An optical technique for reliably separating and quantifying the liquid and vapor phases of real fuels has been elusive. Challenges include multiple scattering in dense regions, complex laser interaction with the fuel, a wide range of length scales, and effects of temperature and pressure. This proposal seeks to overcome these difficulties by (1) introducing a new approach to distinguishing yet capturing both the liquid and vapor phases, (2) removing the effects of multiple scattering, (3) capturing single-shot planar images of droplets, droplet size distributions, and vapor concentrations, and (4) utilizing and calibrating for real fuels, such as JP-8. This will be accomplished through laser-induced fluorescence, phosphorescence, and Mie scattering combined with structured laser illumination. In addition to developing a simplified diagnostic platform to perform these combined diagnostics, significant effort will be expended to analyze data from cold and heated sprays to determine calibration parameters for specific fuels such as JP-8. The Phase I will show the feasibility of these proposed experimental methods, as well as identify strategies for Phase II development of the laser-based planar imaging hardware and software system.
Benefit: Proper fuel-air mixture preparation is critical for meeting the performance objectives of propulsion devices, including gas-turbine combustors, afterburners, pulsed-detonation engines, and rocket engines. The proposed work would provide new tools for visualizing the multiphase mixture preparation process in these devices for real fuels. This will enable researchers to study ignition, flame stabilization, combustion efficiency, and emissions as a function of injector design and operation conditions, leading to improved performance for the warfighter. In addition, the proposed laser diagnostic tools will be useful in a wide variety of multiphase flow applications, including commercial propulsion, stationary power generation, internal combustion engines, space heating, production of alternative fuels, and industrial sprays. Hence, the advanced diagnostic hardware for simultaneous detection of multiple planar images and calibrated signal interpretation algorithms should see wide commercial potential.
Keywords: Fuel Spray, Fuel Droplets, Fuel Vapor, Laser Diagnostics, Fluorescence, Phosphorescence, Mie Scattering
