Flow measurement in metal melts using a non-contact surface velocity sensor based on time-of-flight Lorentz force velocimetry

This paper attempts to present a novel development of an electromagnetic non-contact surface velocity measurement technique in electrically conducting liquids which could be applied in high-temperature metallurgical processes involving metal melts. The technique is based on Lorentz force velocimetry, i.e. on measuring the force which is generated by the interactions of the melt flow and an externally applied magnetic field that is spanned by permanent magnet system. The electromagnetically induced force pushes the magnet system into the direction of the flow and can be measured using a force sensor that is attached to the magnet system. As the measured force linearly depends on melt velocity, a non-contact evaluation of the velocity can be achieved. However, the recorded force also depends on the electrical conductivity of the melt. In application this material property is a priori unknown as it strongly depends on both temperature and composition of the melt. Hence, calibration of such a measuring device becomes a cumbersome task. Our development aims to circumvent this deficit by applying a time-of-flight technique. According to this principle we design and test a prototype of sensor for measuring free-surface velocity. In the model experiments we use both solid bodies and the liquid metal GaInSn as test liquids.