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

为了减少航空业的排放，我们必须提高航空发动机的效率，以实现可持续燃料。这些发动机的关键部件是高压涡轮（HPT），它从热燃烧室出口气体中提取能量。出口气体的温度比HPT金属的熔点高几百度，并在继续上升，以提高发动机的效率。叶片的温度是通过注入冷空气来控制的，通过它和它的表面来保护它免受热气体的影响，但是冷却流的使用降低了效率。因此，我们必须在降低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的需求，从而减少表面积，但这会给每个剩余的叶片带来更多的空气动力负荷或升力。然而，这种高升力叶片的空气动力性能较差。特别是，叶片的吸力面（SS）和压力面（PS）之间的压力差越大，往往会导致更多的泄漏流通过动叶顶与静机匣之间的间隙。这种过叶尖泄漏（OTL）流降低了涡轮的功输出和气动效率。该项目旨在通过以下方式实现高升力叶片的使用：(1)降低较高的OTL流量以保持气动效率；(2)开发高效的冷却策略以减少冷却流量需求。为了减轻OTL流动，将研究高升力剖面的部分护罩或小翼和空腔。由于之前很少有关于高扬程OTL流动的研究，因此该项目将采用多学科的方法，结合分析、数值和实验方法来评估气动和热性能。设计空间将通过分析模型和更复杂的计算流体动力学（CFD）模拟来探索新的尖端设计和冷却配置。有前途的设计将被推广到跨音速线性叶栅实验装置上，该实验装置采用气动探头测量流场，红外热像仪提取传热系数，压敏涂料与外来气体喷射来确定冷却膜的有效性。成功实现这些高升力设计，每年将减少约350万吨二氧化碳排放，从而减少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.