DETERMINING EFFECTS OF FERTILIZER PARTICLE-SHAPE ON AERODYNAMIC PROPERTIES

A method was investigated for determining the extent to which aerodyna mic properties of fertilizer particles can be explained by a combinati on of turbulent airflow theory and a response surface involving geomet ric shape and mass of particles for a sample of specific fertilizer ma terial. Fall tests were conducted, where particles were dropped and fa ll times were described by a mathematical model using turbulent airflo w theory. Secondly, a measure of particle shape was determined to expl ain the difference between theoretical and measured fall times. Variou s dimensions of particles were measured using digital image processing . Absolute radius deviations from a preassumed best-fit circular shape were recorded and combined from two perpendicular particle images and designated ''shape factor''. For a sample of calcium ammonium nitrate (CAN) particles, the shape factor ranged from 11.8 to 73.0 (perfect s pheres are zero). Over that range, the difference between theoretical and measured fall times was satisfactorily explained (R(2) = 0.82) by a function of shape factor and particle mass. A new approach to charac terize a bulk of fertilizer material and its spreading properties was proposed.