Performance analysis of a single-wire capacitance sensor for interface level measurement in stratified multiphase flows

A single-wire capacitance sensor can be used to measure the interface level of a conductive liquid in a stratified multiphase flow. This type of capacitive sensor uses the conducting core in an insulated wire as its first electrode, and the conductive fluid as its second electrode, separated by the wire insulation, producing a coaxial capacitor with a variable electrode length linearly correlated to the liquid level. Therefore in theory, there should be a linear relationship between the liquid level and measured capacitance value. However, at low liquid levels, the authors have observed a noticeable departure from the theoretical correlation in the way of an upward offset. The cause for such a departure is investigated by means of a simplified model geometry and attributed to an additional capacitance between the wire conductor and conductive plane provided by the liquid interface. Analytical and numerical modelling have been carried out to better understand this effect. Recommendations are given on how to correct it.     

数字图像技术在颗粒流测量中的应用

针对目前颗粒流速度场测量手段较单一的现状,系统介绍了基于数字图像技术的颗粒流速度场测量方法。通过对各种测量原理和使用条件的分析比较,指出了这些方法的特点和存在的主要问题,并结合颗粒流测量特点给出了这些测量方法在颗粒流速度场研究中的具体应用条件。此外,还讨论了数字图像技术在休止角测量方面的应用,以及这些测量方法在国内外的应用情况。这将对后续利用数字图像技术研究颗粒流提供指导。     

A parallel-wire microwave resonant sensor for measurement of water holdup in high water-cut oil-in-water flows

In the present study, we propose a parallel-wire microwave resonant sensor (PMRS) with transmission-through configuration for water holdup measurement in high water-cut oil-in-water flows. Through the finite element method (FEM) analysis using HFSS software, the variations of sensor responses for changing water holdup and salinity are investigated. In this manner, the optimum working frequency of microwave resonant sensor is tuned to 1.8 GHz. With the designed PMRS measurement system, an experimental test of vertical high water-cut oil-in-water flows is conducted in a 20 mm inner diameter pipe, through which the relationship among dimensionless normalized phase output of PMRS which reflects the water holdup information, water-cut and total flow rate are investigated. The results show that PMRS presents a high resolution in measurement of water holdup. By establishing statistics models, water-cut can be accurately predicted. Besides, PMRS can still retain high resolution under the circumstance of high salinity. To conclude, PMRS can possess high resolution in measurement of water holdup with both high water-cut and salinity variation in oil-in-water flows, and satisfactory water-cut measurement results can be achieved.     

A two-phase flow meter for determining water and solids volumetric flow rates in stratified,inclined solids-in-water flows

This paper describes the design and implementation of a two-phase flow meter which can be used in solids-in-water two phase pipe flows to measure the in-situ volume fraction distributions of both phases, the velocity profiles of both phases and the volumetric flow rates for both phases. The system contains an Impedance Cross Correlation (ICC) device which is used in conjunction with an Electromagnetic Velocity Profiler (EVP). Experimental results were obtained for the water and solids velocity and volume fraction profiles in upward inclined flow at 30° to the vertical, in which highly non-uniform velocity and volume fraction profiles occur.     

A new device for continuous ambulatory central venous pressure measurement

We have developed a device for continuous direct measurement of human central venous pressure (CVP) during space flight. Normal resting CVP is typically in the range of 5-10 mmHg; in zero gravity, the expected changes are +/- 5 mmHg or less. A 1-mm Hg change in CVP can represent a substantial intravascular fluid shift. The device is small, battery powered, and designed to run for at least 24 hr. Pressure is measured in a saline solution-filled catheter inserted into a central vein. The transducer is placed in the axilla at the level of the catheter tip to offset hydrostatic gradients. A pump and an electronic system mount on the leg. This assembly provides a slow, continuous infusion of heparinized saline solution to maintain the patency of the catheter. The electronic system generates a digital display in mm Hg, an analog output, and a visible and audible alarm for excessive pressure. An air-filled syringe allows for a two-point calibration (zero and a positive pressure generated by measured compression of a known gas volume). A two-failure tolerant system minimizes electric shock hazards. Two latex diaphragms separate the saline solution from the transducer surface, and the electronic system and pump chamber are in separate enclosures. A clear polycarbonate case allows bubbles to be seen. The unit has been tested for pump function, temperature stability, drift, and accuracy. We conclude that this approach provides a unit with sufficient stability, accuracy, and temperature insensitivity for measuring ambulatory CVP for up to 28 hr. The design may be suitable for ambulatory measurement of other intravascular and intracardiac pressures.     

Uncertainty analysis for multiphase flow: A case study for horizontal air-water flow experiments

This work describes the procedure used to define the measurement uncertainties of horizontal two-phase air-water flow experiments conducted to determine influences due to pipe diameter on pressure gradient on such flows. These experiments were performed with 4 different pipe diameters, always using the same test section length, therefore varying the length-to-diameter (L/D) ratio. Several parameters were measured, such as volumetric/mass flow rate, pressures, temperatures and pressure drop; other parameters were calculated, such as the superficial velocities of each fluid, as well as their corresponding properties. The main parameters studied were the flow patterns for different velocity configurations and the two-phase pressure drop to be used for model improvement, thus the importance of uncertainties analysis. The sources of uncertainty were defined, detailed, systematically studied and quantified. Also, the reproducibility capacity of the experimental setups were analysed through the uncertainty analysis and proving them to be able for future similar studies. The flow maps with their uncertainties could help understand the thresholds for each defined flow pattern region, and the plots of two-phase pressure drop variation with diameter confirmed the homogeneous model as a possible approach to calculate pressure drop if the uncertainties are considered.     

Capacitance sensor for void fraction measurement in water/steam flows

A capacitance sensor operating at RF range for void fraction measurements was developed. Two electrodes of the capacitor are mounted on the outer side of pipe walls. The variations in the percentage of phases in two-phase flow cause changes of the equivalent permittivity of the dielectric between the electrodes. The capacitor is connected in a resonant circuit of an oscillator tuned to high frequency of 80 MHz. The changes of frequency generated by the oscillator are the measure of the void fraction in the two-phase flow. An eight-channel system with capacitance sensors of this type was used for determination of the phase conversion along a steam injector.     

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.     

激光干涉仪数字测角的新方法及其应用

介绍了一种基于迈克耳孙干涉仪的精密角度测量系统,该系统利用迈克耳孙干涉仪在几何量测量中的干涉测量技术,通过转换将角位移转换为可以反映干涉光路中光程差变化的线位移,并通过相应电路对干涉条纹进行处理,从而实现了对大转角的精密测量。与以往类似系统相比,该系统具有结构简单、误差恒定、测量精度高、测角范围大、易于数字化等特点。同时,文章还对系统的构成原理、设计注意事项和精度等作了有关的理论分析。     

Three-way PLS regression and dual energy gamma densitometry for prediction of total volume fractions and enhanced flow regime identification in multiphase flow

Dual energy gamma densitometry and 3-way partial least squares regression were applied to quantify the total volume fractions and improve flow regime identification in multiphase flow. Multiphase flow experiments were carried out with formation water, crude oil and gas from different North Sea gas fields in Statoil׳s High Pressure Multiphase Flow Loop in Porsgrunn, Norway. Four different flow regimes were investigated (stratified wavy, slug, dispersed and annular). A traversable dual energy gamma densitometer was used to measure the fluid densities in the pipe. Partial least squares regression was previously applied to identify multiphase flow regimes and quantify volume fractions of gas, oil and water. That study showed promising results for flow regime identification but the predictions of the total volume fractions were not acceptable. In this study a new method combining gamma densitometry and 3-way partial least squares regression was applied in order to improve the quantitative estimation of the total volume fractions gained in the previous study. The proposed 3-way regression approach allows prediction of the total volume fractions directly using one model instead of multiple models which was reported earlier. The improved quantification of the volume fractions of gas, oil and water was used to improve the flow regime identification plots and increase the interpretability.The new 3-way prediction results for the volume fractions were significantly better than what was found earlier based on individual PLS models. The root mean square error of prediction for gas, oil and water from the 3-way PLS models were 4.1 %, 4.3 % and 4.6% respectively. All models reported were validated based on independent data (test set validation).     

一种不定长水尺图像水位测量方法

针对水尺图像水位识别中存在的多根水尺拼接、水尺拍摄不完整以及环境适应性差等问题,从摄影测量学角度提出一种复杂光照条件下不定长水尺图像水位测量方法。首先通过人工选取的标识点构建水尺在像素坐标系和世界坐标系之间的透视投影关系;然后利用水尺的颜色特性将水尺与背景分割并二值化;再根据二值化图像使用方差均值阈值法检测水位线位置;最终通过投影关系计算出水尺图像中水尺中线的表达式,并结合水位线位置计算出水面上水尺中线的真实长度,获得水位值。本文对水文站真实水尺图像进行了测量实验,将检测结果与遥测水位值进行对比,结果表明本方法提高了不定长水尺图像水位检测的可靠性,测量精度达到1 cm,检测分辨率为1 pixel,基本满足水文站水位监测要求。     

A non-intrusive probe for bubble profile and velocity measurement in horizontal slug flows

A new technique was developed for measuring the profile and mean velocity of elongated bubbles in horizontal air–water slug flows. It is based on the capacitance between two thin electrodes mounted on the external surface of a dielectric pipe, and has advantages in relation to the traditional parallel wire technique, since it is not intrusive, the presence of impurities in the liquid phase has no influence on the probe response, and it is applicable to very low electrical conductivity liquids, such as oils and deionized water. Tests were performed in an experimental facility with a 5 m long, 34 mm internal diameter Plexiglas pipeline. The elongated bubble mean velocity was determined by using a cross correlation technique applied to the signals coming from two identical capacitance probes, mounted 50 mm distant from each other. The results were compared with an empirical correlation from the literature. Discordance was observed only for flows near the flow pattern transition regions in the flow pattern map.     

铝电解槽连续测温方法研究

本文提出了利用温度平衡原理对铝电解槽进行连续测温的方法。由于采取了负反馈措施,能够用热电偶在电解槽外面对内部温度进行测量,而不受环境温度变化的影响。初步的实验表明,这种方法使得铝电解槽温度的低成本、高精度连续测量成为可能,可望在冶金行业获得广泛应用。     

虚拟式钢水连续测温仪

采用新型组合式陶瓷热电偶为温度传感器，以LabVIEW为开发平台，建立虚拟式钢水连续测温系统，解决了长期以来钢水测温连续性差、成本高、误差大、实时性差、劳动强度大等难题，利用多通道测温系统，还可以实现多点连续测温。有广阔的工业应用前景。     

Analytical investigation of an inductive flow sensor with arc-shaped electrodes for water velocity measurement in two-phase flows

An inductive flow sensor with spot-shaped electrodes (IFS-SE) is sensitive to the shape of the flow profile and is restricted to be used to measure the flow rate of axisymmetric single-phase flows in a circular pipe. In many cases of application, it is not possible to provide a fully developed flow profile. Therefore, the inductive flow sensor has to cope with flow profiles that are not fully developed. To improve the accuracy, an inductive flow sensor with a pair of arc-shaped electrodes flush-mounted on the internal surface of an insulating section of a pipe is proposed in this article to investigate the characteristics of vertical gas-water two-phase flows. The effect of the flow profile on the inductive flow sensor is analyzed. A key contribution of the present work is to estimate the relationship between the induced voltage and the velocity of the conductive phase in two-phase flows. The estimation is achieved by the analytical calculation of magnetic-inductive equations through the method of variables separation. The analytical solution is compared with the results from an ideal model and from numerical simulation. Experiments are conducted to calibrate the inductive flow sensor with arc-shaped electrodes (IFS-AE). It is noted that the proposed IFS-AE can be adopted to obtain the velocity of the conductive phase in two-phase flows by measuring the voltage induced on the arc-shaped electrodes.     

基于自动化排水集气原理的页岩含气量测试新方法

在岩石含气量测试方法现状调研基础上,详细介绍了自主研制的基于自动化排水集气原理的页岩含气量测试装置,阐述了仪器原理、功能,并采用6种不同气体在快、慢两个不同流速下,研究气体组成及流速对质量流量计法和自动化排水集气法测试精度的影响。结果表明,质量流量计法受气体组分及流速影响显著,尤其当烃类气体组分不确定或含水蒸气时,会出现较大误差,高流速条件下误差可达10%以上。自动化排水集气法计量精度高,误差在1%以内,且对流速变化不敏感,实现了高自动化与高精度。     

A new method for measurement of particle abrasivity

A modified micro-scale abrasive wear test has been used to study the abrasivity of a range of silica and calcium carbonate abrasives in aqueous slurries, against polymethylmethacrylate (PMMA) samples. The method involves the rotation of a cylindrical disc against the specimen surface in the presence of small abrasive particles, and generates a wear scar with an imposed geometry. It allows a wider range of particle sizes to be used than the more conventional ball–cratering method. For the abrasives used in these tests, differences in abrasivity by a factor of at least 16 were found. The main factor which influenced abrasivity was particle shape.     

A new laser measurement system for precision metrology

Laser measurement systems, based on optical heterodyne interferometry, have been a valuable tool for precision metrology for almost two decades. During this period measurement requirements have steadily increased without an accompanying improvement in system capabilities. This paper describes a new laser head, electronics and interferometers that satisfy present needs and have the attributes to meet future requirements.     

基于图像处理的连铸板坯测控系统

本文介绍了基于计算机图像处理连铸板坯长度测量和切割控制系统的硬件构成和软件功能。讨论了摄像机参数标定方法和系统测量误差。