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.     

Mass flowmeter detecting fluctuations in lift generated by vortex shedding

Indirect measurement of mass flow rate has been widely used, combining volumetric flowmeters with the temperature and/or pressure compensation of fluid density. However, this approach has disadvantages, such as a complicated compensating algorithm, and is only applicable to ideal gases, except for highly pressurized and other gases. A flowmeter for direct measurement of mass flow is more suitable for overcoming the disadvantages of indirect measurement. The authors propose one approach to direct measurement using a vortex flowmeter. That is, Karman vortices are generated by a vortex shedder, and fluctuations in the lift and their frequency are detected by stress sensors built into the vortex shedder. The amount of lift is divided by the frequency to yield signals proportional to the mass flow rate. The proposed approach to sensing features simplicity both in principle and in sensor construction. Satisfactory results are obtained from applying this approach to water, air and other gases.     

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.     

智能涡街流量计的设计与实现

涡街流量计众多的优点使其跻身通用流量计之一,但是当流速较低时,会存在测量不稳定的缺点。针对涡街流量传感器的非线性特性,本系统采用16位微处理器M SP430F435为核心,将传感器特性曲线存储在F lash存储器中,实现了对涡街传感器的非线性校正,从而扩大了涡街流量计的使用范围。同时该仪表还具有频率输出、4—20m A电流输出以及R S485通信功能,便于和传统仪表兼容。     

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.     

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。     

基于PIC18F452的流量计的设计与实现

介绍一种以PIC18F452单片机为核心的智能流量计。通过测量来自涡街的信号频率,计算得到流体的瞬时流量和累积量,并进行显示。流量计具有CAN通信接口,多个流量计可以组成CAN通信网络,实现对流量的多点监测。文中详细阐述了流量计的工作原理,给出了硬件原理图及软件流程图。     

Wavelet denoising applied to vortex flowmeters

For the problems of signal extraction from noisy data, wavelet denoising has been proven to be a powerful tool from both an empirical and an asymptotic point of view. In this context of wavelet denoising, we study the specifically modified criteria as flexible forms of thresholding for practical vortex flowmeter signals. Four key factors are discussed. Analysis based on practical signals shows that this method can be used to extend the lower measurement limit of the vortex flowmeters.     

涡街流量计信号估计的自适应陷波方法

本文提出采用自适应陷波方法计算涡街流量计输信号的频率,并给出实验结果。流量计信号为一窄带信号,自适应陷波抑制一个特定的涡街频率,并且几乎不受位于带宽以外频率的影响。此自适应陷波器只需估计一个参数,频率计算非常简单,与以前的频率估计方法相比,它以前的频率估计方法相比,它有许多优点,是一种有效的新方法。     

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.     

Note: anti-strong-disturbance signal processing method of vortex flowmeter with two sensors

Some digital signal processing methods have been used to deal with the output signal of vortex flowmeter for extracting the flow rate frequency from the noisy output of vortex flow rate sensor and achieving the measurement of small flow rate. In applications, however, the power of noise is larger than that of flow rate sometimes. These strong disturbances are caused by pipe vibration mostly. Under this condition the previous digital signal processing methods will be unavailable. Therefore, an anti-strong-disturbance solution is studied for the vortex flowmeter with two sensors in this Note. In this solution, two piezoelectric sensors are installed in the vortex probe. One is called the flow rate sensor for measuring both the flow rate and vibration noise, and the other is called the vibration sensor for detecting the vibration noise and sensing the flow rate signal weakly at the same time. An anti-strong-disturbance signal processing method combining the frequency-domain substation algorithm with the frequency-variance calculation algorithm is proposed to identify the flow rate frequency. When the peak number of amplitude spectrum of the flow rate sensor is different from that of the vibration sensor, the frequency-domain subtraction algorithm will be adopted; when the peak number of amplitude spectrum of the flow rate sensor is the same as that of the vibration sensor, the frequency-variance calculation algorithm will be employed. The whole algorithm is implemented in real time by an ultralow power micro control unit (MCU) to meet requirements of process instrumentation. The experimental results show that this method can obtain the flow rate frequency correctly even if the power of the pipe vibration noise is larger than that of the vortex flow rate signal.     

基于DSP、具有谱分析功能的涡街流量计信号处理系统

本文介绍一种以数字信号处理器（DSP）为核心、具有谱分析功能的涡街流量计信号处理系统。它采用周期图谱分析方法对涡街流量计中传感器的信号进行数字处理,准确计算出信号的频率,测出准确的体积流量,它抗干扰能力强,保证现场测量精度,扩大量程比,现场显示,并适用于不同口径和测量不同流体的一次仪表,它采用了DSP,保证了处理的实时性。     

Response of a dual triangulate bluff body vortex flowmeter to oscillatory flow

In this paper, on an experimental facility, the measurement characteristics of a diameter 50 mm dual triangulate bluff body vortex flowmeter in steady flow and oscillatory flow were investigated. Then, the Hilbert Huang Transformation (HHT) method was used to assess the anti-interference performances and the vortex street stability in oscillatory flow for the dual triangulate bluff body vortex flowmeter and a single bluff body vortex flowmeter. Offline simulation was carried out on the anti-interference performances of the dual triangulate bluff body vortex flowmeter signal noise in oscillatory flow by the method of the EMD-scales filter. The major findings are: (a) in most case, the EMD-scales filter may be as good at de-noising effect for the dual bluff body vortex flowmeter in oscillatory flow than that for the single bluff body vortex flowmeter in oscillatory flow. The vortex street stability in oscillatory flow for the dual bluff body is similar to that for the single bluff body. (b) In some special case, the EMD-scales filter is unable to play a better de-nosing role for the dual bluff body vortex flowmeter in oscillatory flow. The invalid condition of the EMD-scales filter for the dual bluff body vortex flowmeter in oscillatory flow is different to that of the single bluff body vortex flowmeter and it was advanced in this paper. (C) The vortex street stability for the dual bluff body vortex flowmeter is better than that for the single bluff body vortex flowmeter.     

基于ARM单片机的无线涡轮流量计的设计

传统涡轮流量计需要铺设电源线和信号传输电缆,使用起来极不方便。而现有的无线通信方式繁多,特点不一,为了实现计量点分散情况下流量计的远程实时报警、监测流量等功能,对主要无线通信方式进行了简要分析。给出了以ARM单片机为核心处理器,集成无线通信模块的流量计设计方案,并对涡轮流量计的软硬件进行了具体设计。该方案能够实现流量测量、数据存储、流量显示、远程实时报警、远程监控等功能。     

Study of acoustic transducer protrusion and recess effects on ultrasonic flowmeter measurement by numerical simulation

In order to improve the measurement performance of dry calibration on ultrasonic flowmeter, the Computational Fluid Dynamic (CFD) modeling approach of the effect on transducer protrusion and recess are mainly discussed in the paper while its effects on ultrasonic flowmeter accuracy are also presented. Through comparing simulation results to experimental data, the CFD modeling is firstly determined. Then, detail analysis on flow field for two typical transducer installations are obtained based on the CFD method. Besides, the mechanism of both flow effects on measurement accuracy are explained and compared respectively, which indicates that negative velocities generated at protrusion and recess locations are the indispensable factors for negative measurement errors. Finally, comparison results show that smaller measurement error can be achieved with protruding transducers, which is a better arrangement type of transducer for ultrasonic flowmeters.     

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.     

基于DSP的新型超声多普勒流量计设计与实现

文中针对当前工业管道用超声多普勒流量计的性能普遍不高的现状,改进了测量工业管道流量方法,并且采用高速DSP器件TMS320VC5410实现一种新型超声多普勒流量测量系统.实现的新型超声多普勒管道流量测量系统可以动态显示流速和方向、瞬时流量、累积流量、信号强度等测量结果,较高的流速测量动态响应能力以及稳定性,具有较好的推广和应用前景.     

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。     

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.     

差压式涡街质量流量计取压位置的研究

在涡街流量计中，流体通过涡街发生体后会产生压力损失及由旋涡引起的压力波动，根据这一特点，本文提出利用差压检测技术，通过单路差压传感器同时感受由涡街发生体引起的流体双重变化特性，测量流体质量流量的新方法。本文重点对差压检测取压位置进行研究，利用空气和水两种流体介质进行了一系列实验，得到不同取压位置的差压信号与流量关系，确定了能正确测量质量流量的差压取压位置。结果表明，该测量方法结构简单，是测量质量流量的有效方法。