Numerical Modeling of Free Surface Dynamics of Melt in an Alternate Electromagnetic Field. Part II: Conventional Electro
- PDF / 4,489,707 Bytes
- 15 Pages / 593.972 x 792 pts Page_size
- 92 Downloads / 189 Views
RESEARCH
INDUCTION melting of metals in complete levitation conditions has two main advantages over common ceramic crucible or cold crucible[1] induction furnaces. Electromagnetic (EM) levitation in a non-reactive atmosphere prevents contamination of the melt with the crucible material and results in a significantly enhanced purity of alloy. Moreover, heat losses from the liquid metal are reduced and limited only to radiation and evaporation that permits EM processing at extremely high temperatures. On the other hand, a highly under-cooled state can be achieved in the absence of crystallization centers. The levitation melting was invented in the 1920’s,[2] whereas the application started only thirty years later[3] as the first high-frequency generators became available. Nowadays, EM levitation of a small molten metal droplet (1 to 10 mm in diameter) is a well-established
SERGEJS SPITANS, Ph.D. Researcher, is with the Institute of Electrotechnology, Leibniz University of Hannover, Wilhelm-Busch Str. 4, 30167 Hannover, Germany, and also with the Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia, Zellu Str. 8, Riga 1002, Latvia. Contact e-mail: [email protected] EGBERT BAAKE and BERNARD NACKE, Professors, are with the Institute of Electrotechnology, Leibniz University of Hannover. ANDRIS JAKOVICS, Associate Professor, is with the Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia. Manuscript submitted April 5, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
experimental technique for measurements of thermophysical properties. Lord Rayleigh has determined the relationship between the surface tension and a small-amplitude oscillation frequency of an inviscid freely falling droplet.[4] The formula is valid for microgravity conditions,[5] as well as for terrestrial measurements with viscosity,[6] gravity and magnetic field[7] related corrections. Influence of the oxide layer on the frequency spectrum has also been experimentally observed.[8] Lamb has determined the correlation between molecular viscosity and oscillation damping factor[9] for the laminar flow regime. The density of levitated droplets and thermal expansion can be measured by photographic methods,[10] as well as electrical conductivity can be determined from measurements of the change in electric circuit impedance due to the presence of a sample.[11] However, on-ground measurements of these and many other properties can be disturbed by the turbulence,[12] since the gravity must be compensated by the Lorentz force that cause intensive stirring. Therefore, reliable tools for obtaining detailed knowledge of the flow structures in EM-levitated droplets are highly required. Despite the significance of the flow in levitated droplets, it cannot be measured directly in majority of cases due to the lack of experimental technique. Ultrasound Doppler Velocimetry (UDV)[13] or Vives probe[14] cannot be used for direct velocity measurements in small, highly rea
Data Loading...
