Aerosolization of particles from a bubbling liquid: Characteristics and generator development

A new aerosol generator is introduced in which particles suspended in a liquid are aerosolized by gentle bubble bursting. Tangential injection of dry air to the bubbling surface dries the airborne droplets immediately after aerosolization so that they rapidly shrink in size and are carried out from the generator by inward and upward swirling air motion. The new generator has been evaluated with monodisperse PSL particles in the size range of 0.73–5.1 μm and with a saline solution using a time-of-flight aerodynamic particle size spectrometer (Aerosizer). It was found that, in contrast to pneumatic nebulization (e.g., with a Collison nebulizer), the new generator's output in undesirable liquid droplets is very small, while its output in dry PSL particles is high. When using the new aerosol generator, a minimum number of the nebulized droplets is returned to the liquid pool, thus optimizing the number of particles available as test aerosols. The aerosol concentration was found to be constant and stable for at least 30 min with the prototype generator tested. It is shown that the relative humidity of the effluent flow can be regulated. For microorganisms aerosolized by this generator, the shear stress is expected to be considerably lower than in conventional aerosol generators.