Microbubble-generating apparatus

A microbubble generating apparatus having a cylindrical gas-liquid generating tank, a liquid supplying portion for supplying liquid to the gas-liquid generating tank, and a gas supplying portion for supplying gas to the gas-liquid generating tank, generating a swirling flow of the liquid supplied by the liquid supplying portion along an inner surface of a cylinder in the gas-liquid generating tank, producing gas-liquid which is a mixture of the supplied liquid and a gas that is generated by microbubbling the gas supplied from the gas supplying portion by a shearing force of the swirling flow, and discharging the produced gas-liquid, wherein

• a gas supplying port for supplying the gas to the gas-liquid generating tank by the gas supplying portion is disposed on one of circular wall surfaces sealing both end portions of the cylinder of the gas-liquid generating tank,
• an outer shell tank at least partially covering the gas-liquid generating tank is included,
• the outer shell tank forms a gap between a side wall forming a circumferentially curved surface of the cylinder of the gas-liquid generating tank and the outer shell tank as well as a gap between the circular wall surface of the gas-liquid generating tank disposed with the gas supplying port and the outer shell tank to define a space made up of the gaps as a flow passage of the liquid,
• the liquid is supplied to the flow passage on the outside of the circular wall surface, the supplied liquid flows into the flow passage on the outside of the side wall,
• the gas-liquid generating tank has liquid supplying ports in communication with the flow passage outside the side wall and the inside of the gas-liquid generating tank to supply the liquid supplied to the flow passage into the inside of the gas-liquid generating tank, a plurality of the liquid supplying ports are disposed at least in a radial direction of the side wall, a liquid supply direction is set such that the liquid swirls in a constant direction around an axis of the gas-liquid generating tank, and
• the liquid supplying portion supplies the liquid through the flow passage from the liquid supplying ports into the inside of the gas-liquid generating tank to generate the swirl flow.