抄録
Ultrasonic vortex flowmeters are often applied, such as for semiconductor production equipments, since the significance of the fluid control with low-maintenance flow measurement is remarkably increasing in these days. However, it is difficult to measure the flow velocity of gas-liquid two-phase flows, which are associated also with the chemical and biomedical engineering, with the use of ultrasonic vortex flowmeters. To examine the character of the reflection of ultrasonic by the small gas bubbles, reflectivity of the ultrasonic signals in gas-liquid two-phase flows has been measured. As a result, we found that the character of the reflection of damped ultrasonic was determined by void fraction and dispersion of the bubble. On the other hand, the relation between the flow velocity and the vortex shedding frequency was independent on the presence of gas bubbles. This suggests that the auto gain control (AGC) to amplify the ultrasonic amplitude would be effective.
