青贮玉米秸秆螺旋致密成型工艺及压缩过程流变学试验研究

发布时间：2018-03-19 21:22

本文选题：青贮玉米秸秆　切入点：致密成型　出处：《中国农业大学》2017年博士论文　论文类型：学位论文

【摘要】：本研究以青贮玉米秸秆为研究对象,结合青贮玉米田间一体化作业机械化集成需求和青贮玉米秸秆致密成型技术要求,提出了一种机械化螺旋致密成型工艺并设计了螺旋致密成型装置。基于螺旋致密成型工艺搭建试验台,进行了螺旋压缩物料过程中物料流变学规律的相关试验研究。本研究提出了一种螺旋致密成型工艺,基于物料轴、径向力学特性的差异,结合考虑压缩过程能耗、压缩产品稳定性等因素,采用螺旋输送装置调理物料茬口分布的方式理顺秸秆碎料的布置方式,其技术核心是采用螺旋输送装置对物料进行连续分层喂入,并通过螺旋叶片下表面与物料作用理顺物料茬口使物料处于平铺状态进行压缩成型,从而优化压缩方式保证成型质量。搭建青贮玉米秸秆螺旋致密成型试验台,压缩力和径向应力全过程规律试验研究、螺旋压缩单元压缩力变化规律研究;不同含水率(45%、55%、65%)、不同切断长度(20 mm、30 mm、40 mm)和不同压缩密度(400kg/m~3、500kg/m~3、600kg/m~3)条件下,物料松弛特性研究;以及不同机械化加工工艺参数对螺旋压缩装置的功耗影响研究。通过试验得到螺旋压缩全过程物料压缩力变化规律以及最大压缩力、最小变性恢复力变化曲线;采用压缩单元试验方法,发现从压缩力变化规律角度螺旋压缩过程可分为四个阶段,即自然填充阶段、压实阶段、压力下降阶段和快速回弹阶段,并得到了各个阶段物料受压缩力变化规律模型以及不同因素对螺旋压缩单元压缩力的影响;试验结果表明压缩完成后,物料在各个高度梯度内的竖直方向和水平方向均呈明显的应力松弛现象,其松弛模型可表示为两个经典Maxwell模型并联。发生应力松弛前20s时间内,物料内残余应力瞬速衰减,约有80%的残余应力在其间发生衰减。在高度梯度水平上,随距离出料端面的距离越大物料的应力松弛量越大;物料越靠近成型腔底部应力松弛速率越慢,越趋于成型腔顶部松弛速率达到最大。确定了压实密度、物料含水率和切断长度等主要影响因素对应力松弛量、应力松弛率和松弛模量的指标的响应关系。通过正交试验,确定了不同物料含水率条件下,不同机械化加工工艺参数对压缩装置消耗功率的影响模型,在各个含水率条件下,针对螺旋压缩装置总功耗的影响排序为压缩密度行进速度切断长度;得到当压缩密度为400kgh/m~3,切断长度为30mm,含水率为65%,行进速度为0.6m/s时,压缩装置总功耗最小。通过螺旋压缩装置田间生产试验,得到压实密度实际控制范围为316-768kg/m~3;实际生产压缩产品压实密度与预设压力值同一度良好,可达到91.63%;对应压实密度指标的出料效率为:400 kg/m~3条件时出料效率为2.78× 10~3kg/h、500 kg/m~3条件时出料效率为3.36× 103kg/h、600 kg/m~3条件时出料效率为3.49× 10~3kg/h和700 kg/m~3条件时出料效率为2.33× 10~3kg/h。论文的研究对丰富青贮物料压缩方法是一项有益的补充,对于研究螺旋致密成型装置—物料作用关系、深入探讨牧草鲜物料流变特性、完善牧草压缩理论和指导牧草压缩样机研发和生产实践有着重要的意义。
[Abstract]:In this study, corn straw silage as the research object, combined with the integration of the mechanization of silage maize field integrated demand and silage corn straw briquette technology, puts forward a mechanical spiral compact molding process and the design of the spiral compact molding device. The spiral compact molding experiment based on the related experimental research pattern of rheological materials in the process of the compression coil. This study presents a compact spiral forming process, based on the material mechanical properties of radial shaft, difference, considering the energy consumption in the process of compression, compression product stability and other factors, the spiral conveying device of material distribution way to straighten out the conditioning stubble arrangement of straw crushed material, its core technology is adopted spiral conveying device for continuous stratified material feeding, and the role of material surface and through the vane to straighten out the material. Make the material compression molding in flat state, so as to optimize the compression molding quality assurance was set up. The corn silage straw briquette spiral test, experimental study on law of the whole process of compression stress and radial and spiral compression unit variation of compression force; different water content (45%, 55%, 65% (20), different cutting length mm, 30 mm, 40 mm) and different density (400kg/m~3500kg/m~3600kg/m~3) under the condition of relaxation properties of materials; and different mechanical processing parameters on power spiral compression device. By test the whole process of spiral compression material compression force variation and the maximum compressive force, the restoring force curve with minimal degeneration; test method for compression unit that can be divided into four stages from the compression force variation angle spiral compression process, namely natural filling stage, compaction stage, under pressure Drop stage and rapid rebound stage, and each stage of material shrinkage model compression force variation and influence of different factors on the spiral compression unit compression force; test results show that the compression is completed, vertical and horizontal direction of the material in each height gradient in both showed stress relaxation phenomenon, the relaxation model can be said for the two classic Maxwell model should be parallel. 20s time stress relaxation within the material residual stress in the instantaneous velocity attenuation, about 80% of the residual stress attenuation occurs in the meantime. In high gradients, with the distance from the stress relaxation of the material from the end face of the material is more material; near the bottom of the forming cavity stress relaxation rate is slower, more molding cavity top relaxation rate reached the maximum. The compaction density, moisture content and cut off the length of the main influence factors of the stress relaxation quantity, Li Song The relationship between response rate and relaxation relaxation modulus index. Through orthogonal test, to determine the different moisture content under the condition of different process parameters on mechanical compression device power consumption model, in the conditions of various water content, the effect of helical compression device for sorting the total power consumption of compressed density speed cutting length is obtained; when the 400kgh/m~3 compression density, cutting length is 30mm, moisture content is 65%, speed is 0.6m/s, the total power consumption. The minimum compression device of spiral compression device field test, get the actual control of compaction density range is 316-768kg/m~3; the actual production of products of compact density and compression preset pressure value with once well reached 91.63%; corresponding the compaction density index discharge rate: 400 kg/m~3 when the discharge efficiency is 2.78 * 10~3kg/h, 500 kg/m~3 when the discharge efficiency is 3.36 * 103kg/h, 600 Kg/m~3 when the discharging efficiency is 3.49 * 10~3kg/h and 700 kg/m~3 when the discharge efficiency is 2.33 * 10~3kg/h. this research is a beneficial supplement to the compression method for the study of silage material rich, dense spiral forming device - material interaction, in-depth study of the fresh grass material rheological properties, improve the forage compression theory and the significance of forage compression prototype development and production practice.

【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S816.9

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