RHEOLOGY, FLOW AND ATOMIZATION OF COAL-OIL MIXTURES

here are two main objectives to this thesis; (1) To develop a practical method for determining the rheological properties of coal-oil mixtures under various concentration and temperature ranges, and (2) To determine pre-combustion atomization characteristics of the mixtures under different test conditions using an airblast atomizer.;The collected rheological data can be represented by any of the three two-parameter models: Power Law, Bingham Plastic, or Casson. However, the last two models are more realistic and consistent with the observations.;Atomization characteristics of coal-oil mixtures are studied by an experimental set-up consisting of an airblast atomizer fed from a flow control rig, which discharges through a spray channel into a storage tank. Vapors generated are removed via an exhaust system. The fully developed spray is photographed at different axial locations using a 35 mm camera equipped with a microflash designed for high speed photography. Slides and prints are analyzed to determine S.M.D. (Sauter Mean Diameter) using an (alpha)-Image Analyzer.;The results indicate that coal concentration and therefore viscosity have an adverse effect on S.M.D. Surface tension opposes the disintegration of droplets and an increase in liquid density causes a decrease in droplet size. Air velocity has an effective role on spray quality, the greater the air velocity the better the spray fineness.;Samples of stable coal-oil slurries have been prepared, with coal concentrations ranging from 30-50% by weight. Extensive rheological data was obtained using capillary and cone-plate viscometers for samples of coal-oil mixtures and...