小型多流态浮选柱气液两相流场数值模拟与PIV测量.pdf

工程硕士学位论文 小型多流态浮选柱气液两相流场 数值模拟与 PIV 测量 Numerical Simulation and PIV Measurement on the Water-bubble Flow Field of A Laboratory Multi-flow Flotation Column 作 者孟诗淇 导 师闫小康 副教授 中国矿业大学 二〇一九年四月 万方数据 学位论文使用授权声明学位论文使用授权声明 本人完全了解中国矿业大学有关保留、使用学位论文的规定，同意本人所撰 写的学位论文的使用授权按照学校的管理规定处理 作为申请学位的条件之一， 学位论文著作权拥有者须授权所在学校拥有学位 论文的部分使用权，即①学校档案馆和图书馆有权保留学位论文的纸质版和电 子版，可以使用影印、缩印或扫描等复制手段保存和汇编学位论文；②为教学和 科研目的，学校档案馆和图书馆可以将公开的学位论文作为资料在档案馆、图书 馆等场所或在校园网上供校内师生阅读、浏览。另外，根据有关法规，同意中国 国家图书馆保存研究生学位论文。 （保密的学位论文在解密后适用本授权书） 。 作者签名 导师签名 年 月 日 年 月 日 万方数据 中图分类号 TQ051.1 学校代码 10290 UDC 621 密 级 公开 中国矿业大学 工程硕士学位论文 小型多流态浮选柱气液两相流场 数值模拟与 PIV 测量 Numerical Simulation and PIV Measurement on the Water-bubble Flow Field of A Laboratory Multi-flow Flotation Column 作 者 孟诗淇 导 师 闫小康 申请学位 工程硕士 培养单位 化工学院 学科专业 动力工程 研究方向 过程装备流体动力学 答辩委员会主席 评 阅 人 二〇一九年四月 万方数据 致谢致谢 岁月如梭，韶光易逝。转瞬间，硕士生涯，即近尾声。重回首时，有太多的 人需要感谢。首先要感谢我的导师闫小康，大学生涯伊始，即对我有知遇之恩， 是我在研究道路上的启蒙者，引领我踏入心之所向的学术世界。在中国矿业大学 求学的六年间，她都给予了我悉心的指导和无微不至的关怀。闫小康老师在学术 上学识渊博，思维缜密，对待研究一丝不苟；在生活中平易近人，对学生关怀备 至。无论是指导学术研究还是教育待人接物都做到了一个好导师该做的，师从数 载，终身受益，感激之情，溢于言表。毕业之际，谨向我敬爱的导师闫小康致以 衷心的感谢和崇高的敬意 感谢电力工程学院王利军教授多年来在研究工作、 做人做事的许多方面悉心 指导，他平易近人的做人风格和严谨开拓的研究态度更是深深影响着我，许多朴 实而又深刻的教诲我将铭记终生。 感谢王爱博士、石瑞硕士、刘煜硕士、陈朱应硕士、李晓恒博士、郑恺昕博 士、王帅杰硕士在我读研的道路上给予的指导和关怀，让我在课题研究中少走了 许多弯路，更让我懂得了师兄师姐这个称呼的意义。 感谢粟文兵硕士、李娟硕士在生活与学习中的陪伴，是他们让我的研究生生 活更加的有趣，与他们的友情让我终生难忘。 感谢苏子旭硕士、杨涵曦硕士在许多工作上的协助，做出更多的成果。 感谢本论文中被引文献及著作的作者，感谢他们的付出。 感谢我的父母，是他们在背后默默的付出，让我有机会得以继续深造，感谢 他们一直以来的支持和鼓励。同时也要感谢我的女友，她的出现给我的生活与未 来增添了色彩。 最后，感谢在百忙之中抽出时间审阅本论文的各位专家和学者，不弃作者学 术浅薄，对于文中的不当之处，敬请批评指正 万方数据 I 摘摘 要要 旋流-静态微泡浮选柱（FCSMC）是矿物加工工业中的一种过程装备，用来 实现对细粒矿物的分离，现已成功应用于金属、非金属矿物分选及油水分离等领 域。该分离设备内部流态与常规浮选柱相比较为复杂，包含有旋流、逆流和管流 等多种流态，流场特性对其分选性能尤为重要。计算流体动力学（CFD）数值模 拟技术和激光粒子测速技术（PIV）测量技术飞速发展，成为了流体力学的主要 研究手段。然而受限于流态的复杂性，从该分选设备发明伊始到目前的工业化推 广，针对其展开的流体动力学研究虽然一直在进行，但是无论是实验测量还是数 值模拟都仍然不够完善和准确，无法全面反映其复杂的多相流场特性，影响了我 们通过对流场的深入探究进而改善其分选环境，制约了分选性能提高。以小型实 验室多流态浮选柱为研究对象， 针对实验测量和数值研究中存在的问题开展了单 相和两相的 PIV 测量和数值模拟研究，主要研究成果及内容包括以下几个方面。 搭建了 PIV 复杂流态测量平台， 借助内窥镜技术， 解决了常规 PIV 技术无法 测量横截面流动的问题， 完善了 PIV 对复杂流态的测量方法， 获得了浮选柱内部 完整的切向、 径向和轴向速度及其分布规律。 为测量旋流流态最重要的切向速度， 进行了切向速度测量的实验研究，在常规 PIV 实验的基础上，采用 CCD 相机与 内窥镜结合的方法，选取 0.25 m3/h、0.50 m3/h、1.00 m3/h 和 1.50 m3/h 四种循环 流量进行了柱体内部不同截面上速度分量的测量。测量结果表明，在 4 种循环流 量下，流体的轴向、径向和切向速度分别在-0.08 m/s 至 0.08 m/s、0 至 0.2 m/s、 0 至 0.35 m/s 之间，柱体内流动以切向运动为主；在距离旋流倒锥以上 300mm 处（约 1.5 倍直径） ，轴向速度呈现“√”形分布，轴心处流体向上运动，沿着半 径方向速度迅速降低至0后开始向下运动并再缓慢减小直至0后又开始向上运动 直至壁面，存在两个 0 速度点，在柱体内部轴向上存在两个方向相反的涡；径向 上表现为离心运动，从轴心到壁面缓慢减小；切向速度沿着半径先迅速增大后缓 慢降低；随着循环流量增大，三个速度分量的值均增大。 确立了适用于计算 FCSMC 旋流场的湍流模型。利用较为完整的浮选柱单相 流场 PIV 实验测量数据，对旋流场湍流模型进行了可靠性验证，包括有 Standard k-ɛ、RNG k-ɛ、Realizable k-ɛ、RSM 四种湍流模型分别进行了 CFD 数值模拟， 结果表明 RSM 模型计算结果与实验吻合最好，可以准确预测切向、径向和轴向 速度在径向上的分布趋势，且速度平均误差低于 15。而以往模拟中使用的 k-ɛ 双方程模型中，只有 Realizable k-ɛ 能预测轴向速度的趋势，但误差达到 78， 其余径向速度和切向速度的预测误差均接近 30。 搭建了多流态浮选柱的气-液两相 PIV 测试平台，利用分光分波段技术实现 万方数据 II 了浮选柱内部复杂流态下气-液两相的同步测量。完成了循环流量为 1.00 m3/h 和 1.50 m3/h 时，旋流倒锥以上 200 mm 和 400 mm 的高度处的两相 PIV 测量。结果 表明实验中气泡粒径主要集中于 1mm 处，气含率约 1；两相流测量液相速 度与单相流测量结果在轴向速度和径向速度的分布趋势上一致， 单相流测试能且 仅能在一定程度上代表浮选柱内部液相流场的运动特性。 柱体内部气液两相的流 动特征表现为气相进入柱体后螺旋上升运动，在测量范围内，循环流量越大， 高度越低，气相的轴向、径向和切向速度越大；在径向上，气相和液相都是离心 运动，轴心处速度最大，之后径向速度缓慢减小直至壁面处速度接近零；切向速 度气相和液相同向旋转，在轴心处接近零，沿着半径方向迅速增大，到达最大值 后缓慢下降直至壁面。 建立了准确性较高的多流态浮选柱气-液两相流 CFD 数值模型。对使用的两 相流模型、湍流模型和相间作用力模型实施了循环流量为 1.00 m3/h 和 1.50 m3/h 工况的“数值实验”，通过与 PIV 气-液两相流测量数据对比，结果表明欧拉两 相流模型、 RSM 湍流模型及 Tomiyama 曳力模型对小型多流态浮选柱内气液两相 流场预测能力最好，尤其在预测气泡的轴向速度上，误差为 12.277，比原有模 型的预测误差降低了 18。 探明了小型多流态浮选柱内部流场气液两相流动特性。液相水从倒锥处的切 向进口进入浮选柱内，在靠近边壁处螺旋向上运动，靠近轴线处螺旋向下，一部 分从中矿出口离开浮选柱，另一部分沿着轴线形成小直径的螺旋上升流；随着循 环流量增大，流动速度增大；随着测量位置的增高，径向离心和切向旋流的趋势 及其速度均减小，外层的上升、下降螺旋流动速度减缓，而轴线处的小直径螺旋 上升流的上升速度逐渐增大。气相气泡从倒锥段的切向进口进入浮选柱，在旋流 场的作用下螺旋上升，并且向中心聚集，抵达浮选柱顶端气-水界面离开；随着 循环流量增大，轴向、径向、切向速度均增大；在旋流场的作用下，气泡向轴心 聚集成气泡柱，沿着半径方向向外其气含率逐渐降低。 该论文有图 55 幅，表 17 个，参考文献 91 篇。 关键词关键词CFD 数值模拟；PIV 测试；气液两相流；浮选动力学 万方数据 III Abstract The cyclone-static microbubble flotation column has significant advantages in fine-grain mineral sorting, and its internal flow state is more complicated than conventional flotation columns. Flow field characteristics are especially important for its sorting perance. In recent years, computational fluid dynamics numerical simulation technology and PIV measurement technology have developed rapidly and become the main for studying flow field. However, due to the complexity of the flow, the research of the flow field has been carried out from the beginning of the invention to the current industrialization. But, neither the experimental measurement nor the numerical simulation is far from perfect and accurate, and it cannot reflect its complex multi-phase flow field characteristics, which affects our in-depth study of the flow field to improve its sorting environment and restrict its sorting perance. In this paper, we take small multi-fluid flotation column as the research object. Single-phase and two-phase PIV measurements and numerical simulation studies were carried out on the problems existing in the previous studies. The main research results and contents include the following aspects. The PIV complex flow measurement plat was built. The endoscopic technology was used to solve the problem that the conventional PIV technology could not measure the cross-section flow. Therefore, we designed an experimental scheme for tangential velocity measurement using a combination of a CCD camera and an endoscope with fluxes of 0.25 m3/h, 0.50 m3/h, 1.00 m3/h, and 1.50 m3/h. The measurement results show that the axial, radial and tangential velocities of the fluid are between -0.08 m/s and 0.08 m/s, 0 to 0.2 m/s and 0 to 0.35 m/s at four circulating flow rates. Therefore, the flow in the column is dominated by tangential motion. At a distance of 300 mm about 1.5 times the diameter above the swirling inverted cone, the axial velocity exhibits a “√“-shaped distribution, and the fluid at the axial center moves upward. The axial velocity decreases rapidly along the radial direction to zero and then begins to move downwards and then slowly decreases to zero, following a movement up again up to the wall. There are two zero velocity points indicating that there are two opposite vortices in the axial direction inside the cylinder. It acts as a centrifugal motion in the radial direction, slowly decreasing from the axis to the wall. The tangential velocity increases rapidly along the radius and then slowly decreases. As the circulating flow rate increases, the values of the three velocity components 万方数据 IV increase. A turbulence model suitable for calculating the FCSMC cyclone field was established. The turbulence model of the cyclone field was verified by the relatively complete PIV experimental data of single-phase flow field, including the four turbulence models of Standard k-ɛ, RNG k-ɛ, Realizable k-ɛ and RSM. The results show that the RSM model has the best agreement with the experiment, and can accurately predict the distribution trend of tangential, radial and axial velocity in the radial direction, and the average velocity deviation is close to 15. Only Realizable k-ɛ can predict the axial velocity, but the deviation is 78. The prediction deviation of the remaining radial velocity and tangential velocity are both close to 30. A gas-liquid two-phase PIV measurement plat with multiple fluid flotation columns was built. Simultaneous measurement of gas-liquid two phases in a complex flow state inside a flotation column is realized by using the split-band sub-band technology. A two-phase PIV measurement at a height of 200 mm and 400 mm above the swirling inverted cone was achieved with a circulating flow of 1.00 m3/h and 1.50 m3/h. The results show that the bubble size in the experiment is mainly concentrated at 1mm, and the gas content is about 1. The two-phase flow measurement liquid phase velocity is consistent with the single-phase flow measurement result in the axial velocity and radial velocity distribution trends. The single-phase flow test can and can only represent to some extent the motion characteristics of the liquid phase flow field inside the flotation column. The flow characteristics of the gas-liquid two phases inside the cylinder are as follows the spiral gas rises after the gas phase enters the cylinder. Within the measurement range, the greater the circulating flow rate, the lower the height and the greater the axial, radial and tangential speeds of the gas phase. In the radial direction, both the gas phase and the liquid phase are centrifugal, and the velocity at the axis is the largest, after which the radial velocity is slowly reduced until the velocity at the wall is close to zero. The tangential velocity of the gas phase and the liquid rotate in the same direction, approaching zero at the axial center, rapidly increasing along the radial direction, reaching a maximum value and then slowly descending to the wall surface. A CFD numerical model for accurately calculating the gas-liquid two-phase flow of a multi-fluid flotation column was established, including the Eulerian two-phase flow model, the RSM turbulence model and the tomiyama drag model. By comparing with the PIV gas-liquid two-phase flow measurement data, the results show that the 万方数据 V tomiyama drag model has the best predictive ability for the gas-liquid two-phase flow field in the small multi-fluid flotation column, especially in predicting the axial velocity of the bubble. The deviation is 12.277, which is 18 lower than the original model. Using the established two-phase flow numerical model, the numerical simulation of the internal flow field of the small multi-fluid flotation column under different working conditions is completed, and the comprehensive flow field ination is obtained. The results show that the two-phase flow field inside the small multi-fluid flotation column has the following characteristics. The clean water flows from the tangential inlet at the inverted cone into the flotation column and spirals up along the wall surface, and reaches the gas-water interface at the top of the flotation column, and then spirals downward. Then it passes through the inverted cone and continues to rotate downwards to the middle port next to the wall of the lower column. A part of the water flows out from the mine outlet, and another part of the water spirals up along the axis of the flotation column under the action of the flower baffle, passing through the inverted cone section and finally reaching the gas-water interface at the top of the flotation column. As for the bubbles, they tangentially enter from the inverted cone, and under the action of the gravity field and the swirling force to the heart field, they gather toward the center and rotate up to the top of the flotation column to leave the flotation column at the gas-water interface. Keywords CFD numerical simulation; PIV measurement; gas-liquid two-phase flow; flotation kinetics 万方数据 VI 目目 录录 摘摘 要要............................................................................................................................ I 目目 录录......................................................................................................................... VI 图清单图清单........................................................................................................................... X 表清单表清单.......................................................................................................................XIV 变量注释表变量注释表 ..............................................................................................................XVI 1 绪论绪论............................................................................................................................. 1 1.1 课题研究背景与意义 .............................................................................................. 1 1.2 文献综述 .................................................................................................................. 1 1.3 存在的问题 .............................................................................................................. 6 1.4 研究目的 .................................................................................................................. 6 1.5 研究内容与技术路线 .............................................................................................. 7 1.6 本章小结 .................................................................................................................. 8 2 气液两相流数值模拟理论气液两相流数值模拟理论 ........................................................................................ 9 2.1 多相流模型 .............................................................................................................. 9 2.2 湍流模型 ................................................................................................................ 11 2.3 相间作用力模型 .................................................................................................... 13 2.4 本章小结 ................................................................................................................ 14 3 小型浮选柱内部单相流场小型浮选柱内部单相流场 PIV 测量测量 ..................................................................... 16 3.1 实验装置 ................................................................................................................ 16 3.2 轴截面的 PIV 测量 ............................................................................................... 18 3.3 横截面的 PIV 测量 ............................................................................................... 23 3.4 本章小结 ................................................................................................................ 28 4 小型浮选柱内部气液两相流场小型浮选柱内部气液两相流场 PIV 测量测量 ............................................................. 30 4.1 PIV 两相测量原理及装置 .................................................................................... 30 4.2 轴截面的 PIV 测量 ............................................................................................... 32 4.3 横截面的 PIV 测量 ............................................................................................... 39 4.4 本章小结 ................................................................................................................ 42 5 浮选柱内部单相流场数值模拟浮选柱内部单相流场数值模拟 .............................................................................. 44 万方数据 VII 5.1 三维模型 ................................................................................................................ 44 5.2 网格划分 ................................................................................................................ 45 5.3 数值模型 .............................................................................................................