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Unimpeded air velocity profiles of an air-assisted five-port sprayer

Gu, J., Zhu, H., Ding, W.
Transactions of the ASABE 2012 v.55 no.5 pp. 1659
air, air flow, air-assisted sprayers, anemometers, models, nozzles, orchards, plant architecture, temperature, trees, velocity
A capability that relies on tree structure information to control liquid and air flow rates is the preferential design in the development of variable-rate orchard and nursery sprayers. Unimpeded air jet velocities from an air assisted, five-port sprayer in an open field were measured at four heights above ground, seven distances up to 3 m from the sprayer outlets, and five sprayer travel speeds from 0 to 8.0 km/h. Air jet velocities were adjusted by changing the sprayer fan inlet diameter. Calculations of the air jet initial region length, transition length and expansion angle from five-port nozzles were computed with an air jet distribution model. The intersection between adjacent air jets from the five-port nozzles was determined from the air jet expansion angle. Air velocities were measured with a constant temperature anemometer system coupled with hot-wire sensors. The air jets expanded at a 50° angle and intersected with adjacent air jets at 0.027 m from the five-port nozzle. When the sprayer was stationary (0 km/h), axial air velocities from nozzle outlets increased as fan inlet diameters increased and decreased as a hyperbolic function as the distance increased. Variations in the peak air velocities and airflow pressures with the travel speeds of 3.2 to 8.0 km/h and heights of 0.2 to 2.0 m were insignificant. When the sprayer was in motion, due to air entrainment and air jet disturbance, the peak air velocities decreased and airflow pressures increased as the distances from nozzle outlets increased. For all the parameters tested, the peak air velocities and airflow pressure increased as the fan inlet diameters increased, demonstrating that changing fan inlet diameters achieved variable air flow rates with uniform air profiles.