The current analysis of electrospray process on a single emitter with ionic liquid for micro propulsion

The ionic liquid electrospray thruster is one of the most promising candidates of micro propulsion which is in urgent need with the rapid development of micro/nano satellites. The current characteristics of a single emitter are important to understand the ionic liquid electrospray which promotes the improvement of thruster performance. A porous nickel emitter was tested with 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄]) to fully obtain the current characteristics responded to square-wave voltage. The voltage-current characteristics, the pulsation characteristic and the onset delay were investigated to further understand the electrospray with a passively supplied emitter. The results shown that the voltage-current relationship was neither linear nor exponential. The pulsation characteristics in intermittent regime shown great difference with reported modes. A flow impedance model for porous emitter was derived to compute the viscous drag coefficient, so that the onset delay time can be predicted. The experimental results were located within the theoretical band by varying the radius of curvature. The flow impedance and viscous drag coefficient were sensitive to radius of curvature, which shown that the dynamics response will be greatly affected by tip geometry. All these results are worthwhile to understand the ionic liquid electrospray and operate ionic liquid electrospray thruster in suitable operating conditions.