基于颗粒力链引导机理的高速玉米精量排种器机械气力复合充种方法研究

With development of China's maize mass production，High speed and efficiency has become the development trend for corn precision planter, but the seed-filling performance of the pneumatic precision seed-metering device will decrease as sowing speed increase which will lead to a reduction of corn yield. It is difficult to improve the seed filling performance only by means of breaking granular force chain. Aiming at the problem, the traditional method was replaced by guidance of granular force chain, one method of seed-filling is proposed by which the function could be realized of mechanical guidance and pneumatic disturbance, and this method can effectively reduce the seeding absence due to the filling failure the high sowing speed. Characteristic parameter of granular force chain for seeds pile will be built to revel the directing mechanism of granular force chain formed by every part in the mechanical-pneumatic combined seed-filling system by virtue of numerical simulation and dynamic analysis. The degree of restraint that every factors of force chain control the seed into reasonable position of filling will be clarified, and the relationship will be quantified among characteristic parameter and seed-filling performance by experimental research and gas-solid coupling simulation. In addition, control strategy will be established which will contribute to improving stability of seed-filling system，and to optimizing the key parameter of mechanical structure. A mechanical-pneumatic combined seed-filling mechanism will be developed which will provide a basic theoretical model and technology in use for the development of agricultural equipment to the direction of high-speed and accuracy.

随着我国玉米规模化生产的发展，高速高效成为玉米精量播种机发展方向。但随着作业速度的提高，气力式排种器充种性能会显著下降易造成严重漏播，而单纯依靠破坏种群颗粒力链、提升充种性能的方法存在局限性。为此本课题提出一种机械趋导与气流干扰相结合的高速玉米精量排种器复合充种方法，采用颗粒力链引导代替传统力链破坏思路，缓解高速作业对充种过程的冲击，最大限度的降低因排种器充种失败造成的漏播，提高播种机高速作业单粒率。通过构建种群颗粒力链特征参数，结合数值模拟和动态仿真，揭示复合充种系统各工作环节引导种群颗粒力链形成的机理；通过试验研究与气固耦合模拟，明确力链各因素对种子进入合理充填状态的约束程度，量化力链特征参数与充种性能的相互关系；研究提升充种稳定性的控制策略，优化充种系统关键参数；研发一种适于高速气力玉米精量排种器的机械气力复合充种机构，为玉米精密播种机高速化、精准化提供基础理论支持和创新实用技术。

随着我国玉米规模化生产的发展，高速高效成为玉米精量播种机发展方向。但随着作业速度的提高，气力式排种器充种性能会显著下降易造成严重漏播。针对排种器高速作业时充种性能不佳导致排种质量下降的问题，本研究提出一种扰动与趋导相结合的辅助充种方法代替传统强制充种思路，采用主动驱导种群、减少局部种间接触的方法，以降低种子充填阻力，实现排种器高速条件下的充种率和单粒率的提升，并基于此设计了一种趋导辅助充种气吸式精量排种器。建立了玉米种子耦合模型，应用响应面优化法对玉米颗粒粘结模型的种间静摩擦系数和滚动摩擦系数两个关键参数进行标定。分析了排种器充种过程中阻力来源，阐述了排种盘导种槽辅助充种的工作原理，以及在充种过程各阶段提高种子充填率的设计思路；对导种槽外形曲线方程、斜面倾角进行了理论计算，确定了排种盘导种槽曲线的基本参数；基于确定性颗粒轨道模型，将压力梯度力算法引入排种器DEM-CFD气固两相流耦合分析。从宏观尺度、微观尺度对充种过程各阶段临界点进行划分，并确定了各阶段充种性能评价指标；以种子吸附稳定时间、种子移出阻力、型孔处局部空隙率为颗粒力链指标，进行了三因素二次旋转正交组合试验，对试验结果进行多元回归分析，采用多目标优化方法，确定充种系统关键参数对充种性能影响关系。对本研究所设计的排种器进行了前进速度为6~14km/h、工作压强为-4.5~-6kPa的双因素试验，分析了以上2个因素对排种器各指标的影响规律，确定了最佳的排种器工作参数；进行了排种器静止台架试验和室内振动环境模拟试验，将优化后的排种盘与原排种盘不同作业速度下进行对比，结果表明优化后的排种盘高速、振动条件下的充种性能有明显提升，作业速度为14km/h、随机振动主激励频率为9.5Hz、自功率谱密度峰值为0.428g2/Hz时，漏充率为1.26%，充种性能较为稳定。将所设计的排种器安装在气力式玉米免耕播种机上，进行3个工作速度的单因素重复试验，结果表明当作业速度为9.11km/h,粒距合格指数为95.48%，高速条件下充种性能较为稳定。