@article{BiedermannHintzenKameier2022, author = {Biedermann, Till M. and Hintzen, Nils and Kameier, Frank}, title = {Aeroacoustic Interactions of Blade Skew and Leading Edge Serrations Applied to Low-Pressure Axial Fans}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {144}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {12}, publisher = {ASME International}, issn = {0742-4795}, doi = {10.1115/1.4055637}, pages = {12}, year = {2022}, abstract = {Leading edge serrations are well known for their ability to reduce turbulence-induced noise of single aerofoils while also providing aerodynamic advantages under certain operating conditions. Continuatively, applying leading edge serrations to rotating machinery such as axial fans proved the validity to generally transfer the obtained aeroacoustic benefits of single aerofoils. However, for the rotating applications the noise reduction potential highly depends on the point of operation. The current work aims at assessing the aeroacoustic effects of serrated leading edges under the increased geometrical complexity of the fan blades through blade skew. Therefore, the question is whether combining two potentially effective noise-reducing treatments through blade skew and leading edge serrations results in leveraging or obstructing effects. By varying the skew angle from 0 deg to 38 deg, four different prototypes of the fan impeller are tested experimentally in a test rig according to ISO 5136 and ISO 5801. All configurations are tested with original blades of straight leading edges plus five sets of serrations each, parameterised by the serration amplitude and the serrations wavelength. The intensity of the incoming turbulence ranges from 2.6\% to 12.1\%. The results obtained show the skewed blades to improve both the aerodynamic performance and the noise radiation after exceeding an initial skew angle, complemented by a significant onset of stall. Moreover, no contraindication between blade skew and serrated leading edges is encountered, showing the potential to further extend the noise reduction capabilities by combining effects of blade skew and leading edge treatment.}, language = {en} } @inproceedings{FelkerBiedermannKameier2023, author = {Felker, Alexander and Biedermann, Till M. and Kameier, Frank}, title = {Low-Noise Design of Axial Fans Through Optimized Spanwise Application of Leading Edge Serrations}, series = {ASME Turbo Expo 2023, Vol. 6: Education; Electric Power; Energy Storage; Fans and Blowers}, booktitle = {ASME Turbo Expo 2023, Vol. 6: Education; Electric Power; Energy Storage; Fans and Blowers}, publisher = {American Society of Mechanical Engineers}, isbn = {978-0-7918-8699-1}, doi = {10.1115/GT2023-102629}, pages = {13}, year = {2023}, abstract = {Recent studies have shown that leading edge serrations can effectively reduce broadband noise in axial fans and expand their operational range. However, additional aerodynamic losses have to be considered alongside the benefits of improved acoustic performance. The majority of studies focused on applying leading edge serrations along the entire span of the rotor blades regardless of local differences in radial inflow angles, deflection effects, and blade loading. In this regard, local and spanwise varying applications of leading edge serrations are considered crucial to reconciling maximum aeroacoustic and aerodynamic performance. In making these applications, a fan blade span is divided into five sub-segments. Each segment can then be equipped with either an acoustic or aerodynamic optimum as well as a baseline straight leading edge. Through testing at three different inflow turbulence levels along the full characteristic curve, an extensive statistical experimental design is executed. Ultimately, a simplified statistical model is derived. The model provides information on the optimum spanwise shape of a serration design. The results indicate significant effects of the local spanwise selection of varying serration designs. Discrepancies between aerodynamic and aeroacoustic optimum solutions can be satisfactorily resolved where, primarily, a significant extension of the working area is observed. Moreover, an extended potential in the delay of stall entry and the associated improvement of total pressure as well as a significant reduction of aeroacoustic signature is found. The underlying mechanisms are attributed to the compartmentalization effects of the serrations which restrict separation phenomena to local cells of finite spanwise extension. Furthermore, the spanwise geometrical parametrization of the serration segments correlates well with radial blade loading as well as respective flow conditions. By taking the radial distribution of aerodynamic quantities into account, an individual design of locally applied leading edge serrations can be integrated into the fan design process, enabling improved balancing between aeroacoustic benefits while maximizing aerodynamic performance.}, language = {en} } @article{BiedermannCzeckayGeyeretal.2019, author = {Biedermann, Till M. and Czeckay, Pasquale and Geyer, Thomas F. and Kameier, Frank and Paschereit, Christian O.}, title = {Effect of Inflow Conditions on the Noise Reduction Through Leading Edge Serrations}, series = {AIAA Journal}, volume = {57}, journal = {AIAA Journal}, number = {9}, publisher = {American Institute of Aeronautics and Astronautics (AIAA)}, issn = {0001-1452}, doi = {10.2514/1.J057831}, pages = {4104 -- 4109}, year = {2019}, language = {en} } @inproceedings{BiedermannCzeckayGeyeretal.2018, author = {Biedermann, Till M. and Czeckay, Pasquale and Geyer, Thomas F. and Kameier, Frank and Paschereit, Christian O.}, title = {Noise Source Identification of Aerofoils Subjected to Leading Edge Serrations using Phased Array Beamforming}, series = {2018 AIAA/CEAS Aeroacoustics Conference}, booktitle = {2018 AIAA/CEAS Aeroacoustics Conference}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Virginia}, doi = {10.2514/6.2018-3794}, year = {2018}, language = {en} } @inproceedings{BiedermannHintzenKameieretal.2018, author = {Biedermann, Till M. and Hintzen, Nils and Kameier, Frank and Chong, Tze Pei and Paschereit, Christian O.}, title = {On the Transfer of Leading Edge Serrations from Isolated Aerofoil to Ducted Low-Pressure Fan Application}, series = {2018 AIAA/CEAS Aeroacoustics Conference}, booktitle = {2018 AIAA/CEAS Aeroacoustics Conference}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Virginia}, doi = {10.2514/6.2018-2956}, year = {2018}, language = {en} } @article{BiedermannChongKameieretal.2017, author = {Biedermann, Till M. and Chong, Tze Pei and Kameier, Frank and Paschereit, Christian O.}, title = {Statistical-Empirical Modeling of Airfoil Noise Subjected to Leading-Edge Serrations}, series = {AIAA Journal}, volume = {55}, journal = {AIAA Journal}, number = {9}, publisher = {American Institute of Aeronautics and Astronautics (AIAA)}, issn = {0001-1452}, doi = {10.2514/1.J055633}, pages = {3128 -- 3142}, year = {2017}, language = {en} } @article{BiedermannCzeckayHintzenetal.2020, author = {Biedermann, Till M. and Czeckay, Pasquale and Hintzen, Nils and Kameier, Frank and Paschereit, C. O.}, title = {Applicability of Aeroacoustic Scaling Laws of Leading Edge Serrations for Rotating Applications}, series = {Acoustics}, volume = {2}, journal = {Acoustics}, number = {3}, publisher = {MDPI AG}, issn = {2624-599X}, doi = {10.3390/acoustics2030030}, pages = {579 -- 594}, year = {2020}, abstract = {The dominant aeroacoustic mechanisms of serrated leading edges, subjected to highly turbulent inflow conditions, can be compressed to spanwise decorrelation effects as well as effects of destructive interference. For single aerofoils, the resulting broadband noise reduction is known to follow spectral scaling laws. However, transferring serrated leading edges to rotating machinery, results in noise radiation patterns of significantly increased complexity, impeding to allocate the observed noise reduction to the underlying physical mechanisms. The current study aims at concatenating the scaling laws for stationary aerofoil and rotating-blade application and thus at providing valuable information on the aeroacoustic transferability of leading edge serrations. For the pursued approach, low-pressure axial fans are designed, obtaining identical serrated fan blade geometries than previously analyzed single aerofoils, hence allowing for direct comparison. Highly similar spectral noise reduction patterns are obtained for the broadband noise reduction of the serrated rotors, generally confirming the transferability and showing a scaling with the geometrical parameters of the serrations as well as the inflow conditions. Continuative analysis of the total noise reduction, however, constrains the applicability of the scaling laws to a specific operating range of the rotors and motivates for a devaluation of the scaling coefficients regarding additional rotor-specific effects.}, language = {en} } @inproceedings{BiedermannMoutamassikKameier2021, author = {Biedermann, Till M. and Moutamassik, Youssef and Kameier, Frank}, title = {Feasibility Study on the Effect of Blade Inclination for Heavy Duty Centrifugal Fans - Aerodynamic Aspects}, series = {Volume 1: Aircraft Engine; Fans and Blowers; Marine; Wind Energy; Scholar Lecture}, booktitle = {Volume 1: Aircraft Engine; Fans and Blowers; Marine; Wind Energy; Scholar Lecture}, publisher = {American Society of Mechanical Engineers}, doi = {10.1115/GT2021-58505}, pages = {11}, year = {2021}, abstract = {With a special focus on the industrial feasibility and the manufacturability, a recently proposed novel approach to centrifugal impeller blade inclination is adopted and investigated through extensive CFD analysis. The fan blades, originally aligned perpendicular to the impeller backplate, are inclined in either forward or backward direction. For the presented study, an industrially proven fan design is chosen for testing. Compared to the original design, the inclined fan blades possess an increased total blade area and at the same time providing variable inflow angles at the leading edges of the blades. These two factors are expected to alter the fan characteristic curves in providing an increased range of optimum performance while maintaining high aerodynamic efficiency. The results obtained show a clear trend in aerodynamic performance with the degree of inclination, where the characteristic curves rotate at about the design point, allowing local improvements either at overload conditions or part-load conditions of the fan. Moreover, the trends obtained show the tendency to agree well with the rudimentary models published in previous studies, even though it appears to be affected by the fan volute and the point of operation as well.}, language = {en} } @inproceedings{BaldeBiedermannKameieretal.2023, author = {Balde, Nina Maimuna and Biedermann, Till M. and Kameier, Frank and Pohlmann, Tobias}, title = {Aeroacoustic Scaling of Axial Low-Pressure Fans With Leading Edge Serrations}, series = {Volume 6: Education; Electric Power; Energy Storage; Fans and Blowers}, booktitle = {Volume 6: Education; Electric Power; Energy Storage; Fans and Blowers}, publisher = {American Society of Mechanical Engineers}, doi = {10.1115/GT2023-103181}, year = {2023}, abstract = {Previous as well as ongoing studies have shown that bioinspired modifications of the leading edge of axial fans, so-called leading edge serrations, have beneficial effects on sound radiation in rotating systems such as a broadband noise reduction. The objective of this study is to elaborate on the comparability of two geometrically similar low-pressure axial fans that differ in fan diameters. For this purpose, a fan design based on the geometric characteristics of an existing fan, which had been tested in previous studies, was developed with and without leading edge serrations at a scale of 1:3. Extensive experiments were carried out to gather detailed data on the aerodynamic and aeroacoustic performance of the specimen. Similarity laws and non-dimensional parameters are used to investigate whether a transferability comparison of the aerodynamic and aeroacoustic experimental results of these geometrically similar axial fans is possible. The latter also includes an analysis of the spectral range. The results prove that it is possible to derive a comparability of the aerodynamic parameter of the flow coefficient and thus of the flow rate of the fans. Furthermore, a correlation between the noise reduction potential of the two models can be established through spectral Strouhal number normalization. The proposed aerodynamic and aeroacoustic coherences ensure transferability from the model fan to an upscaled fan and thus allow generalized statements to accurately transfer the aeroacoustic potential of leading edge serrations for different geometrically similar fan applications.}, language = {en} }