100W级小功率电弧推力器性能研究

卫星小型化的应用发展对其在轨精确定位的推进技术提出了迫切需求。目前应用于空间微推进技术的主要还是冷气推进和电阻加热推进,其中主要的原因是,很多先进的推进技术虽然可能产生较高的比冲,却很难保证运行性能的稳定性和可控性,或者推力器的体积和重量难以减小到适用于微小卫星,或者系统复杂,以及使用的电源与卫星供电系统兼容性差,等等。然而不管是冷气推进还是电阻加热推进,都存在比冲低的不足,同样的任务需要携带更大量的气体以及气体贮存装置,降低有效载荷。电弧等离子体推力器具有结构简单,工作电压低,容易与卫星供电系统协调、推力功率比高,在技术实现难度及可靠性等方面具有一定优势,也正是由于这些特点,以肼为推进剂的千瓦级电弧加热推力器在国外大、中型卫星,特别是用于通讯和监测等用途的地球同步轨道卫星上,得到了较为大量的应用[1]。由于小卫星通常难以提供中低功率电弧推力器所需的较大输入电功率需求,因此100 W(甚至几瓦)以下稳定工作的Arcjet近年来得到了广泛关注。本文在实验室已有工作的基础上,自行研制了小功率的电弧推力器。推力器阳极喷管的喉道直径为0.3mm,喉道与阳极喷管出口的面积比为200,阳极喷管的扩张半角为20°。实验所用真空室的极限真空可达1×10-4Pa,推力器工作时的最大腔压小于0.8Pa。在气流量100~600 m L/min、工作电流80-180 m A的范围内实现了以氩气、氮气和氨气为推进剂的电弧推力器的持续稳定放电;采用测量冲击力的间接测力方法[2],系统测量了推力器在不同工作参数条件下的推力数据,结合弧电流、弧电压的测量数据,导出了对应条件下推力器的比冲和推力效率,并对推力器性能进行了分析。结果显示,在相同的气流量、工作电流条件下,推进剂为氨气时得到的比冲最大,最大比冲超过300s。三种推进剂条件下获得的弧电压都远高于1k W级电弧加热推力器的电压值。在氮气和氨气条件下,弧电压随气流量的增加先减小而后增大,呈现出不同于1k W级电弧加热推力器的复杂放电特性

直流减压层流氩等离子体射流的温度测量

在低于大气压条件下产生的减压热等离子体射流仍然具有较高的温度和能流密度,已经有几十年的材料工艺应用历史,但是对减压热等离子体射流的参数诊断、特别是对其可能偏离局域热力学平衡的特性研究还远未深入和系统。本文采用玻尔兹曼图表法及双静电探针方法,对以纯氩为工质的减压层流热等离子体射流的激发温度及电子温度进行了测量

Plasma and electrode emissions from a 1 kW hydrogen-nitrogen arcjet thruster

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures

Raman Spectroelectrochemical Study on Bioactive Molecules

本文概述了采用电化学现场拉曼光谱技术研究氧化物歧化酶在L 半胱氨酸修饰金电极表面的电子迁移反应以及腺嘌呤共存条件下超氧化物歧化酶在金电极表面的电子迁移反应和不同电位下银电极表面烟酰胺腺嘌呤二核苷酸的吸附等体系的反应吸附特性 .所得结果对于分析和研究生物活性分子电化学过程机理具有重要意义 .Electron?transfer reaction is known to be one of the key reactions for generating biological functions. Mechanism revelation at a molecular level of such kind reactions is to be very helpful for us to understand life essence. In fact, surface enhanced Raman scattering (SERS) is one of the most powerful tools for the study on metal?electrolyte and metal?vacuum interfaces since 1970's. Moreover, Raman spectroscopic study in enzymology has provided attractive results during last twenty?five years. For the study of electron?transfer reaction mechanism of some oxidoreductases and SERS of some other biological macromolecules, an electrochemical in situ Raman spectroscopic technique was established in author's lab and some research works have been done on it in the past two years. A brief review of these works is given in this paper. The electrochemical in situ Raman spectroscopic measurements were carried out using a Super LABRAM Raman spectrometer (Dilor, France) coupled with a CHI604A Electrochemical Analyzer (CH Instr., USA). A Teflon spectroelectrochemical cell with a quartz plate window was designed for the in situ measurements. The working electrode was pretreated with oxidation?reduction cycles for each measurement. The electrolyte solutions were purged with nitrogen prior to all measurements, and all the measurements were carried out under the nitrogen atmosphere. Copper, zinc superoxide dismutase (SOD) is an important oxidoreductase for organism metabolism. The established spectroelectrochemical technique was first used to characterize the cyclic voltammetric process of SOD at L?cysteine modified gold electrode as well as the process of electrochemical modification of L?cysteine molecules on a gold electrode. The obtained Raman spectra reveal that the L?cysteine modified gold electrode improves effectively the reversibility of electron?transfer reactions of SOD. Besides L?cysteine molecules, it was interesting that adenine was also an effective electron?transfer promoter for SOD at gold electrode. A strong peak at 355 cm -1 can be observed in the Raman spectrum of adenine molecules adsorbed on gold electrode. It was inferred that the peak maybe related to the chemical interaction between adenine molecules adsorbed and gold electrode surface. As shown in Fig.1, for the mixture of SOD and adenine at gold electrode under a polarization potential 55 mV (vs. SCE), both the characteristic Raman lines of SOD and adenine molecules appeared. Therefore it was reasonable to conclude that SOD and adenine molecules should be co?adsorbed on gold electrode surface under such a potential, which is slightly lower than the reduction peak potential of SOD on adenine?modified gold electrode. Moreover, two new peaks appeared remarkably at 445 cm -1 and 610 cm -1 are likely to be related to the active site of SOD. It suggests that the co?adsorption mechanism of SOD and adenine molecules on the gold electrode surface results in effective approaching of the active site of SOD to the electrode surface.作者联系地址：上海师范大学化学系!上海200234,上海师范大学化学系!上海200234,上海师范大学化学系!上海200234,上海师范大学化学系!上海200234,上海师范大学化学系!上海200234,上海师范大学化学系!上海200234Author's Address: Dept. of Chem., Shanghai Teachers Univ., Shanghai 200234,Chin

直流纯氩层流等离子体射流的长度变化

采用主要由阴极、阳极以及介于阴极和阳极之间的中间段组成的直流非转移式电弧等离子体发生器,在大气压条件下,比较系统地研究了纯氩层流等离子体射流的长度随着弧电流、气体流量以及发生器结构而变化的规律.结果表明:层流射流的长度随弧电流和工作气流量的增加而增长;层流向湍流流动转变的临界气流量值随弧电流增大而提高;在发生器的伏安特性呈大梯度变化的情况下,射流长度随弧电流的变化幅度增大

层/湍流等离子体射流波动特性实验研究

本文应用电压传感器、光电倍增管及水冷皮托管,对产生射入空气中的纯氩层流和湍流等离子体射流的弧电压波动、发生器出口处的射流光强波动以及沿射流轴线的滞止压力进行了测量.测量结果显示层流等离子体射流各参数的波动幅度远小于湍流射流的对应值;弧电压的波动幅度随气流量的变化明显,但随电流的变化很小;弧电压的波动幅度与其平均值之比随电流增加呈下降的趋势

Temperature measurements in a laminar plasma jet generated at reduced pressure

Double electrostatic probe method and Boltzmann-plot method are applied to measure the electron temperature and the excitation temperature of a DC laminar argon plasma jet generated at reduced pressure. Attempts are also made to measure the gas temperature by using a pair of WRe-5/26 thermocouple. Experimental results show that the measured excitation temperature at the jet center increases with the vacuum chamber pressure and the arc current, but is appreciably lower than the measured electron temperature, indicating that the plasma jet under study is evidently deviated from the LTE state. The temperature indicated by the thermocouple probe is much lower than the measured excitation temperature and electron temperature. Theoretical analysis shows that the thermocouple method intended for gas temperature measurement contains very large errors due to rarefied-gas heat transfer effects, and thus is unsuitable for this purpose