Design and optimisation of seed-metering plate of air-suction vegetable seed-metering device based on DEM-CFD

The common problem of missed seeding during high-frequency sowing with air-suction seed-metering devices was investigated. A device was optimised and fitted with an auxiliary seed-supporting mechanism using pelletised Chinese flowering cabbage seeds as a typical example. Seed-metering was examined at the micro scale and the critical points were drag force and seed velocity. Suction hole capture duration, migration resistance and collision limit speed were defined as performance evaluation indices for seed filling and seed cleaning, respectively. Modelling by coupled discrete element method and computational fluid dynamics was adopted to simulate the gas–solid two-phase working process of the air-suction seed-metering device. The relationship between seed velocity and drag force was analysed to determine the characteristics of seed flow as well as airflow. At the macro scale, the evaluation indexes of filling and cleaning performance were defined, and experiments designed using quadratic orthogonal rotation combination were performed with maximum single seed rate as the final optimisation goal. The optimal parameter combination for the seed-metering plate was a seed spoon thickness of 1.2 mm, a spoon arc length of 3.2 mm, and a seed cleaning knife inclination of 61.2°. Bench comparison tests were applied to compare optimised seed-metering plate with the original seed-metering plate and the other two control groups at different operating speeds. Results showed that the optimised seed-metering plate had a seedless rate of 1.24%, which was lower than 4.26% obtained by the non-optimised seed-metering plate, indicating that the optimise device had excellent performance.