Reduction of shrouded propeller noise with Over-Tip-Rotor liners

Palleja-Cabre, Sergi, Macey, Ella, Chaitanya, Paruchuri and Joseph, Phillip (2024) Reduction of shrouded propeller noise with Over-Tip-Rotor liners. In 30th AIAA/CEAS Aeroacoustics Conference, 2024. American Institute of Aeronautics and Astronautics.. (doi:10.2514/6.2024-3407).

Abstract

This paper presents a predominately experimental investigation of the reduction of noise from shrouded propellers by using Over-Tip-Rotor (OTR) liners. Experimental far-field noise data has been obtained for SDOF and grooved metal foam liners installed upstream of the propeller, in an OTR position, and downstream of the propeller. A bellmouth intake and a lip or unflanged intake have been considered. The shroud intake geometry strongly modifies the inflow characteristics onto the propeller and significantly affects the sources of propeller noise. The liners are found to provide up to 5 dB of reduction in overall sound pressure level at observer locations close to the propeller axis and peak PWL noise reductions of up to 6 dB in both tonal and broadband noise. It is found that installing the liners over the propeller tip does not provide the maximum noise reduction in the forward arc for all configurations but that it depends both on the type of OTR liner and the intake geometry. An existing point source analytical model has been shown to capture the main features of the measured noise reduction spectra but overpredicts the levels of noise reduction.

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Contributors

Author: Sergi Palleja-Cabre

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