A measurement device for electromagnetic flow tomography

Abstract

Electromagnetic flow meters have succesfully been used in many industries to measure the mean flow velocity of conductive liquids. This technology works reliably in single phase flows with axisymmetric flow profiles but can be inaccurate with asymmetric flows, which are encountered, for example, in multiphase flows, pipe elbows and T-junctions. Some computational techniques and measurement devices with multiple excitation coils and measurement electrodes have recently been proposed to be used in cases of asymmetric flows. In earlier studies, we proposed a computational approach for electromagnetic flow tomography (EMFT) for estimating velocity fields utilizing several excitation coils and a set of measurement electrodes attached to the surface of the pipe. This approach has been shown to work well with simulated data but has not been tested extensively with real measurements. In this paper, an EMFT system with four excitation coils and 16 measurement electrodes is introduced. The system is capable of using both square wave and sinusoidal coil current excitations and all the coils can be excited individually, also enabling parallel excitations with multiple frequencies. The studies undertaken in the paper demonstrate that the proposed EMFT system, together with the earlier introduced velocity field reconstruction approach, is capable of producing reliable velocify field estimates in a laboratory environment with both axisymmetric and asymmetric single phase flows.

State estimation approach to dual-modal imaging of two-phase flow based on electromagnetic flow tomography and electrical tomography

“…EMFT is a novel imaging modality introduced and studied numerically in [8,20], and further validated experimentally in [7,21]. By ET, which is the second modality in this study, we refer to imaging of electrical conductivity based on electric current measurements from the object's surface corresponding to a set of potential excitations.…”

“…In the EMFT data simulation, three magnetic field excitations were run sequentially, so that at each time index, one of the three excitations was performed. Two of the magnetic fields were nearly uniform along the x-and y-axes, and the third corresponded to a nearly anti-Helmholtz magnetic field excitation [9]. This method collected 16 voltage measurements at each time index.…”

“…In ET, a frame used for one reconstruction consisted of current data corresponding to 48 potential excitations (a total of 1128 current measurements). In EMFT, a frame was formed by potential data corresponding to all three magnetic field excitations (a total of 48 voltage measurements) [9]. However, in order to produce EMFT reconstructions in the same rate as in state estimation, we used the so-called sliding window principle [39], i.e.…”

“…Here, ET refers to an imaging modality which is practically equal to ERT, but the measurements are carried out in a slightly different manner which will be explained in subsequent section. EMFT, by contrast, is a novel imaging technique where the velocity field of the fluid is reconstructed based electrode potentials induced under the influence of magnetic field excitations [8,9].…”

Study on a New Electromagnetic Flow Measurement Technology Based on Differential Correlation Detection

“…Since the traditional EMF cannot distinguish between the actual flow signal and interference noise, thereby only eliminating one type of interference, interference noise cannot be removed synchronously. Inappropriate noise elimination even introduces new interference to the system, leading to a lower measurement accuracy [5][6][7]. Therefore, great significance is attached to improving the signal-to-noise ratio, distinguishing interference components, and eliminating interference.…”