Properly synchronized droplet sizing for intermittent high-pressure coal-water slurry (CWS) sprays using the light extinction as a triggering source
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Experimental study was conducted to investigate atomization characteristics near the tip of unsteady coal-water slurry (CWS) fuel sprays. High injection pressure CWS fuel sprays were generated from an electronically-controlled accumulator injector system. A laser diffraction particle analyzing (LDPA) technique was used to measure the droplet Sauter mean diameters (SMDs) of the sprays assuming a Rosin-Rammler two parameter model. In order to ensure the measurement accuracy and repeatability, a new synchronization technique was developed using the laser extinction signal as a triggering source for the data taking initiation. Coal-water slurry fuel contained 50% mass of coal particulates of 5 m mass median diameter (MMD). Injection pressures were ranged from 28 to 110 MPa with two different nozzle orifice diameters, 0.2 and 0.4 mm, and four axial measurement locations from 60 to 120 mm from the nozzle orifice. Measurements were made for both pressurized (2.0 MPa gauge) and atmospheric pressure chamber conditions for comparison. The spray tip SMDs showed a strong decrease with increasing injection pressure and a distinctive increase with the measurement location and with the ambient gas density. An experimental correlation was determined as SMD = 0.279 p-0.702a0.285x1.521.
