Arrays of Rotating Permanent Magnet Dipoles for Stirring and Pumping of Liquid Metals

AbstractMultiple configurations of synchronously rotating permanent magnet cylinders magnetized across the axes are proposed for liquid metal stirring for homogenization as well as for pumping. Universal analytical model is used for an initial parameter analysis. Then experimental setups were built to perform physical modelling of the industrial applications, e.g. large-scale metallurgical furnaces. Velocity distribution in the liquid metal was measured using different methods: the Ultrasound Doppler anemometry and the potential difference probes. The study shows that the cylindrical permanent magnet setups can achieve up to 10 times higher energy efficiency compared to AC inductors and hav…

HOW TO MAKE LIQUID METAL TRANSPARENT? A NEUTRON RADIOGRAPHY METHOD FOR SCALED-DOWN METALLURGICAL EQUIPMENT

MHD sistēmu ar rotējošiem magnētiskiem dipoliem radīto hidrodinamisko plūsmu izpēte

Promocijas darbā eksperimentāli, teorētiski un skaitliski ir pētīta jauna, iepriekš neapskatīta koncepcija un tās radītās šķidrā metāla plūsmas - magnētisku dipolu sistēmas, kas praktiski realizētas, izmantojot cilindriskus pastāvīgos magnētus, kas magnetizēti perpendikulāri to asīm. Izveidots analītisks modelis sistēmas radīto plūsmu parametru kārtas lielumu novērtēšanai, un realizētas vairāk nekā 16 eksperimentālas iekārtas, kur pētīta dažādu koncepciju radītās šķidrā metāla plūsmas. Parādīts, ka, salīdzinot ar klasikām multipola sistēmām, dipoli ir ievērojami efektīvāki pie lieliem nemagnētiskajiem attālumiem, kas ir nepieciešams plašam industriālam pielietojumu spektram. Parādīts, ka ma…

Permanent magnet dipole stirrer for aluminium furnaces

Use of permanent magnet systems for metallurgical applications have been proposed before. We have continued development of such systems by investigation use of single magnetic dipole which is realized as permanent magnet cylinder. Magnet is magnetized orthogonal to its axis and has been mounted to the side of the liquid metal reservoir. System first was modelled using small scale experiment with galinstan melt. Velocity distributions and flow patterns in reservoir using Ultrasound Doppler Anemometer were acquired and will be presented here. Additionally, numerical model using Comsol and Cenos modelling software were developed alongside analytical, non-dimensional estimation calculations. Ex…

Magnētisku dipolu rotācijas inducēta šķidra metāla kustības eksperimentāla izpēte

Darba mērķis ir eksperimentāli izpētīt inducēto šķidrā metāla kustību no rotējošiem cilindriskiem magnētiem, kuru magnetizācija vērta ortogonāli asij. Darbā tiek izpētīta pasaulē vel nekur nerealizēta magnētiskā sistēma, ar mērķi noskaidrot vai šādus magnētus var lietot efektīvai šķidro metālu maisīšanai. Tika izveidota eksperimentā ierīce, kas ļāva nomērīt inducētās šķidrā metālā kustības ātrumu atkarībā no magnētu rotācijas frekvences un attāluma starp magnētiem un šķidrā metāla rezervuāru. Tika iegūti interesanti rezultāti par magnētiskās sistēmas piesātinājumu atkarībā no frekvences un attāluma. Tika apstiprināta hipotēze, ka šādus magnētus var lietot kā ļoti efektīvus šķidrā metāla mai…

Direct chill casting of aluminium alloys under electromagnetic interaction by permanent magnet assembly

Direct chill casting is one of the methods used in industry to obtain good microstructure and properties of aluminium alloys. Nevertheless, for some alloys grain structure is not optimal. In this study, we offer the use of electromagnetic interaction to modify melt convection near the solidification interface. Solidification under various electromagnetic interactions has been widely studied, but usually at low solidification velocity and high thermal gradient. This type of interaction may succeed fragmentation of dendrite arms and transport of solidification nuclei thus leading to improved material structure and properties. Realization of experimental small-scale crystallizer and electromag…

Neutron Radiography Visualization of Solid Particles in Stirring Liquid Metal

Abstract This paper presents the analysis of the first dynamic neutron radiography experiment that visualized motion of solid particles in liquid metal, which was stirred by a system of four counter-rotating magnets. The paper also contains the quantitative results derived from neutron images: the distribution of particle concentration, number of admixed particles and velocities as functions of the magnet rotation speed.

Nanoparticle dispersion in liquid metals by electromagnetically induced acoustic cavitation

Abstract Aim of this study is to investigate experimentally the effect of magnetically induced cavitation applied for the purpose of nanoparticle dispersion in liquid metals. The oscillating magnetic force due to the azimuthal induction currents and the axial magnetic field excites power ultrasound in the sample. If the fields are sufficiently high then it is possible to achieve the acoustic cavitation threshold in liquid metals. Cavitation bubble collapses are known to create microscale jets with a potential to break nanoparticle agglomerates and disperse them. The samples are solidified under the contactless ultrasonic treatment and later analyzed by electron microscopy and energy-dispers…

Permanent magnet bottom-stirred swirling flow in coaxial shallow cylindrical containers

Here, an original rotating permanent magnet (RPM) system placed coaxially with the liquid metal container is studied as an effective means of generating flow in shallow cylinders for potential application in aluminum metallurgy (e.g., for ladle stirring and metal dosing). The studied RPM system generates volume force with strong axial variation and force maximum near the radial midpoint. The numerical and experimental data show that, in the shallow cylinder case, the azimuthal velocity follows the force radial distribution. The resulting velocity maximum occurs near the radial midpoint, unlike in the traditional rotating magnetic field (RMF) stirrer systems, where the velocity maximum occur…

Permanent magnet centrifugal pump for liquid aluminium stirring

In liquid aluminium processing, it is important to ensure continuous mixing of the molten metal to ensure temperature and composition homogeneity, and to improve degassing of the metal. Aluminium and its alloys are often processed in special degassing chambers after preparation in order to avoid segregation and to improve material structure, and to avoid gas pores. This extra step increases material costs and may cause material contamination. In this article, we present the idea to use centrifugal permanent magnet stirrer to induce liquid aluminium motion through thick furnace wall by creating high-speed local liquid metal jet. Analytical estimation, numerical modelling and experimental tes…