Non-contact electromagnetic flow measurement in liquid metal two-phase flow using Lorentz force velocimetry

Z. Lyu - Ch. Karcher

Institute of Thermodynamics and Fluid Mechanics, Technische Universität Ilmenau, P.O. Box 100565, D-98684 Ilmenau, Germany

Abstract
Lorentz force velocimetry (LFV) is a contactless flow measurement technique for electrically conducting liquids. LFV is based on measuring the flow-induced force acting on an externally arranged permanent magnet (or a magnet system) and being proportional to the velocity (or mass flux) of the flow. This force is equal in magnitude to the braking Lorentz forces induced in the moving conductor. In case of flow rate measurement, the magnetic field lines of the used permanent magnet (or magnet system) penetrate the entire cross-section of the flow. In contrast, in local Lorentz force velocimetry (LLFV), tiny permanent magnets are used of which the penetration depth of its field lines is much smaller than the dimension of the flow. The present study aims to extend LLFV to liquid metal two-phase flow measurement. Such flows are of interest in high-temperature metallurgic processes, such as continuous casting of steel, where injection of argon bubbles into the melt is applied to prevent clogging, to mix the melt and to remove inclusions. In a first test, we investigate the transient response of Lorentz force to a simple arrangement of bubble/particle injected into liquid melt GaInSn at rest. The results show that the recorded Lorentz forces vary significantly and their maximum values are different for each rising bubble/particle. The shapes of Lorentz force signals depend on local liquid flow structures and non-conducting volume effects, both of which are dominated by bubble/particle positions. Figs 12, Refs 15.