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Comparisons are discussed of computed and measured transient sprays from an air-assisted fuel injector. Although the measurements were extensive, they did not characterize fully the conditions at the nozzle exit which had to be obtained from a simple model of the flow within the injector. It is found that spray width, spray tip penetration, amount of spray found in the head vortex, and chamber fuel distribution are strong functions of the internal design of the fuel injector. Particularly important are the drop size distribution and the direction of the flow at the exit of the nozzle.

The objective of this study is to characterize the operation of an air-assisted fuel injector. This characterization involves four sets of tests: fuel and air flow calibration; instantaneous measurements of fuel and air solenoid signals, internal pressure in the injector, and poppet lift; photographs of the spray; and droplet sizing. The injector poppet was designed to form a spray of 80° included angle. Nitrogen, instead of air, was used to assist the injection of unleaded gasoline into steady, compressed nitrogen at room temperature. The following conditions were used: nominal fuel flow rates of 10, 20, and 30 mm3/injection; spray chamber pressures of 0.1, 0.169, and 0.445 MPa; and nominal injections per minute (IPM) of 1600 and 3000. Results showed a linear increase in total fuel mass supplied to the injector as fuel solenoid pulse width was increased, except at the highest IPM and chamber pressure when the total fuel mass tended to level off.