Mass production method of micron liquid droplets by active control of cavitation flow

本研究旨在发展一种利用空化流主动控制的微米级液滴批量生产新方法。空化气泡的溃灭在喷嘴内的液体流动中引起湍流，并且它们促进从喷嘴喷射后的液体射流的雾化。首先，得到了最适合于雾化的空化流形式。接着，澄清雾化条件以获得最合适的空化流形式。最后，研制了一种新型的空化气流主动控制气动雾化喷嘴，并对其喷雾特性进行了测试。通过以上实验，得到了以下结果：1.空化发生在低背压和高雷诺数的情况下，空化流的形式可以仅通过空化数进行分类.随着空化数的减小，空化流的形态由光滑流、云状空化流、片状空化流和水力翻转转变.在雾化空气流速较低的情况下，空化流的形成对喷雾特性有很大的影响。片状空化流促进雾化，水力翻转使雾化变差.在雾化空气流速较高时，空化流形态对平均直径的影响较小，雾化空气流速的影响占主导地位.在目前的实验中，最小的平均液滴尺寸约为20？M.这似乎是可能的，使最小平均液滴尺寸小于20？通过设计液体与雾化空气的撞击方式，

This research aims to develop a new mass production method of micron liquid droplets by using the active control of the cavitation flow. The turbulences are induced in the liquid flow inside a nozzle by the collapses of cavitation bubbles, and they promote the atomization of a liquid jet after injection from the nozzle. Firstly, the most suitable form of a cavitation flow for the atomization was obtained. Next, the atomization conditions were clarified to obtain the most suitable form of a cavitation flow. Finally, the new airblast atomizer with the active control of a cavitation flow was developed, and its spray characteristics were measured. From above experiments, the following results were obtained:1. The cavitation occurs at low back pressure and high Reynolds number, and the form of a cavitation flow can be classified by only the cavitation number.2. With the decrease of a cavitation number, the form of a cavitation flow changes from the smooth flow, cloud cavitation flow, sheet cavitation flow and hydraulic flip.3. Under the low velocity of an atomization air, the form of a cavitation flow affects greatly the spray characteristics. The sheet cavitation flow promotes the atomization and the hydraulic flip makes the atomization worse.4. Under the high velocity of an atomization air, the effect of a form of a cavitation flow on the mean diameter gets smaller, and that of a velocity of an atomization air becomes dominant.5. In the present experiments, the minimum mean droplet size is about 20?m. It seems to be possible to make the minimum mean droplet size smaller than 20?m by devising the impinge method between the liquid and the atomization air.