Simulation and Optimization of an Air-Suction Drum-Type Seeding Machine Using DEM-CFD Coupling

Achieving high sowing precision for small and irregularly shaped seeds remains a significant challenge in air-suction plug-tray seeding systems due to frequent seed slipping and detachment during the seed-picking and conveying processes. To address this issue, a novel seed cap incorporating a seed-carrying plate structure was developed. A DEM-CFD gas–solid coupling model of the seed-metering device was established for metering chili pepper seeds. With suction (negative) pressure, seed-carrying plate height, and suction-hole diameter as affecting factors, simulations with a quadratic orthogonal rotational combination were conducted. Response surface methodology (RSM) was employed for multi-objective parameter optimization, followed by comparative bench test verification. The results indicate that the interaction between suction pressure and suction-hole diameter had a highly significant effect on the multiple-filling rate. The optimal combination of working parameters was determined as a suction pressure of 25.5 kPa, a seed-carrying plate height of 0.2 mm, and a suction-hole diameter of 0.4 mm. Experiments with the seed-metering machine demonstrated that under these optimal parameters, the single-seed qualification rate reached 95.09%, the miss-seeding rate was 3.06%, and the re-seeding rate was 1.85%. Compared to the conventional seed cap without a seed-carrying plate, the single-seed qualification rate increased by 4.49%, while the miss-seeding and re-seeding rates decreased by 2.06% and 2.43%, respectively. The seed-carrying plate structure effectively reduced the dependence of the seed-metering device on high suction pressure, providing a technical reference for the research and development of precision plug-tray seeding of irregular seeds.