变径变间距组合式螺旋板齿脱粒装置动态脱粒机理及其低损伤脱粒特性研究

Aimed at the problems that the extruding and rubbing seed corn threshers faced in operation such as the high chop rate of corncob and high crushing rate of grains, and also the poor adaptability problems, a self-developed product--the combined type of spiral bar tooth maize seed thresher with variable radius and space was taken as the object of study in this program, the model of maize seed threshing based on DEM was built up after the research about the physical and mechanical characteristics of each part of maize seed as well as their interactions, the dynamic process of threshing and the motion trails of maize seed and maize cob were analyzed when the combined type of spiral bar tooth maize seed thresher with variable radius and space was used, so as to explore the dynamic threshing mechanism of this thresher. The damage mechanism by using this thresher was studied based on DEM, quadratic regression orthogonal rotation design under the conditions of different structures and motion parameters; threshing damage monitoring system and quantitative evaluation indicator system on damage degree were established and compared with germination test of seeds to explore the low damage rate characteristics about the combined type of spiral bar tooth maize seed thresher with variable radius and space. The main working performance indicators were regarded as the objectives to optimize the working parameters of this thresher based on response surface methodology (RSM) and multi-objective genetic algorithms (MOGA). The optimized thresher was verified in the actual production, in the hope of meeting the requirements of low damage rate but excellent threshing performance for maize seed threshing by extruding and rubbing in the industry of seed production.

针对挤搓式玉米种子脱粒机作业过程中存在的碎芯多、籽粒破碎率高、适应性差等难题，项目以自主研发的变径变间距组合式螺旋板齿脱粒装置为研究对象，在对玉米种子果穗各组成部分物理机械特性及交互特性的研究基础上，构建基于DEM的果穗脱粒模型，分析果穗颗粒群在变径变间距组合式螺旋板齿滚筒工作状态下的动态脱粒过程和籽粒、果穗芯运动轨迹，探明脱粒装置动态脱粒机理。基于DEM和二次回归正交旋转组合设计进行不同结构、运动参数脱粒装置对籽粒的损伤机理研究；建立籽粒脱粒损伤检测系统和损伤程度定量评价指标体系，与种子发芽试验相对照，探明变径变间距组合式螺旋板齿低损伤脱粒特性。以脱粒装置主要工作性能指标为目标，基于响应曲面法、多目标遗传算法对脱粒装置工作参数进行优化；优化后的脱粒装置通过在实际生产中验证，以期满足制种行业对挤搓式玉米种子脱粒机低损伤、高脱净的脱粒性能要求。

脱粒是种子玉米收获和加工的关键环节之一，其性能决定了种子玉米的破碎与损伤程度。种子玉米破损后活力降低，影响种子的发芽和生长。因此，降低种子玉米脱粒损伤成为机械脱粒研究的主要问题。针对挤搓式玉米种子脱粒机作业过程中存在的碎芯多、籽粒破碎率高、适应性差等难题，本项目在进行种子玉米籽粒、果穗芯生物力学特性的技术上，采用有限元、仿真和试验分析等研究方法，对种子玉米籽粒机械损伤机理进行了研究；以种子玉米生物力学特性为理论依据，结合自主研发的变径变间距组合式螺旋板齿脱粒装置，开展了变径变间距组合式螺旋板齿脱粒装置动态脱粒机理揭示及其结构优化设计，对变径变间距玉米种子脱粒试验台工作参数进行优化与试验研究。. 对种子玉米籽粒开展了剪切、压缩试验，通过静态加载力学特性试验研究了种子玉米含水率和籽粒放置方式对籽粒剪切性能的影响规律，以及种子玉米含水率和籽粒放置方式对籽粒压缩性能影响规律。对玉米果穗芯进行了压缩、弯曲试验，得到在相同含水率下，种子玉米果穗芯压碎、弯曲最小破裂载荷平均值皆随着果穗芯轴径的增加而增大；当果穗芯轴径相同时，其含水率越大，对应压缩、弯曲最小破裂载荷平均值越小。应用图像处理技术生成种子玉米籽粒各部分三维实体模型，在ANSYS中对玉米籽粒不同部位的三维模型添加试验获取的不同的弹性模量和泊松比后生成有限元模型，得到种子玉米籽粒低损伤最佳施力部位与施力方式。基于二次回归正交旋转组合设计进行不同结构、运动参数脱粒装置对籽粒的损伤机理研究，对脱粒物料损伤程度定量进行评价，探明变径变间距组合式螺旋板齿低损伤脱粒特性。以脱粒装置主要工作性能指标为目标，基于响应曲面法、多目标遗传算法对脱粒装置工作参数进行优化；优化后的脱粒装置通过在实际生产中验证，以期满足制种行业对挤搓式玉米种子脱粒机低损伤、高脱净的脱粒性能要求。