Numerical studies on the motion of particles in current-carrying liquid metals and its application to LiMCA systems

by Mei Li

Institution: McGill University
Department: Department of Mining and Metallurgical Engineering.
Degree: PhD
Year: 1999
Keywords: Engineering, Metallurgy.
Record ID: 1699655
Full text PDF: http://digitool.library.mcgill.ca/thesisfile37740.pdf


A numerical model is developed concerning the motion of particles in current-carrying liquid metals in a cylindrical coordinate system. The fluid flow is obtained by solving Navier-Stokes equations, and particle trajectories by equations for the motion of particles which incorporate the drag, added mass, history, fluid acceleration and electromagnetic force, with correction factors for particle shape and orientation. Wall effects and the flow conditions in the entrance region are considered. Dimensionless numbers Re, RH, gamma, and k are introduced to represent the fluid velocity, electric current, particle density and particle size, respectively. Electromagnetic force squeezes non-conducting particles away from, while pushes more conductive particles towards the symmetric axis. In a cylindrical pipe or ESZ orifice, particles follow the fluid flow closely in the axial direction. In the radial direction, at low current, non-conductive particles move towards the central axis first and then to the sidewall, while at high current, directly to the wall because of the competition between the fluid acceleration and the electromagnetic force which increases with particle size, electric current, and distance from the central axis. Lighter and larger particles move faster towards the wall. The dominating increase in added mass over electromagnetic force on oblates than on prolates, the smaller drag force and the lower added mass on prolates, with their symmetric axes perpendicular to the transverse axis of the ESZ, move prolates faster towards the wall. In parabolic ESZ orifice, bubbles lead and heavier particles lag behind the fluid flow in the axial direction, and the transient time difference makes particle discrimination realizable. The conditioning effect is attributed to the dramatic increase in fluid velocity near the parabolic orifice wall upon current surge. Designs are proposed for improving the conditioning effect in steel LiMCA, for reducing the background nois