Abstract
An ultrasonic computed tomography (UCT) developed for measuring time-averaged cross-sectional distributions of gas and solid concentrations in three-phase flow is described. The ultrasonic computed tomography is a coupling of a transmission mode ultrasonic sensor developed in Department of Chemical Engineering, Shizuoka University and a tomographic reconstruction technique based on dynamic neural network optimization algorithm developed in Department of Chemical Engineering, The Ohio State University. The ultrasonic sensor is based on measurements of the energy attenuation and the velocity change of ultrasonic pulse waves transmitted through the three-phase medium, enabling the measurements of the gas and the solid concentrations in the system simultaneously. The tomographic reconstruction technique has been proven to reconstruct simulated tomographic data accurately even with a very small number of projection data as used in the measurement. The application of the technique to a water-air-particles flow system in a bubble column is described.Glass-beads with diameters of 100, 260 and 350 micron meters are used as the solid phase. The time-averaged macroscopic flow structure and the behavior of the gas bubbles and solid particles distributions are investigated. The effects of gas velocity, solid loading and particle diameter to the behaviors of bubbles and particles distributions in the three-phase system are also discussed.
