Design and test of a precision air-suction maize seed-metering device for plot planting based on CFD-DEM coupling

• A precision maize seed-metering device featuring V-shaped guide grooves; • Determination of suction hole shape incorporating the coupling information of gas–solid two-phase flow; • Elucidation of the basic structure and working principle; • Construction of optimal working parameters by regression analysis. To address the problem of declining seed filling performance caused by low seed chamber capacity, low seed layer height, and decreasing seed quantity with the operation process of maize plot planting, this paper developed an air-suction precision seed-metering device for maize plot planting with a V-shaped guide groove. Firstly, the mechanical model of the seed movement relative to the seed-metering disc during the seed filling process was established by combining with the particle flow guidance principles, and the configuration of the guide groove that guides the seed to complete the particle adsorption in the optimal path during the dynamic seed filling process was determined according to the seed migration trajectory. Then, based on the CFD-DEM gas–solid two-phase flow coupling simulation method and multi-scale fusion, using Ansys Rocky and Fluent combined with a high-speed camera, the effects of the V-shaped guide groove on the flowability and dispersion of the low-capacity seed population were compared and analysed with other guide groove structures. Furthermore, the adsorption process and force variation of the maize particles were simulated, and the local effects of the airflow field of the four structural suction holes were analysed, and it was determined that the trapezoidal structural form (Structure II) had the best adsorption performance. Finally, the optimal working parameters and optimal seed filling performance of the seed-metering device were analysed by using the single-factor test and Box-Behnken orthogonal test. The results showed that with a cleaning distance of 4.10 mm, working negative pressure of 2.92 kPa, and seeding rotation speed of 17.21 rpm, the seed-metering device had the optimal filling performance, with its qualification index of 98.74 %, multiple index of 1.03 %, and miss index of 0.23 %. Validation tests under identical parameters yielded a qualification index of 98.94 %, multiple index of 0.93 %, and miss index of 0.13 %, consistent with optimisation results. Multi-variety compatibility performance test showed that the qualification index was no less than 96.40 %, the multiple index did not exceed 3.60 %, and no miss-suction occurred, surpassing national standard values and meeting agronomic requirements for maize plot planting.