飞行器复杂外结构的环境热流计算方法

提出了一种通用的、适合飞行器复杂外结构环境热流的计算方法。采用由环境映射面组成的封闭结构对空间飞行器进行包覆,根据飞行器的轨道特征及瞬时位置,确定映射面上环境热流的大小及方向。在映射封闭结构与飞行器表面组成的辐射换热系统中,通过蒙特卡罗法结合设备表面的镜、漫反射特性,计算环境映射面到各设备表面的辐射传递因子,进而获得在轨飞行器不同位置的瞬时环境热流。计算中考虑了结构表面间的遮挡及多次反射问题,解决了空间飞行器因设备众多、尺寸差异大、表面辐射特性不同等给热流计算带来的困难,并为后期的热分析计算提供精确数据。
     

LEO卫星网络中无缝切换管理技术研究

针对低地球轨道(LEO)卫星网络中采用移动IPv6(MIPv6)协议带来切换延时长,丢包率高的缺点,本文提出了一种基于MIPv6协议的简单卫星代理本地转发策略。通过解除MIPv6协议中切换过程与位置注册消息交换过程的耦合关系,显著降低了切换延时和切换丢包率。仿真结果表明,新策略与MIPv6协议相比,丢包率降低达75%以上。     

富氢/富氧燃气同轴双剪切气-气喷嘴性能仿真分析

为研究富氢/富氧燃气同轴双剪切气-气喷嘴设计参数对燃烧性能和燃烧室热载的影响,采用正交试验设计方法对这些参数进行组合,数值模拟单喷嘴燃烧室流场,并以燃烧长度、燃烧室壁面和喷注面板处平均燃气温度为指标评价燃烧性能和热载.结果表明:燃氧速度比对燃烧性能和燃烧室热载影响最显著,中心氢流量比例对燃烧室热载影响非常显著,氧压降比对喷注面板处燃气平均温度的影响也很显著,而喷嘴出口壁厚对喷嘴性能影响不明显.燃氧速度比和氧压降比的交互作用对喷嘴性能有一定影响,而其他设计参数之间的交互作用对喷嘴性能影响非常小.最短燃烧室长度为117.9mm,最低壁面燃气温度及面板燃气温度分别为1637.7K和806.6K.      

BPM授时信号传输损耗的仿真建模

为了适应BPM发播系统升级改造,需要远场监测BPM授时信号的场强,因此有必要研究短波信道传输损耗,建立适当的计算模型。通过分析现有传输损耗理论模型,综合考虑地波、天波对BPM授时信号传输损耗的影响,在Labwindows/CVI开发环境下设计了BPM授时信号场强预测软件。通过将预测值与实测值比较,表明了该软件的可行性和准确性,可用于BPM授时信号场强的远场监测。     

含湿气流单缝冲击冷却数值模拟

对饱和湿空气夹带液滴的含湿气流单缝冲击冷却进行了数值模拟,比较研究了含湿气流中液滴相变换热/液滴载量比和单缝射流几何参数对强化换热效果的影响,研究发现:气流中液滴的加入对冷却效果的影响十分显著,热流密度为8000W/m2的条件下,空气中注入5%的液滴会比饱和湿空气对驻点区的冷却效果提高90%,当液滴载量比从1%提高到5%,冲击驻点区局部传热系数提高了32%;而合适的缝宽和冲击高度也是影响冷却效果的重要因素,在该条件下冲击高度与缝宽的比值为4.55时冲击冷却效果最佳.      

可调静子旋转凸台位置对端区流动的影响

对包含凸台的可调静子模型进行简化,研究了不同凸台位置对端区流动的影响.通过实验测量与数值模拟对比可以发现:可调静子端区流动损失主要是由叶片气动负荷引起的泄漏及气流绕过凸台造成的掺混2个部分组成;通过合理优化设计,将凸台置于气动负荷高的叶片前缘并覆盖尽可能多的前缘间隙,能够有效降低损失,改善气动性能.      

Modeling and Optimal Design of 3 Degrees of Freedom Helmholtz Resonator in Hydraulic System

Three degrees of freedom (3-DOF) Helmholtz resonator which consists of three cylindrical necks and cavities connected in series (neck-cavity-neck-cavity-neck-cavity) is suitable to reduce flow pulsation in hydraulic system. A novel lumped parameter model (LPM) of 3-DOF Helmholtz resonator in hydraulic system is developed which considers the viscous friction loss of hydraulic fluid in the necks. Applying the Newton’s second law of motion to the equivalent mechanical model of the resonator, closed-form expression of transmission loss and resonance frequency is presented. Based on the LPM, an optimal design method which employs rotate vector optimization method (RVOM) is proposed. The purpose of the optimal design is to search the resonator’s unknown parameters so that its resonance frequencies can coincide with the pump-induced flow pulsation harmonics respectively. The optimal design method is realized to design 3-DOF Helmholtz resonator for a certain type of aviation piston pump hydraulic system. The optimization result shows the feasibility of this method, and the simulation under optimum parameters reveals that the LPM can get the same precision as transfer matrix method (TMM).     

火星气囊气体发生器充气过程稳压仿真研究

文章对低温和常温环境下的气囊稳压充气过程的参数进行了仿真计算。主要分析计算了气囊内外壁的对流换热、囊内气体与囊壁间辐射以及水蒸气液化等传热方式的传热量。同时,计算了在不同环境温度下,气囊内气体温度、充气质量以及充气质量流率随时间的变化关系。分析结果可以为工程研制提供参考和数据支持。     

5kN再生冷却发动机推力室传热研究

5 kN摇摆发动机推力室采用再生冷却身部,为检验推力室冷却方案设计的合理性,对5 kN再生冷却发动机推力室进行传热计算,分析了再生冷却的影响因素,并针对发动机设计提出了相应的改进措施,改进后的发动机热试车工作正常,表明了改进工作的有效性。     

A Dual-driven Intelligent Combination Control of Heat Pipe Space Cooling System

Effective thermal control systems are essential for reliable operation of spacecraft.A dual-driven intelligent combination control strategy is proposed to improve the temperate control and heat flux tracking effects.Both temperature regulation and heat flux tracking errors are employed to generate the final control action;their contributions are adaptively adjusted by a fuzzy fusing policy of control actions.To evaluate the control effects,describe a four-nodal mathematical model for analyzing the dynamic characteristics of the controlled heat pipe space cooling system(HP-SCS) consisting of an aluminum-ammonia heat pipe and a variable-emittance micro-electromechanical-system(MEMS) radiator.This dynamical model calculates the mass flow-rate and condensing pressure of the heat pipe working fluid directly from the systemic nodal temperatures,therefore,it is more suitable for control engineering applications.The closed-loop transient performances of four different control schemes have been numerically investigated.The results conclude that the proposed intelligent combination control scheme not only improves the thermal control effects but also benefits the safe operation of HP-SCS.