Role of EHD Motion in the Electrical Conduction of Liquids in a Blade-Plane Geometry

A blade-plane electrode assembly is used to study electrical conduction in divergent fields and, more generally, to investigate high field conduction of dielectric liquids. The stationary current-voltage characteristics show two regimes of conduction: a quasi-ohmic regime and a V¿ one, V being the applied voltage and 3 < ¿ < 6. The latter regime corresponds to dominance of charge injection by the blade, as revealed by the field distribution obtained by the Kerr technique. A liquid motion is induced by the Coulomb force which convects charge carriers and results in a decrease of the first transit time following the application of a voltage step. The transient injection currents exhibit a dependence upon the elapsed time during which no voltage is applied, and the possible origin of this phenomenon is discussed. Measurement of the liquid velocity by laser Doppler anemometry also exhibits two different laws of variation with applied voltage consistent with the two current regimes. In the steady-state conditions of the injection-dominant regime, the square of the measured velocity component w2 varies as the electrical power input IV(I being the current). This is tentatively interpreted by the viscous dominated character of the induced motion.