关键词: 黄精, 气吸式排种器, 离散元法, 流体力学法, EDEM-FLUENT耦合

Abstract: The efficiency of manually sowing Polygonatum sibiricum seeds is low and the cost is high, besides the existing Polygonatum seeders mostly use mechanical seeders, resulting in obvious seed jamming and a high rate of seed damage. In response to the above issues, an air-suction precision seeding apparatus has been designed with strong universality for different sizes of Polygonatum seeds and meets the requirements of dense planting agronomy. Firstly, the planting technology and physical characteristics of Polygonatum seeds were analyzed, and it was found that Polygonatum seeds were small and medium-sized seeds with 1 000-grain weight of 35.60 g, sphericity of 89.95% and equivalent particle size of 3.57 mm. Secondly, the overall structure and working principle of the seeding apparatus were explained, and the working process of the seederwas divided into three areas: seed filling area, seed carrying area, and seed dropping area. Thirdly, according to the agronomic requirements of Polygonatum sibiricum seeds, the shape structure and size parameters of the main components of the seed metering device were designed. Finally, the Discrete Element Method (DEM) was used to analyze the seed filling process of Polygonatum sibiricum, and solved the motion law of the seed without negative pressure, the Computational Fluid Dynamics (CFD) method was used to analyze the internal flow field of the metering device, and solved the pressure and flow rate of flow field at the negative pressure chamber, the EDEM-FLUENT coupling was used to analyze the seeding performance of the seeding apparatus, solved the seed movement law under negative pressure, and analyzed the filling performance, carrying performance and throwing performance of the seed metering device. The simulation results indicate that when the speed of seed discharging disk is 30 r/min, the negative pressure of pneumatic tube is 3.5 kPa, the qualified rate is 90.5%, the reseeding rate is 6%, the leakage rate is 3.5%, the performance of seed discharging is good.

Key words: Polygonatum, airsuction metering device, discrete element method, CFD, EDEM-FLUENT coupling