Quality control of standardized reference spray nozzles

One hundred and thirty-one spray nozzles were evaluated for use as referenc e nozzles for nozzle classification. Droplet spectra measurements showed th at D-v0.1, D-v0.5, and D-v0.9 spectra indices did not overlap between class ification categories except for one case when the addition of the standard deviation of the measurement was taken into account. Mean coefficients of v ariation (CV) for D-v0.1, D-v0.5, and D-v0.9 across all nozzles and all cat egory thresholds were 3.8, 2.3, and 3.3%, respectively. Mean spreads (diffe rence between maximum and minimum, divided by mean) within D-v0.1, D-v0.5, and D-v0.9 across all nozzles and all category thresholds were 13.0, 8.6, a nd 12.8%, respectively. A subset of 25 of the nozzles were identified to se rve as dedicated reference nozzles to support an ASAE Standard (X-572) to r educe variation in nozzle classification. Mean CV values of this subset acr oss all category thresholds were 1.9, 0.9, and 2.0% for D-v0.1, D-v0.5, and D-v0.9, respectively. Similarly, mean spread values were 4.5, 2.1, and 5.0 % for D-v0.1, D-v0.5, and D-v0.9, respectively. These levels were below tho se for nozzles reported in the literature used for a test of laser instrume nts. An inference of the results is that differences found between "identic al" presorted nozzles raise the issue of uniformity in the manufacturing of nozzles. Nozzle samples being classified should be representative of produ ction samples. Nozzle design, manufacturing, and tooling changes, with subs equent effects on droplet spectra, should be monitored to ensure accurate n ozzle classification.