Ultrasound tomography system used for monitoring bubbly gas/liquid two-phase flow

This paper is about a transmission-mode (TM) ultrasound computerized tomography (UCT) system, which is used to monitor a bubbly gas/liquid two-phase flow, a kind of strongly inhomogeneous medium. Because of the high contrast in acoustic impedance distribution of the flow, TM UCT system can only obtain incomplete tomographic projections which depend on the distribution of bubbles in liquid. In order to describe this characteristic, a mathematical model was established. The algorithms used to reconstruct the profile of a distribution of bubbles over a 2-D cross-section of a pipe, for both parallel beam scanning geometry and fan-shape beam scanning geometry, were presented. By using a two-value (0/1) logical back-projection filtering algorithm, a real-time transmission-mode (TM) ultrasound computerized tomography (UCT) system involving fan-shape beam geometry had been developed. Both simulations and experiments showed that the performance of the system was acceptable with an image reconstruction speed of 41.7 frames per second and a data acquisition speed of 667 frames per second if a Pentium/90 compatible computer was used. Finally, possible future improvements of the system were discussed.