Erzeugung ablauffreier Tragkraftverteilungen beim induktiven Schwebeschmelzen elektrisch leitender Stoffe
Final Report Abstract
A numerical model of a new precision level for 3D simulation of coupled EM field and VOF modeled free surface flow of liquid metal with LES turbulence description has been developed, verified and for the first time applied for calculation of EM levitation. Description of EM levitation with VOF algorithm and LES turbulence model, instead of k-ω SST and k-ε models, allows to • capture experimentally observed free surface oscillations at a fully developed flow regime, while two-parameter turbulence models predict steady shape both in 2D and 3D formulation; • obtain better agreement with experiment for the time-averaged droplet shape; • reach greater time-averaged flow velocities, while two-parameter turbulence models overestimate turbulent viscosity that slows down the flow; • obtain better match for the turbulent flow properties with a single-phase simulations in a fixed time-averaged shape of the droplet; • determine precisely values of critical parameters for which the leakage of the levitated melt is initiated. Accurate description of multi-physical processes makes it possible to use the developed model with LES turbulence description to design novel levitation melting furnaces. For numerical simulation of the levitated liquid metal flow and free surface dynamics in horizontal and orthogonal twofrequency ω1, ω2 EM fields it is possible to take into account only the steady part of the Lorentz force, if frequencies 2ω1, 2ω2, (ω1+ω2) un (ω1-ω2) are much higher than the Rayleigh frequency of the melt. The total steady Lorentz force induced by EM fields of two frequencies is the sum of the steady parts obtained separately in the first and in the second EM field. On the ground of numerical results a scaled-up experimental setup for the levitation melting of aluminum samples with increased mass (m = 500 g) has been designed and manufactured. Successful levitation melting experiments have been performed using aluminum samples with m = (100, 150, 200, 250, 300) g, therefore, the limitation of maximum 100 g for levitation melting in conventional inductor with reverse turns has been exceeded with particular method. During levitation melting experiments instability of solid samples has been observed. By means of numerical simulation the mechanism of oscillation amplitude growth has been explained by the small time delay of AC current adjustment if a constant voltage mode is used for generator control. A choice of a constant power mode for generators ensured stability for the fully molten EM levitated samples. By means of horizontal and orthogonal EM fields of different frequencies, compared to the levitation in conventional inductor with reverse windings and zero Lorentz force on the symmetry axis, it is possible to increase the mass of the levitated liquid metal further and to reduce the pronounced dependence on the surface tension.
Publications
- Numerical Modeling of Free Surface Dynamics of Melt in an Alternate Electromagnetic Field: Part I. Implementation and Verification of Model. Metallurgical and Materials Transactions B, Vol. 44 (2013), No. 3, pp. 593-605
S. Spitans, A. Jakovics, E. Baake, B. Nacke
(See online at https://doi.org/10.1007/s11663-013-9809-9) - New technology for large scale electromagnetic levitation melting of metals. Magnetohydrodynamics, Vol. 51 (2015), No. 1, pp. 121-132
S. Spitans, E. Baake, B. Nacke, A. Jakovics
- Numerical simulation of electromagnetic levitation in a cold crucible furnace. Magnetohydrodynamics, Vol. 51 (2015), No. 3, pp. 567{578
S. Spitans, E. Baake, A. Jakovics, H. Franz
- Numerical Modeling of Free Surface Dynamics of Melt in an Alternate Electromagnetic Field. Part II. Conventional electromagnetic levitation. Metallurgical and Materials Transactions B, February 2016, Volume 47, Issue 1, pp 522–536
S. Spitans, E. Baake, B. Nacke, A. Jakovics
(See online at https://doi.org/10.1007/s11663-015-0515-7)
