PIV application in advanced low Reynolds number facility

The advent of micro aerial vehicles (MAV) and advanced flow control methods, using microelectromechanical systems (MEMS) and micro-blowing or suction, has significantly increased the need for a better understanding of very low Reynolds number flows. Aerodynamic testing in this flow regime using conventional facilities, such as wind or water tunnels, is seriously hampered by the necessary small model sizes and low testing speeds, rendering it very difficult to diagnose the flow with adequate spatial resolution and to measure aerodynamic loads with sufficient accuracy. A proof-of-concept pilot of a novel facility specifically intended for low Reynolds number testing has been built and is briefly described. It is based on the use of a high kinematic viscosity test medium, which allows testing superscale models at the correct Reynolds number. The facility is akin to a towing tank, but does not have a free surface with its associated shortcomings. Implementation of the particle image velocimetry (PIV) technique in this type of facility is complicated by the fact that the optics, rather than being stationary as is the case in conventional aerodynamic testing facilities, move in synchronism with the model. Mistracking directly results in velocity-field errors which must be corrected. Methods to do so are described.     

大气压条件下高焓空气等离子体流场特性及应用

评估和鉴定高超声速飞行器防热材料使用性能,需要在能够模拟飞行气动热环境的高焓设备中进行大量地面试验。详细介绍了一种能够运行在大气压条件下的电感耦合等离子体设备,该设备能够产生多种气体（空气、氮气、二氧化碳、氩气）的等离子体射流,运行功率范围为27~85.5 kW,最大运行效率可达77.9%。通过对30 mm的亚声速喷管出口8 mm处空气等离子体流场参数高精度重构和发射光谱测试研究,获得了气体温度和光谱发射强度沿径向的分布,等离子体的焓值范围为8.54~22.2 MJ/kg,驻点热流最高可达721 W/cm²。选定2个试验状态对典型防热材料C/SiC进行烧蚀氧化考核试验,并通过与国内外同类设备比较,表明该大气压感应耦合等离子体设备达到国际先进水平,完全具备开展高超声速飞行器防热材料性能改进地面模拟试验的能力。     

吸气式高超声速技术研究进展

总结了中国空气动力研究与发展中心(CARDC)在吸气式高超声速技术在试验设备、超燃冲压发动机、数值模拟以及机体/推进一体化飞行器等方面的研究进展。介绍了三种类型的高焓设备:脉冲式燃烧加热风洞、连续式燃烧加热风洞和电弧风洞。通过多种尺度的超燃冲压发动机的直连式和自由射流式试验,获得了发动机的基本性能及其随油气比、喷孔位置等的变化规律。对比连续式和脉冲式风洞试验结果,得知工作时间大于100 ms的脉冲式燃烧设备是开展发动机基本性能研究的经济、高效试验手段。成功研制了三维大规模并行数值模拟软件平台AHL3D并广泛应用于发动机研究。在0.6 m风洞中,完成了1.5 m带动力飞行器试验,获得了发动机工作和不工作状态下的飞行器推阻及升力特性。     

爆轰驱动膨胀管性能研究

超高速流动一般指速度超过5 km/s的流动,由于流动具有高焓高速的特点,模拟超高速流动的地面试验设备面临极大挑战。膨胀管(风洞)是少数几种具备超高速流动模拟能力的地面试验设备之一。中国科学院力学研究所高温气体动力学国家重点实验室(LHD)通过将正向爆轰驱动技术和膨胀管结合在一起,建成了可实现最高速度10 km/s超高速试验气流的爆轰驱动膨胀管(JF-16),并开展了典型模型试验。在此基础上对JF-16进行了改造升级工作,为其设计喷管增加了膨胀风洞运行模式,对其性能进行了相关试验测试研究。同时,对膨胀管相关数值方法进行了介绍,并开展数值模拟对试验状态进行辅助诊断和分析。     

高空台间接加热试验

用同一种发动机在不同模拟状态下，采用技改措施及加热器的火焰筒不同个数进行了试验，获得了模拟温度、气源压力与时间的关系。设备的总压系数为0．67；加热系统的总效率为0．41－0．55。与另一高空台使用同一间接加热系统的总效率（约为0．62）相比有所不同。分析了原因，并指出了解决问题的途径。上述试验方法及试验结果可供类拟发动机试验参考使用。     

基于粒子模拟的舱内布局对霍尔推进器可靠性评估真空羽流的影响

对霍尔推进器地面测试过程中真空环境下的羽流流场进行模拟研究,通过直接蒙特卡洛(DSMC)方法进行多种布局方式下的系列数值模拟,重点研究地面测试设施中舱内的抽氙冷板、束流挡板在不同布局环境下对真空羽流流场的影响。数值模拟结果显示:抽氙冷板的布局位置对羽流流场影响较不明显,但应考虑舱内各处均布以防压力局部集聚过高形成阻力;束流挡板对返流粒子的抑制作用明显,对抽氙冷板等具有较好的防护功能,但也同时改变了羽流流场分布,甚至会影响到推进器的放电特性和性能表现。通过该数值模拟方法可以实现对舱内工艺设备的设计指导,对抽氙冷板、束流挡板等进行布局优化,继而为推进器地面测试提供更为有效的测试环境。     

降低高空台涡喷发动机进气流场不均匀度装置的试验研究

本文介绍A及B型涡喷发动机在模拟高空试验时的进口总压畸变及测量技术。发动机在低转速工作时发生“放炮现象”,为消除此故障在发动机进口按装一种整流器(由一个收敛段和气动网格组成)使进口气流分布均匀。试验结果效果良好,使稳态不均匀度和动态湍流度明显下降。文中介绍此类整流器的规格及设计细节,具有工程实用价值。     

航空发动机试车台附加阻力修正方法

附加阻力(进气冲量阻力和外部冲量阻力)是航空发动机试车台架推力的重要组成部分,准确地确定附加阻力对提高发动机试车台推力测量的准确性有十分重要的意义。本文对发动机总推力和试车台的对比标定进行了介绍,对发动机在露天试车台、室内地面台和高空台上附加阻力的确定方法和修正方法进行了详细地研究,给出了高空台与高空台、高空台与地面台的对比标定试验结果。      

Electric-vehicle batteries

Electric vehicles that can't reach trolley wires need batteries. In the early 1900's electric cars disappeared when owners found that replacing the car's worn-out lead-acid battery costs more than a new gasoline-powered car. Most of today's electric cars are still propelled by lead-acid batteries. General Motors in their prototype Impact, for example, used starting-lighting-ignition batteries, which deliver lots of power for demonstrations, but have a life of less than 100 deep discharges. Now promising alternative technology has challenged the world-wide lead miners, refiners, and battery makers into forming a consortium that sponsors research into making better lead-acid batteries. Horizon's new bipolar battery delivered 50 watt-hours per kg (Wh/kg), compared with 20 for ordinary transport-vehicle batteries. The alternatives are delivering from 80 Wh/kg (nickel-metal hydride) up to 200 Wh/kg (zinc-bromine). A Fiat Panda traveled 260 km on a single charge of its zinc-bromine battery. A German 3.5-ton postal truck traveled 300 km with a single charge in its 650-kg (146 Wh/kg) zinc-air battery. Its top speed was 110 km per hour     

航空发动机高、低温起动及高原起动试验技术探讨

根据GJB241对航空发动机高、低温起动及高原起动试验的要求,分析了高、低温及高原环境条件对航空发动机起动性能的影响机理;阐述了利用自然环境条件、低温起动室及高空模拟试验台进行航空发动机高、低温起动及高原起动试验的优、缺点;结合国产斯贝MK202发动机分别在英国R.R.公司低温起动室和高空模拟试车台进行的低温起动试验方法和俄罗斯中央航空发动机研究院(CIAM)高空台的发动机高、低温起动及高原起动试验的方法,提出了符合我国国情的航空发动机高、低温起动及高原起动试验的实施途径。      

A numerical optimization of high altitude testing facility for wind tunnel experiments

High altitude test facilities are required to test the high area ratio nozzles operating at the upper stages of rocket in the nozzle full flow conditions.It is typically achieved by creating the ambient pressure equal or less than the nozzle exit pressure.On average,air/GN2is used as active gas for ejector system that is stored in the high pressure cylinders.The wind tunnel facilities are used for conducting aerodynamic simulation experiments at/under various flow velocities and operating conditions.However,constructing both of these facilities require more laboratory space and expensive instruments.Because of this demerit,a novel scheme is implemented for conducting wind tunnel experiments by using the existing infrastructure available in the high altitude testing(HAT)facility.This article presents the details about the methods implemented for suitably modifying the sub-scale HAT facility to conduct wind tunnel experiments.Hence,the design of nozzle for required area ratio A/A*,realization of test section and the optimized configuration are focused in the present analysis.Specific insights into various rocket models including high thrust cryogenic engines and their holding mechanisms to conduct wind tunnel experiments in the HAT facility are analyzed.A detailed CFD analysis is done to propose this conversion without affecting the existing functional requirements of the HAT facility.     

某高空台发动机进气流场试验分析

本文介绍了目前国内唯一能做涡轮喷气发动机高空模拟试验的试验设备的特点,着重对该高空台的进气流场进行分析、研究,得到一些有参考价值的结果,可供涡喷发动机设计者和试验人员参考。     

AEDC's facility computer enhancement project

The Arnold Engineering Development Center (AEDC) constitutes the largest collection of test cells, wind tunnels, altitude chambers, and ballistic ranges in the free world. AEDC is presently in the midst of an aggressive investment program to decrease the cost of aerospace testing by improving test efficiency and preparing for test requirements projected through 1993. To achieve the desired gains in testing, a multimillion dollar program has been initiated to upgrade data-processing capabilities. This effort, the Facility Computer Enhancement Program (FCEP), replaces the existing facility with new and more powerful computers and state-of-the-art communications networks that link all test processors at AEDC. Tradeoffs and technical considerations during the first year of the program and the design of the new system are discussed. Capabilities that support test objectives at the completion of the project are presented     

Dynamic qualification of the HIRENASD elastic wing model

The High Reynolds Number Aero-Structural Dynamics (HIRENASD) project is conducted by the Collaborative Research Center “Flow Modulation and Fluid-Structure Interaction at Airplane Wings (SFB 401)” at RWTH Aachen University. It is funded by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG) since 2004. Steady and unsteady state experiments with an elastic semispan wing model were performed under transonic and high Reynolds number conditions in the European Transonic Windtunnel (ETW) in Cologne, Germany. The main components of the complete windtunnel assembly were the wing model itself, a piezoelectric 6-components balance and a mechanical excitation mechanism able to excite the wing model at selected resonance frequencies. These components were designed, sized and assembled at the Department of Aerospace and Lightweight Structures at RWTH Aachen University. The dynamic qualification of the windtunnel assembly under wind-off condition was carried out in the department's test laboratory. Modal survey testing based on the hammer impact method was performed, as well as response decomposition analysis using enforced excitation by means of the mechanical excitation mechanism itself. Within the qualification, a test procedure enabling investigations of modal parameter changes under wind-off and wind-on conditions in a cryogenic windtunnel was also verified.     

羽流效应地面模拟试验系统关键技术发展

叙述了羽流效应地面模拟试验系统由高空模拟试车台向真空试验系统发展的过程,指出引射原理的局限性和低温冷凝技术的适用性.介绍了应用低温冷凝技术建成的美国CHAFF-4(the collaborative high altitude flow facility-Ⅳ)系统和德国STG(Simulationsanlage für Treibstrahlenin G?ttingen)系统及中国首座大型羽流效应地面模拟试验系统——PES(the plume effects experimental system)系统.采用直接模拟蒙特卡罗DSMC (direct simulation Monte Carlo )方法对PES设备的内置式液氦深冷泵的抽气能力进行了数值模拟研究,结果表明无论有无羽流吸附泵时,2g/s级发动机点火时,内置式液氦深冷泵都能满足发动机出口截面后 ? 4m×5m范围内的背压小于10-3 Pa,羽流吸附泵能有效地阻止压缩波向喷管方向推进.      

燃烧室火焰筒头部性能对比试验

根据前期某型发动机燃烧室头部降低冒烟数性能试验结果,火焰筒头部结构存在高温烧蚀变形痕迹,为保证该结构工 作可靠性和使用寿命,将原型燃烧室火焰筒头部传统的孔板+挡溅板的冷却结构改进为带有一定角度的收敛双锥形冷却结构,并 在单管燃烧试验器、扇形燃烧室试验件上采用连续气源、模拟参数进行了性能对比试验,录取了改进前后2种头部的点熄火边界、 燃烧效率及头部壁温。结果表明：在同工况下,改进后的火焰筒头部着火余气系数更大,点火边界更宽;贫油熄火边界相当;燃烧 效率基本相当,均大于0.99,符合性能要求;改进后火焰筒头部壁温较原型的有较大降低,温度分布更均匀。     

低雷诺数平面叶栅试验方法研究

传统的叶型气动设计体系建立在高雷诺数基础上,UAV（无人飞行器）的发展对低雷诺数叶型气动设计和试验验证提出了新的要求。本文就降低叶型试验雷诺数的原理、实现的方法进行了分析,提出了在现有试验器基础上进行设备改造的方案和试验调节方法,并根据试验数据对改造后试验器的低雷诺数流场进行了初步分析,在国内首次通过试验手段获得了某高...     

2.4m跨声速风洞大型飞机试验不确定度评估

2.4m跨声速风洞作为中国目前唯一的大型跨声速气动力试验设备,在中国大型飞机研制中发挥着十分重要的作用。因此,对该风洞试验数据质量的评估、控制和改进提高是一项紧迫的工作。笔者通过完善不确定度计算方法、详细标定基本不确定度源和编制评估软件等工作,建立了该风洞大型飞机试验的不确定度评估方法,并对某大型飞机模型试验结果开展了具体的评估与分析,澄清了该风洞大型飞机试验数据的质量水平。     

卫星导航陆基增强系统设备许可体系研究

陆基增强系统(GBAS)是支持飞机精密进近的下一代无线电导航设备。目前,在世界上安装GBAS和提供GBAS服务的机场越来越多。中国已经研制了首套卫星导航GBAS着陆系统,然而并没有通过相关设备的认证许可,未投入实际的运行使用。因此,本文在分析FAA和Eurocontrol对GBAS设备许可的基础上,提出了一套完整的卫星导航路基增强系统设备许可体系的方案,为进行设备的认证许可提供引导,使得整个地面子系统满足安装选址要求、地面和飞行测试对功能和性能的验证要求,保证地面设备子系统经过安装调试后能够达到理想的工作状态。设备许可体系在未来卫星导航技术的发展中发挥着广泛的指导作用,有利于设备的运行、发展和管理。     

美国航空推进系统关键技术

在美国的国防关键技术计划中，航空推进技术受到重视。通过对美国国家级计划－－高性能涡轮发动机综合技术计划、脉冲式爆震波产生推力的新概念发动机计划、燃烧室内气流过渡为超声速的冲压发动机计划的研究，对美国选择推进系统的理由作了分析，并对各国在航空推进系统的研究和发展工作进行了评估。可以看出，日本、德国继美、英、法、俄后在航空航天的推进系统方面已完成了一系列的研究。日本斥巨资建立发动机模拟高空试验台。最后详细列出了燃气涡轮发动机，其它航空动力和燃料三类中的10项关键技术。