Lorentz Force Flowmeter Research Articles

Using Lorentz force flowmeter to measure the narrow channel flow that mimics lead-bismuth cooled reactors

ABSTRACT LFF (Lorentz Force Flowmeter) as a new non-contact electromagnetic flowmeter, can adapt to high temperature, strong corrosion, and other factors, which is suitable for measuring the flow of lead-bismuth eutectic (LBE) commonly used in the nuclear industry. This article designs a narrow channel with fuel rod gap characteristics and conducts simulation measurement experiments on the laboratory GaInSn loop using the Halbach-type LFF. The experimental results indicate that the accuracy of the Halbach-type LFF in measuring the flow rate of this specially shaped narrow channel can meet industrial requirement, and it is more flexible compared to Faraday flowmeter. This paper explores the way forward for real-time, on-line, accurate measurement of narrow flow in LBE cooled reactors in the nuclear industry by LFF.

Electromagnetic flow rate measurement in molten tin circulating in a closed-loop test system

Flow rate measurement in molten metals at elevated temperatures is still a challenging task in metallurgie application. Due to the opaqueness and chemical aggressiveness of such melts, non-contact and non-invasive electromagnetic methods are of special interest. In order to develop and to test such methods under controllable laboratory conditions, during the last years at TU Ilmenau we have built up and instrumented the test facility TINTELO (tin test loop). TINTELO is a closed loop facility made of stainless steel in which molten tin at a temperature up to 350°C circulates in the horizontal plane. The flow is driven by an electromagnetic pump based on rotating permanent magnets. The rotation frequency of the pump can be fixed at up to 60 Hz providing a mass flow rate of 17.5 kg/s which corresponds to a Reynolds number of Re = 2·105. TINTELO is instrumented with both a Lorentz force flowmeter and a wall potential flowmeter. The Lorentz force flowmeter measures the force which the electrical conducting moving molten tin exerts on a system of permanent magnets arranged outside of the loop. This force is the counter force to the well-known braking Lorentz force that is proportional to the melt flow rate. Moreover, the wall potential flowmeter records the electric potential difference between two electrodes inserted in the conducting wall of the loop. This potential difference, induced by the moving melt when interacting with an externally applied magnetic field, is proportional to melt velocity. In this paper we present the design and the instrumentation of TINTELO, the calibration methods for the used flowmeters and first results of the flow rate test measurements.

Lorentz Force Velocimetry using a bulk HTS magnet system

Design of the Lorentz Force Flow-meter (LFF-meter) for weakly-conducting and slow-flowing fluids, e.g., glass melts, place stringent requirements on the magnetic field generation and force measurements. In the scope of the Research Training Group “Lorentz Force Velocimetry (LFV) and Lorentz Force Eddy Current Testing”, a LFF-meter considers: first - a magnetic field source, where NdFeB permanents magnet system is replaced with a bulk high-temperature superconductors (HTS), which promise higher flux densities (> 1 T) and thus higher output force resolution; second - a high-precision force measurements, where electromagnetic force compensation weighing balance (EMFC) setup is replaced with torsion balance based system (TFMS), which claims an increase of the force resolution up to 1 nN. Furthermore, in order to raise the issue of the limiting total mass (which is always an issue for high-precision force measurements), the bulk HTS and TFMS are merged within the cryostat. This work discusses LFV experiments, calculations and numerical simulations, where a magnetic field is generated by the bulk HTS.

Local Lorentz force flowmeter at a continuous caster model using a new generation multicomponent force and torque sensor

Lorentz force velocimetry is a non-invasive velocity measurement technique for electrical conductive liquids like molten steel. In this technique, the metal flow interacts with a static magnetic field generating eddy currents which, in turn, produce flow-braking Lorentz forces within the fluid. These forces are proportional to the electrical conductivity and to the velocity of the melt. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied static magnetic field which is in our case a permanent magnet. In this paper we will present a new multicomponent sensor for the local Lorentz force flowmeter (L2F2) which is able to measure simultaneously all three components of the force as well as all three components of the torque. Therefore, this new sensor is capable of accessing all three velocity components at the same time in the region near the wall. In order to demonstrate the potential of this new sensor, it is used to identify the 3-dimensional velocity field near the wide face of the mold of a continuous caster model available at the Helmholtz-Zentrum Dresden-Rossendorf. As model melt, the eutectic alloy GaInSn is used.

A Lorentz force flow meter for application at blast furnaces: design and calibration

AbstractA reference Lorentz force flow meter (LFF) has been developed to measure molten steel mass flow at the end of the runner of an experimental blast furnace. It works according to the principles of Lorentz force velocimetry [1] in which a static magnetic field interacts with a liquid metal stream. The magnetic field lines are generated by an arrangement of permanent magnets and penetrate the entire cross‐section of the flow generating eddy currents and a total Lorentz force inside the melt. This force is proportional to the mass flow of the liquid metal and owing Newton's third law, there is a counter force of the same magnitude acting on the magnet system which is connected to a load cell. For accurate flow rate measurements, a “dry and wet calibration” of the LFF needs to be performed [2]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Application of Manning’s Formula for Estimation of Liquid Metal Levels in Electromagnetic Flow Measurements

Lorentz force velocimetry is a new technique in electromagnetic flow measurements based on exposing an electrical conducting metal to a static magnetic field and measuring the force acting on the magnet system. The calibration procedure of a Lorentz force flowmeter used in industrial open-channel flow measurements is difficult because of the fluctuating liquid level in the channel. In this paper, the application of Manning’s formula to estimate the depth of a liquid metal flowing in an open channel is analyzed by using the numerical modeling. Estimations of Manning’s n parameter for aluminum show higher values as compared with water flowing in artificial channels. Saint-Venant equations are solved in order to analyze the wave propagation at the free surface of the liquid. Numerical results show a significant damping of waves at the surface of liquid metals as compared with water. Therefore, the Manning formula can be used to correlate the liquid depth and the flow rate in LFF numerical calibration procedure. These results show that the classical formulas, used exclusively to study the water flow in open channels, can be also applied for the liquid metals. The application of Manning’s formulas requires experimental measurements of the parameter n, which depends on the channel bed roughness and also on the physical properties of the liquid flowing in channel.

Influence of velocity profile on calibration function of Lorentz force flowmeter

A Lorentz force flowmeter is a noncontact electromagnetic flow-measuring device based on exposing a flowing electrically conducting liquid to a magnetic field and measuring the force acting on the magnet system. The measured Lorentz force is proportional to the flow rate via a calibration coefficient which depends on the velocity distribution and magnetic field in liquid. In this paper, the influence of different velocity profiles on the calibration coefficient is investigated by using numerical simulations. The Lorentz forces are computed for laminar flows in closed and open rectangular channels, and the results are compared with the simplified case of a solid conductor moving at a constant velocity. The numerical computations demonstrate that calibration coefficients for solid bodies are always higher than for liquid metals. Moreover, it can be found that for some parameters the solid-body calibration coefficient is almost twice as high as for a liquid metal. These differences are explained by analyzing the patterns of the induced eddy currents and the spatial distributions of the Lorentz force density. The result provides a first step for evaluating the influence of the laminar velocity profiles on the calibration function of a Lorentz force flowmeter.

Spatial and temporal resolution of a local Lorentz force flowmeter

Electromagnetic measurement techniques are very promising for accessing the flow properties of liquid melts. We extend one of the recently developed techniques, Lorentz force velocimetry, to the measurement of spatial flow structures close to the wall of the confining container. The sensor we use is called local Lorentz force flowmeter (L2F2). It comprises a small permanent magnet which is attached to a force measurement system. We demonstrate that it is possible to reconstruct the complex flow in the vicinity of the wall of a confined vessel using the L2F2. Additionally, we show with the help of a solid body experiment that the L2F2 responds to temporal changes in the flow in the order of 1 Hz.

Contact-free measurement of the flow field of a liquid metal inside a closed container

The measurement of flow velocities inside metal melts is particularly challenging. Due to the high temperatures of the melts it is impossible to employ measurement techniques that require either mechanical contact with the melt or are only adaptable to translucent fluids. In the past years a number of electromagnetic techniques have been developed that allows a contact-free measurement of volume flows. One of these techniques is the so-called Lorentz Force Velocimetry (LFV) in which the metal flow is exposed to an external, permanent magnetic field. The interaction between the metal and the magnet not only leads to a force on the fluid, but also on the magnet. The force can be measured and is proportional to the velocity of the melt. Moreover, by using a small permanent magnet it is possible to resolve spatial structures inside the flow. We will demonstrate this using a model experiment that has been investigated with different reference techniques previously. The experimental setup is a cylindrical vessel filled with a eutectic alloy which is liquid at room temperature. The liquid metal can be set into motion by means of a propeller at the top of the liquid. Depending on the direction of rotation of the propeller, the flow inside the vessel takes on different states. Beside the vessel, we place a Lorentz Force Flowmeter (LFF) equipped with a small permanent magnet. By measuring the force on the magnet at different positions and different rotation speeds, we demonstrate that we can qualitatively and quantitatively reconstruct the flow field inside the vessel.

Spatially resolved measurements in a liquid metal flow with Lorentz force velocimetry

Velocity measurements inside metal melt flows are important for many laboratory and industrial applications in metallurgy but remain experimentally challenging. Only few techniques are viable for the measurement of mean flow velocities inside hot and aggressive materials. One of them is the previously studied electromagnetic contact-free Lorentz force velocimetry. However, the desire to resolve velocities spatially has not been satisfied so far. In the work presented here, spatial resolution is reached with a Lorentz force flow meter (LFF) by implementing a permanent magnet whose dimensions are significantly smaller than that of the flow under investigation. It is shown on a straight square duct flow that such a flow meter is capable of distinguishing obstacles in the flow and the resulting modified flow structures. The spatial resolution of the LFF is demonstrated to be at least on the order of 3 cm with a 1 cm magnet cube.

Electromagnetic Drag on a Magnetic Dipole Interacting With a Moving Electrically Conducting Sphere

In this paper, we report an analytical study of the forces and torques acting upon a magnetic dipole interacting with a moving electrically conducting sphere. The work is motivated by the question whether Lorentz force velocimetry [Thess , Phys. Rev. Lett., vol. 96, 2006, 164501]-a noncontact flow measurement technique for liquid metals and electrolytes-can be applied to granular materials as well. We derive explicit expressions for all forces and torques for the case of low magnetic Reynolds number and small particle size. After a discussion of symmetry and reciprocity relations among the forces and torques, we apply the general theory to the particular cases of a translating (nonrotating) and rotating (nontranslating) sphere. The analysis for the purely translating sphere leads to the conclusion that the force is proportional to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> is the radius of the sphere and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</i> is its minimum distance to the magnetic dipole. This result indicates that Lorentz force velocimetry can indeed be applied to granular metallic materials. The analysis for the purely rotating sphere leads to the result that the torque is proportional to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> . This result can be applied to derive a rigorous solution for a rotary Lorentz force flowmeter interacting with a rotating sphere. This solution implies that, contrary to intuitive expectation, a frictionless rotary Lorentz force flowmeter rotates with only 4/5 of the angular velocity of the sphere with which it interacts rather than undergoing synchronous rotation.

Calibration of a Lorentz force flowmeter by using numerical modeling

A Lorentz force flowmeter is a device used for contactless measurements of the flow rate in liquid metals at high temperatures. Application of this device in practice requires a calibration procedure. In this paper, numerical modeling is used to calibrate this flowmeter in different flow conditions. Laminar and turbulent flow effects on the calibration curve are analyzed for liquid aluminum flow in closed and open channels. The flow damping caused by the Lorentz forces is also analyzed for laminar and turbulent flows. Numerical computations including flow are compared to the simplified case of a solid conductor moving at constant rate. The computations performed for laminar flows in open and closed channels, show significant flow effects on the Lorentz forces as comparing to the case of solid body computations. In the case of high Reynolds number turbulent flows in closed and open channels, the results are very close to solid body computations. In conclusion, the flow effects are important for the calibration procedure only for laminar flows. At high Reynolds numbers, the complex numerical models used for computing the calibration curves can be replaced by simple solid body computations.

Numerical calibration of a Lorentz force flowmeter

Numerical simulation of complex-shaped devices for contactless electromagnetic flow measurement in metallurgy is a challenge for computational magnetohydrodynamics. We report a series of numerical simulations which demonstrate for the first time that it is possible to predict the calibration constant of a generic Lorentz force flowmeter (LFF) with an uncertainty close to the requirements of real-life industrial applications. Our simulations involve both magnetostatic computations of a complex-shaped magnet system and magnetohydrodynamic computations of the flow of a liquid metal in a nozzle under the influence of a predominantly transverse magnetic field. In order to assess the role of turbulence, the simulations have been performed both for laminar and for turbulent flows using Reynolds-averaged Navier–Stokes equations in the latter case. In addition to the numerical simulations we have measured the calibration constant of the considered LFF using room-temperature liquid metal instead of liquid aluminum. A comparison between the numerically predicted and the measured values of the calibration constant shows that they differ by only 3.4%. This result suggests that numerical calibration of a LFF may become an economic alternative to expensive full-scale experimental calibration.

Optimization of a Lorentz force flowmeter by using numerical modeling

Optimization of a Lorentz force flowmeter by using numerical modeling

Calibration of the Lorentz force flowmeter

The Lorentz force flowmeter (LFF) is a measuring device utilizing localized static magnetic fields for the non-contact measurement of the flow rate in electrically conducting fluids. In case of highly aggressive or high-temperature conductive fluids, it is difficult to reproduce in a laboratory the conditions typically met in application. Hence, calibration becomes a difficult task. For the LFF used for open channel flow measurement in liquid aluminum, we adapt a robust calibration method. This method utilizes reference device calibration data to calibrate other devices. In a first step, liquid calibration involving the fluid flow is performed in a reference open channel with a given reference LFF device. In a second step, the liquid calibration characteristic is transferred from the reference LFF device to the test LFF device during a dry calibration procedure, in which liquid metal flow is replaced by the motion of solid metal bars through the magnet systems of both reference and test devices. Hence, the liquid calibration is needed once for the reference device only. This combined calibration strategy may also be applied to similar measurement devices.

Lorentz Force Flowmeter for Liquid Aluminum: Laboratory Experiments and Plant Tests

This article aims to demonstrate that molten metal flow at a high temperature can be measured effectively in a contactless manner by using external direct current magnetic fields. The device applied in the present work is termed Lorentz force flowmeter (LFF) and is based on exposing the flow to a magnet system and measuring the drag force acting on it. Two series of measurements are reported. In the first series, we perform a model experiment in the laboratory using the eutectic alloy GaInSn, which is liquid at room temperature. The second series of measurements is devoted to two plant tests on flow measurement of a liquid aluminum alloy. In both tests, the force acting on the magnet system is measured that is equal to the Lorentz force acting on the flow. To generalize our results, we also derive the scaling law that relates the force acting on a localized magnet system to the flow rate of a fluid with arbitrary electrical conductivity. This law shows that LFF, if properly designed, has a wide range of potential applications in ferrous and nonferrous metallurgy.

Lorentz force flowmeter in industrial application

Lorentz force flowmeter in industrial application

Dry calibration of the Lorentz force flowmeter

Dry calibration of the Lorentz force flowmeter

Theory of the Lorentz force flowmeter

A Lorentz force flowmeter is a device for the contactless measurement of flow rates in electrically conducting fluids. It is based on the measurement of a force on a magnet system that acts upon the flow. We formulate the theory of the Lorentz force flowmeter which connects the measured force to the unknown flow rate. We first apply the theory to three specific cases, namely (i) pipe flow exposed to a longitudinal magnetic field, (ii) pipe flow under the influence of a transverse magnetic field and (iii) interaction of a localized distribution of magnetic material with a uniformly moving sheet of metal. These examples provide the key scaling laws of the method and illustrate how the force depends on the shape of the velocity profile and the presence of turbulent fluctuations in the flow. Moreover, we formulate the general kinematic theory which holds for arbitrary distributions of magnetic material or electric currents and for any velocity distribution and which provides a rational framework for the prediction of the sensitivity of Lorentz force flowmeters in laboratory experiments and in industrial practice.