A new micro-bubble generator with a spherical body in a flowing water tube has been invented, and its trial products have been tested. In the generator, pressurized water is introduced into a pipe with a spherical body in the core. From conservation equations of mass and energy, the water velocity around the body especially in a downstream region becomes higher than the inlet velocity, and thus the pressure there becomes lower. If the pressure becomes less than atmospheric pressure, air is automatically sucked into the water stream through a number of small holes drilled on the pipe wall in the lower pressure region downstream from the center of the body. Since the water flow there is highly-turbulent and shear flow, the air sucked is well broken into a great number of micro-bubbles. In the tests of its trial products, experimental data on air suction rate, hydraulic power needed to introduce water, bubble generation efficiency, and variation of dissolved oxygen in water after bubbling were obtained by changing water supply rate systematically. From the tests, we found an optimum diameter ratio of spherical body to pipe, and confirmed that the generator could generate micro-bubbles with a lesser energy consumption rate within 40W and raise effectively the dissolved oxygen, etc. (c) 2004 Elsevier Inc. All rights reserved.
