均一粒径を持つ極微細気泡生成技術の開発

开发出粒径均匀的超微细气泡发生技术

• 批准号: 16360094
• 负责人: TAKEMURA Fumio
• 金额: $ 9.15万
• 依托单位: National Institute of Advanced Industrial Science and Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360094/
• 关键词: Micro bubbles; Ultrasonic; Surface wave; Viscosity; Surface tension; 微小気泡

Consecutive images of the fragmentation of capillary waves in an ultrasonic field were obtained using a high-speed video camera through a microscope at a frame rate of 500,000 frames per second. The images showed that micro bubbles of uniform diameter from 4 to 15 μm were generated at a constant periodic rate when a small amount of gas was introduced into a highly viscous liquid whose kinematic viscosity was between 5 and 100 mm^2/s. Results revealed that (1) conditions for stable generation of micro bubbles are affected by excitation frequency, surface tension and viscosity of the liquid, and dimensions of the needle, (2) two controlling parameters for stable generation are the Weber number ( We = ρf^2d_<in>^3/σ, where ρ is density of the liquid, fis excitation frequency, dm is inner diameter of the needle, and a-is surface tension) and Womersley number (Wo+= d_<in>(flv)^<1/2>, where ν is the kinematic viscosity of liquid), and (3) uniform-diameter micro bubbles are generated stably when We < 300 and 2 < Wo < 5. Using a boundary element method, we also simulated this gas-liquid interface behaviour. Although the simulation model is simple because the flow field around the needle is assumed axisymmetrical and irrotational, the simulation results of the periodic interface behaviour and of the effects of liquid viscosity and gas pressure inside the needle qualitatively agreed with experimental results. Simulation and experimental results revealed that a micro gas bubble is generated by detachment of the top of a projection produced by propagation of a surface wave travelling from the outside to inside of the needle. The surface wave is produced by the difference in velocity near the needle wall, and is then propagated by surface tension. The size of the generated micro gas bubbles becomes uniform because the gas-liquid interface converges on periodic behaviour due to the influence of liquid viscosity.

利用高速摄像机通过显微镜以每秒500，000帧的帧速率获得超声场中毛细波破碎的连续图像。图像显示，当向运动粘度为5 ~ 100 mm^2/s的高粘度液体中引入少量气体时，以恒定的周期性速率产生直径为4 ~ 15 μm的均匀微气泡。结果表明：（1）微气泡稳定产生的条件受激励频率、液体的表面张力和粘度以及针的尺寸等因素的影响;（2）微气泡稳定产生的两个控制参数是Weber数（We = ρ <in>f^2d^3/σ，其中ρ为液体的密度，f为激励频率，dm为针的内径，a-为表面张力）和Womersley数（Wo+= d_<in>（flv）^&lt;1/2&gt;，其中v为液体的运动粘度）;（3）当We &lt; 300和2 &lt; Wo &lt; 5时，可以稳定地生成直径均匀的微气泡。使用边界元法，我们还模拟了这种气液界面行为。虽然模拟模型是简单的，因为周围的流场是假设轴对称和无旋，模拟结果的周期性界面行为和液体粘度和气体压力的影响，针内定性与实验结果一致。模拟和实验结果表明，微气泡产生的突起的顶部的分离所产生的表面波传播从外部到内部的针。表面波是由针壁附近的速度差产生的，然后由表面张力传播。由于液体粘度的影响，气-液界面收敛于周期性行为，所产生的微小气泡的尺寸变得均匀。

项目成果

Generation of Micro Gas Bubbles of Uniform Diameter in an Ultrasonic Field (1st Report, Effect of Viscosity on Stable Generation of Bubbles of Uniform Diameter)

超声波场中均匀直径微小气泡的产生（第一次报告，粘度对均匀直径气泡稳定产生的影响）

• 发表时间: 2004
• 期刊: Transactions of the Japan Society of Mechanical Engineers B 70-699
• 作者: Toshinori MAKUTA;Fumio TAKEMURA;et al.
• 通讯作者: et al.

The history force on a rapidly shrinking bubble rising at finite Reynolds number

快速收缩的泡沫在有限雷诺数下上升的历史力量

• 发表时间: 2004
• 期刊: Physics of Fluids 16・9
• 作者: Fumio TAKEMURA;Jacques Magnaudet
• 通讯作者: Jacques Magnaudet

超音波場における均一微細気泡生成過程 第二報 均一気泡生成現象における安定生成条件

超声波场中均匀细小气泡的生成过程第二次报告均匀气泡生成现象的稳定生成条件

• 发表时间: 2005
• 期刊: 日本機械学会論文集B編 71-710
• 作者: 幕田;竹村他
• 通讯作者: 竹村他

超音波場における均一微細気泡生成過程(第一報、均一気泡生成に対する粘性の影響)

超声波场中均匀细小气泡的产生过程（首次报道，粘度对均匀气泡产生的影响）

• 发表时间: 2004
• 期刊: 日本機械学会論文集B編 70-699
• 作者: 幕田寿典;竹村文男他
• 通讯作者: 竹村文男他