涡轮基组合循环发动机分布式控制系统通信网络混合拓扑结构优化方法

涡轮机组合循环(Turbine based combined cycle,TBCC)发动机控制系统通信网络拓扑结构是其分布式控制系统方案设计的重要部分,优化网络拓扑结构可提高发动机推重比和控制系统可靠性。本文基于智能优化算法提出TBCC分布式控制系统网络拓扑结构优化方法。基于图论建立TBCC几何模型和网格模型,以重量和可靠性为优化性能指标,同时考虑发动机表面高温区域以及控制节点的工作可靠性,分别采用粒子群算法和遗传算法优化星形结构中智能中央节点位置、中央节点的环形拓扑结构,获得星形-环形混合拓扑结构。仿真实例表明,基于本文方法优化所得的混合拓扑结构相较于星形集中式控制结构,系统重量降低了51.9%。     

天基轻气炮发射清除低轨碎片方案及关键技术分析

文章分析了现有的空间碎片清除方式,并以800~1200 km低地球轨道高度上1~10 cm量级的空间碎片为清除目标,提出了天基轻气炮清除碎片的新方法。首先分析了轻气炮有效载荷在典型参数下的弹丸加速能力;之后根据将碎片降轨使其坠入大气层烧毁的设想,提出天基轻气炮共面清除碎片的方式,并选择轨道高度800 km的圆轨道作为碎片运行轨道进行可行性分析。计算表明,对半径10 cm、厚度1 cm的铝合金圆板碎片(质量211.95 g),使用初速1 km/s、重10 g的黏性弹丸可按任务方案达到清除效果。此外,计算出该参数弹丸对轨道高度800~1200 km的圆轨道上可清除的最大碎片质量为500~825 g,证明轻气炮弹丸对1~10 cm的碎片具有较强的清除能力。最后,分析了以轻气炮为有效载荷的航天器在完成清除碎片任务时的关键技术。     

多种工质下螺旋波等离子体源波场结构数值模拟

针对螺旋波等离子体放电机理，开展了多种工质条件下的螺旋波放电等离子体内波场结构数值模拟研究。计算发现:氦气等离子体的Er分量在径向边界处的峰值更为突出，有利于等离子体在径向的输运，波电场径向分量决定了电流密度径向分量在内部的表现。在0.266 Pa和1.064 Pa两种气体压强条件下，通过波场结构验证了气压对于波阻尼影响的结论。波场结构是螺旋波在等离子体内传播以及能量沉积的微观体现，研究螺旋波波场结构是揭示其高电离效率的重要途径。初步探索了功率耦合机制，为实验系统优化及实验方案设定奠定理论基础。     

Unsteady wakes-secondary flow interactions in a high-lift low-pressure turbine cascade

Detailed experimental measurements were conducted to study the interactions between incoming wakes and endwall secondary flow in a high-lift Low-Pressure Turbine (LPT) cascade. All of the measurements were conducted in both the presence and absence of incoming wakes, and numerical analysis was performed to elucidate the flow mechanism. With increasing Reynolds number, the influence of the incoming wakes on suppressing the secondary flow gradually increased owing to the greater influence of incoming wakes on reducing the negative incidence angle at higher Reynolds numbers, leading to a lower blade loading near the leading edge and suppression of the Pressure Side (PS) leg of the horseshoe vortex. However, the effect of unsteady wakes on suppressing the profile losses gradually became weaker owing to the reduced size of the Suction Side (SS) separation bubble and increased mixing loss in the free-flow region at high Reynolds numbers. Incoming wakes clearly improved the aerodynamic performance of the low-pressure turbine cascade at low Reynolds numbers of 25,000 and 50,000. In contrast, at the high Reynolds number of 100,000, the profile loss at the midspan and mass-averaged total losses downstream of the cascade were higher in the presence of wakes than in the absence of wakes, and the unsteady wakes exerted a negative influence on the aerodynamic performance of the LPT cascade.     

燃气的基准表及图制定

本文在阐述基准的热力学概念基础上,提出了燃气基准的计算方法,应用CHAPPELL推荐的有关燃气热力性质表达式,导出计算燃气基准的公式,通过微机计算,将结果整理成燃气基准的有关表、图。     

风量与风机的安全运行

本文阐明了离心式通风机在通风除尘(或排毒净化)系统中的作用,以及离心式通风机产生风压.风量的工作工程,从而引出风机的性能参数风量L、风压P、功率N、效率η等.文章突出地论述了风量对风压、功率、效率的影响;详尽地分析了离心式通风机的性能曲线,特别是N—L曲线;根据性能曲线分析得知,风量L为零(L=0)时,风消耗的功率N最小.从而得出结论;系统中的离心式通风机必须是在关闭状态下启动,以确保通风机的安全运行.     

错位与缺失

性权利是人类自然权利和社会权利的集合体,大学生拥有性权利是无可辩驳的事实。分析部分大学生漠视性隐私权、性教育权,只关注性自由权、性快乐权和自主选择权的原因,会发现其性价值观的错位和义务观的缺失是主要根源,加之媒体的不当报道也起到了推波助澜的作用。这样的现实要求我们必须加强大学生性权利的伦理教育以及性权利与性义务的对等教育。     

Emergence of a Habitable Planet

We address the first several hundred million years of Earth’s history. The Moon-forming impact left Earth enveloped in a hot silicate atmosphere that cooled and condensed over ∼1,000 yrs. As it cooled the Earth degassed its volatiles into the atmosphere. It took another ∼2 Myrs for the magma ocean to freeze at the surface. The cooling rate was determined by atmospheric thermal blanketing. Tidal heating by the new Moon was a major energy source to the magma ocean. After the mantle solidified geothermal heat became climatologically insignificant, which allowed the steam atmosphere to condense, and left behind a ∼100 bar, ∼500 K CO₂ atmosphere. Thereafter cooling was governed by how quickly CO₂ was removed from the atmosphere. If subduction were efficient this could have taken as little as 10 million years. In this case the faint young Sun suggests that a lifeless Earth should have been cold and its oceans white with ice. But if carbonate subduction were inefficient the CO₂ would have mostly stayed in the atmosphere, which would have kept the surface near ∼500 K for many tens of millions of years. Hydrous minerals are harder to subduct than carbonates and there is a good chance that the Hadean mantle was dry. Hadean heat flow was locally high enough to ensure that any ice cover would have been thin (<5 m) in places. Moreover hundreds or thousands of asteroid impacts would have been big enough to melt the ice triggering brief impact summers. We suggest that plate tectonics as it works now was inadequate to handle typical Hadean heat flows of 0.2–0.5 W/m². In its place we hypothesize a convecting mantle capped by a ∼100 km deep basaltic mush that was relatively permeable to heat flow. Recycling and distillation of hydrous basalts produced granitic rocks very early, which is consistent with preserved >4 Ga detrital zircons. If carbonates in oceanic crust subducted as quickly as they formed, Earth could have been habitable as early as 10–20 Myrs after the Moon-forming impact.     

低轨道带可变翼的平板型极高真空分子屏

本文计算了在低轨道自由飞行的平板型分子屏（ＷａｋｅＳｈｉｅｌｄＦａｃｉｌｉｔｙ）加了可变翼后，分子屏后实验区的压力分布。计算中考虑了分子屏和翼材料出气对实验区压力的影响。本文并对加可变翼和不加可变翼、考虑出气和不考虑出气几种情形进行了计算和比较。我们的结果表明：给轨道分子屏加上可变翼后，其实验区的压力可比不加可变翼降低一个数量级以上，压力达１０－１３Ｐａ。本文的研究表明，这种给轨道分子屏加可变翼的模型对更好的利用分子屏环境是非常有利的。     

混气电解加工中两相流音速及阻塞机理研究

着重分析研究气液两相流音速特性及其阻塞机理。通过测量由小药量电雷管爆炸而产生的压力波传播速度，然后修正到音速。试验结果表明，气液两相流音速与气泡率、当地压力及其流型有关。由于气液混合物强烈的压缩性，混气电解加工间隙中易于出现类似可压缩气体的阻塞现象。