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The trajectories of ne aerosol particles in the vicinity of a free falling collector droplet and their deposition on it were investigated numerically by solving the equations of motion of the particle and the droplet in quiescent air. The droplet was assumed to be charged to one half of the Rayleigh limit. The Coulomb, image, Stokes, inertial, and gravitational forces acting upon the particle near the droplet were taken into consideration in the equations of motion. The equations of the droplet motion were also incorporated into the set of equations including the Coulomb and image forces on the droplet due to the particle charge. The ow eld in the vicinity of the droplet was determined by numerical solution of the Navier -Stokes equations. The equations of particle motion were solved in threedimensional (3-D) space by the Runge -Kutta method of the fourth order. The collection ef ciency of the particles on the droplet was determined by searching the limiting trajectory within the entire space. The results for particles charged to 10 elementary charges of the same and opposite polarity as the droplet, as well as the electrically neutral ones, were compared. The assumption on the charge of the particle was rather arbitrary. It was assumed that particles are not intentionally charged but only possess a charge generated by tribocharging due to random contacts and were independent of the particle size. Charging the collector causes the Coulomb forces between these 2 species to improve particle deposition on the droplet and in this way the aerosol is removed from the gas. For the aerosol particles charged to the same polarity as the collector, the collection ef ciency is still higher than for uncharged particles due to the action of the image forces. In this case, the INTRODUCTIONThe problem of determination of the particle trajectories near a spherical collector occurs in electrostatic scrubbers, in which ne dust particles are removed by charged droplets, due to the attractive Coulomb forces. Such a technique eliminates many shortcomings inherent in conventional electrostatic precipitators and inertial scrubbers that do not allow for the effective control of the dust particles in the submicrometer size range. In conventional inertial scrubbers the inertial force of the particles smaller than a few ¹m in diameter is too low to deposit it effectively on the collector. In the case of conventional electrostatic precipitators, a low precipitation ef ciency of the dust particles in this size range is caused by the dif culty in charging them to levels higher than a few elementary charges, which results in a low particle mobility. In the electrostatic scrubbers the Coulomb force drives the particle toward the charged droplet.Deposition of charged airborne particles on an oppositely charged spherical collector has been investigated by many authors. However, the solutions have been obtained on numerous restrictive assumptions, one of which is the approximate model for the ow eld around the collector. Also, a xed, instead of a...

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