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.     

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.     

A study of mass flow rate measurement based on the vortex shedding principle

Mass flow rate measurement is very important in the majority of industry processes because the mass of fluid is not affected by ambient temperature and pressure as the volume will be. Conventional mass flow rate is normally derived from the volumetric flow rate multiplied by fluid density. The density can be obtained by a densitometer or calculated according to the temperature and pressure measured by a thermometer and pressure gauge respectively. However the measurement accuracy is not always satisfactory. Flowmeters directly measuring mass flow rate have been studied and developed recently, such as Coriolis and thermal flowmeters. Unfortunately they still have some limits in practical applications. A new method in which mass flow rate can be directly measured based on the vortex shedding principle is presented in this paper. As a vortex flowmeter, von Kàrmàn vortex shedding is generated by a bluff body (vortex shedder), leading to a pressure drop and pressure fluctuation. A single differential pressure sensor is employed to detect the pressure difference between upstream and downstream sides of the vortex shedder. Both vortex shedding frequency and pressure drop are contained from the output signal of the differential pressure sensor, so that the mass flow rate can be obtained from the pressure signal. Numerical simulation has been done to analyze the characteristics of the fluid field and design the measurement device. The Computational Fluid Dynamics (CFD) codes Fluent were used in the numerical simulation. Experiments were carried out with water and gas, and the results show that this method is feasible and effective to measure the mass flow rate. This method has also robustness to disturbances such as pipe vibration and fluid turbulence.     

Limit moment for a smooth pipe bend under in-plane bending

A lower bound for the limit moment of a smooth circular pipe bend of uniform thickness is calculated with no restrictions on the geometry except those of thin shell theory, though the bend angle and the effect of any straight length attachments are not considered. Results of the analyses suggest that the (bend radius)/(pipe radius) ratio is of importance as well as the pipe factor (bend radius x thickness)/(pipe radius)², which is usually assumed to be the only important geometric parameter.     

Systematic investigation of pipe flows and installation effects using laser Doppler anemometry—Part I. Profile measurements downstream of several pipe configurations and flow conditioners

The first part of this paper reports on an automated facility designed to investigate the influence of disturbed flows in pipes on the shift of the error curves of gas flowmeters in situ. This facility can be equipped with several pipe configurations (single and double bends, convergent and divergent sections, straight pipes up to 40 diameters in length etc.) as well as with various types of flow conditioners. It works with atmospheric air at flowrates of up to 5500 m³/h. A two-component semiconductor Laser Doppler Anemometer (LDA) is used to measure the spatial velocity and turbulence fields of the flow along the entire cross section in front of the flowmeter to be investigated. More than 150 velocity distributions have been determined for different pipe configurations at several flowrates and data have been collected to describe the corresponding flowmeter's behaviour. Some typical velocity profiles for the most usual pipe elements and flow conditioners are shown.

The second part of the publication, which will be presented in the following, compares the changes in the meter behaviour with the specific development of the flow characteristics downstream of the pipe configurations investigated. The model found to explain these metering effects will be described, evaluated and verified.     

Study on flow characteristics around the thermowell

In the paper, the effects of different Reynolds numbers on the flow and dynamic characteristics of the thermowell were studied. The results show that a “downwash” phenomenon occurs in the thermowell wake flow field, a “tip” vortex exists on the right, and a “mushroom” vortex lays at the bottom of the free end of the thermowell. The lengths of the reflux zone and the forms of vortex shedding are different on the different horizontal sections of a thermowell. With the increase of the Reynolds number, the size of the “mushroom” vortex gradually decreases, and the “tip vortex” gradually increases. At the same horizontal section, the length of the recirculation zone becomes shorter with the increase of the Reynolds number, and the vortex shedding form gradually changes from “2S” shape to the straight line shape. In the region below 50% height of the thermowell, with the increase of Reynolds number, the boundary layer separation line gradually moves forward, both flow resistance of the casing and “downwash” phenomenon gradually increase, and both lift force around the casing and vortex shedding frequency in the wake decrease. The flow resistance and vibration induced by vortex shedding are the leading causes of thermowell damage.     

Velocity profile effects in Coriolis mass flowmeters: Recent findings and open questions

The aim of this paper is to discuss velocity profile effects in Coriolis flowmeters and to review related research work. The measurements made by Coriolis flowmeters are dependent upon the steady flow velocity distribution within them whenever certain features of the fluid vibrational fields are not uniform inside the measuring tube. This dependence is confirmed by simulation results on two straight tube configurations, one operating in a beam-type mode and the other in a shell-type mode. Findings to date and open questions regarding velocity profile effects in Coriolis flowmeters are discussed for both fully developed and disturbed inlet flow conditions.     

液电混合直线驱动系统耦合特性及位置控制

液压系统与电-机械系统是广泛应用于航空航天、工业、非道路移动机械等领域的两种不同驱动方案。在实际中,两者通常单独使用,电-机械驱动方案能效高,但承载能力弱,液压驱动方案功率密度大、动态响应快,但能量效率低。为此,结合两个驱动方案优点,集成设计电-机械执行器与液压缸,构建一种新型液电混合直线驱动系统,分析系统工作原理及两个非相似驱动子系统耦合特性、力纷争现象及其影响。在此基础上,提出一种电-机械驱动单元运动控制与液压驱动单元力控制的调控方案。研究结果表明,采用所提调控方案可减轻两个非相似驱动子系统耦合作用,在液压阀低压损的同时,可获得良好的位置控制特性。新型液电混合直线驱动系统将为液压系统和电-机械系统的进一步发展提供新思路。     

Beta ratio, swirl and Reynolds number dependence of wall pressure in orifice flowmeters

Experimental work has been performed in an effort to gain a better understanding of the flow field inside orifice flowmeters and the pressure field generated on the walls of the pipe and orifice plate. As a part of a larger study, extensive wall pressure measurements have been made on the pipe wall from four pipe diameters upstream of the orifice plate to six pipe diameters downstream, as well as on both the upstream and downstream faces of the orifice plate. These measurements were performed for Reynolds numbers of 54 700; 91 100 and 122 800; for beta ratios of 0.50 and 0.75 with air as the working fluid. An adjustable swirl plate was installed, which was used to impart varying amounts of swirl into the flow upstream of the orifice plate. For each swirl case, Pitot and static pressure probes were used to characterize the upstream flow field while the pipe wall and orifice plate surface pressures were measured.     

高比转速双向泵马鞍区流动特性分析

为研究双向泵在正、反向运行时非稳定区的内流特性,以名以比转速为1600的双向轴流泵为研究对象,采用标准k-ε湍流模型对双向泵进行了正反向、多工况下的非定常数值模拟,比较了正、反向马鞍区内泵的内流特征及压力脉动变化情况,结果表明:反向时鞍型曲线出现的流量减小,马鞍区范围变窄;在所研究工况,正、反向运行时在叶片进口前靠近壁面处、出口后靠近轮毂处以及导叶内均出现了较大尺度漩涡,反向时,叶轮前的大尺度漩涡向上游移动,在轮毂后也形成了较大的回流区,同时,由于流场的非稳定特性,正向在1²、42、4⁵倍转频,反向在05倍转频,反向在0²倍转频出现了明显的压力脉动。     

上下游闸阀对内锥流量计性能影响的实验研究

旨在认识恶劣流场对内锥流量计性能的影响,利用上下游闸阀实现对流场的扰动,设计内径为100 mm的实验样机一台.实验介质为常温水,雷诺数范围0.1×10~5～4.5×10~5.实验分基线实验与闸阀开度实验2种形式,累计65组,上游闸阀开度分别为75%/50%/25%.下游闸阀开度分别为100%/50%,安装形式13种,等效直径比分别为0.45/0.55/0.65/0.75/0.85.提出平均流出系数相对误差、不确定度和附加不确定度作为安装条件恰当与否的主要评价标准.实验结果给出了12种不同安装形式的直管段建议长度,并与国外研究结论进行了比较.等效直径比为0.45/0.55时,前直管段均为3D;等效直径比为0.65/0.75/0.85时前直管段均为5D.     

热电离飞行时间质谱仪性能评价

本工作介绍了实验室自制的热电离飞行时间质谱仪（TI-TOF-MS）的基本结构、仪器运行参数和性能特点等。离子源产生的离子在推斥电压作用下进入聚焦透镜,然后进入垂直引入反射式的飞行时间质量分析器,最后到达检测器。信号通过数据采集卡处理后传输给计算机,采用编写的LabVIEW软件采集信号和处理数据。结果表明：仪器可测量的质量范围为m/z 6~320,在m/z 208位置的质量分辨率可达2000,2 h质量稳定性为7.76×10^-5,测量²⁰⁷Pb/²⁰⁶Pb、²⁰⁷Pb/²⁰⁶Pb和²⁰⁷Pb/²⁰⁶Pb同位素比值的精密度分别为0.85%、0.27%和0.55%。该仪器在研究热电离离子源电离行为、同位素比值测定和多原子离子信号监测等方面具有广泛的应用前景。     

Metrological performance investigation of swirl flowmeter affected by vortex inflow

Journal of Mechanical Science and Technology - In fluid transportation industries, long straight transition pipelines upstream of flowmeters are required to eliminate the influence of disturbed...     

Turbulent flow field structure of initially asymmetric jets

The near field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemometry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. Three pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the pipe exit, secondary flow through the bend and mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameter-long straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases.     

Effect of asymmetric actuator and detector position on Coriolis flowmeter and measured phase shift

Coriolis flowmeters (CFM) are forced to vibrate by a periodic excitation usually applied midpipe through an electromagnetic actuator. From hands-on experience with industrial CFMs it appears, that the electromagnetic actuator has to be located as symmetric as possible. For CFM design and trouble-shooting it is of relevance to know how and if imperfections, related to the excitation location, influence the dynamic behavior of the vibrating fluid-conveying pipes employed in CFMs. A simple model of an imperfectly excited, simply supported, straight, single pipe CFM is investigated using a multiple time scaling perturbation analysis. The result is a simple analytical expression for the approximated phase shift, which offers a direct insight into how the location of the actuator influences the phase shift. It appears, that asymmetrical forcing combined with fluctuating pipe damping could be a factor contributing to lack of zero shift stability observed with some industrial CFMs. Tests of the approximated solution against results obtained by pure numerical analysis using Galerkin expansion show very good agreement. The effect of asymmetric detector positions is also investigated. Any asymmetry in the detectors position, e.g. due to manufacturing variations or improper handling of the CFM, induces a phase shift that leads to changes of the meter’s sensitivity, and could therefore result into erroneous measurements of the mass flow. This phase shift depends on the mass flow and does not contribute to a lacking zero-point stability. The validity of the hypotheses, which are assumed to be basically similar for more complicated geometries, e.g. bended and/or dual pipe CFMs, with or without multiple actuators, is suggested to be tested using laboratory experiments with purpose built non-ideal CFMs.     

Design conditions for optimal dual bluff body vortex flowmeters

Examination of the performance of a large number of dual bluff body combinations leads to the conclusion that optimum repeatability of vortex shedding may be obtained with combinations satisfying certain basic conditions. One possible condition is the coincidence of the positions of maximum vortex strength for the individual bluff bodies which make up the combination. The aim of this paper is to describe the results of a test of the above principle using rectangular bluff bodies. The first stage is to find the mathematical relationship between the position of maximum strength and the depth of a single rectangular bluff body. The next stage is to use this relationship to find which combinations satisfy the above coincidence condition. These ‘optimal’ combinations were then tested against a number of ‘non-optimal’ combinations as controls. The overall conclusion is that the above condition is just one of five conditions underlying the design of optimum dual bluff body vortex flowmeters.     

Flow disturbance compensation calculated with flow simulations for ultrasonic clamp-on flowmeters with optimized path arrangement

Ultrasonic clamp-on flowmeters (USCF) are popular among measurement technologies due to the versatility of applications, increasing accuracy, and easy, non-intrusive mounting, with the sensors being mounted directly on the external surface of the pipe. In industrial applications, installation space is usually restricted and therefore, flowmeters must be mounted often directly downstream of flow disturbances (FD). A major issue of USCF is the long inlet run needed downstream of FD to achieve a measurement within the specified accuracy. A configuration of two V-paths is proposed, axially rotated 90° relative to each other, that compensates for the flow error introduced due to disturbed flow conditions, independent of the rotational position of the flowmeter. Flow disturbance compensation (FlowDC) is achieved, i.e., accurate measurements within the specification of 2% flow rate accuracy, when the flowmeter is mounted as close as 2 pipe diameters (D) downstream of a FD. Computational fluid dynamics (CFD) are employed to generate rotationally independent correction factors that compensate for the error introduced from disturbed inlet conditions. An automated simulation method is developed to generate correction factors for 90° bend, out-of-plane bend, expansion, and contraction, at mounting distances from 2D to 100D, several flow rates, and rotational positions 0°, 90°, 180°, 270°. This study would be practically impossible with non-automated simulations or solely with measurements. In-house experiments were performed with an industrial clamp-on device at selected distances from the FD with the aim of verifying the simulation results. An independent field-test is presented that showcases the value of FlowDC in USCF applications. The automated simulations have the capability to simulate further FDs on-demand, with the aim of creating a database for the needs of the respective application in industry.     

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.     

Ultrasonic measurement of tie-bar stress for die-casting machine

In die casting, the real-time measurement of the stress of the tie-bar helps ensure product quality and protect the machine itself. However, the traditional magnetic-attached strain gauge is installed in the mold and product operating area, which hinders the loading and unloading of the mold and the collection of die castings. In this paper, a method for real-time measurement of stress using ultrasonic technology is proposed. The stress variation of the tie-bar is analyzed, and a mathematical model between ultrasonic signal and stress based on acoustoelastic theory is established. Verification experiments show that the proposed method agrees with the strain gauge, and the maximum of the difference square is only 1.5678 (MPa)². Furthermore, single-factor experiments are conducted. A higher ultrasonic frequency produces a better measurement accuracy, and the mean of difference squares at 2.5 and 5 MHz are 2.3234 and 0.6733 (MPa)², respectively. Measurement accuracy is insensitive to probe location and tonnage of the die-casting machine. Moreover, the ultrasonic measurement method can be used to monitor clamping health status and inspect the dynamic pulling force of the tie-bar. This approach has the advantages of high precision, high repeatability, easy installation, and noninterference, which helps guide the production in die casting.     

The mean dynamic yield strength of copper and low carbon steel at elevated temperatures from measurements of the “mushrooming” of flat-ended projectiles

Mean dynamic yield strengths for copper and mild steel are deduced from strain measurements on the “mushroomed” ends of flat-ended projectiles, after impact on a flat, nominally rigid anvil. The kinetic energy at impact is equated with plastic work, to give a mean dynamic yield strength averaged over the deformed specimen. Experiments are carried out over the temperature range 20–700°C, with impact velocities in the region of 600 ft/sec, giving a mean strain rate estimated at 5 × 10³/sec. The yield stress-temperature results obtained show an abrupt increase in dynamic/static mean yield stress ratio at homologous temperatures, T/T_M, of 0·4 for steel and 0·5 for copper. These results agree generally with the findings from other investigations into high-speed blanking⁵ and indentation.⁷

Existing theories for the mushrooming of flat-ended projectiles^{1, 3} do not predict the profiles actually obtained in the present experiments.