集排离心式油菜精量排种器排种过程解析与种子流控制策略

Most of metering devices are sowing one row at one device, resulting in complicated structure of the multi-row seeder and inconsistent seeding amount among the rows. Centrifugal metering device is a multi-row metering device with simple construction, but here's difficult to be used for precision sowing small seeds, such as rapeseed. Moreover, the holes of the device is easy to be blocked. To solve above problems, an innovative centralized precision seed-metering technology applied centrifugal metering and multistage distribution was proposed .The project is intended to analysis the seed discharging process and explore the seed flow control strategy of the device for precision sowing rapeseed. Firstly, the stochastic process of the seed metering process will be investigated using theories of stochastic analysis, dynamics and kinematics analysis and reliability analysis. Then random process models, including the displacement, the velocity and the forces of the seed under centrifugal action will be constructed. Further more, the movement law of seeds during the series of sub-processes will be concluded. The optimization strategy will be proved up to enhance its reliability and stability according to a tenet that less series of sub-processes and shorter migration path of the seed. Secondly, mechanism of multistage distribution of seed flow and strategy of prevention blocking of holes of the device will be verified and investigated in detail of the broadened hole and the diverging branch-valve. Thirdly, technologies of the discrete element method simulation and high speed photograph will be employed to study the whole seed metering processes to extract the trajectory of the transporting seeds singly and orderly. Meanwhile, the solid-gas-fluid coupling characteristic about the transporting seeds and gas flow field produced by the centrifugal action will be inspected as well as to evaluate its affects on seed metering. As a further step, the structure of the device will be optimized with increased reliability and performance and sowing speed. The results of the project would promote the technology of centrifugal metering, enrich the design method and means of agricultural machine seed metering device and simplify the rapeseed planter as well as to increase the mechanization level of rapeseed.

针对传统油菜排种器属一器一行、结构复杂且各行一致性难以保证，现有离心式排种器均为非精量条播且因型孔易堵塞导致断条的缺陷，提出一种具有枝状阀式种子多阶“分-合”分流机构的集排离心式油菜精量排种技术与配套装置，开展排种过程的解析与种子流的有效控制策略和排种器结构优化研究。应用随机过程、可靠性设计和运动学与动力学理论，建立排种过程中油菜种子的位移、速度、受载等随机变量的随机过程模型；研究油菜种子排种过程的运移规律，优化并获取最短排种路径；探明采用扩大排种盘型孔孔径增加种子流以避免型孔堵塞，再利用枝状阀式多阶“分-合”分流机构导种的各行排量一致的均匀种子流的形成机制；应用EDEM仿真和高速摄像技术，模拟并提取排种过程中单粒连续种子流的运移轨迹，探明排种过程的固气流耦合特征；提供新型排种技术、简化油菜播种机结构，寻求高速播种排种技术的实现途径，促进油菜种植机械化水平的提高。

本项目针对传统油菜排种器属一器一行、结构复杂且各行一致性难以保证的问题，开展一器多行集排式油菜精量排种器的排种过程解析与种子流控制研究：应用物料特性测试仪及高速摄像技术研究油菜种子物理机械特性与排种机构的作用关系；结合运动学与动力学理论及随机过程理论，建立油菜集排离心锥桶式、集排旋转盘式、集排气送式排种器的种子迁移中的位移、速度、受载等随机变量的随机过程模型，得到种子迁移规律并阐明排种机理。运用EDEM仿真技术，探明油菜集排离心锥桶式排种器型孔堵塞临界值，并确定排种器的投种孔直径取3.8mm时性能较优；探寻种子流经由枝状阀式多阶混合均匀分流机制，基于可靠性设计，得到油菜籽在不同排种过程中种子运移规律并获取最短排种过程和最优的排种路径；解析离心集排器排种过程，提出了通过减小内锥筒容积缩减达到动态平衡时间的改进策略和基于螺旋供种装置的充种量稳定主动控制策略。运用EDEM-CFD气固耦合仿真探明排种过程中迁移的油菜种子（固态）、气流场（气态）的气固耦合特征，揭示排种器排种机理并优化装置结构参数，得到供种装置工作转速范围为10~30r/min，采用倾角为20°的锥柱状型孔时，供种性能较优；输种管道直径、长度和横纵管道长度比分别为42mm、1.0 m和2/3时，管道出口处种子速度、两相流相对速度和压强损失较小，排种性能较优。项目研究提供了新型集排技术、简化油菜播种机结构，寻求高速播种排种技术的实现途径，提高油菜种植机械化水平。