Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process,a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 k W operation mode.Meanwhile,the fluid simulation method and particle-in-cell-Monte Carlo collision(PICMCC) method are adopted to simulate the ion extraction process according to the previous test results.The numerical calculation results are verified by the ion thruster performance test.The results show that after about 1.2 h operation,the hot gap between the screen grid and the accelerator grid reduce to 0.25–0.3 mm,while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium,and the hot gap is almost unchanged.In addition,the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value.Fluid simulation results show that the plasma density of the screen grid is in the range 6?×10~(17)–6?×?10~(18) m~(13) and displays a parabolic characteristic,while the electron temperature gradually increases along the axial direction.The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant.Meanwhile,the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap.The ion beam current has optimal perveance status without thermal deformation,and the intercepted current of the accelerator grid and the decelerator grid are 3.65 m A and 6.26 m A,respectively.Furthermore,under the effect of thermal deformation,the ion beam current has over-perveance status,and the intercepted current of the accelerator grid and the decelerator grid are 10.46 m A and 18.24 m A,respectively.Performance test results indicate that the breakdown times increase obviously.The intercepted current of the accelerator grid and the decelerator grid increases to 13 m A and 16.5 m A,respectively,due to the change in the hot gap after 1.5 h operation.The numerical calculation results are well consistent with performance test results,and the error comes mainly from the test uncertainty of the hot gap.     

Numerical research of a 2D axial symmetry hybrid model for the radio-frequency ion thruster

Since the high efficiency discharge is critical to the radio-frequency ion thruster (RIT),a 2D axial symmetry hybrid model has been developed to study the plasma evolution of RIT.The fluid method and the drift energy correction of the electron energy distribution function (EEDF) are applied to the analysis of the RIT discharge.In the meantime,the PIC-MCC method is used to investigate the ion beam current extraction character for the plasma plume region.The beam current simulation results,with the hybrid model,agree well with the experimental results,and the error is lower than 11％,which shows the validity of the model.The further study shows there is an optimal ratio for the radio-frequency (RF) power and the beam current extraction power under the fixed RIT configuration.And the beam extraction efficiency will decrease when the discharge efficiency beyond a certain threshold (about 87 W).As the input parameters of the hybrid model are all the design values,it can be directly used to the optimum design for other kinds of RITs and radio-frequency ion sources.     

序言

经过近五十年的发展,我国的空间电推进技术呈现出了百花齐放、千帆竞渡、万众瞩目的繁荣 景象,传统技术与创新技术并驾齐驱,产品研制与型号应用成果累累,技术效益和经济效益交相辉 映.新时代的号角已经吹响,踏上航天强国建设新征程,我国空间电推进技术正在迎来一个前所未有的蓬勃发展新时期.     

基于Web的工艺知识资源服务与管理系统

在分析了当今制造企业对工艺知识资源服务与管理的迫切需求的基础上，提出了基于Web的工艺知识资源服务与管理系统，该系统面向企业内部网（Intranet），包括前台工艺知识资源服务系统和后台工艺知识资源管理系统两部分，前台系统为制造企业内部人员提供知识检索服务，后台系统作为工艺知识管理工具和前台的动态维护工具，文中介绍了系统的结构和功能以及关键实现技术。     

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给出了概念设计方案性能的模糊标度方法;从价值工程原理出发,通过将数据包络分析(DEA)模型推广到模糊环境之中,提出了一种机械设计概念方案评估的新方法,通过实例应用,验证了该方法的可行性。     

LIPS-300多模式离子推力器中和器优化研究

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基于因子分析的汽车组合开关力特性评价方法研究

为克服主观评价的模糊性,确保组合开关力特性评价结果客观、科学、合理,在统计分析的基础上提出一种新的评价方法。确立了汽车转向组合开关力特性的6项评价指标;通过因子分析对转向组合开关的指标体系进行归类和分层,并根据主因子对总目标的贡献率及因子得分系数确定了各级指标的权重值。     

汽车用组合开关性能试验台的控制系统

介绍一种汽车组合开关综合性能试验台的控制系统。该试验台控制系统采用PC机为其控制主机,步进电机驱动,具有在线测量组合开关实际力特性的功能。通过C＋＋Builder语言编程,应用API函数实现计算机与试验台整机系统的接口,从而实现了计算机对整个系统的控制。     

电子设备电磁干扰的产生及抑制

阐述了电子设备中电磁兼容问题的重要性,通过对电磁干扰产生的根源及途径的分析,介绍了几种抑制电磁干扰的方法及电磁干扰抑制在实际中的应用.     

基于T5离子推力器无拖曳飞行技术

GOCE是世界上首次应用无拖曳飞行技术的科学测量卫星,用于测量地球重力场和稳态海洋环流.大气阻尼补偿系统是实现无拖曳飞行的重要技术支撑,其核心单元是T5 离子推力器.基于T5 离子推力器无拖曳飞行,论述了从入轨测试到执行任务的技术特点、运行及性能.并对T5 离子推力器在大气阻尼补偿系统中的应用做了总结,提出了离子推力器发展应用的建议.