用Nocilla模型计算卫星气动力系数和热流密度分布

本文用Nocilla粒子-表面作用模型计算卫星在运行轨道中整体气动力系数和星体表面热流密度分布,文中列出了详细计算公式和一个算例。     

尺度效应下大功率伺服电机再生冷却通道超临界态甲烷传热特性研究

针对飞行器电动执行机构的大功率伺服电机强化散热问题,建立了不同尺度的电机缠绕式螺旋管再生冷却通道数值模型,对超临界态甲烷在尺度效应影响下的传热特性和机理进行研究,探讨了不同尺度冷却通道中超临界态甲烷所受重力浮升力和离心浮升力对传热性能的影响.结果表明,离心浮升力及重力浮升力均受到超临界态甲烷热物性剧烈变化的影响;在相同...     

A swept fin-induced flow field with different height mounting gaps

In order to apply the air fin successfully and ensure the maneuverability of hypersonic vehicle, a key problem to be studied urgently is the heat flux brought by the fin mounting gap. The appearance of mounting gap and fin shaft can induce many complex flow structures which need more attentions to be investigated. Under Ma 6, Nano-tracer-based Planar Laser Scattering (NPLS) and Temperature Sensitive Paints (TSP) were applied to visualize and measure transient flow structures and heat flux distribution of a swept fin-induced flow field with different height mounting gaps. Complementarily, Reynolds-averaged N-S equations were solved with k-ω SST turbulent model. The heat flux distribution results of numerical simulation and TSP observed the change of high heat flux region with different mounting gap, both in position and magnitude. The streamlines based on Computational Fluid Dynamics (CFD) and flow visualization results obtained by NPLS revealed the cause of high heat flux region. The high heat flux region in this flow field is mainly related to the reattachment of vortex and flow stagnation. The increase of gap height can lead to stronger gap overflow and shaft-induced horseshoe vortex, which are source of the high heat flux around the fin. The case with the highest mounting gap (4 mm) en-counters the most severe aerodynamic heating, both on the surface of fin and plate. Thus, under the premise of ensuring the flexibility of the fin, the gap should be set as small as possible.     

Recent active thermal management technologies for the development of energy-optimized aerospace vehicles in China

Recently, the development of modern vehicles has brought about aggressive integration and miniaturization of on-board electrical and electronic devices. It will lead to exponential growth in both the overall waste heat and heat flux to be dissipated to maintain the devices within a safe temperature range. However, both the total heat sinks aboard and the cooling capacity of currently utilized thermal control strategy are severely limited, which threatens the lifetime of the on-board equipment and even the entire flight system and shrink the vehicle’s flight time and range. Facing these thermal challenges, the USA proposed the program of “INVENT” to maximize utilities of the available heat sinks and enhance the cooling ability of thermal control strategies. Following the efforts done by the USA researchers, scientists in China fought their ways to develop thermal management technologies for Chinese advanced energy-optimized airplanes and spacecraft. This paper elaborates the available on-board heat sinks and aerospace thermal management systems using both active and passive technologies not confined to the technology in China. Subsequently, active thermal management technologies in China including fuel thermal management system, environment control system, non-fuel liquid cooling strategy are reviewed. At last, space thermal control technologies used in Chinese Space Station and Chang’e-3 and to be used in Chang’e-5 are introduced. Key issues to be solved are also identified, which could facilitate the development of aerospace thermal control techniques across the world.     

Design of nanofluid-cooled heat sink using topology optimization

The paper presented topology optimization of 2D and 3D Nanofluid-Cooled Heat Sink (NCHS). The flow and heat transfer problem in the NCHS was treated as a single-phase nanofluid based convective heat transfer model. The temperature-dependent fluid properties were taken into account in the model due to the strong temperature-dependent features of nanofluids. An average temperature minimum problem was studied subject to the fluid area and energy dissipation constraints by using the density method. In the method, the design variable is updated according to the gradient information obtained by an adjoint based sensitivity analysis process. The effects of the energy dissipation constraint, temperature-dependent fluid properties and nanofluid characteristics on optimal configurations of NCHS were numerically investigated with following conclusions. Firstly, branched flow channels in the optimal configuration increased with the rise of the allowed energy dissipation. Secondly, temperature-dependent fluid properties were significant for obtaining the appropriate optimal results with best cooling performance. Thirdly, heat transfer performances of optimal configurations were enhanced by reducing the nanoparticle diameter or increasing the nanoparticle volume fraction. Fourthly, the optimal configuration for nanofluid had better cooling performance than that for its base fluid.     

Three dimensional temperature field in a conducting sphere due to an arbitrarily located split ring heating source

Thermal control of spacecrafts plays an important role in space missions. In the design stage the preliminary thermal analysis of the spacecraft requires an estimate of the conductive thermal resistance between the various spacecraft components. With this in mind, the fully three dimensional problem of determining the thermal field in a conducting sphere with an asymmetric split ring current carrying heating source is resolved in an analytical or almost analytical form, implying either a closed form solution or utmost expressions involving a simple numerical integration. This has immediate application for evaluation of thermal resistance in spacecrafts. Green's function integral techniques are used. Comparisons are made with series solutions and also with purely numerical solutions to contrast the simplicity and highlight the elegance of the present method. Parametric studies reveal expected behavior.     

基于区域热核不变量的SAR图像变化检测

快速精确地检测SAR图像的变化是SAR应用亟待解决的问题。针对这一问题,提出了基于区域热核不变量的SAR图像变化检测方法。该方法利用图上热核的特征,可以充分发挥图谱理论的优点,且计算简便、矩阵的扰动性小。通过模拟分析研究了热核的特征,并应用于实际SAR图像的变化检测。实验结果表明该方法可以快速精确地检测到变化区域,且其变化检测的精度要优于区域似然比检测方法。     

单相流体回路辐射器性能优化方法

文章以“神舟”飞船辐射器为例,对管肋式单相流体回路辐射器的肋宽进行了优化分析。采用理论分析与数值求解相结合的方法,分析了管肋式辐射器常用性能评价方法--能质比及微元能质比（单位质量散热能力）随肋片宽度的变化规律;而后以提高辐射器能质比为优化目的,对辐射器肋宽进行了优化,得出了辐射器的最佳能质比对应的肋宽表达式;最后给出了“神舟”飞船辐射器优化前后的参数对比。文章对管肋式辐射器的优化设计具有很好的参考价值。     

Preliminary study on heat flux measurement data of TT-0 flight test

With the explosive development of aerospace science, the design of the new generation airliner at higher speeds is attracting more attentions. To achieve this goal, it is necessary to achieve accurate prediction of the aerodynamic heating / force loads and successful reduction of drag and heat flux. As a remedy for the existing studies which are based upon the CFD and wind tunnel tests, this study presents a flight test for the drag and heat reduction spike technology. The principal goals of this flight test were to provide reference for verifying the accuracy of the prediction technology on ground and promote the development of the drag and heat reduction technology. By adopting the OS-X rocket, the TT-0 test vehicle designed by Shenyang Aircraft Design & Research Institute reached a maximum Mach number of 5.8 and a maximum altitude of 38 km. Hypersonic and supersonic pressure data by pressure scanning valves and heat fluxes by gauges at different locations were obtained successfully. Also, heat fluxes obtained by in-house CFD code are illustrated in comparison with the flight data. The results indicate that the numerical errors are large in most cases. More technologies, such as more CFD codes and more numerical procedures, should be adopted to conduct studies on this issue in the future.     

非均匀气动加热下隔热层结构的优化设计

为获得非均匀气动加热条件下高超声速飞行器不同部位的合适的热防护系统厚度,发展了一种基于网格变形技术（ASD）的隔热层结构优化方法。以高超声速飞行器的复合材料隔热层结构为研究对象,采用有限元法在局部均布热流载荷、三角形均变热流载荷和二次函数热流载荷等作用条件下建立隔热层结构的热固耦合分析模型,提出了基于ASD技术与热固耦合分析相结合的结构轻量化设计方法。结果表明,基于网格变形技术能够快速有效地解决优化过程中的网格自动更新问题,并得到了光滑柔顺的厚度形状曲线,优化后更充分发挥了隔热层结构各层材料的承载能力。