NSF Young Investigator Award

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This research program focuses on the fundamentals of electrostatic spraying and some novel applications of this technology in the areas of multiphase combustion and targeted aerosol drug therapy. The objective of the first application is the study of the formation and burning of electrosprays of liquid fuels at both normal and reduced gravity in laminar and turbulent flow regimes. The underlying philosophical approach is that of providing an experimental arrangement that will allow a systematic study of spray evolution and burning in configurations of successively increasing levels of complexity, starting from laminar sprays to fully turbulent ones. A counterflow diffusion flame burner has been designed and used to stabilize a self-sustained ES flame of haptene. This configuration allows the decoupling of droplet-droplet and droplet-gas interactions from turbulence complications and represents a well-defined two-phase combustion flow whose ambient field can be systematically varied. The ultimate goal of this experimental approach is that of eventually burning in a regime of three-dimensional droplet-droplet interaction, for which no experimental results are currently available. The next level of complexity involves the "injection" of turbulence into the gas stream with synthesis of various turbulence scenarios characterized by different intensities and scales. These experiments will address the issue of droplets/turbulence interaction which manifests itself as a two-way coupling. As part of this activity, experiments will be conducted in a drop-tower facility to delineate the effects of natural convection on combustion of electrosprays. A second electrospray application lies in the area of aerosol drug therapy, whereby acute and chronic respiratory diseases are treated by administration of a variety of substances as airborne dispersions of small "particles", typically composed of pure liquids or liquid mixtures such as water or aqueous saline solutions, in which drugs are either dissolved or suspended. An electrostatic spray appears to be an excellent candidate for this task, since under appropriate experimental conditions it is capable of generating monodisperse droplets of arbitrary size and can be used to aerosolize pure liquids or suspensions of macromolecules (thus lending itself to dispersion of liposome encapsulated agents). Aqueous saline solutions and suspensions of liposomes in a liquid carrier will be electrosprayed to generate droplets of controlled size and size distribution in the 1-8 micron range for targeted pulmonary deposition. Effects of liquid flow rate, physical properties, and electric field on the generated droplets will be studied. The influence of a delivery line in the path from generation to inhalation on the aerosol size distribution and transmission will also be investigated.