电阻层析成像系统中的信号采集

电阻层析成像技术(Electrical Resistance Tomography,简称ERT)是一种可用于液-固,气-液两相流检测的一种高新测量技术.文章主要介绍ERT系统的概念与应用、ERT系统硬件构成、设计方案、器件选择,以及如何利用单片机C8051F040实现对传感器各模块功能的控制、A/D转换,从而完成对应用于ERT系统的微弱信号采集.     

一个简单实用的神经网络环状流参数估计器

环状流是一种典型的两相流.人们常用线性反投影法(LBP)对其进行快速成像.但由于该算法精度不高,本质上是一种定性算法,得到的效果不能令人满意.本文以电阻抗层析测量系统(ERT)中LBP法为研究对象,分析其存在的缺陷和产生缺陷的原因.针对理想环状流这一特定流型提出并建立一个基于BP神经网络的参数估计器来计算管道内含油区面积.仿真表明,对环状流使用该估计器能够获得较好的结果.     

电阻层析成像系统中等电势线电极传感器建模与仿真

本文根据电极传感器是等势体这一特性建立了一种新型的电流激励有限元线电极模型,真实的仿真了物理线电极模型。由得到的仿真结果表明,采用等势体线电极模型可以更细腻地反映实际传感器测量最敏感场域中的电场分布及其变化,有助于从理论上分析测量过程中,电流从流入电极到流出电极的空间分布规律,实现电阻层析测量系统中传感器的优化设计。     

基于双槽式孔板组合和神经网络技术的凝析天然气流量计开发

A slotted orifice has many superiorities over a standard orifice. For single-phase flow measurement, its flow coefficient is insensitive to the upstream velocity profile. For two phase flow measurement, various characteristics of its differential pressure （DP） are stable and closely correlated with the mass flow rate of gas and liquid. The complex relationships between the signal features and the two-phase flow rate are established through the use of a back propagation （BP） neural network. Experiments were carried out in the horizontal tubes with 50ram inner diameter, ooerated with water flow rate in the range of 0.2m^3·h^-1 to 4m3·h^-1, gas flow rate in the range of 100m^3·h^-1 to 1000m^3·h^-1, and pressure at 400kPa and 850kPa respectively, where the temperature is ambient temperature. This article includes the principle of wet gas meter development, the experimental matrix, the signal processing techniques and the achieved results. On the basis of the results it is suggested that the slotted orifice couple with a trained neural network may provide a simple but efficient solution to the wet gas meter development.     

基于RBF神经网络和粒子群算法的ECT传感器结构优化

给出一种RBF神经网络与粒子群算法相结合的电容层析成像（ECT）传感器结构参数优化方法。该方法以敏感场整体灵敏度大小等系统性能为优化目标,基于管壁厚度、屏蔽层厚度、径向屏蔽插入管壁深度、径向电极宽度、电极宽度（中心夹角）、管壁材料的相对介电常数、屏蔽层填充物相对介电常数7种重要的结构参数进行试验。应用RBF神经网络对多组结构参数以及对应的系统性能指标进行学习,得到回归模型,并应用粒子群算法进行寻优。结果显示,该方法参数寻优范围大,局限性小,寻优过程收敛快。优化后的系统整体灵敏度增大,成像质量改进。     

基于Web Service的通用测控系统

以WebService技术为基础,将C／S（Client／Server）、B／S（Browser／Server）分布式网络模型应用于实验室通用测控系统,设计具有多层结构的网络测控模型。通过对用户的安全认证,多用户的数据并发访问控制以及远端机器的访问控制等,构建高效率、坚固、安全的网络分布式测控平台。     

用图像相关系数和图像方差分析电阻层析测量反演算法的性能

根据不同两相流流型下获得的电阻抗层析测量结果,用图像相关系数和图像方差两个技术参数分别考察了线性反投影算法(LBP)、改进牛顿-拉夫逊类算法(MNR)、基于遗传算法的LBP-MNR-GA组合算法的反演能力.仿真表明,LBP对简单流型有较快和较好的反演能力,MNR反演复杂流型的能力比LBP强,LBP-MNRGA组合算法的反演能力最强.     

基于流体诱发振动的非接触式湿气流流型识别(英文)

A novel noninvasive approach, based on flow-induced vibration, to the online flow regime identification for wet gas flow in a horizontal pipeline is proposed. Research into the flow-induced vibration response for the wet gas flow was conducted under the conditions of pipe diameter 50 mm, pressure from 0.25 MPa to 0.35 MPa, Lockhart-Martinelli parameter from 0.02 to 0.6, and gas Froude Number from 0.5 to 2.7. The flow-induced vibration signals were measured by a transducer installed on outside wall of pipe, and then the normalized energy features from different frequency bands in the vibration signals were extracted through 4-scale wavelet package transform. A “binary tree” multi-class support vector machine(MCSVM) classifier, with the normalized feature vector as inputs, and Gaussian radial basis function as kernel function, was developed to identify the three typical flow regimes in-cluding stratified wavy flow, annular mist flow, and slug flow for wet gas flow. The results show that the method can identify effec-tively flow regimes and its identification accuracy is about 93.3%. Comparing with the other classifiers, the MCSVM classifier has higher accuracy, especially under the case of small samples. The noninvasive measurement approach has great application prospect in online flow regime identification.     

电阻层析成像有限元仿真模型分析与设计

本文根据电阻层析成像(ERT)中常采用的16电极相邻激励模式,以及有限元计算中广泛采用的三角形网格元素划分.比较分析了5种不同拓扑类捌模型的对称性误差和结构性误差.仿真结果表明不同类型模型各有优缺点,实际应用中应结合具体情况与系统要求选择理想有限元模型.在此基础上,讨了网格分布形式、有限元质量等因素对ERT有限元仿真不确定度的影响,并探讨了提高ERT计算精度的有限元网格设计方法.仿真实验表明,传统的按等间隔原理剖分的有限元模型并不合理,而通过适当调整有限元剖分密度等措施可降低ERT有限元计算的不确定度.     

ECT传感器结构影响分析

设计一种便于分析径向屏蔽结构影响的有限元分析模型,全面分析了电容层析成像(Electrical Capaci-tance Tomography)系统中阵列传感器结构参数对系统性能的影响。在定量分析的基础上合理解释并提出定性的分析结果,为全面认识传感器结构对敏感场分布的影响以及传感器的设计提供依据。有利于深入了解敏感场分布,优化传感器以改善传感器性能。