Effects of water in oil and oil in water on single-phase flowmeters

The effect of two-phase flow on the performance of a range of single-phase flowmeters has been investigated experimentally using the National Standard Multiphase Flow facilities at NEL. The flowmeters tested were 2-inch and 4-inch positive displacement meters, venturi meters, helicoidal and flat-bladed turbine meters, 2-inch U-tube, 3-inch and 1.5-inch straight tube Coriolis meters and a 4-inch vortex shedding meter. The flowmeters were tested in oil flow with water and water flow with oil. The second component fractions were varied from 3% up to 15% by volume. The aim of the project was to quantify the effect of second-phase fluid components on the basic uncertainty of a range of single-phase. These tests have provided evidence of the suitability of particular flowmeters for two-component flow applications. Comparisons have been made between generic type and size of flowmeter. The oil-in-water and water-in-oil tests indicated that the uncertainty in the outputs of the flowmeters tested were generally within ±1% relative to the reference flowrates, although some errors as high as 5–10% were also observed. Most of the measurements from the turbine flowmeters and the positive displacement flowmeters were within ±0.4% of the reference flowrates.     

A regression-based model for prediction of flowmeters calibration cost in oil and gas industry

Measurement of liquid flowmeters is one of the most expensive processes in the oil and gas industry. Estimating calibration costs for such flowmeters in the oil and gas industry is complicated task for the decision-making team. The difficulties arise as a result of the presence of numerous uncertain factors that influence calibration charges such as the fabrication of special tools and spools. Consequently, this paper proposes a data-driven approach for estimating the calibration costs of flowmeters in oil and gas industry. A regression-based model is developed to predict the future calibration costs of flowmeters. The factors that affect the costs of calibrating flowmeters are identified from literature and interviewing local experts. The results indicated that the most important factors influencing the cost of liquid flowmeter calibration include flowmeter size, calibration method, flowmeter type, flowmeter class and calibration factor. The developed model is validated using 577 new data points of flowmeters calibration costs. The findings showed the uncertainty of the proposed model within 98% confidence level. An accurate calibration cost for liquid flowmeter will help to manage the operational and services costs.     

Experimental investigation of gas-liquid flow in a vertical venturi installed downstream of a horizontal blind tee flow conditioner and the flow regime transition

A venturi device is commonly used as an integral part of a multiphase flowmeter (MPFM) in real-time oil-gas production monitoring. Partial flow mixing is required by installing the venturi device vertically downstream of a blind tee pipework that conditions the incoming horizontal gas-liquid flow (for an accurate determination of individual phase fraction and flow rate). To study the flow-mixing effect of the blind tee, high-speed video flow visualization of gas-liquid flows has been performed at blind tee and venturi sections by using a purpose-built transparent test rig over a wide range of superficial liquid velocities (0.3–2.4 m/s) and gas volume fractions (10–95%). There is little ‘homogenization’ effect of the blind tee on the incoming intermittent horizontal flow regimes across the tested flow conditions, with the flow remaining intermittent but becoming more axis-symmetric and predictable in the venturi measurement section. A horizontal (blind tee) to vertical (venturi) flow-pattern transition map is proposed based on gas and liquid mass fluxes (weighted by the Baker parameters). Flow patterns can be identified from the mean and variance of a fast electrical capacitance holdup measured at the venturi throat.     

Theoretical study of vertical slug flow measurement by data fusion from electromagnetic flowmeter and electrical resistance tomography

Electrical resistance tomography (ERT) can be used to obtain the conductivity distribution or the phase distribution of gas/liquid flows (e.g. slug flow). Using proper parameter models and flow regime identification models, the measurement of phase size, void fraction, and pattern recognition can be realized. Electromagnetic flowmeters have been used to measure conductive single-phase liquid flows. However, neither ERT nor electromagnetic flowmeters (EMF) can provide accurate measurement of gas/liquid two-phase flows. This paper presents an approach to fuse the information from ERT and an electromagnetic flowmeter. A model for the measurement signal from the electromagnetic flowmeter has been developed based on the flow pattern and the phase distributions, which are obtained from the reconstructed images of ERT, aiming to reduce the measurement error of the electromagnetic flowmeter and enhance the measurement accuracy. Through the simulation research of virtual current density distribution, the feasibility of fusion of electromagnetic flowmeter and ERT to measure gas/liquid two-phase vertical slug flow is verified. By theoretical analysis, the relationship between the output of electromagnetic flowmeter and flow parameters is established. The electrical potential difference of the electromagnetic flowmeter, average velocity, volume flow rate and gas void fraction between the bubble size and location are also investigated. The fusion approach can be used to measure vertical slug flows.     

Water flow measurement in large bore pipes: an experimental comparison between two different types of insertion flowmeters

In this paper the metrological behavior of two different insertion flowmeters (magnetic and turbine types) in large water pipes is described. A master-slave calibration was carried out in order to estimate the overall uncertainty of the tested meters. The experimental results show that (i) the magnetic insertion tested flowmeter performs the claimed accuracy (+/- 2%) within all the flow range (20:1); (ii) the insertion turbine tested meter, instead, reaches the claimed accuracy just in the upper zone of the flow range.     

容积式流量计的研究现状及展望

容积式流量计计量精度高,受环境影响较小,在航天船舶、化学工程、机电一体化等领域得到了广泛的应用。依据容积式流量计不同的内部转子结构,将其分为齿轮式、活塞式、刮板式和其他样式,并分别描述了各类容积式流量计的计量原理以及优缺点。在此基础上,总结了近十年来国内外研究人员对容积式流量计的研究成果,并针对不同样式流量计各自的缺陷列举了已有的改善方案。最后,针对容积式流量计可能的发展方向进行了探讨。     

Accurate mass flow and density of bubbly liquids using speed of sound augmented Coriolis technology

Speed of sound augmented Coriolis technology utilizes a process fluid sound speed measurement to improve the accuracy of Coriolis meters operating on bubbly liquids. This paper presents a theoretical development and experimental validation of speed of sound augmented Coriolis meters. The approach utilizes a process fluid sound speed measurement, based on a beam-forming interpretation of a pair of acoustic pressure transducers installed on either side of a Coriolis meter, to quantify, and mitigate, errors in the mass flow, density, and volumetric flow reported by two modern, dual bent-tube Coriolis meters operating on bubbly mixtures of air and water with gas void fractions ranging from 0% to 5%. By improving accuracy of Coriolis meters operating on bubbly liquids, speed of sound augmented Coriolis meters offer the potential to improve the utility of Coriolis meters on many existing applications and expand the application space of Coriolis meters to address additional multiphase measurement challenges.The sources of measurement errors in Coriolis meters operating on bubbly liquids have been well-characterized in the literature. In general, conventional Coriolis meters interpret the mass flow and density of the process fluid using calibrations developed for single-phase process fluids which are essentially incompressible and homogeneous. While these calibrations typically provide sufficient accuracy for single-phase flow applications, their use on bubbly liquids often results in significant errors in both the reported mass flow, density and volumetric flow. Utilizing a process fluid sound speed measurement and an empirically-informed aeroelastic model of bubbly flows in Coriolis meters, the methodology developed herein compensates the output of conventional Coriolis meters for the effects of entrained gas to provide accurate mass flow, density, volumetric flow, and gas void fraction of bubbly liquids.Data presented are limited to air and water mixtures. However, by influencing the effective bubble size through mixture flow velocity, the bubbly liquids tested exhibit decoupling characteristics which spanned theoretical limits from nearly fully-coupled to nearly fully-decoupled flows. Thus, from a non-dimensional parameter perspective, the data presented is representative of a broad range of bubbly liquids likely to be encountered in practice.     

Installation effects on ultrasonic and electromagnetic flowmeters: a model-based approach

The paper describes the basic ideas of a model-based installation-effects analysis method and presents results from a collaborative research programme being conducted at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD, USA, and at Tampere University of Technology in Finland. The analysis method is based on a combination of flow modelling and flowmeter modelling. In this paper, installation effects on electromagnetic and travel-time-difference ultrasonic flowmeters are discussed. The installation cases are single elbow and double elbow out-of-plane piping configurations. The results show that significant shifts from ‘ideal’ meter performance can occur in such disturbed flow conditions. The flowmeter modelling results also show that these significant shifts can be reduced by altering the operational arrangements and performance characteristics of the meters. It is concluded that such flowmeter modelling can be very useful in: (1) redesigning flowmeters to make them less susceptible to installation effects, (2) constructing new meters, or (3) arranging special meter configurations to deal with specific disturbed flows.     

Investigation into calibration performance of small volume prover for hydrocarbon flow

Several kinds of commercial flowmeters, namely, Coriolis flowmeters, turbine meters, ultrasonic flowmeters, and positive displacement flowmeters, have been calibrated using the primary standard for hydrocarbon flow measurement in Japan (which is based on static and gravimetric methods with a flying start and finish) and a small volume prover (SVP) at the same calibration condition in order to investigate the performance of the SVP. The differences in calibration results for the mechanical flowmeters between the primary standard and the SVP apparently depend on the flow rate, although the results show agreement within 0.04%. The computer-based flowmeters, which have a time delay in the output pulse signal, indicated larger differences due to the effect of the sudden flow rate change caused by the proving action of the SVP at larger flow damping times.     

Particle image velocimetry flowmeter for natural gas applications

Ultrasonic flowmeters are currently used in the measurement of large natural gas flow. However, their high sensitivity to noise signals can cause measurement errors and direct economic losses. Particle image velocimetry (PIV) measurement technology has several advantages, including convenient installation and maintenance, and strong anti-interference ability, thereby presenting an innovative idea for its application in the field of flow measurement. In this paper, a cyclic integration method is proposed for the application of PIV technology in flow measurement of natural gas. The results show that PIV flowmeter and ultrasonic flowmeter are basically consistent, and the maximum deviation is about 2%. confirming the feasibility of the PIV flowmeter. Therefore, this study provides a theoretical and technical reference for the development of a PIV flowmeter for natural gas.     

Evaluation of flowmeters for heat metering

Heat flowmeters are expected to be reasonably priced, be very reliable, and have high measurement accuracy. Various types of heat flowmeters have been developed and they are widely used in large residential and industrial buildings. In this study, three types of heat flowmeters (turbine, electromagnetic and ultrasonic) were tested for accuracy, effect of installation position and vibration, durability and performance in the field for several installation positions and in the presence of vibration. We used a liquid flow standard system and a customized durability test system in accordance with the International Organization of Legal Metrology (OIML) R 75-2 heat meter testing method. The field test was conducted in eight different locations from winter to summer. All flowmeters were calibrated before and after the field test, and the measurement deviation and the relative expanded uncertainty were calculated. The mean deviations obtained were–0.21%,–0.07%, and 0.11%, with the relative expanded uncertainties 0.48%, 0.17%, and 0.40% for turbine, electromagnetic, and ultrasonic flowmeters, respectively. The results of position and rotation tests, mean deviations by rotation angles at 90°, 180°and 270°relative to 0°(horizontal position) were–1.24%,–1.07% and–0.80%, respectively. For the vibration tests at 1 m/s² and 5 m/s² vibration acceleration, the turbine flowmeter, the electromagnetic flowmeter and the ultrasonic flowmeter showed deviations that ranged from −0.2% to −0.5%, −0.6% (2.6 m³/h), and 0.0% (negligible), respectively. In the durability tests, the accuracy of all three types of heat flowmeters remained at ±1% or less, showing sufficient durability. In the field test, the deviation of the turbine flowmeter and the ultrasonic flowmeter showed ±2.5% or less deviation. However, the electromagnetic flowmeter seems to be inaccurate below 6.9% of the maximum flow rate.     

High-frequency transducers and correlation method to enhance ultrasonic gas flow metering

Research activities carried out in past years have shown that in gas networks some constraints exist on the frequency at which ultrasonic transducers can be operated. The study of the transmission and attenuation of the signal and noise mechanisms gives us a defined suitable frequency range (K.R. Wild, A European collaboration to evaluate the application of multi-path ultrasonic gas flow meters, paper presented at 4th International Symposium on Fluid Flow Measurement, Denver, CO, 1999). A working frequency of 500 kHz proves to be the most suitable to avoid noise effects. This frequency is above the noise level detected in gas pipelines. Moreover, the signal loss due to attenuation of ultrasound in gas is still negligible.In parallel, the use of this frequency allows the application of efficient numerical techniques such as the cross-correlation method for signal processing. An initial process based on this method has been developed for gas flowmeters. It provides low uncertainty for the parameters involved in the flow measurement process.A single-path flowmeter equipped with this system has been tested on the Gaz de France test facilities. Its accuracy is better than 1.5% from 250 to 1000 m³/h without initial adjustment. An auto-calibration process also forms part of the system, using a systematic comparison between ultrasonic measurement of sound velocity and a theoretical approach. The signal-to-noise ratio remains large enough to perform the measurements correctly, even with a control valve installed close to the flowmeter.     

Installation effects on vortex shedding flowmeters

Numerous measurements of the effects of pipe fittngs on vortex shedding flowmeters are carried out as a contribution to flow metering standards. A water test line of 150 mm diameter is used in the experiments covering a Reynolds number range of about 2 × 10⁵ to 10⁶. The effects of six kinds of piping configurations are examined at various upstream straight pipe lengths and all four kinds of liquid vortex shedding flowmeters, which were commercially available in Japan, are tested. The vortex shedding flowmeters are compared with a turbine meter in experiments designed to evaluate reproducibility of measurements. The uncertainty of the measured data is estimated at about 0.1%. It is found that the magnitude of each installation effect strongly depends on the design of the flowmeter. The experimental results are presented in detail and a table is given of the minimum upstream straight pipe lengths needed to suppress the effects to less than 0.5% for each of the tested flowmeters. This can be used as guidance in the installation of vortex shedding flowmeters.     

数字信号处理技术在科氏质量流量计中的应用

科氏质量流量计是目前应用范围最广、发展速度最快的流量计之一。数字信号处理技术是科氏质量流量计的核心技术,直接决定其测量精度、测量稳定性等性能指标;而流量传感器输出信号的数学模型是信号处理的依据和基础。国内外学者提出了多种信号处理方法,但是,没有根据不同的信号模型和不同的应用场合对各种信号处理方法进行比较和评价。为此,根据不同数字信号处理方法的特征量提取原理,分析了其具有的优缺点。针对科氏质量流量计单相流、批料流与气液两相流测量这3种典型应用场合中存在的关键技术问题,依据随机游动信号模型、突变信号模型和自回归滑动平均(ARMA)信号模型,分别从计算精度、响应速度、收敛性、抗干扰能力和对参数变化的敏感度等方面,对不同信号处理方法进行考核和对比,确定了3种典型应用场合下,解决关键技术问题,性能最佳的数字信号处理方法。     

Measurement of steam flow rates using a clamp-on ultrasonic flowmeter with various wetness fractions

Most of the heat in industrial plants is supplied by steam. To minimize energy waste, measuring the steam flow rates in existing pipes is important. Clamp-on ultrasonic flowmeters are used for this purpose, for which the sensors are attached to the pipe wall. However, flow conditions that can be used are limited because the signal-to-noise ratio of the ultrasonic signal in a steam flow is low. Furthermore, the steam wetness increases with heat losses, which may affect measurement results. Therefore, flow rate measurements in wet steam flows using clamp-on ultrasonic flowmeters have not been fully established. In this study, steam flow rates with various wetness fractions and system pressures were measured using a laboratory-made clamp-on ultrasonic flowmeter. The results show that flow rates in wet steam could be determined within a 10% error under general conditions in a steam piping system, although the conversion factor from line-average to area-average velocities was calibrated in superheated conditions, and the speed of sound in saturated conditions at each pressure was used. However, the error of the flow rates tended to increase with the wetness fraction and was biased toward positive values. The speed of sound and liquid volume fraction were evaluated at different wetness fractions. The flow rate error due to the change in sound speed was less than 1%, and 1.2% of the flow rates were overestimated owing to the liquid volume fraction. The velocity distribution in wet steam was considered different from that in the superheated steam owing to the existence of the liquid phase, and the change in velocity profile may lead to an overestimation of the steam flow rates in the wet steam condition.     

差压式湿气两相流量计的校准

伴随着工业技术的不断发展,湿气流量的测量日益增多,湿气流量计的校准工作日益迫切,亟待解决。本文介绍了在湿气流量计量领域中广泛应用的差压式湿气两相流流量计的原理,并在天津大学电气与自动化工程学院的中压闭环湿气标定装置中对其进行了校准,对该流量计的气相和液相的不确定度进行了评定,为今后开展相关流量计的校准工作提供了参考和数据支持。     

A method based on a novel flow pattern model for the flow adaptability study of ultrasonic flowmeter

Ultrasonic flowmeters are widely used in industry for accurate measurement. Flow adaptabilities of meters in non-ideal flow fields are usually concerned about by researchers. This paper presents a theoretical analysis method to study the measurement performance of ultrasonic flowmeter. For the specific water flow in single elbow pipe, a novel three-dimensional flow pattern model is invented by the trust region Newton algorithm based on computational fluid dynamics simulation results. In order to verify the correctness of the model, a typical ultrasonic flowmeter with single diametric acoustic path is mainly analyzed. By comparing flow adaptabilities of the meter downstream of the single elbow with both the novel theoretic model analysis approach and simulation method, good agreement is achieved. It is indicated that both the three-dimensional model and its invention method are valid for this study, which is not only helpful to get knowledge of characteristics of disturbed flows, but also provides a practical method to study the flow adaptability of ultrasonic flowmeter in non-ideal flow fields.     

Coriolis mass flow measurement at cryogenic temperatures

With the growing interest in liquefied natural gas (LNG) in the energy market, Coriolis mass flowmeters have been applied to many applications in the distribution of LNG. Since Coriolis flowmeters are normally calibrated at around room temperatures, measurements for LNG at cryogenic temperatures present a challenging condition. Firstly, a theoretical analysis for Coriolis mass flow sensors is provided considering the major changes of material properties (Young’s modulus and thermal expansion) at cryogenic temperatures. Then, a practical approach which can be used to correct the flow calibration factor obtained at a reference condition is presented. Finally, flow test results obtained from NIST’s cryogenic calibration facility are provided. Based on the results, it can be concluded that if a Coriolis flowmeter is calibrated at a reference condition and the flow calibration factor is corrected considering the non-linearity of Young’s modulus and thermal expansion change with temperature, it can still provide very accurate mass flow measurement even at cryogenic temperatures.     

Development of side wall type permanent magnet flowmeter for sodium flow measurement in large pipes of SFRs

Sodium cooled Fast Reactors (SFR) require measurement of liquid sodium flow in its primary and secondary circuits. For the primary system of the pool type concept of SFR design, flowmeters have to be immersed in sodium pool and require flow sensors which can withstand high temperatures up to 550 °C, nuclear radiation and chemically reactive sodium environment. Secondary circuits and safety grade decay heat removal (SGDHR) circuits of SFR need flow measurement in stainless steel (SS) pipes of diameter varying from 15 mm to 800 mm. For small pipes, flowmeters with permanent magnet flowmeter with ALNICO-V magnet assembly is the unanimous choice. Conventional permanent magnet flowmeters (PMFM) for large pipelines become bulky, heavy and have installation problems. For sodium flow measurement in large pipelines a few other alternate methods are considered. In the case of Prototype Fast Breeder Reactor (PFBR), which is at an advanced stage of construction at Kalpakkam, flow in the 800 mm diameter secondary main circuit is measured by means of a bypass flowmeter. Other sensors that could be deployed include eddy current flowmeters (ECFM), which are introduced into the pipe to measure flow velocity in the pipe, ultrasonic flowmeters and permanent magnet based side wall flowmeters. In permanent magnet based side wall flowmeter (SWFM), a permanent magnet block is mounted on one side of the large pipe and the magnetic field produced by the magnet penetrates through the pipe and interacts with the flowing sodium and induces an electro motive force (emf) proportional to the flow. This is a compact, cost effective and fairly accurate method for flow measurement in large pipelines of SFR circuits. SWFM is suitable for pipelines of 100 mm and above. In the present work a side wall flowmeter for 100 mm pipe is designed, manufactured, calibrated and tested in an existing sodium facility. Voltage signal developed in SWFM for different flowrates was simulated with three dimensional Finite Element Model (FEM) and validated with experimental results. Effect of asymmetric magnetic field on flowmeter voltage signal and dependence of flowmeter voltage signal on position of electrodes was also analyzed with model. The feasibility of use of this type of flowmeter for large pipelines of SFRs is demonstrated.     

腰轮流量计准确度的影响因素

腰轮流量计是目前原油输送过程中精确度高,使用较广的一种计量器具,介绍腰轮流量计的结构、工作原理、检定过程,分析影响腰轮流量计准确度的粘度、温度、压力、流量、介质等因素,依据实际运行情况提出具体做法。