New Approaches to Spraying Pesticides

Prof. W. Zadorsky

New ways to extend nozzle life and improve spraying performance have been devised in Dnipropetrovsk. They can be combined with jet electric charging to form electrosol during or directly after atomization of liquid.

The air-liquid mix in a sprayer may contain dirt, sand and other abrasive particles, especially when the sprayer is operated in an arid area. Clogging and/or rapid erosion may occur with a conventional nozzle whose orifice is 1 mm or less in diameter. The erosion wear results in widening of the orifice and in poor jet performance, for the droplets become bigger and the jet torch less dense.

1. To prevent this, it is suggested to atomize a two-phase fluid (foam) instead of the single-phase liquid. The foam is formed by a specially designed cocurrent generator featuring multiple phase inversion. Since the foam is 5 to 10 less dense than the starting liquid, the orifice diameter may be increased accordingly.

The tests on new nozzles demonstrated that their life was extended, their performance improved and clogging eliminated. The liquid drops formed from foam turned out to be smaller and more uniform in size than those forced from conventional nozzles.

Pressurized air from a tractor-driven compressor was used at the preatomizing step, although precooled exhaust gases from the tractor engine may be used instead.

2. Another technical solution was suggested by Prof. V.P. Koval of Dnipropetrovsk University. The nozzle inner configuration is designed so that vortices are generated that isolate the solid particles from the orifice wall surface. This reduces wear on the walls. Also, rectangular orifices may be used instead of round ones. This simplifies nozzle fabrication and enables a severalfold decrease in operating pressure.

Prof. Vladimir Koval also suggested that the pesticide not be premixed but rather fed via a distinct pipe to be mixed with water inside the nozzle. This reduces the risk of soil contamination and the personal hazard to operators. The chemical agent line is switched off, lending itself to thorough flushing with water.

This type of nozzle has been commercialized.

It is desirable to carry out comparison tests of the two nozzle types.

Contact Professor William Zadorsky at

Information supplied by the Author April 1999.  Page last updated: January 19, 2004