Unimpeded Air Velocity Profiles of an Air-Assisted Five-Port Sprayer

Abstract

A capability that relies on tree structure information to control the flow rates of liquid and air 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-1. 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 the 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 nozzles. When the sprayer was stationary (0 km h-1), axial air velocities from the nozzle outlets increased as fan inlet diameter increased and decreased as a hyperbolic function as the distance increased. Variations in the peak air velocities and airflow pressures with travel speeds of 3.2 to 8.0 km h-1 and heights of 0.2 to 2.0 m were statistically insignificant. When the sprayer was in motion and due to air entrainment and air jet disturbance, the peak air velocities decreased and airflow pressures increased as distance from the nozzle outlets increased. For all parameters tested, the peak air velocities and airflow pressure increased as fan inlet diameter increased, demonstrating that changing the fan inlet diameter achieved variable airflow rates with uniform air profiles.