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Aerodynamic noise sources of the tip flow in the fan stage of turbofan engines

Abstract : The fan stage of turbofan engines is actually responsible for a major part of the noise radiated by an aircraft, whether tonal or broadband, at both approach and take-off operating points. Moreover, the fan noise contribution on future Ultra-High By-pass Ratio turbofan architectures is expected to be amplified. Regarding the growth of global air transport sustained by the emerging countries and the more and more stringent noise certification, engine manufacturers pay particular attention on the understanding, prediction and control of fan noise. Among several physical mechanisms generating the fan noise, the tip clearance noise at the tip of fan blades is considered as a secondary source of noise on the current turbofan architectures and is not accounted for the evaluation of fan noise. The evolution towards Ultra-High By-pass Ratio architectures may bring the tip clearance noise from a secondary source to a primary one. In this context, Large-Eddy Simulations resolving the large eddies and modelling the small ones, are performed on an isolated airfoil and a rig-scaled fan representative of future Ultra-High By-pass Ratio turbofan engine. Based on a comparison with measurements, the numerical method is shown its capacity to recover the unsteady aerodynamics of the tip flow. A wall-modelled approach allows for the computation of turbomachinery applications such as the rig-scaled fan. Moreover, mesh adaptation based on flow quantities appears to be an appropriate methodology to resolve the complex three-dimensional vortical structure of turbomachinery secondary flows, such as the tip flow. Identification functions are also applied to characterise the tip leakage vortex at the tip of fan blades. To bring knowledge for the definition of new models of tip clearance noise, a analysis of tip flow on the two configurations is carried out. Among several aerodynamic source mechanisms of tip clearance noise, the scattering of vortical structures in the gap by the tip edges appears to be the dominant mechanism on Ultra-High By-pass Ratio turbofan engine.
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https://theses.hal.science/tel-03711391
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Submitted on : Friday, July 1, 2022 - 1:23:43 PM
Last modification on : Friday, September 30, 2022 - 10:56:10 AM
Long-term archiving on: : Monday, October 3, 2022 - 4:10:26 PM

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TH_T2825_dlamidel.pdf
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  • HAL Id : tel-03711391, version 1

Citation

David Lamidel. Aerodynamic noise sources of the tip flow in the fan stage of turbofan engines. Other. Université de Lyon, 2022. English. ⟨NNT : 2022LYSEC013⟩. ⟨tel-03711391⟩

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