界面特性对二次水滴产生的影响研究

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摘要

大型火电厂中的汽轮机低压缸的后几级以及压水堆核电机组的大部分级都

在湿蒸汽区内运行。湿蒸汽在高速流动膨胀时凝结形成的尺寸较小的一次水滴，

部分一次水滴沉积在静动叶栅上形成水膜后在气流作用下在叶片尾缘破碎而形成

的尺寸较大的二次水滴。二次水滴的质量大，惯性也大，因此与主汽流的跟随性

差，是造成汽轮机动叶片水蚀的直接原因，严重影响汽轮机运行的安全性。由此，

开展蒸汽轮机内二次水滴问题的研究意义重大。

文章第一部分制作了四组具有不同规则微观结构、粗糙度由 1.2 到2.0 的粗糙

表面，并测量了各个粗糙表面的表观接触角。而后将各组粗糙表面的接触角测量

值与 Wenzel 模型预测值和 Cassie 模型预测值进行比较，分析了影响各个粗糙表面

浸润特性的因素，并提出了新的接触角预测模型。相对于孔状结构，柱状结构更

容易得到较大的接触角，具有更好的超疏水性。对于孔状粗糙表面，液滴难以侵

入微结构内部，且相对柱状表面，具有更稳定的疏水性能，此特性在设计制造超

疏水表面及其实际应用中具有重要意义。

文章第二部分首先总结了国内外二次水滴冲蚀试验装置的研究进展情况，现

有的试验装置主要分为四类：转盘式、振动式、高温气流冲击式及高速水柱撞击

式，其中以高速水柱撞击式效果较好。其次完成了二次水滴试验台的方案设计，

试验了三种方案，最终选取叶片小孔渗水形成二次水滴的方案。接着完成了二次

水滴试验台的总体设计及搭建，二次水滴的试验台主要分为三部分：水路部分，

气路部分及光路（图像采集）部分。最后对该试验台进行了验证，结果显示该试

验台可以很好完成既定试验目标。

文章的第三部分首先介绍了研究固-液界面张力对于二次水滴影响的试验方

法，亲水和超疏水界面特性的试样叶片的选择和试制，试验条件的确定，试验过

程的介绍。此外还介绍了像素标定的过程。最后通过图像法处理并分析了试验数

据。结果发现试样叶片通过亲水处理之后形成的二次水滴粒径有所减小，其脱流

尾迹的长度较长、分支较多，有利于高速气流撕裂液体，导致液体充分被气流雾

化，形成尺寸较小的二次水滴。较小的粒径使得二次水滴易被高速气流携带加速，

有利于减小二次水滴对下级动叶片的冲蚀破坏。

关键字：汽轮机二次水滴界面特性超疏水

ABSTRACT

The steam, flowing in the last several stages of the LP cylinder of steam turbines

at power plants and the most of the stages of pressurized water reactor nuclear power

plant, exhausts to the condenser as a two-phase mixture of saturated steam and small

liquid droplets. Some small liquid droplets are deposited at the pressure surfaces of

cascades and form water films. On the trailing edge, water films are broken into some

larger liquid droplets by steam flow. Because of inertia, these larger liquid droplets can’t

follow primary steam flow and impact on the next cascades, leading to steam turbine

water erosion. It seriously affects the safety operation of steam turbine. Therefore, it is

greatly significative to investigate the water erosion in steam turbines.

There are three parts in the whole thesis. Four groups of rough surfaces with

regular microstructures have been made in the first part of the article. Every group

includes nine pieces of surface with roughness from 1.2 to 2.0.The true contact angle

(CA) has been measured and compared with theoreticalvaluecalculated by Wenzel

Model and Cassie Model to find out the elements which affect the wetting behavior of

every rough surface. It is discovered that difference of extent which liquid intrudes into

microstructures in is the main reason which causes the different wetting behavior. A new

predictor formula has been given out on these rough surfaces with two kinds of different

microstructures. Relative to rough surfaces with cavernous microstructure,

contactangles of rough surfaces with cavernous microstructure are larger. It is hard for

liquiddrop to intrudeinto the microstructure of rough surfaces with cavernous

microstructure. It is useful that stability of hydrophobicity of rough surfaces with

cavernous microstructure is better.

The second part of the article introduces the research progress of secondary water

droplet erosive testing device, and then completes selection of scheme of secondary

water droplet testing device. This testing device contains three parts：waterway part, gas

path part and optical unit(image acquisition part). At last, it has been verified that this

testing device can achieve the established test target.

The third part of the article introduces experimental method how to research the

effect to the formation of secondary droplets by solidliquidinterphase and manufactures

sample blades with different surfacecharacteristics.And then, this part also introduces

experimentcondition and experimental process. At last, experimentaldata has been

handled analyzed by Matlab software.The results showed particalsizes of secondary

droplets broken from the sample blades which are handled into hydrophilic surface are

smaller than these common blades. The wakes of hydrophilic sample blades with

several branches are longer. It is conducive for stream to tear the liquid and form

smaller secondary droplets. Because of smaller particalsizes, it is easy for airflow

carrying secondary droplets. All above help reduce water erosion damage to the next

blade.



Keywords: steam turbine, secondary droplet, interface behavior,

super-hydrophobic

摘要

ABSTRACT

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

1.1 课题的背景和意义 ................................................................................................ 1

1.2 汽轮机中水蚀现象 ................................................................................................ 2

汽轮机内湿蒸汽两相流的形成过程

1.2.1 .............................................................. 2

汽轮机内湿蒸汽两相流的水滴种类及特性

1.2.2 .................................................. 3

湿蒸汽两相流的产生对汽轮机性能的影响

1.2.3 .................................................. 3

水蚀问题国内外研究进展

1.3 ..................................................................................... 5

水蚀问题的解决方法

1.4 ............................................................................................. 6

主动防护措施

1.4.1 ................................................................................................. 6

1.4.2 被动防护措施 ................................................................................................ 8

论文的研究内容和主要工作

1.5 ................................................................................. 8

第二章水蚀现象的理论基础 ...................................................................................... 10

2.1 形成水蚀的原因 .................................................................................................. 10

影响水蚀的主要参数

2.2 ............................................................................................ 11

2.2.1二次水滴撞击叶片表面的速度 ..................................................................... 11

水滴尺寸

2.2.2 ......................................................................................................... 11

二次水滴的撞击角度

2.2.3 .................................................................................... 12

叶片材料的机械性能

2.2.4 .................................................................................... 12

叶片材料的表面性能

2.2.5 .................................................................................... 12

金相组织结构

2.2.6 ................................................................................................ 13

高速气流雾化液体机理

2.3 ....................................................................................... 13

一次及二次雾化机理

2.3.1 .................................................................................... 13

雾化现象的波动原理

2.3.2 .................................................................................... 14

汽轮机内二次水滴的雾化机理

2.3.3 .................................................................... 14

液滴冲蚀固体叶片机理

2.4 ....................................................................................... 15

本章小结

2.5 ............................................................................................................... 16

第三章界面特性的理论基础及试验研究 .................................................................. 17

界面特性的理论基础

3.1 ........................................................................................... 17

3.1.1 表面张力 ....................................................................................................... 17

固

3.1.2 -液界面 ....................................................................................................... 18

3.2 试验部分 .............................................................................................................. 21

具有规则微观结构的粗糙表面的设计及制备

3.2.1 ............................................ 21

试验仪器

3.2.2 ........................................................................................................ 23

试验方法

3.2.3 ........................................................................................................ 23

试验结果分析和讨论

3.3 ........................................................................................... 23

微观结构特征为柱形的粗糙表面

3.3.1 ................................................................ 23

微观结构特征为孔状的粗糙表面

3.3.2 ................................................................ 26

结论

3.4 ....................................................................................................................... 28

第四章二次水滴试验台设计与搭建 .......................................................................... 29

4.1 二次水滴试验装置综述 ...................................................................................... 29

二次水滴试验台总体设计

4.2 ................................................................................... 32

设计目标

4.2.1 ........................................................................................................ 32

试验台设计方案

4.2.2 ............................................................................................ 32

二次水滴试验台的组成

4.2.3 ................................................................................ 33

主要部分设计

4.3 ....................................................................................................... 34

风机系统

4.3.1 ........................................................................................................ 34

试验段管道及试样叶片设计

4.3.2 ........................................................................ 36

水路系统的设计

4.3.3 ............................................................................................ 38

水蚀试验台光路系统的设计

4.3.4 ........................................................................ 39

4.4 试验台的验证 ...................................................................................................... 40

4.5 本章小结 .............................................................................................................. 40

第五章试验 .................................................................................................................. 41

5.1 试验方法 .............................................................................................................. 41

不同界面特性的试样叶片的选择

5.1.1 ................................................................ 41

试验条件

5.1.2 ........................................................................................................ 44

试验过程

5.1.3 ........................................................................................................ 44

像素标定过程

5.2 ....................................................................................................... 45

试验结果

5.3 ............................................................................................................... 45

试样叶片边缘的脱流尾迹的形态

5.3.1 ............................................................... 45

二次水滴尺寸

5.3.2 ................................................................................................ 48

二次水滴的速度

5.3.3 ............................................................................................ 51

本章小结

5.4 ............................................................................................................... 52

第六章试验数据处理及分析 ...................................................................................... 53

试验数据图像处理

6.1 ............................................................................................... 53

图像预处理

6.1.1 .................................................................................................... 53

灰度图像分割

6.1.2 ................................................................................................ 55

图像的形态学处理

6.1.3 ........................................................................................ 57

图像二次水滴粒度分布统计

6.1.4 ........................................................................ 58

二次水滴尺寸数据处理结果

6.2 ............................................................................... 59

普通试验叶片的二次水滴粒径分布

6.2.1 ............................................................ 59

亲水试验叶片的试验结果

6.2.2 ............................................................................ 62

二次水滴平均粒径统计

6.2.3 ................................................................................ 65

二次水滴速度数据处理结果

6.3 ............................................................................... 66

试验处理结果分析

6.4 ............................................................................................... 67

二次水滴粒径及其分布的结果分析

6.4.1 ............................................................ 67

二次水滴速度的结果分析

6.4.2 ............................................................................ 68

本章小结

6.5 ............................................................................................................... 69

第七章结论与展望 ...................................................................................................... 70

主要结论

7.1 ............................................................................................................... 70

本文展望

7.2 ............................................................................................................... 70

主要符号 ........................................................................................................................ 72

参考文献 ........................................................................................................................ 73

在读期间公开发表的论文和承担科研项目及取得成果 ............................................ 78

致谢 .............................................................................................................................. 79

后记 .............................................................................................................................. 80

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摘要：

摘要大型火电厂中的汽轮机低压缸的后几级以及压水堆核电机组的大部分级都在湿蒸汽区内运行。湿蒸汽在高速流动膨胀时凝结形成的尺寸较小的一次水滴，部分一次水滴沉积在静动叶栅上形成水膜后在气流作用下在叶片尾缘破碎而形成的尺寸较大的二次水滴。二次水滴的质量大，惯性也大，因此与主汽流的跟随性差，是造成汽轮机动叶片水蚀的直接原因，严重影响汽轮机运行的安全性。由此，开展蒸汽轮机内二次水滴问题的研究意义重大。文章第一部分制作了四组具有不同规则微观结构、粗糙度由1.2到2.0的粗糙表面，并测量了各个粗糙表面的表观接触角。而后将各组粗糙表面的接触角测量值与Wenzel模型预测值和Cassie模型预测值进行比较，分析了...

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