基于超声法测量气固两相流颗粒相浓度研究

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3.0 赵德峰 2024-11-11 11 4 3.72MB 89 页 15积分
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摘要
气固两相流流动参数检测对于研究两相流流动过程以及工业生产过程的安全、
高效、经济运行均具有重要意义。超声法具有穿透性好，结构简单，无污染等自
身优势，可广泛用于不透光介质以及对环境要求较高场合。本课题针对超声法测
量气固两相流浓度问题进行了实验研究。
首先，设计并建立了一套超声法测量两相流颗粒相浓度实验系统。该系统分
为硬件和软件两部分，其中硬件部分主要包括超声波脉冲激励信号发射装置、信
号调理装置、高速数据采集卡(NI USB-5133)，测量实验段，空气耦合超声换能器
和电脑；软件部分则主要为利用 LabVIEW 语言开发的数据采集、信号处理程序和
颗粒粒径和浓度计算程序。
第二，针对气固颗粒两相体系的超声检测特点，结合长波区的简化 ECAH 模
型，实现了气固两相流中颗粒相的粒径和浓度的计算算法。利用建成的实验系统
结合颗粒重力输送实验装置，对于一种电站锅炉燃煤煤粉样品，在 100kHz 和
200kHz 的超声波频率下进行实验。为更好评价实验效果，将颗粒粒度实验结果与
图像粒度处理仪测量结果进行比较，结果数据较为吻合。测量浓度值与输送装置
给定值亦较接近。验证了该方法可以实现气固两相流固相颗粒浓度的在线测量。
第三，针对双频率超声法测量气固两相流时只能获取被测空间某一局部测量
区的平均浓度值这一弊端，开展了气固颗粒两相流的过程层析成像原理研究，其
核心为利用超声过程层析成像技术重现气固两相流颗粒相空间分布。研制了一套
基于透射模式超声层析成像系统，系统换能器阵列共有 8个换能器，均为自发自
收型换能器，且单个换能器发射的扇形波束角可达到 1500。针对超声过程层析成
像中需要实现换能器的一发多收，设计了专门的切换装置用于换能器发射/接收功
能的转换，提高系统实时性。通过选择高信噪比的信号调理装置和多通道同步采
集卡 PCI8501，基于 LabVIEW 图形化语言编写数据采集、处理程序，构建了多通
道信号同步采集系统。为实现图像重建，采用二值逻辑反投影算法，程序由
MATLAB 实现。软硬件结合组成了一套系统完整的层析成像系统，可以较好地实
现超声波投影信号产生，同步采集以及图像重建功能。
第四，为验证超声波层析成像实验系统性能，先后进行了静态和动态超声层
析成像试验。静态实验部分：实验对象为聚四氟乙烯棒，通过改变聚四氟乙烯棒
的尺寸大小和位置来模拟不同的气固两相流流动状况，利用换能器阵列同步测量
不同观察角下的超声波投影信号；将得到的投影数据利用改进的二值逻辑反投影
图像重建算法进行图像重建，获得成像截面的重建图像。对比截面重建图像与物
体实际分布情况，系统具有较好的成像精度。动态性能实验则是利用实验系统对
空气-煤粉两相流进行连续在线测量，并最终重建了煤粉的空间分布二维图像。结
果显示，系统可以反映出煤粉的空间位置分布，并在 1s 时间得到重建图像，满足
一定的实时性要求。由于图像重建算法采用的是二值逻辑反投影算法，系统并不
能得到颗粒相的绝对浓度值分布，而且对于流速较高、流态变化较快的两相流动，
系统实时性尚不能满足要求。
关键词：气固两相流，超声法，颗粒相浓度，超声层析成像
ABSTRACT
The on-line measurement of gas-solid flows parameters is of great importance for
understand the nature of two-phase flows and safety, economic operation of industrial
process. Compared with Several existing measurement methods, ultrasonic method has
advantages of strong penetrability, simple structure and environment-friendly. For more
information, experimental study of gas-solid flows concentration measurement by
ultrasonic method has been done in this paper.
First of all, it present a particle size and concentration measurement method based
on the principle of ultrasonic attenuation at two different frequencies. To prove the
effectiveness of the method, experiment system was designed and the system can be
divided into hardware and software. The hardware consists of pulse generator device,
signal processing device, high speed data acquisition card (NI USB-5133), transducers,
experimental vessel and computer et al. The software consists of data acquisition
program, Spectrum analysis program, particle size and concentration calculation
program. All of their programs were developed based on LabVIEW.
Second, as a theoretical basis, the simplified ECAH model in long-wavelength
range is employed to predict the attenuation. With the help of a gravity transport device,
experiments of air-coal flow are carried out to measure the particle mean size and
concentration, in which ultrasonic signal has been generated and receiver by transducers
with fixed frequencies of 100 and 200 KHz. The ultrasonic measurement results are
compared with image processing measurements and given concentrations, which show
that the present method possesses a good foreground for the on-line measurement of
particle concentration.
Third, double-frequency ultrasonic method can only get local concentration of the
measured particle two-phase flow and the 2D or 3D distribution of flow parameters
which characterize the measured two-phase flow, is often needed in many operation
conditions. Process tomography techniques can provide a 2D or 3D image of two-phase
flow over a cross-section of pipe with many advantages. The transmission-mode
ultrasonic process tomography system has been developed in this paper. The system
consisting of a sensor array with a high speed Date Acquisition Card (DAQ) and signal
processing devices with switching device. The sensor array contains 8 ultrasonic
transducers and each transducer can emit fan-shaped beams with angle as large as 150
degree. A personal computer is used for recording experimental data and communicates
with the other device as a host. By implementing a LabVIEW-based program it can
synchronously acquire the real-time data of 8 channels of the DAQ Cards (PCI8501),
where the multiple-channels switching device with Microprogrammed Control Unit
(MCU) is of utmost importance for real-time measurements. The system can work well
in one transmitting & multi-receiving mode in which the attenuated ultrasonic waves
from the transmitting transducer can be received by other transducers simultaneously.
Forth, a series of experiments have been done to test the system. At the first, a
PTFE rod is used to simulate high concentration solid particle and which different size,
different location represent different two-phase flow condition. The transducers array
can help get all projection information at different observe angle. The cross-section
image of sample vessel under investigation can be reconstructed using the improved
two-value logic back-projection algorithm with the projection data. Compare with
preset conditions, imaging accuracy is good. Finally, measured the particle
concentration of air-coal two-phase flow on-line used this system. From the
reconstruction image of the air-coal flow cross-section, the system can identify the
distribution of coal powder, but it can`t get accurate concentration distribution of coal
powder and the flow speed is limited.
Key words: Gas-solid two-phase flow, Ultrasonic method, Particle
concentration measurement, Ultrasonic process tomography
目录
摘要
ABSTRACT
第一章 绪论 ................................................................................................................. 1
§ 1.1 气固两相流检测的意义 ............................................................................... 1
§ 1.2 气固两相流测量面临的困难 ...................................................................... 2
§ 1.3 目前常见的气固两相流检测方法 .............................................................. 3
§ 1.3.1 差压法 ............................................................................................... 3
§ 1.3.2 热平衡法 ........................................................................................... 4
§ 1.3.3 光学法 ............................................................................................... 4
§ 1.3.4 电学法 ................................................................................................ 5
§ 1.3.6 超声法 ............................................................................................... 6
§ 1.3.7 层析成像法 ....................................................................................... 7
§ 1.4 本文的研究内容和章节安排 .................................................................... 9
§ 1.4.1 本文的主要研究内容 ........................................................................ 9
§ 1.4.2 本文的章节安排 ............................................................................... 9
第二章 超声法颗粒粒径和浓度测量理论 ................................................................ 11
§ 2.1 超声及产生过程 ......................................................................................... 11
§ 2.2 颗粒两相介质中的声衰减 ...................................................................... 12
§ 2.3 颗粒粒度、浓度测量理论模型 ................................................................. 15
§ 2.3.1 ECAH 理论模型 .............................................................................. 15
§ 2.3.2 “长波长”简化模型 ..................................................................... 17
§本章小结 ............................................................................................................ 19
第三章 气固两相流浓度测量系统及测量结果 ....................................................... 20
§ 3.1 硬件系统 .................................................................................................... 20
§ 3.1.1 超声换能器 ...................................................................................... 20
§ 3.1.2 超声换能器激励装置 ..................................................................... 22
§ 3.1.3 开关电路 ......................................................................................... 24
§ 3.1.3 超声波信号处理装置 ..................................................................... 26
§ 3.1.4 数据采集系统 ................................................................................. 29
§ 3.2 软件系统 ..................................................................................................... 30
§ 3.3 煤粉-空气两相流煤粉浓度实验 ................................................................ 32
§ 3.3.1 实验装置与方法 .............................................................................. 33
§ 3.3.2 实验结果与分析 ............................................................................. 35
§ 3.3.4 实验结论 ......................................................................................... 37
§ 本章小结 .......................................................................................................... 37
第四章 超声过程层析成像基础 ............................................................................... 38
§ 4.1 超声层析成像及其分类 ............................................................................. 38
§ 4.1.1 透射模式 UPT .................................................................................. 38
§ 4.1.2 衍射模式 UPT .................................................................................. 39
§ 4.1.3 反射模式 UPT .................................................................................. 40
§ 4.1.4 基于精确场描述的层析成像技术 .................................................. 41
§ 4.2 介质中的声传播及对应图像重建算法 ..................................................... 41
§ 4.2.1 几何声学近似 .................................................................................. 41
§ 4.2.2 二值逻辑反投影图像重建算法 ...................................................... 43
§ 4.2.3 改进二值逻辑反投影图像重建算法 .............................................. 44
§ 4.2.2 基于声传播波动理论 ...................................................................... 46
§ 4.3 超声层析成像技术面临的几大问题 ....................................................... 47
§本章小结 ............................................................................................................ 48
第五章 气固两相流 UPT 系统结构及设计 ............................................................. 49
§ 5.1 超声换能器阵列设计 ................................................................................ 49
§ 5.1.1 扫描方式的选择 ............................................................................. 50
§ 5.1.2 超声换能器的设计与制作 .............................................................. 51
§ 5.1.3 超声换能器的测试 .......................................................................... 53
§ 5.1.4 阵列换能器数目 ............................................................................. 54
§ 5.2 切换装置 .................................................................................................... 56
§ 5.3 其他硬件装置 ............................................................................................ 57
§ 5.3.1 脉冲发生接收仪 .............................................................................. 57
§ 5.3.2 声前置放大器 .................................................................................. 58
§ 5.3.3 多通道数据采集卡 .......................................................................... 59
§ 5.4 软件部分 .................................................................................................... 60
§ 5.4.1 多通道同步采集程序 ..................................................................... 60
§ 5.4.2 数据处理程序 .................................................................................. 60
§ 5.4.3 图像重建算法程序 ......................................................................... 61
§本章小结 ............................................................................................................ 61
第六章 气固两相流 UPT 系统性能的实验研究 ..................................................... 63
摘要：

摘要气固两相流流动参数检测对于研究两相流流动过程以及工业生产过程的安全、高效、经济运行均具有重要意义。超声法具有穿透性好，结构简单，无污染等自身优势，可广泛用于不透光介质以及对环境要求较高场合。本课题针对超声法测量气固两相流浓度问题进行了实验研究。首先，设计并建立了一套超声法测量两相流颗粒相浓度实验系统。该系统分为硬件和软件两部分，其中硬件部分主要包括超声波脉冲激励信号发射装置、信号调理装置、高速数据采集卡(NIUSB-5133)，测量实验段，空气耦合超声换能器和电脑；软件部分则主要为利用LabVIEW语言开发的数据采集、信号处理程序和颗粒粒径和浓度计算程序。第二，针对气固颗粒两相体系的超声检...

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作者：赵德峰 分类：高等教育资料 价格：15积分 属性：89 页 大小：3.72MB 格式：PDF 时间：2024-11-11

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