气流扰动下种子群体状态对水稻精量排种器充种性能的作用机理研究

Rice direct seeding technology has developed rapidly in recent years. However, the pneumatic type precision seeding is the development direction. As the seeds movement resistance has a significant influence on the seed filling performance, pneumatic metering device performs poor when sowing rice which has bad liquidity and high movement resistance. Reasonable state of seeds movement can reduce movement resistance, thus improve the seed filling performance. Existing research of pneumatic metering device focused on structure parameters, working parameters and physical characteristics of seed. However, study on the influence of seeds movement state on performance of seed metering device was little and need to go further, which didn’t develop quantitative models. To solve the problem, an attempt of this project will be made to reveal the mechanism of the influence of seeds movement state under air disturbance on filling performance of precision metering device for rice, based on a seed metering device under a new method that improves seeds movement state through air disturbance. The project will study the interaction among state of seeds movement, airflow field and metering device via gas-solid coupling simulation and bench testing combined high speed photograph technology, the formation mechanism of state of seeds movement under air disturbance will be revealed and the dynamical model of seed capturing and transporting from seeds pile will be developed. Finally, the relationship between seeds movement state and seed filling performance will be qualified, and the reasonable state of seeds movement will be determined. The research results of the project will provide and perfect the theory basis for design and optimization of precision seed metering device for rice, so as to improve the performance of rice planting equipment and promote the development of rice direct seeding technology.

水稻精量穴直播技术近几年发展迅速，其中气力式精量播种是水稻高效直播作业的发展方向。气力式排种器充种性能受种群移动阻力影响较大，对于水稻等流动性差的种子充种效果不佳。合理的种群状态可有效降低种群移动阻力，提高充种性能，而现有气力式排种器研究主要关注排种器结构、工作参数及种子特性对充种性能的影响，针对种子群体状态与充种性能作用机理的研究尚不充分，缺乏明确的量化结果。本项目以水稻种子群体状态与充种性能的作用关系为研究对象，提出利用气流扰动改善种子群体状态的新思路，基于设计的气流扰动式精量排种器，借助气固耦合模拟、台架试验及高速摄像技术手段，研究种子群体、气流场和排种元件之间的相互作用，探明气流扰动作用下种子群体状态的形成机理，建立扰种式气流结构下种子群体定量分离过程的动力学模型，量化种子群体状态对充种性能的影响，明确合理的种子群体状态特征，为水稻精量排种器设计与优化提供理论依据，研究意义重大。

杂交稻精量播种一直是精量播种研究一大难题，主要是由于杂交稻种子细长、不规则，且表面较为粗糙，种子从种群中分离的阻力较大。项目针对杂交稻精量播种中种子移动阻力大、气流结构不合理的关键问题，提出利用气流扰动改善种子群体状态的新思路，在气流扰动作用下种子群体呈流态化，充种孔在种群内部依然可以保持较高的吸附力，同时弱化了种子间的相互作用，进而降低移动阻力。项目基于前期研发的气流扰动式精量排种器，对气流扰动作用下种子群体状态的形成机理以及种子群体状态对充种性能的影响展开研究，研制了一套种子散粒体参数测试装置，测量了Y两优1号水稻种子各项物理力学参数及水稻种子散粒体参数；通过蓝光三维扫描获取了种子的外形点云数据并建立三维模型，模型各项参数与实测数据平均值误差均在4.5%以内；利用EDEM及Fluent建立了较为准确的离散元模型和排种器内部流场模型，并通过研制的电驱控制物性实验装置对模型进行了标定；对排种器内部流场进行仿真分析，明确了排种器内部流场分布规律，并根据水稻精量排种要求对进气口、气室等关键结构参数进行了优化；基于构建的种子离散元模型及内部流场模型，开展排种器气固耦合模拟分析，并结合充种过程力学分析，明确了气流扰动下种子群体状态变化规律及其对充种性能的影响；基于理论分析与数值模拟结果，对排种器气流调节方式、腔室压力气流结构进行了改进和试制，针对不同种群状态、腔室压力、排种盘转速对1-2 mm的10个系列型孔进行了试验研究，确定了最优种群状态等各项参数，研究了气流参数与种子群体状态特征参数的相关性并建立相应数学模型。本项目研究完善了气力式排种器研究理论体系，为水稻精量直播排种器设计提供理论支撑和新思路、新方法，有效推动了我国水稻直播技术发展及应用。