Fabrication of Porous Ultra-high Temperature Ceramics for Transpiration Cooling of Hypersonic Vehicles.

用于高超声速飞行器蒸发冷却的多孔超高温陶瓷的制造。

• 批准号: 2131760
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2131760
• 关键词: Fabrication; Porous; Ultra; Temperature; Ceramics

Ultra-high temperature ceramics (UHTCs) are to be examined for their use in transpiration cooling systems for the leading edges of hypersonic vehicles. Previous thermal protection systems (TPS) for applications such as atmospheric re-entry have tried to minimise the effect of aerodynamic heating by having a large radius of curvature for the leading edge [1]. This is effective at reducing the heating of the vehicle but is detrimental to manoeuvrability. These shields would also rely on ablative cooling, a process by which the protective material is removed, effectively removing heat from the protected vehicle but is only suitable for single use [1].To design a sharp leading edge, which is also reusable, the TPS must be able to withstand up to 2000C without sustaining damage. Only UHTCs are capable of sustaining such temperatures [2]. The TPS to be tested is transpiration cooling, a process by which a cooling gas flows through the exposed outer layer. This both cools the material internally and provides a protective fluid layer at the surface [1].Transpiration cooling requires a material that allows for fluid flow while maintaining structural stability, the fabrication of which will be the primary focus of the current work. Different methods for creating internal channels in zirconium diboride will be assessed. Currently the creation of porous zirconium diboride by partial sintering has been shown to allow for sufficient fluid flow for transpiration cooling [1]. Following work will now be to probe parameters controlling coarsening and densification of zirconium diboride, with the aim to produce a porous material which will not then densify at application temperatures of 2000C. Characterisation of materials will involve use of dilatometry to assess densification at high temperature, while material properties such as thermal conductivity, strength, and permeability will be used to assess suitability of materials.Additionally, work will involve combining the porous skin with a dense, channelled, substructure for efficient and controlled delivery of cooling fluid, as well as providing structural reinforcement. Also made from zirconium diboride, optimisation of channel size and spacing will be investigated. Manufacturing methods such as pressureless sintering, robocasting, and gel casting are to be assessed for their suitability for the design and development of an effective transpiration cooling system.[1] Rocher, M.E, et al., "Testing a Transpiration Cooled Zirconium-Di-Boride sample in the Plasma Tunnel at IRS." AIAA Scitech 2019 Forum, 2019.[2] Fahrenholtz, W.G, & Hilmans, G.E. "Ultra-high Temperature Ceramics: Materials for extreme environments." Scripta Materialia, 129, 94-99 2018.

将检查超高温陶瓷（UHTC）在高超音速飞行器前缘蒸发冷却系统中的应用。以前用于重返大气层等应用的热保护系统 (TPS) 试图通过前缘的大曲率半径来最小化气动加热的影响 [1]。这可以有效减少车辆的热量，但不利于机动性。这些防护罩还依赖于烧蚀冷却，这是一种去除保护材料的过程，可有效去除受保护车辆的热量，但仅适合一次性使用 [1]。为了设计可重复使用的锋利前缘，TPS 必须能够承受高达 2000C 的温度而不造成持续损坏。只有 UHTC 能够承受这样的温度 [2]。待测试的 TPS 是蒸腾冷却，即冷却气体流过暴露的外层的过程。这既可以在内部冷却材料，又可以在表面提供保护性流体层[1]。蒸腾冷却需要一种允许流体流动同时保持结构稳定性的材料，其制造将是当前工作的主要焦点。将评估在二硼化锆中创建内部通道的不同方法。目前，通过部分烧结制造多孔二硼化锆已被证明可以提供足够的流体流动以进行蒸发冷却[1]。接下来的工作将是探索控制二硼化锆粗化和致密化的参数，目的是生产一种在 2000°C 的应用温度下不会致密化的多孔材料。材料的表征将涉及使用膨胀测量法来评估高温下的致密化，同时使用导热性、强度和渗透性等材料特性来评估材料的适用性。此外，工作还将涉及将多孔蒙皮与致密的通道式下部结构相结合，以实现冷却液的高效和受控输送，以及提供结构加固。同样由二硼化锆制成，将研究通道尺寸和间距的优化。将评估无压烧结、机器人铸造和凝胶铸造等制造方法是否适合设计和开发有效的蒸发冷却系统。 [1] Rocher, M.E 等人，“在 IRS 的等离子隧道中测试蒸腾冷却二硼化锆样品。” AIAA科技2019论坛，2019.[2] Fahrenholtz, W.G, & Hilmans, G.E. “超高温陶瓷：适用于极端环境的材料。”材料脚本，129, 94-99 2018。