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A Study on the Improvement of Submerged Water Jet Performation by the Efficient Use of Cavitation

有效利用空化提高水下射流性能的研究

基本信息

批准号：
12555044
负责人：
FUJIKAWA Shigeo
金额：
$ 6.85万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The present study has been done to develop an alternative submerged water jet system which is operated at a moderately low level of discharge pressure and is capable to improve the efficiency and safety in operation of customarily used systems. The main results of the study are as follows.(1)Novel experimental methods were developed to generate micro-bubbles in liquid and to measure their properties. The injection of compressed air into water through a rotating multi-hole disk enabled to produce micro-bubbles with their diameter of 10〜40[μm] and number density of (1〜4) x10^5[number/cm^3] which were measured by a newly-developed image processing technique.(2)The generation and development of cavitation bubbles in a starting submerged water jet were investigated at jet exit speeds of 15〜20[m/s]. A prominent feature of bubbles generated at the early stage of jet development was found to form a shape similar to a vortex ring. The average trajectory, size and geometry of the ring-like bubbles were evaluated from photographic data.(3)Experiments on the decomposition of organic compounds in water were made using a new submerged water jet system where the cavitating water jet was discharged through a specially designed nozzle. The result indicated that the decomposition of organic compounds could be achieved under the discharge pressure much lower than that of currently available systems.(4)A new computational method based on the two-fluid model was developed to calculate submerged water jet flows. By taking into account of both a surface average pressure of liquid at the gas-liquid interface and a phase change across the interface, it became possible to describe the occurrence of locally high pressure at the collapse of cavitation bubbles.

本研究的目的是开发一种替代的水下喷水系统，该系统在适度低的排放压力下运行，并且能够提高常用系统运行的效率和安全性。主要研究结果如下：(1)开发了在液体中产生微气泡并测量其性质的新实验方法。通过旋转多孔盘将压缩空气注入水中，可产生直径为 10〜40[μm]、数密度为 (1〜4) x10^5[个/cm^3] 的微气泡，并通过新开发的图像处理技术进行测量。（2）在射流出口速度为 15〜20[米/秒]。发现射流发展早期产生的气泡的一个显着特征是形成类似于涡环的形状。根据照片数据评估环状气泡的平均轨迹、尺寸和几何形状。(3)利用新型浸没式水射流系统进行了水中有机化合物的分解实验，其中空化水射流通过特殊设计的喷嘴排出。结果表明，在比现有系统低得多的排放压力下，可以实现有机化合物的分解。(4)提出了一种基于双流体模型的水下射流计算方法。通过考虑气液界面处液体的表面平均压力和界面上的相变，可以描述空化气泡破裂时局部高压的发生。