油水两相流浓度电容层析成像的测量方法

以8电极油水两相流电容层析成像系统为研究对象,分析了油水两相流电容层析成像系统的测量原理,依据二重积分微元原理建立了油水两相流相浓度分布信息的数学模型,采用ART图像重建的方法完成油水两相流的浓度测量,并在重建算法中引入了阈值以提高图像重建质量和含率计算的准确性,测量误差在1%左右,较好地解决了其他测量方法速度慢,成本高,安全性差等缺陷,为油水两相流浓度的测量提供了一种新方法.     

一种电容层析成像图像重建优化算法

提出一种电学层析成像(ECT)图像重建优化算法。通过将传统正则化算法转化为最小二乘问题进行求解,结合lp范数逼近正则化最小化问题,利用重新加权的方法进行迭代计算。以油-气两相流模型进行仿真及静态实验,将所提出的优化算法与常用的LBP、Landweber迭代及Tikhonov正则化算法进行对比。结果表明,与常用算法相比,采用该优化算法对管道中心物体及多物体分布流型进行图像重建,其图像相对误差均为最低,且重建图像的形状保真度明显提高。     

基于电容层析成像系统测量信号稀疏性的两相流流型辨识

提出了基于电容层析成像(ECT)测量电容信号稀疏性的两相流流型辨识算法,该算法首先使用所有流型对应的归一化测量电容值信号构建一个过完备字典,并将待辨识样本通过该过完备字典进行稀疏表示,使其具有稀疏性并满足稀疏重构的基本要求,然后以压缩感知的正交匹配追踪(OMP)算法求取各标准样本对应于完备样本集的稀疏解,最后根据待辨识样本与标准样本稀疏解之间的线性相关程度进行流型辨识。使用该方法对5种典型的两相流流型识别进行了仿真及实验研究,结果表明:该方法的流型正确识别率均高于98%。     

Application of electrical capacitance tomography to the void fraction measurement of two-phase flow

Based on the electrical capacitance tomography technique, a new method for the void fraction measurement of two-phase flow is proposed. A 12-electrode void fraction measurement system is established. A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, combining the Tikhonov regularization principle and the algebraic reconstruction technique algorithm, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of void fraction measurement is satisfactory. The proposed method is suitable for the void fraction measurement of many kinds of two-phase flow.     

气液两相流阶跃脉冲瞬变过程数值计算

构建了气液两相流动的半经验波动模型，用特征线法对绝热管中初始空泡分布为阶跃脉冲的气液两相流动过程进行数值计算，研究脉冲空泡分布的流动稳定性。计算表明，脉冲空泡场具有色散波特征，存在不稳定的行波解。阶跃稳定域由阶跃初始值、终了值以及漂移通量特性决定。     

基于多元经验模态分解与卷积神经网络的气液两相流流型识别

提出了一种基于多元经验模态分解(MEMD)与卷积神经网络(CNN)的垂直管道气液两相流流型识别方法。该方法基于数字化电阻层析成像(ERT)系统采集的测量数据,预处理后进行MEMD分析,通过求取各分量与原始信号的皮尔逊相关系数选取本征模函数(IMFs)并求解Hilbert边际谱,提取Hilbert边际谱的标准差与均值作为卷积神经网络(CNN)输入以识别流型。结果表明,该方法能够有效识别泡状流、弹状流、段塞流,平均识别准确率可达96.43%。     

基于MO-PLP-ELM及电容层析成像的两相流流型辨识

提出一种基于多目标优化并行感知器的极限学习机(MO-PLP-ELM)及电容层析成像(ECT)技术的两相流流型辨识算法.首先,为保证样本具有代表性,采用随机思想生成7类流型的训练及测试样本集;其次,对样本模型的电容数据归一化处理;最后,采用MO-PLP-ELM算法进行流型辨识,并与常用的BP神经网络、支持向量机、极限学习...     

A Digital Special-Purpose Signal Processor for Two-Phase Flow Real-Time Analysis

In the statistical study of two-phase flow real-time control of experiments is often needed. Furthermore, in industrial processes involving boiling units control or two-phase gas-liquid transport control, real-time signal processing is required to check the status of two-phase flows. An instrument is described for the measurement of the fundamental characteristic parameters of two-phase flows. The measurement technique employs extensively high speed digital computation. It is based on a discrimination of the probe output signal into two signals, representing, respectively, a "bubble" flow and a slug flow. The parameters are measured on averaging times ranging from 10 ms to 104 s. Measurement errors and limitations of this high-resolution measurement technique are pointed out. Its utility in evaluating the fundamental statistical parameters of two-phase flows is demonstrated.     

Measurement and evaluation of two-phase flow parameters

The fuzzy set theory and the flow-imaging technique were applied to measure the flow pattern and void fraction of two-phase flow. The flow pattern was identified online by using `fuzzy identification', and an instrument system based on the flow-imaging technique was developed for online flow pattern measurement as well. The void fraction was evaluated online by `fuzzy multifactorial evaluation'. The void fraction was also measured online by an instrument system based on the flow-imaging technique. The experimental results show that the developed methods are satisfactory     

液压介质波速影响因素分析

为了给设计人员与管理人员提供依据,对液压系统介质中压力波波速的影响因素进行理论分析与计算。提出在高压系统中,考虑油—气两相状态下,原有的液压介质中压力波波速决定公式的各项假设条件已不成立,应当重新设定估算方法。采用最新的非插入式测量方法,把压力测量夹具安装在管路的两处,检测压力波达到不同夹具的时间差,计算波速。结果显示压力波波速变化的随机性,该结果可为系统仿真、设备的选型与液压设备管理工作提供参考。     

Application of electrical capacitance tomography in particulate process measurement – A review

Particulate process measurement presents challenges because it often involves multiphase flow. Due to its advantages over other tomography modalities, electrical capacitance tomography (ECT) is widely applied in monitoring and measuring particulate processes. This paper presents a review on the application of ECT in particulate process measurement, including the monitoring of flow regime and solids distribution, solids flow velocity measurement, and fluidized bed dryers. The electrostatic phenomenon and the effect of electrostatics on the performance of ECT systems are also addressed. Finally, the challenges to ECT for particulate process measurement are given.     

环形管流量计测量气液两相流研究

提出了一种基于环形管流量计的新型气液两相流流量测量方法.设计了多圈环形管流量传感器,通过对多圈环形管的水平直径上和垂直直径上四个差压信号进行分析,建立了不同位置差压信号与总体积流量和总质量流量的关系模型,并由此获得气液两相流的混合密度,实现了气液两相流分相流量的测量.     

长喉颈文丘里管气液两相流弹状流机理研究

为了实现气液两相流相含率测量并得到相关模型,结合气液两相流研究现状,采用近红外光谱技术与高速摄影技术结合的手段,利用近红外系统布置于长喉颈文丘里管喉管位置的新装置,将弹状流相间流动特征与近红外测量系统接收光强信号特征相结合,提出了把弹状流分成泰勒气泡与尾部气泡两部分的简化模型,在数据处理时对近红外接收光强高频信号进行有效分组,建立了新的气液两相流弹状流相含率测量模型。从一定程度上解决了弹状流不同部位的两相交界面对近红外接收探头接收光强信号影响差异较大的问题。新型模型的测量效果较好,所得结果测量误差较小。     

基于层析成像的气液两相流相关流量测量方法

对电阻层析成像技术和图像的小波纹理特征进行了研究,提出一种基于层析成像的气液两相流相关流量测量方法,实现了液相流量的准确测量。利用电阻层析成像技术和相关算法对不同泡型下的相含率、渡越时间进行检测,得到气相流量;利用小波分析提取出层析成像的流型纹理特征;从而基于BP神经网络建立不同泡型下的气液两相流的相关流量测量模型。实验结果表明,液体流量的测量精度可以达到3%以内。     

The measurement of thermodynamic performance in cryogenic two-phase turbo-expander

Liquid fraction measurement in cryogenic two-phase flow is a complex issue, especially for an industrial cryogenic system. In this paper, a simple thermal method is proposed for measuring the liquid fraction in cryogenic two-phase turbo-expander by an electric heating unit in experimental study. The liquid fraction of the cryogenic two-phase flow is determined through the heat balance built at the outlet of the turbo-expander (inlet of heating unit) and the outlet of the heating unit. Liquid fractions from 1.16% to 5.02% are obtained from five two-phase expansion cases. Under the same turbo-expander inlet pressure and rotating speed, five superheated expansion cases are tested to evaluate the wetness loss in two-phase expansion. The results show that the proposed method is successful in measuring the liquid fraction of cryogenic two-phase expansion for turbo-expander in an industrial air separation plant. The experimental isentropic efficiency ratio and the tested Baumann factor decrease with the increasing mean wetness. Based on prediction of Baumann rule, the cryogenic turbo-expander with low liquid fraction in two-phase expansion cases suffers from more severe wetness loss than that with the higher liquid fraction.     

基于小波变换的CT/ECT图像融合方法

在基于工业CT及ECT的多相流参数测量中,CT所得重建图像分辨率较高,但由于其投影角度较少,重建图像边缘出现失真;对于ECT 系统,由于其敏感场软场特性,其重建图像分辨率较低,但图像边缘保真度高。基于二者的互补特性,研究了CT/ECT图像融和方法,提出了改进的逻辑滤波器算法应用于小波变换的低频系数融合规则,结果表明该方法可提高融合后的重建图像质量。     

基于改进SR3模型算法的ECT图像重建研究

针对电容层析成像技术应用于气固两相流检测时,图像重建过程中存在的不适定性问题,提出一种稀疏松弛正则化回归模型(SR3)应用于ECT图像重建。采用软阈值迭代法和梯度下降法为SR3模型求解器,向SR3模型中加入L1、L2惩戒项,并设计滤值环节优化解向量。实验结果表明,改进SR3模型算法相比Tikhonov正则化算法、L1正则化算法及原SR3模型算法,重建图像精度明显提高,图像相对误差显著降低,有较好的成像效果。     

Numerical simulation of forward problem for electrical capacitance tomography using element-free Galerkin method

Electrical capacitance tomography (ECT) is a new measurement technology, which is often used to identify two-phase/multi-phase flow regime and investigate the solid distribution in circulating fluidized bed. It is composed of forward problem and inverse problem. Usually, forward problem is solved using finite element method (FEM). Element-free Galerkin method (EFGM) is one of the meshless methods developed recently. In order to obtain the numerical solution using EFGM, a shape function is constructed by moving least-squares (MLS) approximation, a variational equation weak form of the studied problem is used to deduce the discrete equation, and Lagrange multipliers are used to satisfy essential boundary conditions. In EFGM, only nodal data are necessary compared with FEM. In this paper, EFGM was used to solve forward problem and simulation results showed EFGM has high accuracy and its post-processing is easy.     

Two-Phase Flow and Heat Transfer During Chilldown of a Simulated Flexible Metal Hose Using Liquid Nitrogen

For many industrial, medical and space technologies, cryogenic fluids play irreplaceable roles. When any cryogenic system is initially started, it must go through a transient chill down period prior to normal operation. Chilldown is the process of introducing the cryogenic liquid into the system, and allowing the system components to cool down to several hundred degrees below the ambient temperature. The chilldown process is an important initial stage before a system begins functioning. The objective of this paper is to investigate the chilldown process associated with a flexible hose that was simulated by a channel with saw-teeth inner wall surface structure in the current study. We have investigated the fundamental physics of the two-phase flow and quenching heat transfer during cryogenic chilldown inside the simulated flexible hose through flow visualization, data measurement and analysis. The flow pattern developed inside the channel was recorded by a high speed camera for flow pattern investigation. The experimental results indicate that the chilldown process that is composed of unsteady vapor-liquid two-phase flow and phase-change heat transfer is modified by the inner wall surface wavy structure. Based on the measurement of the channel wall temperature, the teeth structure and the associated cavities generally reduce the heat transfer efficiency compared to the straight hose. Furthermore, based on the measured data, a complete series of correlations on the heat transfer coefficient for each heat transfer regime was developed and reported.     

基于1D-CNN-AdaBoost及电阻层析成像的两相流流型辨识

基于电阻层析成像(ERT)系统采集的垂直管气液两相流测量数据,将一维卷积神经网络(1D-CNN)与AdaBoost(Adaptive Boosting)相结合,构建1D-CNN-AdaBoost算法,进行了气液两相流流型辩识研究。该算法使用5个1D-CNN作为弱分类器,通过实验数据样本训练,结合AdaBoost形成最终的强分类器。将1D-CNN-AdaBoost算法与BP神经网络、支持向量机及决策树算法进行比较,结果表明,1D-CNN-AdaBoost算法辨识正确率高于其他算法,平均辨识正确率可达97%。