Abstract
Measurement error in an electromagnetic flow meter appears if magnetic and electric properties of admixtures are different from that of the fluid. Expressions of the error, which depends on volume concentration, permeability, and electric conductivity of particles were obtained by approximating the particles’ shape as an ellipsoid. Components of the error, which appear inside particles and outside particles in active zone of flow meter, with any canal form are investigated. Expressions of the error are presented assuming that particles are oriented in various directions with respect of the flow direction and are spinning. Different cases of magnetic and electric admixtures properties are discussed. Error expression obtained for flows with nonconductive and nonmagnetic particles coincides with experimental and modelling results obtained by other explorers for flows with air bubbles. Magnetic particles with high electric conductivity are especially dangerous. Extra measurement error in this case greatly depends on the shape of the particle. Measurement error increases if particle shape differs from a sphere. The complementary measurement error can exceed the volume concentration of particles by ten times if the ratio between the longest and the shortest axes of ellipsoid exceeds 3.
Highlights
Electromagnetic flow meters (EMFM) for measuring ionic fluid flow in closed completely filled pipes are investigated in this paper
Considering that the weight vector can be different in any point of the active zone, we express the value of measurement signal U0 when there are no admixtures in the flow:
Expressions of the measurement signal errors when the fluid is contaminated by small magnetic particles depending on the volume concentration, permeability, and electric conductivity of particles are obtained in Reference [14] for spherical particles and for an ideal electromagnetic flow meter with a rectangular duct and infinitely conductive large electrodes
Summary
Electromagnetic flow meters (EMFM) for measuring ionic fluid flow in closed completely filled pipes are investigated in this paper. Theoretical foundations of these meters, summarized by J.A. Shercliff [1], lead to the creation of accurate and reliable measuring instruments. The ability of assessing the sensitivity to velocity distribution [3], the influence of channel electrical properties on calibration [4,5], including the case when closed pipe is not completely filled [6], and setting of weighting functions has been simplified [7]. Further development of multiphase flow measurement theory is hampered by the insufficient analysis regarding how different electric and magnetic properties of admixtures in the flow and particles shape influence the accuracy of EMFM. This article summarizes results of the research carried out by the Kaunas University of Technology
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