【作者】 辛明金；

【导师】 李宝筏；

【作者基本信息】 沈阳农业大学 ， 农业机械化工程， 2008， 博士

【摘要】 干旱缺水影响农作物的播种、出苗、以至产量,是制约农业持续发展的重要因素。目前我国47%的地区年均降水量不足400mm,每年受旱农田面积占整个耕地面积的25%～30%,干旱造成的损失超过其它所有自然灾害。作为主要旱作作物的玉米是最重要的粮食和饲料来源,在农业生产和国民经济中占有极其重要地位,由于干旱缺水常无法播种或播种后出苗不全,严重影响其生产。本文结合保水剂的抗旱保水作用、播前浸种、坐水播种以及流体播种的优势,提出了玉米流体穴播方法。通过深入研究流体穴播机理及其关键技术,为流体播种机具的研究及其在旱作农业中的推广应用提供理论依据;为旱作农业解决抗旱、节水、保苗等问题探索一种新途径和新方法,在我国北方长期缺水的现实条件下,具有重要的应用价值和理论意义。1.本文以玉米种子浸泡后物理机械特性、保水剂胶体溶液粘度的测试研究以及流体播种种液用量和施用浓度的试验研究为基础,通过分析揭示了种子各参数的变化规律和差异,在国内首次提出适于机械化流体播种的玉米种子较为合适浸泡时间为16h～24h,确定了种子浸泡后的各参数值、选用保水剂类型及配制种液的浓度要求;2.通过二次回归正交旋转组合设计试验,并利用Matlab与Excel软件分析了各因素对玉米出苗和生长性状的影响关系;分别建立了种液用量、种液浓度与土壤含水量数学模型,确定了干旱条件下种液用量和种液浓度的施用条件;3.通过种子无搅拌条件下的动力学分析,在理论上证实了比重和体积较大的种子在种液中沉降不可避免:深入分析压气搅拌混合机理,首次提出了压气搅拌混合的空气用量的数学模型;分析和试验结果表明,单位容积的种液需要的空气量约为250m~3/m~3·h～330m~3/m~3·h;4.完成了玉米流体穴播装置结构方案确定,采取压气搅拌混合方式,解决种子沉积和伤种问题;设置稳压控制系统,充分利用压缩空气来维持排液压力,克服播种过程中排种不均问题;利用虹吸原理解决种子沉积堵塞,并利用虹吸排种管中的锤击原理解决排种过程中的堵塞。在利用Solidworks软件进行实体建模和模拟验证基础上,研制了玉米流体穴播排种装置。5.本研究的创新点在于:①得出排种阀门开启间隙与开启面积的变化规律;建立了阀门杆关闭的微分方程,求解排种阀门关闭时间和开口面积的变化规律,确定了开口面积的选用原则;②建立了流体穴播一次排液量与虹吸排种管内径、进出口的垂直距离,种箱内液面高,拨轮半径、拨轮转速,拨轮与阀门杆位置尺寸,阀门杆的结构参数,挡球的质量、直径,弹簧弹性系数以及流量系数的关系的数学模型;利用Matlab软件分析结果表明,可通过更换不同管径的排种管、拨轮转速进行排液量调整;③建立了排液播种过程中,保证排液稳定的空气用量的数学模型:由此得出单位容积的种液需要的空气量为69.2m~3/m~3·h～149.5 m~3/m~3·h;④通过对虹吸排种管中的锤击现象的分析,确定了阀门关闭时弹簧拉力数学模型;6.试验研究结果表明,本研究所研制的流体穴播装置能够实现玉米流体播种,其穴播粒数在2±1之间的穴粒数合格率为75%左右;伤种率为0;空穴率较高,部分试验超过了10%;平均穴距为356.5 mm,穴距合格率为91.67%,穴距稳定性变异系数CV为22.99%;内径20mm排种管的排液量在70～140ml之间可调。7.经济效益分析结果表明,玉米流体穴播的成本、增产效益、节水效益以及机具开发和应用等方面具有较好的经济性和应用前景。更多还原

【Abstract】 Water shortage affects the sowing,emergence and yield of crop and it is one of the most important factors which limit the development of agriculture.Maize is one the main dry farming crops which is the most important source of food and forage,and it plays an essential role in agricultural production and natural economy.But it couldn’t be sowed or with a low emergence rate for drought.The fluid hilling of maize was put forward in this study which combines the functions of water preserving agent,the watering bed sowing,the properties of the soaked seeds and fluid sowing.The mechanism and key technology of fluid hilling was studied which will contribute to the development and application of fluid sowing machine. The study explored a new way to resist drought,save water and ensure emergence rate.It is especially significant for northern China where lacks of water.1.According to the study on the physical and mechanical properties of soaked maize seeds, the test on viscosity,quantity and concentration of the mixed liquid of water preserving agent, the varying principle and diference of the parameters of soaked seed were revealed in this study and the suitable soaking time of maize seeds for fluid sowing was put forward for the first time which was16h～24h.And the parameters of soaked maize seeds,the type of water conserving agent utilized and the concentration of the sowing fluid were determined.2.The quadric orthogonal revolve test was carried out and the effect of the factors on the emergence of maize seed and growth was analyzed with Matlab and Excel.The mathematic model of fluid quantity and soil water content,the fluid concentration and soil water content were set up respectively.The applied fluid quantity and concentration for soil with different water content were determined.3.Dynamic analysis on the seeds in the fluid without agitation showed that the seeds of larger specific gravity and volume will settle in the fluid.The mechanism of pneumatic agitation and mixing was done and the mathematic model between the air quantity needed and the length,width of the seed chamber,the fluid height in the chamber and the required fluid velocity was put forward for the first time.The analysis and experiment showed that the required air quantity for unit volume of fluid was 250m~3/m~3·h～330m~3/m~3·h;4.The structure of maize fluid hilling device was determined and air blowing agitation was utilized to reduce the seeds settlement and damage.The pressure control system was set to maintain fluid metering pressure to avoid uneven seed metering caused by the decrease in height and pressure of the fluid in the chamber.Siphon principle was applied to solve the problem of seed settlement and the hammering function in the siphon tube was utilized to avoid seeds blocking during metering.The maize seed fluid metering device was designed based on solid model and simulation verification with Solidworks. 5.The principal innovation of this study are as following:①The varying law of the opening lash and the area of the metering valve was determined; the differential equation of the close of valve stem was established;the selecting principle for the opening area of the valve was determined by solving the equation of the closing time and opening area.②The mathematic model of the metering rate of fluid per hill to the diameter and the vertical distance between the inlet and outlet of the siphon metering tube,height of the fluid in the chamber,radius and angular velocity of the push wheel,the position of the push wheel and the valve stem,the parameters of the valve stem,the mass,diameter of the block ball,the elastic coefficient of the spring and the coefficient of the fluid metering rate.The analysis based on Matlab showed that the fluid metering rate could be varied by changing tube with different diameter or changing the revolutions of the push wheel.③The mathematic model of the increased air quantity needed to maintain stable fluid metering to the metering rate per hill,times of metering and dimension of the chamber was established.The air quantity needed per unit volume of fluid was 69.2m~3/m~3·h～149.5 m~3/m~3·h according to the formula.④The mathematic of the pull of spring was determined through analysis on the hammering impact in the siphon tube which will help to the design of the spring.6.The experiments results showed that the fluid metering device could realize maize seed fluid hilling.The percentage of hills with seeds of 2±1was 75%,seeds damage was 0,it had a larger percentage of empty hill,some of it was greater than 10%,the percentage of the permitted hill distance was 91.67%,the variable coefficient of the hill distance was 22.99%. The metering rate of fluid with a metering tube of 20mm can be adjusted between 70 ml～140ml.7.The economic analysis on the cost of fluid sowing,the increase of yield,the water saving and the development and application of the fluid sowing device showed that the fluid sowing is economical.更多还原