玉米籽粒收获机贯流风-筛清选装置工作机理及参数优化

Whereas corn threshed directly in the process of harvesting is as industry material or forage, corn threshing harvester has been increasingly popular. Air and screen cleaning device is key part of corn threshing harvester.Part of corn is broken up seriously when moisture cotent of corn is over 30 percent. So the performance of the cleaning device gets worse and loss of corn particles is increased. Work mechanisms and parameters optimization of air and screen cleaning device for corn threshed components would be studied in detail. And systemic method to study microcosmic touched relationships such as physical mechanics characteristics of agricultural erose and bigger and high wet particles would be formed. Air-particle moving models would be founded through theory research. The screening theory would be improved. CFD-DEM numerical simulation and verified experimental study would be combined to obtain air and corn threshed components moving laws then make work mechanisms of the cleaning device known. Experimental study connected with numerical simulation study based on CFD-DEM would be done to obtain the affect of factors on objective indexes, in which high cleaning rate and low loss rate of corn and low airflow pressure drop of the cleaning device would be objective indexes,and in which factors include the structural and moving parameters of the cleaning device and corn characteristics. Genetic algorithm would be introduced to optimize parameters.And key techniques of air-and-screen device would be improved and confirmed through field test. The performance and reliability of the whole harvester would be improved through above studies, which would boost the development of harvest techniques.

玉米收获时直接脱粒用作工业原料或饲料，使玉米籽粒收获机有广泛的应用前景，贯流风-筛清选装置是玉米籽粒收获机的核心装置，由于秋季收获时玉米的含水率达到30%以上，部分籽粒破碎严重，使风筛清选装置的籽粒损失增加。本项目通过理论分析建立清选装置内气固两相运动模型，在此基础上完善风筛清选筛孔处颗粒透筛理论；形成农业不规则形状大粒高湿散粒体物理力学特性参数研究的系统方法；运用有限元与离散元相耦合数值模拟与试验研究相结合，获得风筛清选装置内气固两相流（气流和不规则形状玉米粒、玉米芯、玉米秆等）的运动规律，揭示风筛清选装置的工作机理；并获得风筛清选装置的参数和玉米脱出物的特性对清选装置性能指标的影响规律，通过遗传算法进行参数优化，并进行田间试验验证，设计高效玉米脱出物风筛清选装置。通过对玉米脱出物贯流风-筛清选装置进行深入系统的研究，对提高整机性能和可靠性有重要的现实意义，并推进收获技术发展。

玉米收获时直接脱粒用作工业原料或饲料，使玉米籽粒收获机有广泛的应用前景，贯流风-筛清选装置是玉米籽粒收获机的核心装置，由于秋季收获时玉米的含水率一般为30%左右，籽粒破碎严重，使得经风筛清选后的籽粒损失增加。本项目创新设计了颗粒碰撞恢复系数测试平台，构建出基于颗粒与壁面碰撞、基于三维速度和形变的无约束颗粒间碰撞恢复系数计算的理论模型，结合高速摄像试验获得了颗粒碰撞恢复系数随颗粒碰撞位置、碰撞速度和角度等的变化规律，利用离散元DEM与物理试验相结合的方式实现对颗粒群滚动摩擦因数的判定，揭示了颗粒碰撞恢复系数和滚动摩擦因数的产生机理，为玉米籽粒的离散元仿真研究奠定了基础，并形成了农业不规则形状大粒高湿散粒体物理力学特性参数研究的系统方法；通过理论分析建立清选装置内气固两相运动模型，采用CFD-DEM耦合方法，对变风场条件下不同形状玉米籽粒透筛过程进行仿真研究，得到颗粒在整个筛面上的透筛规律，完善风筛清选筛孔处颗粒透筛理论，获得风筛清选装置内气固两相流（气流和不规则形状玉米粒、玉米芯、玉米秆等）的运动规律，揭示了风筛清选装置的工作机理；通过多因素试验研究确定了清选装置的结构参数和运行参数对其性能影响的规律；基于传统的平面往复振动筛、曲柄摇杆与平面四杆机构工作原理，创新设计出多自由度玉米清选振动筛驱动机构；基于玉米脱出物的物理特性及其在清选装置内的运动规律，创新设计了正弦曲线编织筛体、阶梯式筛体、贝壳-圆孔组合式筛体，并进行试验验证，提高了玉米脱出物风筛清选装置的性能。通过对玉米脱出物贯流风-筛清选装置进行系统性的深入研究，对提高整机性能和可靠性有重要的现实意义，并推进收获技术发展。