Effect of turbulent diffusion on particle transport and collection efficiency in electrostatic precipitators with cavity walls

Abstract

The electrohydrodynamic (EHD) flow induced by the corona wind was observed in a model ESP of the simple geometry composed of the plates with a cavity. The model ESP has been named ``a wire ? cavity plate ESP``. And the influence of the EHD flow and the turbulence condition of inlet cross-flow on the particle behavior inside the wire ? cavity plate ESP and its collection efficiency was elucidated through experimental and numerical analysis. The experimental studies were performed in a wire ? cavity plate ESP. The gas velocities of the core flow and the circulating flow inside the cavity increased due to the corona wind for increasing corona voltage. The turbulence intensity increased near the cavity region with the corona voltage, caused by the additional irregular circulating flow due to the corona wind. As the corona voltage increased for the low bulk gas velocity, corona wind prevented the particle transport into the cavity, which was observed from the visualization results of particle trajectories. 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. But the collection efficiency was very slightly lower for the high inlet turbulence than for the low inlet turbulence above the critical corona voltage, because of the turbulent diffusion of particles from the collecting electrode to the centerline downstream from the corona wire. Computational simulation was performed to compare the numerical predictions with the experimental results. The numerical computation showed the results correspondent with the experimental data. The laminar model was suitable for the weak EHD flow and the turbulent model for the strong EHD ...