Dynamic and stationary charging of heavy metallic and dielectric particles against a conducting wall in the presence of a dc applied electric field

摘要

Dielectric and metallic paricles (both spherical and irregular in shape) in the range 29-4760 μm in diameter are electrically charged while in dynamic or stationary contact with either wall of a charged parallel‐plate capacitor. The charge distribution received tends to remove any particle from the wall. Particles larger than 127 μm are studied individually with dc electric field strengths of 2-15 kV/cm. Smaller particles are studied mainly in the form of clouds. In the presence of gravity and standard atmosphereic air, the particle motion, once initiated, is continuous between the parallel plates both dynamic and stationary charging and the resulting particle motion are experimentally and theoretically studied considering the particles as capacitors in themselves. For copper particles a single formula of the form Q= (πϵ) a2EK applies 2EK applies with K=1.64 whether or not charging is dynamically or statically acquired. The presence of an oxide film does not alter K. Dielectric particles followed a similar equation (K≪1.64) when contact (triboelectric) charging was assumed small and surface electrical conductivity was sufficiently large. K for dielectrics is dependent on surface conductivity, permittivity, diameter, and contact time. Induced average particle velocities in atmospheric air were tested from 40 to 105 cm/s. Inelastic particle‐wall collisions and a conservative body force such as gravity resulted in a critical lower limit electric field strength for sustained particle motion. Gaseous discharge from a particle to a wall of opposite sign can occur with sufficient particle size and electric field strength.