Acoustic Characterization of Forward- and Backward-Skewed Axial Fans Under Increased Inflow Turbulence

Zenger, Florian; Herold, Gert; Becker, Stefan

doi:10.2514/1.j055383

Cited by 32 publications

(12 citation statements)

References 30 publications

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“…The aerodynamic properties for the disturbed inflow conditions have already been described in the literature [3,28,29] on the basis of laser Doppler anemometry measurements. For the present study, the flowfield was reinvestigated using 3-D CTA from Dantec Dynamics.…”

Section: Inflow Conditionsmentioning

confidence: 99%

“…The noise generation due to the interaction of the leading edge of an airfoil or blade with an incoming turbulence can also be a dominant noise source for fans [3,[27][28][29]: for example, when they are placed downstream of a heat exchanger (see, for example, Ref. [30]).…”

Section: Introductionmentioning

confidence: 99%

“…The underlying noise generation mechanisms can differ from those observed at isolated airfoils because the prevalent velocity components are much different due to the rotation. In addition, the turbulence in such rotating systems will most likely not be ideally homogeneous and isotropic as in a wind-tunnel study on isolated airfoils [3,28,29]. This makes a transfer of noise reduction techniques from a single, steady airfoil to a rotating fan challenging [31,32].…”

Section: Introductionmentioning

confidence: 99%

“…However, leading-edge treatment approaches to reduce turbulence interaction noise also exist for axial fans, including leading-edge serrations [31][32][33][34][35][36] and porous materials [37][38][39]. In addition, modifications of the shape of the blades in the form of sweeping or skewing are known as effective means for noise reduction [3,[40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

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Permeable Leading Edges for Airfoil and Fan Noise Reduction in Disturbed Inflow

Ocker

Geyer

Czwielong³

et al. 2021

AIAA Journal

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A detailed experimental study on the aerodynamic performance and noise emission of airfoils and fan blades with permeable leading edges under disturbed inflow conditions was performed. The airfoils and fan blades with permeable leading edges were made of an aluminum alloy using a powder bed fusion-based additive manufacturing process. In a first step, a wind-tunnel study was carried out. This consisted of detailed aerodynamic and aeroacoustic measurements on 16 airfoils with different permeable leading-edge designs that were performed for various flow speeds and geometric angles of attack. Based on the results from that study, unskewed fan blades with four different permeable leading-edge designs were manufactured in a second step. With the aim of reducing turbulence interaction noise of axial fans, the fans were examined with regard to their aerodynamic and acoustic properties under grid-generated turbulent inflow conditions. In a third step, a possible transfer of the observed noise emission from airfoils with permeable leading edge to that of fan blades was investigated. It was found that a notable broadband noise reduction can be transferred from airfoil applications to the sound spectra of axial fans. At the same time, the porous modifications can reduce the aerodynamic performance, and hence the fan efficiency.

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Section: Inflow Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Permeable Leading Edges for Airfoil and Fan Noise Reduction in Disturbed Inflow

Ocker

Geyer

Czwielong³

et al. 2021

AIAA Journal

Self Cite

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“…Zhou et al [13] utilised the Bezier curve to determine the parameters of the blade meridian of an air-conditioning axial fan and indicated that the flow field is improved and the noise is reduced by 1.1 dB after blade skewing. Zenger et al [14] experimentally examined the influence of increased inflow turbulence on the sound generation in forward-and backward-skewed low-pressure axial fans. They found that distorted inflow conditions have a significant impact on the sound emission and the extent of this is strongly related to blade design.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Performance of a Variable-Pitch Axial Fan with Forward-Skewed Blades

Ye¹,

Fan²,

Zhang³

et al. 2019

Energies

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For a single-stage variable-pitch axial fan, the aerodynamic performance and through flow with and without blade skewing are examined numerically. Simulated results show that the total pressure rise and efficiency increase by 2.99% and 0.16%, respectively, with the best forward-skewed angle of θ = 3° at the design conditions. At the blade pitch angles of β = 29° and 35°, the total pressure rises and efficiency of the fan with θ = 3.0° under the highest efficiency point change by −0.55%, −0.53% and 1.39%, 2.11%, respectively. At design and off-design conditions, the forward-skewed blades mitigate tip leakage and delay the emergence of separation flow at the blade root, these benefits are higher at the higher blade pitch angle. The θ = 3.0° forward skew effectively raises the stage performance of the impeller and guide vanes.

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