Authors

Abstract

To provide fundamental data for the design and experimental evaluation of pneumatic precision seed metering devices for small-seed crops, the material characteristics of millet, broomcorn millet, and rapeseed were systematically investigated in this study. The moisture content, thousand-seed weight, density, principal dimensions, equivalent diameter, and angle of repose of the three seed types were determined through physical measurements. The Poisson’s ratios of millet, broomcorn millet, and rapeseed were measured using a universal testing machine and were found to be 0.27, 0.33, and 0.29, respectively. In addition, the static and dynamic friction coefficients between each seed type and acrylic, stainless steel, and resin surfaces were obtained. The elastic moduli of millet, broomcorn millet, and rapeseed were measured using a texture analyzer as 351.76, 589.14, and 133.37 MPa, respectively, which were closely related to seed density and structural characteristics. To further clarify the influence of seed–surface collision behavior on seed motion trajectories during the seed metering process, a high-speed imaging test system was established to determine the coefficients of restitution of seeds with moisture contents of 15%, 20%, and 25% after collision with different material surfaces. The results showed that the coefficient of restitution was significantly affected by seed moisture content and decreased markedly with increasing moisture content. Among the three seed types, the coefficient of restitution decreased in the order of broomcorn millet, millet, and rapeseed. For each seed type, the coefficient of restitution decreased sequentially for collisions with acrylic, stainless steel, resin, and the corresponding seed surface. These results provide important data support for the structural design and simulation analysis of pneumatic precision seed metering devices.

Abstract in Chinese

为给小籽粒气力式排种器的设计与试验提供数据支撑，本文选取谷子、糜子和油菜籽对其物料特性进行了系统研究。通过测量试验得到了三种种子的含水率、千粒重、密度、三轴尺寸、等效直径、自然休止角等具体参数数值。利用万能试验机得到三类种子的泊松比分别为0.27,0.33和0.29。得到了三类种子分别与亚克力板、不锈钢板和树脂板之间的动、静摩擦系数。使用质构仪得到三类种子的弹性模量分别为351.76MPa、589.14MPa和133.37MPa，这与种子的密度和构造有对应的关系。为分析种子与排种器接触过程中碰撞行为对其运动轨迹的影响，搭建了高速摄像测试系统，测定了15%、20%、25%不同含水率种子与不同材料接触后的碰撞恢复系数。结果表明：碰撞恢复系数与含水率有显著关系，随着含水率的增加，碰撞恢复系数迅速减小；糜子、谷子、油菜籽的碰撞恢复系数依次减小；每类种子与亚克力板、不锈钢板、树脂板、同类种子板之间的碰撞恢复系数依次减小。该研究可为小籽粒气吸式排种器的结构设计与仿真分析提供重要的数据支撑。