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The tiny bubbles with diameters less than 1 m are called ultrafine bubbles (UFB). And the application of UFB in agriculture, fishery and environment is highly anticipated. In this study, the changes in the properties of oxygen, 5% hydrogen (95% nitrogen), and nitrogen UFBs were investigated with droplet formation. The UFB water was ejected through the orifice nozzle (diameter: 280pm) and formed tiny droplets. Particularly in the case of oxygen UFB, a change in the distribution of the bubble size was observed. We observed higher microbubble concentration and smaller bubble size below 50pm in the sprayed UFB water compared with in the control distilled water. The distribution of oxygen UFB itself changed before and after spraying, and its diameter tended to be larger. In addition, its water contained more MB, which resulted in a higher cleaning effect. [ABSTRACT FROM AUTHOR]

Micro bubbles measuring tens of micrometers or less in diameter have recently been paid much attention. Swirl-type, pressurizing dissolution, and perforated plate methods have been proposed for micro bubble generation. The swirl-type method can generate micro bubbles even under low-pressure power in a simple structure. The enlarged inlet diameter of the swirl chamber can reduce the average bubble diameter. This study examined the effect of the swirl chamber inlet diameter on the flow around chamber outlet in a swirl-type micro bubble generator by numerical analysis. The Inlet diameter of the swirl chamber was changed to 30 mm, 60 mm, and 90 mm, the flow velocity distribution and the wall shear stress around the chamber outlet were calculated. As a result, when the inlet diameter of the swirl chamber was enlarged, it was clarified that the circumferential flow velocity and the wall shear stress around the chamber outlet increased, which reduced the average bubble diameter. [ABSTRACT FROM AUTHOR]

Micro bubbles measuring tens of micrometers or less in diameter have recently been paid much attention. Swirl type, pressurizing dissolution, and perforated plate methods have been proposed for micro bubble generation. The swirl type method can generate micro bubbles even under low-pressure power in a simple structure. This study examined the effect of the swirl chamber inlet diameter on the bubble diameter in a swirl type micro bubble generator. The swirl chamber inlet diameter was varied in the range of 15-90 mm and the effect was examined. In order to clarify the effect of enlarged inlet diameter, the micro bubbles diameter was measured under changing water supply pressure and air flow rate, the behavior of air column in the swirl chamber was visualized, and the velocity distribution around outlet of swirl chamber was measured. As a result, when the swirl chamber inlet diameter was enlarged, the outflow form changed from an axial outflow to a radial outflow. The average bubble diameter could also be reduced. An average bubble diameter of 28 -m could be realized under the conditions of swirl inlet diameter of 90 mm and water supply pressure of 0.1 MPa gage. [ABSTRACT FROM AUTHOR]