Methods and apparatus for generating gas bubbles

A method for generating gas bubbles in a liquid, the method comprising:

• providing a bubble generator comprising:
• a casing defining a casing bore extending longitudinally therethrough;
• a diffuser located in the casing bore, the diffuser defining a diffuser bore extending longitudinally therethrough, the diffuser bore comprising a fluid-input region at or near a fluid-input end of the diffuser and a fluid-output region at or near a fluid-output end of the diffuser, a cross-sectional area of the diffuser bore in the fluid-input region greater than a cross-sectional area of the diffuser bore in the fluid-output region;
• wherein at least a portion of the diffuser is porous for permitting a flow of pressurized gas from a region of the casing bore located outside of the diffuser and the diffuser bore, through the porous portion of the diffuser, and into the diffuser bore;
• wherein the casing comprises a gas-input opening which provides fluid communication with the region of the casing bore located outside of the diffuser and the diffuser bore;
• connecting the fluid-input region of the diffuser bore to receive a liquid at sufficient pressure to create a pressure gradient of the liquid in the diffuser bore to cause the received liquid to flow longitudinally in the diffuser bore toward the fluid-output region of the diffuser bore;
• and
• connecting the gas-input opening to receive gas at a pressure higher than the pressure of the liquid in the diffuser bore, such that the gas received at the gas-input opening moves from the region of the casing bore located outside of the diffuser and the diffuser bore, permeates the porous portion of the diffuser, and enters the diffuser bore to mix with the liquid flowing longitudinally in the diffuser bore and the mixture of liquid and gas bubbles exits the fluid-output region of the diffuser bore.