Synchronized droplet size measurements for coal-water slurry (CWS) diesel sprays of an electronically-controlled fuel injection system
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Experiments were completed to study intermittent coal-water slurry (CWS) fuel sprays injected from an electronically-controlled accumulator injector system. A laser diffraction particle analyzing (LDPA) technique was used to measure the spray diameters (Sauter mean diameter, SMD) assuming the Rosin-Rammler two parameter model. In order to ensure an accurate synchronization of the measurement with the intermittent sprays, a new synchronization technique was developed using the light extinction signal as a triggering source for the data taking initiation. This technique allowed measurement of SMDs near the spray tip where the light extinction was low and the data were free from the multiscattering bias. Coal-water slurry fuel with 50% coal loading in mass containing 5 m mass median diameter coal particulates was considered. Injection pressures ranging from 28 to 110 MPa, 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 were studied. Measurements were made for pressurized (2.0 MPa in gauge) and for ambient chamber conditions. The spray SMD showed an increase with the distance of the axial measurement location and with the ambient gas density, and showed a decrease with increasing injection pressure. A correlation of the Sauter mean diameter with the injection conditions was determined as SMD = 0.279P-0.702A0.285x1.521 showing a satisfactory agreement with the measured SMD data. The results were also compared with previous SMD correlations that were available only for diesel fuel sprays.
