气力滚筒式异形种子精量排种器的设计与研究

发布时间：2018-02-25 09:23

本文关键词： 排种器精量排种吸孔结构流场仿真试验研究　出处：《浙江理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,随着人民生活水平逐步提高,对蔬菜需求量增加,中国已逐渐成为世界上最大的蔬菜生产国和消费国。蔬菜生产具有季节性,而温室技术的应用改变了蔬菜种植受季节限制的特点,但是,温室种植的蔬菜大多采用育苗移栽方式,而蔬菜种子由于其粒径小,形状不规则,目前仍旧以人工或半机械化方式育苗为主,工作效率低。因此,开发适合蔬菜种子外形特点的排种装置,对蔬菜种植业全程机械化推广具有重要意义。本文针对蔬菜种子粒径小,形状不规则等特点,提出一种气力滚筒式异形种子精量排种器,并以芹菜种子良峰玉芹为试验对象,进行试验研究。本文主要研究内容:(1)基于蔬菜种子异形的物理特性,提出了一种气力滚筒式异形种子精量排种器。完成排种器结构参数设计,包括吸孔结构设计、滚筒内腔结构设计、滚筒直径设计、滚筒轴向及周向吸孔间隔设计。(2)建立了排种过程种子的动力学模型,获得吸种阶段排种滚筒直径、吸孔直径、滚筒转速等因素对最小负压区压力的影响规律,携种阶段最小吸附力的变化规律,进行投种阶段滚筒转速、正压区压力值对种子水平位移的影响研究。(3)进行气力滚筒式异形种子精量排种器气流场仿真分析,获得正、负压区流场分布规律,得到正、负压区的吸孔端面压力与正、负压区的入口正压值、出口负压值呈近似线性关系。进行吸孔参数对排种器正、负压区流场分布的影响研究,获得最佳吸孔结构参数组合。(4)对气力滚筒式异形种子精量排种器排种过程进行耦合分析,研究排种器正压区入口压力值、滚筒转速对种子运动状态的影响规律,得到投种过程种子水平方向速度降与正压口压力呈线性关系。(5)研制气力滚筒式异形种子精量排种器,开展排种性能测试。分别以吸孔结构参数、排种器运行参数为试验对象进行单因素试验研究,再进行正交试验研究,试验结果表明:排种器合格率、重播率、空穴率、单粒率受吸孔直径、吸孔末端直径、滚筒转速以及正、负压口压力值影响均较为显著。当吸孔直径为0.7mm,吸孔末端直径为2mm,吸孔过渡层直径为2mm,转速为12r/min,正压口压力值为1500Pa,负压口压力值为-4000Pa时,排种器工作状态最佳,排种合格率达到71.78%,空穴率为16.82%。
[Abstract]:In recent years, with the gradual improvement of people's living standards and the increasing demand for vegetables, China has gradually become the world's largest vegetable producer and consumer. Vegetable production is seasonal. The application of greenhouse technology has changed the seasonal limitation of vegetable planting. However, most of the vegetables grown in greenhouse are planted by transplanting seedlings, and the seeds of vegetables are irregular because of their small diameter. At present, it is still mainly artificial or semi-mechanized, and its working efficiency is low. Therefore, a seed metering device suitable for the appearance characteristics of vegetable seeds is developed. Aiming at the characteristics of small grain size and irregular shape of vegetable seeds, a pneumatic roller type special-shaped seed metering device was put forward, and the celery seed Liangfeng Jade celery was taken as the experimental object. In this paper, based on the physical characteristics of vegetable seed specialities, a pneumatic roller type seed metering device with special-shaped seed is proposed. The structure parameters of the metering device are designed, including the design of sucking hole structure, the main content of this paper is as follows: (1) based on the physical characteristics of the abnormal shape of vegetable seed, a pneumatic roller type seed metering device is proposed. The design of inner cavity, diameter of drum, interval between axial and circumferential suction holes of roller are designed. The dynamic model of seed seeding process is established, and the diameter of seeding drum and suction hole is obtained in the stage of sucking seed. The influence of cylinder speed and other factors on the pressure in the minimum negative pressure region and the variation rule of the minimum adsorption force in the seed carrying stage, and the rotating speed of the roller in the feeding stage, Study on the effect of pressure value in barotropic region on horizontal displacement of seed. (3) Simulation analysis of airflow field in pneumatic cylinder type special-shaped seed metering device is carried out, and the distribution law of flow field in positive and negative pressure zone is obtained, and the pressure and positive face of suction hole in positive and negative pressure region are obtained. The inlet positive pressure and outlet negative pressure of negative pressure region are approximately linear. The influence of suction hole parameters on the flow field distribution in the positive and negative pressure region of the metering device is studied. The optimum structure parameter combination of suction hole is obtained. The coupling analysis is carried out on the seeding process of the pneumatic cylinder type special-shaped seed metering device. The influence of the inlet pressure in the positive pressure zone of the metering device and the rotational speed of the roller on the seed motion is studied. The linear relationship between the horizontal velocity drop of seed and the pressure of barotropic orifice was obtained. 5) the pneumatic roller type seed metering device was developed, and the metering performance test was carried out. The parameters of suction hole structure were used respectively. The operation parameters of seed metering device were studied by single factor test and orthogonal test. The results showed that the qualified rate, resowing rate, hole rate, single grain rate and terminal diameter of suction hole were obtained. When the diameter of suction hole is 0.7 mm, the end diameter of suction hole is 2 mm, the diameter of transition layer of suction hole is 2 mm, the rotational speed is 12 r / min, the pressure value of positive pressure port is 1500 Paa, and the pressure of negative pressure port is -4 000 Pa. The seed metering device has the best working condition, the qualified rate of seed metering is 71.78 and the hole rate is 16.82.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S223.2

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