Systematic investigation of pipe flows and installation effects using laser Doppler anemometry—Part II. The effect of disturbed flow profiles on turbine gas meters—a describing empirical model

For systematic investigations of installation effects and for finding efficient ways to minimise these effects, a research project was initiated at the PTB. It covers the design of an automated test facility using a laser Doppler anemometer, the measurement of velocity profiles downstream of several pipe configurations and flow conditioners, as well as the measurement of the change in the gas meter behaviour, namely the shift of the error curve due to the disturbed velocity profiles.

Part I of this paper (presented in this issue) describes the test facility for the investigation of installation effects and shows the relation between pipe configuration and disturbed flow profile for a wide variety of pipe configurations and flow conditioners.

The second part compares the error shift of turbine meters with the characteristic of disturbed flow profiles. For this, three flow field parameters are used to quantify the disturbances of the velocity profiles such as the swirl intensity, flatness and asymmetry of the profile. Considering this, an empirical model is presented to explain the error shift of a turbine meter as a function of these three flow field parameters. The model will be verified for three types of turbine meters and the results will be discussed.     

Reproduction of air velocity in the entrance region of the test pipe in a wind tunnel

The airflow development in the pipe, in the entrance region of the wind tunnel located in the Lithuanian Energy Institute, the laboratory of Heat Equipment Research and Testing is investigated to analyze the conditions for the reproduction of air velocity values. The analysis is performed to reveal undeveloped flow conditions where the calibration of the devices is usually made, the entrance region of the pipes, or free stream from the nozzles. In this study, different flow regimes have been investigated using different air velocity measurement methods. Experimental and numerical results clearly show the features of the developing flow. They both demonstrate the stable core of the velocity profile up to 5 D in the pipe and ≤1 D from the entrance into the free stream in the testing chamber. Ultrasonic anemometer (UA) installed in the aerodynamic test facility shows reliable and highly comparable results with another non-intrusive device – laser Doppler velocimeter (LDA) in a range of velocities from 0.05 m/s up to 30 m/s. UA integrated into the wind tunnel is not found to be used for metrological issues for air velocity. Due to the fast response, they both enabled to analyze fluctuations in the flow. Local vortices identified in the flow have influenced the low-frequency fluctuations and the scatter of measurement results. Moreover, high-frequency fluctuations found in the flow originated from the flow turbulence and might be due to the electronic or acoustic noise. The stabilization of the entrance region in the pipe influences the mean value of air velocity, the transversal distribution of velocity and the development of axial velocity in different test sections of the pipe in a wind tunnel. Along with the recirculation zones in cavities of ultrasonic transducers, these factors are essential that make an impact on the reproduction of air velocity value.     

Velocity and turbulence measurements downstream of flow conditioners

The flow downstream of three conditioners, a tube bundle and two perforated plates, is investigated experimentally by means of particle image velocimetry and hot wire anemometry for Reynolds numbers of the order 10⁵. The conditioners are exposed to the flow disturbed by two different installations: a 90° single bend and a 2×90° out-of-plane double bend. Velocity profiles, turbulent fluctuations and Reynolds‘ stress are measured. The jets issuing from the holes and tubes of the conditioners are visualised in the near field which extends up to approximately four pipe diameters downstream of the conditioners. The disturbance imposed on the flow by the conditioners disappears at this position, while the decay of the disturbance caused by the installations takes place in the far field. The decay rate in the far field depends on the specific installation. It is found that this decay is more rapid for the double bend. While the velocity profiles match the profile for fully developed flow approximately at a position of 25 diameters downstream of the conditioners, the turbulent equilibrium state is not even reached at 50 diameters. The results also show that the perforated plates have a higher efficiency than the tube bundle in conditioning the disturbed flow.     

Improving basic relationships of pipe hydraulics

This communication presents the approaches set up for processing spinner flowmeter well logs in vertical wells with a single fluid phase, which is the most widely used in assessing wells productivity. These focus on improving the pipe hydraulics relationships so that the different fluid inputs throughout the well can be quantified. Since vertical flow inside wells varies with depth between laminar flows (very low Reynolds number, i.e. Re < 10³) and turbulent (Re > 4·10³) the aim has been to reduce the uncertainty in the transition interval. Starting from bibliographical data and/or well-known formulas for laminar and for turbulent flow, several continuous relationships have been developed for any regime: 1) an expression for the radial distribution of velocity inside the pipeline (velocity profile) was developed. 2) A relationship between the average velocity and the velocity at the axis (velocity factor) was created. 3) A third equation was generated to obtain the friction factor in smooth pipes (and starting from this, a new explicit equation for rough pipes). The purpose has been to have a set of empirical expressions of easy and continuous application for any regime, as an alternative to the use of computer simulations.     

On the detection of a low-dimensional attractor in disperse two-component (oil-water) flow in a vertical pipe

The flow of multiphase and multicomponent mixtures in pipes is one of the greatest unsolved problems of modern process engineering. The complexity of the behaviour has meant that all but the simplest phenomena have remained unexplored, both experimentally and theoretically. The droplet flow regime in an oil-water flow in a vertical pipe is investigated by using impedance and ultrasonic techniques. The data are analysed with the Grassberger-Procaccia algorithm. The dimension of the attractor governing the flow is found to be the same (D ≈ 5) within experimental error for both methods. Limitations to the technique are described and the concept of a flow regime map derived in terms of attractor dimension (fractal or Hausdorf-Besicovich) contours is presented.     

Upstream swirl-induction for reduction of erosion damage from slurries in pipeline bends

Industries which transport slurries and other particle-laden liquids in pipes expend the equivalent of millions of pounds every year to repair erosion damage caused by solid particle impingement. It is against this background that the perceived relationship between pipeline erosion and imposed swirling flow fields in pipe bends is important. Definitions of flow fields and particle dispersions which minimise erosive wear are sought to facilitate the development of new designs and geometries for slurry handling equipment. Such an approach is pertinent to industries handling valuable or hazardous material in the face of increasing safety, efficiency and economic requirements. Robust erosive wear models must be developed to explore the advantages of swirl flow and subsequent particle dispersion.

Collaboration between the universities of Nottingham and Southampton is aimed at the reduction of wear at critical locations in slurry handling pipelines by applying swirl-inducing pipes upstream of pipe bends. This paper details the improved particle distributions, particle impingement conditions and lower flowrates resulting from such swirl flow. These factors are discussed in terms of current erosion models and the predicted reduction in wear rates. Parallel visualisation studies using simulant particle-laden liquids augment computational modelling of the flow patterns.     

圆柱主管圆锥支管Y形三通管展开图CAD

Y形三通管接头在管道系统中是最常用的连接部件之一.将图解法和计算法相结合,用计算机进行数据计算、绘图,以代替图解法的手工作图,从而快速精确地展开由一个圆柱管和两个圆锥管组成的任意夹角的Y形三通管接头.用VC 6.0编程生成专用软件,根据用户输入的Y形三通管参数,完成计算和图形显示,同时将计算数据转换成DXF文件,供AutoCAD直接调用.     

Comparison of velocity and turbulence profiles downstream of perforated plate flow conditioners

This paper presents the results obtained when placing different designs of perforated plate flow conditioner downstream of two common flow-disturbing installations in turn: a single 90° bend and a twisted S bend. The results comprise a series of LDV measurements of velocity and r.m.s. fluctuation velocity profiles made in two perpendicular planes at locations between 3 and 41 pipe diameters (D) downstream of the conditioners. The flow conditioners were placed at 4D downstream of the flow-disturbing installations. Measurements were also made without the inclusion of a flow conditioner for comparison. Several designs of flow conditioner give profiles within 5% of a fully developed profile 11D downstream of the conditioner; so significant reductions in lengths of meter runs should be possible. The Spearman (NEL) design performs at least as well as other contemporary designs and is available for inclusion in the relevant standards. These measurements were carried out in a water pipeline.     

An approach for transition correlation of laminar pulsatile pipe flows via frictional field characteristics

Transition of laminar pulsatile pipe flow into turbulence is one of the current research topics in flow dynamics. Despite the existence of a considerable number of theoretical and experimental studies, the physical mechanism of transition is not well defined. Furthermore, there is almost no information on the start and the end of the transition in terms of pulsatile flow parameters.

In this paper, an approach which consists of attempts to correlate the governing flow parameters is presented to reveal the transition process with particular emphasis on the frictional field. The experimental data collected in slightly compressible, Newtonian, one-dimensional laminar pulsatile pipe flow without a flow reversal were compiled for this purpose. The common oscillation parameters, dimensionless frequency parameter and velocity amplitude ratio A₁ were the main variables of the experimental study covering the ranges of and 0.05≤A₁≤0.8. The time history of local static pressure gradient and axial velocity field were accumulated and the data were expressed through pulsatile flow, instantaneous λ_u(t) and time-averaged λ_u,ta friction factors using momentum-integral equation. A reference friction factor ratio λ_R, whose definition was based on the concept of steady flow friction was introduced. The start and the end of transition were predicted through the functional relationships of λ_R with time-averaged and oscillating Reynolds numbers, Re_ta and Re_os by means of a trial–error procedure. The proposed correlations and determined approximate critical limits of transition are only valid in the corresponding ranges of 2000≤Re_ta≤60 000, 620≤Re_os≤18 800 and the analysis is open to discussion.     

PIV measurements of the time-averaged flow velocity downstream of flow conditioners in a pipeline

The flow downstream of three different flow conditioners, a tube bundle and two perforated plates, was investigated by measuring the time-averaged, axial velocity component with Particle Image Velocimetry (PIV). The conditioners were exposed to the flow disturbed by a 90° out-of-plane double-bend. The experiments were performed with air flow through a pipeline of 100 mm i.d. and at Reynolds numbers between 100 000 and 200 000. The axial development of the velocity profiles, without and with conditioner, is documented, and the performance of the three devices in conditioning the disturbed flow can be compared. Particular attention is given to the determination of time-averaged velocity values by means of PIV.     

油气润滑系统中环状流流过突扩管时的流动特性

基于Fluent软件分析了油气润滑工况下环状流流过突扩管时的压力和油膜变化特点。结果表明,油气环状流流过突扩管时压力和油膜会发生突变,且突变的位置不会受到入口气速的影响,但是其变化的强度与入口气速的大小呈正比;油气环状流的液膜在管路突扩前分布的部分分布较为均匀,而在管路突扩后的分布受到气速和管径的影响较大,较大的气速和突扩管径会使环状液膜分散的程度增大。     

Hydraulic modelling of control devices in loop equations of water distribution networks

The simulation of hydraulic behaviour of water distribution networks (WDN) needs to develop and implement a mathematical model that is able to consider a wide range of control devices of complex systems. A literature overview is primarily provided for the solution procedures of steady state simulation of nonlinear pipe network hydraulics. Typical elements of pressure regulating valves are conceptually described and differentiated into their functional characteristics to incorporate their hydraulics in the simulation model. They are explored by considering their possible topological positions and operating states. A novel efficient methodology using an unknown head-loss function is initially presented for the hydraulic simulation of network flow problems containing static and/or dynamic closed pipes. Closed pipes can be mainly obtained in the distribution networks either by turning off the isolation valves at a pipe segment or as a result of the operating state of unidirectional control devices depending on the pressure distribution in the pipe network. Thereupon, this approach is extended to integrate the control elements of pipe networks such as check valves, pressure reducing (PRV) and safety valves as well as booster/pumping stations. An iterative numerical algorithm is applied to solve the loop equations using the Newton-Raphson method for the linearised energy equation, where Hardy-Cross technique is locally used to correct flow rates of loops containing closed pipes in the iteration procedure. The developed hybrid approach demonstrated robust and very fast converging behaviour for real-world pipe network applications. Moreover, it can consider a variety of combinations of control devices in different network configurations. Several empirical head loss formulas can be additionally used in combination with the commonly known equations such as Hazen-Williams and Colebrook-White head loss formulas. The application of the algorithm will be briefly demonstrated by discussing some simulation results from example and real world large scale WDN.     

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.     

电导式相关流量计应用于油井井下流量测量

本文提出了一种新型的电导相关流量计,其敏感元件采用两个电导传感器,该流量能够应用于高含水油井的油水两相流流量测量,在多相流动实验装置上进行的实验表明,该流量计测量的流速范围宽,线性好,该流量计已经在大庆油田进行现场试验,使用该流量计在井下测量的油水的总流量与地面计量结果对比良好。     

Flow imaging for multi-component flow measurement

For pseudo-homogeneous flows, measurements of density and mean velocity can give the component mass flow rate of a two-component mixture. However, for accurate measurement of non-homogeneous flow rate, the density and velocity distribution across the cross-section of the pipe must be known. The most practical way of obtaining this information is by using the flow imaging technique.

A recently developed capacitance system gives 60 frames per second images of oil/water flow in a 78 mm pipe. The target spatial resolution is one part in 20 by distance (one in 400 by area). The electrical properties of each imaged boundary are functionally related to the imaged value, so the component ratio of a two-component mixture within a boundary can be measured, although individual particles cannot be imaged. Design data shows how the basic system can be part of a complete system for component mass flow measurement.     

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.     

输流管道参数共振的试验研究

利用试验的方法研究两端固定输流管道在脉动内流作用时的参数共振特性,建立了一套输流管道试验系统,可以在定常流、脉动流和支承运动等情况下对悬臂、两端固定和两端铰支等多种边界条件的管道进行振动试验,同时给出了一些重要参数的有效测量方法。在对两端固定管道的试验中,重点观察和分析了第1振型1/2次谐波参数共振,并用试验的方法确定了相应的参数共振区域。将其与理论共振区域进行对比,二者在定性上得到了较好的吻合。     

Simulation and experimental study of the sensor emitting frequency for ultrasonic tomography system in a conducting pipe

Ultrasonic tomography techniques provide flow visualization capability, non-invasively and non-intrusively, to enhance the understanding of complex flow processes. There is limited ultrasonic research in tomography imaging systems in the tomogram analysis of fluid flow in a conducting pipe because of a high acoustic impedance mismatch, which means that very little ultrasonic energy can be transmitted through the interface. The majority of industrial pipelines are constructed from metallic composites. Therefore, the development and improvement of ultrasonic measurement methods to accommodate a stainless steel pipe are proposed in this paper. Experimental and simulation distribution studies of the ultrasonic emitting frequency in acrylic versus stainless steel pipes were studied, measured and analyzed. During the simulation, ultrasonic transducers were placed on the surface of the investigated pipe to inspect the ultrasonic sensing field. The distribution of the sound wave acoustic pressure was simulated based on the physical dimensions and parameters of the actual experimental hardware set-up. We developed ultrasonic acoustic models using the finite element method with COMSOL software, and experiments were carried out to validate the simulation results. Finally, by performing the static phantoms tests, a feasibility study of ultrasonic tomography system was presented to investigate the void fraction of liquid column inside a stainless steel pipe.     

气力输送分支流的流量分配特性试验研究

在气力输送试验台上,以压缩空气为输送介质,以砂石为输送物料,进行了分支流的输送试验.试验结果表明,当两个分支管路的阻力特性相同时,它们各自所分配的物料比较平均,表观气速的影响不明显,只是在输送较小粒径的物料时,流量的分配要相对稳定些.当两个分支管路的阻力特性不同时,管道阻力越大,输送物料粒径越大,表观气速越低,其分配的流量就越少.     

大口径宽波段激光发射通道的正压密封

针对大口径宽波段高能激光发射系统内通道的防尘除湿问题,提出了内通道正压通风密封方法。该方法利用净化后的干燥洁净空气排出原有的空气,并在发射端口形成正压气流阻挡外界空气向内通道扩散,从而达到密封防护的目的。借助计算流体力学软件Fluent对发射系统内通道的正压通风流场进行了数值模拟和分析研究,研究显示洁净气流在发射端口处产生一定的风速和压差,从而形成了内部正压抵挡通道外空气的回流。对于10.6μm的长波激光,根据压力变化估计了通道内的折射率变化在10-7量级,引起的光程差约为1μm。最后,通过实验验证了仿真结果。结果表明:监测面的速度值比仿真结果稍大,但是速度变化基本相同,而且洁净气流在监测面保持有0.64m/s的正压速度,洁净空气的相对湿度从59%降至了29%,基本达到了正压通风系统防尘除湿的密封设计要求。