ELECTROKINETIC STUDY IN NONPOLAR LIQUIDS BY LASER-DOPPLER ANEMOMETRY

The influence of EHD motion on charge convection in stressed contamina ted non-polar liquids has been investigated. The test liquids, Norpar( R) 12 and Voltesso (R) 35 were artificially contaminated by adding a c ertain quantity of fine carbon black particles or Stadis(R) 450, an io nic impurity. The role played by the charge convection in the passage of current was analyzed by studying the transient current resulting fr om the application of a step voltage to parallel-plane electrodes sepa rated by the test liquid. Non-intrusive optical techniques, Schlieren photography and laser Doppler anemometry were used for flow visualizat ion and measurement of velocities both during the transient and steady state condition. The variation in velocity with time followed the sam e trend as the current. Both velocity and current measurements indicat e that the peak value of velocity/current during transient state depen ded on the initial charge density at the liquid-electrode interface. A ny increment in current was closely associated with increased liquid v elocity indicating that charge transport was dominated by convection. The large difference between maximum velocities during transient state and mean velocities during steady state indicated that injection in n on-polar liquids is weak and is a function of the impurity concentrati on.