A brief review of alternative propellants and requirements for pulsed plasma thrusters in micropropulsion applications

Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg. Unfortunately, there is still a lack of suitable efficient micropropulsion systems at these scales. The pulsed plasma thruster is a structurally simple form of electric propulsion. This simplicity also makes it ideally suited for miniaturization. Its history can be traced back to applications in satellites that are much larger than micro/nano-satellites. The vast majority of modern pulsed plasma thrusters use solid polytetrafluoroethylene (PTFE) as a propellant. Unfortunately, at lower discharge energy levels such as those necessitated by the power limitations of micro/nano-satellites, PTFE has a tendency to exhibit carbon deposition, which can ultimately lead to thruster failure. In this new era of small satellites, it is important to consider alternative propellants in the miniaturization of pulsed plasma thrusters. This brief review discusses the needs and limitations of small satellites and alternative propellants that may be able to meet these needs. Such propellants may be able to offer advantages such as a longer thruster lifetime, a higher specific impulse, or a higher thrust-to-power ratio. This would enable the development of different types of pulsed plasma thrusters that can be tailored towards specific mission requirements.     

10 cm ECR中和器性能优化实验研究

针对电子回旋共振(ECR)中和器性能无法满足实际应用需求的问题，开展了10 cm ECR中和器的性能优化实验研究，在分析现有ECR中和器内部结构的基础上，提出新的结构改进方案。通过改进ECR中和器的电子束流引出对比实验，得到了中和器结构对束流引出性能的影响规律。优化后的ECR中和器性能实验表明：相同条件下ECR中和器束流引出大小与气体流量大小不成正相关，但随着微波功率的增加而增加。性能实验得到的中和器最佳工作和性能参数为：微波功率为10 W、氙气流量为0.5 sccm，收集板间距为5 mm时，在50 V引出电压条件下能够引出127 mA的电子束流。     

临近空间高超声速飞行器黑障问题研究综述

首先对国内外黑障问题研究历史进行了回顾,然后从等离子体鞘套形成机理和基本特征、电波传播机理及信道特征等方面阐述了高超声速飞行器黑障问题的成因。随后,着重介绍了等离子体流场和电波传播数值模拟方法并分析了方法的适用性。进一步对等离子体地面模拟方法和诊断技术进行了概述,并对国内外地面黑障实验结果进行了详细分析。在此基础上,针对临近空间高超声速飞行器的特点,采用层次分析法(AHP)对现有黑障消除技术进行了评估,给出了目前工程实用方法、近期可能实现的工程实用解以及未来具有应用潜力的消除技术。最后,对黑障问题后续研究方向提出了几点建议。     

钛合金表面等离子喷涂ZrO2—NiCoCrAlY梯度涂层的抗热震行为

ＺｒＯ２－ＮｉＣｏＣｒＡｌＹ梯度涂层的成分沿厚度方向呈连续梯度化分布，提高了涂层与基体的粘结强度和涂层的内聚强度，其抗热震性能优于双层涂层。在较大热冲击应力作用下，梯度涂层整体自基体表面剥落而失效；在较小热冲击应力作用下，由于ＮｉＣｏＣｒＡｌＹ底层与ＴＣ４合金基体发生了热相互作用，改善了涂层与基体的结合状况，梯度涂层纵向断裂并部分自基体表面剥落而失效。     

Supersonic Two-Dimensional Minimum Length Nozzle Design at High Temperature. Application for Air

When the stagnation temperature of a perfect gas increases, the specific heat ratio does not remain constant any more, and start to vary with this temperature. The gas remains perfect, its state equation remains always valid, except it will name in more calorically im-perfect gas or gas at High Temperature. The goal of this work is to trace the profiles of the supersonic Minimum Length Nozzle with centered expansion when the stagnation temperature is taken into account, lower than the threshold of dissociation of the molecules and to have for each exit Mach number several nozzles shapes by changing the value of the temperature. The method of characteristics is used with a new form of the Prandtl Meyer function at high temperature. The resolution of the obtained equations is done by the second order of finite differences method by using the predictor corrector algorithm. A study on the error given by the perfect gas model com-pared to our model is presented. The comparison is made with a calorically perfect gas for goal to give a limit of application of this model. The application is for the air.     

Numerical design optimization of compressor blade based on ADOP

An aerodynamic design optimization platform(ADOP) has been developed.The numerical optimization method is based on genetic algorithm(GA),Pareto ranking and fitness sharing technique.The platform was used for design optimization of the stator of an advanced transonic stage to seek high adiabatic efficiency.The compressor stage efficiency is increased by 0.502% at optimal point and the stall margin is enlarged by nearly 1.0% at design rotating speed.The flow fields of the transonic stage were simulated with FINE/Turbo software package.The optimization result indicates that the optimization platform is effective in3Dnumerical design optimization problems.      

氢气添加对RP-3航空煤油燃烧特性的影响

为了阐明氢气添加对国产RP-3航空煤油燃烧特性的影响,在定容燃烧反应器中实验测量了初始压力为0.1MPa、初始温度分别为390,420K、当量比范围为0.8～1.5时RP-3航空煤油/氢气混合气的层流燃烧速度与马克斯坦长度,分析了掺氢比对火焰发展结构、层流燃烧速度及马克斯坦长度的影响.结果表明:随着掺氢比的提高,在火焰发展过程中,火焰前锋面逐渐出现裂纹或褶皱,火焰的不稳定性逐渐增强;随着混合气当量比或掺氢比的升高,RP-3航空煤油/氢气混合气的马克斯坦长度逐渐减小;当混合气当量比从0.8升高至1.5时,RP-3航空煤油/氢气混合气的层流燃烧速度呈现先增加后降低的趋势,当量比为1.2时混合气的层流燃烧速度达到最大;同时,随着初始温度或掺氢比的升高,RP-3航空煤油/氢气混合气的层流燃烧速度逐渐升高。      

航空发动机外部管路调频方法研究

为了使航空发动机外部管路调频工作简化和效率提高,运用有限元方法、通过计算机仿真,对航空发动机外部管路模态进行计算分析,得到了卡箍约束位置对外部管路1阶固有频率的影响规律;引入管路等效长度和等效系数的概念,总结得到典型结构管路的管长等效系数值;综合卡箍约束位置对外部管路固有频率的影响规律、典型管路结构的管长等效系数和工程实际经验,归纳得到管路调频的一般工作步骤,用于指导管路调频工作,显著地提高了管路调频工作效率。     

一种基于需求工程思想的民用飞机需求确认方法

依据民用飞机在产品开发过程中需求如何确认的现实需求,定义了一种基于需求工程思想的民用飞机需求确认的方法。该方法一方面引入了需求工程的思想,一方面在不破坏原有设计要素的前提下,同时利用设计方案作为两者沟通、融合的载体,有效实现了“需求是牵引,设计是根本”的现代民机产品开发理念。该方法和流程在民机型号的概念设计工作中得到应用,取得了较好的实践效果。为了能够对相关的工程设计工作提供可参考和借鉴的经验,以飞机起飞场长为例,对该需求的确认过程进行了详细剖析,进一步阐述这种设计方法的关键点和核心思想。     

EUV observation from the Earth-orbiting satellite,EXCEED

An Earth-orbiting small satellite “EXtreme ultraviolet spectrosCope for ExosphEric Dynamics” (EXCEED) which will be launched in 2012 is under development. The mission will carry out spectroscopic and imaging observation of EUV (Extreme Ultraviolet: 60–145 nm) emissions from tenuous plasmas around the planets (Venus, Mars, Mercury, and Jupiter). It is essential for EUV observation to put on an observing site outside the Earth’s atmosphere to avoid the absorption. It is also essential that the detection efficiency must be very high in order to catch the faint signals from those targets. In this mission, we employ cesium iodide coated microchannel plate as a 2 dimensional photon counting devise which shows 1.5–50 times higher quantum detection efficiency comparing with the bared one. We coat the surface of the grating and entrance mirror with silicon carbides by the chemical vapor deposition method in order to archive the high diffraction efficiency and reflectivity. The whole spectrometer is shielded by the 2 mm thick stainless steel to prevent the contamination caused by the high energy electrons from the inner radiation belt. In this paper, we will introduce the mission overview, its instrument, and their performance.