A Diagnostic for Simultaneous Liquid and Vapor Distribution in Sprays Using Filtered Rayleigh and Mie Scattering

New automotive engine technologies, such as direct injection with stratified charge combustion, are being explored under programs of the DOE and others that offer significant increases in efficiency and reductions in emissions. Research tools are needed to help determine how best to adequately control the combustion process throughout the engine operating envelope, to optimize combustion efficiency, and to prevent misfires and partial burn. Advanced fuel injector spray patterns can be complex, and quantitative measurements of the spray structure are needed, but current diagnostic systems lack the ability to measure fuel/air mixture distributions in the critical regions of the spray. MetroLaser, Inc. and the Ohio State University (OSU) are developing a diagnostic system that combines filtered Rayleigh scattering (FRS) with Mie scattering to allow imaging of both liquid and vaporized fuel simultaneously in a fuel injector spray. A sheet of laser light illuminates the region of interest and two cameras view the laser sheet, one employing FRS that blocks scattering from droplets to measure fuel vapor, and the other measuring Mie-scattered light from droplets to obtain the droplet distribution. In the Phase I, a model of the FRS signal was developed for various single-component hydrocarbon fuels, and was validated experimentally. Excellent agreement was seen between model and data for simple fuels, and results for more complex fuels were encouraging as well. Measurements were performed using the FRS/Mie technique in an evaporating fuel spray at room temperature and pressure, proving feasibility by demonstrating quantitative two- dimensional (2D) distributions of fuel/air mixture ratio and droplet distributions. In Phase II, the model will be extended to improve the accuracy for the more complex fuels, and will be validated by comparison with experimental data at thermodynamic conditions representative of an engine. A prototype FRS/Mie system will be constructed and developed in a constant flow spray facility at moderate pressure, and finally demonstrated on a fuel injector spray in a model combustion chamber at engine conditions. Commercial Applications and Other Benefits: The proposed diagnostic technique should help bring about significant improvements in energy efficiency, reduced fuel use, and reduced emissions in vehicles by providing engine designers with a tool to better quantify fuel injection dynamics. Boosting the efficiency of internal combustion engines is one of the most promising and cost-effective approaches to increasing vehicle fuel economy. This diagnostic system would provide a critically important capability needed to help achieve a 20 to 40 percent reduction in fuel use, which the DOE estimates can be attained through commercialization of advanced engines.