AIR-JET VELOCITIES FROM A CROSS-FLOW FAN SPRAYER

Transverse profiles of air velocity were measured along the jet centerlines at 0.05 to 6 m (0.16 to 20 ft) from the outlet of a two-unit, cross-flow fan orchard sprayer. Velocity profiles were obtained for fan speeds of 1080 and 1476 rpm and with the upper fan both vertical and inclined downward 20-degrees from vertical. Observed maximum velocities along the lower jet centerline agreed with those predicted by a plane jet model. Outlet air velocity at 1476 rpm was about 1.6 times the velocity at 1080 rpm. For an inclined upper fan, air velocities at the lower elevation increased 10% at 3 m (9.8 ft) from the outlet. When the upper fan was inclined 20-degrees, the interaction of the two jets appeared to form a persistent flow field in which velocities alternately increased and decreased over the range from 0.15 to 1 m (0.49 to 3.3 ft) from the outlet. The inclined upper jet apparently deflected the top of the lower jet toward the ground, which may tend to keep spray-droplets near the ground and thereby reduce drift loss from spray operations.