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Chusseau, Maylis. "Contribution à la réduction du bruit d'hélice sur avion monomoteur à pistons". Toulouse 3, 1995. http://www.theses.fr/1995TOU30018.
Pełny tekst źródłaAcevedo, Giraldo Daniel. "Experimental and analytical investigation of the aerodynamic noise emitted by generic distributed electric propulsion wing-propellers configurations". Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0015.
Pełny tekst źródłaThe present thesis investigates experimentally and analytically the acoustic installation effects of a pair of six-bladed side-by-side subsonic propellers installed near a wing's trailing edge. In a significant range of low-and-middle frequencies, the propellers' diameter, wing chord, and propeller-wing distance are smaller than the acoustic wavelengths, reaching a compact regime. This generic configuration mimics future Distributed Electric Propulsion urban aircraft architectures, addressed in the framework of the European Union's H2020 project ENODISE. The installation effects refer to the additional sources of aerodynamic noise caused by blade-wing interaction and their scattering by the wing, compared to the case of isolated propellers. This work aims to find an optimum generic configuration concerning aerodynamic and acoustic standpoints through a parametric study. The idea is to demonstrate not only the ability of the experimental approach to determine optimized configurations but also the potential of analytical models to estimate this sound-scattering effect, which is of primary interest for the preliminary design steps of a system. Firstly, wind tunnel tests are performed as a reference. Secondly, an analytical model is implemented and its predictions are validated with the experimental results. Finally, this will help to find interesting options for propulsion-airframe integration. Wind tunnel tests have been conducted in the anechoic open-jet facility at École Centrale de Lyon. Aerodynamic measurements were taken by static pressure taps on the wing, whereas the aero-propulsive performance was evaluated with load cells. In addition, the far-field sound was measured with a rotating microphone antenna, exploring part of a sphere around the setup. The propellers were tested at a constant rate of 7000 rpm in static conditions. Variations in magnitude and directivity of the sound pressure levels at the first blade passing frequency tones were explored comprehensively for the different cases. The spectral content of selected cases of interest was examined in greater detail, showing the impacts of acoustic scattering, diffraction, reflection, and shielding depending on the propeller position. The results show positions at which there is significant potential for noise attenuation by masking both the tonal and broadband noise content. Reductions of up to 5~dB in the overall sound pressure level and 20 dB in the first blade passing frequency were evidenced. Additionally, the data show that the installation effect is crucial for analyzing tonal propeller noise. In particular, sound radiation is significantly increased when the blade tips operate close to the trailing edge. Furthermore, in the analytical formulation, dipole-like noise sources of the propellers are considered, assuming rigid blades. The sound radiation from the propellers is formulated in three dimensions for characteristic spinning modes of tonal noise. In addition, the half-plane Green's function is used to account for the sound scattering by the wing. A finite-chord correction is applied, and validated by numerical simulations. The results confirmed that the installation effect is crucial for analyzing tonal propeller noise. This approach was quantitatively assessed against the far-field wind tunnel sound measurement. Sound pressure maps show that in the presence of the wing, radiation modes that would be evanescent in free-field can be converted into very effectively radiating patterns if the blade tips of the installed propellers are at a compact distance from the wing trailing edge. This effect tends to increase the radiation efficiency of steady-loading noise, which is most often of secondary importance compared to unsteady-loading noise in free field
Quaglia, Michael. "Méthodes de prévision acoustique semi-analytiques pour un doublet d'hélices contrarotatives isolé". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC063/document.
Pełny tekst źródłaNo abstract
Quaglia, Michaël. "Méthodes de prévision acoustique semi-analytiques pour un doublet d'hélices contrarotatives isolé". Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11781.
Pełny tekst źródłaGiez, Justine. "Effets de charge et de géométrie sur le bruit d'interaction rotor-rotor des doublets d'hélices contra-rotatives". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC005.
Pełny tekst źródłaThe development of alternative propeller systems to turbojets is a main issue for research in the current context of aeronautical transport. Counter rotating open rotors are a candidate solution because they allow reduction of fuel consumption and gas emission. However, noise emissions are still a challenge for these types of configuration, in particular because they cannot benefit from the nacelle and the liners currently used in turbojet. The understanding of acoustic sources and their prediction is necessary in order to be able to reduce noise emission in the near future. Flows in an open-rotor are complex, in particular for the downstream propeller which is the subject of this approach.This work based on a numerical, experimental and analytical study and takes part in the ADOPSYS chair between Safran Aircraft Engines and l’Ecole Centrale de Lyon. This PhD has two main goals. The first one is to complete an experimental study in order to elucidate the behavior of the flow on a swept airfoil and the resulting acoustics, with a possibly developing leading-edge vortex. The measurements will be a data base for further comparison with analytical prediction. The second objective of the PhD consists in developing a semi-analytical modeling of the noise emitted by an airfoil in response to an incoming perturbation, taking into account the loading and geometry effects. A numerical study of a full counter-rotating system was used as a basis for designing the investigated airfoil. The latter was designed so that a leading-edge vortex could be formed on the surface for some angles of attack. The mock-up was then tested in an anechoic wind tunnel of Ecole Centrale de Lyon for various sets of parameters. Flow visualization and wall-pressure measurements indicated the presence of the leading-edge vortex for some angles of attack. The far-field measurements indicated three acoustic regimes, which can be associated with three behaviors of the leading-edge vortex. Source localization measurements corroborate these observations. Analytical predictions of the noise emitted by the airfoil and based on Amiet’s model were also performed. Firstly, the sweep angle is taken into account in the model. Secondly it is applied to the studied airfoil. A better match of the results is found when the sweep is considered, in particular in the perpendicular directions. The model in then extended in order to include the wall-junction. This part is exploratory and should be further developed. Finally, a complementary experimental investigation of the impingement of periodic wakes on the airfoil has been performed, using a system made of rotating bars, mimics true wake interactions. The measurements suggest that the leading-edge vortex has a quasi-steady behavior
Vignaud, Alexandre. "Influence de l'intensité du champ magnétique sur l'imagerie RMN des poumons à l'aide d'hélium-3 hyperpolarisé". Phd thesis, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00003668.
Pełny tekst źródłaMarinus, Benoît. "Multidisciplinary optimization of aircraft propeller blades". Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00692363.
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