Abstract
A stable capillary liquid jet formed by an electric field is an important physical phenomenon for formation of controllable small droplets, power generation and chemical reactions, printing and patterning, and chemical-biological investigations. In electrohydrodynamics, the well-known Taylor cone-jet has a stability margin within a certain range of the liquid flow rate (Q) and the applied voltage (V). Here, we introduce a simple mechanism to greatly extend the Taylor cone-jet stability margin and produce a very high throughput. For an ethanol cone-jet emitting from a simple nozzle, the stability margin is obtained within 1 kV for low flow rates, decaying with flow rate up to 2 ml/h. By installing a hemispherical cap above the nozzle, we demonstrate that the stability margin could increase to 5 kV for low flow rates, decaying to zero for a maximum flow rate of 65 ml/h. The governing borders of stability margins are discussed and obtained for three other liquids: methanol, 1-propanol and 1-butanol. For a gravity-directed nozzle, the produced cone-jet is more stable against perturbations and the axis of the spray remains in the same direction through the whole stability margin, unlike the cone-jet of conventional simple nozzles.
Highlights
Rayleigh proposed a theory on a spherical liquid droplet subjected to an electric field for the first time showing that the spherical shape could not stay stable beyond a threshold of electric potential difference[1]
Stability of the cone-jet is crucial for combustion of liquid fuels in small scales[8,20,23], while in meso/micro scales it is important to produce very fine droplets but sufficiently large mass flow rates
We will discuss the characteristics of the cone-jet stability island for a conventional simple nozzle configuration and the effect of the extender cap in more details
Summary
Taylor Cone-jet in Electrohydrodynamics received: 23 August 2016 accepted: 25 October 2016 Published: 05 December 2016. The well-known Taylor cone-jet has a stability margin within a certain range of the liquid flow rate (Q) and the applied voltage (V). The range of voltage which may lead to a stable cone-jet structure depends on nozzle geometry, electrodes configuration, flow rate, and liquid properties especially conductivity and surface tension. We discuss the governing physical mechanism and introduce a novel yet simple emitter in order to enhance stability of the cone-jet mode for a wide range of flow rates and applied voltages. This extension in flow rates is provided by adding a small part, called the “extender cap” hereafter, to the conventional simple nozzle. It is observed that the cone-jet formed with the extender cap is much more stable compared to the simple nozzle when both of them operate at the same flow rate
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