Effects of gas leaks in oil flow on single-phase flowmeters

The effect of gas entrainment in oil 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 4-inch and 2-inch positive displacement, venturi, helicoidal and flat-bladed turbine meters and 2-inch U-tube and 1.5-inch straight tube Coriolis meters. The flowmeters were tested in oil flow with gas fractions 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 flowmeters and, as a consequence, identify which generic types of single-phase flowmeter were most suitable in applications where such components may be present. 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. At low gas fractions, the positive displacement and venturi flowmeters were more accurate than the other meters and estimated the total flowrate to within ±2%. Over 9% gas fraction, there was an improvement to the response from some of the flowmeters with increasing gas fractions. This was considered to be indicative of improved mixing in the flow.     

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 technique for low cost calibration of large electromagnetic flowmeters

The need for calibration of electromagnetic flowmeters adds considerably to the cost of these instruments especially in the larger sizes. This paper discusses a proposed technique for calibration of large electromagnetic flowmeters which avoids the need for a calibration flow rig. The technique consists essentially of filling the flowmeter tube with water, operating the electromagnet as it would be operated in normal flowmeter operation and measuring the axial component of the eddy current electric field in the water over each electrode. This allows the calibration factor for a flat velocity profile to be determined.     

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.     

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。     

Liquid low-flow calibration rig using syringe pump and weighing tank system

A calibration rig consisting of a syringe pump and a weighing tank system that can operate in the flow rate range of 0.02–60 L/h was developed in this study. This paper discusses the design considerations of the calibration methods, the development of the rig, the calibration results, and the uncertainty analysis conducted on the rig. A weighing tank system that minimizes the effects of outlet tube contact and evaporation was developed. The syringe pump system was designed using a servomotor, a precise ball screw, and a linear encoder, and it was calibrated using the developed weighing tank system via the standing start and stop method over the target range of flow rates with light oil and industrial gasoline. Several flowmeters were calibrated using the syringe pump via the flying start and finish method. During the flowmeter calibration stage, the effect of the evaporation error was eliminated because the calibration rig can form a closed pipeline system. The influence of dissolved gas and the position dependence of the syringe pulse factor on the calibration accuracy were investigated experimentally. As a result, all obtained syringe pulse factors were found to be within ±0.02% of each other. The preliminary expanded uncertainties (k=2) of the calibration rig were estimated to be 0.066% and 0.070% for mass and volumetric flows, respectively.     

Developing a model for prediction of helical turbine flowmeter performance using CFD

In this article, a numerical model for prediction of turbine flowmeter performance is proposed. This model is consists of a novel iterative algorithm, based on torque balance theory. Despite previous studies, the effect of bearings drag torque on finding balance point is considered. Using an in-house code, the bearings torque of the flowmeter is calculated based on the finite difference method. The three-dimensional steady state internal flow field of turbine flowmeter is obtained from the Computational Fluid Dynamics (CFD) simulations. For evaluation of the model׳s accuracy the experiments on a 6 in. helical turbine flowmeter has been carried out for crude oil and water. Consequently, the K-factor and also linearity error for cases of fluids are achieved. The results were compared with experimental data and it is found that the numerical model results are reasonably accurate. Therefore, by using the proposed model, the heavy cost of design and optimization of turbine flowmeters can be reduced.     

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.     

双转子燃油流量计校准试验及结果

在航空发动机性能和工作特性试飞中,燃油流量的准确测量对发动机工作指标和性能计算有着重要的影响。和传统单转子流量计相比,双转子燃油流量计有响应更快、重复性好、精度高、量程更宽广等优点,被广泛地应用在航空领域。通常,航空发动机由于安装空间的原因,燃油流量计的进出口平直段难以满足整流的需要。因此,需要装机后对燃油流量计再次进行校准。本文通过标准流量台对安装试验件的某型双转子流量计进行校准,将试验结果与厂家提供的校准曲线进行对比,发现有一定的偏差。通过对校准结果的不确定度合成,其结果小于2‰。还得到了K因子校准特性曲线图,为双转子流量计的工程应用提供了技术支持。     

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。     

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.     

Numerical analysis of installation effects in Coriolis flowmeters: Single and twin tube configurations

A fully coupled, partitioned, numerical model that accounts for fluid–structure interaction is applied for a study of the installation effects of Coriolis flowmeters. The modeled configurations include a single straight-tube full-bore flowmeter and two different twin tube flowmeters with straight and U-shaped measuring tubes. Three different flow disturbance elements positioned upstream of the flowmeter are considered in the study, as well as two different types of flow splitters in the case of the twin tube configurations. The installation effects are estimated by comparing the mass-flow sensitivities under the disturbed and fully developed flow conditions at the inlet of the flowmeter. For the modeled twin tube flowmeters they are found to be of the order of one-tenth of a per cent. These relatively small values of the installation effects are related to the presence of flow splitters and to the averaging of the motion of both measuring tubes in the twin tube configurations. Similarly, averaging the response from two sensor pairs instead of only a single sensor pair reduces the circumferential variations and the peak values of the installation effects for asymmetric flows in the single straight-tube flowmeter.     

包含电极尺寸及位置信息的电磁流量计干标定模型

现有电磁流量计干标定模型中,电极尺寸、位置均被作了理想化处理,即假设电极尺寸无穷小、电极位于测量管段正中间的两个对称点上,两对称点连线与磁场垂直。这类理想化的模型与实际情况差异较大,限制了干标定的精度,并对产品一致性提出了很高的要求。针对这一问题,采用分离变量法建立了包含实际流量计电极尺寸及位置参数的电磁流量计干标定模型,比现有干标定模型更接近于实际流量计,有利于提高干标定精度,降低对产品一致性的要求。通过与现有模型及数值仿真的对比分析,验证了该模型的准确性。     

基于DSP的低成本涡街流量计信号处理系统

涡街流量计易受噪声影响，现场测量精度得不到保证，节程比受限。本文选用片上资源丰富的TMS320LF2407A DSP芯片作为处理器，研制相应的数字信号处理系统。系统选用数宁滤波加频谱分析的信号处理方法处理传感器信号，提高仪表抑制噪声的能力，扩展量程比；模拟信号调理部分加入限幅滤波电路，解决传感器信号强度变化大、需要调整硬件电路参数的问题。该系统体积小、成本低、功能齐全，并可与不同口径的一次仪表匹配。目前该系统已通过实验标定，并应用于工业现场。     

On-line viscosity measurement using Coriolis mass flowmeters

Industrial viscometers are available in large variety to measure for both Newtonian and non-Newtonian fluids. A simple system which uses the Coriolis mass flowmeter as a capillary tube has a growing range of applications. Employing the capillary principle, the rheological properties of time-independent Newtonian fluids and some non-Newtonian fluids can be successfully measured. The method applies readily available and proven components, namely mass flowmeters and differential pressure transducers. Basic viscosity calibration can be achieved with suitable software. To add viscosity measurement capability to an existing flowmeter site in most cases requires only the installation andd connection of a suitable differential pressure transducer.     

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。     

Soft sensor for an orifice flowmeter in presence of disturbances

Measurements using an orifice flowmeter are widely used in industry. In certain instances, the output of the flowmeter may be corrupted due to plate contamination, changes in fluid density, or incorrect insertion of the plate. This paper describes a method for estimating the correct output in the presence of such disturbances. First, a linear parameter-varying model of the orifice flowmeter is developed using data extracted from computational fluid dynamics simulations. The simulation and experimental output are found to have an average deviation of 6.5% and 3.49% in terms of the differential pressure and discharge coefficient, respectively. Observer-based estimators for the linear parameter-varying models are developed for different combinations of the settling time and maximum overshoot. These estimators enable the disturbance-induced output to be corrected close to the true value. The error in the disturbed output due to plate contamination is reduced from 45% to 0.82%. Similarly, the error due to an accidental change of plate decreases from 76% to 2.03%. Thus, the proposed estimator can be used to nullify the disturbances induced in the measurements from orifice flowmeters.     

Investigation of the batch measurement errors for single-straight tube Coriolis mass flowmeters

Batch flow is a typical method for calibrating Coriolis flowmeters. It is also an important application for Coriolis flowmeters in the process industry. Batch processes of short duration or from empty have been identified as an important development for Coriolis flowmeters. The measurement of total mass by a commercially available single-straight tube Coriolis flowmeter compared with a weigh scale is presented in this paper. A theoretical understanding for short batch is also provided by numerical simulations of both deterministic and probabilistic parameters. The simulation results agree with the batch tests and may, at least partially, explain the experimental findings.     

BS 7405: The principles of flowmeter selection

With so many different types of flowmeter available from so many sources of supply, flowmeter selection is becoming increasingly difficult. The paper looks at the principles of flowmeter selection and lists the factors that affect the choice of technology and even design variants within a particular technology. The new BS 7405 classifies closed conduit flowmeters into 10 major groups and this grouping was used in the basic layout of the standard. More than 45 variables were identified as the most important factors in selection and these have also been grouped into five major areas. These five areas can be considered in turn, depending on which is the most important, against the required application specification. The paper looks at the mechanics of flowmeter selection and highlights the importance of specification before the elimination process is begun. The standard only allows selection of a flowmetering type and does not give guidance or recommendations on suppliers.     

科里奥利质量流量计检定误差分析与对策探讨

科里奥利质量流量计在能源和化工品等领域的贸易结算中应用较广,其具有测量效率高、精度准确和运行稳定可靠的特点。目前,人们对科里奥利质量流量计的使用提出了更高的精度要求,因此有必要进行其检定误差的消除处理。以万华(宁波)化学有限公司2019年的大修项目为例,在阐述流量计检定准确性影响因素的基础上,就项目检定与误差分析过程进行深入分析,指出科里奥利质量流量计检定误差处置办法,期望能进一步提升科里奥利质量流量计检定精度,继而为相关行业贸易实现和经济发展提供有效保证。