【作者】 付作立；

【导师】 方宪法； 王德成；

【作者基本信息】 中国农业大学 ， 农业机械化工程， 2014， 博士

【摘要】 为了有效地减少苜蓿收获环节的损失,提高草产品质量,论文基于苜蓿植株基本特性以及双圆盘式旋转割草机的特点,研发了适合我国苜蓿种植特点的倾置刀盘和异形割刀并存的双圆盘式旋转切割器,并研究了切割器周围的流场对苜蓿植株运动产生的影响。主要研究成果包括：(1)分析了苜蓿植株的结构特点、力学特性以及割刀与苜蓿植株的切割关系,研究了切割系统切割条件。从苜蓿植株茎秆和叶片的形态特点和微观结构入手,建立了苜蓿植株、茎秆和叶片的物理模型；对首蓿植株茎秆的力学特性进行整理和试验验证,总结出了苜蓿植株茎秆的基本力学特性参数；研究不同切割方式对切割阻力和能耗造成的影响,提出了削切是最佳切割方式；研究了苜蓿无支撑切割条件,即最低切割速度要求为30m/s,最佳取值在65-80m/s之间；模拟了相邻刀盘割刀实际重叠区域形成过程,提出了重叠区域宽度设计要求。(2)为了满足切割条件,论文在分析了双圆盘式旋转切割器结构的基础上,提出了异形割刀和倾置刀盘结合的结构设计方案。根据复数矢量理论探寻割刀扭角与刀盘倾角的最佳取值区域,根据平面向量理论讨论两者之间的相互作用关系,提出了异形割刀扭角和刀盘倾角关系的作用指标。切割器具体参数为：刀盘直径530mm,转速2170r/min,割刀伸出长度60mm,理论重叠区域宽度25mm,异形割刀扭转角度为8°,刀盘倾角范围0-8。。(3)为了分析气流对苜蓿植株产生的影响,论文利用计算流体力学软件(CFD)对切割器周围的流场进行模拟分析,结果表明：气流对苜蓿植株产生的流场力与植株重力在同一个数量级,对苜蓿植株的运动有较大影响。其中,滚筒周围流场对苜蓿植株的作用一方面体现在竖直方向的“升举作用”,另一方面体现在圆周方向的“弯曲作用”；异形割刀周围的流场对苜蓿植株的影响一方面是瞬时强动能,另一方面是稳定长时间的弱作用。并提出了在流场作用下的苜蓿植株运动模型,得出了苜蓿植株的运动状态和受力情况。滚筒周围区域压力场的模拟结果与经验公式计算结果数值相符。(4)进行了双圆盘式刈割压扁机切割系统田间试验。利用9GYZ-1.2型自走式苜蓿刈割压扁机对设计的切割系统和传统切割系统进行了对比试验,结果表明：设计的切割系统作业时的碎草率远低于传统切割系统,同时基于论文切割系统研发的9GYZ-1.2型自走式苜蓿刈割压扁机的各项性能指标均达到或优于国家标准要求。更多还原

【Abstract】 By2010, the cultivated area of alfalfa had been reached4,270,000hm2, but the level of mechanization was fairly low. Developing and manufactureing suitable Alfalfa harvesting machinery for China is necessary. The mower is the main equipment for harvesting, at present, the study on mower is forcused on its structure and the key working parts.such as dynamic analysis of cutting knife and so on. However, the flow field around mower as an important factor to affect the performance of the mower was always neglected. Based on the analyze of Alfalfa mechanical properties,the interaction between alfalfa and cutting tools,and the effect of flow field on the Alfalfa, The article developed a two-disc rotary mower with the special-shaped cutting knife and sloping cutting discs, The main results are as follows:(1) Inorder to desing suitable mower, the physical models of stem and leaf of Alfalfa were built by means of analyzing the morphological character and microstructure, meanwhile,, the apparent volume, surface area, area of contour, apparent density and specific weight were discussed by this model. And then, the mechanical characteristic parameters of alfalfa stem were obtained through experimental collecting. the cutting type impacted on resistance and energy loss in cutting was also discussed. Based on these research, a new cutting method named inclined cutting was proposed in this paper.In order to avoid recutting in working, the conditions meeting to this cutting method were determined, that is a linear velocity greater than30m/s of the cutting knife is needed and the best velocity value is between65m/s to80m/s.(2)The sloping cutting discs and the special-sharped cutting knife were designed to meet the inclined cutting methord. And the torsion angle β of special-shaped cutting knife and the tilt angle a of cutting discs were important parameters which would affect the working performant. Acording to the plural vector theory and the plane vector theory, the best value range of the torsion angle β and the tilt angle α,and the interaction betweenβand a were discussed. Finally, the parameters of the cutter of mower were determined, which were the diameter of the disc was530mm, the rotary speed of the cutters was2170r/min, the length of the cutting knife was60mm, the width of theoretical overlap area was25mm,.he torsion angle β of special-shaped cutting knife was8°,and the range of the tilt angle a of cutting discs was0-8°(3) In order to analyze the effect of cutter rotating airflow on alfalfa,computational fluid dynamics (CFD) was used to simulate the flow around the cutters, the results showed that, the flow had a great impact on the movement of the plants. Specifically, in the flow around the special-shaped cutting knife, the plant obtained the force upward in the bottom and the even load on the whole plant; in the flow around the drum, the plant was lifted along the drum axis derection and bended in the circumference of drum. The pressure field in the flow is expressed by static pressure, dynamic pressure and the total pressure. The range of the static pressure around the drum is-250～100Pa, the dynamic pressure is0-1300Pa and the total pressure is-250～1300Pa. Considering the impact of the flow around the special-shaped cutting knife and drum and optimizing the kinematics and statics model of the plants, analyzing the different motion state by adjusting the parameter in the model. Under the same condition, optimizing the motion model of the special-shaped cutting knife could support the designing of the knives.(4) A rotary mower equipted with designed cutter were used to test its working performance in the field. Comparing with common cutting knife, the rate of broken alfalfa of desigened cutting knife was much lower under the same conditong of victory. Based on this designed cutter, a new rotary mower named9GYZ-1.2machine was designed and manufactured, field testing showed that all indexes of this machine had reached the standard.更多还原