本文選題：采集頭 + CFD模擬��； 參考：《中國農業(yè)機械化科學研究院》2017年碩士論文

【摘要】：我國苜蓿種植面積、總產量均居世界前列,隨著畜牧業(yè)的發(fā)展,苜蓿種植規(guī)模仍在持續(xù)、快速地增長,但由于苜蓿植株的特殊結構,苜蓿種子采集難度大、機械化收獲技術水平不高。本文在分析苜蓿植株與種莢生長特性及物理特性的基礎上,對9ZQ-2.7型苜蓿種子采集機采集頭內部結構進行了理論分析和試驗研究,完成了采集頭CFD模擬及結構改進優(yōu)化方案設計,最終實現(xiàn)采集頭進口速度分布均勻性的提高。主要研究內容和結論如下:1、本文對苜蓿植株及種莢的物理特性與空氣動力學特性進行了試驗研究。利用統(tǒng)計學原理建立了具有北方代表性品種的紫花苜蓿的物理力學特性與空氣動力學特性的基礎數(shù)據(jù),苜蓿植株的高度、種莢上部高度、種莢下部高度、種莢高度幅差、植株上部直徑、植株中部直徑、植株底部直徑的分布結果分別為796～1184mm、741～1123 mm、490～610mm、181～559mm、1.08～1.52 mm、2.20～3.32 mm、2.46～3.58 mm,苜蓿種子與種莢的懸浮速度分別為:5.06±0.15 m/s、6.95±0.14m/s,莖稈的懸浮速度為8.26±0.15m/s,為采集頭的改進提供數(shù)據(jù)支撐。2、對9ZQ-2.7型苜蓿種子采集機的工作原理及采集頭的結構進行了系統(tǒng)研究。根據(jù)采集頭的結構建立了三維CAD模型,利用前處理軟件對模型進行了簡化,并采用四面體單元進行了網(wǎng)格的劃分;設置了 25個壓力進口及1個壓力出口,建立了k-ε 標準湍流模型,采用速度壓力耦合SIMPLE算法;進口處的壓力為標準大氣壓101325 Pa,出口處的壓力為101085 Pa,來模擬采集頭內氣流場的分布。對仿真結果進行分析,得到原結構的進口速度由左側區(qū)域Ⅰ往右側區(qū)域Ⅲ逐漸減小,而在調風板處的速度出現(xiàn)波動;最左側的速度能達到15.7 m/s,右側的速度最小值為3.61 m/s,從而確定原結構的速度分布均勻性差。3、在原有結構的基礎上進行了仿真分析與試驗,發(fā)現(xiàn)進口處速度分布均勻性差。針對存在的問題對原結構進行改進,設計了 20種改進方案;對改進方案依次進行仿真分析,然后從中選擇三種速度分布均勻性比較好的方案進行試驗驗證;對選擇的三種方案試驗結果進行比較分析,確定最優(yōu)方案為方案12,改方案的結構為d1=198mm,d2=175 mm,α1=15°,α2=20°。
[Abstract]:With the development of animal husbandry, alfalfa planting scale is still increasing rapidly in China. However, because of the special structure of alfalfa plants, it is difficult to collect alfalfa seeds. Mechanized harvesting technology is not high. Based on the analysis of the growth characteristics and physical characteristics of alfalfa plants and pods, the internal structure of the collecting head of 9ZQ-2.7 alfalfa seed collector was analyzed theoretically and experimentally, and the CFD simulation of the collecting head and the design of structural improvement optimization scheme were completed. Finally, the velocity distribution uniformity of the inlet of the acquisition head is improved. The main contents and conclusions are as follows: 1. The physical and aerodynamic characteristics of alfalfa plants and pods were studied in this paper. Based on the principle of statistics, the basic data of physical, mechanical and aerodynamics characteristics of alfalfa with representative northern varieties were established. The height of alfalfa plant, the upper height of seed pod, the lower height of seed pod, the amplitude difference of seed pod height were obtained. The upper diameter of the plant, the diameter of the middle part of the plant, The distribution of the bottom diameters of alfalfa seeds and pods were 796 鹵1184 mm / 741 1 123 mm ~ 490 ~ 610 mm ~ (-1) ~ (59) mm ~ (-1) 1.52 mm ~ 2.20 ~ 3.32 mm ~ 3.46 ~ 3.58 mm, respectively. The suspension velocity of alfalfa seeds and pods was 5.06 鹵0.15 mm / s (6.95 鹵0.14 m / s), respectively. The suspension velocity of stem was 8.26 鹵0.15 m / s, which provided data support for the improvement of collecting head, and provided data support for 9ZQ-2.7 type alfalfa seed collector. The working principle and the structure of the collecting head are studied systematically. According to the structure of the collecting head, the 3D CAD model is established, the model is simplified by pre-processing software, the mesh is divided by tetrahedron element, 25 pressure inlet and 1 pressure outlet are set up. The k- 蔚 standard turbulence model is established, and the velocity and pressure coupled simple algorithm is used. The pressure at the inlet is 101325 Paa and the pressure at the exit is 101085 Pa. to simulate the distribution of the air flow field in the head. The simulation results show that the inlet velocity of the original structure decreases gradually from the left region I to the right region 鈪，

本文編號：1996364