Electrohydrodynamic Flow and Particle Transport Mechanism in Electrostatic Precipitators with Cavity Walls

The electrohydrodynamic (EHD) flow induced by the corona wind was observed in a model electrostatic precipitator (ESP) of the simple geometry composed of the plates with a cavity. And the influence of the EHD flow and the turbulence condition of inlet cross-flow on the particle behavior inside the ESP and its collection efficiency were elucidated through experimental and numerical analysis. The profiles of streamwise gas velocities and turbulence intensities were measured in the ESP with a laser Doppler anemometer.A laser beam sheet visualized particle trajectories. Collection efficiencies were measured with a particle counter. In addition, numerical computations were performed to compare with the experimental results. The numerical results showed good agreement with the experimental data. As the corona voltage increased, the gas velocities of the core flow and the circulating flow inside the cavity increased due to the corona wind and the turbulence intensity increased near the cavity region. As the corona voltage increased for the low bulk gas velocity, corona wind prevented the particle transport into the cavity. And the particle transport into the cavity by turbulent dispersion was observed as the bulk gas velocity increased. When the flow with high turbulence intensity entered the ESP, the turbulent dispersion enhanced the transport of particles into the cavity; hence, the collection efficiency was higher compared with the case of the relatively lower inlet turbulence intensity below a critical corona voltage. However, the collection efficiency was slightly lower for the high inlet turbulence than for the low inlet turbulence above the critical corona voltage due to the turbulent diffusion of particles toward the centerline downstream from the corona wire.