Performance and Stability Analysis of a Highly-Loaded Low-Pressure Compressor Under Distorted Inflow Conditions

Advanced aircraft technologies are currently in the focus of research to address the environmental goal of reducing aircraft emissions within the next decade and beyond. Short-Nacelle High-Bypass (SNHB) turbofans and Boundary Layer Ingestion (BLI) engines are among the most promising technologies to improve fuel and propulsive efficiency in the short and long term respectively, forcing nevertheless the engine to operate with a highly distorted inlet flow.

Although operability and performance deterioration of fans under distorted conditions has been the primary focus of research in last decades, almost no information is currently available on the low-pressure compressor (booster), despite its crucial role in the forthcoming generation of engines. The complex flow distortion pattern observed behind the fan may indeed influence the underlying physical mechanisms taking place within the compressor stage, possibly jeopardizing performance and stability of the whole engine. This research activity therefore aims at providing a complete characterization of the physical phenomena driving loss generation and stability deterioration in modern low-pressure compressors when distorted flow conditions set up.

An axial compressor representative of the first stage of a modern geared turbofan booster was tested in the VKI-R4 facility with an inlet total pressure distortion, while unsteady simulations were used to support the results of the experiments. The assessment of global performance, along with detailed flow surveys to ensure a thorough understanding of the involved physical phenomena in the clean and distorted machine were performed. Such extensive set of data is believed to support the development and design of boosters for the forthcoming generation of aircraft engines.