The main research objective was to determine the effectiveness of the CWF treatments on atomization quality when applied to an ultrafine coal-water fuel (solids loading reduced to 50%) and to gas turbine operating conditions (atomization at elevated pressures). Three fuel treatment techniques were studied: (1) heating of CWF under pressure to produce steam as the pressure drops during passage of the CWF through the atomizer nozzle, (2) absorption of CO/sub 2/ gas in the CWF to produce a similar effect, and (3) a combination of the two treatments above. These techniques were expected to produce secondary atomization, that is, disruptive shattering of CWF droplets subsequent to their leaving the atomizing nozzle, and to lead to better burnout and finer fly ash size distribution. A parallel objective was to present quantitative information on the spray characteristics (mean droplet size, radial distribution of droplet size, and spray shape) of CWF with and without fuel treatment, applicable to the design of CWF-burning gas turbine combustors. The experiments included laser diffraction droplet size measurements and high-speed photographic studies in the MIT Spray Test Facility to determine mean droplet size (mass median diameter), droplet size distribution, and spray shape and angle. Three systems of atomized sprays were studied: (1) water sprays heated to a range of temperatures at atmospheric pressure; (2) CWF sprays heated at atmospheric pressure to different temperatures; and (3) sprays at elevated pressure. 31 refs., 47 figs., 1 tab.