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Braham A.,Unite de Recherche Materiaux | Braham A.,Tunisian National Institute of Applied Sciences and Technology | Lachiri Z.,SiRF | Lachiri Z.,Tunisian National Institute of Applied Sciences and Technology
International Review of Electrical Engineering | Year: 2010

In induction machines, motor current signature analysis has been tested in many industrial cases with good results. However, this method does not always achieve successfully results to detect broken-rotor-bar under variable load torque. Recent advances on signal processing techniques have provided more powerful tools for faults diagnosis. This paper proposes a novel approach based on Power Spectrum Density estimation (PSD) to diagnose and detect broken-rotor-bar faults in induction motor under different levels of load. This paper also analyses three different spectral decomposition methods applied to induction machine stator current, namely Welch, Burg and Multiple Signal Classification (MUSIC). Based on different power spectral estimation concepts, the frequency resolution, variance and detection capability are different from each other according to the set of parameters used. The proposed methodology aims to determine which spectral estimate method best suited for implementation in an automated system for fault detection. Also, the PSD estimate is used for feature extraction and aims at identifying the descriptors that show high variability between different classes and thus would help distinguishing between them. Various scenarios are examined using data sets of stator current signals from experiments under different load, and the results are compared to obtain the best performance for automated process. © 2010 Praise Worthy Prize S.r.l. - All rights reserved. Source


Ait-Djafer A.Z.,Algerian Center de Developpement des Techniques Avancees | Saoula N.,Algerian Center de Developpement des Techniques Avancees | Aknouche H.,Unite de Recherche Materiaux | Guedouar B.,Algerian Center de Developpement des Techniques Avancees | Madaoui N.,Algerian Center de Developpement des Techniques Avancees
Applied Surface Science | Year: 2015

The aim of this study is to investigate the influence of plasma deposition parameters (the pressure and the substrate bias voltage Vs) on structure, surface morphology, hardness and electrochemical behavior (studied by potentiodynamic polarization and optical microscope (OM) in aggressive environment NaCl 3.5 wt%) of TiAlN coatings. The coatings were deposited by reactive RF magnetron sputtering (13.56 MHz). They were carried out during 60 min and their thickness was approximately 1 μm. Structural analysis shown that TiAlN coating crystallized in cubic (fcc) and hexagonal (hcp) structure with orientations in (1 0 0), (1 1 1), (2 0 0), (1 1 0), (2 2 0) and (3 1 1) planes. The deposited coatings present maximum hardness (H = 25.75 GPa) and Young's modulus (E = 479.82 GPa) at low pressure (20 mTorr) and -60 V of negative substrate bias. Also, mechanical properties (H&E) were strongly influenced by coatings density and grain size. Electrochemical tests revealed that XC48 steel substrate covered with TiAlN coating exhibits excellent corrosion resistance. © 2015 Elsevier B.V. All rights reserved. Source


Mabrouki J.,Unite de Recherche Materiaux | Abbassi M.A.,Unite de Recherche Materiaux | Guedri K.,University of Umm Al - Qura | Omri A.,Unite de Recherche Materiaux | Jeguirim M.,CNRS Mulhouse Institute of Materials Science
Fuel | Year: 2015

Abstract The main purpose of this present work is to optimize the biofuel production from the fast pyrolysis of three palm oil residues, namely palm shell (PS), empty fruit bunch (EFB) and mesocarp fiber (MF). Hence, a biofuel process is simulated using SuperPro Designer (SPD) software. The simulation includes pretreatment, fast pyrolysis, product collection, and upgrading sections. The developed SPD model was validated firstly with published data of the fast pyrolysis of wood oak in fluidized bed reactor. Secondly, the influence of the operating conditions such as pyrolysis reactor temperature and residence time on the fast pyrolysis of the different residues was examined. The obtained results indicate that temperature at 550 C is suitable for obtaining a maximum liquid yield. Moreover, it was found that 0.5 s is the optimized residence time to maximize this liquid yield. Above the optimum residence time, an increase in the gas fraction and a decrease of the bio-oil and char fractions are observed. Comparison of the different residues indicates that the higher yield of liquid fraction was obtained from the EFB and MF while pyrolysis of the PS produced a higher yield of char. These product yields were strongly correlated to the biomass polymer components. The obtained correlation was in agreement with the products yields found in literature for various biomass sources. The developed model provides very useful information about different conditions of pyrolysis for oil palm residues and product yields. Moreover, the model can be generalized and help to assist in the optimization of the fast pyrolysis process of different biomass without performing heavy experimental investigations. Such model will contribute strongly to the intensification and the improvement of the biomass fast pyrolysis. © 2015 Elsevier Ltd. Source


Mejri I.,Unite de Recherche Materiaux | Mahmoudi A.,Unite de Recherche Materiaux
Chemical Engineering Research and Design | Year: 2015

This paper examines the natural convection in an open cavity with a sinusoidal thermal boundary condition. The cavity is filled with a water-Al2O3 nanofluid and subjected to a magnetic field. Lattice Boltzmann method (LBM) is applied to solve the coupled equations of flow and temperature fields. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number of the base fluid, Ra=103 to 106, Hartmann number varied from Ha=0 to 60, the phase deviation (γ=0, π/4, π/2, 3π/4 and π) and the solid volume fraction of nanoparticles between ϕ=0 and 6%. Results show that the heat transfer rate decreases with the increase of Hartmann number and increases with the rise of Rayleigh number. At Ha=30 and Ra=103 to 105, for all phase deviations the addition of nanoparticles increases heat transfer rate. Also, at low Rayleigh number (Ra≤104) the highest heat transfer rate is obtained for γ=π/2. © 2015 The Institution of Chemical Engineers. Source


Mejri I.,Unite de Recherche Materiaux | Mahmoudi A.,Unite de Recherche Materiaux
Fluid Dynamics and Materials Processing | Year: 2015

This paper examines natural convection in an open cavity with a sinusoidal thermal boundary condition. The cavity is filled with a water-Al2O3 nanofluid and subjected to a magnetic field. The Lattice Boltzmann method (LBM) is applied to solve the coupled equations of flow and temperature. The study has been carried out considering parameters in the following ranges: Rayleigh number of the base fluid, Ra = 103 to 106, Hartmann number varied from Ha = 0 to 60, phase deviation (γ = 0,π=4,π=2, 3π=4 and π) and solid volume fraction of nanoparticles between ø= 0 and 6%. Results show that the heat transfer rate decreases with the Hartmann number and increases with Rayleigh number. At Ha = 30 and Ra = 103-105, for all phase deviations the addition of nanoparticles increases the heat transfer rate. Also, at low Rayleigh number (Ra≤ 104) the highest heat transfer rate is obtained for γ = π=2. © 2015 Tech Science Press. Source

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