Non-Intrusive Flow distortion measurements within a Turbofan Intake (NIFTI)- De-risking the test campaigns with CFD analysis

Abstract

Short and slim aero-engine intake designs for very high bypass ratio configurations cause notable levels of steady and unsteady distortions at the fan face, especially under crosswind or AOA operation during aircraft take-off. Such distortions can adversely affect the engine’s performance, operability, structural integrity and safety margin with potentially catastrophic consequences for the entire propulsion system. There is a significant lack of open published measured data for fans and compressors operating under inlet distortions, which is mainly due to the difficulties and cost involved in setting up such experimental campaigns. The Non-Intrusive Flow distortion measurements within a Turbofan Intake (NIFTI) project aims to address this gap by demonstrating a non-intrusive technique for measuring velocity fields across a plane located upstream of a large diameter fan of a high bypass ratio aero-engine which has never been achieved. This method will provide synchronous datasets across the measurement plane with at least one order of magnitude higher spatial resolution than current methods. The experimental activities will be supported by numerical campaigns and advanced data processing of measured data, which will be used to analyse the highly unsteady nature of the flow distortions. The outcome of this project will ultimately unlock the complex aerodynamics of closely coupled fan-intake systems and aid the validation of CFD codes, as well as establish novel design guidelines for future, stall-tolerant aero-engines. This paper reports on the initial finding from CFD analysis of NIFTI project, focusing on the investigation of the interaction between the distortion caused by the AOA (upstream) and pylon (downstream) on a low-speed fan blade operation and addressing the possible aerodynamic instabilities which can arise for such a system. The aim is to use CFD to predict aerodynamic and in-future aeroelastic stability of the coupled fan-intake configuration prior to the test campaigns in order to computationally determine the operating envelope of the rotating fan experimental facility.