【作者】 张杰；

【导师】 张永；

【作者基本信息】 内蒙古农业大学 ， 农业电气化与自动化， 2023， 博士

【摘要】 内蒙古自治区拥有丰富的草资源,草资源收获打捆设备方便了松散草物料的运输与储存过程,成为了助力草产品商品化流通的重要设备。圆捆机卷捆过程中钢辊压缩力向草捆内部传递逐渐衰减,是影响圆捆机性能以及成型草捆径向密度分布特征的重要因素,随着相关理论的不断发展及研究方法的不断丰富,借助多种理论与实践手段相互结合、相互弥补的优势进一步研究卷压过程中草捆内部径向压力传递特征及草捆径向密度分布特征对推进圆捆机发展具有重要意义。本文在对内蒙古地区常见卷压对象紫花苜蓿物理力学特性系统研究基础上,采用理论分析、仿真研究与试验研究相结合的方式探究物料卷捆过程、草捆径向压力传递特征以及草捆径向密度分布特征,建立物料卷压模型表示物料压缩应力与成捆密度之间的关系,提出纠缠性高密度环形柱状壳体草捆外层结构假设,分析其形成条件。基于压溃理论中壳体类结构非圆度参数对其自身结构强度的破坏效果,设计螺旋线形成型仓圆捆机,从实际试验和仿真角度研究不同钢辊布局参数对草捆径向压力传递特征、草捆径向密度分布特征以及紫花苜蓿卷压过程的影响,揭示草捆径向密度分布特征形成机理,并对圆捆机成型仓钢辊布局结构进行优化。具体研究内容及结果如下:(1)对紫花苜蓿物理力学特性进行了研究,测定了紫花苜蓿的基本外形尺寸、含水率、体积密度、绝对密实度、孔隙率、静摩擦系数、滚动摩擦系数、碰撞恢复系数、堆积角与剪切模量等物理特性参数,为后续紫花苜蓿离散元模型建立及其卷压过程仿真参数设置提供基础数据。(2)对物料卷压过程进行理论分析和高速摄影,建立物料卷压力学模型和运动学方程,明确了不同阶段物料的受力状态与运动特征。采用草捆分层切割试验方法,明确草捆的径向密度分布特征,系统分析了密度分布特征形成机理以及对圆捆机性能的影响规律。基于压缩理论建立圆草捆卷压模型,明确卷压过程中压缩力与物料压缩程度之间的函数关系,对模型中各参数进行物理意义标定。研究结果表明,钢辊压力在草捆内部传递损失是造成草捆径向密度差异的根本原因。(3)基于草捆纠缠性高密度环形柱状壳体草捆外层结构特征假设以及压溃理论中环形柱状壳体结构非圆度参数对壳体本身结构强度破坏作用,对9YQ-710型圆捆机进行改造,设计并安装圆捆机钢辊位置调节机构。详细阐述了螺旋线形成型仓结构设计方法和原理,确定了螺旋线形成型仓钢辊布局结构参数及范围。完成了数据采集试验平台整体结构硬件安装与调试工作。完成了控制系统、数据采集系统硬件选型安装以及相关软件的设计工作。搭建完成的圆捆机数据采集试验平台实现了试验台自动化控制要求,具备试验台工作状态监测以及记录试验数据功能,有效增强了试验的工作效率与试验数据采集的准确性。(4)基于EDEM离散元仿真技术建立圆草捆卷捆模型,对圆捆机钢辊受力分布特性进行分析,仿真试验研究结论对理论计算结果进行了补足。基于对螺旋线形成型仓钢辊布局螺距参数的调整范围极限值计算结果,对极限螺距调节值的卷捆过程进行仿真研究,结果表明,能够顺利完成卷捆仿真的最高极限螺距值为125mm,并依此确定钢辊螺距值调节范围及划分水平。对不同水平螺距值参数的卷捆过程进行仿真试验,结果表明,草捆内所有物料受到的压缩应力随着草捆压缩比的增大呈指数形式增长,成型仓钢辊布局的变化能有效改变草捆卷压成型所需的卷捆压力。(5)以螺旋线形成型仓钢辊布局结构参数螺距值及圆捆机作业参数喂料速度、钢辊转速为试验因素,以草捆径向压力传递损失、钢辊平均压缩应力、卷捆能耗为圆捆机性能评价指标,以草捆径向密度标准差为草捆品质评价指标,采用Box-Behnken响应面试验方法开展正交试验,建立各指标与各试验因素间的回归模型,分析各因素及其交互作用对圆捆机性能及草捆品质影响规律,确定显著性影响关键参数,确定螺旋线形成型仓圆捆机较优结构参数与工作参数组合为:螺距60mm、喂料速度0.13kg/s、钢辊转速280rpm。基于优化结果进行试验验证,试验结果表明,圆捆机采用螺旋线形成型仓钢辊布局方式较采用圆形成型仓,卷捆能耗降低了11.46%,草捆径向密度均匀性提高了28.51%,草捆径向压力传递损失降低了15.58%,钢辊平均压缩应力降低了17.02%,优化后的螺旋线形成型仓结构显著改善了圆捆机综合性能,同时提高了草捆品质。本文研究结果可为圆捆机通过钢辊布局结构优化改善圆捆机性能、提高草捆品质提供理论依据和实现方法,同时也为其他领域草物料卷压密度分布特征研究提供参考。更多还原

【Abstract】 The Inner Mongolia Autonomous Region has rich grass resources.The harvesting and baling equipment of grass resources facilitates the transportation and storage of loose grass materials,and becomes an important equipment to facilitate the commercialization and circulation of grass products.During the baling process of round baler,the compression force transfer of steel roller to the inner bales gradually decreases,which is an important factor affecting the performance of round baler and the radial density distribution characteristics of formed bales.With the continuous development of relevant theories and the continuous enrichment of research methods,It is of great significance for the development of round baler to further study the radial pressure transfer characteristics and the radial density distribution characteristics of bales in the baling process by means of combining and complementing various theoretical and practical means.Based on the systematic study of the physical and mechanical characteristics of alfalfa,a common baling and pressing object in Inner Mongolia,this thesis uses theoretical analysis,high-speed photography,simulation research and experimental research to explore the baling process of materials,the radial pressure transfer characteristics and the radial density distribution characteristics of bales,and establishes a baling model to represent the relationship between the compression stress of materials and the bale density.The hypothesis of the outer structure of the entangled high density annular columnar shell straw bale was put forward and its forming conditions were analyzed.Based on the damage effect of shell structure non-roundness parameters on its own structural strength in the crushing theory,a spiral forming bin round baler was designed to study the effects of different steel rollers layout parameters on the radial pressure transfer characteristics of bales,the radial density distribution characteristics of bales and the baling process of alfalfa from the perspective of practical experiments and simulation,so as to reveal the formation mechanism of the radial density distribution characteristics of bales.And optimize the layout structure of steel roller in round baler chamber.The specific research content and results are as follows:(1)The physical and mechanical characteristics of alfalfa were studied,and the physical parameters of alfalfa,such as basic dimensions,water content,volume density,absolute density,porosity,static friction coefficient,rolling friction coefficient,collision recovery coefficient,repose angle and shear modulus,were determined,which provided basic data for the subsequent discrete element model establishment and simulation parameter setting of rotary compression process of alfalfa.(2)Theoretical analysis and high-speed photography were carried out on the rotary compression process of materials,and the pressure model and kinematic equation of materials were established to clarify the stress state and movement characteristics of materials at different stages.The radial density distribution characteristics of straw bales were studied by means of layer-cutting test method,and the formation mechanism of density distribution characteristics and its influence on the performance of round baler were systematically analyzed.Based on the compression theory,the rotary compression model of round bales was established to clarify the functional relationship between the compression force and the compression degree of materials in the baling process,and the physical significance of each parameter in the model was calibrated.The results show that the loss of steel roller pressure transfer within the bales is the fundamental cause of the radial density difference of the bales.(3)Based on the hypothesis of entangled high density annular columnar shell bales outer structure and the destruction of the structural strength of the shell caused by the non-roundness parameter of the annular columnar shell in the crushing theory,the9YQ-710 round baler was transformed,and the steel roller position adjustment mechanism of the baler was designed and installed.The design method and principle of spiral chamber structure are described in detail and the parameters and range of steel roller layout of spiral chamber are determined.The hardware installation and debugging of the whole structure of the data acquisition test platform are completed.Completed the hardware selection and installation of the control system and data acquisition system and the design of related software.The completed data acquisition test platform of round baler has realized the automation control requirements,and has functions of monitoring the working status of the test platform and recording test data,which effectively enhances the working efficiency of the test and the accuracy of the test data acquisition.(4)Based on the EDEM discrete element simulation technology,a rotary compression model was established to analyze the pressure distribution characteristics of steel rollers.The results of simulation experiments are supplemented to the results of theoretical calculation.Based on the calculation results of the limit value of the adjustment range of the steel roller layout pitch parameters of the spiral chamber,the simulation study of the baling process of the limit pitch adjustment value is carried out.The results show that the maximum limit pitch value can successfully complete the baling simulation is 125 mm,and according to this conclusion,the adjustment range and division level of the steel roller pitch value are determined.The simulation tests of the baling process with different horizontal pitch values show that the compression pressure of all materials in the bales increases exponentially with the increase of the compression ratio of the bales.The change of the layout of steel roller can effectively change the baling pressure required for baling.(5)Taking the pitch value of steel roller layout parameters of spiral chamber,feeding speed and steel roller rotation speed as test factors,the radial pressure transfer loss of bale,average compression pressure of steel roller and baling energy consumption as the performance evaluation indexes of round baler,and the standard deviation of radial density of bale as the quality evaluation indexes.Box-Behnken response surface test method was used to carry out orthogonal test,and a regression model between each index and each experimental factor was established.The influence law of each factor and their interaction on the performance of round baler and the quality of bales was analyzed,and the key parameters of significant influence were determined.The optimal combination of structural parameters and working parameters of round baler with spiral chamber was determined as follows: Pitch 60 mm,feed speed 0.13kg/s,roller rotary speed 280 rpm.Based on the optimization results,the test results show that baling energy consumption is reduced by 11.46%,the radial density uniformity of bale is increased by 28.51%,the radial pressure transfer loss of baling is reduced by 15.58%,and the average compression pressure of steel roller is reduced by 17.02%.The optimized spiral chamber significantly improves the comprehensive performance of the round baler and improves the alfalfa bales quality.The research results of this thesis can provide theoretical basis and realization method for improving the performance of round baler and improving the quality of alfalfa bales by optimizing the steel roller layout,and also provide reference for the research on the density distribution characteristics of fibre agricultural and animal husbandry materials rotary compression in other fields.更多还原