Molecular dynamics simulation of ionic liquid electrospray: Revealing the effects of interaction potential models

Abstract

Electrospray thrusters with small size, high precision specific impulse, low power consumption are the most recommended propulsive equipments for micro-nano satellites. Molecular dynamics simulation is able to be used to predict the fundamental physics of electrospray and evaluate the propulsive performance. However, the accuracy of molecular dynamics simulation results critically depends on the accuracy of the interaction potential models used. Therefore, the present paper discusses the effect of different interaction potential models on the molecular dynamics simulations of electrospray thrusters with ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate. The reduced charge all-atoms model, full charge all-atoms model, effective-force coarse-grained model and Merlet coarse-grained model reported in the literature are used for comparison, and comparison is also made to experimental data to elucidate which interaction potential model might be the most realistic. The process of Taylor cone formation, electrospray currents, energy characteristics and velocity distribution are analyzed under varying operating conditions. Our calculations indicate that the reduced charge all-atoms model is the most accurate model for molecular dynamics simulation of electrospray. In contrast, the coarse-grained models fail to reveal the energy characteristics. The full charge all-atoms model is not able to characterize the velocity characteristics. The full charge all-atoms model and coarse-grained models underestimate and overestimate the propulsive performance respectively. It is also found that the energy characteristics and velocity distribution of particles within the Taylor cone are almost unchanged with varying operating conditions.