Abstract:
This thesis deals with the theoretical and experimental investigation of two-phase flow
for a dielectric liquid electromagneticf lowmeter. So far only limited investigationsi nto
the possibleu se of electromagneticf lowmeters for multiphasef low measuremenht ave
been made. These have been restricted to electromagnetic flowmeters designed for
conducting water based (electrolytic) fluids. The possibility of designing
electromagnetic flowmeters for use with insulating (dielectric) fluids such as oil and
petrol has been existed for some years. However the measuremenot f two-phase flow
of insulating fluids using electromagnetic flowmeters and the application of this
knowledge to the measurement of the separate phases has not yet been a subject for
research. An analytical model is developed which evaluates a transformer signal that is
produced on the electrodes when a bubble unbalances eddy currents while it passes
through the meter. The shape and magnitude of this signal for various positions in the
pipe cross-section is investigated. The behaviour of this transformer signal for various
electrode shapes is studied as well and it is found that when using large area electrodes
the position of the amplitude along the pipe axis remains almost constant. For
measuring the speed of bubbles passing through the meter a frequency analysis is
carried out and shows that the peak frequency of the signal is proportional to the
velocity of the bubbles. A flowmeter is built to carry out experimental work. The first
sets of experiments are carried out with plastic beads fixed on a thin string which is
attached around two wheels. The speed of the beads is adjusted by an electromotor
which powered one wheel. In a second experimental design gas bubbles are injected in
a vertical pipe which is filled with dielectric oil. Both types of experiments exhibit the
behaviour predicted in theoretical analysis.