基于CFD-DEM耦合的气流一阶集排式排种系统仿真与试验

发布时间：2018-04-24 00:40

本文选题：农业机械 + 播种机　；参考：《昆明理工大学》2017年硕士论文

【摘要】：近年来谷物种植规模化的发展及大型拖拉机的推广应用,使播种机械向大幅宽、高速度作业方向发展。而我国市场上现有的播种机仍以配套中小型拖拉机的型号居多,多采用“一器一行”的排种器形式,增大幅宽时,就需要增加相应数量的排种器,排种器数量过多会造成播种机整机结构臃肿、庞大,不便于作业转场运输及保证作业质量。而集排器相比“一器一行”式排种器排种效率高、单个排种器能同时完成多行的排种任务。大宽幅播种机采用集排器可减少排种器的使用数量,简化播种机整机结构,是近年来的发展方向。本文在国内外研究基础上,设计了气流一阶集排式排种系统。利用CFD-DEM耦合数值模拟的方法优化排种系统结构,对设计计算加以修正。试制气流一阶集排式排种系统样机,搭建气流一阶集排式排种系统试验台对气流一阶集排式排种系统进行排种性能试验研究,得出最优排种性能工作参数。本论文具体研究内容如下:(1)通过查阅相关文献掌握了小麦种植的农艺要求,根据农艺要求确定气流一阶集排式排种系统结构方案,并对其结构和工作原理进行了阐述,对系统工作参数和关键部件进行设计计算。(2)根据设计的集排系统参数建立数值仿真模型进行耦合计算分析,模型收敛性良好,验证了 CFD-DEM耦合法模拟排种系统的可行性。仿真计算种子排出系统速度达2m/s,没有出现种子的沉降,滞留及堵塞现象,气流一阶集排系统设计功能实现。排种速度达15.6kg/min,各行排量一致性变异系数为4.7%。(3)查阅相关文献资料,采用PB试验设计方法,利用CFD-DEM耦合数值模拟的方法对影响集排系统排种性能的结构参数进行仿真试验,筛选出混合室长度、弯管弯径比、褶型管长度为对排种性能的主要影响因素。设计二次旋转正交组合试验进行仿真试验,得出混合室长度、弯管弯径比、褶型管长度对排种性能的影响规律,对参数进行优化分析得出褶型管长度在297.46mm时,混合室长度在196.4-208.2mm、弯径比在4.7-5.5时为最优结构参数组合,各行排量一致性变异系数小于4.6%。根据仿真试验优化出的结构参数试制排种系统样机,搭建试验台进行试验验证,试验结果各行排量一致性变异系数为5.18%。由于安装制造有误差及实际试验条件无法达到模型理想边界条件,验证试验结果略有偏差,仿真试验结果可信。(4)设计入风口气流速度、喂种速度对排种性能影响的单因素试验,通过单因素试验分析得出喂种量为260g/s,气流速度为40m/s时各行排量一致性变异系数最低为6.8%。气流速度为40m/s,喂种速度为300g/s时各行排量一致性变异系数最低为6.1%。以气流速度、喂种速度、弯管弯径比为影响因素,以各行排量一致性变异系数为目标函数,采用二次旋转正交组合试验设计方法,对试验结果进行优化分析,弯管弯径比为5时,气流速度为49.2-51.9m/s、喂种速度为258.7-267.6g/s时为最优工作参数组合,各行排量一致性变异系数小于4.35%。(5)在气流一阶集排式排种系统设计和试制基础上,对其结构及工作参数对排种性能的影响进行研究,为工程设计和进一步研究提供参数依据和理论基础。
[Abstract]:In recent years, the large-scale development of grain planting and the popularization and application of large tractors have made the sowing machinery develop to a large width and high speed. However, the existing sowing machines in our market still take the majority of the types of small and medium tractors and adopt the "one row" type of seed metering device, and the corresponding number should be increased when the width is enlarged. The quantity of seed metering device is too large, which can cause the whole structure of the planter to be overstaffed and large, and it is not convenient for the operation to transfer the field and guarantee the quality of the work. Using the quantity to simplify the whole structure of the planter is the direction of development in recent years. On the basis of the research at home and abroad, this paper designs the first order discharge system of air flow. Using the method of CFD-DEM coupling numerical simulation, the structure of the seed metering system is optimized and the design calculation is revised. The experimental research on the performance of the first order collection system is carried out to get the optimal performance parameters. The specific contents of this paper are as follows: (1) the agronomic requirements of the wheat planting are mastered by consulting the relevant literature, and the first order collection system of the air flow is determined according to the agronomic requirements. The structure and the working principle are expounded, and the working parameters and key components of the system are designed and calculated. (2) the numerical simulation model is established based on the parameters of the designed set arrangement system to carry out the coupling calculation and analysis. The convergence of the model is good, and the feasibility of the CFD-DEM coupling simulation seed metering system is verified. The speed of the output system is up to 2m/s. There is no seed settlement, stagnation and blockage. The design function of the first order air collection system is realized. The speed of the first order of the air flow is realized. The row speed is up to 15.6kg/min, the consistency variation coefficient of the row displacement is 4.7%. (3), and the PB test design method is used, and the CFD-DEM coupling numerical simulation method is used to influence the collection system. The length of mixing chamber, the ratio of bend pipe to diameter, and the length of the fold tube are the main factors affecting the performance of the seed metering. The two rotation orthogonal combination tests are designed to simulate the influence of the length of the mixing chamber, the ratio of the bend diameter and the length of the fold tube to the performance of the seed arrangement, and the parameters are superior to the parameters. When the length of the fold tube is in 297.46mm, the length of the mixing chamber is 196.4-208.2mm and the ratio of the bend diameter is the best combination of the structural parameters. The consistency variation coefficient of the row displacement is less than that of the 4.6%.. The test results are set up to verify the test results. The induced coefficient of variation is 5.18%. because the installation error and actual test conditions can not reach the ideal boundary condition of the model. The results of the test are slightly deviant, and the results of the simulation test are credible. (4) the single factor experiment on the design of air flow velocity and the effect of feeding speed on the performance of the seed seed is 260. G/s, when the velocity of air flow is 40m/s, the minimum variation coefficient of the line displacement is the lowest 6.8%. flow velocity of 40m/s. When the feeding speed is 300g/s, the lowest coefficient of variation is 6.1%. at the velocity of air flow, the feed rate and the ratio of bend diameter of the pipe are the influence factors, and the coefficient of variation of each line is taken as the objective function, and the two rotation positive is used. The test results are optimized and analyzed. When the ratio of bend to diameter is 5, the velocity of air flow is 49.2-51.9m/s and the feeding speed is 258.7-267.6g/s, it is the best working parameter combination. The coefficient of variation of the consistency of each row is less than 4.35%. (5). On the basis of the design and trial production of the first order collection system of air flow, the structure and the structure of the system are discussed. The influence of working parameters on seeding performance is studied, which provides parameter basis and theoretical basis for engineering design and further research.

【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

【参考文献】