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International Society for Industrial Process Tomography

8th World Congress on Industrial Process Tomography

An Adaptable Sensor for Electromagnetic Flow Tomography utilizing an Axially Split Symmetric Ferromagnetic Circuit

J. C. Abrolat and T. Musch

Institute of Electronic Circuits – Ruhr-University Bochum Universitaetsstr. 150, 44801 Bochum, Germany jan.abrolat@est.rub.de

ABSTRACT

Asymmetric flow profiles often occur directly behind pipe bends and in multiphase flows, which are challenging for standard flow meters. Electromagnetic Flow Tomography (EMFT) uses a setup consisting of multiple field coils and multiple electrodes to determine the velocity distribution along the pipe’s cross section. This allows for accurate measurements in these cases. Previously developed EMFT systems apply magnetic field coils constructed as pairs of air coils with large diameters. However, such a construction contradicts a compact sensor design with many magnetic field poles, which is especially favorable for multiphase flow applications. In this contribution, we propose a new sensor design, consisting of two parallel rings of field coils on the surface of the measuring pipe. The coils are arranged in close proximity to the electrodes and enclosed in two magnetic circuits to minimize the excitation current and coil size. A great advantage of this design is the variability of the generated magnetic fields, enabling further investigations of local flow velocities with highly localized flux densities. We developed a forward model of a sensor with 12 electrodes and 24 field coils, by means of 3D electromagnetic field simulations. After computation of the magnetic fields and electrode weight functions, the corresponding voltages for different velocity profiles are calculated. Based on the forward model, a reconstruction method with an additional calibration function is implemented, and the functionality of the sensor is validated. Moreover, the accuracy of the velocity distribution reconstruction was verified with respect to different levels of electrode noise.

Keywords electromagnetic flow tomography, flow meter, velocity profile

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