本文選題：采集頭 + CFD模擬�。� 參考：《中國(guó)農(nóng)業(yè)機(jī)械化科學(xué)研究院》2017年碩士論文

【摘要】：我國(guó)苜蓿種植面積、總產(chǎn)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(zhǎng),但由于苜蓿植株的特殊結(jié)構(gòu),苜蓿種子采集難度大、機(jī)械化收獲技術(shù)水平不高。本文在分析苜蓿植株與種莢生長(zhǎng)特性及物理特性的基礎(chǔ)上,對(duì)9ZQ-2.7型苜蓿種子采集機(jī)采集頭內(nèi)部結(jié)構(gòu)進(jìn)行了理論分析和試驗(yàn)研究,完成了采集頭CFD模擬及結(jié)構(gòu)改進(jìn)優(yōu)化方案設(shè)計(jì),最終實(shí)現(xiàn)采集頭進(jìn)口速度分布均勻性的提高。主要研究?jī)?nèi)容和結(jié)論如下:1、本文對(duì)苜蓿植株及種莢的物理特性與空氣動(dòng)力學(xué)特性進(jìn)行了試驗(yàn)研究。利用統(tǒng)計(jì)學(xué)原理建立了具有北方代表性品種的紫花苜蓿的物理力學(xué)特性與空氣動(dòng)力學(xué)特性的基礎(chǔ)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(jié)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(jìn)提供數(shù)據(jù)支撐。2、對(duì)9ZQ-2.7型苜蓿種子采集機(jī)的工作原理及采集頭的結(jié)構(gòu)進(jìn)行了系統(tǒng)研究。根據(jù)采集頭的結(jié)構(gòu)建立了三維CAD模型,利用前處理軟件對(duì)模型進(jìn)行了簡(jiǎn)化,并采用四面體單元進(jìn)行了網(wǎng)格的劃分;設(shè)置了 25個(gè)壓力進(jìn)口及1個(gè)壓力出口,建立了k-ε 標(biāo)準(zhǔn)湍流模型,采用速度壓力耦合SIMPLE算法;進(jìn)口處的壓力為標(biāo)準(zhǔn)大氣壓101325 Pa,出口處的壓力為101085 Pa,來(lái)模擬采集頭內(nèi)氣流場(chǎng)的分布。對(duì)仿真結(jié)果進(jìn)行分析,得到原結(jié)構(gòu)的進(jìn)口速度由左側(cè)區(qū)域Ⅰ往右側(cè)區(qū)域Ⅲ逐漸減小,而在調(diào)風(fēng)板處的速度出現(xiàn)波動(dòng);最左側(cè)的速度能達(dá)到15.7 m/s,右側(cè)的速度最小值為3.61 m/s,從而確定原結(jié)構(gòu)的速度分布均勻性差。3、在原有結(jié)構(gòu)的基礎(chǔ)上進(jìn)行了仿真分析與試驗(yàn),發(fā)現(xiàn)進(jìn)口處速度分布均勻性差。針對(duì)存在的問(wèn)題對(duì)原結(jié)構(gòu)進(jìn)行改進(jìn),設(shè)計(jì)了 20種改進(jìn)方案;對(duì)改進(jìn)方案依次進(jìn)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(jìn)行試驗(yàn)驗(yàn)證;對(duì)選擇的三種方案試驗(yàn)結(jié)果進(jìn)行比較分析,確定最優(yōu)方案為方案12,改方案的結(jié)構(gòu)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(hào)：1996364