Molecular dynamics simulation of evaporation of electrified liquid in electrospray.

The micro thruster based on electrospray is currently one of most widely used electric propulsion technologies for micro-nano satellites due to excellent advantages of long acceleration time, no energy loss and zero chemical fuel pollution. However, in outer space, the fluctuation of ambient temperature directly affects the behavior of electrospray and its accuracy of thrusters. Therefore, it is necessary to explore the influence of temperature on electrospray process, where atomization morphology, drops or/and ions distribution and intermolecular interactions need to be clarified in detail. In present study, electrospray evaporation ions behaviors of ethanol and diethylene glycol were numerically studied at various ambient temperatures utilizing molecular dynamics (MD) method. The atomization morphology of two typical liquids under various electric field strengths is compared. Diethylene glycol requires a higher electric field strength to form a stable jet than ethanol. The jet firstly breaks up into main droplets and further disintegrate into progeny small droplets. As the ambient temperature increases, the ethanol main jet gradually becomes slender and changes from single-cluster cone jet to ramified jet, finally becomes multiple jet. The tip of ethanol jet emerges unstable behavior with the temperature increasing. Owing to the differences in physical properties between ethanol and diethylene glycol, the ionization/fission of ethanol is greater than that of diethylene glycol. When the temperature approaches the boiling point, the diethylene glycol jet rapidly bursts into irregular droplets maybe caused by ramified instability. The increase in temperature could accelerate evaporation rate and molecular thermal movement, the hydrogen bonds formed between molecules break more easily, while the interactions between molecules significantly reduce. The conclusion of present work may provide direct insight into the micro mechanism of electrospray evaporation behavior. • The cone-jet, ramified-jet and multi-jet sequentially appear as ambient temperature increasing. • The ionization of charged liquids is enhanced as ambient temperature increasing due to the stretching of bonds violent. • The hydrogen bonds between molecules break up more easily because of acceleration of evaporation rate and molecular thermal movement owing to an increase in temperature. • The ionization of ethanol is stronger than that of diethylene glycol because of the difference of density and viscosity. • Diethylene glycol requires a higher electric field to overcome the surface tension to form a stable jet. [ABSTRACT FROM AUTHOR]