OCR Text |
Show Rheology Many of the key physical properties of a CWS are associated with its flow properties. Not only do they determine its handling characteristics during transport and pumping, but the quality of atomization was also expected to be controlled by these properties. The approach taken in this study was to use extensive laboratory viscometer measurements to determine the effect of temperature, shear rate, and time at constant shear rate on the apparent viscosity of the various coal-water fuels tested. These results were correlated with pipe flow and atomization results. Atomization Atomization characterization tests were performed in B&W's recently completed atomization facility (Figure 2). This facility is equipped with state-of-the-art laser diagnostics and permits local droplet velocity, size distribution, and relative number density measurements to be made in large-scale sprays. The inside dimensions of the spray chamber are 8 feet square x 10 feet long. Mounted on opposing walls are two 4- x 8-foot plate glass windows that provide optical access to the spray for laser measurements, visual observation, and still and motion picture photography. A uniform, axial flow of air continually sweeps through the chamber to prevent the buildup of a "fog" of very fine droplets. This airflow is provided by a large, forced-draft fan and is straightened and uniformly distributed by the windbox. The atomizer barrel is inserted through the windbox as shown. A gas cleanup system attached to the downstream end of the chamber removes most of the spray droplets from the airstream before it is exhausted back into the atmosphere. In the case of CWS, the fuel collected in the gas cleanup system is pumped into a large holding tank for subsequent disposal. -6- |