A laboratory test bench for nozzle spray droplet analysis

This paper presents a low cost laboratory test bench, designed and built at the Section of Mechanics and Mechanisation of the Department of Agricoltura, Alimentazione e Ambiente (Di3A) to analyse nozzle sprays according to the procedure established by ISO 5682-1. Moreover, spraying at the same time natural (fruits or leaves) or artificial targets (water sensitive papers – WSP), it allows studying the correlations between spray features, water sensitive paper surface coverage and spray deposit on the targets. The test bench is made of a trolley with a 70 L tank, a diaphragm pump driven by a 230 V AC electric motor, a spray boom, pressure and flux transducers, and all the system control devices. The spray boom is applied to a mobile platform that moves along two rails parallel to the plane of the trolley, in such a way the distance between target and nozzle is 0.5 m. According to the procedure established by ISO 5682-1, the nozzle under test, while moving at a speed selectable in the range 0–1.5 m/s, sprays a test liquid above Petri dishes containing silicon oil of appropriate kinematic viscosity. The images of the drops trapped into the oil are acquired by using a high resolution (24 Mpixel) DSLR camera and then processed via image analysis software. Preliminary tests have shown the functionality of the whole system and the capability of the image analysis system of detecting drops of minimum diameter of 6 µm.