辅助动力装置排气系统气膜冷却效果

为研究辅助动力装置（APU）排气系统的冷却空气引射孔、引射缝以及飞机后整流罩形状等对冷却效果的影响,采用商业CFD软件Fluent,选用realizable k-ε湍流模型和DO热辐射模型建立了13个有不同引射孔位置、引射缝尺寸和飞机尾罩形状的排气系统流动和传热数值计算模型,得到了流场、温度场和热流分布。计算结果表明,冷却空气引射缝大小、引射孔的位置与形状面积以及后整流罩形状对APU排气系统的气膜冷却效果有重要影响。     

飞机BCU故障注入系统研究

针对飞机BCU特性,设计了一种能兼顾BCU从方案、生产、调试、验收等几个阶段的故障注入系统,并通过元件级、组件级和系统级3种形式故障注入试验,验证故障注入系统正确性,从而提高BCU的测试性和可靠性。     

超声速湍流边界层中横向声速喷流的混合LES/RANS模拟

通过对超声速湍流边界层中横向声速喷流的计算,对一种混合大涡/雷诺平均Navier-Stokes(LES/RANS)模拟方法进行了测试,该方法采用一个依赖于到壁面的距离及当地湍流参数的混合函数结合两方程k-ω SST(shear stress transport)湍流模型和混合尺度亚格子模型来封闭湍流项.计算结果表明:混合模拟方法能够捕捉到喷流/湍流边界层相互干扰的非定常大尺度结构,且对分离区长度、壁面静压峰值和膨胀区静压分布的计算精度要高于RANS(Reynolds-averaged Navier-Stokes)方法.      

高马赫数射流预冷试验装置设计及试验验证

为加速中国射流预冷技术的研究,设计了1套基于高马赫数的射流预冷试验装置。对试验装置需满足的功能流程和设计需求进行了识别,明确了试验装置的组成;对试验段和水系统的结构进行了详细设计,提出了直杆型和圆环型2种不同喷杆布局的射流段,并对使用2种射流段时试验段的流场均匀性进行了分析,认为直杆型射流段的温度场和压力场分布更加均匀;选取几种典型的试验工况,对所设计的试验装置进行了温降特性、总压恢复系数以及流场均匀性等试验验证。结果表明：试验装置总体运行良好,结构设计合理,能够完成全工况下的射流预冷试验,其温降特性、总压恢复系数和流场均匀性符合试验预期,研究成果对中国航空领域射流预冷发动机的研制具有指导意义。     

基于光固化成形技术的复杂航空零件快速制造方法

提出一种基于光固化成型技术的复杂航空零件快速制造方法。根据零件结构设计模具,采用光固化成形技术制造压蜡模具型壳,填充金属树脂复合材料,经过固化、去应力等工序实现压蜡模具制造;并基于蜡模制造复杂AISI316L航空零件。该制造方法周期短、精度高、成本低,能够快速响应市场的需求。     

高温合金材料螺孔加工技术研究

高温合金GH4169属镍基高温合金,是航天发动机高温系统中应用广泛的高温结构材料,但它的切削加工性能极差.如以相对正火状态45钢的切削加工性Kv=1来衡量,高温合金的切削加工性Ky=0.2～0.5,而镍基高温合金的Kv=0.2.其切削加工特点主要表现为强度高,塑性大,切削抗力大,冷作硬化严重,切削温度高,刀具在加工过程中磨损剧烈,以攻丝为加工最难点,小直径的螺孔用普通攻丝方法几乎无法加工,已经严重影响了公司的生产进度和产品质量.我们经过自己研究、攻关和与国内几所大学联合开发,特别是利用北京师范大学的离子注入技术,开发出加工高温合金螺孔的新型丝锥,现已用于公司的发动机生产,基本能满足公司的需要,解决了存在多年的高温合金的螺孔加工的难题.     

发散冷却最小冷却介质注射量的数值研究

充分发挥材料本身的抗高温能力, 以最小的冷却介质注射量, 确保推进器不被烧蚀是发散冷却系统的设计目标.本文用一维可压缩、非稳态、局部非热平衡模型, 数值研究了瞬态冷却过程及最小冷却介质注射量的依赖参数.数值研究表明:研究瞬态的冷却过程十分重要, 因为尽管当冷却过程达到稳态以后热端温度在烧蚀点以下, 但在进入稳态之前可能已经发生烧蚀;多孔介质骨架材料的初始温度越高、特征尺寸越大, 冷却介质需要量越大;在仅考虑冷却效果的前提下, 孔隙率越大, 冷却介质需要量越大;相反, 骨架材料导热系数越高, 冷却介质需要量越小.      

注塑模成型零件工作尺寸的概率计算法

在分析塑料收缩率波动规律的基础上,导出了注塑模成型零件工作尺寸的概率计算公式,讨论了塑料收缩率波动范围、塑件尺寸公差、制造公差以及修模裕磨量之间的关系。研究表明,概率法计算注塑模成型零件工作尺寸比广为采用的极值计算法更为合理。     

Comparison of aerodynamic characteristics between a novel highly loaded injected blade with curvature induced pressure-recovery concept and one with conventional design

This paper introduces a novel design method of highly loaded compressor blades with air injection.CFD methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade.A compressor blade is designed with a curvature induced pressure-recovery concept.A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure,which is referred to as a curvature induced ‘Shock'.An injection slot downstream from the ‘Shock' is used to prevent ‘Shock' induced separation,thus reducing the loss.As a result,the compressor blade achieves high loading with acceptable loss.First,the design concept based on a 2D compressor blade profile is introduced.Then,a 3D cascade model is investigated with uniform air injection along the span.The effects of the incidence are also investigated on emphasis in the current study.The mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow field.For the highly loaded cascade without injection,the flow separates immediately downstream from the ‘Shock';the initial location of separation shows little change in a large incidence range.Thus air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced ‘Shock' and reduces the size of the separation zone at different incidences.Near the endwall,the flow within the incoming passage vortex mixes with the injected flow.As a result,the size of the passage vortex reduces significantly downstream from the injection slot.After air injection,the loss coefficient along spanwise reduces significantly and the flow turning angle increases.     

On the anthropogenic and natural injection of matter into Earth’s atmosphere

Every year, more and more objects are sent to space. The increasing number of countries with space programs, advancing commercialization, and ambitious satellite constellation projects raise concerns about space debris and the increase of mass flux into the atmosphere due to deorbiting of satellites and rocket bodies. A comparison of this anthropogenic influx to the natural influx due to meteoroids is presented giving detailed information about the mass, composition and ablation of the entering matter. Currently, anthropogenic material does make up about 2.8% compared to the annual injected mass of natural origin. For two different future scenarios considering planned and already partially installed large satellite constellations this fraction increases to nearly 13%, respectively 40%. For these cases, the anthropogenic injection of several metals prevails the injection by natural sources by far. Considering different ablation products, we find that the anthropogenic injection of aerosols into the atmosphere increases disproportionately. Today, they make up about 1% compared to the injected aerosol mass of natural origin, increasing to 30% and 94% for the two future scenarios, respectively. Considering the injection of atoms, the natural injection is dominant by far. For the two future scenarios, the anthropogenic injection is only at 5%, respectively 15% compared to the annual natural atom injection. The predicted strong increase in anthropogenic injection will make it significant in comparison to the natural injection which can have yet unknown effects on Earth’s atmosphere and the terrestrial habitat.