CFD-DEM coupling-based analysis and parameter optimization of the collaborative seed delivery process in an air-suction soybean seed metering device with an auxiliary delivery mechanism

To address the problems of dispersed seed trajectories after detachment from the metering disc and unstable terminal release during operation, an air-suction soybean seed metering device equipped with an auxiliary seed delivery mechanism was investigated. A CFD–DEM coupling simulation model was established to analyze the seed motion states during suction-based carrying, detachment from the metering disc, receiving by the reversing wheel, and terminal release. The effects of different terminal seed delivery outlet positions on seed release stability were first compared. The results showed that, at Position I, the mean equivalent spacing on the seed delivery belt was 15.00 mm, the coefficient of variation of spacing was 5.15%, the qualified rate was 100.00%, and the mean lateral offset was 0.44 mm, indicating better terminal delivery stability. On this basis, response surface experiments were conducted using metering disc rotational speed, reversing wheel angular velocity, and negative pressure as experimental factors, while the qualified rate of equivalent seed spacing, miss-seeding rate, and multiple-seeding rate were used as performance indicators. The results showed that the qualified rate of seed spacing ranged from 76.27% to 96.55% under different parameter combinations, while the miss-seeding rate and multiple-seeding rate ranged from 2.27% to 18.64% and from 1.15% to 12.50%, respectively. Negative pressure had a pronounced effect on the qualified rate of seed spacing, and significant interaction effects were observed between metering disc rotational speed and reversing wheel angular velocity, as well as between metering disc rotational speed and negative pressure. The optimized parameter combination was a metering disc rotational speed of 31.58 r·min -1 , a reversing wheel angular velocity of 11.05 rad·s -1 , and a negative pressure of 4.14 kPa, with a predicted qualified rate of seed spacing of 95.20%. In the bench validation test, the parameters were adjusted to 32.05 r·min -1 , 10.91 rad·s -1 , and 4.00 kPa. The average qualified rate of seed spacing from five repeated tests was 94.30%, with a relative error of 0.95% compared with the predicted value. The results indicate that the established model can be used for matching and analyzing the collaborative operating parameters of an air-suction seed metering device and an auxiliary seed delivery mechanism.