Acquisition of a High-Energy, Narrow Linewidth Laser for Gas-Phase Scalar Mixing Studies in Turbulent Spray Flows

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0853513SuttonThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This is small equipment grant for the acquisition of a high-energy, narrow-linewidth, injection-seeded Nd:YAG laser. This instrument will be the primary component for advanced imaging studies to investigate the gas-phase scalar mixing in turbulent spray flows. Probably the best known examples of turbulent sprays exist in practical energy conversion systems where a liquid fuel issues into an oxidizing environment, disperses, evaporates, and mixes with the oxidizer before reacting. Although these systems are complicated by several physical and chemical processes, they are ultimately limited by the rate that liquid fuel evaporates and the fuel vapor mixes with the oxidizer at the finest physical length scales. Gas-phase scalar mixing, while studied in-depth for single-phase turbulent flows, has not been studied extensively in multiphase flow environments primarily due a lack to reliable experimental techniques that can determine the gas-phase concentration with sufficient accuracy. The PI intends to use the procured laser to validate a new experimental methodology for a novel variation of the Filtered Rayleigh Scattering (FRS) imaging technique to quantitatively measure the vapor-phase scalar concentration discriminately in the presence of liquid-phase droplets. Important quantities such as the gas-phase mixture fraction, which describes the degree of mixing between two non-premixed streams, and the scalar dissipation rate, which describes the that the two streams mix, may be derived without interference from the droplets. Such measurements are crucial for understanding the fundamental physics describing the evaporation of the liquid phase and the subsequent mixing of the vapor phase. In addition, these measurements will provide valuable assessment and development support for Large-Eddy Simulation modeling of turbulent sprays. Multiphase turbulent flows are of significant interest in many engineering applications including direct-injection automotive engines, liquid-propellant rocket engines, industrial furnaces, and water-mist fire-suppression systems. A graduate student will be supported directly by the PI to develop and implement the gas-phase scalar measurement technique. Every effort will be made to include the participation of students classified as underrepresented including women and ethnic minorities.