電極法による管内粒子の局所平均流速の測定

測定プローブの開発

抄録

An electric probe for measuring local velocity of particles in solid-liquid mixtures has been constructed and tested for its performance using four kinds of glass spheres, sand, and an oxidized iron powder.
The probe is composed of a supporting bakelite tube (dia. 4mm), a ceramic tube, and three ringlet electrodes made of Pt wire (dia. 0.3mm).
The electrodes are axially placed on the surface of the ceramic tube at intervals of 10mm.
The fluctuations of differential voltage between the middle and the upstream electrode were cross-correlated with those between the middle and the downstream electrode to determine the transit time in conjunction with the local velocity of particles.
Volumetric flow rates calculated from particle velocity distributions of upward flows in a vertical pipeline were compared with those obtained from an electric magnetic flow meter.
The accuracy of 6% in the sand and the glass sphere and 8% in the oxidized iron powder was achieved at the discharge velocity of about 3m/s.
A comparison of velocity distributions between the probe and the pitot tube in a horizontal pipeline revealed that the pitot tube measurement was insufficient in the region of high solid concentration.
Some difficulty was encountered in the measurement of velocity distributions in a steel pipeline due to the electric effect of the steel pipe. It was, however, solved by means of isolation amplifiers introduced into the measuring system.