High-Lift High-Pressure Turbine Blade Tips for Future Aircraft Engines

为了减少航空部门的排放，我们必须提高航空发动机的效率，以实现可持续燃料。这些发动机中的一个关键部件是高压涡轮(HPT)，它从燃烧室出口的高温气体中提取能量。排出气体的温度比HPT金属的熔点高出几百度，并且还在继续上升，以提高发动机的效率。叶片的温度是通过向叶片表面注入较冷的空气来控制的，以保护叶片不受高温气体的影响，但使用冷却流会降低效率。因此，我们必须在减少冷却流量要求的同时实现有效的冷却。我们可以通过减少叶片的数量来减少冷却流量需求，从而减少表面积，但这会对每个剩余的叶片施加更多的气动载荷或升力。然而，这种高升程叶片的气动性能可能会较差。特别是，叶片吸力面(SS)和压力面(PS)之间的较高压力差往往会通过转子叶片尖端和静止机壳之间的间隙驱动更大数量的泄漏流动。这种超尖端泄漏(OTL)流降低了涡轮的输出功和气动效率。该项目旨在通过(1)缓解较高的OTL流动以保持空气动力效率，以及(2)开发高效的冷却策略来降低冷却流量要求，从而实现高升程叶片的使用。为了缓解OTL流动，将用高扬程剖面研究部分护罩或小翼和空腔。由于以前很少有关于高升程OTL流动的工作，本项目将采用多学科方法结合分析、数值和实验方法来评估气动和热性能。将使用分析模型和更复杂的计算流体动力学(CFD)模拟来探索设计空间，以研究新颖的尖端设计和冷却配置。有希望的设计将被推广到跨音速线性叶栅实验台上，该实验台使用空气动力学探头测量流场，红外热像仪提取换热系数，压敏涂料使用外来气体喷射来确定冷却膜的有效性。成功启用这些高扬程设计将每年减少约350万吨二氧化碳的排放，目标是减少0.3%的燃料消耗。

In order to reduce the emissions from the aviation sector, we must improve the efficiency of aero engines to enable sustainable fuels. A key component in these engines is the High-Pressure Turbine (HPT), which extracts energy from the hot combustor exit gasses. The temperature of the exit gas is several hundred degrees above the melting point of the HPT metal and is continuing to rise to improve engine efficiency. The blade temperature is controlled by injecting cooler air through it and over its surface to shield it from the hot gas, but the use of cooling flows reduce efficiency. We must therefore achieve effective cooling while reducing cooling flow requirements. We can reduce cooling flow requirements by decreasing the number of blades, and thus surface area, but this puts more aerodynamic load, or lift, on each remaining blade. However, such high-lift blades can suffer poorer aerodynamic performance. In particular, the higher pressure difference between the blade's Suction Surface (SS) and Pressure Surface (PS) tends to drive greater amounts of leakage flow through the clearance gap between the rotor blade tip and the stationary casing. This Over-Tip Leakage (OTL) flow reduces the turbine work output and aerodynamic efficiency. This project aims to enable the use of high-lift blades by (1) mitigating the higher OTL flow to maintain aerodynamic efficiency, and (2) developing highly effective cooling strategies that reduce the cooling flow requirement. In order to mitigate OTL flows, partial shrouds, or winglets, and cavities will be studied with high-lift profiles. Since there is little previous work on high-lift OTL flows, this project will take a multi-disciplinary approach to assess aerodynamic and thermal performance, combining analytical, numerical, and experimental methods. The design space will be explored with the use of analytical models, and more complex Computational Fluid Dynamics (CFD) simulations to investigate novel tip designs and cooling configurations. Promising designs will be carried forward to a transonic linear cascade experimental rig which employs aerodynamic probes to measure the flow field, infrared thermography to extract heat transfer coefficients, and pressure sensitive paint with foreign gas injection to determine cooling film effectiveness. Successfully enabling these high-lift designs would reduce emissions by around 3.5 million tonnes of CO2 per year as a result of a targeted 0.3% reduction in fuel consumption.