飞行器管理系统需求

飞行器管理系统(VMS)将飞行、推进控制与相关的公管系统综合.飞行器管理系统的概念为性能改善带来了巨大的好处,同时对可靠性、维修性和保障性有重大改善.未来高性能的飞机将具有多操纵面/效应器以保证机动性,利用飞行/推进综合控制实现性能收益.随着更多系统的参与,综合设计的难度会增加.为确保VMS的实际应用,需要明确其计算和...     

Ionization effect of solar protons in the Earth atmosphere – Case study of the 20 January 2005 SEP event

The cosmic ray ground level enhancement on January 20, 2005 is among the largest recorded events in the history of cosmic ray measurements. The solar protons of MeV energies cause an excess of ionization in the atmosphere, specifically over polar caps following major solar disturbances. The ionization effect in the Earth atmosphere is obtained for various latitudes on the basis of solar proton energy spectra, reconstructed from GOES 11 measurements and subsequent full Monte Carlo simulation of cosmic ray induced atmospheric cascade. The estimation of ionization rates is based on a numerical model for cosmic ray induced ionization. The evolution of atmospheric cascade is performed with the CORSIKA 6.52 code using FLUKA 2006b and QGSJET II hadron interaction models. The atmospheric ion rate ionization is explicitly obtained for 40°N, 60°N and 80°N latitudes. The time evolution of obtained ion rates is presented. It is demonstrated that ionization effect is negative for 40°N and small for 60°N, because of accompanying Forbush decrease. The ionization effect is significant only in sub-polar and polar atmosphere during the major ground level enhancement of 20 January 2005.     

Drag force on solar sails due to absorption of solar radiation

We consider a special relativistic effect, known as the Poynting–Robertson effect, on various types of trajectories of solar sails. Since this effect occurs at order v^?/c, where v^? is the transversal speed relative to the sun, it can dominate over other special relativistic effects, which occur at order v²/c². While solar radiation can be used to propel the solar sail, the absorbed portion of it also gives rise to a drag force in the transversal direction. For escape trajectories, this diminishes the cruising velocity, which can have a cumulative effect on the heliocentric distance. For a solar sail directly facing the sun in a bound orbit, the Poynting–Robertson effect decreases its orbital speed, thereby causing it to slowly spiral towards the sun. We also consider this effect for non-Keplerian orbits in which the solar sail is tilted in the azimuthal direction. While in principle the drag force could be counter-balanced by an extremely small tilt of the solar sail in the polar direction, periodic adjustments are more feasible.     

The possibilities of polar meteorology,environmental remote sensing,communications and space weather applications from Artificial Lagrange Orbit

The ability to observe meteorological events in the polar regions of the Earth from satellite celebrated an anniversary, with the launch of TIROS-I in a pseudo-polar orbit on 1 April 1960. Yet, after 50 years, polar orbiting satellites are still the best view of the polar regions of the Earth. The luxuries of geostationary satellite orbit including rapid scan operations, feature tracking, and atmospheric motion vectors (or cloud drift winds), are enjoyed only by the middle and tropical latitudes or perhaps only cover the deep polar regions in the case of satellite derived winds from polar orbit. The prospect of a solar sailing satellite system in an Artificial Lagrange Orbit (ALO, also known as “pole sitters”) offers the opportunity for polar environmental remote sensing, communications, forecasting and space weather monitoring. While there are other orbital possibilities to achieve this goal, an ALO satellite system offers one of the best analogs to the geostationary satellite system for routine polar latitude observations.     

太阳模拟器光照不均匀性的研究

辐照不均匀性是太阳模拟器的一项主要技术指标.首先通过对国内外辐照不均匀性测量装置进行了充分的调研,决定采用“决门法”设计完成了辐照不均匀性的测量装置.接着通过试验证明了晴空无遮挡的太阳光可以作为该装置的标准光源并进行了该装置的标定.然后,利用该装置对自然光源进行了测试,结果与利用标准表测试一致.最后,利用该装置对脉冲式太阳模拟器的辐照不均匀性进行了现场测试.     

材料和尺寸参数对Rainbow型压电换能器发电能力的影响

给出了一种多方向振动能量收集装置的设计结构.为研究Rainbow型压电换能器材料、尺寸参数对其发电能力的影响,根据压电材料的机电耦合方程和对换能器的力学理论分析,建立了Rainbow型压电换能器开路电压与输出电能的数学模型.对开路电压模型进行了仿真验证,仿真结果与理论分析一致.对输出电能理论模型的数值模拟分析表明,金属基片的宽度与厚度、换能结构初始曲率半径的增大将会引起换能结构两片压电薄膜输出电能的降低;金属基片长度、压电薄膜宽度的增大将会引起两片压电薄膜输出电能的增加;压电薄膜长度、厚度的增大将会使得两片压电薄膜输出电能先增加后减小;铍青铜基片换能器要优于钢基片换能器;换能器弧形内侧压电薄膜的输出电能都要大于外侧压电薄膜.最后,结合Rainbow型压电换能器的力学分析给出了分析结果的合理解释.     

美国AEHF军事通信卫星推进系统及其在首发星上的应用

美国先进极高频（AEHF）项目将采用4颗运行于地球同步轨道（GEO）的AE—HF军事通信卫星。AEHF卫星的推进系统由远地点发动机、姿态控制发动机组和双模式霍尔电推进子系统组成。首发星AEHF-1是世界上首个采用霍尔电推进系统执行发射后轨道提升任夯的GEO卫星。AEHF-1卫星星箭分离后,远地点发动机未能正常工作,因此...     

基于多电技术的民用飞机舱门电作动器研究

目前国内多电技术的工程应用较少,基于此,以舱门电作动器为例,分析了其技术要求,从No-Back和软硬件设计技术两方面对设计难点进行了研究,然后对电机组件、齿轮装置、控制组件、控制板、作动器控制算法进行了系统设计,并完成样件试验。结果表明,样件满足设计要求和功能要求。     

碘工质射频离子推力器栅极系统束流特性仿真

为分析碘工质射频离子推力器束流特性,应用粒子云网格算法（PIC）,对碘工质射频离子推力器栅极系统进行三维数值仿真。碘工质电离产物中除了大量存在的I⁺,还包含少量I₂⁺、I²⁺、I³⁺几种多价离子。对添加多价离子前后束流特性的仿真结果进行对比,得出该栅极系统离子空间分布、电势分布、离子相空间分布以及束流、束流发散角,并对变密度工况下束流大小进行统计。计算结果表明,程序能较好地模拟离子在栅极系统中的运动情况：添加多价离子后,等离子体悬浮电势有所上升,鞍点电势有所下降,但整体电势分布的变化幅度较小;添加多价离子后束流大小略有增加,束流发散角略有减小,通过理论分析可知仿真所得理论推力及理论比冲均有小幅度增加;放电室等离子体数密度增加到约2.4×10¹⁷m^-3时,该栅极系统达到了束流引出的极限,后续增大等离子体密度引出束流不增反降。模拟结果可以为碘工质射频离子推力器栅极系统的设计提供参考。     

压气机线性振荡叶栅气弹试验研究（二）：叶尖间隙的影响

 为了加强对叶轮机三维气动弹性机理的理解,为数值模拟方法提供试验验证数据,开展了压气机线性叶栅气动弹性试验研究。本研究分为2个部分,第1部分研究压气机线性振荡叶栅的气弹稳定性,本文为第2部分,重点辨别叶尖间隙对压气机叶片气弹稳定性的影响。试验结果表明随着叶尖间隙的增加,间隙流对振动叶片有失稳影响,其影响范围几乎遍及整个叶高,这与非定常气动的瞬时径向相互作用的结论是一致的。这种失稳效应与叶片间相位角对叶栅气弹稳定性的影响不耦合。间隙流在叶栅稳定性最差时影响最显著。详细的非定常压力试验结果表明,随着叶尖间隙的增加,叶片表面非定常压力幅值减小区域与间隙流造成的卸载区域相对应。由试验结果可以推断,不考虑叶尖间隙的数值模型可能会给出过稳定的叶片颤振预测。