Turbulent flow energy for aerosolization of powder particles

The process of re-entrainment and re-dispersion of powder particles is studied both theoretically and experimentally in order to discuss the possibilities of improvement of the quality of aerosol emitted from dry powder inhalers (DPI). The eddy fluid particle model (EFPM) is employed to solve turbulent flow structure in the microscale in a channel with various types of turbulence promoters. The resuspension process caused by the gas shearing forces is modeled with the Verlet algorithm taking into account the inter-particle cohesive interactions. Nondimensional numbers are introduced to define the domains of powder aerosolization. Computational results indicate the importance of the geometry of turbulence promoters for powder re-entrainment (fluidization) and de-aggregation of particle clusters. The theoretical findings, are supported by experimental results obtained in a model resuspension chamber with a pharmaceutical powder (disodium cromoglycate). A noticeable increase of emission and re-dispersion was obtained at low airflow rates due to the use of turbulence promoters mounted in the vicinity of the powder layer. The corresponding increase of flow resistance is acceptable in respect to the practical application in DPIs. (C) 2007 Elsevier Ltd. All rights reserved.