Study on the flow field characteristics of the air-suction jujube harvester pipeline based on magnetohydrodynamic airflow control

This study aimed to address the issue of suction force attenuation in the air-suction jujube (red date) harvester due to pipeline pressure loss. The active flow control method based on magnetohydrodynamics was used to optimize the pipeline flow field and reduce pressure loss. Through multiphysics field coupling theory modeling and numerical simulation, the regulatory effects of different electromagnetic field parameters on the pipeline flow field were characterized. An experimental platform was established to verify that the optimized electrode tip density, electrode voltage, and magnetic induction intensity could significantly increase the outflow gas velocity, pressure difference, and harvesting efficiency of the pipeline. The results showed that when the voltage increased from 50 to 80 kV, the pipeline outlet velocity increased from 27.90 to 30.65 m/s, showing a significant marginal decreasing characteristic. For every 0.1 T increase in magnetic induction intensity, the terminal velocity increased by an average of 1.45 m/s, and the secondary coupling effect of Lorentz force gradually became more significant with the increase of the magnetic field intensity. When the air flow velocity increased from 15 to 30 m/s, the nonlinear characteristic of the velocity gain was prominent. When the tip density was 5.208 units/cm², the electric field voltage was 80 kV, the magnetic induction intensity was 0.203 T, the average pipeline outlet velocity reached 9.917 m/s (an increase of 7.9% compared to the benchmark), the average inlet and outlet pressure difference increased to 253 Pa (an increase of 7.7%), the average red date harvesting efficiency reached 3.037 kg/min (an increase of 7.3%), and the fruit damage rate was controlled at around 0.5%. This research provides theoretical support for optimizing air-suction jujube harvesting equipment, and shows the potential application of magnetic fluid airflow control technology in agricultural machinery.