Development of Microbubble Generation Method

摘要

In microbubble drag-reducing technology, the energy consumption in microbubble generation is often too large to achieve a high efficient energy conversion. The purpose of this research is to improve the efficiency of the microbubble generation method in practical applications. In this paper, microbubbles are generated by a special designed nozzle, whose principle is a converging flow. In water, it is possible to generate bubbles, whose diameter ranges from 1.5 to 4 mm, by using this nozzle. If a very little amount of Cetyltrimethy-lammonium Chloride (CTAC) surfactant is added to the water at T = 20°C, the average diameter of bubbles of 46.7-48.6 μm can be generated because of the reduction of the surface tension of the bubbles. It was found that the amount of air injected showed weak influence on the generated bubble size. It was also found that the counter-ion sodium salicylate (NaSal) could assist to enlarge the bubble and reduced the bubble dispersion due to the change of fluid property. After adding NaSal to the CTAC solution, the average bubble diameter generated was enlarged to 122 μm, however, this bubble size is still effective to reduce the turbulence drag in practical application.