Magnetic Resonance Imaging of two-phase systems

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Directly or indirectly, humans encounter bubbles and sprays all the time: by driving a diesel car or riding a bus (diesel fuel sprays), by using electricity from hydro/heat/nuclear plants (bubbles erode hydroplant turbines and are active agents of corrosion in cooling systems) or by eating vegetables (most likely treated with insecticide sprays). Whether you design a geo-engineering project to spray salt water on a massive scale to fight global warming or build a bubble column reactor to produce biofuel from algae, an understanding of processes involving bubbles and droplets is of fundamental importance. To develop that understanding, reliable, quantitative measurements of bubbly flows and droplets in sprays are necessary. Commonly employed measurement techniques in studies of bubbly flows and sprays are optics-based. However, as both bubbles and droplets reflect light, optical techniques become ineffective at high bubble and spray densities. This project proposes to use Magnetic Resonance Imaging (MRI) for studies of bubbly flows and sprays. Commonly employed as a diagnostic modality in clinics, MRI is also steadily becoming an essential tool in studies of materials because of its advantages as a non-invasive, inherently 3-dimensional method which can be sensitive to a wide variety of physical and chemical parameters and which does not require any optical transparency. In bubbly flows, new techniques of measuring microbubble sizes, mobility and bubble-induced mixing will be developed and evaluated on bubble column prototypes. In spray research, a spray chamber will be built inside an MRI scanner. New approaches to study droplet evaporation, size, velocities and other parameters with MRI will be investigated, permitting imaging at very short time scales in the regions previously inaccessible by other methods.