Measurement of Two-phase Flow using Multi-wave Ultrasound (Measurement of Bubble Rising Velocity using Correlation Method)

Abstract

In this paper, two types of ultrasonic measurement techniques are attempted to obtain liquid and gas velocity distributions in bubbly flow. The first attempt is that the both of liquid and gas velocity distributions are obtained using an ultrasonic basic frequency and its echo signals. In order to separate the signals reflected on liquid-gas interfaces and particles, thresholding based on the ultrasonic echo intensity is applied. However, it is difficult to extract completely the echo signals reflected on the tracer particles. In order to overcome the difficulty, a multi-wave ultranonic transducer (TDX) is applied. The TDX consisted of two piezoelectric elements that have different basic frequency. The liquid velocity distribution is obtained using an ultrasonic velocity profiles (UVP) monitor at 8 MHz ultrasonic frequency, and the rising velocity of bubbles is measured using cross-correlation method at 2 MHz ultrasonic frequency. Using the technique, both of the liquid and gas velocity distributions are obtained accurately using the TDX.