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Show INTRODUCTION Coal-water slurries (CWSs) are being studied as potential alternatives in both coal- and oil-fired power plants. One basic advantage of coal-water slurry is the ability to handle it as a liquid fuel. As a liquid fuel, CWS will require an atomization process preceding combustion. The atomization process must generate a sufficient mass of fine particles for easy ignition and flame stability. Also, the atomization process must not generate an inordinate mass of large droplets. Large drops of slurry may not burn out in a combustor, resulting in fouling problems, or they may drop out to the combustor floor resulting in an overall decrease in combustion efficiency. Size measurements of atomized slurry droplets were made in conjunction with combustion studies. In the atomization tests, both the fuel flow and air/fuel mass flow ratio were varied. Drop size measurements were made using the Particle Sizing Interferometry (Visibility) Technique ^lK In this application, this technique has several limitations which required special precautions. Although complete size distributions were not obtained, the data indicated the correct trends over the size range measured. Measurement Technique The size of atomized coal-water slurry droplets was measured using the visibility technique. This technique, also known as Particle Sizing Interferometry (PSI), was originally proposed by Farmer ^ and used the same optical equipment as a dual-beam Laser Doppler Anemometer (LDA). A schematic of this equipment is shown in Figure 1. The beam of light from the laser is expanded as required, split into two equal intensity beams which pass through a transmitting lens (optional), and are crossed at a point in the spray. The receiving lens is positioned symmetrically with respect to the axes of the laser beam. Beam stops block the incident laser beams so that only the light scattered from droplets is focused onto the photodetector. Droplets passing through the crossing region of laser beams generate a scattered light signal - also shown in |