Leibniz University Hannover

Three-dimensional simulation of electromagnetic (EM) levitation of molten aluminum (20 g) in a conventional single-frequency inductor with reverse windings, and in a novel two-frequency levitation melting furnace (500 g and 4 kg).

Problem:

Induction melting of metals under complete levitation conditions has two essential advantages over well-known metallurgical induction crucible furnaces: Electromagnetic (EM) levitation in a non-reactive atmosphere prevents contamination of the melt with the crucible material, resulting in a significantly enhanced quality of alloy, and heat losses from the liquid metal are reduced. However, in a conventional, single-frequency levitation inductor, the Lorentz force vanishes on the symmetry axis, leading to molten metal leakage that is mitigated only by surface tension. This limits the maximum practical metal charge to under 100 grams, which is too small for industrial applications.

Solution:

Researchers increased the metal mass using ANSYS Multiphysics solutions to design a two-frequency, levitating induction furnace with horizontal and orthogonal EM fields. The workflow included ANSYS Mechanical for EM calculations in the liquid metal at an instant free surface shape; ANSYS Fluent for determining the turbulent free surface flow of the liquid metal; and ANSYS CFD-Post to retrieve the new, slightly changed free surface shape of the liquid metal and export it back to ANSYS Mechanical for recalculation of the Lorentz force. The result is a novel, two-frequency induction furnace that is capable of levitation melting of up to 500 grams of aluminum. This design has been verified experimentally. Scale-up to 4 kg of aluminum has been achieved in simulation.

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