Construction and Assessment of an Inflow-Control-Device for a Low-Speed Aeroacoustic Fan Rig

Caldas, Luciano; Kruck, Sebastian; Klähn, Lukas; Rudolphi, Angelo; Meyer, Robert K.; Enghardt, Lars; Tapken, Ulf

doi:10.2514/1.j061729

Cited by 5 publications

References 11 publications

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New method to separate turbulence statistics of fan rotor wakes from background flow

Caldas

Meyer

2023

Exp Fluids

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The separation of turbulence parameters such as turbulence intensity and integral length scale of fan rotor wakes from background flow from unsteady velocity data is a challenge. The two processes are overlapped, and typically, very few samples of the data are taken inside the rotor wakes, making it hard to perform any spectral analysis. This work proposes a new time domain approach to separate the two processes by using two suitable data tapers. The unsteady velocity cyclic variance distribution is used as reference to establish the border between the blade wakes and the background flow. Results indicate an increase in wake turbulence levels and a slight increase in background turbulence levels with the increase in fan blade loading. The integral length scale of the rotor wakes did not change considerably among the different fan loading analyzed. This contrasts with the values observed for the background flow, which decreased with increasing of fan loading. The rotor wakes seem to be anisotropic, regardless of the fan operating point. Graphical abstract

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New method to separate turbulence statistics of fan rotor wakes from background flow

Caldas

Meyer

2023

Exp Fluids

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Experimental Investigation of Mode-Frequency Scattering at Fan Stages

Behn,

Tapken

2024

Journal of Turbomachinery

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For the development of low-noise fan designs the sound generation must be reduced at the source, but also sound transmission effects through the rotor can be exploited to reduce the noise emitted to the far-field. Rotor shielding has been identified as a means of noise abatement, where rotor counter-rotating modes are blocked by the rotor and transmit poorly to the inlet. An effect that is rarely considered in this context is mode-frequency scattering at the rotor, which can circumvent the blockage effect by shifting the sound energy in frequency and mode order, typically to a rotor co-rotating mode order that transmits efficiently to the inlet. An experimental investigation is presented, where the transmission, reflection and scattering of individually generated modes through a fan stage is measured by means of a loudspeaker array and microphone arrays, upstream and downstream. The highly resolved measured data comprise the variation of mode order, frequency, rotor speed and aerodynamic operating conditions. In this study the focus is on mode-frequency scattering, for which results are presented for high and low rotor speed.

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Measurements of fan inflow distortion noise generation in a low speed fan - part I: aerodynamic analyses

Caldas

Klähn

Meyer

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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Construction and Assessment of an Inflow-Control-Device for a Low-Speed Aeroacoustic Fan Rig

Cited by 5 publications

References 11 publications

New method to separate turbulence statistics of fan rotor wakes from background flow

New method to separate turbulence statistics of fan rotor wakes from background flow

Experimental Investigation of Mode-Frequency Scattering at Fan Stages

Measurements of fan inflow distortion noise generation in a low speed fan - part I: aerodynamic analyses

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