碲化铋基温差发电模块输出功率优化试验研究

同位素温差发电器在深空探测活动中具有广泛的应用背景。为优选温差发电模块构型、提高输出功率,制备了具有不同热电元件厚度的碲化铋基温差发电模块;并通过建立的试验测试系统,测量了不同温差条件下发电模块的输出功率和匹配负载随热电元件厚度的变化。试验结果表明,在所研究的热电元件厚度范围内,随着热电元件厚度的减小,模块的输出功率呈线性增大趋势,而匹配负载则呈线性减小趋势。在热源温度478 K、热沉温度300 K的条件下,测得热电元件厚度为1.0 mm的模块的最大输出功率达到约8.2 W,最大功率面积比约为0.52 W·cm-2。     

温差发电器工作特性的数值研究

考虑温差材料的塞贝克效应及电流的珀耳帖效应,与传热方程相结合,建立了温差发电器的一维计算模型,数值模拟了温差发电器的热电耦合工作过程。分析了温差发电器的热环境、回路中负载电阻值等参数及温差电单体对的连接方式对发电器工作性能的影响。研究结果表明,提高温差发电器热端的加热热流或增加冷端的换热系数均能提高发电器的输出功率及热电转换效率,但两者的影响趋势不同;供电回路的负载电阻对发电器温差电元件的温度分布有明显的影响,并可导致发电器最大输出功率的状态点发生漂移;温差电单体对不同连接方式对发电器性能有明显的影响。     

重复频率脉冲激光辐照下光学薄膜元件 温升的有限元分析

文章采用有限元ANSYS程序分析了在重复频率脉冲激光辐照下光学薄膜元件表面的温度变化。结果表明激光脉宽相同时,重复频率越高,相同辐照时间薄膜元件表面温度累积就越大;占空比一样时,脉宽越大,相同辐照时间元件温升越高。重复频率表现出来的只是温度的累积效果,脉宽的影响效果远大于重复频率引起的温度累积。     

激光辐照条件下光电电池温度特性的实验研究

激光输能具有广阔应用前景,而光电电池是激光输能技术中实现光-电转换的核心部件。文章围绕温度对光电电池输出性能的影响,通过建立电池输出性能实验测试系统,研究了一定激光功率密度下砷化镓电池和硅电池在不同温度下的伏安特性,以及开路电压、短路电流、最大输出功率、匹配负载、转换效率、填充因子随电池温度的变化规律,并给出其定量表达式,可为激光输能条件下光电电池的选择以及光电电池温度特性预测提供参考。     

焊锡对热电偶测温误差影响分析

航天器真空热试验中为了消除焊锡可能带来的温差热电势,文章采用Keithley 2750数据测量系统,通过比较法对焊锡与铜、焊锡与康铜之间的温差热电势进行了测试分析。标准热电偶选择铜-康铜热电偶,测试温度范围为-195～+75℃。测试时,热电偶冷端为冰水混合物,热端为液氮浸泡过的不锈钢圆柱体或热水瓶。为了确保回路中的焊点处于相同的热环境条件,可采用多层隔热组件进行包覆,避免接插件直接接触热沉。     

月面巡视探测器太阳帆板热电耦合仿真计算

文章建立了月面巡视探测器太阳帆板热电耦合计算模型,制定了太阳帆板的对日定向方案和输出电能分配方案。通过数值模拟获得了月面白昼期间太阳帆板的温度及电能输出,分析了太阳帆板背面包覆隔热材料前后及帆板是否对日定向的计算结果。计算表明:当帆板不对日定向时,其背面包覆隔热材料对其温度及电能输出无明显影响;对日定向时,帆板温度随时间的分布规律发生了明显改变,此时帆板背面包覆隔热材料使其温度明显上升,但帆板正面与背面的温差减小。     

STP热光伏发电的方案设计与性能分析

结合STP (Solar thermal Propulsion)高温吸热芯的技术特点,采用二次分光膜,对STP热辐射光伏发电(TPV)系统进行了结构设计和性能计算。通过优化分析,得到使太阳电池工作温度在额定值附近的氢冷却剂入口参数和通道尺寸数据。计算结果表明,当吸热芯温度为2400K时,光伏电池组件的输出功率在50~100W之间;通过调节电池组件的串并联电池数量,可以获得期望的输出特性。结论为STP的热光伏发电系统的设计研究提供参考依据。
     

燃烧供热热光伏系统实验研究

针对未来深空探测供电需求,设计了一套热光伏发电系统,采用丙烷燃烧器模拟同位素热源,并利用低禁带GaSb电池实现了系统的热电转换。研究了气体流量、过量空气系数、回热器性能、滤波器等对辐射器温度及电池输出功率、系统转换效率的影响。结果表明：电池输出功率随燃气量单调增加,而在一定燃气量下,存在一最优过量空气系数使其达到最大值;同时,回热器和滤波器对辐射器温度和电池输出特性有很大影响;本实验系统可以实现最大输出功率密度0.45W/cm 2,系统转换效率2.8%。     

兆瓦级探月火箭空间核电源系统设计与性能研究

针对目前空间核电源在深空探测领域功率不足的问题，结合热离子热电转换空间核电源和碱金属热电转换空间核电源的发电方式，提出一种新型空间核电源。计算堆芯有效增殖因子、功率峰值因子、冷却剂空泡系数和停堆深度等安全性参数，并通过分析接收极功函数和碱金属热电转换系统电流密度等性能参数。之后，对比耦合发电系统与原热离子热电转换空间核电源和碱金属热电转换空间核电源的效率，发现新型耦合发电系统发电效率分别较另两种发电系统提高约6％和约10％。最后建立动态模型进行分析，确保核电源可以稳定运行，为大功率核电源设计提供理论依据。     

L波段高效小尺寸功率放大器载片设计

为了应对当前市场对功率器件更低成本、更小尺寸和更优性能的要求，设计了一款工作频率为1.2～1.4GHz的高效率小尺寸氮化镓（gallium nitride,GaN）基功率放大器载片。使用有源时域负载牵引系统对GaN管芯进行在片测试并提取管芯的非线性行为模型，在先进设计系统（advanced design system,ADS）软件中利用模型进行阻抗匹配电路设计和仿真，将功率放大器端口匹配到了目标阻抗50Ω。该载片采用谐波控制技术使功率放大器附加效率提高了6%～8%，采用高介电常数的陶瓷材料将载片电路集成在8mm×8mm。实测结果显示，放大器在漏源电压28V、100us脉宽和10%占空比脉冲输入的工作条件下，在小尺寸的载体上实现了输出功率大于56W，功率附加效率大于78%的高效率指标。     

Use the water: In-situ resource technology for icy-surface landers

Robotic landers serve vital reconnaissance roles in the exploration of planetary surfaces, but are constrained by deliverable payload size and environment survivability. Although the Mars exploration rovers (MER) have shown incredible survivability, their solar power source limits the science output per sol. Future landers will be larger, and will incorporate more sophisticated data-collection and analysis packages, which will likely bring with them an increased demand for power. Anticipating this demand, we propose an innovative hybrid power system combining a primary radioisotope thermoelectric generator (RTG) with a secondary alkaline fuel cell. This combination provides the opportunity to utilize more effectively the energy produced by the RTG, to produce and store O₂ and H₂ via electrolysis of melted ice, and use this obtained O₂ and H₂ in a variety of ways, including as fuel for a regenerative fuel cell. This hybrid system has applications ranging from planetary rovers and deep-space probes to human habitats.     

空间核动力平台电力管理系统的设计

空间核动力平台是一种全新的电源推进一体化航天器,其电力系统具有三相交流输出、工况多且复杂、母线电压体制多等特点。为了解决空间核动力平台负载供电诸多难题,通过对系统功能、负载类型、母线体制、组成配置、工作模式、控制机制等方面论证分析,提出了一种新型空间核动力平台电力管理系统架构。其中,变配电系统从硬件实现角度解决了基于布雷顿热电转换系统输出为负载稳态供电问题,自主控制系统从软件控制角度解决了主能源、辅助能源等多能源间流动控制以及负载暂态匹配问题,这为未来空间核动力平台电力管理系统研究工作奠定了基础。     

Characteristics of thermal ion outflows in the polar cap according to data of the <Emphasis Type="Italic">Interball-2</Emphasis> satellite

Characteristics of polar wind fluxes at a height of ∼20000 km measured by the Hyperboloid mass-spectrometer installed onboard the Interball-2 satellite are presented in the paper. The characteristics are presented for the upwelling flows of ionospheric ions H⁺, He⁺, and O⁺ from the sunlit polar cap in the period of solar activity minimum. Orbit segments with minimal precipitation of magnetospheric ions and electrons were preliminarily selected, and the measurements where the fluxes of ions coming from the cusp/cleft were excluded as carefully as possible. Thus, the densities, field-aligned velocities, and temperatures of ions in the regions where fluxes of polar wind could be detected with the maximal probability degree are presented in the paper. It is found that cases when only H⁺ ions are reaching the detector are with high probability the polar wind outflows. Their characteristics agree well with the Tube-7 hydrodynamic model and are as follows: n ≈ 1.5 cm⁻³, V _∥ ∼ 21 km/s; T _∥ = 3500 K, and T _⊥ = 2000 K. In cases when He⁺ and O⁺ ions are also detected, the temperatures are substantially higher than the model ones, and the measured field-aligned velocities of O⁺ fluxes are several times higher than the model ones. Moreover, it was revealed that the polar wind outflows are predominantly observed in the polar cap regions where the polar rain fluxes are very small.     

Metallic and Oxidized Aluminum Debris Impacting the Trailing Edge of the Long Duration Exposure Facility (LDEF)

A total of 87 microcraters >30 m in diameter that were found in gold substrates exposed on the trailing edge of the non-spinning Long Duration Exposure Facility (LDEF) yielded analyzable projectile residues in their interiors. Using qualitative SEM-EDS analysis methods, some 60 of these craters were formed by natural cosmic-dust particles, while 27 residues (31%) were assigned to orbital debris (Hörz et al., 1993). The far majority of the orbital-debris impacts, 24 (89%) of the 27 events, contained only aluminum in their X-ray spectra. The present study evaluates these aluminum-rich residues in detail and employs a windowless X-ray detector, which permits for the analysis of low-Z elements and specifically of oxygen. This makes it possible to discriminate between oxidized (Al₂O₃) and metallic (Al) projectiles from dramatically different sources, the former produced during solid-fuel rocket firings, the latter resulting from explosively or collisionally disrupted spacecraft.Of the 24 craters analyzed with the windowless detector, 13 (54%) contained Al₂O₃ and 11 (46%) yielded structurally disintegrated Al metal. The oxidized residues preferentially occur in the smaller craters, all <60 m in diameter. Corresponding particles on LDEF's trailing edge are <35 m in diameter. Some 70% of this particle population is composed of Al₂O₃. Although solid-fuel rocket exhaust products are typically <5 m in size, they tend to coagulate into crusts at the rocket nozzle to be shed occasionally as relatively large, aggregate particles. Structurally disintegrated, metallic fragments compose one-third of all particles <35 m, but they dominate all particles >35 m, and thus all craters >60 m. These findings clearly establish that solid-rocket exhaust particles, as well as explosively or collisionally produced debris, exist in low-inclination, high-eccentricity orbits in sufficient quantities that they must be accounted for in models describing the present and future orbital-debris population at typical Shuttle and Space Station altitudes.     

释放SF_6气体改变电离层电子密度的实验研究

电离层受到自然或人工扰动后产生的电子密度变化会影响无线电的传播。实验模拟了人工释放SF_6气体扰动电离层,通过对SF_6气体在电离层中的扩散过程和相应的离子化学反应的分析,并结合实验测量,研究了电离层电子密度随SF_6气体释放量的变化规律。实验结果表明:SF_6气体在电离层高度释放后,电子密度显著减少,且减少量与气体释放量在一定范围内呈负指数关系。研究可为今后提高卫星通信保密性和实施通信干扰等应用提供理论依据。     

Deployment history and design considerations for space reactor power systems

The history of the deployment of nuclear reactors in Earth orbits is reviewed with emphases on lessons learned and the operation and safety experiences. The former Soviet Union's “BUK” power systems, with SiGe thermoelectric conversion and fast neutron energy spectrum reactors, powered a total of 31 Radar Ocean Reconnaissance Satellites (RORSATs) from 1970 to 1988 in 260 km orbit. Two of the former Soviet Union's TOPAZ reactors, with in-core thermionic conversion and epithermal neutron energy spectrum, powered two Cosmos missions launched in 1987 in ～800 km orbit. The US’ SNAP-10A system, with SiGe energy conversion and a thermal neutron energy spectrum reactor, was launched in 1965 in 1300 km orbit. The three reactor systems used liquid NaK-78 coolant, stainless steel structure and highly enriched uranium fuel (90–96 wt%) and operated at a reactor exit temperature of 833–973 K. The BUK reactors used U-Mo fuel rods, TOPAZ used UO₂ fuel rods and four ZrH moderator disks, and the SNAP-10A used moderated U-ZrH fuel rods. These low power space reactor systems were designed for short missions (～0.5 kW_e and ～1 year for SNAP-10A, <3.0 kW_e and <6 months for BUK, and ～5.5 kW_e and up to 1 year for TOPAZ). The deactivated BUK reactors at the end of mission, which varied in duration from a few hours to ～4.5 months, were boosted into ～800 km storage orbit with a decay life of more than 600 year. The ejection of the last 16 BUK reactor fuel cores caused significant contamination of Earth orbits with NaK droplets that varied in sizes from a few microns to 5 cm. Power systems to enhance or enable future interplanetary exploration, in-situ resources utilization on Mars and the Moon, and civilian missions in 1000–3000 km orbits would generate significantly more power of 10's to 100's kW_e for 5–10 years, or even longer. A number of design options to enhance the operation reliability and safety of these high power space reactor power systems are presented and discussed.     

超临界压力下航空煤油RP-3在水平细圆管内对流换热特性实验研究

为探究超临界压力下碳氢燃料在水平管内的对流换热规律,文章针对超临界条件下航空煤油RP-3在水平细圆管内的对流换热,分析了热流密度、进口雷诺数及浮升力对对流换热的影响。研究表明:沿流动方向,管内表面传热系数随热流密度的增大先减小后增大;在低进口温度及低进口雷诺数情况下,管内换热均出现先恶化后强化的现象,而随着进口温度和雷诺数的增加,此现象消失;浮升力对换热的影响随热流密度的增加而增加;浮升力对下表面换热的加强使得入口效应的影响在下表面先于上表面结束;受浮升力影响,上下壁最大温差可达50 K;质量流速的增加会抑制浮升力对换热的影响;准则数Grq/Grth可以很好地反映浮升力的变化趋势。以上研究结果可为采用碳氢燃料作冷却介质的各类飞行器主动热防护技术方案提供技术支撑。