A study on the electrohydrodynamic flow in a rectangular impactor with positive corona discharge

Visualization experiments and numerical simulations were performed to investigate the electrohydrodynamic flow in a rectangular slit impactor. Smoke was used to trace the flow, while flow visualization was carried out using a pulse laser sheet technique. This study focuses on the interactions between the impactor airflow (i.e., primary flow) and the electric wind due to the positive polarity of the corona discharge. The Reynolds number for the primary flow varies from 500 to 2500, and the applied voltage on the corona discharge wire ranges from 10 kV to 12 kV. Flow visualization shows that the positive corona discharge produces a stable electrohydrodynamic flow, and that the streamlines between the throat exit and the impaction plate become narrow with decreasing electric Froude number, FR. The axial velocity at the throat exit is accelerated due to the reduced flow cross-sectional area. Thus, as a result of the high electric body force, the shape of the streamline resembles a jet. It can be predicted that the critical Stokes number will decrease when a positive corona discharge is generated in the rectangular impactor. Furthermore, the electric wind may play a role in enhancing the collection efficiency of electrostatic precipitators. Finally, the experimental results and numerical simulations exhibit good qualitative agreement.