Synchronized droplet size measurements of intermittent coal-water slurry diesel sprays from an electronically-controlled accumulator fuel injection system

Abstract

Experiments have been completed to characterize atomization of intermittent coal-water slurry sprays from an electronically controlled accumulator fuel injection system of a diesel fuel engine. A synchronized laser diffraction particle analyzer technique was used to measure the spray tip Sauter mean diameters (SMD). The Rosin-Rammler two parameter model was assumed for the droplet distribution. The measurements were made at the spray tip where laser obscuration was low and the chance of multiscattering bias was minimal. Coal-water slurry fuel with 50% coal loading by mass containing 5gm volume mean diameter coal particles was used. Injection pressures were ranged from 28 to II 0 MPa. Three different nozzle orifice diameters, 0.2, 0.4, and 0.6 mm, four axial measurement locations from 60 to 120 mm downstream of the nozzle tip were studied. Measurements were made for both pressurized (2.07 MPa, 300 psig) and unpressurized (ambient, 0 gage) chamber conditions. The spray tip SMD showed an increase with chamber gas density, and with axial measurement location, and showed a decrease with increasing injection pressure. The effect of nozzle orifice diameter on spray tip SMDs of completely developed sprays for such high pressure injections was found to be negligible. A regression equation for CWS-50 spray tip SMDs was determined as SMD = 0.279-P(inj).̄702 r(amb) 2̣85 x .521 where Pinj is the injection pressure in Mpa, r(amb) is the ambient density in kg/m3, and x is the axial measurement location downstream of the nozzle tip in mm. The equation shows very good agreement with the measured SMD data by having a Pearson correlation coefficient of 0.97. The results were also compared with previous SMD regression equations that were originally obtained for diesel fuel sprays.