One hundred and thirty-one spray nozzles were evaluated for use as reference nozzles for nozzle classification. Droplet spectra measurements showed that D{sub}(v0.1), D{sub}(v0.5), and D{sub}(v0.9) spectra indices did not overlap between classification categories except for one case when the addition of the standard deviation of the measurement was taken into account. Mean coefficients of variation (CV) for D{sub}(v0.1), D{sub}(v0.5), and D{sub}(v0.9) across all nozzles and all category thresholds were 3.8, 2.3, and 3.3, respectively. Mean spreads (difference between maximum and minimum, divided by mean) within D{sub}(v0.1), D{sub}(v0.5), and D{sub}(v0.9) across all nozzles and all category thresholds were 13.0, 8.6, and 12.8, respectively. A subset of 25 of the nozzles were identified to serve as dedicated reference nozzles to support an ASAE Standard (X-572) to reduce variation in nozzle classification. Mean CV values of this subset across all category thresholds were 1.9, 0.9, and 2.0 for D{sub}(v0.1), D{sub}(v0.5), and D{sub}(v0.9), respectively. Similarly, mean spread values were 4.5, 2.1, and 5.0 for D{sub}(v0.1), D{sub}(v0.5), and D{sub}(v0.9), respectively. These levels were below those for nozzles reported in the literature used for a test of laser instruments. An inference of the results is that differences found between "identical" presorted nozzles raise the issue of uniformity in the manufacturing of nozzles. Nozzle samples being classified should be representative of production samples. Nozzle design, manufacturing, and tooling changes, with subsequent effects on droplet spectra, should be monitored to ensure accurate nozzle classification.
展开▼
