水稻多吸孔窝眼排种器种群低损精量分离机理研究

Rice direct seed-metering devices are mostly not good in the precise separation of seed population, and the rice seeds are easily damaged during the seed-metering process, resulting in decreased of fine and small-amount seeding performance, which become a difficult problem to be solved urgently in the development of mechanized hill-drop drilling technology of hybrid rice. Seed inside-filling method may enhance the seed population fluidity and improve the filling performance of seed-metering device, which are beneficial to the precise separation of seed population. In order to lower the damage of rice seeds and realize precise separation of seed population, an innovative inside-filling pneumatic precision seed-metering means with multi-suction holes-socket structure, which is a conical socket with three suction holes uniformly distributed on the bottom of the socket, is proposed in this project, The low damage and precise separation mechanism of the structure during the separation of seed population will be investigated subsequently. Firstly, the stochastic process of the seed-metering process will be investigated using granular mechanics analysis, dynamics and kinematics analysis, and stochastic process theory. Then stochastic mathematical models, including velocity, displacement, and forces of the seed during seed population separation process will be constructed, which combined EDEM simulation of seed-metering process and high-speed camera analysis of bench test together, so as to clear the seed filling process of inside-filling socket structure and the movement law of seed population. Meanwhile, the follow-up protection characteristics of the circulation movement of seed population and its influencing essential factors will be verified. Secondly, the fluid-solid coupling numerical simulation method DEM-CFD will be employed to study the whole precise separation process of seed population, which helps to uncover the change law of forces on the seeds adsorbed in the socket with its spatial position. Moreover, the effect of friction descending and drag reduction on the adsorbed seed by the follow-up protection of the circulation movement of seed population during the separation process will be investigated in detail. And the adsorption law of multi-suction holes to rice seeds will be cleared subsequently, so as to clarify the low damage and precise separation mechanism of rice seed-metering device with multi-suction holes-socket structure. Finally, the comparative test of the low damage and precise separation performance of seed population will be carried out between the multi-suction holes-socket structure and the multi-suction holes structure without socket to verify the theoretical analysis and simulation. The results of this project will not only propose an innovative low damage and precision seed-metering technology of inside-filling pneumatic type for rice seed, but also provide the theoretical foundation and technical support to realize mechanized fine and small-amount hill-drop drilling of rice.

传统水稻直播排种器排种过程中因种群精量分离效果不佳、种子易破损，导致精少量排种性能下降，成为杂交稻机械化穴直播技术发展亟待解决的难题。内充种方式可增强排种器种群流动性，提高充种性能，有利于种群精量分离。本项目拟采用一种多吸孔窝眼结构的内充气力式精量排种方法，实现水稻种群的低损精量分离。通过构建种群分离过程中稻种受载、速度、位移等变量的随机数学模型，结合EDEM仿真与高速摄像技术，解析内充窝眼的稻种充填过程和种群的运移规律，明确环流种群的随动护种特性及其影响要素；基于DEM-CFD流固耦合数值模拟方法，研究种群分离过程中窝眼内被吸附稻种的受载规律，探明环流种群的随动护种对被吸附稻种在分离过程中的降摩减阻作用，明晰近距多孔气流对稻种的吸附规律，揭示多吸孔窝眼排种器的种群低损精量分离机理。本项目研究拟提出一种新型内充气力式水稻精量排种技术，为实现水稻精少量穴直播排种提供理论依据与技术支持。

本项目针对传统水稻直播排种器排种过程中因种群精量分离效果不佳、种子易破损，导致精少量排种性能下降的问题，开展多吸孔窝眼结构水稻内充气吸式排种器的种群精量分离研究：应用现有或搭建散粒体物料特性测试仪器测试研究短圆、中长、细长三个典型尺寸稻种的基本物料特性及与排种机构的摩擦特性；运用动力学、运动学、散体力学及弹性碰撞等理论，构建稻种吸附力学模型，阐明内充气吸式排种方法对提高型孔充种性能的助力作用，明确排种器正常排种时所需吸种负压；确定排种器圆台状窝眼的关键结构参数，窝眼入口直径取17.0mm可有效确保充种性能；建立相邻吸孔中心距与稻种尺寸和吸种直径的数学关系式，取吸孔中心距为4.3mm可提高吸种合格指数；运用离散元EDEM仿真软件，构建稻种仿真颗粒模型，探明影响排种器仿真排种效果的接触参数为稻种颗粒间静摩擦系数与滚动摩擦系数，并对其进行标定，建立一种稻种离散元颗粒模型接触参数快速标定方法；进行排种器排种过程的数值模拟，明确内充气吸式排种方法种群运动达到稳定的时刻；明晰充种区种群的种层划分，并阐明充种区种群的运移规律；对比有无窝眼结构的吸附层稻种的迁移状态，揭示内充窝眼结构对被吸附稻种提供稳定安全迁移空间的作用，利于吸孔从种群中精量吸附和分离稻种；明确吸孔直径对吸种性能无显著影响，阐明吸孔直径对不同球度稻种具有较好的适应性，优化吸孔直径为1.5mm；明确降低进种口高度，减少充种区种子量，有助于降低种群分离过程中被吸附稻种所受的种群阻力；明确排种器适宜的吸种工况组合，窝眼滚筒转速为17.14r/min，气室真空度为1.1kPa，进种口高度为25mm；对比研究平板导种与叶轮导种方式，探明平板导种方式的优势；以精简排种机构为目标，提出一种充种口与投种口分开但相通的腔道式穴播排种方法，构建排种器型孔充种过程运动学与动力学模型，明确较优型孔参数组合为型孔个数20，型孔长度10.6mm，型孔宽度7.6mm，型孔倾角0°；提出一种型孔轮式排种器滑片护种机构，促进排种装置护种方法发展；研发试验示范播量可调水稻精量穴播机。项目研究提供了新型水稻精量排种技术，寻求水稻多品种可变精量排种技术实现途径，提高水稻种植机械化水平。