This program deals with the design, development, and application of novel laser diagnostic techniques for the study of spray/drop vaporization and combustion. The overall objective is accurate determination of such parameters as droplet temperature and temperature gradient profiles of the gas media surrounding one or more interacting burning droplets to provide fundamental knowledge regarding their combustion. The specific objectives of the Phase I program are: a) Improve and further develop an existing test facility for burning fuel droplet streams; b) Develop the point-diffraction interferometric technique in conjunction with digital image processing techniques to define the gas temperature field around a stream of burning drops; c) Apply rainbow thermometry to measure instantaneous liquid droplet temperatures; d) Investigate the feasibility of automatically integrating all this information to allow full reconstruction of the temperature field surrounding the droplets; and, e) Perform a preliminary assessment of measurement errors associated with the technique. The ultimate potential product is an instrument which would enable acquisition of fundamental information regarding the structure of the thermal fields surrounding interacting burning fuel droplets (notably, low-grade fuels) which is of paramount importance in development of future combustion systems which could utilize these fuels. Potential applications include development/use of a novel fuel injector system for existing internal combustion engines which would enable them to use low grade fuels at high efficiency and with minimal production of pollutants. These applications could significantly reduce U.S. dependency on foreign oil imports, and would help ensure world competitiveness and environmental responsibility in the use of low grade fuels.