Location: Application Technology ResearchTitle: Unimpeded air velocity profiles of air-assisted five-port sprayer Author
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2012
Publication Date: 12/21/2012
Publication URL: http://handle.nal.usda.gov/10113/56247
Citation: Gu, J., Zhu, H., Ding, W. 2012. Unimpeded air velocity profiles of air-assisted five-port sprayer. Transactions of the ASABE. 55(5):1659-1666. Interpretive Summary: Although current air-assisted sprayers provide improved spray penetration and deposition uniformity, they are not able to adjust both liquid and air flow rates as needed and thus spray losses are still considerable. Future variable-rate sprayers should have a capability to control both liquid and air flows to match tree canopy structures. This study investigated the effect of fan inlet diameters on characterization of air velocity profiles from an air-assisted five-port sprayer, in an effort to form a basis for the development of an automatic device to control the air flow rate for the future variable-rate sprayers. Test results demonstrated that the air velocities and airflow pressures for a particular fan inlet diameter were relatively uniform, confirming the capability of the sprayer to discharge uniform spray profiles for carrying droplets. Consequently, this study established an alternative approach with changing the fan-inlet diameter to achieve variable rates of air for new pesticide sprayers to have efficient air flow penetration into plant canopies.
Technical Abstract: 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.