Electrovortex Flow Research Articles

Solutal buoyancy and electrovortex flow in liquid metal batteries

Liquid metal batteries can be more rapidly charged and discharged when the bottom layer alloy is being efficiently mixed by flows. A numerical investigation into how solutal buoyancy and electrovortex flows interact and influence the alloy composition is presented. Theoretical estimates for the minimal flow magnitude needed to enhance mixing during discharge are derived, and a novel scaling law for the intensity of the solutal convection flow that is observed during charge is proposed.

Research of the electro-vortex flows in the liquid metals at different currents

The electro-vortex flow is a very important phenomenon, taking place in the different processes in metallurgy, such as electrical welding or electrical melting. It appears in the conducting medium under the action of the electromagnetic force due to interaction of the non-uniform electrical current (which passes through this medium) and self-magnetic field. Here we present the study of the electro-vortex flow for the hemispherical geometry. The equations were solved in variables “vorticity – vector potential of velocity”. We considered the problem using Stokes approximation and non-linear case with a finite size of the central electrode, and compared the results obtained by different methods of solving the equations.

Numerical and experimental investigation of electro-vortex flow in a cylindrical container

In a cylindrical container filled with an eutectic GaInSn alloy, an electro-vortex flow (EVF) is generated by the interaction of a non-uniform current with its own magnetic field. In this paper, we investigate the EVF phenomenon numerically and experimentally. Ultrasound Doppler Velocimetry (UDV) is applied to measure the velocity field in a cylindrical vessel. Second, we enhance an old numerical solver by taking into account the effect of Joule heating, and employ it for the numerical simulation of the EVF experiment. Special focus is laid on the role of the magnetic field, which is the combination of the current induced magnetic field and the external geomagnetic field. For getting a higher computational efficiency, the so-called parent-child mesh technique is applied in OpenFOAM when computing the electric potential, the current density and the temperature in the coupled solid-liquid conductor system. The results of the experiment are in good agreement with those of the simulation. This study may help to identify the factors that are essential for the EVF phenomenon, and for quantifying its role in liquid metal batteries.

Energy efficient solutions of DC Electric Arc Furnace Bottom Electrode

Analysis of recent research and publications. The problems of thermal state of billet-type bottom electrode (BE) in liquid bath of DC electric arc furnace (EAF) are associated with limited thermal conductivity of the rod in the absence of available alternative to copper-steel pair. There isn’t enough data on values of convective and Joule components of heat flux, passing through BE, initiated by electrovortex flows (EVF); regarding influence of thermophysical characteristics of transition copper-steel zone and cooling rate of BE copper part on the position of phase transition surface of steel part. Problems are considered, especially related to innovative “flat bath” steelmaking technologies, in which the possibilities of dead time pauses for periodic renewal of the BE body due to “EVF-off” are significantly limited.Purpose. To investigate the effect of EVT on the thermal state of bottom electrode and to develop on this base the energy efficient BE solutions.Methodology. Numerical simulations of BE thermal state and an industrial testing of essentials. Findings & Originality. For the first time, the joint effect of EVF, Joule heat, and characteristics of BE transition zone copper – steel on the position and equilibrium thickness of solid steel part of the BE, which determines the energy efficiency of DC EAF operation, was comprehensively studied.Research implications. Numerical simulations of EVF in DC EAF steelmaking bath and heat transfer with a phase transition through BE were carried out. The heat flux density and local EVF velocity in anode well are 1.8–2 MW/m2 and 0.75 m/s, respectively. Equilibrium thickness of solid steel BE part is critically dependent on the width of copper-steel transition zone, should not exceed 20-25 mm. Contribution of Joule component of total thermal load on the BE does not exceed 20%. Intensification of cooling rate above ≥ 20 kW/(m2K) practically doesn’t affect the BE solid steel part thickness.Practical implications. Manufacturing technology of BE with a narrow transition zone by the method of two-stage electro-slag welding of copper on a steel billet, which ensures stable DC EAF operation and increases energy efficiency, has been improved.

Енергоефективні рішення подового електроду дугової сталеплавильної печі постійного струму

Проведено чисельні дослідження електровихрових течій (ЕВТ) в сталеплавильній ванні дугової печі постійного струму і теплопередачі з фазовим переходом через подовий електрод (ПЕ). Щільність теплового потоку в ПЕ і локальна швидкість ЕВТ в анодній ямі становлять 1,8 −2 МВт/м2 і 0,75 м/с, відповідно. Рівноважна товщина твердої сталевої частини ПЕ знаходиться в критичній залежності від ширини мідно-сталевої перехідної зони, яка має не перевищувати 20−25 мм. Вдосконалено технологію виготовлення ПЕ з вузькою перехідною зоною, що забезпечує сталу експлуатацію ПЕ та підвищення енергоефективності печі.

Numerical simulation of mass transfer enhancement in liquid metal batteries by means of electro-vortex flow

Abstract Mass transfer is of paramount importance for an efficient operation of liquid metal batteries. We show for the first time that electrodynamically driven flow can indeed improve mixing of liquid electrodes, and reduces concentration polarisation substantially. Simulating the discharge of a realistic Li | | Bi cell at 1 A/cm2, the corresponding overpotential reduces by up to 62%. Moreover, the formation of intermetallic phases is delayed, which improves capacity usage. Finally, we demonstrate that vertical magnetic fields – which are originating from external sources – change the flow structure entirely, and will homogenise the positive electrode even better.

Comparison of argon injection and other methods of electrovortex flow control in metallurgical furnaces

The article considers the problem of modeling the metal melting in a direct current arc furnace with the bottom electrode. A mathematical model and a technique for conducting coupled modeling of magnetohydro- and thermodynamic flows in such a furnace are presented taking into account electromagnetic forces and convection. Using the developed strategy, simulations were performed and the effectiveness of some approaches to the vortex flow control was evaluated. As a result, it was shown that changing the location, shape, and temperature of the bottom electrode as well as the bottom position can significantly reduce fettle wearing near the electrode, while argon injection does not decrease shear stress and does a negative influence on the fettle.

Influence of joule heat and heat of electric arc on the vortex flow in DC arc furnace

The paper devoted to the numerical simulation of processes in DC electric arc furnaces with the bottom electrode. These furnaces have shown higher efficiency, low heat loss, lower components wear and higher quality of steel production. The biggest disadvantage of such furnaces is a high rate of fettle wear near the bottom electrode that connected with electrovortex flow. Electrovortex flows appearing under electromagnetic forces as a result of non-homogeneous distribution of the current density through the liquid conductor. This effect can be observed in many technological processes: electro slag remelting process (including DC and AC metallurgical furnaces, electrolysis cells and submerged-resistor induction furnaces), arc welding, processes of semiconductor crystals growing, electro vortex engines etc.

Characteristics of convective heat transfer in the melt of multi-electrode arc furnace

The modern direction of improving the technology of steel production in high-power arc furnaces is the intensification of magnetohydrodynamic effects for melt mixing. In this regard, it is relevant to study the characteristics of heat trans-fer in the melt of this furnace, taking into account the interaction of electrovortex and thermogravitational convection. The results were obtained using a three-dimensional mathematical model of magnetohydrodynamic and thermal pro-cesses, constructed using a non-inductive approximation, taking into account the k- turbulence model. As heat-generating sources, the model takes into account the heat flows from electric arcs and Joule heating. Processing of the results was carried out using visualization methods of vortex structures. A furnace design containing three arched and three bottom electrodes and providing the formation of additional electrovortex flows in the melt is proposed. It is shown that under the given simulation conditions and currents in 80 kA electrodes a multivortex flow is formed in the furnace melt as a result of the interaction of electrovortex and thermogravitational convection. Electrovortex convection dominates near the bath axis. Thermogravitational convection, due to uneven heating of the melt, leads to a reduction in the size of the main electrovortex flow and the formation of an additional flow near the side walls of the furnace. Maximum speeds of 2 m/s are fixed in the melt areas under electric arcs. In this case, the speed of the downward flow under the electric arcs decreases, and the speed of the upward flow in the region of the bottom elec-trodes increases. The effect of thermogravitational convection on the azimuthal melt flow is manifested mainly in the region of the bottom electrodes, leading to an increase in the azimuthal velocity and displacement of the vortices to the center of the bath. The verification of the proposed model was carried out by comparing the calculation results with the experimental data obtained in laboratory installations with various electrode arrangements. The results will be used to further improve the energy and design parameters of arc furnaces.

Study of modes of electrovortex flow in a wide range of external magnetic field magnitudes

Study of modes of electrovortex flow in a wide range of external magnetic field magnitudes

Numerical simulation of electrovortex flows in cylindrical fluid layers and liquid metal batteries

Electrovortex flows occur whenever thin electrodes are put in contact with wider liquid metal regions. An investigation shows that in liquid metal batteries, electrovortex flows can become so intense they can compromise the layered structure of the battery and cause a short circuit.

Numerical simulation of the electrovortex flow in the non-inductive approximation under the influence of an external magnetic field

The results of a numerical study of the structure of an electro-vortex flow under an external magnetic field are presented. It was shown that an external magnetic field can lead to both an increase and a decrease in the intensity of the flux. At the same time, it is necessary to control the external magnetic field in direct current arc furnaces very carefully, since the non-optimal external magnetic field leads to the suppression of the flow in the melting bath.

Numerical study of electro-vortex flow in long cylinder with localized current supply

Numerical simulations of the electrovortex flow (EVF) of the GaSnZn alloy in a closed cylindrical volume are performed. The electric current is applied with two localized opposed electrodes on the cylinder side wall. It is shown that in the entire considered range of electric current values from 50 to 1000 A the EVF arises in a cylinder, in a form of the two-toroidal flow. The flow intensity increases with increasing current values and its maximum intensity is 12 cm/s (at 1000 A). Even at the lowest electric current value of 50 A, a non-stationary behavior of EVF is observed. However, the two-toroidal flow pattern is present in all considered regimes. It is shown that with increasing current the velocity pulsations in the near-electrode region have a frequency up to 0.26 Hz.

Stirring flow of liquid metal generating by low-frequency modulated traveling magnetic field in rectangular cell

In the present work the influence of low frequency modulation of a travelling magnetic field (TMF) on a process of generation of electro-vortex flows in electrically conducting media are numerically and experimentally investigated. The measurements are carried out on a low melting temperature GaZnSn alloy by means of Ultrasonic Doppler Velocimetry. For numerical simulation, Comsol Multiphysics software was used. The dependencies of average and pulsating Reynolds numbers on the magnitude of electromagnetic impact and two modes of low frequency modulation are considered. A positive influence of reversed TMF modulations on the stirring process is determined. In particular the formation of a small-scale vortex structure in the main volume of liquid media.

Electrovortex flows generated by electrodes localized on the cylinder side wall

Electrovortex flows generated by electrodes localized on the cylinder side wall

Applicability of different MHD approximations in electrovortex flow simulation

Applicability of different MHD approximations in electrovortex flow simulation

On the applicability of the electrodynamic approximation in the simulation of the electrovortex flow in the presence of an external magnetic field

Experimental and numerical results on the effect of an external axial magnetic field on the structure of the flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. Results show that for high external axial magnetic field it is absolutely necessary to take into account the induced currents generated by the flow. These results can be used in electrometallurgy for a priori estimates of the flow structure in the direct-current-arc furnaces.

Experimental and numerical investigation of the instability of the electrovortex flow in hemispherical container

Experimental and numerical results on the effect of an external vertical magnetic field (MF) on the structure of the flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. The experiments on the velocity measurement were carried out on the eutectic alloy In–Ga–Sn with the unique fiber-optic transducers. The fiber-optic technique for measuring velocity is described. Results on influence of the axial external MF on the flow are presented. The boundary curve separating the one-vortex and two-vortices flow modes depending on the current values through the experimental setup and the external MF was obtained. These results can be used in electrometallurgy for a priori estimates of the flow structure in the direct-current-arc furnaces.

Electromagnetically driven convection suitable for mass transfer enhancement in liquid metal batteries

Liquid metal batteries (LMBs) were recently proposed as cheap large scale energy storage. Such devices are urgently required for balancing highly fluctuating renewable energy sources. During discharge, intermetallic phases tend to form in the cathode of LMBs. These do not only limit the up-scalability, but also the efficiency of the cells. Generating a mild fluid flow in the fully liquid cell will smoothen concentration gradients and minimise the formation of intermetallics. With this application in mind, electro-vortex flow is studied numerically. A recent LMB related experiment is simulated, and it is further discussed how the feeding lines to the cell can be optimised to enhance mass transfer. The Lorentz forces have to overcome the stable thermal stratification in the cathode of the cell; it is shown that thermal effects may reduce electro-vortex flow velocities considerably. Finally, the influence of the Earth magnetic field on the flow is studied.

Influence of a Local Temperature Change of a Metal Melt on Its Electrovortex Motion in a Bounded Volume

The influence of a local change in the temperature of a metal melt in a bounded volume of a dc arc furnace with a bottom electrode on the structure of its convective and electrovortex flows has been modeled numerically with account taken of the crystallization of the metal. The motion of the metal melt was described by magnetic-hydrodynamics equations for a nonisothermal liquid. The strategy of solution of the indicated problem within the framework of standard packages of applied programs has been developed. It has been shown that the local temperature change of the metal melt changes substantially the structure of its convective and electrovortex flows in the immediate vicinity of a point of the furnace with a lower-than-average temperature and exerts a minor influence on the vortex motion of the melt as a whole throughout the furnace′s volume.