基于场协同原理的横排锯齿翅片湍流传热强化机理

通过数值模拟方法分析了横排(TD)锯齿翅片在板翅换热器通道内传热与流动特性.研究了湍流条件下横排锯齿翅片的温度场,速度场以及两场协同性,探索其强化传热机理.在此基础上获得了翅片高度,翅片间距和翅片宽度对传热与流动的影响规律,并给出了横排锯齿翅片的综合传热性能因子.结果表明:横排锯齿翅片通道内流体扰动强烈,形成了周期性纵向涡流;改善了通道内速度与温度梯度场之间的协同作用,强化传热效果,提高了综合传热性能因子.      

地外天体起飞时进入喷管内部激波对喷管的力、热效应

为研究激波进入喷管内部对发动机喷管产生的力、热效应,对喷管与起飞平台基面之间的羽流场进行了大量的仿真计算,着重分析了不同导流型面、不同起飞偏角情况下,进入喷管内部激波对喷管产生的力、热综合效应,激波在喷管内部的分布形态,并给出了激波移出喷管的条件.结果表明:当激波进入喷管内部但不产生激波贴壁现象时,激波不会对喷管内壁产生附加的力、热冲击;当激波进入喷管内部且产生激波贴壁现象时,在激波贴壁区产生一定的附加力矩和附加热流.该结论对探测器结构布局的设计具有重要的指导作用.      

A review of recent studies on rotating internal cooling for gas turbine blades

Gas turbines have been used extensively for aircraft and marine propulsions as well as land-based power generation because of their high thermal efficiency and large power to weight ratios. To further increase the thermal efficiency, numerous prior researches on gas turbine blade internal cooling have been intensively carried out, majorly under stationary conditions. However, the stationary studies neglect the effects of Coriolis and buoyancy forces, which should change the velocity, turbulence and temperature distribution under rotating conditions. To elucidate the rotational effects on gas turbine internal cooling, the extensive results collected from recent investigations are discussed, which include the rotation and buoyancy effects on the rib turbulated cooling, pin fin cooling, jet impingement cooling, dimple/protrusion cooling, latticework cooling as well as swirl cooling. The rotational effects on the friction factors and the most employed experimental and numerical methods are also presented. Moreover, recommendations for future research are outlined. Therefore, this review article provides extensive literature information for the design of the next-generation high-efficiency internal cooling for rotating turbine blades.     

新型铝锂合金AA2198高频疲劳红外热耗散演化规律

利用红外成像技术开展新型铝锂合金AA2198高频疲劳（100 Hz）热耗散演化规律研究,发现不同应力条件下疲劳热耗散呈现上下波动特征,试件平均温度随着加载应力的提升有增加的趋势,但升温现象并不明显,不同应力条件下温度变化幅值小于1℃。疲劳试验初期和疲劳断裂时伴随着急剧升温过程,提出的能量转化理论模型合理解释了疲劳热耗散演化过程。研究还发现,喷丸强化在试件表面形成的残余压应力有助于激发疲劳裂纹的闭合效应,对试件的升温过程具有抑制作用。     

增强型轨道列表星历及其在北斗混合星座中的应用

为了改进北斗卫星数小时内的力模型精度,分析日月引力摄动和光压摄动的短期变化特性,提出基于二次多项式逼近日月引力摄动的15参数增强型轨道列表星历模型。利用该星历模型对北斗的5 GEO + 5 IGSO + 4 MEO混合星座进行了为期11天的星历拟合实验。结果表明,三类卫星在非地影期的2小时星历拟合精度优于1 cm。增强型轨道列表星历模型没有轨道根数的潜在奇点问题,能够为我国北斗星座和星基增强系统提供更多可行的星历模型选择。     

X-37B的发展现状及空气动力技术综述

X-37B的研制和试验国内外一直高度关注。X-37B作为跨大气层飞行器,从空气动力技术角度分析其研究工作很有意义。介绍了X-37B的发展历程,分析了战略用途,并重点介绍了涉及的一些关键气动技术,如气动布局设计优化、气动舵面/RCS/O MS复合控制设计、热防护技术、气动辅助变轨技术等,对其利用三大手段开展的研究工作也作了简要介绍,最后简要总结了X-37B研制过程中的一些经验教训。     

低功率氮氢混合物电弧加热发动机模拟研究

对低功率电弧加热发动机内的传热与流动过程进行了数值模拟研究,分别采用氮氢混合物模拟氨和肼作推进剂,计算获得了不同入口总压和弧电流的多种工况条件下发动机内温度和速度分布.结果表明,随着弧电流的增加,发动机出口处的温度、速度和比冲也随之增加;随着入口总压的增加,工作气体流量增加,发动机喷管出口处轴向速度增加.对NASA 1 k W级电弧加热发动机采用氮氢模拟肼作推进剂进行了数值模拟,模拟结果与文献报道的实验结果大体相符.     

GEO卫星电推进与化学推进组合变轨方案研究

针对GEO卫星采用电推进和化学推进系统进行变轨的问题,在给定轨道控制模型的基础上,给出实现轨道半长轴、偏心率和倾角3个参数单独调整和联合控制的控制律。结合假设的运载火箭发射能力约束,给出航天器不同入轨高度对应的初始质量。以此为约束,给出化学推进和电推进不同组合的6种GTO向GEO转移方案,并对比分析各方案完成变轨所需的时间、推进剂、速度增量以及完成变轨后的质量剩余情况,研究方法可为电推进系统在航天领域的应用提供参考。     

Multiobjective genetic optimization of Earth–Moon trajectories in the restricted four-body problem

In this paper, optimal trajectories of a spacecraft traveling from Earth to Moon using impulsive maneuvers (ΔV maneuvers) are investigated. The total flight time and the summation of impulsive maneuvers ΔV are the objective functions to be minimized. The main celestial bodies influencing the motion of the spacecraft in this journey are Sun, Earth and Moon. Therefore, a three-dimensional restricted four-body problem (R4BP) model is utilized to represent the motion of the spacecraft in the gravitational field of these celestial bodies. The total ΔV of the maneuvers is minimized by eliminating the ΔV required for capturing the spacecraft by Moon. In this regard, only a mid-course impulsive maneuver is utilized for Moon ballistic capture. To achieve such trajectories, the optimization problem is parameterized with respect to the orbital elements of the ballistic capture orbits around Moon, the arrival date and a mid-course maneuver time. The equations of motion are solved backward in time with three impulsive maneuvers up to a specified low Earth parking orbit. The results show high potential and capability of this type of parameterization in finding several Pareto-optimal trajectories. Using the non-dominated sorting genetic algorithm with crowding distance sorting (NSGA-II) for the resulting multiobjective optimization problem, several trajectories are discovered. The resulting trajectories of the presented scheme permit alternative trade-off studies by designers incorporating higher level information and mission priorities.     

短基线高准确度时间传递研究

为了实现守时系统与授时系统的高准确度时间同步,通过搬运钟法对微波时间传输系统的可测量时延部分进行准确测量,应用测量结果对微波时间传输系统进行校准,将GPS共视比对结果与微波时间传输系统的单、双向比对结果进行分析研究,并用BIPM(BUREAU INTERNATIONAL DES POIDS ET MESURES)给出的结果进行验证,得出两种不同时间同步方法的同步误差和两种不同方法产生误差的主要原因,给出了两种不同方法在时间统一系统中的的最佳应用模式。