Experimental Performance Characterisation and Measurement of Unstart Force on a Scramjet Intake across the Operational Envelope

该项目属于EPSRC流体力学和空气动力学研究领域。简介高超声速飞行器以超过5马赫的速度飞行，正在开发用于进入太空、民用运输和国防目的的飞行器。为了提高任务能力，吸气式发动机比基于火箭的系统更受青睐，因为它们不携带任何氧化剂。对于马赫5及以上，唯一可行的系统是旋转爆震发动机(RDEs)或超音速燃烧冲压发动机(超燃冲压发动机)。它们都依赖于超音速进气性能，以最小的损失压缩输入的空气。大多数进气口的设计假设在单一设计点的稳态运行，但预计将在一系列飞行条件和姿态下运行。瞬时变化会对进气的整体性能产生不利影响，这可能会导致发动机熄火或无法启动。在洛克希德公司SR-71“黑鸟”飞机的研制过程中，单一引擎的不启动会产生重要的偏航时刻，在某些情况下会导致飞行器的损失。已经有了大量的学术研究，目的是开发预测控制策略来减轻或防止不启动。然而，关于超燃冲压发动机进气道在不启动过程中产生的力的大小，实验数据有限。在多引擎配置中，所产生的力是否足以导致车辆损失或相邻引擎故障，仍然是一个悬而未决的研究问题。项目目的拟议的DPhil项目的主要目标是在一系列条件下对超燃冲压发动机进气未启动时施加给飞行器的力进行实验研究。此外，该项目还将探索车辆姿态对进气性能的影响以及低焓测试和高焓测试之间的差异。方法本研究将主要是实验，使用牛津高密度隧道(HDT)进行低焓测试，使用昆士兰大学反射激波隧道X3R进行高焓测试。此外，该项目将使用一种名为MassCap的设备，这是牛津大学开发的一种新型质量流量测量和机械背压设备，专门用于短期设施中的高速进气测试。第一年的大部分时间将专门用于进气口的设计。在第二年，实验进气模型将被制造出来，并在HDT上进行实验表征。该设施将在Palm模式(具有延长测试时间的模式)下运行，以便能够调查启动/不启动周期。在DPhil的第三年，使用相同模型的实验将在昆士兰大学的激波隧道设施中进行，在飞行焓条件下进行。通过这种方式，可以检查由于高焓效应引起的进气性能的变化，为飞行性能提供更好的评估。进气性能将在整个飞行包线中被表征。进气不启动过程中轴向力的测量将是独一无二的，并提供对整个车辆的影响的洞察力。还将研究性能随姿态的变化、进气口对不启动的敏感性以及自启动能力。将使用高速纹影照相术检查启动/非启动过程中的外部激波结构，并将探索使用压敏涂料和红外热像仪来分别提供表面压力和热通量的更高空间分辨率。在整个项目中，学生将与牛津高超声学小组的其他学生和工作人员以及外部学术、政府和行业合作伙伴进行互动，例如昆士兰大学高超声学中心。

This project falls within the EPSRC Fluid dynamics and aerodynamics research area.IntroductionHypersonic vehicles travelling at over Mach 5 are in development for access to space, civil transportation, and defence purposes. To increase mission capability, air-breathing engines are favoured over rocket-based systems as they do not carry any oxidiser. For Mach 5 and over, the only viable systems are Rotary Detonation Engines (RDEs) or Supersonic Combustion Ramjets (SCRamjets). These both rely upon supersonic intake performances to compress the incoming air with minimal losses. Most intakes are designed assuming steady-state operation at a single design point yet are expected to operate over a range of flight conditions and attitudes. Transient variations adversely affect the overall performance of the intake, which can result in either engine flame out or unstart. During the development of the Lockheed SR-71 'Blackbird' aircraft, the unstart of a single engine would produce a significant yawing moment that in some instances caused the loss of the vehicle. There has been significant academic investigation with the goal of developing predictive control strategies to mitigate or prevent unstart. However, there is limited experimental data on the magnitude of force generated during unstart for scramjet inlets. It remains an open research question as to whether the forces generated are sufficient to cause loss of vehicle or adjacent-engine failure in multi-engine configurations. Project AimThe primary aim of the proposed DPhil project is to experimentally investigate the forces imparted to a vehicle during the un-start of a scramjet intake over a range of conditions. Additionally, the project will explore the influence of vehicle attitude on intake performance and differences arising between low and high-enthalpy testing.MethodologyThis study will be primarily experimental, using the Oxford High-Density Tunnel (HDT) for low-enthalpy tests and the University of Queensland reflected shock tunnel facility X3R for high-enthalpy tests. Additionally, the project will use a device called MassCap, which is a novel mass flow measurement and mechanical back-pressurisation device developed at Oxford specifically for high-speed intake testing in short-duration facilities.The bulk of the first year will be dedicated to the design of an intake. During the second year, the experimental intake model will be manufactured, and experimentally characterised in the HDT. This facility will be operated in PALM mode (a mode with extended test times) to enable the start/un-start cycle to be investigated. In the third year of the DPhil, experiments using the same model will be undertaken in the University of Queensland shock tunnel facility at flight enthalpy conditions. In this way, changes in the inlet performance due to high enthalpy effects may be examined, providing a better assessment of the performance in flight.The inlet performance will be characterised throughout the flight envelope. Measurement of the axial force induced during inlet unstart will be unique and offer insight into the impact on the overall vehicle. The change in performance with attitude, sensitivity of the intake to unstart and self-starting capability will also be investigated. High-speed Schlieren videography will be used to examine the external shock structure during starting/un-starting and the use of pressure-sensitive paint and infrared thermography to provide an improved spatial resolution of the surface pressure and heat flux (respectively) will be explored. Throughout the project, the student will interact with other student and staff members within the Oxford hypersonics groups as well as external academic, government, and industry partners, such as at the University of Queensland Centre for Hypersonics.