Eddy-current flow meter response to spherical non-conductive inclusions travelling in a liquid metal

In this paper, we address the problem of characterizing the size and position of a spherical non-conductive inclusion in a conductive material. The characterization is done using an Eddy -Current Flow Meter (ECFM), a device usually used to measure the flow rate of liquid metals, but which is also sensitive to the second gaseous phase. ECFM responses to the passage of inclusions in a quiescent liquid metal are computed numerically. The signal amplitude and phase variations are analyzed for inclusions of different radii and radial positions travelling in the pipe. Two parameters are introduced to characterize these variations: the maximum amplitude of the ECFM signal and its corresponding phase. It is shown that a unique relation exists between these parameters and the size and position of the inclusion. The ECFM signal thus provides enough information to determine the size and position of the inclusions by means of an inverse method. This provides valuable information for low void fraction measurement in industrial liquid metal flows. (authors)