Size Distributions of Micro-bubbles Generated by a Pressurized Dissolution Method
Size of micro-bubbles is widely distributed in the range of one to several hundreds micrometers and depends on generation methods, flow conditions and elapsed times after the bubble generation. Although a size distribution of micro-bubbles should be taken into account to improve accuracy in numerical simulations of flows with micro-bubbles, a variety of the size distribution makes it difficult to introduce the size distribution in the simulations. On the other hand, several models such as the Rosin-Rammlcr equation and the Nukiyama-Tanazawa equation have been proposed to represent the size distribution of particles or droplets. Applicability of these models to the size distribution of micro-bubbles has not been examined yet. In this study, we therefore measure size distribution of micro-bubbles generated by a pressurized dissolution method by using a phase Doppler anemometry (PDA), and investigate the applicability of the available models to the size distributions of micro-bubbles. Experimental apparatus consists of a pressurized tank in which air is dissolved in liquid under high pressure condition, a decompression nozzle in which micro-bubbles are generated due to pressure reduction, a rectangular duct and an upper tank. Experiments are conducted for several liquid volumetric fluxes in the decompression nozzle. Measurements are carried out at the downstream region of the decompression nozzle and in the upper tank. The experimental results indicate that (1) the Nukiyama-Tanasawa equation well represents the size distribution of micro-bubbles generated by the pressurized dissolution method, whereas the Rosin-Rammler equation fails in the representation, (2) the bubble size distribution of micro-bubbles can be evaluated by using the NukiyamaTanasawa equation without individual bubble diameters, when mean bubble diameter and skewness of the bubble distribution are given, and (3) an evaluation method of visibility based on the bubble size distribution and bubble number density is proposed, and the evaluated visibility agrees well with the visibility measured in the upper tank.
Micro-bubble Bubble size distribution Pressurized dissolution method Phase Doppler anemometry
C. Taya Y. Maeda S. Hosokawa A. Tomiyama Y. Ito
Kobe University,1 -1 Rokkodai,Nada,Kobe 657-8501, Japan Panasonic Electric Works Co. Ltd, 1048 Kadoma, Osaka 571-8686, Japan
国际会议
The 7th International Symposium on Measurement Techniques for Multiphase Flows(第七届国际多相流测试技术会议)
天津
英文
199-206
2011-09-17（万方平台首次上网日期，不代表论文的发表时间）