Coffman Chase S, Martínez-Sánchez Manuel, Lozano Paulo C
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev E. 2019 Jun;99(6-1):063108. doi: 10.1103/PhysRevE.99.063108.
Numerical investigations are presented for an ionic liquid meniscus undergoing evaporation of ions in a regime of high electric field. A detailed model is developed to simulate the behavior of a stationary meniscus attached to a liquid feed system. The latter serves as a proxy for commonly utilized electrospray emitters such as needles and capillary tubes. Two solution families are identified for prototype liquid analogous to the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4). The first belongs to a regime of low electric field in which the meniscus is blunt and does not emit charge. The second belongs to a regime of high electric field in which a conelike meniscus produces charge from a sharp tip. Electrohydrodynamic features of the meniscus in this regime are presented. These reveal that the meniscus is Stokesian and hydrostatic and governed by conduction. The applied electric field influences both the shape of the meniscus and the current that it produces while the impedance of the feed system-which must be above a threshold value in order to ensure that the current, and therefore the flow, remains below a maximum value-influences the meniscus current but not the macroscopic shape. In general, this shape deviates from Taylor's idealized cone.
本文针对高电场条件下离子液体弯月面中离子蒸发的情况进行了数值研究。建立了一个详细模型来模拟附着在液体进料系统上的静止弯月面的行为。该液体进料系统可作为针状和毛细管等常用电喷雾发射器的替代物。对于类似于离子液体1-乙基-3-甲基咪唑四氟硼酸盐（EMI-BF4）的原型液体，确定了两类溶液。第一类属于低电场情况，此时弯月面钝圆且不发射电荷。第二类属于高电场情况，此时锥形弯月面从尖锐尖端产生电荷。给出了该情况下弯月面的电流体动力学特征。结果表明，弯月面是斯托克斯型且为静水压力型，由传导作用控制。施加的电场既影响弯月面的形状，也影响其产生的电流，而进料系统的阻抗（必须高于阈值以确保电流以及流量保持在最大值以下）影响弯月面电流，但不影响宏观形状。一般来说，这种形状偏离了泰勒的理想化圆锥。
