Dynamics of electrified jets in electrohydrodynamic atomization

Abstract

An electrified jet ejected from a meniscus (or Taylor cone) can further disintegrate into fine drops with different modes in electrohydrodynamic atomization (EHDA). This process has been applied into many fields because of controllable production of highly charged and monodispersed drops. However, both stable and unstable electrified jets are encountered in EHDA, usually depending on liquid physical properties and operating parameters. A series of electrified jets are visualized and the transient breakup dynamics are analyzed within an electric field. According to the geometry forms of drops or/and jets emitted from the end of a needle, periodic dripping, pulsating-jet, stable-jet, and unstable jet are clearly classified. The operating parameters versus spraying modes are also discussed, especially for propylene glycol and n-octanol. The initial velocity from the Taylor cone, jet breakup length, jet position, and the size separation effect are deeply studied. The jet velocity is significantly accelerated by electric stresses and good agreement with predicted value. The jet breakup length increases sharply as liquid flow rate increasing and slowly increases as electric potential increasing, except for small liquid flow rate where bullet cone occurs. The jet ejection point varies and gradually deflects off needle axis with an increase in electric potential. The ‘size separation effect’ can help improve the quality of printing by removed highly charged satellite drops.