Experimental study on electrostatic particle deposition from gas-solids two-phase flow based on tribo-electrification

摘要

Electrostatic particle deposition on a target embedded in a substrate under a locally applied voltage has been investigated experimentally based on the tribo-electrification of particles.Initially particles deposit mainly on the edge of the target because of the contact potential difference between substrate (poly(mefhyl methacrylate)) and target (brass).The thickness of particle layer formed by the deposited particles increases with time,but gradually saturates.Since then almost no additional particles deposit on the target.When high voltage is applied to the target,an orange peel phenomenon is observed on the surface of the particle layer.In the central region of the target,the particles under high Stokes number,St,do not deposit because of the particle rebound and the resuspension of deposited particles.The larger the Coulombic force parameter K_E,the higher the effective deposition velocity is.The velocity increases dramatically for Z+E>6X 10~(-6) and 20 < St < 60.The larger Stokes number makes the coefficient of variation larger for the thickness of the particle layer,i.e.the deposition under higher Stokes number gives a less uniform deposition layer.However,for St < 10,particles deposit almost uniformly.For the deposition under a larger Coulombic force parameter,onset of the rebound and resuspension is suppressed,and the region with a uniform deposition layer is shifted to a higher Stokes number.It is also found that particles can successfully deposit on a non-conductive target of a dielectric substance through setting a grounded guard electrode around the target.