Development of a liquid-jet nozzle for fertilizer injection in paddy fields using CFD

Abstract

The current broadcasting method for chemical fertilizer applications for rice production causes significant nitrogen losses through volatilization. To minimize this problem, a liquid-jet nozzle was developed for injection of liquid fertilizer in paddy fields. With computational fluid dynamics (CFD), the liquid-jet nozzle was modelled to examine the mass flow rates and velocities as affected by the critical design parameters of the nozzle: fertilizer inlet diameter (df) and nozzle orifice diameter (do). The model was validated with tests, and the performance of the liquid-jet nozzle was evaluated through injecting Urea Ammonium Nitrate solution into a clay loam soil. Simulation results showed that flow velocities decreased and mass flow rates increased at larger do values in a non-linear fashion. Effects of df were less pronounced and depended on the values of do. The model results agreed well with the test results with relative errors between 0.4 and 13.3%. Considering the requirements of nitrogen application rates for rice (60–180 kg ha−1) and soil cutting depths (20–50 mm), the optimal design parameters for the liquid-jet nozzle were the combinations of (df, do): (1.0, 1.0 mm) for producing the highest nitrogen application rate, and (0.6, 0.8 mm) for having the highest ability in cutting soil. The liquid-jet nozzle, a non-traditional injection method, has high potential to become a cost-effective and low soil-disturbance practice for rice production.