Numerical investigation on the installation effects of electromagnetic flowmeter downstream of a 90°elbow-laminar flow case

摘要

An electromagnetic flowmeter installed downstream of a 90° elbow to measure the flow-rate of laminar flow is numerically simulated to investigate installation effects by varying the location of the electromagnetic flowmeter at a distance up to22D from the elbow, and the angle between the electrodes plane and the symmetry plane of the elbow atφ= 0, 45 and 90°. Effects of the curvature radius (R{sub}c) and the Reynolds number (Re) based on a diameter D are also scrutinized in the range of400≤ Re≤1500 and R{sub}c 1.5D and 3.0D.For the simulation of an electromagnetic flowmeter, a commercial code FLUENT(ver. 4.4) is applied for flow field analyses and a three-dimensional numerical code is developed for analyzing the magnetic field. The developed code adopts a finite volumemethod to solve a Poisson-type voltage equation for the magnetic field.It is found that the deviations of the flow signal due to the disturbance from the elbow is strongly dependent on the pattern of axial velocity contours. Cases forφ = 45° are found to permit significantly better measurement accuracy in comparison withφ = 0° andφ = 90°, and the effect of the curvature on the optimum installation distance depends on the Reynolds number. The present numerical simulation method is found to be a useful tool for the performance analysis of the electromagnetic flowmeter.