A new bubble generator for creation of large quantity of bubbles with controlled diameters

A novel bubble generator was proposed and studied. The generator provides a considerable enhance of the bubble formation in two-phase flow. The generator comprises a number of hollow cylindrical bushings sequentially installed in the flow and deployed relative to each other by 90°. Each bush has two holes of equal diameters which are located at its side surface in the central plane of flow channel. Air is supplied to each bush. The bubble diameters and velocities were measured using the Phase Doppler Particle Analyzer (PDPA) at constant water flow rate equal to 1.38×10 −5 m 3 /s and air flow rate in the range 12.5×10 −7 −0.5×10 −5 m 3 /s. The tests showed that the distribution of the bubble diameters and their velocities remain almost the same in spite of change in air flow rate by a factor of 4. The diameter of bubbles was 0.6–0.8 mm and has 2 maximum points, namely, in regions of 630 µm and about 800 µm which correspond to the bubble size at the outlet from air holes, and the second maximum is a result of bubble coalescence. Their average velocity at the measurement point is close to zero that indicates a high vorticity of the flow.