Transpiration Cooling for Sharp Leading Edges on Hypersonic Vehicles

通常，高速车辆的设计具有光滑的车身，以提高空气动力学效率，并避免因台阶、空洞和缝隙而产生的热点。然而，在实际飞行器中，这些是不可避免的有很多原因，包括：-允许不同部件之间的热膨胀-例如航天飞机上的热保护系统的瓦片-操纵面的驱动-包括仪器-例如用于飞行器的数据传输和制导-制造和连接不同部件的容差-发射和分离阶段的附着点-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，首选简单的几何气动形状。然而，由于上述原因，缝隙、界面和突起可能是必要的。车辆表面的这种特征可能会导致各种影响，如局部加热率增加和边界层过早转变。像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，只有基本的经验规则可以确定间隙、界面和突起的大小，因此它们在气动热力效应方面不会很明显。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，并不总是适用于真实的飞行器。本项目的目的是扩展现有的知识库，以包括更一般的规律，即这些表面特征对飞行过程中预期条件下的飞机机身绕流的影响。扩展现有数据库和工程级别的关联库将使这些领域的考虑能够在早期设计阶段得到更准确的处理，最终导致在后期阶段实现更少的设计余量。这将通过实验测试和数值模拟相结合的方式实现。实验测试将在牛津热流体研究所的高超声速测试设施中进行，该设施具有独特的欧洲能力，可以进行高雷诺数和热传导实验。数值模拟将主要在流体重力工程(FGE)进行，他们将与该大学合作开展这一项目。FGE在开发和应用高速进入车辆的数值模拟工具方面处于欧洲领先地位。试验将包括对简化的车辆模型(例如平板或圆锥体)进行气动热力测试，这些模型具有不同结构的台阶、间隙和突起。模型将被用来研究各种流动效应，如热传递和感兴趣区域的表面压力变化。这些实验的结果将被用来产生开放的通用关联，然后可以被包括在进行数值模拟的软件中，在那里它们可以用于真实车辆的设计。该项目属于EPSRC流体动力学和空气动力学研究领域。

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.