油菜气送式集排器种子流均匀分配路径解析及控制策略

Air-assisted centralized metering device is an important development direction of metering device with high efficiency, precision seeding, and simplified structure. Seed flow distribution uniformity was the core part of air-assisted centralized seed-metering device which can sow several rows synchronously for rapeseed. As the complex and extraordinary random of seed flow, the distribution routing analysis and control method of seed flow was studied for the distribution system of air-assisted centralized metering device in this project. Firstly, the airflow field distribution, seed migration trajectory, and seed motion characteristics were demonstrated and the interaction mechanism between airflow field and seed flow was revealed using the Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) coupling approach. Secondly, the regularity and randomness of seed migration trajectory, distribution routing, and seed dropping were analyzed. The mathematical models of seed flow distribution and seed dropping were established. The intrinsic relationship between the migration characteristics of seed flow, the distribution path and seed dropping was proved, and the seed distribution and dropping regular patterns of seed flow in the airflow field were proposed. Thirdly, the effects of structural and working parameters on airflow distribution, distribution routing, and seed dropping were investigated for clarifying the control method of seed flow distribution and dropping. This research provides theoretical and application basis for designing the precision seeder for rapeseed by revealing the mechanism of the distribution of the seed flow.

气送式集排器是实现油菜高效精量排种并简化播种机结构的重要途径,种子流均匀有序分配是集中排种的关键环节。本项目针对种子流分配过程随机性强和轨迹不可控的问题，以油菜气送式集排器的分配系统为研究对象，开展油菜种子流分配路径解析和控制策略的研究。应用CFD-DEM耦合方法建立正压气流与种子间相互作用的气固两相流模型，分析分配系统的气流场分布、种子流迁移轨迹与种子运动特性，阐明气流场对种子流迁移特性的影响机理；解析种子流轨迹、分配路径和种子落点的规律性和随机性，建立种子流分配和落点分布均匀性数学模型，探明迁移特征与分配路径和种子落点的关系，揭示气流作用下种子流分配路径和种子落点的规律；分析分配系统结构和工作参数对气流场分布、分配路径和种子落点的影响，明确分配系统气流场分布对种子流均匀分配作用机制。结合多目标优化方法，提出种子流均匀分配的控制策略，为研制高效高精度油菜精量播种机提供理论支撑和应用基础。

播种机械化率低是油菜实现全程机械化的薄弱环节，成为制约油菜产业发展的瓶颈问题，研发轻简型联合直播机是提高播种机械化率低的重要途径。气送式集排器是适应油菜播种的典型排种器，具有播种行数多、幅宽大、作业速度高等优点。本项目针对油菜气送式集中排种器种子流分配过程随机性强和轨迹不可控的问题，应用CFD-DEM耦合仿真、高速摄像和台架试验等方法，研究气流场分布、油菜种子迁移特性和分配路径，揭示了种子流在分配系统中均匀分配路径的形成机制。. 构建了气送式集排器分配系统种子流-气流场-分配系统壁面之间的耦合模型，应用随机理论构建了分配过程模型，明确影响分配均匀性的关键因素，旋腔径高比为2.0时气流速度和压力的微观过渡更好，种子颗粒碰撞频率较低，提高了种子颗粒停留时间一致性；流线型分流和120°锥盖的气流平稳，导种效果较优，气流速度20~24 m s-1的分配均匀性变异系数低于5%。. 明确了管道结构影响流场分布与种子落点的作用机制，波纹输送管扰动气流，增强了对种子的扰动进而提高种子与输送管壁面、种子与种子之间的碰撞频率，提高了种子颗粒在管道中的分布均匀性；通过数值仿真与高速摄像获取了种子在导种管的运移轨迹，探明了导种管变形降低了出口气流压强一致性；构建了分配均匀性与气流压强的数学模型，确定分配均匀性变异系数与气流压强一致性呈正相关。. 通过DEM仿真与高速摄像结合探明了倾斜与振动激励影响供种性能进而影响分配均匀性的作用机制，提出了通过稳定供种、优化分配装置结构与工作参数与降低导种管碰撞次数以提高排种均匀性的调控方法。项目研究成果阐明了油菜气送式集排器种子流分配路径的形成机制，揭示了种子流、气流场与壁面间的互作机理，研发了一种油菜气送式集排器分配系统，创制了油菜气送式联合播种机，形成了轻简化、精量化、高效化的油菜播种理论与技术。