ANALYSES OF ELECTRIC AND FLOW FIELDS IN CHARGE INJECTION TYPE OF ELECTROSTATIC OIL FILTER

Abstract

This paper presents experimental and numerical simulation results of the electric and flow fields in a charge injection type of electrostatic oil filter. A previous work has shown that flow is generated from the tips of the projections of the emitter electrode towards the smooth electrodes because of ion drag phenomenon and that the flow may detach part of the contaminant particles captured on the smooth electrodes and may be the principal cause of the saturation of the filtration speed at higher applied voltages and oil temperatures. In order to minimize the bad influence of the ion drag flow on the filter performance, it is important to be able to predict the flow in filters of various configurations by numerical simulation. Experimental results of the flow field are compared to numerical simulation results. In addition, electric potential distribution is measured and is compared between experiment and simulation. It is shown that the magnitude of the ion drag flow is increased with increasing applied voltage, is decreased with decreasing electrode spacing and is larger for negative charge injection than for positive charge injection. Similar results can be obtained by numerical simulations but the improvement of simulation accuracy is necessary.