The development of a distributed electric propulsion (DEP) noise model
C.N.M. Bononi Bello (TU Delft - Aerospace Engineering)
M. Snellen – Mentor (TU Delft - Aerospace Engineering)
F. Yin – Graduation committee member (TU Delft - Aerospace Engineering)
E.J.J. Smeur – Graduation committee member (TU Delft - Aerospace Engineering)
S. Heblij – Mentor (Royal Netherlands Aerospace Centre)
W de Haan – Mentor (Royal Netherlands Aerospace Centre)
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Abstract
With the ever-increasing demand of air travel from before the pandemic expected to return, the world’s concern of environment-related issues linked to aviation has also increased. With these issues becoming progressively important, it is not surprising that the propeller, with generally a superior efficiency over the jet engine, has regained the interest of the aviation sector. Among the various concepts being explored, one particular propeller configuration stood out as promising: the distributed electric propulsion (DEP) configuration. While DEP configurations have the potential to revolutionise aircraft designs and their performance, there are still several technological and operational challenges that must be addressed before these configurations start roaming the skies. One of the research areas that still needs to be explored, for example, is the noise pollution caused by a DEP aircraft, and consequently the impact it has on society. For that reason, the development of a noise prediction model of a DEP aircraft is introduced in this paper. Acoustic results are presented for Maeve-01, a DEP concept aircraft designed by Dutch startup Maeve Aerospace 1. The DEP model solely focuses on tonal propeller noise generated by steady blade loading and propeller rotation; i.e., broadband sources and unsteady loading noise are disregarded in this study. The tonal noise signatures of an isolated propeller are computed with a model that uses the Helicoidal Surface Theory to predict the source noise. Subsequently, the individual source noises are superimposed at observers in the far field by applying digital processing steps to incorporate spherical spreading, the Doppler effect, atmospheric absorption and phase lags to include the interference effects between propellers. The DEP model is verified both using a more computational intensive model (developed by NLR) for the isolated propeller signatures, and by predicting the directivity patterns of two monopole sources along the axis over the wing span to model the source field of two interfering propellers. For the validation of the DEP model, real-life flyover experiments have been performed with a small drone with four propellers, combined with a comparison with literature data.