气液两相流差压波动信号的Hilbert-Huang变换特性

将Hilbert-Huang（HHT）变换应用于中小管径水平管气液两相流差压波动信号的分析.利用经验模态分解（EMD）方法把信号分解成多个内模函数(IMF),再对各内模函数进行Hilbert变换,得到信号的Hilbert谱,并提取各内模函数的信号能量特征.在此基础上比较了不同管径下信号分析的结果,分析了不同频段的能量分布与流型变迁的关系,并讨论了小波变换和HHT两种信号处理方法各自的特点.实验结果表明,HHT可以用于非线性非平稳信号的分析,提取的能量特征值反映了水平管气液两相流的流动状态和流型的变迁,该方法为水平管气液两相流差压波动信号的研究提供了借鉴.     

基于EMD和ICA的AR模型在两相

为了对气液两相流流型进行准确识别,提出了一种基于经验模态分解（EMD）和独立成分分析（ICA）的AR模型的流型识别方法。该方法首先提取气液两相流动态差压信号,通过EMD技术对其进行分解,对分解出来的高频模态进行小波包消噪,然后通过ICA技术实现原始信号的降维处理。对通过ICA得到的独立分量建立AR模型,将模型参数和残差方差作为特征向量,建立不同流型的模板向量。计算未知流型信号的特征向量与模板特征向量的综合Mahalanobis距离,通过比较各判别距离的大小得到流型识别的结果。对40 mm水平管气水两相流进行实验,利用文丘里管采集动态差压信号,采用上述处理过程可以对泡状流、弹状流、塞状流进行有效识别,识别率达94.3％。该方法受环境条件影响小,可以有效滤除信号中的噪声成分,识别率高,易于工程实现。     

基于EMD和ICA的AR模型在两相流流型识别中的应用

为了对气液两相流流型进行准确识别,提出了一种基于经验模态分解(EMD)和独立成分分析(ICA)的AR模型的流型识别方法。该方法首先提取气液两相流动态差压信号,通过EMD技术对其进行分解,对分解出来的高频模态进行小波包消噪,然后通过ICA技术实现原始信号的降维处理。对通过ICA得到的独立分量建立AR模型,将模型参数和残差方差作为特征向量,建立不同流型的模板向量。计算未知流型信号的特征向量与模板特征向量的综合Mahalanobis距离,通过比较各判别距离的大小得到流型识别的结果。对40mm水平管气水两相流进行实验,利用文丘里管采集动态差压信号,采用上述处理过程可以对泡状流、弹状流、塞状流进行有效识别,识别率达94.3%。该方法受环境条件影响小,可以有效滤除信号中的噪声成分,识别率高,易于工程实现。     

不同管径水平管气液两相流流动特性数值模拟

为更好了解不同管径水平管气液两相流的压降特性,选用空气和水在管径分别为38.1,50.8,101.6 mm,长为9.525 m的水平管内进行气液两相流数值模拟,并结合理论分析了不同管径下水平管气液两相流压降的变化规律.利用Fluent软件研究结果表明:在同一管径下,当液速一定时,压降随气速的增大而增大;气速恒定时,压降...     

基于旋转分相单元的电容式气液两相流含液率测量

为提高电容器对含水率测量的能力,设计与其相匹配的旋转分相单元,以实现气液两相流含水率的起旋分相式电容测量。在电容传感器的测量单元基础上,增加旋转分相单元,利用气液两相流体力学理论对其结构进行设计优化,并根据实际应用条件确定分离圈数,保证气液分相效率。旋转分相单元克服了气液两相流流动形态的多样性,将体积含水率信息转换成液膜厚度信息及截面含水率信息进行测量。经实验验证,Lockhart-Martinelli截面含气率模型与实验中电容器测量截面含气率具有良好的一致性,其能够实现对体积含水率20%以内的气液两相流有效测量,体积含水率的绝对误差在±2%以内。     

基于旋转分相单元的电容式气液两相流含液率测量

为提高电容器对含水率测量的能力,设计与其相匹配的旋转分相单元,以实现气液两相流含水率的起旋分相式电容测量。在电容传感器的测量单元基础上,增加旋转分相单元,利用气液两相流体力学理论对其结构进行设计优化,并根据实际应用条件确定分离圈数,保证气液分相效率。旋转分相单元克服了气液两相流流动形态的多样性,将体积含水率信息转换成液膜厚度信息及截面含水率信息进行测量。经实验验证,Lockhart-Martinelli截面含气率模型与实验中电容器测量截面含气率具有良好的一致性,其能够实现对体积含水率20%以内的气液两相流有效测量,体积含水率的绝对误差在±2%以内。     

垂直上升绝热管内汽、液两相流的压降

针对蒸发过程中沸腾层内汽、液两相流的流动状态,对垂直上升绝热管内汽、液两相流流动状态(泡状流和弹状流)中压降的主要部分采用与实际情况相近的模型进行分析,对压降的次要部分采用均相模型和分相模型进行分析,通过积分推出两相流体在区间[Z_1,Z_(1+1)]内总压降的计算式。本文理论计算值与实验结果符合较好。     

基于分相流模型的气液两相流流量测量

从伯努利方程出发,基于分相流模型,推导出气液两相流流过文丘里管的流量公式.在分析了两相流通过节流装置的实际流动情况后,作者认为气液两相滑移比是影响流量公式误差的一个重要因素.在理论与实验研究的基础上,作者提出了气液两相流流过文丘里管的滑移比经验关联式.利用作者提出的滑移比经验关联式和分相流模型的流量公式测量两相流流量,体积流量误差的均方根小于5.1%,表明该方法适用流过文丘里管的两相流流量测量,尤其对于两相流动激烈的两相相互作用区域,流量误差满足测量的要求.     

气液两相流水平绕流柱体的动态压降特性

压降是气液两相流绕流柱体时包含丰富流动信息的重要参数,对于压降的研究密切关系到两相流动系统的设计和运行.以空气和水为实验介质在泡状流、塞状流、弹状流和环状流四种流型下,研究了气液两相流水平绕流梯形柱体的动态压降特性.结果表明:泡状流和塞状流的动态压降有较稳定的波动,其时均值主要取决于液相流量;弹状流的动态压降变化剧烈,其时均值随两相雷诺数的分布比较均匀;环状流的动态压降变化比较平缓,其时均值随两相雷诺数的增加呈近似线性递增;在四种不同流型下,时均动态压降系数随两相雷诺数的增加都呈线性递减.这一结果为分析气液两相流绕流柱体的流动特性提供了有益的借鉴.     

电阻层析成象技术在两相管流测量中的应用

介绍应用电阻层析成象 (ERT)技术测量两相流中的基本原理和ERT系统的基本结构 ;描述应用天津大学过程层析成象研究室开发的ERT系统样机 ,在实验装置上进行两相流流型识别的实验研究。提出应用ERT系统进行流型识别的基本方法 ;并通过重建图像和分析测量数据实现两相流流型的识别。实验结果证明应用ERT系统实现两相流流型和参数测量的可能性     

Characterization of Air‐Water Two‐Phase Vertical Flow by Using Electrical Resistance Imaging

The characterization of air‐water two‐phase vertical flow in a 12 m flow loop with 1.5 m of vertical section is studied by using electrical resistance tomography (ERT). By applying a fast data collection to a dual‐plane ERT sensor and an iterative image reconstruction algorithm, relevant information is gathered for implementation of flow characteristics, particularly for flow regime recognition. A cross‐correlation method is also used to interpret the velocity distribution of the gas phase on the cross section. The paper demonstrates that ERT can now be deployed routinely for velocity measurements and this capability will increase as faster measurement systems evolve.     

Measurment of gas-liquid two-phase slug flow with a Venturi meter based on blind source separation☆

We propose a novel flow measurement method for gas–liquid two-phase slug flow by using the blind source sep-aration technique. The flow measurement model is established based on the fluctuation characteristics of differ-ential pressure (DP) signals measured from a Venturi meter. It is demonstrated that DP signals of two-phase flow are a linear mixture of DP signals of single phase fluids. The measurement model is a combination of throttle re-lationship and blind source separation model. In addition, we estimate the mixture matrix using the independent component analysis (ICA) technique. The mixture matrix could be described using the variances of two DP sig-nals acquired from two Venturi meters. The validity of the proposed model was tested in the gas–liquid two-phase flow loop facility. Experimental results showed that for most slug flow the relative error is within 10%. We also find that the mixture matrix is beneficial to investigate the flow mechanism of gas–liquid two-phase flow.     

基于ERT传感器和数据挖掘技术的空气水两相流空隙率测量(英文)

Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least squares support vector machine(LS-SVM) algorithm together with the feature extraction method,and three feature extraction methods are tested:principal component analysis(PCA),partial least squares(PLS) and independent component analysis(ICA).In the practical voidage measurement process,the flow pattern is firstly identified directly from the conductance values obtained by the ERT sensor.Then,the appropriate voidage measurement model is selected according to the flow pattern identification result.Finally,the voidage is calculated.Experimental results show that the proposed method can measure the voidage effectively,and the measurement accuracy and speed are satisfactory.Compared with the conventional voidage measurement methods based on ERT,the proposed method doesn’t need any image reconstruction process,so it has the advantage of good real-time performance.Due to the introduction of flow pattern identification,the influence of flow pattern on the voidage measurement is overcome.Besides,it is demonstrated that the LS-SVM method with PLS feature extraction presents the best measurement performance among the tested methods.     

Measuring gas hold-up in gas–liquid/gas–solid–liquid stirred tanks with an electrical resistance tomography linear probe

An electrical resistance tomography (ERT) linear probe was used to measure gas hold-up in a two-phase (gas–liquid) and three phase (gas–solid–liquid) stirred-tank system equipped with a Rushton turbine. The ERT linear probe was chosen rather than the more commonly used ring cage geometry to achieve higher resolution in the axial direction as well as its potential for use on manufacturing plant. Gas-phase distribution was measured as a function of flow regime by varying both impeller speed and gas flow rate. Global and local gas hold-up values were calculated using ERT data by applying Maxwell's equation for conduction through heterogeneous media. The results were compared with correlations, hard-field tomography data, and computational fluid dynamic simulations available in the literature, showing good agreement. This study thus demonstrates the capability of ERT using a linear probe to offer, besides qualitative tomographic images, reliable quantitative data regarding phase distribution in gas–liquid systems.     

Enhanced high-order information extraction for multiphase batch process fault monitoring

Conventional independent component analysis (ICA) monitoring methods extract the feature information of process data by selecting more important independent components (ICs), which discard a small part of ICs that may contain useful information for faults, leading to unsatisfactory monitoring results. However, when the number of sampling points is greater than that of process variables, the ICA monitoring model does not work well. To address the aforementioned problems, a novel monitoring method, multiphase enhanced high-order information extraction (MEHOIE), is proposed in this paper. The entire production process was first divided into several steady phases and transition phases by the affinity propagation (AP) phase partitioning method. The enhanced high-order information extraction (EHOIE) model was then built in each phase for fault monitoring. Finally, the algorithm was applied in the penicillin simulation platform and industrial microbial pharmaceutical process. The flexibility and superiority of this algorithm were verified by comparing it with other conventional methods.     

Analysis of gas holdup in bubble columns with non-Newtonian fluid using electrical resistance tomography and dynamic gas disengagement technique

This paper presents an experimental analysis of the influence of the liquid rheology on the gas flow pattern in a bubble column reactor. Aqueous solutions of xanthan are selected as an example of non-Newtonian shear thinning fluid. Averaged gas holdup is determined by two experimental techniques: parietal pressure probes and electrical resistance tomography (ERT). ERT is also used to provide 2D images of the gas phase distribution in a column cross-section. Bubble size distributions are evaluated by a gas disengagement technique using the parietal pressure probes. All these techniques clearly show the gas flow pattern is different in Newtonian and non-Newtonian fluids. Gas holdup values decrease when increasing the liquid viscosity and reach a minimum or a plateau. Homogeneous flow regime, observed in water at low gas velocities, tends to disappear when viscosity increases. This evolution is visualized by a much less isotropic distribution of the gas phase within cross-section of the column and by the appearance of much larger bubbles due to an increased coalescence phenomenon.     

Electrical resistance tomography for flow characterization of a gas-liquid-solid three-phase circulating fluidized bed

Electrical resistance tomography (ERT) as an imaging technique was employed in this study for flow characterization, including simultaneous measurements of phase holdups and velocity distribution of individual phases in a gas-liquid-solid circulating fluidized Bed (GLSCFB). Application of ERT in three-phase flow systems is completely new. ERT is a non-invasive technique based on conductivity of the continuous phase, which provides color-coded cross-sectional view of the phases with a frequency of up to 250 Hz. The local conductivity measured by 16 electrodes located at the periphery of the plane inside the ERT measurement section, was then further converted into local phase concentration distribution based on Maxwell's relation. By cross-correlation analysis between the data obtained from both upstream and downstream planes, each consisting of eight electrodes, the phase propagation velocity was determined. Water was used as the continuous and conductive phase, while glass beads and air were non-conductive solid and gas phases, respectively. Qualitative and quantitative radial profiles of the phase holdup and propagation velocities were obtained. Phase holdup was also measured by pressure fluctuation, using online non-invasive pressure transducers and the results were in close agreement with the ERT results.     

Analyses of color emotion for color pairs with independent component analysis and factor analysis

Semantic‐differential data of color emotions for color pairs were collected and examined with factor analysis (FA) and independent component analysis (ICA). The axial orientations of factors cannot be identified by FA, whereas they can be determined by ICA with the intrinsic statistical properties of data such as kurtosis. Three factors or components were extracted by FA and ICA. The factors extracted by FA with the varimax method were consistent with the primary factors: evaluation, activity, and potency. When ICA extracted components with positive kurtosis, the components did not match any of the primary factors. However, the independent components extracted by ICA for negative kurtosis were consistent with the primary factors, and similar to the factors obtained by FA. The results of ICA suggest that the evaluation, activity, and potency factors are independent dimensions in psychological space of color emotions for color pairs. The distributions of the factor scores in FA and the scores of the independent components obtained by ICA for negative kurtosis were not Gaussian, but they had negative kurtosis. These support the use ofICA instead of FA. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 297–308, 2013     

Influence of Pressure on the Hydrodynamics and Mass Transfer Parameters of an Agitated Bubble Reactor

The present study deals with the pressure effects on the hydrodynamic flow and mass transfer within an agitated bubble reactor operated at pressures between 10⁵ and 100 × 10⁵ Pa. In order to clarify the flow behavior within the reactor, liquid phase residence time distributions (RTD) for different operating pressures and gas velocities ranging between 0.005 m/s and 0.03 m/s are determined experimentally by the tracer method for which a KCl solution is used as a tracer. The result of the analysis of the liquid‐phase RTD curves justifies the tank‐in‐series model flow for the operating pressure range. Good agreement is obtained between theoretical and experimental results assuming the reactor is operating as perfectly mixed. Two parameters characterizing the mass transfer are identified and investigated in respect to pressure: the gas‐liquid interfacial area and volumetric liquid‐side mass transfer coefficient. The chemical absorption method is used. For a given gas mass flow rate, the interfacial area as well as the volumetric liquid mass transfer coefficient decrease with increasing operating pressure. However, for a given pressure, a and k_La increase with increasing gas mass flow rates. The mass transfer coefficient k_L is independent of pressure.     

周期性扩缩微通道内气液两相流型及其演变特性

以空气和水为实验工质,利用IDT高速摄像仪和Nikon生物显微镜组成的可视化系统对水平放置的PDMS周期性扩缩微通道内的气液两相流型及其演变特性进行实验研究。观察到的主要流型为间歇流和分离流。对于间歇流,气体以离散形式分布在液相中或者是液体以分散形式分布在气相中,而且气相分散跟液相分散交替存在。对于分离流,气体主要沿气体进口壁侧流动,液体主要沿液体进口壁侧流动。两相中存在明显的分界面,沿流动方向界面产生波动。通过改变气液两相表观流速,得到气液两相流型分布,进而提出间歇流与分离流流型转换的准则关系式。结果表明,同一液相表观流速下,三角凹穴型微通道间歇流向分离流转变所需的气相表观流速略小于扇形凹穴微通道。