【作者】 丛锦玲；

【导师】 廖庆喜；

【作者基本信息】 华中农业大学 ， 农业机械化工程， 2014， 博士

【摘要】 小麦、油菜是中国重要的粮油作物,油菜种植面积相对稳定,2012年播种面积约为700万公顷,但机械化播种水平仅为14.51%；小麦种植面积呈逐年增高趋势,2012年达2427万公顷,机械化播种水平为86.52%,但多以机械化条播为主。油菜、冬小麦均为秋冬种作物,特别是长江流域油菜与小麦播种期相邻、种植工序相似。为提高播种机具的利用率,实现一机兼播油菜小麦两类作物,研制了一种新型油菜小麦兼用型气力式精量排种器。本文基于负压气流吸种、正压气流投种的工作原理,集成气力式精密排种技术,针对油菜小麦物料特性差异大,创新性提出一种排种盘内嵌入导种条式的油菜小麦兼用型气力式精量排种装置,并在此基础上,深入开展油菜与小麦兼用型气力式精量排种系统及其机理研究。主要研究内容包括：(1)系统开展了油菜、小麦的机械物理特性参数的测试与分析,得出种子基本外形尺寸、种子千粒质量、自然休止角、种子内摩擦系数等,为排种器主要结构参数的设计提供理论依据；利用负压吸种、正压投种的正负气压组合式原理,研制开发一种油菜、小麦兼用型气力式精量排种系统,分析确定了该兼用型排种器的结构参数和工作参数。(2)分析研究了油菜小麦兼用型排种器的排种过程,利用力学解析方法,构建排种器主要工作过程的吸种、携种、投种过程中的运动学与动力学模型；分析确定了种子运移过程中不出现滑动、滚动时的条件及其结构参数、运行参数对种子运移过程的影响规律。由分析得知：充种区种子充填角γ与排种盘转速ω、排种盘半径,、导种条倾角900-θ及种子与导种条间和种子间的摩擦系数f1、f2相关；吸种与携种负压值与种子质量m、种子外形尺寸、排种盘直径d、型孔直径dx、吸种角度α及排种器转速ω相关;投种正压值与种子质量m、排种盘直径d、型孔直径dx、及排种器转速ω相关。(3)系统开展了油麦兼用型排种器台架预试验。初步确定排种盘型孔直圆柱形通孔,油菜排种盘型孔直径为1.2mm,小麦排种盘型孔直径为1.5mmm；小麦排种盘内嵌入导种条为矩形并且呈I形排列。试验表明该排种器的合格指数、重播指数、漏播指数等性能指标受排种盘转速、正负压大小影响显著。试验结果表明当排种器转速、吸种区负压、投种区正压分别为18r/min、-2200Pa、400Pa时,油菜精量播种合格指数为90.02%,漏播指数为2.59%；当排种器转速、吸种区负压分别为15r/min、-2300Pa时,排种盘内嵌入导种条时,小麦精量播种合格指数为90.62%,漏播指数为2.96%。(4)在分析研究油菜小麦兼用型气力式精量排种共性技术与公用主体结构特征基础上,创新性提出一种兼用型内嵌入导种条式排种盘及其型孔结构,以实现油菜小麦气力式精量排种器兼用。研究表明：吸种负压为-2900Pa、排种盘内嵌入导种条可使小麦排种的平均合格指数相对提高30.76%,漏播指数相对降低38.61%；吸种负压为-900Pa、投种正压为500Pa时,排种盘内嵌入导种条可使油菜排种的平均合格指数相对提高3.72%,漏播指数相对降低8.58%；在转速为20～30r/min时,排种性能均能满足油菜小麦兼用精量播种的要求,且排种器内嵌入导种条时对种子无机械损伤。(5)开展了基于高速摄像技术的内嵌入导种条式排种器的充种、吸种、携种、投种四个工作过程在线观察与分析。研究得出：转速范围为10～45r/min时,排种器充种区种子充填角与转速线性相关,排种器内嵌入导种条时,其充种性能明显提高；吸种高度与种子进种口高度相关,进种口高度为47mm时,吸种高度与转速线性相关且拟合度最好；携种路径与转速相关,转速越高,其携种弧长越短；种子投种轨迹及投种过程中种子的位移与排种盘转速、排种盘半径及种子下落时间相关。转速越高时,投种轨迹拟合度越好,越接近平抛运动形成的抛物线,由此优化投种口宽度值为40mm。(6)开展了基于EDEM的种子流迁移规律的仿真分析,探索性开展了种子颗粒体及颗粒体群的速度、位移、合力与时间的作用机理：当排种器转速一定时,充种区颗粒体群生成后,充种区种子群位移随时间呈规律性周期变化,种子群所受合力随时间趋于稳定,其运动速度在颗粒生成后呈小幅度波动变化,总体上趋于平稳,仿真结果与高速摄像得出分析结果一致；同时开展了基于ANSYS软件流体模块ANSYS/CFX和FLUENT的排种器负压气室气流速度场模拟研究,明确了不同型孔结构形状处的气流速度场的分布,得出当型孔为直圆柱孔形时,其气流速度场变化均匀,符合排种器对负压气流速度均匀稳定的要求。(7)开展油菜小麦兼用型气力式精量排种系统的田间播种试验,试验结果表明：排种器各行间排量一致性较好,播种油菜、小麦,其各行间变异系数均低于10%；同时开展了田间成苗率的测试与分析,测试结果表明油菜基本苗为2.92万株／亩；小麦基本苗为3.92万株／亩,分蘖数约为3-10株,分蘖后约为25.48万株／亩。符合油菜、小麦种植农艺要求。利用测点法所开展的田间测产试验表明：油菜每亩预测产量为202kg；小麦每亩预测产量为480kg。创新点1：利用正、负气压组合式的基本原理,研制开发一种适合两种不同粒径的兼用型气力式精量排种器；创新点2：创新性提出一种兼用型内嵌入导种条式排种盘及其型孔结构,以实现油菜小麦气力式精量排种器兼用。更多还原

【Abstract】 Wheat seed and rapeseed are important grain and oil crops in China,the acreage of rapeseed is relatively stable as approximately7,000,000hectares in2012, but the level of mechanization of its planting is only14.51%; The acreage of wheat seed is increasing very year, which approaches to24.27million hectares in2012, the level of mechanization of its planting is86.52%, but majority of it is based on mechanized drilling. Rapeseed and winter wheat are autumn crops, especially in the Yangtze River basin,rapeseed and wheat sowing period are adjacent to each other,the rapeseed’s planting process is similar to the wheat seed’s.Anewdual-purpose both for wheat seed and rapeseed pneumatic precision seeder was developed to improve the utilization of the planterand plant both the rapeseed and wheat seed with only one seeder.Based on the working principle of the sucking section with negative airflow pressure and the releasing section with positive airflow pressure and the integrated pneumatic precision seed technology,a dual-purpose both for wheat seed and rapeseed pneumatic precision metering devices was proposed with innovationbecause of the extremely physical properties differences of the rapeseed and wheat seed, and on this basis,the pneumatic precision metering system and mechanism of dual-purpose for wheat seed and rapeseed were researched.The main contents include:(1) The test and analysis of mechanical and physical properties and parameters for wheat seed and rapeseed were carried out, and the basic size of seed shape,the thousand grain weight of seeds,natural angle of repose for seeds,coefficient of friction of the seeds were obtained,which could provide the theoretical basis for the main structural parameters design,according to the working principle of the sucking section with negative airflow pressure and the releasing section with positive airflow pressure,a kind of rapeseed and wheat seed combined type pneumatic precision metering systems was developed and the structural parameters and operating parameters were analyzed.(2)The releasing process of the seeder both for rapeseed and wheat was analyzed,the kinematics and dynamics model of the seeds when they were in the sucking section,taking section and releasing section were established with the help of mechanical analytical method and got the discipline of how the working index affects the moving seed and analyzed the situation when the seed would not slide or roll while it was moving.The analysis showed that:the filling angle y of seed filling area,the rotating speed ω of seed plate,the radius r of seed plate,the angle of guiding strip90°-θ had a relationship with the friction coefficient f1between seeds and guiding strip and the friction coefficient f2among seeds;The negative pressure of sucking and taking had a relationship with the mass of seed m, the size of seed shape,the diameter d of seed plate,the diameter dx of hole carrying single seed, the angle a of sucking and the rotating speed co of seed plate;The positive pressure of sucking and taking had a relationship with the mass of seed m, the diameter d of seed plate,the diameter dx of hole carrying single seed and the rotating speed ω of seed plate.(3)The test for dual-purpose pneumatic precision metering device both for wheat and rapeseed was carried out in a system way. The hole carrying seed on the seed plate was identified that it was straight cylindrical bore, the diameter of the hole for carrying rapeseed was1.2mm and1.5mm instead for wheat seed plate;The guiding stripes on the seed plate for wheat were a rectangular shape and they were arranged like L.Tests showed that the seeder’s qualified index,multiple index, missing index were affected by rotating speed of the seed plate,the positive and negative pressure significantly.The test results showed that when the rotating speed of the seed plate was18r/min,the negative pressure was2200Pa,the positive pressure was400Pa,the qualified index for seeding rapeseed was90.02%,the missing index was2.59%;when the rotating speed of the seed plate was15r/min,the negative pressure was2300Pa,the qualified index for seeding wheat was90.62%,the missing index was2.96%with guiding strips fixed on the seed plate.(4)Based on the analysis of the common technology and structural features of a public body of dual-purpose pneumatic precision metering for both wheat seed and rapeseed a kind of dual-purpose seeder with guiding strips fixed on the seed plate and its structural of the hole carrying seed was developed for its dual-purpose pneumatic precision metering.Studies had shown that:when the negative pressure was2900Pa,the average qualified index for wheat seeding with guiding strips fixed on the seed plate relatively increased by0.76%and the missing index decreased by38.61%; when the negative pressure was900Pa,the positive pressure was500Pa,the qualified index for rapeseed seeding with guiding strips fixed on the seed plate relatively increased by3.72%and the missing index decreased by8.58%;while the rotating speed of seed plate inside the dual-purpose pneumatic precision metering device was20r/min-30r/min, the seeding performance of the dual-purpose pneumatic precision metering device could meet the requirement of sowing for wheat seed and rapeseed,and there were no mechanical damage to the seeds while the guiding strips were fixed on the seed plate.(5)The process of filling,sucking,taking,releasing in the seeder with guiding stripe fixed on the seed plate was analyzed and observed based on the with the high-speed camera technology.Research results showed:while the rotating speed of seed plate inside the dual-purpose pneumatic precision metering device was10r/min-45r/min, the seeds filling angle and the rotating speed had a linear correlation,the filling performance improved while the seed plate fixed with guiding stripes;The height of sucking point had a relationship with the height of the seed inlet point, when the height of the seed inlet point was47mm,the height of sucking point had a best linear correlation with the rotating speed;The path length of taking section had a relationship with the rotating speed,the faster of speed,the shorter of the path length of taking section;The releasing trace and the path length of releasing had a relationship with the rotating speed of the seed plate,the radius of the seed plate and the falling time of the seed.The faster of the rotating speed,the better of degree of fitting for the releasing trace and the closer to the parabola when it was doing a horizontal cast movement,the width of the releasing outlet would be40mm.(6)A simulation of the seed flow movement was carried out with the help of EDEM,the velocity,displacement,force and time of the seed granules and granule group was conducted in a exploratory way:when the rotating speed didn’t get changed,the displacement of the granules group got a regular cycle changing with time,the force of the granule group would be stable with the time went on,the velocity of the granule group would get changed within a narrow range after the seeds became to granule group,which were stable overall,the simulation results with the results obtained consistent high-speed camera;Meanwhile,a simulation of the air flow inside the seed chamber was carried out based on the software named of ANSYS-fluid module ANSYS/CFX and FUENT,defined the velocities of the air flow with the different holes shape,and when the hole was drawn straight cylindrical bore hole shape,its airflow velocity changed in a uniform way,which could match the requirements of the uniform air negative flow for the seeder.(7)The test for the seeding system in field was carried out,results showed that:every row of the output volume had a good consistency,the variable coefficient of each row was under10%when seeding rapeseed and wheat seed;Meanwhile,the test and analysis of the seedling rate in field were carried out,the test results showed that rapeseed planting density could be29,200/acre;wheat planting density could be39,200thousand/acre,the tiller number was about3to10,after that it could be about254,800/acre,which could match the agronomic requirements of wheat and rapeseed.Field production test showed that:the pre-production of rapeseed would be202kg/acre;the pre-production of wheat would be480kg/acre. Innovation Point1:Using the basic principles of positive and negative pressure modular, developed a suitable particle size combined use of two different type Pneumatic precision seeder;Innovation Point2: Innovatively proposed a dual-purpose seeder within guiding stripes and holes inside to match the purpose of a a pneumatic precision metering device for dual-purpose use;更多还原