PICA-X的制备及其炭化前后性能研究

采用不同浓度热塑性酚醛树脂溶液浸渍莫来石纤维毡,经过溶胶-凝胶反应和常压干燥后,制备出酚醛浸渍陶瓷烧蚀体(PICA-X,0.45~0.50 g/cm~3),后研究了其炭化前后微观形貌、力学、隔热及抗氧化性能。结果表明:PICA-X具有莫来石纤维增强酚醛气凝胶复合结构,其弯曲强度为26.7~34.0 MPa,热导率为36~40 m W/(m·K)。经过1 000℃炭化后,C-PICA-X的弯曲强度为13.9~14.5 MPa,热导率为41~45m W/(m·K);PICA-X炭化前后均表现出较好的抗氧化性能。     

刚性短切碳纤维预制体和酚醛浸渍碳烧蚀体的制备及性能

以短切碳纤维、热固性酚醛树脂为原料,经真空成型得到短切碳纤维预制体(Fiberform),再以Fiberform为骨架、酚醛树脂溶液为浸渍液,经反应干燥得到酚醛浸渍碳烧蚀体(PICA)。结果表明:Fiberform具有明显的各向异性,当Fiberform的密度由0.13 g/cm~3增大到0.18 g/m~3时,其纵向压缩强度由0.10 MPa增大到0.39 MPa,横向压缩强度由0.33 MPa增大到0.79 MPa。PICA具有酚醛气凝胶/碳纤维复合型结构,其密度可以通过控制酚醛树脂溶液浓度来调节。当PICA的密度由0.27 g/cm~3增大到0.43 g/cm~3,其纵向压缩强度由0.45 MPa增大到2.42 MPa,横向压缩强度由1.36 MPa增大到3.12 MPa。PICA的隔热性能与Fiberform相近,其纵向和横向热导率分别为0.08和0.11 W/(m·K)。     

刚性短切碳纤维预制体和酚醛浸渍碳烧蚀体的制备及性能杨

以短切碳纤维、热固性酚醛树脂为原料,经真空成型得到短切碳纤维预制体(Fiberform),再以Fi鄄

berform 为骨架、酚醛树脂溶液为浸渍液,经反应干燥得到酚醛浸渍碳烧蚀体( PICA)。结果表明:Fiberform 具

有明显的各向异性,当Fiberform 的密度由0. 13 g/ cm3增大到0. 18 g/ m3 时,其纵向压缩强度由0. 10 MPa 增大

到0. 39 MPa,横向压缩强度由0. 33 MPa 增大到0. 79 MPa。PICA 具有酚醛气凝胶/ 碳纤维复合型结构,其密度

可以通过控制酚醛树脂溶液浓度来调节。当PICA 的密度由0. 27 g/ cm3增大到0. 43 g/ cm3,其纵向压缩强度由

0. 45 MPa 增大到2. 42 MPa,横向压缩强度由1. 36 MPa 增大到3. 12 MPa。PICA 的隔热性能与Fiberform 相近,

其纵向和横向热导率分别为0. 08 和0. 11 W/ (m·K)。

     

高硅氧纤维/酚醛泡沫复合材料的结构与性能

以高硅氧短切纤维毡为增强体,分别以酚醛树脂和酚醛泡沫为基体,制备了高硅氧/酚醛与高硅氧/酚醛泡沫两种复合材料,采用红外光谱分析、扫描电镜分析、热失重分析等方法对其结构和性能进行了表征。结果表明,两种材料具有相似的基体化学结构和相近的固化反应温度,均具有良好的耐热性能,性能测试结果表明,复合材料中基体由酚醛树脂变成酚醛泡沫后,力学性能明显降低,同时,密度由1.65 g/cm3降低至0.5 g/cm3,热导率由0.5 W/(m·K)降低至0.09 W/(m·K)。     

空心石英纤维/酚醛树脂复合材料的结构与性能

将石英纤维空心化,并通过模压成型方法制备了空心纤维/酚醛树脂复合材料。结果表明,空心纤维的空腔直径为4～7μm,随着纤维空心度增大(0～0.5),纤维的力学强度提高。在相同的纤维体积分数下,当纤维空心度从0增大到0.5时,复合材料的密度和热导率分别从1.63 g/cm3和0.49 W/(m·K)降低到1.46 g/cm3和0.41 W/(m·K),烧蚀性能保持不变。采用此方法制备的空心纤维/酚醛复合材料同时具有良好的隔热、防热性能。     

浸渍工艺对先驱体转化制备Cf/SiC复合材料结构与性能的影响

以聚碳硅烷(PCS)/二乙烯基苯(DVB)为先驱体制备了3D-B Cf/SiC复合材料,研究了不同浸渍工艺对材料力学性能的影响.结果表明采用加热加压浸渍可以大大提高先驱体的浸渍效率,提高所制备材料的密度,从而明显提高Cf/SiC复合材料的力学性能.选用加热加压浸渍条件所制备的材料密度达到1.944g/cm3,室温弯曲强度达到662MPa,在1650℃(真空)和1800℃(真空)下测试,材料的弯曲强度分别为647MPa和609MPa.     

超高温刚性隔热材料的制备及性能

针对新型航天飞行器高温隔热(约1 500℃)的迫切需求,开展了超高温刚性隔热材料的制备和性能研究。采用陶瓷纤维和无机粘结剂,经过湿法抽滤成型、高温热处理等工艺制备了刚性隔热材料。对材料的微观结构、热物理和力学性能进行了表征、测试。结果表明:纤维有效粘结在一起;通过改变纤维和粘结剂的比例,可以调节材料性能;热导率、力学性能与密度近似呈直线关系。材料在1 500℃经1 h处理后线收缩率<2%,密度为0.3～0.5 g/cm3,热导率为0.06～0.09 W/(m.K),压缩强度为0.6～1.2 MPa。     

整流罩用隔热材料的研制

以改性有机硅树脂基体和无纺纤维毡为原料,经喷涂定型工艺制备了低密度阻燃隔热材料.材料密度和热导率分别为0.27～0.36g/cm3和0.032～0.036 W/(m·K).测试分析了基体拉伸强度以及材料密度和厚度对隔热效果的影响.结果表明,隔热性能可满足直升机发动机整流罩的热防护要求.     

纺丝温度对新型高导热碳材料性能的影响

利用中间相沥青纤维的自粘结性和沥青大分子沿纤维轴高度择优取向的特点,通过热压方法制备高导热块体碳材料。在纺丝和氧化条件不变的情况下,主要考察了中间相沥青的熔融纺丝温度对纤维性能和目标材料性能的影响。结果显示:(1)熔融纺丝温度越高,中间相沥青纤维的直径越大;(2)在合适的纺丝温度下所得的纤维经氧化后热压制得材料具有较高的弯曲强度、密度、热导率以及较低的电阻率。选取纺丝温度为308℃,所纺中间相纤维直径为20μm,氧化后经热压所得材料的密度、弯曲强度、热导率和电阻率分别为2.02 g/cm3、128.7 MPa、597 W/(m.K)和1.25μΩ.m。     

氧化铝气凝胶复合高温隔热瓦的制备及性能

以陶瓷纤维制成的高温隔热瓦为骨架,真空浸渍氧化铝溶胶,再经过凝胶、老化和超临界干燥制备出氧化铝气凝胶复合高温隔热瓦,研究了其在不同温度处理后(最高温度1 400℃)的微观结构、隔热和力学性能。结果表明:气凝胶复合高温隔热瓦在1 400℃保温30 min后线收缩率仅为2%;随着热处理温度升高,气凝胶颗粒发生熔并、长大,气凝胶从填充纤维空隙到不断收缩,但对纤维骨架没有明显影响;隔热瓦的室温、高温热导率均显著降低;在热面1 400℃的背温测试中,复合后材料的背温从945℃降到870℃;复合后隔热瓦的力学性能略有增加;但是1 200~1 400℃的压缩强度下降较大。可见,气凝胶复合高温隔热瓦可改善其隔热性能,但在高温下力学性能下降。     

有翼高超声速再入飞行器气动设计难点问题

有翼高超声速再入飞行器是近年来的研究热点,气动设计是飞行器设计的关键。为了更清楚地认识有翼高超声速再入飞行器气动设计的难点问题,对有翼高超声速再入飞行器的发展、优势及总体任务剖面进行了介绍,从5个方面详细介绍了该类飞行器气动设计的难点问题,包括多约束复杂面对称气动布局设计、高温真实气体效应对气动特性影响、天地差异与天地换算方法、反作用控制系统(RCS)喷流干扰对气动特性的影响以及气动数据不确定度等,简要阐明了这些难点问题对总体设计的重要性以及初步的解决思路,为有翼高超声速再入飞行器气动设计提供了一些参考。     

Simulation and Analysis of Crashworthiness of Fuel Tank for Helicopters

Crashworthiness requirement of fuel tanks is one of the important requirements in helicopter designs. The relations among the protection frame, textile layer and rubber layer of the fuel tank are introduced. Two appropriate FE models are established, one is for an uncovered helicopter fuel tank without protection frame, and the other is for fuel tank with protection frame. The dynamic responses of the two types of fuel tanks impinging on the ground with velocities of 17.3 m/s are numerically simulated for the purpose of analyzing energy-absorbing capabilities of the textile layer and protection frame. The feasibility of the current crashworthiness design of the fuel tank is examined though comparing the dynamic response behaviors of the two fuel tanks.     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

ν-gap度量及其在飞行控制律评估中的应用

 传统控制律评估方法主要用于单输入单输出（SISO）系统，且对模型参数摄动考虑不够全面,针对这些不足，研究了ν-gap度量方法。在介绍系统广义稳定裕度相关概念的基础上，给出了ν-gap度量的定义、特点和性质以及近似摄动模型的计算，提出ν-gap度量评估控制律的步骤。实例结果表明，该方法不仅克服了上述传统评估方法的缺陷，而且还有根据所求的各摄动影响情况忽略影响小的元素，以减少计算量及可以找到最坏情况下的参数摄动组合等优点。     

突破技术趋同，波音再现竞争优势

 波音公司面临着来自空客公司的巨大挑战,企业战略性创新才是公司成功的关键。为此波音公司的全部战略性研究集中在扩大产品的差异性上,体现在3个方面：电子化（e-Enabled）运营环境、整体复合材料机身部件的制造技术和支持波音787客机的全球协同环境（GCE）。     

临近空间飞行器测控与信息传输系统频段选择

 临近空间飞行器是高性能信息化武器平台,测控（TT&;C）与信息传输系统是其信息保障的核心,而选择合理、可行的频段是展开系统设计的前提和基础。频段选择影响到整个技术方案的制定,是一个需综合考虑、影响深远并具有战略意义的关键问题,从国际电联（ITU）国际标准、高速数传、接收信噪比（SNR）、“三抗”、超视距中继、黑障、雨衰以及设备研制成熟度8个方面全面、细致论证了近空间平台测控系统的频段选择问题,最终得出在视距链路中以Ka频段为宜,在超视距链路中以Ku/Ka双频段为宜的结论。     

基于弯曲激波压缩系统的高超声速进气道反设计研究进展

总结了近十年来弯曲激波压缩研究的主要成果。提出了弯曲激波压缩系统的新概念,即利用特殊设计的楔形弯曲压缩面或空间弯曲压缩面,产生一系列与前缘弱激波相互交汇或叠加的压缩波系,从而使前缘激波弯曲,形成特殊的弯曲激波,它与波后的等熵压缩波来共同完成对气流的压缩。在此基础上,实现了由给定出口气动参数的超声速内流道反设计,实现了由给定压缩面压力分布和给定压缩面马赫数分布要求的型面反设计,实现了由给定激波波面的压缩型面反设计。研究证明,弯曲压缩面-弯曲激波压缩系统具有良好的综合气动性能,为高性能高超声速进气系统的气动设计提供了一种全新的设计方法。     

Integrated Entry Guidance for Reusable Launch Vehicle

A method for the implementation of integrated three-degree-of-freedom constrained entry guidance for reusable launch vehicle is presented. Given any feasible entry conditions, terminal area energy management interface conditions, and the reference trajectory generated onboard then, the method can generate a longitudinal guidance profile rapidly, featuring linear quadratic regular method and a proportional-integral-derivative tracking law with time-varying gains, which satisfies all the entry corridor constraints and meets the requirements with high precision. Afterwards, by utilizing special features of crossrange parameter, establishing bank-reversal corridor, and determining bank-reversals according to dynamically adjusted method, the algorithm enables the lateral entry guidance system to fly a wide range of missions and provides reliable and good performance in the presence of significant aerodynamic modeling uncertainty. Fast trajectory guidance profiles and simulations with a reusable launch vehicle model for various missions and aerodynamic uncertain-ties are presented to demonstrate the capacity and reliability of this method.     

Experimental Study on Effects of Fuel Injection on Scramjet Combustor Performance

In order to investigate the effects of fuel injection distribution on the scramjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The results of Test A, whose fuel injection is carried out with injectors located on the top-wall and the bottom-wall, show that the fuel injection with an appropriate close-front and centralized distribution would be of much help to optimize combustor performances. The results of Test B, whose fuel injection is performed at the optimal injection locations found in Test A, with a given equivalence ratio and different injection proportions for each injector, show that this injection mode is of little benefit to improve combustor performances. The results of Test C with a circumferential fuel injection distribution displaies the possibility of ameliorating combustor performance. By analyzing the effects of injection location parameters on combustor performances on the base of the data of Test C, it is clear that the injector location has strong coupled influences on combus- tor performances. In addition, an inner-force synthesis specific impulse is used to reduce the errors caused by the disturbance of fuel supply and working state of air heater while assessing combustor performances.     

(高)超声速流动试验技术及研究进展

近年来,与高速飞行器相关的(高)超声速流动受到了极大的关注。这类流动所具有的非定常性、强梯度和可压缩性对试验方法和风洞设计技术提出了挑战。超声速纳米示踪平面激光散射(NPLS)技术是由作者所在团队研发的非接触光学测试技术。它能够以较高的空间分辨率来揭示超声速三维流场的一个瞬态剖面的时间解析的流动结构。介绍了NPLS技术以及基于NPLS开发的密度场测量、雷诺应力测量和气动光学波前测量等方法,并回顾了这些技术在超声速边界层、超声速混合层、超声速压缩拐角、激波/边界层相互作用和光学头罩绕流等流动中的应用,清晰地再现了边界层、混合层、激波等典型流场结构及其时空演化特性。另外,为了模拟和研究高空大气条件下边界层自然转捩和超声速混合层的转捩特性,介绍了高超声速静风洞、超-超混合层风洞的设计技术以及层流化喷管的设计方法。