耐高温抗激光烧蚀涂层研制与性能表征

以有机硅树脂、聚碳硅烷和玻璃粉为黏结剂,添加Al2O3,BN,SiC,ZrO2,SiO2和碳纤维等耐热填料制备了抗烧蚀涂层,对其物理机械性能进行了表征,同时分别采用马氟炉、氧乙炔焰烧蚀对其耐热抗烧蚀性能进行了表征。研究结果表明:玻璃粉、BN对改善涂层裂纹起关键作用,ZrO2对提高涂层隔热和耐烧蚀性能至关重要。所研制涂层在厚度为1mm的30CrMnSiA钢基材表面涂覆600μm,经受3000℃氧乙炔焰4s烧蚀,钢基材不发生穿孔;900μm厚度的涂层在531W/cm2激光功率密度下照射4s,带涂层钢基材背面温度比同等辐照温度下,空白钢板背面温度下降1000℃左右。     

酚醛树脂基泡沫碳材料的烧蚀与隔热性能

为考察纳米孔径的酚醛树脂基泡沫碳材料的烧蚀与隔热性能,以酚醛树脂为碳源,环戊烷为发泡剂,吐温80为表面活性剂,对甲苯磺酸为固化剂,采用发泡固化碳化工艺制备了低密度泡沫碳材料。所制备的泡沫碳材料密度为0. 3 g/cm^3,压缩强度达到了11. 7 MPa。采用LFA457激光导热仪考察了泡沫碳材料在不同温度下(25、200、400、600℃)的导热性能,25℃下热导率为0. 141 W/(m·K),600℃下热导率为0. 344 W/(m·K);通过氧乙炔试验(30 s/60 s)对泡沫碳材料与C/C复合材料在同样的气流条件下隔热性能进行了比较,在材料正面烧蚀峰值温度泡沫碳材料比C/C复合材料高出约400℃的情况下,背面峰值温度比C/C复合材料仍低出150℃;通过氧乙炔试验考察泡沫碳材料的抗烧蚀性能,氧乙炔烧蚀60 s的线烧蚀率为0. 031 mm/s。试验结果证明低密度的泡沫碳材料同时具备优异的隔热与高温抗烧蚀性能。     

RTM型耐烧蚀酚醛树脂性能研究

对一种可用于RTM工艺的酚醛树脂的成型工艺性能和浇铸体性能进行研究,采用流变性能测试、热失重分析、氧-乙炔烧蚀等方法进行表征。结果表明:树脂的低黏度平台(≤800 mPa·s)长,且65~80℃的适用期均大于2 h;树脂浇铸体在800℃N2氛围下残碳率为61.38%,线烧蚀率和质量烧蚀率分别为0.167 mm/s和0.065 4 g/s。说明这种树脂可用作RTM注射成型且适合作为烧蚀防热复合材料的基体。     

2D C/SiC-ZrB2复合材料的烧蚀性能

用ZrB2微粉对2D C/SiC基体进行改性,研究了化学气相渗透结合浆料浸渍及先驱体浸渍裂解工艺制备2DC/SiC-ZrB2复合材料在氧-乙炔焰和1800℃甲烷风洞环境中的烧蚀行为.结果表明:在氧-乙炔环境中,2D C/SiC-ZrB2的线烧蚀率和质量烧蚀率分别为6.1×10-2 mm/s和1.0×10 -2g/s,相对2D C/SiC复合材料而言,ZrB2微粉并没有提高C/SiC复合材料的抗烧蚀性能.在1800℃甲烷风洞环境中,涂层致密度起主要作用,涂层致密度相同时,复合材料的开气孔率越大,质量烧蚀率越大,ZrB2微粉的渗入对C/SiC复合材料的烧蚀性能影响不大.     

耐烧蚀防热隔热涂层的研制

根据某大型固体火箭发动机的飞行工作特性,在研究涂层的防热隔热机理的基础上,采用环氧改性有机硅树脂为基体树脂,加入耐温梯度分解混合填料及添加剂等制备了一种外防热涂层,并通过L9(33)正交实验确定了无机混合填料组分多聚磷酸铵、氢氧化铝和硼酸的最佳用量分别为4份、6份、3份.最后确定的涂层最佳配方试验结果:线烧蚀率为0.116 mm/s,热导率为0.28 W/(m·K),密度为1.28 g/cm3,附着力为11.84 MPa,表明该涂层具有良好的防热隔热性能且综合性能优良,满足了该固体火箭发动机的外部防热需求.     

C/C复合材料在再入模拟环境中烧蚀性能研究

为了研究轴棒法编织的高密度碳/碳(C/C复合材料在再入飞行时的烧蚀性能,采用热等离子体地面模拟再入烧蚀系统对C/C复合材料进行烧蚀试验。试验中分别采用氮气(N、氧气(O和空气作为工作气体,对比研究C/C复合材料在不同环境中的烧蚀率和烧蚀性能。结果表明,三种情况下试样的烧蚀率和微观形貌有很大差异;纯氧气时氧化反应的线烧蚀率和质量烧蚀率分别为0.0423mm/s和0.0451g/s大于纯氮气时氮化反应的0.0314mm/s和0.0338g/s也大于空气成分时复合反应的0.0215mm/s和0.0208g/s在试样烧蚀的热影响区发生轻微开裂;三种工况下的烧蚀机理不同,分别是碳的升华、碳的氧化和碳氮反应的某种组合。     

CVD-SiC阵列结构对ZrB2/SiC涂层抗烧蚀性影响

采用飞秒激光在化学气相沉积(CVD)-SiC中间层表面制备不同尺寸的阵列,研究了阵列结构对ZrB₂/SiC涂层性能的影响。结果表明,随着激光刻蚀频次的增大,阵列结构的深度从30μm增大到150μm。采用氧乙炔烧蚀600 s,ZrB₂/SiC涂层烧蚀表面温度随CVD-SiC微结构深度增大而逐步降低,最低的表面温度达到1 700°C,下降了约200℃。烧蚀中心区域的颜色从白色过渡到浅灰色。对于激光刻蚀频次为5的试样,在600 s的单次烧蚀后,质量烧蚀率和线性烧蚀率分别为-7.4×10^-5 g/s和-13.3μm/s。阵列结构增大了ZrB₂/SiC涂层与CVD-SiC中间层的接触面积,从而增强了导热性能,减少了热积聚,进而改善了ZrB₂/SiC涂层的抗烧蚀性能。     

轴棒法编织C/C复合材料的超声速火焰烧蚀性能

为了研究轴棒法编织、高压浸渍-碳化致密工艺(HPIC)及高温处理工艺制成的高密度的碳/碳(C/C)复合材料在火箭发动机中的烧蚀性能,使用气氧和煤油超声速(HVO)火焰对复合材料进行含铝工况烧蚀/侵蚀实验,烧蚀时间为30s;对比研究了复合材料在有、无含铝粒子侵蚀时烧蚀性能的差别;分别用扫描电镜、微CT和表面能谱分析了不同工况烧蚀表面的形貌和成分。结果表明,在不同的烧蚀工况下,材料的表面粗糙度不同,微观形貌和烧蚀率也有很大差异;复合材料在无粒子侵蚀工况下的线烧蚀率和质量烧蚀率的平均值分别是0.0318mm/s和0.0319g/s,烧蚀表面呈竹笋状和毛絮状,热化学烧蚀起主导作用;有粒子侵蚀时的线烧蚀率和质量烧蚀率的平均值分别是0.0516mm/s和0.0353g/s,烧蚀表面呈钝竹笋状,纤维从根部断裂,热化学烧蚀和机械剥蚀同时起作用;在纤维和基体表面有Al2O3粒子沉积;含铝烧蚀/侵蚀的线烧蚀率是不含铝烧蚀的1.6倍,质量烧蚀率的1.1倍。在烧蚀区的内部,基体碳受热后开裂,而碳纤维与基体碳间的界面相受热后无明显变化。     

功能涂料及多功能广用途改性剂

<正>1梯度功能轻质烧蚀涂料(1)T-98烧蚀涂料(2)TH-120轻质烧蚀涂料(3)TH-80烧蚀涂料(4)TH-60烧蚀涂料(5)THD-1室温固化烧蚀涂料以上涂料的固化温度有180、120、80、60℃及室温等,其线烧蚀率为-0.3-0.0496 mm/s,质量烧蚀率为78.8-40 mg/s,并且无烟。它们的密度有1.2、0.8、0.4及0.22 g/㎝3,可按设计要求调整。相应的热导率为0.45、0.14、0.08及0.055 W/(m.K)。通过防热专业的理论计算,可以获得很好的烧蚀性和隔热性能。     

CVD-SiC 涂层的C/ C-SiC 复合材料的抗烧蚀性能

采用CVD法,1 050℃在三维针刺C/C-SiC复合材料表面制备SiC涂层,研究稀释气体与载气流量比分别为4∶1和2∶1制备条件下涂层的晶体结构、表面和断面的微观形貌,对比了涂层前后C/C-SiC复合材料的抗烧蚀性能.结果表明:稀释气体流量降低其制备的SiC涂层更加平整致密,与基体结合程度更好,沉积产物均为单一的β-SiC结晶相.在600 s的氧化烧蚀下,两种流量比条件下制备CVD-SiC涂层的C/C-SiC复合材料的线烧蚀率比未涂层的分别降低34％和50％,质量烧蚀率分别降低70％和75％,抗氧化烧蚀性能明显提高.     

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.