Ionic liquid electrospray behavior in a hybrid emitter electrospray thruster

Electrospray thrusters are most suitable for micro-nano satellites in advantage of small size, low power consumption and high specific impulse. However, conventional electrospray thrusters with capillary emitters operate at single mode with limited range of thrust. In order to expand range of thrust, novel electrospray thrusters with hybrid emitters which are capable of operating at dual-modes are recommended. Molecular dynamics simulation is used to study the behaviors of the novel electrospray thruster in this work, using EMIM-Tf2N as propellant. Electrospray behaviors for the capillary emitter and the hybrid emitter are compared at the same operating conditions, showing that droplets are more easily emitted from the capillary emitter. For the hybrid emitter, the externally-wetted emission mode is displayed at a low flow rate. Only ions are emitted from the hybrid emitter because of the stronger electric field and larger hydraulic impedance. Meanwhile the change in range of mean diameter and charge to mass ratio of particles are relatively small as compared to the capillary emitter. But the hybrid emitter transits into a capillary emission mode at a high flow rate. Furthermore, analysis of particle charge shows that if there exist particles with charge below the Rayleigh limit, droplets can be produced in electrospray beam.