Aerostructural investigation of shape adaptive rotor blading for the reduction of BLI induced losses in the distorted flow regimes of a transonic fan rotor

Abstract

Within the Cluster of Excellence for Sustainable and Energy-Efficient Aviation SE2A, a blended wing body aircraft is investigated to improve efficiency and carbon emissions of future air transport. By embedding the aircraft engines on the top rear fuselage, parts of the aircraft’s wing boundary layer are ingested, which has the potential to further improve the engine’s propulsion efficiency. Through the ingestion of low momentum fluid however, inflow distortion is induced and the fan rotor operates under increased flow incidence in the distorted flow regimes. To reduce the thereby arising efficiency and pressure ratio penalties in the aircraft engine, alternative design strategies for the fan stage are required. Within this investigation, an active shape morphing mechanism is introduced, which allows to temporarily adjust the fan blading when the fan rotor is exposed to distorted inflow conditions. By integrating piezoceramic actuators into the rotor blading, the blade staggering and turning can be adjusted with the goal to reduce flow incidence and deviation in the distorted flow regimes. For this investigation the NASA rotor 67 is chosen as a reference test case and its performance under boundary layer ingestion (BLI) conditions is evaluated. For the shape morphing assessment, FEA morphing simulations are tightly coupled with a geometry re-engineering methodology and stationary CFD simulations of the actuated fan rotor geometries under distorted inflow. For the chosen test case, the achievable deformations are however too small to compensate for the strong distortion effects of a blended wing body’s boundary layer. Therefore, the blade reference design needs to be adapted in order to increase the achievable deformations. This includes the investigation of typical compressor design parameter variations, such as blade hub-to-tip ratio, chord length as well as lean and sweep and their impact on the deformability of a shape-adaptive fan stage.