Numerical Simulation and Advanced Modelling of Hydrogen-Fuelled Propulsion Systems for Reusable Launch Vehicles

反应发动机有限公司（REL）是一家成立于1989年的英国公司，旨在设计和开发新型高超声速推进系统-协同吸气式火箭发动机（SABRE）的技术。REL的突破性技术是一种超轻型热交换器，通过防止发动机部件过热，使SABRE发动机能够在非常规的高速下使用传统的航空技术。SABRE技术将使飞行器在大气层中的飞行速度超过音速的五倍，并实现单级入轨航天运载火箭，降低成本并改善进入太空的途径。SABRE发动机成功的关键是使用氢作为燃料，在非常规条件下燃烧，这一点远未得到充分理解。在这些条件下的燃烧包括固有的不稳定性（热扩散，流体动力学和热声），对燃烧室设计提出了重大挑战。对这种世界领先的技术进行原型制作是非常昂贵的，而数值模拟可以提供对这种新型燃烧室所涉及的基本物理过程的无与伦比的洞察力，从而有助于设计和开发过程。然而，现有的数值模拟已经证明了用于描述湍流混合和火焰物理的模型的敏感性;为了开发和验证可靠的湍流燃烧模型，以便用于燃烧室的设计和开发，我们需要进行高分辨率的数值模拟。2.方法学：一个高保真度的三维直接数值模拟（DNS）数据库将构造考虑到氢燃料直接喷射到亚音速横流中的湍流混合，以及随后在与SABRE相关的条件下的下游稀燃。NASA的低排放贫氢燃烧器将被用作目标测试用例，反应发动机将提供进一步的必要条件，可用于初始化。DNS计算将使用PeleLM（和PeleC，如果必要的话）进行，由加州的劳伦斯伯克利国家实验室开发，并建立在PI拥有超过15年经验的框架上。主要优点包括利用低马赫数近似和自适应网格更新，这两者都显著降低了计算费用，并针对并行超级计算机进行了优化，使其成为世界领先的湍流燃烧计算工具。模拟规模的增加将分阶段进行，从一个高规格的工作站开始，通过NU HPC设施“Rocket”，直到国家超级计算机“Archer”。DNS数据将被详细分析，以评估用于雷诺平均纳维尔-斯托克斯（RANS）和大涡模拟（LES）方法的现有湍流火焰模型，并酌情指导新模型的开发。这些模型将在工程CFD软件框架中实施和测试，并在与DNS模拟相同的情况下进行验证;这将允许进行直接比较并迭代模型开发，从而建立该方法的一致性，以便它可以更广泛地应用于帮助SABRE燃烧室技术的设计和开发。建议的研究领域：连续介质力学，燃烧工程，流体动力学和空气动力学，数值分析，氢和替代能源载体

1 OverviewReaction Engines Ltd (REL) is a UK-based company formed in 1989 to design and develop technologies for a new class of hypersonic propulsion system - the Synergetic Air-Breathing Rocket Engine (SABRE). REL's breakthrough technology is an ultra-lightweight heat exchanger that enables the SABRE engine to use conventional aerotechnology at unconventionally high speeds by preventing engine components overheating. SABRE technology will enable aircraft to fly over five times the speed of sound in the atmosphere, and realise single-stage-to-orbit space launch vehicles, reducing costs and improving access to space.Key to the success of the SABRE engine is using hydrogen as fuel, burning under unconventional conditions that are far from well-understood. Combustion at these conditions includes inherent instabilities (thermodiffusive, hydrodynamic and thermoacoustic) that pose signicant challenges to combustor design. Prototyping such world-leading technology is extremely expensive, and numerical simulation can provide unparalleled insight into the fundamental physical processes involved in such novel combustors, thereby aiding the design and development process. However, existing numerical simulations have demonstrated a sensitivity to models used to describe turbulent mixing and flame physics; there is a need for high-resolution numerical simulations to develop and validate reliable turbulent combustion models that can be used for combustor design and development.2 MethodologyA database of high-fidelity three-dimensional Direct Numerical Simulations (DNS) will be constructed that consider both the turbulent mixing of direct injection of hydrogen fuel into a sub-sonic cross-flow, and the subsequent downstream lean combustion at conditions relevant for SABRE. NASA's low-emission lean-hydrogen burner will be used as a target test cases, and Reaction Engines will provide further necessary conditions that can be used for initialisation.The DNS calculations will be carried out using PeleLM (and PeleC, if necessary), developed at the Lawrence Berkeley National Laboratory in California, and built on a framework with which the PI has over fteen years' experience. Key advantages include exploitation of the low Mach number approximation and adaptive mesh renement, both of which signicantly reduce computational expense, and is optimised for use on massively-parallel supercomputers, making it a world-leading computational tool for turbulent combustion. Simulations increasing in size will be carried out in stages, starting from a high-specication workstation, through the NU HPC facility "Rocket", up to the national supercomputer "Archer".The DNS data will be analysed in detail to assess existing turbulent flame models used for Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) approaches, and to guide development of new models as appropriate. The models will be implemented and tested in an engineering CFD software framework, and validated on the same cases as conducted for the DNS simulations; this will allow direct comparisons to be made and to iterate on the model development, thereby establishing the condence in the approach so that it can be applied more generally to aid the design and development of SABRE combustor technology.Suggested research areas: Continuum Mechanics, Combustion Engineering, Fluid Dynamics and aerodynamics, Numerical Analysis, Hydrogen and alternative energy vectors