The Venturi style dry-powder generator has air entering into one end of the venturi. The powder is fed into the narrowed throat of the venturi by the pressure differential. A funnel that is attached to the body of the venturi holds the powder supply. Then, shear flow disperses the powder into an aerosol in the expansion section. The total flow and the feed flow are functions of the compressed air pressure. The flow rate downstream of the Venturi tube is measured using a dry test meter.
A paper, “A Venturi Disperser as a Dry Powder Generator for Inhalation Studies”, by Y.S. Cheng, E.B. Barr and H.C. Yeh describes the design and operation based on the Venturi principle.
The table shows the stability of Aerosol Concentrations during a 1 month study.