Visualization study of electrohydradynamic flow field in electrostatic separator

The electrohydradynamic (EHD) flow characteristics of micron size(2 μm) oil droplets in a wire-plate electrostatic separator were investigated by particle image velocimetry(PIV) method. The typical flow patterns and velocity distribution under fully developed laminar flow (gas flow velocity of 0.16 m/s) were presented with the applied voltage changed. The results show that the EHD flow patterns and velocity distribution were significantly influenced by the applied voltage. When the applied voltage is below the onset corona discharge voltage(<8 kV), the flow field does not change significantly. With the increase of applied voltage (8-12 kV), oil droplets at the discharge electrode and the downstream of the separator move towards to the two collecting plates in the form of jet. The transverse velocity and axial velocity at upstream increase as the applied voltage increases. When the voltage is above 12 kV, the EHD secondary flow at upstream of discharge electrode appears in the form of two symmetric counter rotating vortices. The sizes of vortices increase with the voltage increasing. The maximum transverse velocity can reach up to 0.4 m/s. Meanwhile, the EHD reverse flow appears at the downstream of the separator. The appearance of EHD secondary and reverse flow blocks the flow along axial direction. The separation efficiency increases with the increase of the applied voltage.