Experimental and theoretical performance of a vacuum seeder nozzle for vegetable seeds

The performance of a vacuum seeder depends on several variables that interact in a complex way. The maximum distance at which seeds may be picked up from the nozzle, depends on the dimensions of the nozzle, on the depression applied at the nozzle and on the shape and dimensions of the seeds themselves. A mathematical model was devised, based on the general principles of fluid dynamics, and valid for seeds with a round shape, to identify the major parameters regulating the phenomenon. Experimental tests, with a vacuum pick-up device, were carried out to measure the maximum distance at which pick-up took place, when the depression was varied in the interval from zero to 80 kPa. The tests were carried out for four different types of seeds and seven different nozzles. For all nozzles and seeds tested, it was found that depressions in excess of 20 kPa did not substantially increase the pick-up distance. © 1996 Silsoe Research Institute.