CHARACTERIZATION OF FULLY DEVELOPED AIR-ASSISTED SPRAY UNSTEADINESS USING RP-3 JET FUEL

The ideal spray theory of Edwards and Marx was utilized to investigate the dependence of fully developed intermittent air-assisted spray unsteadiness on operational conditions and fluid properties. Time series information of spray droplets was identified by phase Doppler particle analyzer and used for inter-particle arrival time statistics. Results demonstrated that spray unsteadiness along the spray axis and in proximity to the nozzle exit area is more pronounced than far-nozzle field and spray periphery. The unsteadiness on the spray axis exhibits a decreasing function with the fuel injection durations, whereas an increase of air injection duration significantly elongates the unstable region along the spray axis. The properties of test liquid fuels show a moderate effect on the unsteadiness of the air-assisted spray, potentially due to their inconspicuous influences on spray atomization characteristics. Chi-square method is generally the preferred method for quantifying the global spray unsteadiness when compared to the deviation of the first time gap of experimental and theoretical inter-particle time distribution. Unsteadiness results observed during high-velocity droplet spray stage are relatively distinct compared to droplet deceleration and suspension stages. This distinction can be attributed to the continuous energy input during the initial nozzle opening, emphasizing the significance of droplet velocity in determining spray unsteadiness.