Use of Electric Image Forces for Collection of Aerosols by Arrays of Drops

The use of electric image forces for collection of uncharged aerosols by two- and three-dimensional arrays of charged drops is considered. Trajectories of aerosols are simulated using an algorithm for transformation of electric image forces and flow field from spherical coordinate systems of the drops to the central system, where the equation of motion is solved. Radius and efficiency of collection of aerosols, as a function of the number of rows of drops, are presented for different geometries and charge levels. The nature of the weak image force dictates the need to use a charge level closer to the Rayleigh limit and optimized array geometries. Inertial effects that enhance dispersive modes, of otherwise convergent trajectories, become significant for aerosols as small as 20 w m. In this case, multiple values of radius of collection and collection efficiency can be obtained for the same number of rows. Geometries with no shifts between rows of drops are shown to be inferior to those involving a larger shift. The former geometries require a substantially larger number of rows for a prescribed level of collection and may not facilitate complete collection. Systems of uncharged drops and charged aerosols behave similarly to those with charged drops and uncharged aerosols. Three-dimensional arrays can be more efficient than two-dimensional ones, provided that weakness planes, where aerosols show deep penetration, are eliminated by appropriate shifts of rows. A decrease of the drop size at a fixed volume fraction with the charge set at its Rayleigh limit enhances the collection efficiency. Finally, the random model of collection, using the exponential distribution, is recast in order to accommodate for the effect of the order of the array and the deterministic nature of the aerosol trajectories.