Análisis experimental de procesos de atomización de líquidos basados en campos hidrodinámicos y electrodinámicos

Resumen

The controlled production of jets and droplets in the micrometer scale has a huge relevance in several fields such a medicine and pharmacy, technological and even food industry. Therefore, the great interest has aroused along the time the research in their production techniques, either for improving existing or developing new ones. The main goal of this work is the experimental study of two main techniques used for this purpose: electrospray and flow focusing. In chapter 2 we have framed this study in a bigger context through a general overview of both techniques and their more relevant applications. Electrospray (ES) is a method for producing jets and droplets atomization reached by the action of an electric field over a liquid which can be injected at a constant flow rate through a metallic capillary (steady regime) or a pendant drop hanging from the upper electrode (unsteady regime). In chapters 3 and 4 we analize scaling laws that govern both regimes, where we show a theoretical development widely validated by experimental results and numerical simulations, for both steady and unsteady regimes. Once all results are showed, in chapter 5, we demonstrate the validity of one-dimensional model for the study of cone-jet mode (steady) of this technique. The flow focusing (FF) technique was proposed by Gañán-Calvo as a method for producing jets and droplets in the micrometer scale by purely hydrodynamic means. This can be reached by a gas stream that coflows with a liquid jet injected through a submilimeter capillary. Both fluids pass through an orifice, also submilimeter, located in front of the capillary, obtaining a jet with a much smaller diameter than that of the capillary and orifice. In the next part of this work variants of the techniques mentioned above are proposed, by changing injector element, replacing the capillary by a common hypodermic needle. In chapter 6, we carry out an experimental study of ``Needle Electrospray'' technique, although the use of hypodermic needles in electrospray is not new, there is no systematic studies that allow us to know the behavior of this method. In the last chapters of this work, we develop a novel technique for producing jets based in FF, where a hypodermic needle will be used and we develop an experimental study of the ``Needle Flow Focusing'' technique (NFF) for liquid-liquid configuration, in chapter 7 and liquid-gas, in chapter 8.