整秆式甘蔗联合收割机叶鞘剥离机理与关键技术研究

Sugarcane is the main sugar crop in China. At present, the sucrose cost in China is higher than that of world average. The main reason is that mechanization level for sugarcane production is too low. The technology of whole stalk sugarcane combine harvester accommodates current situation of the sugarcane production system in China. The high leaf-stripping impurity rate, however, is universal problem in these harvesters. It is difficult to strip the sugarcane leaf sheath for it bundles the stalk tightly like a tube and more pieces overlap each other. But, now the mechanism of sugarcane leaf sheath stripping in the process of the whole stalk harvesting is not clear. Study on mechanism of sugarcane leaf sheath stripping is closely related to its physical and mechanical characteristics and action mechanism of elastic dentation sugarcane leaf-stripping element which is the key technical problem in the research of sugarcane leaf-stripping technology. In this project, the fracture forms and the fundamental failure strength of leaf sheath, mechanism and key technology of sugarcane leaf sheath-stripping are studied based on the method of physical and mechanical performance experiments, physical and virtual prototyping experiments, theoretical modeling. The objective of this project is to design a new style elastic dentation-roller-type sugarcane leaf-stripping device for whole stalk sugarcane combine harvester. The research result of this project can provide a new theoretical method to study on leaf-stripping for high and crude stalk category crops.

甘蔗是我国主要的糖料作物。目前我国甘蔗生产机械化水平较低导致蔗糖成本高于世界平均水平。整秆联合收获工艺是适合我国甘蔗生产体系的机械化工艺，但普遍存在剥叶含杂率高的技术难题。甘蔗叶鞘呈管状紧实包裹茎秆且多片叶鞘相互重叠导致剥离困难是造成剥叶含杂率高的主要原因之一，而目前尚未研究清楚整秆剥叶过程中叶鞘的剥离机理。叶鞘剥离机理与叶鞘的物理力学特性、剥叶元件的作用机理等方面密切相关，是甘蔗剥叶技术研究中需要重点解决的关键技术。本项目采用基础力学试验、虚拟样机试验、物理样机试验和理论建模分析等方法深入研究甘蔗叶鞘的力学性能与破坏形式、弹性齿剥叶元件的作用机理和叶鞘剥离机理以及叶鞘剥离关键技术，研制出性能更优良的新型弹性齿滚筒式甘蔗整秆剥叶装置，为高粗茎秆类作物剥叶技术研究提供一种理论方法。

甘蔗叶鞘剥离技术难度大是影响整秆式甘蔗联合收割机收获甘蔗含杂率的主要因素之一，项目研究了弹性齿滚筒式甘蔗整秆剥叶装置的叶鞘剥离机理及剥叶关键技术，提高叶鞘的剥离效果，降低整机收获的含杂率。采用基础力学试验、虚拟样机试验、物理样机试验和理论建模等方法研究了三个方面的主要内容：.（1）甘蔗叶鞘物理力学性能以及甘蔗叶鞘破坏形式.（2）弹性齿剥叶元件作用过程和运动状态.（3）弹性齿作用力形式与叶鞘剥离力学模型.研究得出了叶鞘的基本破坏强度和破坏形式，确立了叶鞘剥离准则；提出了弹性齿剥叶元件件对叶鞘的破坏作用机理，建立了运动状态方程与动力学模型，为整秆式甘蔗联合收割机叶鞘剥离关键技术改进提供理论依据。.研究主要结论：.（1）处于同一节段的叶鞘纵向抗拉强度最大、剪切强度次之、横向抗拉强度最小。处于茎秆不同位置的叶鞘，接近稍部的力学强度较大，接近根部的力学强度较小，接近稍部的叶鞘是机械剥离需要重点解决的难题。叶鞘在纵向拉伸、横向拉伸和冲击剪切作用下破坏形式分别为维管束脆性断裂、薄壁组织撕裂和维管束剪切变形，其中，薄壁组织撕裂是叶鞘最容易实现的破坏方式。叶鞘剥离准则应同时满足：1）在垂直于叶鞘纤维方向的应力σ2不小于σ2max；2）轴向应力σ1不小于撕裂后的叶鞘与茎秆在轴向上的最大强度。.（2）弹性齿对叶鞘的作用分为接触甘蔗茎秆、撕裂叶鞘和撕扯叶鞘3个阶段。弹性齿与甘蔗茎秆接触后相对于甘蔗茎秆在x、y轴线速度差和上、下弹性齿的交错深度是影响叶鞘剥离效果主要的运动参数和结构参数。.（3）弹性齿接触甘蔗茎秆过程持续施加纵向、横向和切向打击力。弹性齿沿茎秆圆周滑动，横向打击力造成叶鞘沿纤维方向撕裂。弹性齿沿茎秆轴线滑动，纵向打击力对叶鞘产生推挤破坏。弹性齿在x和y方向对甘蔗茎秆打击力的最大值同时超过叶鞘的最大破坏力值，弹性齿在茎节连接处将叶鞘刮离茎秆，实现整体剥离。