Development of two-phase flow measurement technique using multi-wave ultrasonic transducer

Full text of publication follows: In this paper, a new technique for multi-phase flow measurement is proposed. This technique is based upon the ultrasonic Doppler method (UDM). Using different sizes of ultrasonic transducer (TDX) for the UDM measurement, the measured data apparently differ. Because the bubble rising velocity is higher than the liquid velocity, the velocity PDF of the bubbles is higher than that of the liquid at each channel. With a change in the measurement volume, the velocity PDF significantly changes. Furthermore, the ultrasonic refraction from the particle changes as changing of the relative size between the objectives and ultrasonic beam diameter. Applying this method for multi-phase flow, several kinds of particles which sizes are greatly different can be measured for each velocity distributions. To emit different sizes of ultrasonic beam at the same time and the same position, the Multi-wave TDX is newly developed. The new TDX consists of special ultrasonic element. The ultrasonic element has two basic frequencies. The central 3 mm-diameter area has 8 MHz basic frequency and the outer area has 2 MHz frequency. Generally, the size of element corresponds to its basic frequency. The Multi-wave TDX can emit ultrasonic independently for 2 MHz and 8 MHz basic frequencies. Using the new TDX, a new technique for measurement of multi-phase flow is proposed to measure the each velocity. First step of this method, the new technique is applied for measurement of bubbly flow. Using the velocity difference between bubble rising velocity and the liquid velocity, the accuracy of this method is investigated. For the next step, the measurement of multi-phase flow mixing of particles, liquid and bubble is carried out. (author)