抄録
Magnetic flowmeters, which have been one of the standard instrument to measure liquid flowrate in industry, were applied to tomographic imaging of flow velocity field, based on the fact that there are no exciting magnetic fields that induce the flow signal proportional to volumetric flowrate free from the velocity profile. Two-dimensional case was examined theoretically for the reason of simplicity, and a flowmeter with eight magnetic coils and eight signal pick-up electrodes was developed. Driving alternating current of unit ampere was fed to eight combinations of pairs of the coils and induced electro-motive force were picked up across eight combinations of pairs of the electrodes. Flows in a pipe were assumed to be fully developed and axially symmetric since the straight approach flow has the length of forty-five times of the pipe diameter (45D). Since field interaction model of the meter is ill-posed, some prior knowledge, such as non-negativeness of the flow velocity and smoothness of the profile, was introduced to reconstruct the velocity profile.
In order to examine the possibility of reconstructions for various velocity profiles, to make different velocity profiles is needed. When the pipe is shifted perpendicularly to its axis, the weight function is different from what it was. Therefore the shift of the pipe position was treated instead of the different velocity profiles for simplicity. As a result, when the pipe was shifted, the same reconstruction regardless to displacement was achieved. The flowrate estimated with the present equipment agreed with a commercially available standard magnetic flowmeter within 5% accuracy.
