Electromagnetic Flow Measurements Research Articles

Optimization of electromagnetic flow measurement system based on a new mesh electrode

Electromagnetic flowmeter(EMF) is a common volumetric flow measurement instrument widely used in industrial flow measurement. With the development of EMF in the direction of high precision and intelligence, it is increasingly urgent to further improve the accuracy of EMF measurement. The key to reducing measurement error and eliminating the impact of interference noise is optimizing the electromagnetic flow sensor structure. Aiming at the existing EMF electrode optimization deficiencies, a new mesh structure electrode is firstly proposed in this paper. Then, a theoretical study on the distribution of virtual current density based on this mesh structure electrode is carried out, different structure electrodes are verified and analyzed through COMSOL finite element simulation, and the optimal structure design parameters of the new mesh electrode are obtained. Finally, an experimental platform is built, and a comparative experiment is conducted on the electromagnetic flow measurement system composed of the new mesh structure electrodes. The experimental results show that the maximum relative error of the optimized electromagnetic flow measurement system (OEMFS) is reduced by 0.47% compared with the ordinary EMF in the non-axisymmetric flow test. In the low-flow velocity test, the maximum relative error of the OEMFS is reduced by 7.46% compared with the ordinary EMF. In the strong interference test, the steady-state fluctuation of the amplitude of the OEMFS is reduced by 5.01% compared with the ordinary EMF. The OEMFS has better anti-interference, and the relative error of the system is less affected by the change in flow rate.

Experimental investigation of liquid metal droplet flow affected by a time-dependent magnetic field

Abstract The present study investigates experimentally the effects of a time-dependent and spatially inhomogeneous magnetic field on liquid metal droplet flow down an inclined substrate. The flow is solely excited by the electromagnetic interactions between the electrically conducting melt and the applied magnetic field. The metal droplet consists of the eutectic alloy GaInSn which is liquid at room temperature. The magnetic field is generated in the gap between two metallic disks that are equipped with a special geometric arrangement of permanent magnets and put into a measured rotation. During the experiments, a droplet of a measured volume is positioned on an electrically non-conducting substrate that is slightly inclined against the horizontal direction. Droplet and substrate are placed in between the two rotating magnetic disks. In our experiments, we record the electromagnetically excited flow of the droplet downwards onto the substrate using a high-speed camera system. Applying standard techniques of digital image processing, we measure both the displacement position and velocity of the droplet as a function of time. We observe that, depending on the rotation rate of the disks and angle of inclination, the magnetic field eventually triggers this spreading process. In more detail, by evaluating the recorded data, we find that the magnetic field excites capillary waves at the free surface of the droplet. These surface waves contribute to a redistribution of volume towards the contact line formed at the downward-facing end tip of the droplet. This mode of transport steepens the contact angle, allowing the droplet to move. Besides the fundamental aspect of this work, the present study may contribute to the electromagnetic control of both the production of metallic microfibers and metallurgic coating processes as well as to the non-contact electromagnetic flow measurement technique of Lorentz force velocimetry applied to liquid metal free-surface flows.

Research on Electromagnetic Flowmeter Based on Double-frequency Trapezoidal Wave Excitation

Electromagnetic Flowmeter is widely used in industrial production and life, because it is characterized by high precision and little environmental interference in electromagnetic flow measurement. However, the commonly used low frequency rectangular wave excitation greatly reduces the measurement accuracy and measurement range of electromagnetic flowmeter due to in-phase interference, differential interference and other factors. Double-frequency trapezoidal wave excitation has the advantages of both excellent zero-point stability of low frequency excitation and strong ability to suppress the noise of slurry fluid and fast response speed of high frequency excitation. In this paper, a double-frequency trapezoidal wave excitation method for electromagnetic flow measurement is proposed. Then the experimental platform is established to verify the measurement accuracy and measurement range. According to the comparison with the instant flow of the standard meter, the measurement accuracy of double-frequency trapezoidal wave excitation is significantly higher than that of low frequency rectangular wave excitation, and in phase interference and differential interference are significantly reduced.

Study on a New Electromagnetic Flow Measurement Technology Based on Differential Correlation Detection.

Under the conditions of low flow rate and strong noise, the current electromagnetic flowmeter (EMF) cannot satisfy the requirement for measurement or separate the actual flow signal and interference signal accurately. Correlation detection technology can reduce the bandwidth and suppress noise effectively using the periodic transmission of signal and noise randomness. As for the problem that the current anti-interference technology cannot suppress noise effectively, the noise and interference of the electromagnetic flowmeter were analyzed in this paper, and a design of the electromagnetic flowmeter based on differential correlation detection was proposed. Then, in order to verify the feasibility of the electromagnetic flow measurement system based on differential correlation, an experimental platform for the comparison between standard flow and measured flow was established and a verification experiment was carried out under special conditions and with flow calibration measurements. Finally, the data obtained in the experiment were analyzed. The research result showed that an electromagnetic flowmeter based on differential correlation detection satisfies the need for measurement completely. The lower limit of the flow rate of the electromagnetic flowmeter based on the differential correlation principle could reach 0.084 m/s. Under strong external interferences, the electromagnetic flowmeter based on differential correlation had a fluctuation range in output value of only 10 mV. This shows that the electromagnetic flowmeter based on the differential correlation principle has unique advantages in measurements taken under the conditions of strong noise, slurry flow, and low flow rate.

Electrodes Optimization of an Annular Flow Electromagnetic Measurement System for Drilling Engineering

The early monitoring of downhole overflow can be effectively realized by the downhole annular electromagnetic flow detection system. In order to improve the accuracy of the electromagnetic measurement system of downhole annular flow, it is important to optimize the excitation system and electrodes of this system. This research focuses on the optimization of the electrodes for the electromagnetic measurement system of downhole annular flow, whose excitation system has been optimized. First, the basic principle of electromagnetic measurement of downhole annular flow is analyzed. Then, the influence of different positions of the four-point electrodes on the virtual current distributions is analyzed, and the optimum electrode positions and distributions are introduced. On this basis, the influence of shape and size of the large electrode on virtual current density distribution is analyzed. Based on the theoretical study of the influence of electrode on virtual current density distribution, taking hemispherical electrodes and arc electrodes as examples, this paper optimizes hemispherical electrodes and arc electrodes with different shapes and sizes by using finite element simulation method, and proposes three indexes to evaluate the annular virtual current density distributions when the electrodes of different shapes are used. The optimum parameters of shapes and sizes of the hemisphere electrodes and arc electrodes under specific structures of the downhole annular electromagnetic flow measurement system are obtained. This research has great significance for the optimization of electrodes in the downhole annular electromagnetic flow measurement system, and can also be used as reference for the electrode optimization of the traditional electromagnetic flowmeter.

The hemodynamic impact of the bidirectional flow within calf perforators and conductive veins in varicose vein disease

The hemodynamic assessment of the bidirectional flow within calf perforators and in the conductive veins in varicose vein disease is presented. The bidirectional streaming within calf perforators is induced by the changing polarity of the systolic and diastolic pressure gradients arising during calf pump activity between the deep veins and the saphenous system of the lower leg, as documented by simultaneous pressure measurements in the posterior tibial vein and the great saphenous vein. This bidirectional flow makes the deep and superficial veins of the lower leg conjoined vessels. The vector of the bidirectional streaming in varicose vein patients is oriented inward, into the deep veins. The enlarged calf perforators are the consequence of the saphenous reflux; after elimination of saphenous reflux the diameter of calf perforators diminishes significantly. Results of venous pressure, plethysmographic and electromagnetic flow measurements rebut the still prevalent opinion that the outward flow within calf perforators is a reflux. There is an up-and-down flow in the conductive veins during calf pump activity with a prevailing systolic centripetal (orthograde) flow in the popliteal/femoral axis and a diastolic centrifugal (retrograde) flow in the incompetent great saphenous vein. The popliteal vein represents actually the drain pipe of the calf muscle pump. The ambulatory venous pressure gradient arising during the diastolic phase of the calf pump activity resembles the diastolic pressure difference between the aorta and the left ventricle.

Electromagnetic Flow Detection Technology Based on Correlation Theory

When the electromagnetic flowmeter (EMF) is applied to the industrial field, the effective flow signal of the electrode output is easily drowned out by the noise under the condition of strong noise and flow rate lower than 0.2 m/s. However the flow signal drowned out in strong noise cannot be measured accurately by traditional electromagnetic flow detection technology, which cannot separate signal and noise effectively. The correlation technology can be applied to select the reference signal with the same regularity as the target signal to separate the target signal and remove the noise. Firstly, researches on the correlation detection and the basic correlation theory of the electromagnetic flowmeter are carried out. Then, the design of the electromagnetic flow measurement system based on the theoretical research is completed. Finally, in order to verify the performance and accuracy of the designed flow measurement system, a test platform for electromagnetic flow detection is set up, and the verification experiments are implemented. The experiment results show that the electromagnetic flow measurement system based on the correlation theory can not only meet the requirements of traditional flow measurement but also have unique advantages in suppression of strong noise interference, slurry flow measurement, and low flow rate measurement.

Measurement of Annular Flow for Drilling Engineering by Electromagnetic Flowmeter Based on Double-Frequency Excitation

Using downhole annular electromagnetic flow measurement to obtain annular flow in real-time is a foundation of microflow control drilling technology. The existing annular flow electromagnetic measurement method based on low-frequency rectangular excitation is affected by slurry interference and formation fluid invasion, which results in large noise generated on the electrode output signal. These noise causes the instability of the flow measurement system output and lower accuracy. Double-frequency rectangular wave excitation has the advantages of excellent zero-point stability attributed to low-frequency rectangular wave excitation and fast response speed with great ability to suppress slurry interference. First, the double-frequency rectangular wave excitation for annular flow electromagnetic measurement is researched, and its corresponding electromagnetic induction signal process is investigated. In order to verify the feasibility of downhole annular electromagnetic flow measurement, a flow verification platform for comparison of standard and detected parameters is established for simulation experiment, and the ability to suppress slurry interference and response speed of the technology in downhole slurry flow measurement are analyzed. The test results show that the downhole annular electromagnetic flow measurement based on double-frequency rectangular wave excitation can not only satisfy the requirements of regular electromagnetic flow measurement but also suppress the annular slurry interference effectively.

Invited commentary

With 827 consecutive post-carotid endarterectomy completion arteriograms, Dr Wieker and colleagues detected 57 (6.9%) defects requiring immediate surgical revision. One in 14 of their cases required reopening of the artery! Despite their significant incidence of defects requiring immediate revision, the authors' overall results are superb (0.2%, 0.5%, and 0.6% 30-day mortality, stroke, and transient ischemic attack rates, respectively), and immediate revision was not associated with worse outcomes. Should we adopt the authors' recommendation to perform completion arteriography after all carotid endarterectomies? Before adopting routine completion angiography in our practices, we should answer three questions. First, can we standardize criteria for arterial re-exploration? The authors' figures demonstrate egregious findings clearly requiring re-exploration, but what about more subtle findings? Second, are there less invasive, less time-consuming, and equally accurate methods for assessing the adequacy of reconstruction? Continuous-wave Doppler interrogation, duplex ultrasound, prearterial closure angioscopy, and electromagnetic flow measurements have all been reported to be effective in detecting thrombus, flaps, and other defects requiring revision. There are no data consistently demonstrating the superiority of routine completion angiography over these methods. Third, does every patient need the same completion study? Does the “easy” endarterectomy (thin mobile neck, low bifurcation, focal plaque, easily visualized perfect end point) require the same completion study as the difficult endarterectomy? Perhaps we can use one modality, such as continuous-wave Doppler, for the straightforward cases and reserve arteriography or duplex ultrasound for the more difficult cases and for those with less than perfect Doppler findings. Because so many surgeons have reported excellent results (comparable to the authors') without performing routine completion arteriography, I find it hard to accept the authors' recommendation. There are, however, a few essential routines. The first is obsessive attention to detail in the performance of carotid endarterectomy, both in creation of the endarterectomy end point and in optimizing flow across the fresh, thrombogenic endarterectomy surface. This requires excellent exposure with clear visualization of the arterial intima distal to the plaque and occasional use of tacking sutures or plication techniques. In addition, any anatomic feature that results in damped flow or high resistance to flow, such as proximal common carotid lesions or distal internal carotid kinks, must be treated. Similarly, obsessive attention to perioperative and intraoperative medical management (aspirin, statins, appropriate heparin dosing, tight blood pressure control) is a prerequisite for superior outcomes. Finally, as alarmingly demonstrated in this study, even when experienced surgeons employ standardized, state-of-the-art techniques, anatomic outcomes can be poor. For this reason, routine intraoperative completion studies are essential. For the authors, routine completion arteriography has proven safe and effective. However, there are many other options for intraoperative quality control. In the absence of compelling data supporting the superiority of any one technique, each surgeon should continue to use what works best for her or him while carefully monitoring outcomes and exploring every opportunity for improvement. Impact of routine completion angiography on outcome after carotid endarterectomyJournal of Vascular SurgeryVol. 69Issue 3PreviewThe objective of this study was to analyze the impact of completion digital subtraction angiography (cDSA) after carotid endarterectomy (CEA) on technical and early clinical results. Full-Text PDF Open Archive

Numerical Model for the Detection of Single Particle in Two-Phase Lorentz Force Velocimetry

Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique to measure the flow rate of aggressive or high-temperature molten metal, such as steel or aluminum, and to give information about the local flow. In this paper, we present an extension of the LFV to detect solid particles in a conducting liquid metal based on the Lorentz force signals. The results are verified by magnetohydrodynamics volume element method using ANSYS FLUENT and validated by measurements.

Transient process based electromagnetic flow measurement methods and implementation.

The ordinary electromagnetic flowmeter (EMF) utilizes the steady-state period of the excitation current for measuring the flow rate in order to ensure zero stability and measurement accuracy. In this paper, the transient process of EMF is studied to measure the flow rate so as to realize applications requiring ultra-low power consumption, for example, water meters. For this reason, the dynamic excitation current and signal voltage of the transient process are analyzed, and three kinds of transient measurement methods are proposed to determine the relationship between the processing results of the signal voltage and flow rates. They are the voltage-current ratio method, voltage-current differential method, and differential interference compensation method. In order to verify these measurement methods, a DSP (Digital Signal Processor) that is the same processing chip as the current ordinary electromagnetic flow transmitter is selected to design a hardware system of the transmitter, and the excitation current and signal voltage of the transient process are acquired. Analysis of experimental data shows that there is a good linear relationship between the processing results of the signal voltage and flow rates. The software of the electromagnetic flow transmitter based on DSP is developed, and the transient measurement methods are realized in real time so as to perform the water flow calibration experiments and power consumption tests. The experimental results show that the measurement accuracy is 0.5% which is the same as the ordinary EMF. Comparisons of power consumption show that the excitation power consumption of EMF based on the transient measurement principle is 1/1200 of that of the ordinary EMF.

Dynamic measurements in non-uniform flows

The response of gauges registering the flow velocity and pressure in highly non-uniform media (for example, a powder under shock compression or powdered low-density explosive) is simulated. The modeling employs an acoustic approach. Against the average level of the signal, the fluctuations generated by the heterogeneity of the medium are observed which may distort the results completely. For reliable measurements, gauges larger than the characteristic scale of the medium non-uniformity are required. Under this condition, electromagnetic flow measurements and the velocity interferometer system for any reflector (VISAR) produce quite similar flow velocity profiles with small level of noise.

Electromagnetic interaction between a rising spherical particle in a conducting liquid and a localized magnetic field

Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique for electrically conductive liquids. It is based on measuring the flow-induced force acting on an external permanent magnet. Motivated by extending LFV to liquid metal two-phase flow measurement, in a first test we consider the free rising of a non-conductive spherical particle in a thin tube of liquid metal (GaInSn) initially at rest. Here the measured force is due to the displacement flow induced by the rising particle. In this paper, numerical results are presented for three different analytical solutions of flows around a moving sphere under a localized magnetic field. This simplification is made since the hydrodynamic flow is difficult to measure or to compute. The Lorentz forces are compared to experiments. The aim of the present work is to check if our simple numerical model can provide Lorentz forces comparable to the experiments. The results show that the peak values of the Lorentz force from the analytical velocity fields provide us an upper limit to the measurement results. In the case of viscous flow around a moving sphere we recover the typical time-scale of Lorentz force signals.

Electromagnetic interaction between a permanent magnet and laminar flow of a moving sphere in a conducting liquid

Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique for electrically conducting liquids. It is based on measuring the flow-induced force acting on an externally arranged permanent magnet. Motivated by extending LFV to liquid metal two-phase flow measurement, in a previous test we considered the free rising of non-conductive bubbles/particles in a thin tube of liquid metal (GaInSn) initially at rest. We observed that the Lorentz force signals strongly depend on the size of the bubble/particle and on the position, where it is released. Moreover, the force signals cannot be reproduced in detail, which necessitates a statistical analysis. This is caused by chaotic trajectories due to the rising velocities of about 200 mm/s. Therefore, in this paper, we use an improved setup for controlled particle motions in liquid metal. In this experiment, the particle is attached to a straight fishing line, which suppresses any lateral motion, and is pulled by a linear driver at a controllable velocity (0-200 mm/s). For comparison, we solve the induction problem numerically using Oseen's analytical solution of the flow around a translating sphere that is valid for small but finite Reynolds numbers. This simplification is made since the precise hydrodynamic flow is difficult to measure or to compute. The aim of the present work is to check if our simple numerical model can provide Lorentz forces comparable to the experiments. Although Oseen's solution becomes inaccurate near the sphere for finite Reynolds numbers, it provides a fore-aft asymmetry of the flow and is globally well-behaved. It provides an upper limit to the measurement results. We recover the peak-delay of the Lorentz force signals as well.

Non-contact electromagnetic flow measurement in liquid metal two-phase flow using Lorentz force velocimetry

Non-contact electromagnetic flow measurement in liquid metal two-phase flow using Lorentz force velocimetry

Estimation of combined sewer overflow discharge: a software sensor approach based on local water level measurements.

Combined sewer overflow (CSO) structures are constructed to effectively discharge excess water during heavy rainfall, to protect the urban drainage system from hydraulic overload. Consequently, most CSO structures are not constructed according to basic hydraulic principles for ideal measurement weirs. It can, therefore, be a challenge to quantify the discharges from CSOs. Quantification of CSO discharges are important in relation to the increased environmental awareness of the receiving water bodies. Furthermore, CSO discharge quantification is essential for closing the rainfall-runoff mass-balance in combined sewer catchments. A closed mass-balance is an advantage for calibration of all urban drainage models based on mass-balance principles. This study presents three different software sensor concepts based on local water level sensors, which can be used to estimate CSO discharge volumes from hydraulic complex CSO structures. The three concepts were tested and verified under real practical conditions. All three concepts were accurate when compared to electromagnetic flow measurements.

Competent and incompetent calf perforators in primary varicose veins: a resistant myth

The pathophysiology of calf perforators is presented. Bidirectional flow within calf perforators with a prevailing inward, into deep veins oriented component arises during calf pump activity in varicose vein patients, as evidenced by venous pressure measurements, plethysmographic findings, duplex ultrasonography, and electromagnetic flow measurements. Reflux within calf perforators is an inward, not outward, flow; the opinion that the outward flow within calf perforators is a reflux is at odds with the reality. During calf muscle contraction, the pressure in the posterior tibial vein is higher than in the great saphenous vein; it induces the harmless outward flow within calf perforators, which runs further via great saphenous vein in the physiological direction toward the heart. Deep and superficial veins of the lower leg form conjoined vessels, as documented by nearly equal pressure curves registered simultaneously in the posterior tibial and great saphenous veins both in varicose vein patients and in healthy people. Calf perforators do not entail ambulatory venous hypertension or any other hemodynamic disorder, even if enlarged and incompetent; their ligation is needless. The diameter of calf perforators is influenced by the intensity of saphenous reflux; it enlarges with increasing intensity of saphenous reflux and diminishes after the abolition of reflux.

Experimental study of an electromagnetic flow meter for liquid metals based on torque measurement during pumping process

This paper presents a detailed experimental study on an electromagnetic flow measurement technique to measure the flow rate of liquid metals. The experimental setup consists of a contactless electromagnetic pump with a torque sensor mounted on the pump shaft. The electromagnetic pump is composed of two rotating steel discs having embedded permanent magnets with alternating poles. The rotation of the discs creates a travelling sinusoidal magnetic field and eddy currents within the liquid metal. The metal is contained inside the duct located between the discs of the pump. The interaction of the magnetic field and the induced eddy currents generates an electromagnetic Lorentz force providing the pumping effect. The flow rate is proportional to this force. The torque sensor measures the moment of the discs due to the Lorentz force, which is converted to a flow rate value. We name the method Lorentz torque velocimetry (LTV). The full calibration procedure and experimental investigation of the LTV are described. The method can be used as a non-contact flow rate control technique for liquid metals.

Design of Electromagnetic Probe Having Reduced Base Line Drift for Blood Flow Measurement

ABSTRACTAn improved design for electromagnetic probe for blood flow measurement is presented. The probe produces a magnetic field in the column of blood to induce a voltage as per Faraday's laws. The mechanical and electromagnetic structures are designed to reduce the effect of base line drift and signal variations with time which are very common in electromagnetic flow measurement systems. A signal with very less noise and drift is induced with a sensitivity of more than 80 mV/lpm. The signal has a linear variation with flow rates and need no frequent calibration. Signal variations with time are negligible and had less power signal interferences and noisy spikes.

Preface

The workshop <em> Electromagnetics-Modelling, Simulation, Control and Industrial Applications</em> was held at Weierstrass Institute for Applied Analysis and Stochastics (WIAS), Berlin during May 13-17, 2013. Organizers of this workshop were Dietmar Hömberg (WIAS), Ronald H. W. Hoppe (University of Augsburg/University of Houston), Olaf Klein (WIAS), Jürgen Sprekels (WIAS) and Fredi Tröltzsch (Technical University of Berlin). More than sixty researchers from mathematical, physical, engineering and industrial communities participated in this scientific meeting. This special issue of DCDS-S, which contains eleven research-level articles, is based on the talks presented during the workshop. Electromagnetism plays an important role in many modern high-technological applications. Our workshop brought together prominent worldwide experts from academia and industry to discuss recent achievements and future trends of modelling, computations and analysis in electromagnetics. The contributions to this volume cover the following topics: finite and boundary element discretization methods for the electromagnetic field equations in frequency and time domain, optimal control and model reduction for multi-physics problems involving electromagnetics, mathematical analysis of Maxwell's equations as well as direct and inverse scattering problems. <br> We particularly emphasize that most articles are devoted to mathematically challenging issues in applied sciences and industrial applications. The optimal control and model reduction presented by S. Nicaise et al. arise from electromagnetic flow measurement in the real world. The contribution by G. Beck et al. focuses on a generalized telegrapher's model which describes the propagation of electromagnetic waves in non-homogeneous conductor cables with multi-wires. The numerical analysis of boundary integral formulations carried out by K. Schmidt et al. is motivated by asymptotic models for thin conducting sheets. The integral equation system established by B. Bugert et al. and the analysis and experiments performed by H. Gross et al. make new contributions to direct and inverse electromagnetic scattering from diffraction gratings, respectively. The locating and inversion schemes for detecting unknown configurations proposed by H. Ammari, G. Bao, J. Li and X. Liu et al. could be important and useful in radar and medical imaging, non-destructive testing and geophysical exploration. Last but not least, one can also find important mathematical applications regarding the estimate of the second Maxwell eigenvalues obtained by D. Pauly and the regularity of solutions to Maxwell's system at low frequencies due to P-E. Druet. <br> We hope the presented papers will find a large audience and they may stimulate novel studies on electromagnetism. Finally we would like to express our gratitude to the Research Center MATHEON and the Weierstrass Institute, whose financial support made the workshop possible.