Flow variability of an aerial variable-rate nozzle at constant pressures

Authors: Martin, Daniel - Dan

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2013
Publication Date: 8/22/2013
Citation: Martin, D.E. 2013. Flow variability of an aerial variable-rate nozzle at constant pressures. Applied Engineering in Agriculture. 29:483-488.

Interpretive Summary: Variable-rate spray systems have been successfully used for ground-based application, but high application speeds, flow requirements, and aerodynamic considerations have slowed development of variable-rate nozzles that are effective for aerial application. A new commercially-available, aerial variable-rate nozzle was found to provide nearly double the flowrate of conventional aerial nozzles. However, differences in flow rates between nozzles were excessive under standard operating procedures. These results will help aerial applicators make informed decisions when using aerial variable-rate nozzles for precision applications that can reduce the cost and quantity of applied agricultural chemicals.

Technical Abstract: Variable-rate ground application systems have been in use for the past 15 years, but due to high application speeds, flow requirements, and aerodynamic considerations, variable-rate aerial nozzles have not been available until now. In 2006, Spray Target, Inc. released the VeriRate™ variable-rate aerial nozzle, the first commercially-available retrofit aerial nozzle of its kind. Conventional, fixed-orifice, hydraulic aerial nozzles are physically and practically limited to a doubling of flow rate. This new variable-orifice aerial nozzle promised a 10X rate change. Using a standard aircraft spray boom, this study quantified flowrate and flowrate variability from a set of 48 VeriRate nozzles at spray pressures ranging from 207-483 kPa (30-70 psi). Results indicated an increase in the flowrate change that could be achieved with this nozzle (3.4X), but shy of the desired 10X rate change. Additionally, measured flowrate from the nozzles was dependent on the pressure-up sequence. Excess flow variability between nozzles was found when spray pressure was gradually applied to the nozzles. Initially "spiking" the spray pressure to 483 kPa (70 psi) removed virtually all excess flow variability, except at 207 kPa (30 psi).