References of "Bozet, Jean-Luc"
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See detailExperimental validation of a thermal model of a LOx flooded ball bearing
Servais, Christophe ULg; Bozet, Jean-Luc ULg; Kreit, Patrick ULg et al

in Tribology International (2014), 80

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 ... [more ▼]

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 prescribed. 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 forward, in order to understand and anticipate especially the thermal instability described above. [less ▲]

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See detailTest equipments for characterizing the behavior of materials, bearings and dynamic seals in cryogenic fluid environments
Bozet, Jean-Luc ULg; Servais, Christophe ULg; Duquenne, Marc ULg et al

in Space Propulsion 2014 (2014, May)

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 ... [more ▼]

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. [less ▲]

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See detailExperimental Validation of a Thermal Model of a LOx Flooded Ball Bearing
Servais, Christophe ULg; Bozet, Jean-Luc ULg; Kreit, Patrick ULg et al

Conference (2013, September 05)

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 ... [more ▼]

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 forward, in order to understand and anticipate especially the thermal instability described above. [less ▲]

Detailed reference viewed: 17 (3 ULg)
See detailInfluence of tribology of cage material on ball bearing cage instability
Servais, Christophe ULg; Duquenne, Marc ULg; Bozet, Jean-Luc ULg

in 15th European Space Mechanisms and Tribology Symposium 2013 (2013, September)

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 ... [more ▼]

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. This is based on pin-on-disk tests and on a numerical approach. [less ▲]

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See detailInfluence of liquid oxygen environment on the tribological behaviour of PCTFE/440C steel contact
Cautain, Satia; Duquenne, Marc ULg; Robbe-Valloire, François et al

in Space Propulsion 2012 (2012)

This article proposes a tribological study of contact between polychlorotrifluoroethylene (PCTFE) and 440C steel. The tests are performed on a pin-on-disc cryotribometer specifically designed to overcome ... [more ▼]

This article proposes a tribological study of contact between polychlorotrifluoroethylene (PCTFE) and 440C steel. The tests are performed on a pin-on-disc cryotribometer specifically designed to overcome the additional issues due to the use of cryogenic fluid. Test parameters such as speed, contact pressure and sliding distance are kept the same for the whole campaign, leaving the environment as the only variable. This study focuses on the analysis of friction, wear of PCTFE pin and appearance of disk after tests. The test results show the influence of the state of environment (gas or liquid), its temperature and its reactivity (neutral or oxidative) on the contact behaviour. [less ▲]

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See detailLiquid oxygen compatibility of materials for space propulsion needs
Bozet, Jean-Luc ULg; Heyen, Georges ULg; Dodet, Claude ULg et al

in 4TH EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES (EUCASS) (2011)

Since the origin, the use of liquid oxygen as oxidizer is widespread in space propulsion. It has been the source of numerous incidents. Many materials can burn violently in an oxygen enriched environment ... [more ▼]

Since the origin, the use of liquid oxygen as oxidizer is widespread in space propulsion. It has been the source of numerous incidents. Many materials can burn violently in an oxygen enriched environment when ignited. Consequently, it is mandatory to perform oxygen compatibility tests. In the present work, compatibility tests are impact tests and auto ignition tests. Both standardized test methods are illustrated by test results on polymeric materials (i.e. fluorinated resins, polyimides, polyetherketone) for seals and ball bearing cage. For future needs, in order to face the increase of pressure of injection of propellants in cryogenic engines, the adiabatic compression test has been identified as well suited for qualifying materials as oxygen compatible in highly constraining conditions. Details on the test procedure and on the installation available at the Université de Liège are presented. [less ▲]

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See detailComportement tribologique du contact PCTFE/acier 440C en azote de la température cryogénique à l'ambiante
Cautain, Satia; Robbe-Valloire, François; Bozet, Jean-Luc ULg

in Journées Internationales Francophones de Tribologie (2011)

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See detailFluid Bearings in LOX
Bozet, Jean-Luc ULg

Conference (2004, December)

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See detailTribology of SiC/SiC Ceramic Matrix Composites in Liquid Oxygen in Relation to the Design of Hydrostatic Bearings
Bozet, Jean-Luc ULg; NELIS, M.; LEUCHS, Martin et al

in Tribotest Journal (2003), 10(2), 105-115

This paper aims with the characterization of ceramic matrix composites for bearing applications in LOX. First, compatibility tests have been performed to assume the safety and feasibility of further ... [more ▼]

This paper aims with the characterization of ceramic matrix composites for bearing applications in LOX. First, compatibility tests have been performed to assume the safety and feasibility of further research operations. Then tribology tests were made on a pin-on-disc apparatus using LOX as working environment. The measurement of friction and wear allowed a comparison between different kinds of CMC and steel 440C materials. As a logical approach, a real geometry test rig is now being built up. The design of a hybrid journal bearing has been finished and the manufacturing of the rig components started. [less ▲]

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See detailCeramic Journal Bearing in Cryogenic Turbo-Pumps
Nelis, M.; Bozet, Jean-Luc ULg; BICKEL, M. et al

in European journal of mechanical and environmental engineering (2003), 48(no2), 73-80

The availability of components built in CMC technology forms in major areas a prerequisite for the realisation of future reusable launcher engines. Apart from the efforts to introduce CMC components in ... [more ▼]

The availability of components built in CMC technology forms in major areas a prerequisite for the realisation of future reusable launcher engines. Apart from the efforts to introduce CMC components in the hot areas of the engine like nozzles and thrust chambers there exists an important optimisation potential in the engines through the use of CMC components in (cryogenic) turbo-pumps. By replacement of the ball bearings in the pumps by journal bearings, a significantly higher lifetime can be obtained and the inherent limitation of the turning speed of the pumps can be widely extended. The CMC journal bearings of MAN have proven their quality and reliability in numerous applications in industrial pumps. Based on this experience a research program was initiated by DLR and funded by means of the BMBF and MAN to investigate the use of this bearing type under the conditions of a cryogenic turbo-pump. Major results are presented in this paper. [less ▲]

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See detailMatériaux en céramique SiC/SiC pour paliers lisses sous oxygène liquide: études expérimentales
Bozet, Jean-Luc ULg; Nélis, Marc; Leuchs, M.

Conference (2003, May)

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See detailTheoretical and experimental characterization of polyimide dry bushings
Bozet, Jean-Luc ULg; POYSAT, P.; MEROT, P.

in IMechE Conference Transactions (2001)

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See detailModelling of friction and wear for designing cryogenic valves
Bozet, Jean-Luc ULg

in Tribology International (2001), 34(4), 207-215

From a tribological point of view, the selection of materials for seals for valves of cryogenic rocket engines is a critical issue for the designer. Due to the lack of comprehensive information on this ... [more ▼]

From a tribological point of view, the selection of materials for seals for valves of cryogenic rocket engines is a critical issue for the designer. Due to the lack of comprehensive information on this topic. data have been obtained in the framework of research programmes. In the first step, two polymers potentially usable for sealing cryogenic fluids were identified, They were submitted to general test conditions to gain some fundamental understanding of their tribological behaviour when immersed in a cryogenic fluid. This fundamental understanding proved to be helpful for an efficient technical approach. This approach with the test conditions as close as possible to those met in real valves has been used in the second step. In order to obtain the best information with the minimum number of tests, the statistical method of Doehlert has been adopted. The use of such a method led to the construction of surface response for modelling friction and wear. These surfaces and their associated equation are directly and easily usable by the designer, This way of treating technical tribological problem is illustrated by an example. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling of friction and wear for cryogenic valve seals of rocket engines
de Lamotte, E.; Bozet, Jean-Luc ULg; KABUYA, A.

in Proceedings of 8th European Space Mechanisms and Tribology Symposium (2000)

Based on the experimental results, earlier work presented a first attempt at the statistical modelling of the friction and wear valves and seals of rocket engines must withstand. Available friction ... [more ▼]

Based on the experimental results, earlier work presented a first attempt at the statistical modelling of the friction and wear valves and seals of rocket engines must withstand. Available friction coefficients and wear rates (as defined in Archard’s equation) were fitted against two independent variables : sliding speed and contact pressure. The computations yielded second-degree polynomials and the corresponding response surfaces. However, it was felt that a statistical design of experiments to reduce the test activities and maximise result quality was needed. A detailed analysis led to the choice of Doehlert’s approach, with a contribution of the general equiradial design. Testing was performed with a pin-on-disk tribometer capable of working at room temperature (RT) and under liquid nitrogen (at 77 K). The results pertaining to two examples are discussed. Statistical as well as practical aspects of the work performed and consequences of the results are covered : based on correlation factors and other mathematical indicators, on the general profile of the response surfaces and on requirements for use, the tribological properties of the considered materials are illustrated, leading to their eventual usefulness in cryotechnic equipment and space applications. [less ▲]

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See detailNanoindentation investigation of Ti/TiN multilayers films
Ben Daia, M.; Aubert, P.; Labdi, S. et al

in Journal of Applied Physics (2000), 87(11), 7753-7757

The hardness of Ti/TiN nanolaminated films is investigated in this study. Monolithic Ti and TiN films and Ti/TiN multilayers were deposited on silicon substrates by radio-frequency sputtering. The period ... [more ▼]

The hardness of Ti/TiN nanolaminated films is investigated in this study. Monolithic Ti and TiN films and Ti/TiN multilayers were deposited on silicon substrates by radio-frequency sputtering. The period thickness of multilayers was decreased from 20 to 2.5 nm. Grazing x-ray reflectometry showed that the modulation of composition of Ti/TiN multilayers exists for all the period thickness considered. From nanoindentation measurements, we determined the hardness and Young's modulus of multilayers. Hardness increased with decreasing period thickness to go beyond the rule-of-mixture value for samples with period thickness of Lambda less than or equal to 5 nm. The maximum hardness, 1.6 times higher than the value obtained by the rule of mixture, is obtained for Lambda=2.5 nm. Our results are compared to a dislocation-based model previously introduced by Lehoczky. (C) 2000 American Institute of Physics. [S0021-8979(00)09411-1]. [less ▲]

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See detailMechanical properties of Al/Al2O3 nanolaminated films: correlation to microstructure
Ben Daia, M.; Aubert, P.; Labdi, S. et al

in Surface & Coatings Technology (2000), 125(1-3), 196-200

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate ... [more ▼]

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate temperatures: T-s= 25 degrees C and T-s= -90 degrees C. The period thickness of multilayers was lowering from 40 to 2 nm. From nanoindentation measurements, it appears that the hardness of multilayers has an intermediate value between those of metal (Al) and ceramic (Al2O3). The tribological test was conducted by the pin-on-disc method. The T-s=25 degrees C deposited multilayers, as well as single films, demonstrated poor wear resistance. The best wear resistance was obtained for multilayers deposited at the lowest substrate temperature (T-s= -90 degrees C). The results are ill good agreement with structural characterization. X-ray reflectometry demonstrated that the multilayer character of Al/Al2O3 is more pronounced for T-s= -90 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved. [less ▲]

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See detail100km/h en 1899 : la voiture électrique de Jenatzy
Bozet, Jean-Luc ULg

Scientific conference (2000)

Detailed reference viewed: 47 (2 ULg)