Transpiration Cooling for Sharp Leading Edges on Hypersonic Vehicles

通常，高速车辆被设计成具有光滑的车身，以获得空气动力学效率，并避免由台阶、空腔和间隙引起的热点。然而，在实际的飞行器中，这些是不可避免的，原因有很多，包括：-允许不同部件之间的热膨胀-例如航天飞机上的热防护系统的瓦片-控制表面的致动-包括仪器-例如用于飞行器的数据传输和引导-制造和连接不同部件的公差-发射和级分离期间的连接点-分离可展开部件所需的接口入门飞行器设计通常是保守的，优选简单的几何空气动力学形状。然而，由于上述原因，可能需要间隙、界面和突起。车辆表面上的这种特征会导致各种影响，例如局部加热速率增加和过早的边界层转变。这样的流动很难分析，这意味着任何设计过程都需要有很高的安全裕度。目前，只有基本的经验法则来确定间隙、界面和突起的尺寸，使它们在气动热力学效应方面不显着。最常见的是，这些特征的大小与预期的边界层长度尺度有关，并不总是适用于真正的飞行器。本项目的目的是扩展现有的知识库，使之包括在飞行过程中预期的条件下这些表面特征对飞机机身上的流动的影响的更一般的规律。扩展可用数据库和工程级相关性的库将使这些领域的考虑能够在早期设计阶段更准确地解决，最终导致在后期阶段携带更少的设计裕度。实验测试将在牛津热流体研究所的高超音速测试设施中进行，该研究所在欧洲具有进行高雷诺数和传热实验的独特能力。数值模拟将主要发生在流体重力工程（FGE）谁将与该项目的大学合作。FGE是欧洲高速进入飞行器数值模拟工具开发和应用的领导者。实验将包括简化飞行器模型（例如平板或锥体）的气动热力学测试，这些模型具有不同配置的台阶、间隙和突起。模型将高度仪表化，用于研究各种流动效应，如感兴趣区域的传热和表面压力变化。这些实验的结果将用于产生开放的通用相关性，然后可以将其纳入软件中进行数值模拟，并用于真实的车辆的设计。该项目属于EPSRC流体动力学和空气动力学研究领域的福尔斯。

Typically, high speed vehicles are designed with smooth bodies for aerodynamic efficiency and to avoid hot spots incurred from steps, cavities and gaps. However, there are many reasons why in a practical vehicle these are unavoidable including:- Allowance for thermal expansion between different components - for example the tiles of the thermal protection system on the Space Shuttle- Actuation of control surfaces- Inclusion of instrumentation - for example for data transmission and guidance of the vehicle- Tolerance in manufacture and joining of different components- Attachment points during launch and separation of stages- Interfaces that are required for separation of deployable componentsEntry vehicle design is usually conservative with simple geometric aerodynamic shapes being preferred. However, gaps, interfaces and protuberances may be necessary due to the reasons outlined above. Features like this on the surface of the vehicle can cause various effects such as increased localised heating rates and premature boundary layer transition. Flows like this are difficult to analyse, meaning that any design process needs to carry high safety margins.Currently, only basic rules of thumb exist for sizing gaps, interfaces and protuberances such that they will not be significant in terms of aerothermodynamic effects. Most commonly, these relate the size of the feature to expected boundary layer length scales and are not always applicable to true flight vehicles.The aim of this project is to extend the current knowledge base to include more general laws for the effect that these surface features have on the flow over an aircraft body at the conditions expected during flight. Extending the library of available databases and engineering level correlations will enable consideration in these areas to be addressed more accurately in early design stages, ultimately leading to carrying less design margin in later phases. This will be achieved by combining experimental testing with numerical simulations.The experimental testing will take place in the hypersonic test facilities at the Oxford Thermofluids Institute which have unique European capabilities to perform high Reynolds number and heat transfer experiments. Numerical simulations will primarily take place at Fluid Gravity Engineering (FGE) who will be working in collaboration with the University for this project. FGE is a European leader in the development and application of numerical simulation tools for high speed entry vehicles.Experiments will consist of aerothermodynamic testing of simplified vehicle models (for example flat plates or cones) featuring steps, gaps and protuberances in different configurations. Models will be highly instrumented for the investigation of various flow effects such as heat transfer and changes in surface pressure in areas of interest. Results from these experiments will be used to produce open generic correlations which can then be included into software for carrying out numerical simulations where they can be used in the design of real vehicles. This project falls within the EPSRC Fluid Dynamics and Aerodynamics research area.