Transpiration Cooling for Turbine Cooling

燃气涡轮发动机的比功率从根本上受到涡轮燃烧温度的限制。人们逐渐采用更精密的方法，将其提高到发动机所用金属的熔点以上。冷却剂从压缩机级取出，用于将燃烧下游的热金属部件的温度降低到可接受的温度。冷却剂需要压缩，对它所做的工作是发动机损失的直接来源。目前，燃气轮机使用大约30%的压缩空气来冷却发动机的高温阶段。蒸腾冷却是目前技术水平上的一个潜在改进。它包括让冷却剂通过类似多孔材料的细通道。流经叶片的冷却剂和从叶片表面流出的液体都起到冷却和保护叶片免受热气体影响的作用。蒸腾冷却需要新的制造技术和对冷却剂流动以及与发动机主要气体路径的相互作用的更深入的了解。蒸腾冷却将使涡轮机的入口温度比目前可能的温度提高200摄氏度，比功率提高10%。可以进一步减少发动机的冷却剂用量，显著提高效率。蒸腾冷却对高超声速飞行器，如重返高层大气的太空飞行器也很感兴趣。多孔陶瓷可用于此目的。虽然该项目仅限于燃气轮机的金属部件，但实验和数值方法以及冷却剂的几何形状可能是可转移的。项目目的将开发仪器和方法来测量冷却剂通过多孔材料的渗透，有或没有交叉流动。这将首先从平板开始，并最终扩展到叶片样品。将建立数值模型并根据实验数据进行验证。根据叶片的运行要求和对冷却剂流动的不断发展的理解，将提出新的冷却剂通道几何形状。伯明翰高温研究中心的尼克·格林教授将提供制造方面的专业知识。利用传统的加工技术，他将为早期研究提供平板。提出了一种新的叶片样品铸造工艺。全新的领域需要全新的冷却剂几何形状来实现蒸腾冷却的定义。在这种几何学中有发明和新奇的空间。原型叶片将采用全新的制造技术，这将允许新的形状，并具有文献中未处理的限制和问题。新的仪器和技术可以用来测量建筑物的积液，使用最先进的光敏涂料，热丝探头等。研究主题本项目与EPSRC能源主题下的能源效率子主题保持一致。该项目由EPSRC资助。

The specific power of gas turbine engines is fundamentally limited by the turbine combustion temperature. Progressively more elaborate methods have been employed to elevate this above the melting point of the metals employed in the engines. Coolant is taken from the compressor stages and used to reduce the temperature of the hot metal parts downstream of the combustion to an acceptable temperature.The coolant requires compressing and the work done on it represents a direct source of loss of the engine. Currently gas turbines use about 30% of the air compressed to cool the hot stages of the engine.Transpiration cooling is a potential improvement on the current state of the art. It involves passing coolant through fine passages that may resemble a porous material. The coolant flowing through the blade and the resulting effusion from its surface both serve to cool and protect the blade from the hot gasses.Transpiration cooling requires new manufacturing technologies and deeper understanding of the coolant flow and the interaction with the main gas path of the engine. Transpiration cooling would enable a raising of the turbine entry temperature of 200C above what is currently possible increasing the specific power by up to 10%.The coolant used in the engine could be reduced further increasing the efficiency significantly.Transpiration cooling is also of interest to hypersonic vehicles such a space vehicles re-entering the upper atmosphere. Porous ceramics may be employed for this purpose. Although this project is confined to metal parts for gas turbines, experimental and numerical methods and coolant geometry may be transferrable.Aims of the ProjectInstrumentation and methods will be developed to measure the effusion of coolant through porous materials with and without cross flow. This will initially start with flat plates and will eventually be extended to blade samples.Numerical models will be built and validated against experimental data. Based on the operational requirements of the blade and the developing understanding of the coolant flow new geometries of coolant channels will be proposed. Prof Nick Green at the High Temperature Research Centre in Birmingham will provide manufacturing expertise. Using traditional machining techniques he will supply flat plates for early study. A novel casting technique is proposed to make blade samples.Areas of NoveltyEntirely novel coolant geometry is required to achieve the definition of transpiration cooling. There is scope for invention and novelty in this geometry.The prototype blades will use totally novel manufacturing techniques which will permit new shapes and have constraints and issues not dealt with in the literature.Novel instrumentation and techniques may be employed to measure the effusion building on the state of the art use of photosensitive paint, hot wire probes etc.Research ThemeThis project is aligned with the EPSRC sub-theme of energy efficiency under the main theme of energy. This project is funded by the EPSRC.