Dynamic behaviours of a flame as plasma in a strong electric field

Dynamic behaviours of a flame are experimentally examined via applying an electric potential difference between two parallel electrodes and placing a flame of ethanol between them. Given that a flame behaves as a weakly ionised plasma, the shape of the flame is affected by an external strong electric field. When a strong ac electric field is applied horizontally, i.e., transverse field, and as the applied ac voltage increases, the shape of the flame becomes flat and the width of the inner flame expands and saturates at a specific value. When a strong ac electric field is applied vertically, i.e., axial field, the frequency of the self-excited oscillation is affected by a specific value of the applied frequency. When the frequency of the applied ac voltage changes, temperature and light emission of flame are significantly affected by the applied ac voltage. Furthermore, when the strength of the horizontally applied electric field is further increased, a discharge occurs in the flame, and it is reshaped into an arc plasma. The current signals exhibit background troughs and sudden peaks in the form of spikes. The spectrophotometric curve includes the spectra of both the flames and arc plasma under the arc discharge.