Velocity Vector Measurement of Dispersed Bubbles in Horizontal Gas-Liquid Slug Flows by Using Ultrasonic Doppler Method

Horizontal gas-liquid slug flows are widely encountered in industrial production fields, such as energy, pharmaceutical and petrochemical industry. The gas-liquid slug flows present pseudo-periodic motion alternating between the film regions and the slug regions, and dispersed bubbles are distributed in slug region. The velocity distribution of dispersed bubbles is an important parameter in the gas-liquid slug flow. In this paper, an ultrasonic Doppler measurement system was designed, and the horizontal gas-liquid two-phase flow experiment was carried out to obtain the echo signals of ultrasonic sensor. Based on the echo signals, the instantaneous velocity profiles were extracted. Then we acquired the spatial-temporal distribution of velocity vectors. The relative velocities between dispersed bubbles and Taylor bubbles were calculated in order to observe the coalescence and detachment process. The results show that with the increase of the mixing velocity, the velocities of dispersed bubbles become particularly instable, leading to a complicated coalescence and detachment behavior.