激光辐射下AP/HTPB复合推进剂低压燃烧特性数值模拟

为了研究激光辐射对AP/HTPB复合推进剂低压燃烧的作用机理，建立二维三明治稳态燃烧模型进行数值仿真研究。针对激光辐射强度1.4W/mm²，压强30～90kPa的工况下推进剂的燃烧进行仿真计算，并与130～160kPa压强下自持燃烧的仿真结果进行差异分析。结果表明，激光助燃工况下，仿真计算所得燃速与实验基本一致，最大误差不超过4.2%。在激光助燃和自持燃烧工况下，组分扩散速度快，气相火焰均为预混结构。激光助燃工况下，激光辐射的能量使得近燃面处的反应比较充分，初扩散反应在气相反应中占主导地位，气相火焰高温区域离燃面近；自持燃烧工况下，AP预混反应和初扩散反应共同主导气相反应过程，气相火焰温度在垂直于燃面方向上增长缓慢且高温区域离燃面远。激光助燃比自持燃烧时的压强指数低，推进剂燃烧对压强的敏感性较弱。     

AP/HTPB推进剂组分热分解特性及其匹配关系对推进剂燃速的影响

本文应用差示扫描量热——热重(DSC—TG)技术研究了TMO(过渡金属氧化物)对过氯酸铵(AP)、端羟基聚丁二烯(HTPB)固化胶片热分解反应动力学参数(如活化能E、反应温度T、反应速度常数K、以及热分解速率等)的影响.测定了AP/HTPB/TMO推进剂的燃速.考察了组分热分解动力学参数与推进剂燃速的关系.结果表明,TMO对AP热分解特性和推进剂燃速的影响不是等效的,TMO对HTPB固化胶片的热分解基本无催化作用.由凝聚相燃烧模型进行理论分析发现,若要推进剂维持稳态燃烧,则氧化剂的热分解速率(r_(ox))、热着火延迟时间(t_(ign))与粘合剂的热分解速率(r_f)之间必须具备一定的匹配关系:rox(1-t_(ign)/t)/r_f≤1.推进剂试样的中止燃烧电镜照片验证了这一理论分析的正确性.     

固体推进剂二维绝热微尺度燃烧模型的数值研究

为实现固体微推力器工作过程的一体化模拟,基于Fluent计算软件的二次开发功能(UDF)和简化化学动力学模型,实现了固体推进剂的二维气-凝相绝热微尺度燃烧模型的建立,该模型针对固体微推力器所用双基推进剂,包含两步凝相反应和五步气相反应,燃速、推进剂表面温度和组分质量分数基于燃面物理特性计算得到,并考虑了粘性作用对气相和凝相反应的影响。针对0.5MPa,1.0MPa,2.0MPa和5.1MPa四种工况进行了计算,结果表明,高压工作环境下出现发光火焰区,且随表面压力增大而逐渐靠近壁面,凝相反应区厚度和嘶嘶区、暗区主要反应物在燃面的质量分数随推进剂表面压力增大而减小。对称面处推进剂燃速,推进剂表面温度和气相火焰结构与实验结果基本一致。由于壁面附近较高的粘性作用,气相火焰在壁面位置更加靠近推进剂燃面,并导致壁面位置推进剂燃速高于对称面位置。该模型实现了二维环境下考虑分步凝相反应的推进剂绝热燃烧模型的一体化计算,较好地拓展了原模型的应用范围。     

过渡金属氧化物催化作用的表征

本文系统地研究了TMO(过渡金属氧化物)对AP热分解性能和AP/AI/HTPB推进剂燃速的催化作用.结果发现,TMO对AP热分解反应和AP/AI/HTPB推进剂燃速的催化作用是一致的.文中指出了与AP热分解反应和AP/AI/HTPB推进剂燃速同时有关的表征参数,为采用热分析实验预估含铝推进剂的燃速奠定了基础.     

AP/HTPB复合推进剂低压燃烧特性数值研究

为研究AP/HTPB复合推进剂低压燃烧特性,使用二维三明治模型进行了数值仿真研究。该模型使用简化的四步总包反应机理,考虑燃烧过程中的燃面退移,计算时大粒径AP取平均粒径,小粒径AP采用“均质黏合剂假设”,认为其与HTPB组成“均质黏合剂”。在0.02MPa-0.08MPa的压强下进行了仿真,并与高压（5MPa）下的燃烧仿真进行对比。结果表明,低压下固相AP对黏合剂的传热导致了交界面处燃面的下陷,下陷程度随压强减小而增大;随着燃烧的进行燃面各点燃速趋于一致,燃面形状不再改变。低压下气相反应表现为预混燃烧,初焰为主导反应。低压下燃速仿真与实验值基本一致,压强指数小于高压下的压强指数。     

储氢合金/AP/HTPB推进剂燃烧性能研究

制备了Al/AP/HTPB推进剂和储氢合金/AP/HTPB推进剂,并对它们进行了DSC,PDSC,爆热和燃速测试.DSC和PDSC测试结果表明,储氢合金对AP/HTPB推进剂的凝聚相反应有催化作用,在0.1MPa和5MPa下,使其凝聚相主分解温度分别降低21.67℃和15.67℃,凝聚相反应热分别提高105.97％和21.87％;爆热测试结果表明,储氢合金对AP/HTPB推进剂的气相反应有催化作用,使气相反应热提高4.74％;燃速结果表明,储氢合金可以提高AP/HTPB推进剂的燃速.进一步研究表明,A1/AP/HTPB推进剂和储氢合金/AP/HTPB推进剂的燃速与爆热存在一定的相关性.总结出了燃速-爆热关系式.     

NEPE推进剂的高压燃烧特性研究

应用高压燃速测试、微热电偶测温及燃烧火焰单幅摄影等技术,研究了NEPE推进剂的高压燃烧特性与燃烧机理。实验结果表明:NEPE推进剂高压压强指数出现拐点;且随压强以及AP含量升高,燃烧波由硝胺-CMDB向AP-CMDB推进剂转变。分析认为硝酸酯基的含量及AP单元推进剂的扩散火焰是控制NEPE推进剂燃速及压强指数的主要因素。     

纳米铝粉和镍粉对复合推进剂燃烧性能的影响

对铝含量较低的AP复合推进剂燃速进行测试，外加2％的n-Ni或4/1的n-Al/g-Al级配均可提高低压下燃速和降低燃速压强指数，改善推进剂的燃烧性能，而采用1/1的n-Al/g-Al级配则降低推进剂的燃烧性能。通过对推进剂样品的能量特性、火焰结构、燃烧残渣的观测以及热分析(TG和DTA实验)，n-Al与n-Ni在燃烧中有不同于g-Al的行为。具有较低的点火阈值和较短的燃烧时间，同时n—Al倾向于单颗粒燃烧，有别于g-Al的凝聚燃烧行为；n-Ni则催化了复合推进剂中主要组分AP的热分解，多种因素共同作用促进了推进剂的燃烧。     

丁羟推进剂燃速计算图象法

本文用PEM模型编制的燃速计算程序,计算了一定压力,一定过氯酸铵(AP)粒径级配条件下不同配方的燃速,求出配方组分与燃速关系方程,绘制出AP/Al/HTPB系统的等燃速三角图,在图中由配方组分可迅速查找出燃速,也可由给定的燃速选择合适的配方.     

含铝复合固体推进剂的燃烧模拟计算

本文以我们提出的AP/HTPB推进剂的稳态燃烧模型为基础,对多级配AP/Al/HTPB推进剂的燃速和压力指数进行了模拟计算,并对铝粒径、铝含量对燃速和压力指数的作用规律及其机理作了说明。计算结果和实验符合得很好,相对误差小于10％的达90％以上,能满足定量予估的要求。      

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.