Measurements of fan inflow distortion noise generation in a low speed fan - part II: acoustic analyses

Klähn, Lukas; Caldas, Luciano; Tapken, Ulf

doi:10.2514/6.2022-2945

Cited by 2 publications

(1 citation statement)

References 17 publications

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“…The comparison is performed at the three operating points DP, PR max and ṁmax (see Table 1). A detailed description of the pure experimental data can additionally be found in [33].…”

Section: Acoustic Validation Using the Baseline Fanmentioning

confidence: 99%

Smart Blade Count Selection to Align Modal Propagation Angle with Stator Stagger Angle for Low-Noise Ducted Fan Designs

Schade,

Jaron,

Klähn

et al. 2024

Aerospace

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The rotor–stator interaction noise is a major source of fan noise. Especially for low-speed fan stages, the tonal component is typically a dominant noise source. A challenge is to reduce this tonal noise, as it is typically perceived as unpleasant. Therefore, in this paper, we analytically, numerically and experimentally investigate an acoustic effect to lower the tonal noise excitation. Our study on an existing low-speed fan indicates a reduction in tonal interaction noise of more than 9 dB at the source if the excited acoustic modes propagate parallel to the stator leading edge angle. Moreover, a design-to-low-noise approach is demonstrated in order to apply this effect to two new fan stages with fewer stator than rotor blades. The acoustic design of both fans is determined by an appropriate choice of the rotor and stator blade numbers in order to align the modal propagation angle with the stator stagger angle. The blade geometries are obtained from aerodynamic optimization. Both fans provide similar aerodynamic but opposing acoustic radiation characteristics compared to the baseline fan and a significant tonal noise reduction resulting from the impact of the modal propagation angle on noise excitation. To ensure that this effect can also be applied to other low-speed fans, a design rule is derived and validated.

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“…The comparison is performed at the three operating points DP, PR max and ṁmax (see Table 1). A detailed description of the pure experimental data can additionally be found in [33].…”

Section: Acoustic Validation Using the Baseline Fanmentioning

confidence: 99%