COMPARISON BY IMAGE PROCESSING OF TARGET SUPPORTS OF SPRAY DROPLETS

Abstract

Laboratory tests make it possible to compare or evaluate the performances of spraying nozzles (output, transversaldistribution, angle, resistance to wear, etc.). The characterization by image processing of the spectrum of droplets depositedon a target is an interesting complementary technique for which the spraying target has great importance. An experiment wasconducted to compare three commonly used artificial targets: watersensitive paper, Petri dish containing two silicone oils(according to the ISO Standard 56821), and glass slide. The variability between targets of the same kind was studied throughvolumetrically similar droplets deposited by means of a micrometric needle. Image processing of spray droplets gave theirdiameter. A
2 test sorted the three targets in ascending order of variability: silicone oils, glass, and far more variable, thewatersensitive paper. A spread factor was calculated for each type of target. The targets were also compared in practicalspraying conditions. The median and average diameters, the standard deviation, and the degree of skewness of Fisher werecompared by analyzing the variance for pressures ranging between 200 and 400 kPa while maintaining a sprayed volumeof 100 l/ha. The choice of target depends on the use envisioned. This study revealed that the Petri dish with silicone oils wasappropriate to carry out a precision measurement and to serve as a reference, but its implementation is delicate. The glassslide target was easy to use and had a low variability; however, quick drying of the smallest droplets can limit its use. Thewatersensitive paper was the easiest to use, but it must be reserved for qualitative observations.