Characterization of electrode charges and forces in an electrohydrodynamic thruster

Corona discharge generates an electrohydrodynamic (EHD) flow and a reactive thrust between electrodes in the air. Although the theory for this thrust between two electrodes has been thoroughly developed, the mechanism responsible for the reactive forces acting on the electrode surfaces is not well understood. Here, we numerically and experimentally investigate these forces and the charges that generate them. The results show that the emitter and collector surface charges deviate from the equality of capacitive charges as the discharge initiates. As the applied voltage increases, the emitter surface charge maintains its initial onset value, while the collector surface charge and the volume charge between the electrodes linearly increase. In the same manner, the emitter and collector surface forces deviate from the equilibrium of action and reaction as the discharge initiates. As the circuit current increases, the emitter surface force maintains its initial onset value, while the collector surface force and the thrust linearly increase. In particular, we demonstrate an unconventional thrust-measuring method by installing a windshield in the rear of the thruster. The force exerted on the windshield is equal to a good approximation of the pure EHD thrust. Also, the difference between this force and the thrust measured without the windshield can be taken as the approximate drag force acting on the electrodes.