Electric Field Effects on the Equilibrium and Small Signal Stabilization of Electrofluidized Beds

A continuum analysis is developed of electric field coupling to a charge-free fluidized bed of polarizable particles, with the electric field at an arbitrary angle to the gas flow. The electric force density and stress tensor is derived from the principle of virtual work and includes polarization and electrostriction forces but neglects Coulombic free charge forces. Effective medium theory for various particle structures derives the effective bed permittivity as a function of particle voidage and is used with the energy method to derive the electric. force density acting on the particles. Necessary force-free boundary conditions at the top free surface of the bed are developed. A linear stability analysis is used to find the conditions for electric field stabilization. Experiments with Rochelle salt show elimination of bubbling with collinear electric field and flow but never complete stabilization with crossed field and flow as predicted by the analysis. There is qualitative agreement between the stability analysis and measurements. Numerical differences are attributed to particle viscosity, which was not included in the fluid model.