Behavior of gas injected through a helical tuyere into water

Gas behavior in water, splash amount and mass transfer rate between gas and liquid of a helical tuyere in which swirl flows formed were investigated, and compared with those of a conventional circular tuyere. Three kinds of helical tuyere were used for the experiments: 1) a tuyere divided by a twisted sheet inside a circular tube to form two partitions, 2) a tuyere clogging one of the two partitions of 1), and 3) a tuyere comprising three twist-bundled circular tubes. The back attack phenomenon was diminished or its frequency was decreased when gases were injected into water through multiple holes with different jet angles because of increased shear stress at the interface of the gas cavity into the tuyere. The diameters of both the formed and rising gas bubbles in the helical tuyere were smaller than those in the circular one, for the same reason as discussed above in the back attack phenomenon. Gas through the helical tuyere spread in the transverse direction, whereas gas injected by the circular tuyere was concentrated in the middle of the vessel. The splash amounts of the helical tuyere were less than those of the circular one because vertical momentum and rising gas velocity were small. The increase in interface area between gas and liquid resulting from the smaller bubble diameter and rising gas velocity of the helical tuyere enhances the mass transfer rate between gas and liquid, compared with the circular tuyere.