水力旋流器流场大涡模拟及结构改进

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摘要

水力旋流器结构简单，应用广泛，但其内部流场的流动却相当复杂，还需要

多方面的研究和探索。有关水力旋流器工程应用的数值研究大都会选用占用计算

资源较少的 κ-ε湍流模型，可以得到定性的分析结果；学术研究大都选用雷诺应力

模型(Reynolds stress model, RSM)，主要考虑 RSM 模型中湍流粘度为各项异性，更

符合实际过程；大涡模拟(Large-eddy simulation)虽具有更高的计算精度，但因为需

要很大的计算资源而较少使用。本文将采用大涡模拟方法结合两相流模型模拟水

力旋流器内流场，以期通过局部流动的特点，指导改进水力旋流器的结构以及调

整合适的运行参数。探索大涡模拟方法在水力旋流器设计方面的有效性及可行性。

首先本文对比了雷诺时均方法的 RNG κ-ε (Renormalization κ-ε)模型、RSM

(Reynolds Stress Model)模型和大涡模拟方法的 Smagorinsky-Lilly 亚格子模型，选

择优秀的模型作为后续研究的湍流模型。通过对比速度压力分布与经验公式，拟

合径向速度分布曲线与理论曲线，对比压力降与理论公式的匹配程度等方法得到

的分析结果，一致认为大涡模拟方法准确性较高，可以得到水力旋流器内精准的

速度、压力等分布场。

其次本文使用湍流大涡模拟方法结合 VOF 两相流模型，捕捉水力旋流器中的

局部流动结构（空气柱、循环流、短路流等等）。研究表明模拟结果与大量实验事

实的吻合程度较好，并且得到空气柱运动的规律，循环流，短路流，轴向零速包

络面之间的关系等，以及实验中无法测得的现象。

最后本文分析了大涡模拟方法捕捉到的局部流动现象，结合流体力学相关理

论知识和水力旋流器的设计理论，针对不合理现象提出改进结构。将改进后结果

与原始结果对比，表明原始结构中不合理的流动现象得到了改进，水力旋流器内

部流动更加合理；为验证水力旋流改进前后分离效率是否真正得到提高，本文还

采用RNG κ-ε结合Eulerian模型模拟水力旋流器沉砂口的粒径分布，结果表明改进

后结构的切割粒径d50减小，大于d50颗粒分级效率提高，小于d50

综合以上研究，表明大涡模拟方法准确性较高，可以得到精准的速度、压力

等分布场，使得数值模拟结果更加真实可行，更具说服力。湍流大涡模拟方法可

以有效的捕捉水力旋流器内局部流动现象，成为指导水力旋流器结构改进有效的

数值模拟工具，以及大涡模拟方法在指导水力旋流器结构改进优化方面的潜力与

可行性。同时说明大涡模拟方法捕捉水力旋流器局部流动现象，结合流体力学理

论及实验经验公式提出改进方法的技术路线是有效可行的。

颗粒分级效率降低，

整体分布表明分离效率得到较大的提高。

关键词：水力旋流器；大涡模拟；VOF；欧拉-欧拉；空气柱；循环流短路流；轴

向零速包络面

ABSTRACT

Hydrocyclone is a widely used machinery, whose structure is simple, however its

internal flow field is quite complex. More research and exploration is needed for

engineering and science. κ-ε turbulence model required less computation resources is

employed in most numerical simulations for engineering applications of hydrocyclone,

with which qualitative results are usually obtained; Reynolds stress model (RSM) is

employed in most numerical academic research of hydrocyclone for its consideration of

non-homogeneous Reynolds stresses; Large Eddy Simulation (LES) is deemed to be a

more accurate methodology than other turbulence models for hydrocyclone flow, but it

requires large amount of computing resources. In the present work, LES method

combined with two-phase flow model will be employed to simulate the internal flow of

hydrocyclone, and then based on the simulated characteristics of the local flow structure

improvement will be conducted.

First of all, three models, the RNG κ-ε (Renormalization κ-ε) model and RSM

(Reynolds Stress Model) of Reynolds Average Navier-Stokes (RANS) methods, LES

(Large-eddy simulation) with Smagorinsky-Lilly subgrid model are compared to find

the best turbulence modeling for further study. By comparing pressure and speed

distribution with experiment results, fitting the radial velocity curve with the theoretical

curve obtained, comparing pressure drop with theoretical formula, it is found that the

large eddy simulation is the most accurate of the three modeling methods, with which

much more accurate velocity and pressure distribution of hydrocyclone can be

obtained .

LES (large eddy simulation) analysis has been carried out to investigate the flow

fields in a hydrocyclone. Detailed flow structures and phenomena such as shortcut flow,

internal circulations, locus of zero vertical velocity (LZVV) and locus of maximum

tangential velocity (LMTV), were analyzed. The study shows that the simulation results

are in best agreement with the published experiments. Some interesting phenomena

such as shortcut flow, circlation flow, LZVV and LMTV have been investigated that are

difficult to be found with experimental methods.

Modification and improvement of the cyclone internal structures was conducted

based on the detailed flow structure and phenomenon combined with theories of

hydrocyclone design and fluid mechanics. The further LES analysis shows that

compared with original cyclone, the flow fields in the modified one are obviously

improved, which implies that a better liquid-solid separation can be expected. In order

to prove this conclusion, RNG κ-ε with Eulerian multiphase model was adopted to

simulate the particle diameter distribution at underflow outlet. The modified cyclone

was found to be with obviously better performance.

According to the above research, numerical simulation results show that more

precise, more convincing velocity, pressure distribution can be obtained with large eddy

simulation method. The present work proves that a detailed flow analysis based on LES

may significantly improve hydrodynamic designs of cyclones. LES can effectively

capture the local detailed flow phenomena of hydrocyclone. Detailed analyses on the

flow fields in the cyclone can be very helpful to improve hydrocyclone design.

Keyword: Hydrocyclone, Large-eddy simulation, VOF, Eulerian-Eulerian

multiphase model, air core, shortcut flow, LZVV

摘要

ABSTRACT

第一章绪论 .................................................................................................................... 1

1.1 概况 ...................................................................................................................... 1

1.2 国内外研究现状 .................................................................................................. 2

1.3 研究目的和意义 .................................................................................................. 6

1.4 课题研究的内容与思路 ...................................................................................... 8

1.4.1 研究内容及步骤 ......................................................................................... 8

1.4.2 研究思路 ..................................................................................................... 9

第二章基本概念与理论 ............................................................................................... 11

2.1 水力旋流器原理介绍 ......................................................................................... 11

2.2 基本流场分析 ..................................................................................................... 11

2.2.1 旋转流动 ................................................................................................... 12

2.2.2 自由涡 ....................................................................................................... 13

2.2.3 强制涡 ....................................................................................................... 14

2.2.4 组合涡 ....................................................................................................... 15

2.3 局部细节流动介绍 ............................................................................................ 18

2.3.1 内旋流与外旋流 ....................................................................................... 18

2.3.2 空气柱 ....................................................................................................... 19

2.3.3 短路流 ....................................................................................................... 19

2.3.4 循环流 ....................................................................................................... 20

2.3.5 最大切线速度轨迹面（LMTV） ........................................................... 20

2.3.6 轴向零速包络面（LZVV） .................................................................... 21

2.4 水力旋流器分级效率 ........................................................................................ 21

2.5 本章小结 ............................................................................................................ 22

第三章数值计算方法 .................................................................................................. 24

3.1 数值计算方法简介 ............................................................................................ 24

3.1.1 计算流体力学介绍 ................................................................................... 24

3.1.2 数值计算方法的步骤 ............................................................................... 24

3.1.3 数值计算的离散方法 ............................................................................... 25

3.1.4 数值计算方法的局限性 ........................................................................... 26

3.2 湍流运动与非线性输运方程（N-S 方程） .................................................... 27

3.3 湍流的数值方法介绍 ........................................................................................ 28

3.3.1 直接数值模拟方法(DNS) ........................................................................ 28

3.3.2 大涡模拟方法(LES) ................................................................................. 29

3.3.3 雷诺平均方程方法(RANS) ..................................................................... 29

3.3.4 湍流数值方法的基本特点对比 ............................................................... 30

3.4 两相流模型介绍 ................................................................................................ 30

3.4.1 研究两相流的方法 ................................................................................... 30

3.4.2 两相流模型对比 ....................................................................................... 31

3.4.3 两相流模型选择 ....................................................................................... 32

3.5 VOF 模型基本思想与控制方程 ........................................................................ 33

3.5.1 VOF 模型基本思想 ................................................................................... 33

3.5.2 VOF 模型控制方程 ................................................................................... 33

3.6 网格技术 ............................................................................................................ 34

3.6.1 结构与非结构网格 ................................................................................... 34

3.6.2 网格软件介绍 ........................................................................................... 35

3.7 本章小结 ............................................................................................................ 36

第四章大涡模拟方法与雷诺时均湍流模型的对比 .................................................. 37

4.1 引言 .................................................................................................................... 37

4.2 大涡模拟方法（LES） ..................................................................................... 37

4.2.1 控制方程 ................................................................................................... 37

4.2.2 亚格子模型 ............................................................................................... 38

4.2.3 LES 方法的网格与计算条件 .................................................................... 39

4.2.4 LES 方法边界条件及初始条件 ................................................................ 40

4.2.5 LES 方法数值算法设置 ............................................................................ 40

4.3 雷诺平均方法（RANS） ................................................................................. 41

4.3.1 控制方程 ................................................................................................... 41

4.3.2 重整化群 κ-ε模型（RNG κ-ε） .............................................................. 41

4.3.3 雷诺应力模型（RSM） .......................................................................... 43

4.3.4 RANS 方法的网格与计算设置 ................................................................ 44

4.4 物理模型 ............................................................................................................ 44

4.5 速度场分析 ........................................................................................................ 45

4.5.1 切线速度分布对比 ................................................................................... 46

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摘要：

摘要水力旋流器结构简单，应用广泛，但其内部流场的流动却相当复杂，还需要多方面的研究和探索。有关水力旋流器工程应用的数值研究大都会选用占用计算资源较少的κ-ε湍流模型，可以得到定性的分析结果；学术研究大都选用雷诺应力模型(Reynoldsstressmodel,RSM)，主要考虑RSM模型中湍流粘度为各项异性，更符合实际过程；大涡模拟(Large-eddysimulation)虽具有更高的计算精度，但因为需要很大的计算资源而较少使用。本文将采用大涡模拟方法结合两相流模型模拟水力旋流器内流场，以期通过局部流动的特点，指导改进水力旋流器的结构以及调整合适的运行参数。探索大涡模拟方法在水力旋流器设计方...

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