Herbicide application using a fluid‐driven rotary atomizer

Abstract

Hand held electrically driven spinning disc atomizers are capable of applying herbicides more efficiently than with hydraulic nozzles, because the narrower droplet spectra they produce reduce drift and wastage of chemical. Despite these savings, however, farmers are frequently reluctant to use such methods because of poor reliability, and high maintenance costs of the electrical drive systems. Therefore an alternative drive system has been examined, which uses a jet of the pesticide fluid to power the atomizer. Experiments were carried out to increase understanding of the processes involved, and an optimum design has been produced, which is suitable for attaching to a knapsack sprayer in place of a hydraulic nozzle. The fluid drive mechanism is comparable to that of a Pelton wheel; driving torque arises from a change in momentum of a fluid jet as it strikes the inside of a cup, causing it to rotate. The fluid is emitted from grooves and teeth to form ligaments which produce uniform droplets. Peripheral distribution of fluid is made uniform by a series of slotted weirs on the inside wall of the cup. Spectral and deposit characteristics are satisfactory for CDA herbicide application with water‐based formulations, but an antifoaming agent must be added to formulations containing surfactant. Typical volume median diameters are of the order of 250 μm, and optimum swath width is 1.2 m for an intended application rate of 30–40 litres/ha.

Keywords:

• spinning disc
• fluid‐driven
• herbicide