The Challenge of Tonal Fan Noise Prediction for an Aircraft Engine in Flight

摘要

Expensive fly-over tests are needed to verify that noise certification standards are fulfilled. Currently, no numerical alternative exists to perform a holistic "virtual fly-over" test. As a step towards enabling such evaluations in the future, the authors focus on an isolated noisesource – the tonal rotor-stator-interaction (RSI) of the fan stage. A high-fidelity simulation relying on a state-of-the-art yet computationally efficient method is performed for a V2527 aircraft engine in approach conditions. The computational domain includes the noise generation inthe fan stage, its propagation in the engine inlet and bypass duct, as well as its radiation into the far field. Installation effects due to bifurcations and struts in the duct, ESS (engine section stator), liners, and inflow distortions are not considered. Post-processing methods are introducedand applied to the numerical data to allow for a meaningful comparison of the results to microphone data recorded during fly-over experiments. In particular, great care is taken to quantify the numerical dissipation of the simulation inside the nacelle and to enable a suitable correction ofthe numerical data. The numerical simulation cannot fully reproduce the experimental data indicating that its level of complexity is not yet sufficient. As there is no obvious cause for the mismatch, it would be necessary to incrementally increase the complexity of the simulation in orderto pinpoint the most significant sources and effects.