气吸滚筒式小麦精密排种器设计与试验研究

发布时间：2018-10-22 18:01

【摘要】：小麦精量播种技术是余松烈院士提出的小麦种植方式,较传统小麦种植方式增产10%以上,小麦精量播种要求种子行距株距确定,传统的小麦排种器以外槽轮式为主,难以实现小麦精播,本文在分析了现有机械式及气力式精密排种器的结构及工作原理的基础上,设计了气吸滚筒式小麦精密排种器,并对排种器内流场情况及工作状态进行了仿真分析,采用理论与试验相结合的方法,对气吸滚筒式小麦精密排种器进行了研究,主要研究内容和结论如下:(1)以小麦精量播种的农艺要求为理论依据,以京冬22号小麦种子为试验对象,在测量了小麦种子三轴尺寸、千粒重和球形度等物理参数的基础上,基于机械式和气吸式精量播种原理,研制了一种可以满足小麦精量播种的气吸滚筒式小麦精密排种器,对排种器关键部件的设计及工作原理进行了阐述,并分析了排种器在排种过程中种子的受力情况,最后利用三维建模软件Creo建立了气吸滚筒式小麦精密排种器的三维模型。(2)以计算流体力学为理论依据,以Ansys和Fluent软件为计算平台,在Ansys Meshing软件中对简化后的气吸滚筒式小麦精密排种器的三维模型进行了网格划分,在Fluent软件中对划分好的网格模型进行了流场分析,分别以排种滚筒上吸孔直径和排种滚筒吸室真空度为影响因素,分析不同影响因素对应的排种器内部流场的变化情况,仿真结果表明,随着吸孔直径的逐渐增加,吸孔内负压值逐渐减小,吸孔内气流速度逐渐减小,吸孔吸附能力下降;当负压风机提供稳定的负压后,真空吸室内流场的分布不再受风机的影响,风机只对流场压力大小和流速大小产生影响。采用台架试验对仿真结果进行了验证,结果表明,仿真结果与试验结果存在一定差值,但二者总体的变化趋势保持一致,证明仿真结果可以用作参考。(3)以离散元素法为理论依据,借助离散元仿真软件EDEM建立了小麦种子的三维仿真模型,并对排种器的排种过程进行了仿真分析。由仿真结果可以看出,种子生成并落入吸种区后,贴近排种滚筒表面的种子受滚筒的摩擦力最先运动,部分种子落入窝眼内,并随排种滚筒旋转直至脱离窝眼。排种过程仿真分析得出了种子的运动速度及受力随时间的变化曲线,种群与排种滚筒的接触粒数及种群与排种滚筒摩擦力随时间变化关系曲线图。(4)采用3D打印技术加工了气吸滚筒式小麦精密排种器,设计并搭建了小麦精量播种试验台,进行了气吸滚筒式小麦精密排种器的台架试验,分别以吸孔直径、吸室真空度和排种滚筒转速为影响因素,以重复吸种率、漏吸种子率、吸种合格率和标准差变异系数为评价指标,进行了单因素试验,并对各影响因素进行了方差分析,得出了不同影响因素对评价指标影响的显著性,试验得出了吸室真空度为3500Pa、吸孔直径为1.6mm、排种滚筒转速为40r/min时排种器的吸种合格率最高为90.2%。
[Abstract]:The wheat precision sowing technology is the wheat planting mode proposed by academician Yu Songlie. Compared with the traditional wheat planting mode, the wheat planting mode is increased by more than 10 percent, the precision sowing of the wheat requires the distance between the seed spacing and the row spacing, the traditional wheat row seed device is mainly wheel-shaped, and the wheat fine seeding is difficult to achieve, On the basis of analyzing the structure and working principle of the existing mechanical and pneumatic type precise exhaust device, this paper designs a kind of precision exhaust device of air-suction drum type wheat and simulates the flow field situation and working condition in the row type device, and adopts the combination of theory and experiment. The main research contents and conclusions are as follows: (1) The wheat seed is the test object based on the agronomic requirements of wheat precision seeding, and the three-axis size of wheat seeds is measured. On the basis of the physical parameters such as 1000-grain weight and sphericity, based on the principle of mechanical and gas-suction type precision sowing, a kind of air-suction drum-type wheat precise row cutter which can meet the precision sowing of wheat is developed, and the design and working principle of key parts of the row type device are expounded. In this paper, the stress condition of seed is analyzed, and the three-dimensional model of air-suction drum-type wheat precise row cutter is established by using three-dimensional modeling software Creo. (2) Based on computational fluid mechanics and Ansys and Fluent software as the computing platform, the three-dimensional model of the simplified gas-suction drum-type wheat precise row cutter is divided into three-dimensional model by Ansys and Fluent software, and the divided grid model is analyzed in Fluent software. On the basis of the influence factors of the diameter of the suction hole and the vacuum degree of the oil suction chamber of the discharge roller, the change of the internal flow field of the ejector corresponding to the different influencing factors is analyzed, and the simulation results show that the negative pressure value in the suction hole gradually decreases as the diameter of the suction hole increases gradually. When the negative pressure fan provides a stable negative pressure, the distribution of the flow field in the vacuum suction chamber is no longer affected by the fan, and the fan only influences the size of the convection field and the size of the flow velocity. The simulation results are verified by bench test. The results show that the simulation results are different from the experimental results, but the overall trend of the simulation results is consistent, and the simulation results can be used as references. (3) Based on the discrete element method, the three-dimensional simulation model of wheat seeds was established by using DEM of discrete element simulation software. It can be seen from the simulation results that after the seed is generated and falls into the seed absorption region, the seeds close to the surface of the row roller are first moved by the friction force of the roller, some of the seeds fall into the nest, and rotate with the row of rollers until the seed is disengaged. In this paper, the movement speed of seed and the change curve of stress over time, the number of contact grains of population and row type roller, and the relationship of population and row type roller friction with time were obtained by simulation analysis. (4) adopting 3D printing technology to process the air suction drum type wheat precise row seed device, designing and constructing the wheat precision sowing test bed, carrying out bench test of the air suction drum type wheat precise row seed device, respectively taking the diameter of the suction hole, the vacuum degree of the suction chamber and the rotating speed of the row of the roller as the influencing factor, The single factor test was carried out on the basis of the repetition rate, the seed rate of the leak, the rate of absorption and the variation coefficient of standard deviation as the evaluation index, and the influence factors were analyzed by variance analysis, and the significance of different influencing factors on the evaluation index was obtained, and the vacuum degree of the suction chamber was 3500Pa. When the diameter of the suction hole is 1. 6mm and the rotating speed of the row is 40r/ min, the qualified rate of seed suction is 90.2%.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S223.2

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