Bipolar charge measurement of pharmaceutical powders

This paper presents the results of the experimental study on pharmaceutical powders using the Bipolar Charge Measurements System (BCMS) developed at Brunel University. The main function of the BCMS is to provide fast, simultaneous measurement capability of the bipolar charge fractions on pharmaceutical aerosols delivered from medical dispensers, primarily in the particle size range between 0.5 and 10 mum. The BCMS employs the principle of particle separation by means of electric field acting perpendicular to the flow field. The integrated particle flow bifurcator-precipitator is composed of two ("D" shape) sections incorporating three wire electrodes. During the operation of the system, the aerosol particles are sucked by a continuous flow of air into the bifurcation-precipitation section, which divides the air flow into two identical streams. These streams are simultaneously directed into two precipitator sections, where charged aerosol particles are precipitated and deposited on the surface of the measurement electrode. The bifurcator-precipitator section was analyzed numerically using an extended commercial CFD code to calculate the particle deposition within the precipitator due to the combined effect of the flow field and the electric field. Based on the Lagrangian approach, the trajectories of the particles were calculated considering electric and aerodynamic forces. (C) 2003 Elsevier B.V. All rights reserved.