基于粘弹塑性接触模型的红花渐进剪切-气力吸附高效低损采收机理研究

The safflower cropping area in Xinjiang Province has been the largest in our country. However, the industrialization and large-scale development of safflower has been significantly restricted by the disadvantages of current mechanized harvesting process including the inefficient, crush and falling of petal, and the broken rate of fruit. To achieve the high-performance and low-loss harvesting of petal, a late-model harvesting mechanism of petal need to be proposed and studied based the coupling of progressive shearing and pneumatic process. Based on the bonded-particle discrete element modeling and C language, the viscoelastic-plastic contact model, which was suitable to the contour and mechanical property of petal, will be established. The low-loss separation mechanism of petal is one of the most important impacts. To reveal the mechanism, the influences of parameters of bit tool on the fracture of petal are studied; following the mathematical model is established to indicate the relationship among the net recovery rate, damage percentage, bonding strength between the fruit and flower and parameters of bit tool. In addition, the efficient transportation mechanism of petal needs to be interpreted by the mathematical model. In this process, the effect of suction fan parameters on the transportation of petal is obtained, and the relation between net rate and parameters of airflow velocity, case body and piping is studied. Eventually, the high-performance and low-loss harvesting mechanism of petal is ultimate target need to be elaborated. Thus, the CFD-DEM coupling simulation method is employed to analysis influences of structural parameters on the movement of petal, and to obtain the relationship between the airflow and petal. Ultimately, the parameters are optimized and the prototype is trial-produced to test and proof the contact model through comparative analysis between the theory parameters and practical application. This study will lay the foundation for the safflower harvesting research in Xinjiang and provide reference for high-precision numerical analysis modeling of other crops.

红花是新疆特色经济作物，种植面积居全国首位，但目前机械化采收存在效率低、花丝破碎、掉落及果球损伤等问题，制约产业发展。因此，提出一种新型的花丝采收方法，通过渐进剪切与气力吸附相结合的方式实现花丝高效低损采收。基于离散元粘结颗粒模型及C语言，构建符合花丝外形及力学特性的花丝粘弹塑性接触模型；研究不同刀具参数对花丝断裂的影响，建立采净率、破碎率与花果分离力、刀具参数间的数学模型，揭示花丝低损分离机理；研究不同负压风机参数对花丝输送的影响，建立集净率与气流速度、箱体及管道结构参数间的数学模型，揭示花丝高效输送机理；通过CFD-DEM耦合仿真，分析机具结构和工作参数对花丝运动状态影响，探明气流-花丝间相互作用关系，揭示高效低损采收机理；优化机构参数并试制样机，开展试验研究，通过理论与实际分析的对比，检验、修正模型。研究成果将为新疆红花采收机具研究奠定基础，并为其他农业物料高精度数值分析提供参考。

目前红花采收机具的结构及工作参数不完善，仍存在采净率低，含杂率和破碎率高，从而不能有效指导采收机具优化。但构建红花三维形态模型，进行花丝高精度数值模拟，可以准确地揭示花丝高效低损采收机理，提升红花采收机具作业性能。为此，针对目前红花机械化采收效率低、花丝破碎、掉落及果球损伤等问题，本项目以“高效率、低损伤”红花采收的实现为目标，综合应用农学、数学和仿真模拟。结合三维数字化重建、气固耦合等技术，从不规则柔性体--花丝物理及力学特性入手，建立基于粘弹塑性接触结构从新构建红花丝高精度数值模拟模型，标定及校准花丝离散元仿真参数，分析渐进剪切-气力吸附红花采收原理；构建采收机具-花丝交互力学模型，并采用CFD-DEM耦合的方法模拟花丝剪切及输送过程，确定适宜的机具腔体结构及风机转速，阐明花丝高速渐进剪切分离机制，揭示红花高效低损采收机理，优化机具结构和工作参数；基于红花高效低损采收机理，开展采收机具结构及工作参数优化，并完成工作性能的台架及田间试验，通过单因素与多因素交互试验确定渐进刀具切割花丝时最佳刀具参数，提升了采收机具的作业性能。针对本项目研究的相关内容，在国内外发表科研论文5篇，其中EI收录2篇，中文核心期刊2篇，英文期刊1篇；申请相关国家专利9项，其中发明专利8项，授权发明专利7项、实用新型专利1项。研究成果为红花采收机具研发奠定了理论与技术基础，同时为其他农业物料高精度数值分析建模提供了参考。