Numerical Study of Pneumatic Conveying of Rapeseed through a Pipe Bend by DEM-CFD

In the wide-width and high-speed operation of the rapeseed air-feeding planter, the air-feeding seed metering system adopts the top-down seed tube of different structural types in the production process, thus leading to significant differences in the discharge consistency and breakage rate of the respective row in the seeding process. Thus, the corrugated, hole-type, and ordinary round-tube seed tubes were taken as the research objects for this study, and virtual walls were introduced to compare and analyze the movement of seeds after collision with the seed tubes that had different wall structures. The effects of three types of seed tubes on the motion characteristics of seed particles were analyzed using DEM-CFD gas-solid coupling, and the simulation results were verified through bench experiments. The results indicated that when the inlet velocity was 16 m/s, and there was no material; the average error between the simulated value and the examined value of the airflow velocity at the same point of the vertical conveying pipe of the ordinary round-tube seed tube was 6.71%, thus verifying the feasibility of the simulation model built establishment of this study; when the inlet airflow velocity was 16 m/s and the seed particles were generated at the same per second, both the corrugated and hole-type seed tubes had a surge in airflow speed in the elbow part, and the highest airflow of the corrugated and hole-type pipes the velocities were 32.48 and 26.20 m/s, respectively. The corrugated and hole-type structure significantly affected the airflow field characteristics in the seed tube; the corrugated and hole-type seed tubes significantly improved the stable delivery of seeds, and the speed and force of the seeds were similar “sinusoidal fluctuation”, and the stagnation time of the seeds in the ordinary round-tube, corrugated, and hole-type seed tubes were 0.3, 0.38, and 0.48 s, respectively, and the seed velocities at the outlet were 5.18, 1.73, and 3.76 m/s, respectively. This study provides a reference for the optimization of the structure of the seed tube of the air-feeding seed metering system.