The ionic liquid electrospray-based propulsion system is one of the most promising candidates for space micro-propulsion, which is in urgent need with the rapid development of micro/nano satellites. The current mode in the electrospray process directly dominates the performance of ionic liquid electric thruster. Hence, in order to study the general current modes of ionic liquid electrospray, a series of experiments have been conducted with a coned porous nickel emitter. With the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as propellant, both the time-varying voltage-current curves and corresponding optical images of the electrospray process are obtained. Firstly, based on the voltage-current curves and optical images, the classification of current mode was discussed, which showed that the current is a result of basic-mode composition in time and space and the mode transition is dominated by the electric field strength. Secondly, the liquid flow at the tip of coned porous emitter was studied based on the images, which is found to be a combination of porous media flow and liquid film flow influenced by the electric field. The projected area of meniscus can be much larger than the pore size, which indicates that the emission can span several pores in our system. As the electric voltage increases, the size of meniscus decreases and three-site emission is optically captured, which explains the spatial composition of the current mode. Finally, the onset delay is calculated from the time-varying current curves. Based on the observation that the meniscus size is variable, an onset delay model is developed, whose prediction agrees well with the experimental results. Since a single emitter is a basic element for array porous emitters, this work is valuable to the design of efficient ionic liquid electric thruster.

基于离子液体电喷雾的推进系统是空间微推进的最有希望的候选者之一，随着微型/纳米卫星的快速发展，迫切需要该系统。电喷雾过程中的电流模式直接控制着离子液体电动推进器的性能。因此，为了研究离子液体电喷雾的一般电流模式，已使用锥形多孔镍发射极进行了一系列实验。用离子液体1-乙基-3-甲基咪唑鎓四氟硼酸盐作为推进剂，可以获得电喷雾过程的时变电压-电流曲线和相应的光学图像。首先，基于电压-电流曲线和光学图像，讨论了电流模式的分类，这表明电流是时间和空间中基本模式组成的结果，而模式转换主要由电场强度决定。其次，基于图像研究了锥形多孔发射器尖端的液体流动，发现该流动是受电场影响的多孔介质流动和液膜流动的结合。弯月面的投影面积可能比孔径大得多，这表明发射可以跨越我们系统中的多个孔。随着电压的增加，弯月面的大小减小，并且光学捕获了三点发射，这解释了电流模式的空间组成。最后，根据时变电流曲线计算出启动延迟。基于弯液面大小可变的观察，建立了发作延迟模型，其预测与实验结果吻合得很好。由于单个发射器是阵列多孔发射器的基本元件，因此这项工作对高效离子液体电动推进器的设计很有价值。