Effect of a filamentary discharge on the particle trajectory in a plane-to-plane DBD precipitator

In this paper, particle velocity fields inside a plane-to-plane dielectric barrier discharge (DBD) precipitator are investigated using time-resolved particle image velocimetry. The main objective is to analyse the effect of a filamentary discharge on the particle trajectory. A sine wave high voltage (24 kV, 30 Hz) is applied to create a DBD inside a planar gap (6.4 mm) filled with particles with a mean size of about 0.28 μm. The time-averaged velocity of the flow in the centre of the channel is about 1 m s-1. After the establishment of the discharge several filaments cross the gap, and induce a strong effect on the particle trajectory. During a complete period of the voltage, successive phenomena are observed. Before the first filament propagation, the shape of the velocity profiles is typical of a laminar flow. At the early stage following the filament propagation across the gap, the grey-level images show a sudden disappearance of the particles at the same location where the filament takes place. This is due to the fast precipitation of particles. During the positive half-cycle, the particles migrate mainly towards the grounded electrode due to their positive net charge. At the end of a half-cycle, the polarity of the electric field is reversed then the particles initially charged return towards the channel centre. Consequently, the particles oscillate delaying their collection.