New techniques for multi-component flow velocity measurement using high-frequency pulsed diode lasers

The application of high-frequency pulsed laser diodes for fringe-type laser Doppler anemometry allows multi-component flow velocity measurements by using only one receiver and one signal processing chain. This is effected by synchronization of the laser pulses with the sampling process of the data acquisition system. Consequently, an identical wavelength can be used for all components. The experimental verification of this new technique is described. The technique permits the design of miniaturized and low cost optical flow sensors which can be used for low and high speed flows.     

动态电容层析成像图像重建算法

提出了融合ECT测量信息和被测对象动态演化信息的新型图像重建模型;基于Tikhonov正则化方法,建立一个同时考虑了ECT测量信息、被测对象动态演化信息、时间与空间约束的新型图像重建目标泛涵,将图像重建问题转化为最优化问题;提出了集成分裂Bregman迭代法优势的新型算法求解该目标泛涵。数值仿真结果表明,所提出的图像重建算法其图像重建质量均优于OIOR算法、STR算法及PLI算法;同时由于所提出的图像重建算法同时考虑了测量数据和重建模型的不精确性,其抵抗测量噪声的能力得以提高。     

基于双截面ECT的气/固两相流参数检测系统

为了实现多相流的流动过程在线监测和多参数测量,设计并研发了一套应用于气/固两相流检测的双截面8电极电容层析成像系统.采用交流法电容检测原理实现具有16个独立电容检测通道的电容测量电路,实测系统的成像速度为590帧/秒.将双截面电容层析成像系统用于气/固两相流的实时检测,并将两层截面的图像作相关计算,获取成像截面的固相速度分布.由固相速度和浓度最终算出气/固两相流的固相质量流量,从而实现气/固两相流浓度、速度、流量等多参数的综合检测.将双截面ECT传感器算得的质量流量与发料罐重力传感器获取的质量流量作对比发现,两者具有较好的一致性,流量测量误差小于8％.     

矩形电容层析成像传感器仿真模拟和实验测量

常规电容层析成像传感器为规则对称方形或圆形结构,其测量和成像算法已相对成熟.由于受循环流化床旋风分离器入口结构段的限制,上述传感器结构已不能应用在旋风分离器入口段的测量,因此为了研究大型化循环流化床多旋风分离器并联布置入口段固体颗粒浓度分布,提出和设计了一种矩形非常规电容传感器,该传感器为12电极结构,在每个入口段的短边布置2个电极,长边布置4个电极,成像敏感场仿真计算基于Ansoft-Maxwell软件.对此传感器进行了静态仿真模拟研究和静态实验测量,对不同激励电压和频率测量结果进行分析,并对测量结果进行误差分析,得到矩形不规则电容传感器最佳测量参数(激励电压和频率),并对循环流化床分离器入口段进行了动态测量.结果表明,这种矩形非常规电容传感器可以用于循环流化床冷态试验台的旋风分离器入口段的直接测量,测量结果对改进旋风分离器的布置方式有参考意义.     

Flow pattern identification for gas-oil two-phase flow based on a virtual capacitance tomography sensor and numerical simulation

Gas-oil two-phase flow is widely encountered in oil exploitation and transportation pipelines. It's complex and transient changes of flow regimes present a great challenge for accurate and real-time measurement. As a non-invasion and real-time measuring method, electrical capacitance tomography (ECT) is suitable for the transient measurement of non-conductive gas-oil flow. However, the highly random and nonlinear nature of multiphase flow make it difficult and limited to investigate the flow parameters based on either static or dynamic measurement. In this research, the whole process of dynamic measurement of ECT applying in gas-oil two-phase flow is thoroughly studied, including simulation calculation, experimental validation and comprehensive data analysis. A simulation approach by coupling the flow and electrostatic field is proposed based on a virtual ECT sensor, in order to monitor the gas-oil two-phase flow characteristics. Based on FLUENT and COMSOL platform, the numerical simulation under six typical flow patterns in a horizontal pipe is carried out. Combining the visualized image generated by ECT measurement and the theory of flow pattern transition, the formation mechanism and structural characteristics of different gas-oil flow patterns are analyzed in detail. Furthermore, this research attempts to analyze the signal fluctuation characteristics caused by flow pattern change, in order to access more in-depth flow information implied in the original capacitance data, via time-series analysis as well as frequency domain analysis based on Flourier Transform. At last, a series of dynamic experiment is conducted to verify the feasibility of the simulation and data analysis approach. The experiment focuses on the flow pattern transition, gas-liquid dynamic characteristics and noise influence in the actual process. It can be concluded from the results of simulation and experiment tests, combining the visualized images and the dynamic characteristics of capacitance signals can make it more effective and intuitive for flow pattern identification, which might be used for the online measurement in real-industry process.     

Dynamic imaging method using the low n-rank tensor for electrical capacitance tomography

Imaging objects in electrical capacitance tomography (ECT) measurement are often in a dynamic evolution process, and exploiting the spatial–temporal properties of the dynamic reconstruction objects is crucial for the improvement of the reconstruction quality. Based on the multiple measurement vectors, in this paper a robust dynamic reconstruction model that incorporates the ECT measurement information and the dynamic evolution information of a dynamic object, in which a series of dynamic images is cast as a third-order tensor that the first two dimensions are space and the third is time, is proposed. Under the considerations of the two-dimensional spatial structure property of a difference image and the spatial–temporal property of a third-order image tensor, a new objective functional that fuses the ECT measurement information, the dynamic evolution information, the temporal constraint, the spatial constraint, the low rank constraint of a difference image and the low n-rank constraint of a third-order tensor is proposed, where the images are reconstructed by a batching pattern. The split Bregman iteration (SBI) algorithm is developed for solving the proposed objective functional. Numerical simulations are implemented to demonstrate the advantages of the proposed algorithm on improving the reconstruction quality and the robustness.     

用于两相流测量的ECT图像重构技术研究

电容层析成像技术(ECT)具有非侵入、响应速度快、成本低等优点,是用于两相流参数检测非常有发展潜力的技术之一。而图像重构是ECT系统研究的关键技术。该文利用有限元方法对12电极ECT系统进行建模仿真,进行正问题求解,获得了图像重构的样本数据;引入改进的径向基函数神经网络,建立了ECT图像重构算法,并在MATLAB平台上进行了仿真验证。结果表明,改进的径向基神经网络算法在图像重构准确度及速度方面有了明显提高。     

多模态流动成像技术研究进展

流动成像技术采用空间敏感阵列,以非接触或非侵入方式对被测对象进行检测,可实时提供封闭管道、容器等过程设备内物场的二维/三维分布和运动状态信息,是实现流动过程可视化测量的核心技术。多模态流动成像通过融合不同敏感模态的检测信息实现多相、多组分流动过程的可视化监测以及过程参数的准确提取。分别介绍了电学、超声与射线单模态流动成像基本原理;总结了已有的多模态流动成像系统及其构成,以及适用于多模态流动图像重建的融合算法;讨论了在不同流动对象与工况条件下的多模态选择与系统设计原则。在此基础上,对多模态流动成像发展中的关键技术与科学问题进行了展望。     

流场超声层析成像中图像的迭代滤波反投影重建

为提高流场超声层析成像的图像重建质量,提出了一种迭代滤波反投影图像重建算法。该算法借鉴联合迭代重建算法的原理,将滤波反投影算法引入迭代重建过程。首先,利用滤波反投影算法,通过投影数据残差重建误差图像对流场图像进行修正,实现图像的迭代重建。然后,通过优化迭代步长,使每步迭代后投影数据残差均取得极小值以便加快收敛速度。最后,基于流场连续、紧支撑分布的特点,在迭代重建过程中引入投影数据的细分内插和流场图像的圆域修正。实验表明:相比于滤波反投影算法,迭代滤波反投影算法可使理论流场重建的图像误差平均减少26%,流量误差由1.77%减小至±0.25%以内;程序运行时间为0.63s,仅为联合迭代重建算法的0.89%。该算法可实现对直管段内和单弯管下游实际流场的可靠重建,满足流场高精度实时成像的要求。     

电容式气固两相流浓度测量系统

本文介绍一种电容式气固两相流浓度测量系统,给出了具体的测量电极和测量电路。并采用所设计的电容式浓度测量系统在自行搭建的气力输粉系统上以面粉为媒质、在水平管道上对稀相气固两相流浓度进行了在线测量,获得了5×10^-5%体积百分比的面粉浓度分辨率。应用该系统对锅炉气力输粉管道中的气固两相流浓度进行实时在线检测与控制,对确保燃烧过程稳定,节能降耗和减少污染排放具有重大意义。     

杂散电容对交流法微电容测量电路噪声特性影响的分析

对电容成像交流法微电容测量电路由杂散电容导致的测量噪声进行了研究.利用运算放大器的噪声模型,对运算放大器输入电压噪声、输人电流噪声以及周边电阻元件的热噪声通过杂散电容作用于交流法微电容测量电路输出的影响进行了理论分析,给出了测量电路输出中噪声峰峰值的理论计算公式并进行了实验验证.理论分析及实验结果表明:交流法微电容测量电路前级运算放大器输入电压噪声通过测量端与地之间的杂散电容形成的噪声是该微电容测量电路输出噪声的主要来源.最后给出了电容成像系统前级运算放大器选型的指导原则.     

Extracting reference voltages from measurement voltages for oil-water two-phase flow measurement of electrical impedance tomography

To apply electrical impedance tomography (EIT) for heterogeneous two-phase flow measurement, reference voltages have to be measured, which requires the entire pipeline filled with a homogeneous medium. Such process is often time-consuming, costly and infeasible in some cases. Reference voltages acquired initially could not be used later, because of electrical conductivity change of two-phase flow caused by temperature change or chemical reaction. It will be ideal if reference voltages could be extracted from measurement voltages. In this paper, a novel multiple measurements (MMs) method is proposed by data fitting and empirical formula to establish the mapping model from measurement voltages to reference voltages, and the effectiveness of the method is proved by the oil-water two-phase flow experiment. Compared with the measurement-scale feature (MSF) and best homogeneous (BH) methods, the proposed MMs method achieves 6.38% average relative error (RE) and 4.96% average volume fraction relative error (VFRE) in the test set. The work enables the accurate estimation of the reference voltage and thus the accurate measurement of the volume fraction of oil-water two-phase flows, which will broaden the application of EIT in the field of two-phase flow measurement.     

Framework for morphometric classification of cells in imaging flow cytometry

Imaging flow cytometry is an emerging technology that combines the statistical power of flow cytometry with spatial and quantitative morphology of digital microscopy. It allows high‐throughput imaging of cells with good spatial resolution, while they are in flow. This paper proposes a general framework for the processing/classification of cells imaged using imaging flow cytometer. Each cell is localized by finding an accurate cell contour. Then, features reflecting cell size, circularity and complexity are extracted for the classification using SVM. Unlike the conventional iterative, semi‐automatic segmentation algorithms such as active contour, we propose a noniterative, fully automatic graph‐based cell localization. In order to evaluate the performance of the proposed framework, we have successfully classified unstained label‐free leukaemia cell‐lines MOLT, K562 and HL60 from video streams captured using custom fabricated cost‐effective microfluidics‐based imaging flow cytometer. The proposed system is a significant development in the direction of building a cost‐effective cell analysis platform that would facilitate affordable mass screening camps looking cellular morphology for disease diagnosis.     

中红外傅里叶气体分析软件系统的设计

中红外傅里叶多组分气体分析仪已逐渐成为环境污染检测,工业生产过程监控的有力工具。文中基于自行研制的PFTS型中红外傅里叶多组分气体分析仪,介绍了相应的中红外傅里叶多组分气体分析软件系统构成和设计方法,并重点描述了软件系统的主要模块:光谱连续采集,光谱识别与具基线自补偿能力的多组分浓度分析方法的实现原理和具体算法。现提出的设计方法对光谱研究人员开发产品化的多组分气体分析软件有一定的借鉴之处。     

Flow measurement method of complex flow in heat exchange casing

Fluid plays an important role in engineering application and the accurate control of the carrier is the premise of energy efficient conversion and management, such as the primary air volume of the boiler, the reactor inlet flowrate, the amount of oil and air intake of internal combustion engine, etc. Therefore, flowmeter plays an important role in energy conversion and management. In this work, a high-low frequency combined with reflection-penetration synchronization flowmeter was designed to measure the flowrate in casing device based on the characteristics of different frequencies of sound. The flowrate calculation method of casing device is given and verified by numerical simulation. The results show that the flowrate of different flow states can be calculated accurately by using the high-low frequency combined with reflection-penetration synchronization method. At the same time, the method can also be used in electromagnetic wave, optical and other fields.     

Development and assessment of a new operating principle for the measurement of unsteady flow rates in high-pressure pipelines

Instantaneous mass flow rate measurements in high-pressure transmission pipelines under transient flow conditions can be valuable for the analysis of hydraulic power systems. However, at present no reliable commercial measuring device is available for pressure levels beyond 300 bar. A new operating principle, of general application, for measuring the flow rate in high-pressure flows (from 300 to 2000 bar) was developed and assessed. The innovative device was capable of accurately evaluating the instantaneous mass flow rate on the basis of the pressure–time histories detected at two different locations by high-pressure transducers. The measurement operating principle was detailed and technical indications for the flowmeter correct design were provided.For validation purposes, the flow rate measurements taken at the inlet of a Multijet Common Rail (CR) injector were compared to the theoretical data predicted by an advanced numerical model of the complete fuel injection system.The developed flowmeter was then applied to characterize the flow rate ripple at the delivery of the CR high-pressure reciprocating pump.     

Flow rate measurement by an orifice in a slowly reciprocating gas flow

It is shown that small density changes can give rise to misinterpretation of flow rate signals in unsteady (reciprocating) flows. Basically a flow rate measured at some point A cannot simply be assigned to a remote point B. Depending on the way of plotting a hysteresis appears which, in fact, does not exist. Unsteady conservation of mass is applied to a volume and orifice flow system to obtain an equation which explains and predicts the apparent hysteresis. The equation in dimensionless form contains a key parameter β which holds the flow determining quantities. Experiments are conducted with respect to a wide spread of β. It is shown that the equation predicts reality quite well.     

Visualization of flow pattern in thermosyphon by ECT

Visualization of the liquid flow in a two-phase closed thermosyphon (TPCT) is studied using electrical capacitance tomography (ECT) with optimal step lengths for iterative image reconstruction algorithm. Measurements are made under a range of heating rates. Experimental results demonstrated ECT’s capability of reconstructing images of thin films of the order of μm in thickness. Results are compared with the established theory and agreements and discrepancies are observed for different thresholds. ECT images of the liquid distributions in the TPCT show clear dependence on the variation of working conditions, which reveals the potential of ECT as an advanced technique for monitoring the operation of TPCT.     

锅炉送粉管道煤粉浓度的电容层析成像测量方法研究

锅炉燃烧过程中,准确测量各风管中的煤粉浓度并指导调节对锅炉的安全、经济运行非常重要.采用电容层析成像技术(ECT),对常温下锅炉煤粉气力输送的固体浓度进行了测试研究.为克服电容传感器敏感场的不均匀性对成像造成的影响,实验系统中装置了一个旋风分离装置,通过旋风分离作用将固体颗粒主要集中在壁面区域,传感器电极布置在分离器直管上.这种测试方法的优点在于不破坏原有系统的运行特性,属于非侵入式、在线的快速测试技术.通过搭建实验台及相应的在线测量系统,并对不同浓度工况进行测量及对比分析,实验结果证明了该测量方法的可行性及可靠性.