Finite element analysis of positive and negative discharge in atmospheric air

Positive and negative discharge mechanisms in atmospheric air have been numerically analyzed using a fully coupled finite element analysis. Until now, many research works have examined discharge analyses, but the discharge mechanism has not yet been explained in detail numerically. In a positive discharge, the electric field intensity at the streamer head can be enhanced owing to the superposition of a Laplacian field and a field from the positive space charge density. With this increased electric field intensity and attraction force between the negative electrode and positive space charge density, the positive streamer can move straight from the positive tip electrode to the negative plane electrode. In a negative discharge, the polarity of the electrode is reversed, and the positive space charge covers the negative electrode. Excess negative ions move toward the positive electrode, and a Trichel pulse is formed in the discharge current. To analyze this space charge propagation, we employed charge continuity equations for carriers such as electrons and positive and negative ions. These equations include ionization, attachment, and recombination effects, and Poisson's equation for electric fields. A secondary emission effect is included as a boundary condition on the cathode surface. Tip-plane electrodes were implemented in 2D axial symmetric model with a gap radius of 1 mm. To verify our numerical setup, the numerical results were compared with experimental data found in the previous literature.