Breakdown characteristics of nonuniform electric fields in crossflows

An experimental evaluation of the breakdown characteristics of the nonuniform electric fields established between two spheres and between two points in a crossflow was conducted and the results were then compared to the breakdown characteristics in quiescent air. The aluminum spheres used in this investigation ranged in diameter from 0.635 em to 2.54 em. The points had a radius of curvature of 0.5 mm. The velocities of the crossflow ranged from 23 mls to 58 mls and the gap distances ranged from 0.5 cm to 2.0 cm. Photography was used to determine the effect of the crossflow on the luminous spark for all electrodes. The sparking voltages in the crossflow were a function of the crossflow velocity, electrode size and gap distance. It was concluded that the most significant increase of sparking voltages in a crossflow, as compared to the same configuration in quiescent air, was for the point-point gap at a distance of 2.0 cm for a 58 mls crossflow. As the electrodes were increased in size, the effect of a given crossflow decreased. For the 2.54 cm spheres with a 58 mls crossflow, there was actually a decrease in the sparking voltage as compared to its counterpart in quiescent air. The photographs showed a significant deflection of the spark in the direction of the crossflow for the point-point gap, but no significant deflection was detected for the other electrode geometries.