We experimentally evaluated the influence of an electric field on a liquid micro-jet, emerging vertically from a gas dynamic virtual nozzle. The liquids used included purified water, saline solution, ethylene glycol, isopropanol and ethanol at liquid flow rates of 0.1 – 4.0 ml/min and air flow rates of 10 – 80 l/h. An electrode, operated at voltages 2 – 8 kV was positioned 10 mm bellow the nozzle. Flow types (dripping, jetting, whipping and their combinations) and jet diameters were analysed. For all process parameter combinations flow type diagrams were constructed and differed markedly between liquids. Measurements showed the electric field stabilising jets at gas flow rates ~25 l/h, whereas at flow rates ~65 l/h it accelerated jet breakup. Analysis of ethylene glycol jets with diameters between 132 – 430 µm demonstrated thinning to 50 % at ~6000 V and thickening to 115 % at ~2000V, with a thinning prevalent downstream and thickening closer to the nozzle. We identified a previously unreported flow type, in which an ethanol jet transformed into a liquid sheet at ~8000 V and at gas and liquid flow rates of 0 – 40 l/h and 1 – 3 ml/min, respectively. Research findings are important for sample delivery in serial crystallography.
|
