Time filter

Source Type

Benhamou A.,University of Hassiba Ben Bouali Chlef | Bounif A.,Oran University of Science and Technology - Mohamed Boudiaf | Maspeyrot P.,PPRIME Institute | Mansour C.,Oran University of Science and Technology - Mohamed Boudiaf
Mechanika | Year: 2014

Elastohydrodynamic (EHD) journal bearings in rotating machine parts are subjected to very severe operating conditions, leading to a reduction in the minimal thickness of the lubricating film which can generate premature wear of the contact. In this work, an analytical method of calculating the minimal thickness of the oil film was proposed. It takes into account the effect of the elastic deformations due to both hydrodynamic pressure and inertia. The elastic deformations are calculated analytically and simultaneously. The connecting - rod bearing body deformations was predicted under low and moderate engine regimes. The correction produced by the introduction of the effect of inertia, have shown a clear difference for the global behaviour. The method was applied for analysis of a General Motors connecting - rod bearing engine. Source

Garcia C.B.,University of Minho | Ariza E.,University of Minho | Tavares C.J.,University of Minho | Villechaise P.,PPRIME Institute
Applied Surface Science | Year: 2012

Microstructural characterization and crystallographic orientation aspects of aluminium doped zinc oxide (ZnO:Al) thin films have been investigated by means of electron backscatter diffraction. ZnO:Al was produced by magnetron sputtering deposition from a ZnO ceramic target containing 2.0 wt% Al 2O 3 and 0.12 wt% Y 2O 3. Both top surface and cross-section analysis were performed. The experimental details concerning specific sample preparation procedures for EBSD investigations are presented. Crystalline texture was described by the inverse pole figure (IPF) maps. Strong texture on the basal plane orientation was observed on the analyzed thin film surface. In accordance with these results obtained from top surface investigations, a strong prismatic texture was found in cross-section analysis. From all these analyses a good description and quantification of the three dimensional configuration of the grains and of their crystallographic texture can be proposed. © 2012 Elsevier B.V. Source

Bonneau V.,SNECMA | Polacsek C.,ONERA | Barrier R.,ONERA | Lewy S.,ONERA | And 2 more authors.
AIAA Journal | Year: 2015

The interaction of wakes generated by a fan with the outlet guide vanes occurring at the blade-passing frequency and its harmonics is mainly responsible for aeroengine tonal noise emission in approach conditions. Conventional rotor-stator interaction models assume axisymmetric rows and quasi-annular ducts. However, the stator of new engines is characterized by nonidentical vanes (so-called heterogeneous outlet guide vane) and integrates two internal bifurcations up to the nacelle outlet. These new technologies invalidate the existing tools adopted by engine manufacturers at the design stage. For this reason, hybrid methodologies based on a three-dimensional unsteady Reynoldsaveraged Navier-Stokes simulation considering the complete geometry of a modern Snecma engine model are investigated in this paper. Unsteady Reynolds-averaged Navier-Stokes simulation output data are postprocessed using different integral methods to assess the impact of the heterogeneity on angular mode distribution (compared to an idealized homogeneous stator) and the effect of bifurcations on downstream propagation. In particular, the Goldstein formulation is extended to loading sources distributed over nonidentical vanes. The harmonic sound power predictions derived from loading noise equations are also compared to a direct calculation of the acoustic intensity obtained by extracting the perturbation fields over prescribed cross sections behind the outlet guide vanes. This method requires a suited spatial filtering process in order to reduce the contribution of vortical waves known for polluting the acoustic field. A modal decomposition of the extracted perturbations on a Fourier-Bessel basis is also proposed to avoid this difficulty. Finally, computational fluid dynamics solutions and acoustic predictions compare reasonably with the available experimental data issued from a half-scale turbofan test. © 2015 by H. Hafsteinsson. Published by the American Institute of Aeronautics and Astronautics, Inc. Source

Luttgens S.,ELSTATIK | Luttgens G.,ELSTATIK | Thulin A.,ATC AB | Paillat T.,PPRIME Institute | Touchard G.,PPRIME Institute
Chemical Engineering and Technology | Year: 2015

In order to contribute to a better understanding of the electrostatic phenomena appearing during splash filling of liquids and to clarify the reasons why this process is suspected to increase static electrification especially due to atomization, accurate experiments of charge measurements were made on droplets of various liquids falling over a large distance (5m). Eleven liquids of different conductivity and surface tension were tested. The results confirm that no charge evolution appears even over a long falling distance. A possible explanation of the static charge increase in splash filling is presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Lane N.J.,Drexel University | Vogel S.C.,Los Alamos National Laboratory | Vogel S.C.,Nuclear Research Center - Negev | Caspi E.N.,Drexel University | And 4 more authors.
Journal of the American Ceramic Society | Year: 2014

Herein, we report on the temperature-dependent crystal structures of Ti 3 AlC 2 and Ti 3 Al 0.8 Sn 0.2 C 2 in the 373-1273 K temperature range, as determined by Rietveld analysis of high-temperature neutron diffraction time-of-flight data. The compositions are 86(1) wt% Ti 3 AlC 2 and 14(1) wt% TiC 0.92(2) for the sample with no Sn, and 95(1) wt% Ti 3(Al 0.8 Sn 0.2) C 2 and 5(1) wt% Ti 2 AlC for the solid solution with Sn. The average linear volumetric thermal expansion is 8.0(2) × 10-6 K-1 for Ti 3 AlC 2 and 8.2(5) × 10-6 K-1 for Ti 3(Al 0.8 Sn 0.2) C 2. The average linear thermal expansion in the a and c directions, respectively, are 7.6(2) × 10-6 K-1 and 8.9(2) × 10-6 K-1 for Ti 3 AlC 2. For Ti 3(Al 0.8 Sn 0.2) C 2, the respective values are 8.0(5) × 10-6 K-1 and 8.6(6) × 10-6 K-1. In the case of the solid solution, the quadratic thermal expansion coefficients are also given. Detailed bond lengths analysis shows that the thermal expansions along the a and c directions are controlled by the thermal expansions of the Ti - C, and Ti - Al bond lengths, respectively. The atomic displacement parameters (ADPs) show that the Al and Sn atoms vibrate with a higher amplitude than the Ti and C atoms. Consistent with first-principles calculations, the ADPs of the Al/Sn site(s) in Ti 3(Al 0.8 Sn 0.2) C2 are lower than the ADPs of Al in Ti 3 AlC 2. © 2013 The American Ceramic Society. Source

Discover hidden collaborations