Mechanism of aerosol collection by two- and three-dimensional inhomogeneous arrays of charged drops

Three- and two-dimensional trajectories of charged aerosols, in a system of three- and two-dimensional array of oppositely charged drops, are computed by a new simulation model. The trajectory pattern of the aerosol is shown to depend on the size and geometry of the array, as well as on operational parameters, such as charge and size of drops and aerosols. Low-inertia aero sols that are collected by the large arrays of drops, exhibit "column conve rgence", whereas smaller arrays produce "array convergence" that involves f ocusing of trajectories toward the symmetry axis. High-inertia aerosols exh ibit "array dispersion" in which trajectories spread across the array. The concepts of the collection radius and collection efficiencies are reviewed, and redefined, with respect to the number of rows that are required for im pact of the aerosols on collecting drops. It is shown that the concept of c ollection radius becomes ambiguous, once its monotonic relation to the numb er of rows ceases to exist, and for high-inertia aerosols it becomes meanin gless. Inhomogeneous arrays exhibit unique collection patterns that involve by-passing effects. Collection efficiencies are enhanced by setting the in itial position of the aerosol closer to, and then, inside the array. Initia l positions, which are set inside the array, eliminate the erratic trajecto ries observed for aerosols that start their motion outside the array. Final ly, the use of fixed geometry arrays provides conservative estimates of the collection efficiencies, which are predicted to be high, within the constr aints set by the stability of the drops, and the technology available for t heir charging. (C) 2000 Elsevier Science Ltd. All rights reserved.