Simple installation for measurement of two-phase gas–liquid flow by means of conventional single-phase flowmeters

The paper describes a method of measuring the flow rate of the components of a two-phase gas–liquid mixture. The proposed method ensures the separation of two phases using a rather simple modification of pipeline configuration than using separating vessels to achieve this aim. The two components can then be measured using conventional single-phase flowmeters. The errors of the separating and metering installation are about ±(3–4)% in the flow rate range 3:1.     

石化乙烯厂C4201一次机流量改造方案探讨

对茂名石化乙烯厂的乙烯气C4201一次机的流量改造方案进行了探讨。通过考虑各种流量调节方法的特点和C4201一次机的实际工作要求,分析比较了可用于C4201机流量调节的各种方案。针对初步优选的减小气缸内径的改造方案,阐述了在改造中需要考虑的工程问题,以及改造成本和经济效益方面的简单评价。采用的工程设计和研究方法,对压缩机流量调节方案的抉择和一般工程设计方案评价有参考意义。     

Feasibility of using thermal response methods for nonintrusive compressed air flow measurement

Robust, low-cost nonintrusive flow meters are of interest in many industries. In particular, a reliable nonintrusive flow measurement for the diagnosis of air leaks in compressed air systems is desirable. Measurement of the air flow due to leaks in the system ensures an accurate estimation of potential cost and energy savings. This study evaluates a novel method of using thermal responses to nonintrusively measure leakage rates in compressed air lines. The method uses heat and the resulting thermal response to calculate the flow rate inside the compressed air line. Compared to the current methods for flow measurement, this method can simplify flow measurement while decreasing the sensitivity to errors when measuring flow rates. In this study, the methodology of the proposed method is explained along with the potential advantages to the design. Two approaches are evaluated: a dynamic step response and sinusoidal frequency response. Simulated tests evaluate the feasibility of the proposed methods, followed by experiments that validate the simulation results. A clear correlation between the thermal step response and the flow rate indicate viability of the proposed method in simulation. Experimental results yielded similar results, confirming the validity of the proposed method. The results of a field test in an industrial environment demonstrate the capability of the approach to other flow rate measurement techniques.     

Simulation of transient flow in pipeline systems due to load rejection and load acceptance by hydroelectric power plants

In this paper, the implicit method of characteristics (IMOC) is extended to simulate the transient flow caused by load variation of hydroelectric power plants. The IMOC was proposed recently by the authors to remove the limitations of the commonly used conventional method of characteristics (MOC) and subsequently used for the simulation of transient flow caused by valve closure and pump failure. In the IMOC, an element-wise definition is used for all devices that may be used in a pipeline system and the corresponding equations are then assembled to form a system of equations that is solved for the unknown nodal heads and flows at each time step. In this paper, the IMOC is extended for the simulation of transient flow in the pipeline system upstream of a hydroelectric power plant. For this, an element-wise definition of the hydroelectric power plants and simple surge tank is proposed and their governing equations are derived in a matrix form required by the IMOC. Then these equations are assembled along with those of other devices of the pipeline system to construct a system of equations that is solved for the unknown head and flow. To further improve the convergence characteristics of the method, an improved formulation of the turbine is also proposed. In the proposed formulation, one of the turbine characteristic parameters, namely turbine net head, is used in addition to turbine head and discharges, to formulate the behavior of the turbine element. The method is applied to a problem of transient flow caused by load rejection and acceptance and the results are presented and compared with those of the explicit MOC. The results show the ability of the proposed method to accurately predict the variations of head and flow in the cases considered. It is also shown that the improved formulation of the turbine is computationally more efficient than the original formulation while producing the same results.     

Forced oscillation to reduce zero flow error and thermal drift for non-reciprocal operating liquid ultrasonic flow meters

A new method using forced oscillation excitation for transit-time difference (TTD) measurement is proposed to improve the accuracy and stability in ultrasonic flow metering under non-reciprocal operating conditions. Forced oscillation guarantees the frequencies of the received signals in both directions constant and known, thus the TTD can be measured as the phase difference. Choosing the driving frequency slightly off the resonance of the transducers can considerably decrease the long-term drift of the TTD results caused by temperature variations, and minimize the zero flow error. In the simulations and experiments, the proposed method showed good performance in the non-reciprocal metering system, the zero flow error and the thermal drift on the TTD measurement results were reduced.     

计量泵出厂后的渗漏及流量问题分析

针对HJ2-0.835型计量泵出厂后用户反映的板间渗漏及流量不合格问题,分析了产生的原因,提出了对密封件、加工精度、装配、检验等方面的改进建议,使计量泵提高加工质量,严格装配规程,改进检验方法,解决了上述的问题。     

Mass flow rate measurement of gas-liquid two-phase flow using acoustic-optical-Venturi mutisensors

The measurement of multiphase flow parameters is essential for the online monitoring of industrial production and energy metering. In this paper, a multi-sensor experimental measurement device is designed based on NIR, acoustic emission sensors, and throated Venturi. The measurement information is decomposed using modal decomposition, and the characteristic variables of the gas volume fraction are extracted by flow noise decoupling and light attenuation analysis. A new gas volume fraction model is proposed based on Gradient Boosting Decision Tree (GBDT) through feature-level fusion, and the Mean Absolute Percentage Error (MAPE) of the gas volume fraction prediction models is within 4% for the three flow patterns. A new flow rate model is established based on the Homogeneous and Collins models. Laboratory results indicate that the MAPE of the flow rate model is 1.56%, and 98.61% relative deviations are within ±20% error band. The study provides a new method for online measurement of multiphase fluid motion and a theoretical basis for sensing mechanism and measurement of multiphase flow.     

为实现节能降耗亟待推广应用流量测量新技术

为加强能源计量、实现节能降耗，在大管径、大流量的使用场合有必要淘汰高能耗的能源计量仪表，并推广应用流量测量新技术。该文将从理论和实验两方面分析和论证这一问题。并提出新的流量计选型原则。     

Stiffness and damping coefficients for journal bearing using the 3D transient flow calculation

The dynamic coefficients of journal bearing are necessary components in the analysis of linear stability and response of rotating dynamic systems. We propose a new method for the numerical identification of bearing support force coefficients in flexible rotor-bearing systems based on the 3D transient flow calculation. The CFD commercial software FLUENT is mainly used in this simulation, which employs a finite volume method for the discretization of the Navier-Stokes equations. To determine the dynamic coefficients, a new mesh movement approach is presented to update the volume mesh when the journal moves during the 3D transient flow calculation of a journal bearing. Existing dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. Measurements and identification are performed on a test rotor supported on a pair of identical two-lobe fluid film bearings, and the results obtained from the CFD methods agree well with experimental results. The results indicate that the methods proposed in this paper can predict the dynamic coefficients of the journal bearing in a rotor-bearing system effectively, and provide a further tool for stability analysis.     

基于双线性插值控制策略的比例流量阀特性研究

当前液压调速阀通常采用机械式压差补偿器或动态流量器等方式实现输出流量的精确控制,但存在机械结构复杂、通流量小,以及输出流量受负载影响大等不足。提出一种基于双线性插值的流量补偿策略,并将该策略应用到以Valvistor阀为主阀的比例流量阀中,形成具有数字流量补偿功能的比例流量阀,其包括主阀、先导阀、压力传感器和流量补偿器,压力传感器的作用是检测反馈主阀进、出口压力;流量补偿器以主阀进、出口压力和设定流量为输入变量,经双线性插值计算后,流量补偿器输出流量校正控制信号,调节先导阀开口以补偿主阀口压差变化对输出流量的影响,从而实现流量的精确控制。建立该比例流量阀的简化数学模型（不考虑流量补偿器）,研究发现输出流量、先导阀输入电压与主阀压差平方根之间存在着线性关系,基于此特征,设计基于双线性插值算法的流量补偿器,并利用仿真和试验对该流量阀的动、静态特性进行研究;结果表明该流量阀输出流量具有良好的静态控制精度且受主阀压差变化的影响较小;若主阀口压差越大,则主阀芯动态响应会越快;对于由负载压力阶跃变化产生的主阀压差而言,若主阀压差越大,则系统流量抗干扰能力随之减弱。     

The fractal flow conditioner for orifice plate flow meters

The sensitivity of orifice plate flow meters to the quality of the approaching flow continues to be a cause for concern in flow metering. The distortions caused by pipe fittings such as valves, bends, compressors and other devices located upstream of the orifice plate can lead to non-standard velocity profiles and give errors in measurement. The design of orifice plate meters that are independent of the initial flow conditions of the upstream is a major goal in flow metering. Either using a long straight pipe, or a flow conditioner upstream of an orifice plate, usually achieves this goal.The effect of a fractal flow conditioner for both standard and non-standard flow conditions was obtained in experimental work and also using simulations. The measurement of mass flow rate under different conditions and different Reynolds numbers was used to establish a change in discharge coefficient relative to a standard one. The experimental results using the fractal flow conditioner show that the combination of an orifice plate and a fractal flow conditioner is broadly insensitive to upstream disturbances.The simulation results also show that the device can be used as a part of a flow metering package that will considerably reduce installation lengths. Previous work with orifice plates has shown that a combination of flow conditioner and orifice plate was promising. The results of using a combination of the fractal flow conditioner and orifice plate for non-standard flow conditions including swirling flow and asymmetric flow show that this package can preserve the accuracy of metering up to the level required in the Standards.     

Theoretical and experimental investigation for developing a gas-liquid two-phase flow meter

Despite the intricacy, inline metering of two-phase flow has a significant impact in multitudinous applications including fusion reactors, oil, nuclear, and other cryogenic systems. Since measurement of individual flow rate is prominent in various systems, it warrants the establishment of a flow meter system that can monitor the mass flow rates of liquid. In this regard, an approach was taken towards the development of a two-phase flow meter system in the present study. The concept involves two-phase flow through narrow parallel rectangular channels resulting in laminar, stratified flow with a slope at the liquid-vapor interface. The height of the liquid column at specific channel locations is measured for determining the flow rate. However, the geometric configurations of the channels and fluid properties are pivotal in ensuring accurate measurement. Consequently, theoretical and experimental studies are performed to investigate the correspondence between flow rate and change in liquid height. Based on the governing equations, a theoretical model is established using MATLAB®. The model investigated the intricate influence of various flow and fluid properties in the estimation of the mass flow rate. The experimental investigation was done with various conditions under different liquid and vapor volume flow rates for validating the proposed supposition and the theoretical model. Both the theoretical and experimental analyses showed fair correspondence. The proposed system estimated the mass flow rate within a tolerance of ±10% and showed potential towards the development of the cryogenic two-phase flow meter.     

Soft-sensors: Model-based estimation of inflow in horizontal wells using the extended Kalman filter

The growing demand for hydrocarbon production has resulted in improved oilfield management using various control and optimization strategies. These strategies increasingly require downhole equipment to obtain real-time oil and gas production rates with sufficient spatial and temporal resolution. In particular, downhole multiphase metering can improve the production of horizontal wells by allocating the zones of oil, gas and water inflow. However, the existing downhole multiphase meters are expensive, inaccurate or accurate only within a limited operating range and therefore such monitoring is unrealistic.To overcome these problems one can use the so-called multiphase soft-sensors, i.e. estimating flow rates from conventional sensors (e.g. pressure gauges) in combination with a dynamic multiphase flow model. This methodology uses inverse modeling concepts to estimate flow rates that are not measured directly. Based on the analysis of the transient pressure response due to a rapid inflow, a real-time estimator is proposed, which uses a dynamic model of the multiphase wellbore flow and information from conventional pressure sensors. The feasibility of the proposed concept is assessed via simulation-based case studies both for noisy synthetic measurements and for artificial data generated by the OLGA simulator.     

Energy metering system for high quality saturated steam

For accurate measurement of steam flow rate, the dryness fraction has to be included in the flow rate calculation; the dryness fraction is also a parameter that often needs to be monitored for effective process control and for condition monitoring of the plant. It is notoriously difficult, however, to measure dryness fraction easily and accurately. In this paper, an energy metering system which measures the steam quality, mass flow rate and thus the energy of the steam is proposed and tested. The system consists of a separator and condensate flowmeter followed by a steam flowmeter; the output signals of these devices are fed into a microcomputer which contains the characteristics of the devices and formulations for steam properties. Testing of the energy metering system showed that the average differences between the displayed output of the system and the values obtained using a condensate weightank was about 0.22% for the dryness fraction and 1.05% for the saturated steam flow rate.     

基于差压信号的湿气流量测量方法

通过理论分析和室内试验研究差压信号的基本特性及差压法测量原理的局限性。对湿气流过孔板和V锥的差压信号进行分析发现：两相流差压主要由气相流动产生,液相的影响很小;低含液率时液相以薄液膜的形式附着在管壁,对气相流动有“润滑”作用,液膜厚度增大到一定值后,气液界面摩擦压降显著增加,由此导致湿气流过节流元件的差压、压损及压损比随含液率增加先减小后增大;差压波动是一个随机过程,差压方根的标准差等特征参数具有稳定性和重复性都较差的特点,难以适用于工业中的湿气流量测量。以过读关联式为基础的测量方法,误差传递过程会缩小气相流量预测误差,但会放大液相流量预测误差,且含气率越高,放大效果越明显,由此造成液相流量预测误差远大于气相流量。建议对于高含气率的湿气流动,液相流量独立测量,避免与气相流量耦合求解;应用压损比作为特征参数时应关注其非单调特性;不建议将差压方根标准差等重复性差的差压信号特征参数用于流量测量。     

An investigation into factors determining the metering performance of a fuel control unit in an aero engine

Fuel flow rate is the most important and most used control parameter for aero engines and it is assured by a device called the fuel control unit (FCU). To investigate factors that determine the metering performance of the fuel control unit, this research comes into being. This paper establishes mathematical models revealing the effect of these determinants, which are pressure difference across the metering valve and actuating process of the metering valve. Results show that the pressure difference does not keep constant as we thought. It will influence the accuracy of metered fuel of the fuel control unit. Furthermore, factors such as the input current of the servo valve, the pressure of the servo fuel and the moving direction of the metering valve will have impacts on the actuating process of the metering valve, influencing the dynamic response of the fuel control unit. Finally, the analyses are affirmed in a hardware-in-the-loop (HIL) experiment involving a real fuel control unit.     

Numerical investigation of cavitating Herschel Venturi-Tubes applied to liquid flow metering

The objective of the present work is the numerical investigation of the applicability of hydrodynamic cavitating Herschel Venturi-Tubes to liquid flow metering. For this purpose, two- and three-dimensional simulations of cavitating flow in two different nozzle geometries were carried out using commercial CFD code. For several reasons, the Herschel Venturi-Tube proved to be superior to other types of nozzles such as the ISO 9300 with respect to liquid flow metering.     

Simulations of the transient flow generated from a started flat plate

Transient operations are commonly founded in fluid machineries such as the starting, stopping, and variations of rotor speeds, etc. Flow generated from a started flat plate is of fundamental importance. Experiments have been done to observe the flow evolution in current researches. And in order to explore the flow in more detailed scale, some vortex methods with high resolution and other numerical methods were developed to solve various related problems by some researchers. But the promotion of vortex method to engineering application is rare due to its complexity and difficulty in specifying the boundary conditions. In order to build up a method of numerical study for such problems, a simplified model is built up with a flat plate. The development of two-dimensional viscous incompressible flow generated from an impulsively started and uniformly accelerated infinitesimally thin flat plate is simulated numerically. A dynamic mesh(DM) method based on the spring analogue and local remeshing is applied to realize the mesh motion caused by the started plate. Researches show that the mesh quality will decline under large grid shear force during the updating process. To conquer this problem, a region near the plate is separated to guarantee the mesh quality at location of interest which is the innovation of the present paper. All computations at least cover a period during which the plate translates 6 times its length. The simulated instantaneous velocity profiles, flow structures and drag coefficients under several Reynolds numbers (20 Re 126) and accelerations (20 m/s2 a 152 m/s2) are presented and compared with existing results in literatures. Comparisons are found to be satisfactory, confirming the validity of the current proposed method(region separated DM). The proposed DM method is firstly used to study the transient flow generated from a started flat plate and can be used in further study of transient characteristics during transient operations of turbo machineries.     

干式空心电抗器匝间短路故障暂态特性仿真研究

从理论上分析了干式空心电抗器从正常运行状态到匝间短路故障状态下的匝间短路动态过程,建立了暂态电路耦合计算模型,并利用ANSYS Maxwell软件模拟了匝间短路故障的暂态特性,提出了通过安装在电抗器封装上的检测线圈实现对电抗器短路位置引起的磁场突然变化的检测方法。通过实验研究表明,采用本文提出的方法可以在较早的故障期间检测到匝间短路故障。     

Development of a novel rotary flow control valve with an electronic actuator and a pressure compensator valve for a gas turbine engine fuel control system

This paper presents a new rotary proportional flow control valve with Cam-Nozzle configuration. The rotating cam against the fixed nozzle changes the flow area and then can meter the fuel flow. This valve equipped with a pressure compensator plunger type valve to retaining constant pressure difference across the flow control or metering valve. The cam shaft directly coupled to an electronic servomotor type rotary actuator and then it is possible to apply digital control techniques such as pulse width modulation (PWM) in this control system. This new valve configuration is developed for an electro hydro mechanical fuel control system in a gas turbine engine. In addition to aero engine application, this type of flow metering valve can widely be used in industrial hydraulic systems. In this unit, the output flow is proportional to the cam's angular position (or throttle command) and it is not sensitive to pressure fluctuations at nozzle inlet and outlet. The aim of this new design is to modify a manual single adjusted hydro-pneumatic fuel control unit to obtain a new electro-hydraulic fuel control system for a gas turbine engine. The main innovations in the presented fuel metering unit include new design of the rotary valve opening shape (Cam-Nozzle) without metal to metal contact, use of a rotary electronic actuating mechanism and also direct coupling between the actuator and the rotating cam. The increased fuel metering precision in the new flow control valve has improved the ultimate control accuracy of system. A computer simulation software based on the proposed model, is performed to predict the steady state and transient performance and to analyze effect of important design parameters on valve outlet fuel flow and obtain the final design parameters. The validity of the proposed valve configuration is assessed experimentally in the steady state and transient modes of operation. The results show good agreement between simulation and experimental in both modes (max. 4% deviation).