沉积参数对磁控溅射镀金膜膜层残余应力与微观形貌的影响

残余应力直接影响镀膜膜层的稳定性与可靠性。为减小薄膜的残余应力,提高镀膜膜层的可靠性,在不同溅射气压、不同镀膜温度条件下,在熔融石英基底上进行了直流磁控溅射镀金膜试验。通过基片曲率法得到薄膜的残余应力,采用激光平面干涉仪对基片的形变进行测试,对不同工艺参数下膜层的残余应力进行分析,并采用扫描电镜对膜层的表面形貌进行测试。通过试验可知,磁控溅射镀膜膜层的残余应力随镀膜温度的升高而升高,在一定工作气压范围内（0.2Pa~0.6Pa)随溅射气压的增加而降低。电镜测试结果表明,常温镀膜晶粒的尺寸约为30nm,180℃镀膜晶粒的尺寸增长至近100nm。镀膜温度越高,薄膜的微观结构越致密。     

钛合金稀土阳极化成膜过程的电化学研究

 对钛合金稀土阳极氧化的电化学过程进行了研究;重点研究了钛合金稀土阳极氧化的成膜过程;分析了不同硫酸浓度,不同成膜电压条件下,电化学参数的变化,讨论了稀土阳极氧化膜的形成机理;通过对阳极氧化膜的 SEM微观形貌图及其他电化学参数的分析,推断氧化膜为分层结构;在一定温度和电压下,对电极电位的变化进行了研究,探讨了稀土阳极氧化膜的形成过程和导电机制;提出了稀土阳极氧化膜是由具有一定半导体特性和电容性的致密层与多孔层构成的,整个成膜过程中导电是由空穴、铈盐离子和溶液离子共同完成的。     

纳米多层膜及其在材料连接应用中的研究进展

纳米多层膜由于尺寸效应,存在熔点降低现象,应用于温度敏感材料的连接具有明显优势。同时由于多层膜层剧烈而快速的自蔓延放热反应,应用于连接时可以提供巨大热量。一方面可作为中间层辅助钎焊或扩散焊接;另一方面可作为独立热源为连接提供热量。纳米多层膜反应过程的实时观察受到单镜头拍摄速度和测量精度等条件的限制,而分子动力学模拟的应用为纳米多层膜反应机理研究拓展了新的思路。     

表面热膜测试技术在边界层测量中的应用

表面热膜测试技术由于其高频响特点,且能反映边界层从前缘到尾缘的连续瞬态变化过程,在边界层测量中很具优势.概要介绍了表面热膜的使用方法,深入探究了表面热膜探针测量的不确定性,发展了一套表面热膜测试技术的使用方法.利用多通道表面热膜探针测试技术,研究了某一负荷分布下边界层的发展过程,准确捕捉到了边界层的分离和转捩位置,表明了表面热膜探针测量结果的有效性和可靠性.     

ZrO2纳米颗粒含量对AZ91D镁合金微弧氧化膜耐蚀性的影响

为了提高AZ91D镁合金的耐蚀性能,利用单极性脉冲电源制备具有不同ZrO₂纳米颗粒含量的微弧氧化膜层,研究纳米ZrO₂颗粒对AZ91D镁合金微弧氧化膜层耐蚀性的影响。采用扫描电子显微镜观察复合膜层的表面及截面形貌;同时利用X射线衍射仪分析不同ZrO₂纳米颗粒含量的膜层中的相组成;测试样品的电化学腐蚀性能。结果表明：当电解液中加入1 g/L ZrO₂颗粒时,纳米ZrO₂颗粒能够渗入微弧氧化膜层之中,封闭膜中原有的微孔和微裂纹等缺陷,膜层表面质量较好;随着电解液中ZrO₂颗粒含量由2 g/L增加到3 g/L时,膜层的裂纹明显增多,导致腐蚀介质容易进入膜层发生腐蚀,耐蚀性能下降;在电解液中添加纳米ZrO₂颗粒时,1～3 g/L范围内添加1 g/L ZrO₂纳米颗粒的微弧氧化膜层的耐蚀性能最好。     

纳米流体强化倾斜丝网热管换热特性

对纳米流体强化不同倾角轴向丝网热管的换热特性进行了实验研究,实验以水基CuO纳米流体作为工质,在稳压条件下运行,运行压力为7.45,12.38和19.97 kPa(对应的蒸汽饱和温度为40℃,50℃和60℃).实验结果表明,纳米流体质量浓度对倾斜热管的总热阻有明显的影响,存在一个使热管热阻最小的最佳质量浓度,此质量浓度为1.0%.倾角对热管的换热特性有很大的影响,倾角为45°左右时,热管的蒸发换热系数强化率最大.在此倾角下,蒸发换热系数最大增加了20%,热管的总热阻大约降低了15%.而最大热流密度的强化效果则随着热管倾角的增大而增强,最大增加25%左右.      

热膜测试技术在涡轮叶栅边界层测量中的应用

为了更加精确地测量附面层流动状态,并验证表面热膜测试技术的可靠性,利用表面热膜测量了低雷诺数定常来流条件下高负荷涡轮叶栅通道内叶片吸力面附面层的流动状态,并与表面静压实验测得结果进行对比。结果表明,利用表面热膜测得的准壁面剪切力以及相关的统计参数能够准确捕捉到附面层分离泡和转捩的位置,对于高负荷低压涡轮叶型附面层流动测量是可靠有效的。     

液态水含量对防冰表面水膜流动换热的影响

为了研究液态水含量对防冰表面水膜流动换热的影响,基于机翼防冰表面水膜及空气相互作用机理,并考虑水膜表面传热传质过程,建立了水膜与空气的流动换热模型,得到溢流水膜及空气边界层流动换热的积分控制方程,通过对比文献试验结果验证了模型的准确性.在此基础上,比较了不同液态水含量条件下防冰表面水膜厚度及主要热流量的分布情况.结果表明:液态水含量对水膜沿表面厚度分布有明显影响,而对换热过程中各项热流的影响主要集中在水滴撞击区域,加热热流与散热热流随液态水含量的增加呈现相反的变化趋势.     

燃气环境内高温部件红外测温试验方法

针对航空发动机加力燃烧室高温部件温度场测试精度不高的问题,提出了一种燃气环境内高温部件红外测温试验方法。在同一时刻,分别用配装3.97～4.01μm窄带滤光片的红外热像仪和K型热电偶测试了燃气环境内高温部件在8种不同状态下的壁面温度分布,并对测试结果进行了对比,根据K型热电偶测试结果引入红外热像仪测试结果综合修正系数。结果表明：所引入的综合修正系数可有效地修正表面发射率、高温燃气、蓝宝石玻璃窗口以及环境大气等因素在不同温度条件下所带入的测试误差,经修正后红外热像仪和热电偶之间的测试偏差可控制在1.5%以内。该方法为后续航空发动机加力燃烧室高温构件温度分布测试提供了一种方法和思路。     

基于Myers模型的三维结冰数值仿真

三维结冰表面上的水膜流动和结冰增长是结冰计算模型应考虑的核心内容,其中广泛应用的是Myers模型。Myers模型考虑了空气剪切力和空气压力对结冰表面水膜流动的影响,以及冰层、水膜和空气之间的导热与对流传热对结冰速率的影响。本文在使用Myers模型进行结冰预测时,发现Myers模型对霜冰转化为明冰的判断标准存在缺陷,会在结冰极限处产生不合理的冰角。因此对Myers模型的结冰类型判断标准进行了修改,对机翼表面的结冰过程进行了更加准确的模拟,并应用了有效的离散算法计算水膜流动和结冰增长过程。对比了二维NACA0012翼型的单步法、多步法计算结果和实验结果。明冰结冰温度较低时,本文计算结果与实验结果吻合很好,明冰结冰温度较高时,本文对上冰角的计算与实验结果有一定差距。本文提供了三维GLC-305后掠翼的结冰计算结果和实验结果的对比,冰角厚度的计算结果略小于实验结果,但整体趋势一致。     

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.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.