射频离子推力器放电室结构优化研究

Structure Optimization of Discharge Chamber in Radio-Frequency Ion Thruster

射频离子推力器因结构简单、推力精确可调、工作寿命长等因素,已被广泛应用于航天领域,其中放电室的离子密度是决定推力性能的关键性要素。本文基于电感耦合放电过程建立了二维轴对称流体模型,分别研究了放电室在不同长径比和不同结构等条件下的离子密度变化规律。结果表明:增大射频功率和气压可以提升离子密度,放电室长度在3.5-4 cm时离子密度较高。在放电室直径相同条件下,模型1圆柱结构与模型2圆台结构体积保持一致,减小表面积可以提升离子密度;模型3球壳结构、模型4球壳圆柱结构与模型1圆柱结构的总长度一致,最优的复合结构模型4与单一圆柱结构模型1相比,离子密度提高18.2%,若两者密度相等时,最优的复合结构模型4可以节省15%功率输入或降低10%放电室内气压。

Radio-frequency ion thruster has been widely used in aerospace field because of its simple structure,precise and adjustable thrust and long working life.The ion density of discharge chamber is the key factor of the thruster performance.Based on the process of inductively coupled discharge,a two-dimensional axisymmetric fluid model is established.The variation of ion density in the discharge chamber under different aspect ratios and different structures are studied respectively.The results show that increasing the RF power and pressure can increase the ion density.The ion density is higher when the length of discharge chamber is 3.5-4 cm.Under the same diameter of the discharge chamber,Model 1 of cylindrical structure and Model 2 of frustum structure have the same volume.Reducing the surface area can improve the ion density.Model 3 of calotte structure,Model 4 of calotte-cylindrical structure and Model 1 of cylindrical structure have the same total length.Compared with the single cylindrical structure in Model 1,the optimal composite structure Model 4 has an ion density increase of 18.2%.When their densities are equal,Model 4 saves 15%of power input and 10%of pressure in the discharge chamber.