一种用于纳米颗粒场致发射推力器的自中和技术

New Self-Neutralization Technology for Nano-Particle Field Extraction Thruster

关键词:  纳米颗粒  反向充电策略  自中和  数值分析

Key words:  Nano particles  Reverse charging strategy  Self-neutralization  Numerical analysis

摘要:

纳米颗粒场致发射推力器（NFET）是一种用于微小卫星的固体工质静电推力器，为促进NFET的工程研制，提出一种新的自中和技术——反向充电中和策略。为研究这种自中和技术的设计方法，建立相应的数值模型以模拟该中和技术下羽流输运过程，并且，在真空舱中开展NFET的羽流测量试验来验证中和模型的正确性。以比色温度计和“打靶法”装置来分别测量羽流温度分布和推力，通过试验与仿真结果的对比，羽流温度变化的试验结果与仿真结果在定性规律上一致，推力的计算误差在9%～10%。在验证模型正确性的基础上，利用该数值模型对关键设计参数进行数值分析。结果表明：引出极与发射极的内径比变化会导致外加电场对剩余电荷颗粒作负功，引起推力下降，该物理参数在0.94附近时，推力达到极大值；而随着颗粒直径的增加，羽流中和区域整体向下游推移，推力升高。本文结论可为NFET的反向充电中和策略提供设计参考。

Abstract:

Nano-particle field extraction thruster is a sort of electrostatic propulsion device with the solid working medium applied on the cube-satellite platform. A new self-neutralization technique has been established to improve the engineering development of NFET, namely the reverse charging strategy for self-neutralization. In order to study the design approach of this neutralization strategy, a relevant numerical model has been investigated to describe the characteristics of the plume transportation. Subsequently, a measurement test of NFET plume in the vacuum tank was conducted to examine the accuracy of the numerical model. The temperature distribution and thrust were measured respectively by the colorimetric thermometer and the target-shooting system. According to the test and calculation results, the temperature solved by the calculation was qualitatively consistent with the test results, and the computational error of the thrust ranged within 9%~10%. After the accuracy of the neutralization model being examined by the test, the key parameters of design were analyzed numerically. The calculation results indicated that, with the ratio of extractor diameter to emitter diameter changing, the applied electric field would exert a negative work on the excess charges and the thrust would decrease, and the thrust would reach the maximum with the ratio of extractor diameter to emitter diameter around at 0.94 while the plume neutralization region would be pushed to downstream and the thrust would increase with the particle diameter increasing. This paper could provide a reference of the optimizing design for the NFET with the reverse charging self-neutralization technique.