PM—Power and Machinery: Design Factors affecting Spray Characteristics and Drift Performance of Air Induction Nozzles

Abstract

A test air induction nozzle was designed and manufactured to investigate how some design parameters affected the characteristics of the spray and how the spray characteristics influenced drift. A droplet-sizing technique which uses laser imaging rather than light scattering was used to characterize the sprays in terms of size and velocity distributions. The quantity of air inside the droplets was estimated. Increasing both Venturi throat diameter and the size of the final orifice resulted in an increase in airflow rate, as did a reduction in liquid flow rate. Droplet size was affected mostly by the size of the final orifice and only slightly by the air intake. The estimated quantity of included air within droplets, however, was independent of the final orifice size but increased with air intake. For a given nozzle setting, each spray droplet appeared to have a density independent of its size, contrary to the previous suggestions. Spray drift was influenced mostly by droplet size, with the sprays with larger volume median diameters resulting in lower levels of drift. There was no measurable effect of droplet density on drift, since, it is suggested, this was counteracted by the effect of increased air and droplet velocities near the nozzle.