Liste des publications
CoSoTIA Project: Decision Supportfor the Choice of Concentrated SolarTechnologies for Electricity Generation
The CoSoTIA (Concentrated Solar Technologies for Industrial Applications)project initiated by the CRTI center in collaboration with the URMPEunit concerns the study and development of CSP solar concentrators for industrialapplications. In the present work, we present decision support tools for thechoice of a solar concentration technology for sites in Algeria. They will be usedfor the comparison between different technologies of solar concentration e.g.:cylindro-parabolic, parabolic, solar tower, etc. The models used include projectcosts and site characteristics; they incorporate also engineering knowledge (economic,social, technical and environmental). The information needed for decisionmakingproduced by these tools is: the total cost of the project, indicators witheconomic, social, technical and environmental aspects. The case studies presentedwere conducted under the SAM Advisor environment, which was developed toevaluate the capacities to implement CSP project in order to produce expertisefor the different actors through an application on a given site (by the client). Fourcase sites in Algeria and for two types of solar concentrator plant are studied andpresented. A comparative study was conducted and for each site the best CSP wasdeduced and commented. Voir les détails
Mots clés : Decision support, Multicriteria analysis, Solar concentration
Thermal analysis of the friction stir welding process based on boundary conditions and operating parameters
Modelling of friction stir welding (FSW) remains a complicated task, as it is crucial to predict the mechanical properties of the final welded part. This research focuses on the numerical simulation aspect of the alloy material AA2195-T8. 3D transient thermal model was applied to simulate the heat transfer phenomena in the welding phase. In this model, the FSW tool is considered as a circular heat source moving in a rectangular plate having a cooling surface and subjected to non-uniform and non-homogeneous boundary conditions. To solve the thermal problem, the finite element method was used as part of a Lagrangian formulation. The obtained results allow us to determine the maximum value of the temperature in the Nugget zone of the welded joint. Sensitivity analysis of the operating parameters was also investigated to determine the thermal cycle and the temperature distribution during this welding process. Our results were successfully compared with the ones available in the literature with good agreement. Voir les détails
Mots clés : Friction Stir Welding, Heat transfer, AA2195-T8, alloy material, parameter characterisation
Effects of Boundary Conditions and Operating Parameters on Temperature Distribution during the Friction Stir Welding Process
This work deals with a numerical simulation of the friction stir welding FSW process of alloy material AA2195-T8. A 3D transient thermal model for simulating the heat transfer phenomena in the welding phase is applied. In this model, the FSW tool is considered as a circular heat source moving in a rectangular plate having a cooling surface and subjected to nonuniformandnon-homogeneousboundaryconditions.ThethermalproblemissolvedusingthefiniteelementmethodaspartofaLagrangianformulation.TheobtainedresultsallowustodeterminethemaximumvalueofthetemperatureintheNuggetzoneoftheweldedjoint.Duringthisprocess,thethermalcycleandthetemperaturedistributionweredeterminedfordifferentvaluesoftheweldingprocessparameters.Theobtainednumericalresultsareingoodagreementwiththeoneavailableintheliterature. Voir les détails
Mots clés : Frictio n Stir Welding, Heat transfer, AA2195-T8
DNS using CLSVOF method of single micro-bubblebreakup and dynamics in ?ow focusing
Numerical simulations are performed to investigate the breakup of air bubble in ?ow focusingcon?guration; the CLSVOF (coupled level set with volume of ?uid) method is employed to track theinterface, which allows a better identi?cation of the liquid–gas interface via a function called level set. TheCFD simulations showed that the velocity ratio, the interfacial tension, the outer channel diameter, thecontinuous phase viscosity, the ori?ce width and length play an important role in the determination of the airbubble’s size and shape. However, at low capillary number, increasing the ?ow velocity ratio gives a smallerbubble size in shorter time, while the increase in interfacial tension leads to a bigger bubble. Moreover, thecarrier ?uid is found to slightly affect the bubbling mechanism, while the smallest bubbles were obtainedwith the smallest ori?ce size. In addition, three breakup regimes are observed in this device: disc-bubble(DB), elongated bubble (EB) and the slug bubble (SB) regime ?ows. This work also demonstrates that theCLSVOF is an effective method to simulate the bubbles breakup in ?ow focusing geometry. In addition, acomparison of our computational simulations with available experimental results reveals reasonably goodagreement. Voir les détails
Mots clés : Bubbling, Multiphase ?ow, CLSVOF, CFD and ?ow focusing
Optimal Tuning of Fractional Order Proportional-Integral-Derivative Controller for WireFeeder System Using Ant Colony Optimization
The goal of this work is to present a robust optimal control approach, in order to improve the speed error-tracking and control capability of a permanent magnet DC Motor (PMDC)driven wire-feeder systems (WFSs) of gas metal arc welding (GMAW) process. The proposed speed controller employs an optimized fractional-order proportional + integral+ derivative (FOPID) controller that serves to eliminate oscillations, overshoots, undershoots and steady state fluctuations of the PMDC motor and makes the wire-feeder unit (WFU) has fast and stable starting process as well as excellent dynamic characteristics. The fixed controller parameters are meta-heuristically selected via an ant colony optimization (ACO) algorithm. Numerical simulations are performed in Matlab/Simulink environment and the performance of the proposed ACO-FOPID controller is validated. The simulation results clearly demonstrate the significantimprovement rendered by the proposed approach in the wire-feeder system's reference tracking performance, torque disturbance rejection capability, and transient recovery time. Voir les détails
Mots clés : gas metal arc welding process, wire-feeder system, fractional-order-proportionalintegral-derivative controller, ant colony optimization algorithm
Arc Welding Current Control Using Thyristor Based Three-Phase Rectifiers Applied to Gas Metal Arc Welding Connected to Grid Network
The purpose of the welding operation is to ensure the continuity of the materials to be assembled in large industrial sectors. This study aims to suggest a topology of the Thyristor based three-phase rectifiers applied to the Gas Metal Arc Welding (GMAW) process connected to the grid network, the output currents are controlled and using various pulsed forms such as square, annealing, and spike pulse operations and investigate and compare between the effects of the three references welding currents structures on the welding current, welding voltage, droplet diameter, and welding quality. To have the best pulse operation, the amplitude and frequency are kept the same for all operations, the application of meshing graphs in the references of welding currents structures, welding current, welding voltage, and droplet diameter can illustrate a clear comparison between them. The simulation results show that the square pulse operation is the best among them. The Single-Sided Amplitude Spectrum (SSAS) method is also applied to the welding current and droplet diameter of the three operations under slow and rapid droplet detachment rates to estimate the droplet detachment frequency. The results show the great success of the SSAS in estimating the precise frequency. Voir les détails
Mots clés : Gas Metal Arc Welding, three-phase rectifier, grid network, SSAS method, welding current, welding voltage, droplet diameter, detachment frequency
Prediction of the Friction Coefficient of 13Cr5Ni2Mo Steel Using Experiments Plans-Study of Wear Behavior
Metal materials used in industrial applications deteriorate under the effect mechanical and chemical phenomena occurring under operating conditions, such as pipes carrying gas or fluid that are subject to internal wall wear. From where an experimental study was conducted through friction tests on supermartensitic stainless steel Cr13Ni5Mo2, in order to estimate the effect of test parameters on friction coefficient and wear behavior of this steel by adopting the factorial plans 22 methodology at two factors (Load "P" and linear sliding "V"), each at two levels (-1, +1). The results have been demonstrated using a mathematical model predicting the coefficient of friction "f" in every point of the study field. The factorial plans make it possible to establish a modeling of the studied phenomenon with a maximum of efficiency and a minimum of experiences. The experimental results showed that the friction coefficient "f" reaches a max value for an applied load P=10N combined with a linear speed V=5cm/s. In addition, the wear morphology of surfaces after the friction test indicates that for 2N and at all speeds, friction is dominated by an abrasive wear mechanism. However, for 10N, it is observed the predominance of adhesive wear with a higher wear rate. Voir les détails
Mots clés : friction, factorial design, Mathematical model, wear mechanism
Plastic Deformation Effect on Wear and Corrosion resistance of Super Martensitic Stainless Steel
The microstructure and the mechanical properties of a super martensitic stainless steel (SMSS) were investigated in this study. Test specimens were taken from seamless tube generally used in oil and gas industries. The specimens were plasti- cally deformed by tension from its as-received state to different levels of elongation at 2%, 10%, and 15%, respectively. The focus was to study the influence of plastic deformation on the tribological behavior against alumina balls in dry conditions and the corrosion resistance in 3.5% NaCl solution. Analysis results showed an abrasive wear as the main wear mechanism. Plastic deformation prior to sliding wear test increases wear resistance as the deformation rate increases. Based on the elec- trochemical experiments, all of the specimens showed an increase in their corrosion resistance i.e., the corrosion potential Ecorr (vs. Ag/AgCl) tends to move toward more noble values with respect to the initial potential. The greatest polarization resistance was displayed by the specimen with 10% of deformation rate. Voir les détails
Mots clés : Super Martensitic Stainless Steel, • Cold deformation, • Wear, • Corrosion
Investigation ?n Dry Sliding Wear Performance and Corrosion Resistance of 13Cr5Ni2Mo Supermartensitic Stainless Steel
This work aimed to study the microstructure, wear and corrosion resistance of supermartensitic stainless steel (SMSS). Heat treatment applied to samples consists of quenching after austenitization at elevated temperature (1250 °C) followed by a double tempering at 650 °C. Conventional mechanical properties, scanning electron microscopy (SEM/EDS) analysis and X-ray diffraction methods (XRD) are used to analyze the microstructure and to evaluate the wear mechanisms. The potentiodynamic polarisation and the electrochemical impedance spectroscoopy (EIS) methods are used to evaluate the corrosion resistance in both the 0.5M H2SO4 and 0.5M NaCl aggressive media. The microstructure is mainly composed with tempered lath martensite, small quantity of retained austenite and carbides. Oxidative and abrasive wear dominated the wear process in dry condition. During the corrosion process, the same mechanism of degradation was found in both the 0.5M NaCl and 0.5M H2SO4. Voir les détails
Mots clés : Supermartensitic steel, microstructure, friction, Wear Corrosion
Thermodynamic investigation on the adhesion and corrosion inhibitionproperties of a non-steroidal anti-inflammatory drug in HCl electrolyteapplied on mild steel material
In this paper, the inhibition mechanism of a pharmaceutical agent, piroxicam, on the corrosion behavior of carbon steel in HCl (1M) solution was investigated. The weight loss technique and quantum chemical calculations were carried out. The determined inhibition efficiency at 298 K was 86.90 % for a concentration of 600 ppm. The adsorption mode of the drug obeys to the Langmuir isotherm model. The free energy of adsorption (ΔGads = −32.84 kJ mol?¹) revealed a spontaneous process with a mixed interaction type, physical and chemical. The thermodynamic parameters (ΔHads and ΔSads) governing the adsorption phenomenon and metal dissolution were investigated and discussed through thermodynamic and kinetic principles. The ΔHads and ΔSads were respectively −17.86 kJ mol?¹ and 50.27 J mol?¹ K?¹ which indicates an exothermic process and an increased disorder at the interface. The DFT method was used to determine the adsorption centers of the chemical structure of the drug. EHOMO (−6.448 eV) reveals a high tendency of the drug to share its electrons with the metal. In addition, the SEM analysis was carried out for the surface characterization of the carbon steel after immersion into the aggressive medium in the absence and presence of the drug substance. Voir les détails
Mots clés : Mild steel, Weight loss, adsorption, DFT