is proved that the use of parameter eV2/L is effective. These results indicate that the change in the electric field due to the existence of a flame should be considered when examining the effect of an external electric field on combustion behavior.