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

本研究旨在开发一种利用空化流的主动控制来大规模生产微米级液滴的新方法。在喷嘴内的液体流动中，湍流是由空化气泡的崩塌引起的，它们促进了喷嘴喷射后液体的雾化。首先，得到了最适合雾化的空化流形式。其次，澄清了雾化条件，以获得最合适的空化流形式。最后，研制了一种具有空化流主动控制的新型空气雾化喷嘴，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条件下，仅通过空化数就可以对空化流的形式进行分类。随着空化数的减小，空化流的形式由平滑流、云状空化流、片状空化流和水力翻转流转变而来。在雾化空气的低速下，空化流的形式对喷雾特性影响很大。片状空化流促进了雾化，而液压翻转使雾化恶化。在高速雾化空气条件下，一种空化流形式对平均直径的影响变小，而雾化空气速度对平均直径的影响起主导作用。在本实验中，最小平均液滴尺寸约为20 μ m。似乎有可能使最小平均液滴尺寸小于20？通过设计液体与雾化空气之间的碰撞方法。

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.