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

Abstract

Expensive flyover 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 noise source-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 in the 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 introduced and applied to the numerical data to allow for a meaningful comparison of the results to microphone data recorded during flyover experiments. In particular, great care is taken to quantify the numerical dissipation of the simulation inside the nacelle and to enable a suitable correction of the 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 order to pinpoint the most significant sources and effects.

Aeroacoustics research in Europe: The CEAS-ASC report on 2018 highlights

“…Special care was taken to validate the accuracy of the interfaces between the tools. To ensure that the entire computational chain delivers plausible results, the results were compared to another simulation [73] using an established technique for the case of an isolated engine and a good agreement was found. To prove the new methods capability of predicting the tonal fan noise of an installed engine, the technique was applied to a V2527 engine mounted underneath the fully equipped wing of an A320 aircraft in approach conditions (shown in Fig 32).…”