A mathematical model to predict the wear rate of nozzles with elliptical orifices
A mathematical model was developed to predict orifice wear rate for fan-pattern, spray nozzles. Variables affecting nozzle wear rate in the model are usage time, spray pressure, initial orifice size, effective coefficient of friction between orifice wall and fluid, orifice material, and the fluid. Spray-pattern measurements for new and worn orifices verified that wear mainly increased minor-axis length of the elliptical orifice with very little wear at the ends of the major axis. There was good agreement between predicted and measured flow rate increases for worn orifices with various materials and nominal capacities for up to about 38% increase in flow rate relative to new orifices. Both the model and experiments indicated nozzle wear rate increased with usage time, spray pressure, effective coefficient of friction between nozzle orifice wall and fluid, and ratio of major to minor axis of the elliptical orifice.