Optimization of Orifice Shape and Oscillatory Displacement of an Ultrasonic Microbubble Generator to Increase Microbubble Yield

摘要

Microbubbles have various properties such as low rising velocity and large surface area per unit volume. Owing to these favorable properties, there has been a recent increase in the application of microbubbles in the agricultural and medical fields, including the development of a microbubble generator, which employs a hollow cylindrical ultrasonic horn. In this device, gas is supplied through a path in the horn to create a gas-liquid interface in water. Thereafter, ultrasonic oscillation is irradiated to the surface to generate microbubbles. However, to realize practical applications of microbubbles, a higher yield is required. This study aims to increase the microbubble yield by modifying the shape of the orifice at the horn end and evaluating the resulting microbubble yield by measuring the concentration of oxygen dissolved in water. The horn end contains side orifices and releases bubbles between walls; it achieved an increase of up to 60% in the generation of microbubbles. This increase is likely because this modified design enables better reception of strong ultrasonic oscillations, as compared to conventional straight orifices. The effect of ultrasonic amplifications were also evaluated.