Computational Fluid Dynamics Modeling of a Pneumatic Air Jet Nozzle for an application in Coffee Fruit Harvesting

Abstract

This study deals with the design of a pneumatic air-jet nozzle for coffee fruits harvesting purposes. In steady-state conditions, a CFD finite element model was implemented to validate the nozzle design. We studied variations in the cavity length and outlet diameter of the nozzle under 5 bar of pressure and 140 Lt/min of caudal flow. Using additive manufacturing, three prototypes of the nozzles were created in onyx material. In addition, a pneumatic assembly was built by integrating a nozzle with a solenoid electro valve that allowed air to be discharged from a compressor. Using a high-speed video camera, we conducted an experiment to understand the air jet morphometry of each nozzle. The electro valve was operated at 42 Hz and the operating conditions were chosen based on simulations. CFD-derived velocity was compared with the filmed jets from the experiments to illustrate its turbulence. The results were analyzed in terms of their capacity to produce punctual impacts on coffee fruits Coffea Arabica L. var Castillo. The results of this study suggest that future studies could be conducted to investigate the impact capacity of pneumatic air-jet nozzles on coffee fruit excitation in terms of vibrational measurements.