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ORBi Open Repository and Bibliography (186,317 recursos)
In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision). This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.

Engineering, computing & technology => Aerospace & aeronautics engineering

Mostrando recursos 1 - 20 de 695

1. Experimental Validation of a Thermal Model of a LOx Flooded Ball Bearing - Servais, Christophe; Bozet, Jean-Luc; Kreit, Patrick; Guingo, Sébastien
Ball bearings of turbopumps of rocket engines work in very singular conditions; they are flooded into liquid oxygen or liquid hydrogen. Therefore, the use of any conventional lubricants (oil or grease) is proscribed. Although cryogenic fluids can cool this kind of ball bearing, they cannot separate the surfaces in contact. As a result, there is a significant increase in frictional power losses. This paper presents tests performed on a cryotechnic ball bearing flooded in liquid oxygen. The test results showed that beyond a critical loading of the bearing, a sudden increase in temperature occurred. A thermal model is also put...

2. Experimental validation of a thermal model of a LOx flooded ball bearing - Servais, Christophe; Bozet, Jean-Luc; Kreit, Patrick; Guingo, Sébastien
Peer reviewed

3. Test equipments for characterizing the behavior of materials, bearings and dynamic seals in cryogenic fluid environments - Bozet, Jean-Luc; Servais, Christophe; Duquenne, Marc; Kreit, Patrick; Dodet, Claude
Test rigs available at the cryogenic test site of the University of Liège concern quite delicate high rotational speed components of cryogenic rocket engines. That is to say bearings and dynamic seals. These rigs gave successfully important results for the understanding and the improvement of the running of the so called components. Until now the test zone is equipped for handling liquid oxygen and liquid nitrogen.

4. Influence of tribology of cage material on ball bearing cage instability - Servais, Christophe; Duquenne, Marc; Bozet, Jean-Luc
By creating a solid lubricant thickness on both bearing races, a cage material of cryogenic ball bearing plays a significant role in the good dynamical behavior of the cage. This role is essential because of the lack of conventional lubricant into this kind of bearing. In this paper, a method able to identify if a particular potential cage material can correctly fulfill its function is described. In other words, if it can lead to a stable movement of the cage. From the identification of fundamental tribological parameters governing the cage behavior, this method presents an example of ranking of such materials....

5. Experimental investigation of a Scroll unit used as a compressor and as an expander in a reversible HP/ORC unit - Dumont, Olivier; Quoilin, Sylvain; Lemort, Vincent
Peer reviewed

6. Robust optimal rendezvous using differential drag - Dell'Elce, Lamberto; Martinusi, Vladimir; Kerschen, Gaëtan
The practical realization of the differential drag technique for orbital relative maneuvers must cope with the several and severe uncertainty sources affecting drag modeling. Neglecting these uncertainties might yield to oversimplified solutions whose representation of a real-life scenario is questionable. The first outcome of this study consists in the synthesis of a robust optimal controller which combines differential flatness theory and the scenario approach to generate a reference path which can be easily followed. The second outcome is the characterization of the relevant uncertainties of the differential drag problem, with a special focus on the aerodynamic force. The developments are...

7. Aircraft Engine Gas Path Diagnostic Methods: Public Benchmarking Results - Simon, Donald; Borguet, Sébastien; Léonard, Olivier; Zhang, Xiaodong
Peer reviewed

8. Advanced Aeroservoelastic Modeling for Horizontal axis Wind Turbines - Prasad, Chandra Shekhar; Chen, Qiong-zhong; Dimitriadis, Grigorios; Bruls, Olivier; D'Ambrosio, Flavio
Peer reviewed

9. Analysis versus synthesis for trending of gas-path measurement time series - Borguet, Sébastien; Léonard, Olivier; Dewallef, Pierre
Peer reviewed

10. Résonance locale et caractérisation de défauts de délaminage par vibrothermographie - Demy, Philippe
La vibrothermographie est une méthode de thermographie active utilisée en contrôle non destructif qui présente des caractéristiques intéressantes et peu communes pour la détection de défauts. Cependant, la méthode souffre d’un manque de fiabilité des résultats lié au chaos acoustique inhérent à la nature du contact pour la stimulation. La principale innovation de cette thèse consiste à étudier et proposer une méthode alternative à la vibrothermographie classique à partir d’un couplage linéaire obtenu par collage. La mise en évidence et l’étude d’un phénomène de résonance locale de délaminage a permis la mise au point d’une technique performante et fiable pour...

11. Wind Tunnel Testing of a VTOL MAV Propeller in Tilted Operating Mode - Theys, Bart; Dimitriadis, Grigorios; Andrianne, Thomas; Hendrick, Patrick; De Schutter, Joris
This paper presents experimental results of the full 3-axis force vector and 3-axis moment vector acting on a propeller, commonly used for a Vertical Take Off and Landing Micro Aerial Vehicle (VTOL MAV). Measurements were carried out in a wind tunnel using a high resolution 6-axis force/moment sensor embedded in a customized test rig at several wind speeds, propeller rotational speeds and angles of the propeller shaft with respect to the air stream. Results show strong moments acting on the propeller in forward flight and unstable conditions in descending flight. Power calculations reveal a decrease in power consumption during slow...

12. Validation of differential drag propellantless maneuvers using 6 DoF simulations and stochastic dynamics - Dell'Elce, Lamberto; Kerschen, Gaëtan
Differential drag is regarded as a promising technique in low-Earth orbits, since it allows to turn the often-undesired drag perturbation into a control force for relative maneuvers. Nonetheless, relevant uncertainties in drag modeling make its practical realization a challenge, especially if no other propulsive means is available to accommodate them. The main outcome of this study is the identification and characterization of the uncertainty sources affecting differential-drag-based maneuvers. This characterization is carried out by using statistical methods in conjunction with mechanical modeling considerations to infer a probabilistic model of the sources from observed data. The developments are illustrated in the...

13. Muti-scale methods with strain-softening: damage-enhanced MFH for composite materials and computational homogenization for cellular materials with micro-buckling - Wu, Ling; Nguyen, Van Dung; Adam, Laurent; Doghri, Issam; Noels, Ludovic
In this work, multi-scale methods with strain softening are developed in the contexts of damage modeling for composite laminates and of buckling analyses in cellular materials. First, an anisotropic gradient–enhanced continuum damage model is embedded in a mean–field homogenization (MFH) process for elasto-plastic composites. The homogenization procedure is based on the newly developed incremental secant mean-field homogenization formulation, for which the residual stress and strain states reached in the phases upon a fictitious elastic unloading are considered as starting point to apply the secant method. The mean stress fields in the phases are then computed using isotropic secant tensors, which are...

14. PhD committe presentation - 3rd year - Serino, Gennaro

15. Cryogenic and Thermal Control for Vacuum Facilities Development in KARI - Guiot, Marc; Jamotton, Pierre; Grodent, Christophe; Moon., Guee-Won; Cho., Hyokijn; Seo, Hee-Jun; Lee., Sang-Hoon

16. Probabilistic Assessment of the Lifetime of Low-Earth-Orbit Spacecraft: Uncertainty Characterization - Dell'Elce, Lamberto; Arnst, Maarten; Kerschen, Gaëtan
Peer reviewed

17. Turn key fully controlled thermal system for space applications - Guiot, Marc; Jamotton, Pierre; Grodent, Christophe; Suchail, Jean-Luc; Moon., Gueewon; Heejun, Seo

18. Ray tracing enhancement for space thermal analysis: isocell method - Jacques, Lionel; Masset, Luc; Kerschen, Gaëtan
The finite element method (FEM) is widely used in mechanical engineering, especially for space structure design. However, FEM is not yet often used for thermal engineering of space structures where the lumped parameter method is still dominant. Radiative exchange factors (REFs), used to calculate radiative thermal exchanges in space, are usually computed through Monte Carlo ray-tracing. Due to the large number of elements composing a FE model, the computation of the REFs is prohibitively expensive. In the frame of a global approach, several research axes will be investigated to reduce the computational effort of the REFs with FEM. The first...

19. Ray tracing enhancement for space thermal analysis: isocell method - Jacques, Lionel; Masset, Luc; Kerschen, Gaëtan
The finite element method (FEM) is widely used in mechanical engineering, especially for space structure design. However, FEM is not yet often used for thermal engineering of space structures where the lumped parameter method is still dominant. Radiative exchange factors (REFs) are usually computed through Monte Carlo ray-tracing. Due to the large number of elements composing a FE model, the computation of the REFs is prohibitively expensive. The developments of the new Isocell quasi-Monte Carlo ray tracing method are presented. The Isocell method enhances the uniformity of the generated quasi-random sequence of ray directions and leads to faster convergence. It...

20. Experimental study of wings undergoing active root flapping and pitching - Abdul Razak, Norizham; Dimitriadis, Grigorios
Peer reviewed

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