Alternative transient eddy-current flowmetering methods for liquid metals

• Published in: Flow measurement and instrumentation 2019-03, Vol.65, p.150-157
• Main Authors: Looney, Richard, Priede, Jānis
• Format: Article
• Language: English
• Subjects: Eddy current; Electromagnetic flowmeter; Liquid metal
• ISSN: 0955-5986; 1873-6998
• DOI: 10.1016/j.flowmeasinst.2018.11.011

We present a comprehensive numerical analysis of alternative transient eddy-current flowmetering methods for liquid metals. This type of flowmeter operates by tracking eddy-current markers excited by the magnetic field pulses in the flow of a conducting liquid. Using a simple mathematical model, where the fluid flow is replaced by a translating cylinder, a number possible alternative measurement schemes are considered. The velocity of the medium can be measured by tracking zero crossing points and spatial or temporal extrema of the electromotive force (emf) induced by transient eddy currents in the surrounding space. Zero crossing points and spatial extrema of the emf travel synchronously with the medium whereas temporal extrema experience an initial time delay which depends on the conductivity and velocity of the medium. Performance of transient eddy-current flowmetering depends crucially on the symmetry of system. Eddy current asymmetry of a few per cent makes the detection point drift with a velocity corresponding to a magnetic Reynolds number Rm∼0.1. With this level of asymmetry transient eddy-current flowmetering can be reliably applicable only to flows with Rm≳0.1. A more accurate symmetry adjustment or calibration of flowmeters may be necessary at lower velocities. •Alternative measurement schemes of the transient eddy-current flowmeters for liquid metals are considered and a comprehensive numerical analysis of their operation is presented.•It is pointed out for the first time that the operation of transient eddy-current flowmeters relies crucially on their symmetry.•Our results may be useful for designing more accurate and reliable transient eddy-current flowmeters for liquid metals.