EHD Flow and Collection Efficiency of a DBD ESP in Wire-to-Plane and Plane-to-Plane Configurations

In this paper, particle velocity fields inside three electrostatic precipitators (ESPs) are investigated experimentally using particle image velocimetry (PIV). The reference case is a typical wire-to-plane ESP under negative and positive dc high voltages. The two other ESPs use an ac high voltage to generate a dielectric barrier discharge (DBD) in wire-to-plane and plane-to-plane configurations. The main objective of this paper is to analyze the effect of the ionic wind on the particle collection efficiency in such systems. The high voltage magnitude and the frequency are the major parameters taken into account. With the wire-to-plane ESPs, PIV results show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and viscous forces. With this configuration, the particle trajectory is 3-D. In the case of the plane-to-plane ESP, a 2-D analysis of the time-averaged flow can be accepted. The time-averaged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of the ionic wind on the primary flow in such a configuration is negligible. The correlation between the electrohydrodynamic flow and the collection efficiency shows that increasing the ionic wind magnitude did not improve necessarily the electrostatic precipitation effectiveness of submicrometer particles, particularly using DBD precipitators.