A fine bubble generating device which generates fine bubbles by mixing a liquid continuously supplied from a liquid supply source and a gas supplied from a gas supply unit, and which discharges a gas-liquid mixture obtained by mixing the fine bubbles and the liquid together, the fine bubble generating device comprising:
- a bubble generator including a tubular body, a liquid introduction port, a gas introduction port, and a discharge port, the tubular body having a flow passage for the liquid in the tubular body, the liquid being introduced into the flow passage through the liquid introduction port, the gas being introduced into the flow passage through the gas introduction port, the gas-liquid mixture being discharged from the flow passage through the discharge port;
- a gas supply unit including a compressor and a gas supply port, the compressor being configured to pressurize the gas, the gas pressurized by the compressor being supplied to the bubble generator through the gas supply port, and
- a shower head connected to the bubble generator through a hose connected to the discharge port of the bubble generator, wherein
- the flow passage of the bubble generator extends substantially along a same axis from the liquid introduction port to the discharge port, a plurality of reduced diameter portions each having an inner diameter reduced are provided to the flow passage along a direction along which the liquid flows, and gas-liquid mixing portions are provided downstream of the respective reduced diameter portions in a contiguous manner, each of the gas-liquid mixing portions having an inner diameter larger than a minimum inner diameter of each of the plurality of reduced diameter portions,
- the gas introduction port of the bubble generator is formed of a plurality of through holes arranged along a circumferential direction of an outer wall of the tubular body, and is provided in a vicinity of a most upstream reduced diameter portion of the plurality of reduced diameter portions provided to the flow passage, and the gas introduction port communicates with the gas supply port of the gas supply unit, and
- the tubular body comprises the plurality of reduced diameter portions provided to the flow passage of the bubble generator,
- wherein the flow passage of the bubble generator has, from an upstream side to a downstream side of the flow passage, a first reduced diameter portion, a first gas-liquid mixing portion which is contiguous with the first reduced diameter portion, a second reduced diameter portion which is contiguous with the first gas-liquid mixing portion, and a second gas-liquid mixing portion which is contiguous with the second reduced diameter portion,
- wherein the first reduced diameter portion includes portions where the inner diameters are reduced and enlarged, and the second reduced diameter portion includes a portion where the inner diameter is reduced,
- the plurality of reduced diameter portions of the bubble generator is formed such that the minimum inner diameter of the second reduced diameter portion disposed downstream is smaller than the minimum inner diameter of the first reduced diameter portion disposed upstream, and
- the gas-liquid mixing portions of the bubble generator are formed such that the inner diameter of the second gas-liquid mixing portion disposed downstream is larger than the inner diameter of the first gas-liquid mixing portion disposed upstream.