Anul XX (2013), Nr. 1

COVER

TABLE OF CONTENTS

ARTICLES

Dynamic Impact Test of the Railing with Dissipative Elements
Eugen-Marius Afronie , Tiberiu Stefan Manescu, Constantin Vasile Bîtea

By definition, the railing is a wall or a railing of little height witch serves to delimit the edge of a road, a bridge, aimed at stopping vehicles and restoration mainly on carriageway, pedestrians and conveyance of other road users.

Keywords: railing, steel, deformation, protection, safety

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Fuzzy Logic Based Speed Control System for Three-Phase Induction Motor
Marwan A. Badran, Mostafa A. Hamood, Waleed F. Faris

Three-phase induction motors have been used in a wide range of industry applications. Using modern technology, the speed of induction motor can be easily controlled by variable frequency drives (VFDs). These drives use high speed power transistors with various switching techniques, mainly PWM schemes. For several decades, conventional control systems were applied to electric drives to control the speed of induction motor. Although conventional controllers showed good results, but they still need tuning to obtain optimum results. The recent proposed control systems use fuzzy logic controller (FLC) to enhance the performance of induction motor drives. In this paper, a fuzzy logic based speed control system is presented. The proposed controller has been designed with MATLAB/SIMULINK software, and it was tested for various operating conditions including load disturbance and sudden change of reference speed. The results showed better performance of the proposed controller compared with the conventional PI controller.

Keywords: Electric Drive, PI controller, Fuzzy Logic Controller

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Modeling of Discontinuities in Resistance Structures due to Corrosion
Daniel Bobos

The corrosion process is a process that produces significant negative effects on the resistance structures by reducing their section and by deterioration of mechanical properties of materials. In this paper are presented some notions about the corrosion process, types of corrosion encountered and types of geometric models that can be used for analytical calculation and for numerical simulation using finite element analysis programs, of the effects produced in the corrosion process on the natural frequency of the structure elements.

Keywords: corrosion, geometric model, natural frequencies

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The Performance Evaluation of Overall Heat Transfer and Pumping Power of ?-Al2O3/water Nanofluid as Coolant in Automotive Diesel Engine Radiator
Navid Bozorgan, Komalangan Krishnakumar, Nariman Bozorgan

The efficiency of ?-Al2O3/water nanofluid as coolant is investigated in the present study. ?-Al2O3 nanoparticles with diameters of 20 nm dispersed in water with volume concentrations up 2% are selected and their performance in a radiator of Chevrolet Suburban diesel engine under turbulent flow conditions are numerically studied. The performance of an automobile radiator is a function of overall heat transfer coefficient and total heat transfer area. The heat transfer relations between nanofluid and airflow have been investigated to evaluate the overall heat transfer and the pumping power of ?-Al2O3/water nanofluid in the radiator with a given heat exchange capacity. In the present paper, the effects of the automotive speed and Reynolds number of the nanofluid in the different volume concentrations on the radiator performance are also investigated. As an example, the results show that for 2% ?-Al2O3 nanoparticles in water with Renf=6000 in the radiator while the automotive speed is 50 mph, the overall heat transfer coefficient and pumping power are approximately 11.11% and 29.17% more than that of water for given conditions, respectively. These results confirm that ?-Al2O3/water nanofluid offers higher overall heat transfer performance than water and can be reduced the total heat transfer area of the radiator.

Keywords: Automotive Diesel Engine Radiator, Nanofluid, Turbulent Flow, Overall Heat Transfer, Pumping Power

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Study of Finite Element Number Influence over the Obtained Results in Finite Element Analyses of a Mechanical Structure
Ana-Maria Budai

This paper present the results of a study that was made to establish the influence of finite element number used to determined the real load of a structure. Actually, the study represent a linear static analyze for a link gear control mechanism of a Kaplan turbine. The all analyze was made for the normal condition of functioning having like final scope to determine de life time duration of mentioned mechanism.

Keywords: linear, static, analyze, link, finite element

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Cavitation Erosion Research for AlSi12 Alloy Tested at Different Time Periods
Daniel Chirus, Marian-Dumitru Nedeloni

This paper presents cavitation erosion research for 2 batch of an AlSi12 alloy. The tests were made on a cavitation stand in laboratory, using the stationary specimen method. This alloy is not subject to cavitation, but the experimental research highlight the behavior of AlSi12 alloy when the time periods are different. The research results are presented through graphs and representative images.

Keywords: cavitation erosion, AlSi12 alloy, time periods

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Study of Phosphating Process for Artillery Pipes Subjected to Mechanical Self-shrinkage with Mandrel
Ioan Ciorba

This paper present the results of a study that was made to establish the optimal parameters of phosphating process for artillery pipes. The optimal parameters that were determined after analysis are: the temperature of phosphating solution respectively the holding time in the phosphate bathroom to obtain a maximum thickness of phosphate layer.

Keywords: phosphate, artillery, pipes, self-shrinkage, mandrel

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Influence of the Rib Radius on the Maximum Stress and Deformations of a Corner Bracket
Vasile Cojocaru

The influence of the radius of circular ribs on the maximum stresses and deformations of a corner bracket was analyzed. The results were obtained using simulations based on finite element method. Two geometries were studied: with one and two ribs. For each of these two geometries the radius of the ribs was ranged between 3 mm and 9 mm. The parts were subjected to bending. The simulations show that the increase of the ribs radius generates a substantial decrease of the maximum stresses and the maximum deformations.

Keywords: rib radius, stresses, deformations, finite element method, corner bracket

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The Influence of Hydraulic lay out on the Performances of the Hydraulic Turbine from HPP Raul Alb
Adrian Cuzmos, Nicolae Brebu, Viorel Campian, Ioan Ion, Cosmin Dumbrava

At the commissioning of HPP Raul Alb hydro units it has been found that the hydro units were unable to achieve the guaranteed maximum power. The present work paper presents the results of the tests performed in order to determine the maximum power it can reach these two hydro units in single and parallel operating mode.

Keywords: turbine, hydro unit, power, turbine power, hydraulic lay out

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Intex Tests Performed on Hydro Unit no2 from HPP Ruieni before and after Refurbishment
Adrian Cuzmos, Nicolae Brebu, Viorel Campian, Cosmin Dumbrava

The paper work presents the results of index tests performed on HPP Ruieni hydro unit no2 before and after refurbishment, using for discharge measurements the Winter-Kennedy method.

Keywords: Index tests, hydro unit, hydraulic turbine, wicket gates, Winter-Kennedy method

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Determine the Correlation between Wicked Gates Angles and Servomotors Strokes for Asymmetric Hydrofoil
Daniel Daia, Dorian Nedelcu

The paper describe the results obtained from theoretical calculus of the kinematics of the wicked gates for the correlation: ao=f(a); aor=ao/Do(a); S=f(a) and propose analytical formulas for ao=f(a) correlation, applicable to 16, 24 wicked gates blade number and asymmetrical hydrofoils; also, numerical results compared with graphical values are presented.

Keywords: Wicked gates, kinematics, asymmetric hydrofoil

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Optimal Encoding of Data in Data Transmission Channels
Silviu Draghici, Cornelia Anghel Drugarin, Cristian Chioncel

This paper aims to present the methods of achieving an optimal encoding in the data communication channels. After a short description of the communication channel and of the data communication channel types, follow briefly a few notions of the data channel enthropy, information, transinformation, with their properties, definitions and mathematical relations connecting them. Chapter 2 presents the concept of optimal code, following a detailed description (using two suggestive examples) of the two main methods used to obtain an optimal code: Shannon-Fano and Huffman.

Keywords: optimal code, communication channel, entropy, information, transition functions

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Modal Analysis of Thin Plates with Damage Simply Supported on all Edges
Cornel Hatiegan, Gilbert-Rainer Gillich, Nicoleta Gillich, Marius Tufoi, Mihaela Raduca

This paper presents the natural frequencies obtained by modal analysis for five types of rectangular thin plates. These plates are simple supported on all edges, and are without damage, with a lateral damage and with a damage placed in the in center, in both cases two types of damage being used. We compared the results and highlighting the way how natural frequencies changes due to damage.

Keywords: thin plates, natural frequency, vibration, damage

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Equation of Motion and Determining the Vibration Mode Shapes of a Rectangular Thin Plate Simply Supported on Contour Using MATLAB
Cornel Hatiegan, Gilbert-Rainer Gillich, Eugen Raduca, Marian-Dumitru Nedeloni, Lenuta Cîndea

This paper presents the differential biharmonic equation of thin plates through which, the vibration mode shapes for a rectangular thin plate simply supported on contour were obtained. Also, the first four vibration mode and the first four natural frequencies of this rectangular thin plate of steel, were obtained. Using MATLAB software, the vibration mode shapes were graphically represented.

Keywords: Equation of motion, vibration mode shapes, MATLAB

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Study of Geometric Model Car Body through the Finite Element Mesh
Cornel Iacob-Mare

The paper proposes an analysis of a freight wagon body structure with high walls that has platform to maneuver through study recommended medium for geometric model finite element mesh type Shell63.

Keywords: finite element, meshing, wagon bodz

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Effective Stiffness and Period of Friction Bearing Devices with one Concave Sliding Surface for Different Load Conditions
Vasile Iancu Camelia Stefania Jurcau, Gilbert-Rainer Gillich

The friction pendulum system is a passive earthquake device used for a seismic isolation of buildings, bridges and other types of structures; their purpose is to protect, control and limit the energy transfer from the soil to the structure and fully dissipate seismic energy. In the paper we determine the stiffness and effective period of the friction pendulum system with one sliding surface for different levels of horizontal load..

Keywords: earthquake isolation, friction pendulum, structural integrity, stiffness

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Contributions to the Structural Analysis of the Double Gear Harmonic Transmission
Draghita Ianici

In this paper, we present the construction and functioning of a new constructive variant of harmonic drive called double gear harmonic transmission (DGHT). In the second part of the paper, we present the desmodromy analysis of the DGHT considering the planar approach of the respective mechanism. At establishing the mobility, class and order of the DGHT we have used the procedure of instantaneous– isokinetic transformation wich followed the identifica-tion of the kinematic groups of the mechanism and the replacement of the higher kinematic pairs by links and by lower kinematic pairs.

Keywords: double gear harmonic transmission, structural analysis, link, kinematic pair

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Force Analysis of a Double Gear Harmonic Drive
Sava Ianici

The paper presents an original method for determining by experimental means the tangential forces distribution in the gearing’s zones from the portant elements of the double gear harmonic drive, as well the scheme of the used testing stand. Taking into consideration the results of the theoretical and experimental tests it may be asserted that they concord almost entirely, the deviation being under 6%.

Keywords: double gear harmonic drive, tangential force, experimental analysis, testing stand

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Forming Tendency Distribution of Oxide Inclusions in Kaplan Blade Castings
Cinca Ionel Lupinca, Constantin Marta, Relu Costel Ciubotariu, Rodica Radulea, Cornelia Ecaterina Cornean

The results of theoretical and practical studies realized on Kaplan rotor blades, cast from high steels alloyed with chromium and nickel represent the objective of this paper. The data presented refer to the distribution of alloy elements in the entire volume of the casting, resulted from the chemical composition analysis, determined on specimens taken from certain areas of the casting; the forming process and the distribution of oxide inclusions during the mould filling process and during the solidification process. In order to obtain results we have applied the AnyCasting simulation software. Microstructures of specimens from four different areas of the casting are also presented in this paper.

Keywords: Kaplan blade, simulation, martensite

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Considerations about how the Numerical Methods are Choose in Purpose to Calculate the Stress – Deformations from Rolling Bearings
Tiberiu Manescu jr.

The paper present the simulations made with finite element method for a simplified model of rolling bearing balls. The simulations were made with Ansys software. The simplified model of the bearing was made from a ball and two parallel planes.

Keywords: rolling bearing, finite element, Ansys, contact, stress

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Researches on Wear Evolution of Xylan 1052 Two-Layer Coating under Hard Working Loads or Different Rotational Speeds
Ion-Cornel Mituletu, Ion Vela, Gilbert-Rainer Gillich, Marius Tufoi

Assuming that vibration and noise amplitude depend on coating thickness, here were performed important tests about wear of the Xylan 1052 coating. Applying variable contact stress by different load pressures on a disk coated, and keeping the rotational speed constant, a wear evolutions diagram has resulted. Also, a diagram with the wear evolutions of Xylan 1052 coating has been achieved by using the same load pressure and varying the rotational speed. This information offers significant knowledge about Xylan 1052-film wearing, reflecting an appreciation of the running-in period and the coating thickness. Further on, the proper working time is accomplished, as well as the minimum coating thickness whereas the covering becomes irrelevant to use.

Keywords: wear evolution, Xylan 1052 coating, contact stress, rotational speed, coated disk

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Lubrication Influence on Wear Evolution of Xylan 1052 Coated Disk Tested at Various Rotational Speed and High Contact Stress
Ion-Cornel Mituletu, Ion Vela, Zoltan Korka, Marius Tufoi

This paper relates the lubrication influence on the Xylan 1052 coating applied as the surface layer of a testing disk. By pressing a coated and uncoated bearing ball against the surface of coated disk having different rotational speeds, wear evolution diagrams have been achieved. Tests were performed in three specific conditions, when the disk coated surface is: dry, under poor or continuous lubrication. These conditions allow understanding the influence of poor or continuous lubrication on the behavior of coated disk surface at the contact stress. Such conditions could practically occur due to some problems appearing in industrial environment.

Keywords: wear evolution, dry test, poor lubrication, continuous lubrication, Xylan 1052 coated disk

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Applications of the Rapid Prototyping Technology to Manufacture the Pelton Runners
Dorian Nedelcu, Raoul Avasiloaie, Danut Florea, Aleksandar Rajic

The paper presents an application of the Rapid Prototyping technology using Objet Desktop 3D Printer to manufacture two Pelton runners that are destined for experimental measurements on a Pelton microturbine. The runners are different by bucket’s number and the bucket’s geometry of the second runner is similar with those of the first runner, but scaled in all directions with the bucket’s numbers ratio.

Keywords: Rapid Prototyping, Pelton, runner

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The Reverse Engineering of a Spring Support using the Noomeo Optinum 3D Scanner and the Rapidform XOR3 Software
Dorian Nedelcu, Aleksandar Rajic, Danut Florea, Raoul Avasiloaie

The paper presents an application of the Reverse Engineering technology using a Noomeo Optinum 3D scanner to read the complex shape of the spring support and generate the geometry in a computer file that can be processed by Computer Aided Design software. Rapidform XOR software was used to convert the scanned data into a solid model.

Keywords: Reverse Engineering, 3D Scanner, spring, Rapidform XOR3

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Big Data in High Performance Scientific Computing
Florica Novacescu

The main concern of this study is to find the bottlenecks that are caused by the deluge of data, in the supercomputing community. To be more precise, the research targets the big data community, and is concentrated around identifying the new challenges posed by the huge amounts of data resulted from the numerical simulations using supercomputers..

Keywords:supercomputing, big data, high performance scientific computing, big data challenges

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The Block Diagram for the Synchronous Motors used for the Compensation of the Reactive Power
Iulius Petrica, Adrian Valentin Petrica

The optimal control system for the compensation of the reactive power in an energetic consumer assembly is presented, containing one or more synchronous motors, connected to the same power bars in parallel, including asynchronous motors and static converters. The compensation of the reactive power absorbed from the system by the consumers is possible, using a optimal control system that controls the reactive power provided on the bars by the synchronous motors on condition that the power losses in the created whole are zero. A limited functional block diagram of the synchronous motor, which is the controlled object completed with the control circuits of the exciting tension and current is obtained having as set value the sum of all reactive currents of the consumers from the power assembly. The optimization is obtained using the module criterion of Kessler.

Keywords: asynchronous motors, reactive power, block diagram, Kessler

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Computer Simulation of Water Flowing inside Turbine HYE 10a, a Modern Method for Checking of the Structural Improvements
Florin Pomoja

This paper presents theoretical results of flow simulations, performed on cross-flow type turbine of 8.25 kW, and also the results obtained on the improved turbine, with modified shapes for the rotor, case, and guiding palette.

Keywords: Computational Fluid Dynamics, cross-flow turbine, 8.25 kW

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Anul XX (2013), Nr. 2

COVER

TABLE OF CONTENTS

ARTICLES

A Continuous Approach of the Contact Dynamics
Petre P.Teodorescu, Veturia Chiroiu

Ther paper is devoted to the analysis of a sonic composite under dynamic contact with friction loading, by using LISA (local interaction simulation approach). LISA is an an efficient tool for the numerical simulation of the acoustic wave propagation in heterogeneous material specimens, in particular those with sharp boundaries between different materials, like in sonic composites. Boundary conditions are introduced to contain contact interfaces with frictional slips.

Keywords: sonic composite, auxetic foams, contact, friction, LISA

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On the Modeling of Contact Interfaces with Frictional Slips
Ligia Munteanu, Cornel Brisan

The paper analyses the contact interfaces between the scatterers and the matrix into the sonic composites, in the presence of the frictional slips. The sonic composite is a sonic liner designed in order to provide suppression of unwanted noise for jet engines, with emphases on the nacelle of turbofan engines for commercial aircraft.

Keywords: sonic composite, contact interface, friction, slip

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An Experimental Study of the Cutting Forces in Metal Turning
Zoltan Iosif Korka, Calin-Octavian Miclosina, Vasile Cojocaru

Cutting forces are classified among the most important technological parameters in machining process. Cutting forces are the background for the evaluation of the necessary machining power, as well as for dimensioning of the tools. Cutting forces are also having a major influence on the deformation of the work piece machined, its dimensional accuracy, and machining system stability.

Keywords: Metal cutting, cutting forces, cutting parameters

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Some Aspects on Technological Design of a Cam Type Workpiece Using CATIA Software
Calin-Octavian Miclosina, Zoltan Iosif Korka, Vasile Cojocaru, Catalin Lorinti

The paper presents the geometrical models of cam and of semi-finished piece, obtained with CATIA software. Two cam technological routes are shown and the optimal route is chosen. From the technological route, rough milling operation is simulated with CATIA software. By using different milling parameters, various machining time values are obtained.

Keywords: technological design, rough milling, CATIA

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Considerations Regarding the Stresses and the Deformations of the Butterfly Valve Body
Florin Peris-Bendu, Adelina Bostan, Viorel Câmpian, Dorian Nedelcu

In the present paper it is analyzed the “von Mises” equivalent stress distribution, respectively strains, which appear in the body of a butterfly valve with nominal diameter (DN) of 2800 mm and operates at a nominal pressure (PN) 19 bar. The paper examines the body of a butterfly valve using finite element method and the followings data is considered to be known: boundary conditions for which the analysis is made in both positions, the valve disk in the closed position and the open position, mechanical characteristics and resistance of the materials for valve body components and loads to which it is subject. The result of the analysis obtained allow optimization of the valve body size by highlighting the oversized areas respectively areas where efforts are maximized.

Keywords: von Mises equivalent stress, strains, body valve, butterfly valve, finite element method

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Influence of the Mesh Parameters on Stresses and Strains in FEM Analysis of a Gear Housing
Vasile Cojocaru, Zoltan Iosif Korka, Calin-Octavian Miclosina

The influence of the mesh parameters on the results of FEM simulations depends on the type of the study and the geometry of the system submitted to analyze. In this paper a gear housing was submitted to static analysis. Six studies with distinct values for the maximum dimensions of mesh elements were applied. The results show significant differences for the values of maximum stresses and relatively small differences for the maximum displacements and strains.

Keywords: FEM simulation, mesh, stresses, strains, gear housing

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Experimental Determination of Chassis Tensions Freight Wagons with High Walls Tensometriei Resistive Method
Cornel Iacob-Mare, Tiberiu Stefan Manescu

The paper aims at forwarding an experimental analysis, through the method of resistive tensometry, of the strains occurring in the body of a high-walled freight wagon with handler’s platform.

Keywords: wagon body, resistive tensometry, experimental analysis

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Comparison Criteria and Performance Levels for Soundproofing Panels Made in Different Constructive Variants
Ana Gheorghe

This paper presents an analysis of the performance lavels and comparison criteria for panels made from different soundproofing materials, in different constructive variants. Setting the performance level, on the basis of normative and regulatory documents, for soundproofing materials contained inside of noise reduction devices, is determined so that it can be defined, tested and established feasible technical solutions for sound absorbing protection, through a dissemination of obtained results as well for ensuring requirements for implementing the technology transfer for manufacturing.

Keywords: soundproofing materials, noise reduction devices, performance levels

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An Effective Strategy for Enforcing Ethics Compliance amongst Engineering Industries in the Developing World
Fatai Sado, Faris Waleed

Both governments and professional engineering societies in the developing nations have made several codes of ethics for their engineering industries. But there are little indications that these codes are fully complied with. The consequence of poor compliance has been a tremendous negative effect on humans and the environment. The need to enforce the application of these ethics is therefore necessary. A two way solution is suggested. An internal approach that will require the industries to set up and supervise an ethics compliance program induced by way of government legislation; and an external approach that will require the government to setup an active task force supported with an active involvement of professional societies to setup their own watchdog and ethics compliance scheme for the industries.

Keywords: ethics, engineering industries, compliance

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Insertion Loss Analysis of the Acoustic Panels with Composite Construction
Vasile Ovidiu

In order to reduce noise pollution, under European legislation in our country need to align, a special attention has the tests carried out on acoustic panels. The most eloquent attempts, defining traffic noise attenuation are tests that can determine the insertion loss of an acoustic screen. In this paper, it briefly shows the method of determining the insertion loss in octave bands and some real results in the case of acoustic panel in a composite construction.

Keywords: acoustic panels, insertion loss, composite

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New Products and Technologies, Based on Calculations Developed Areas
Gheorghe Vertan, Teodor Eugen Man, Eugen Constantin Isbasoiu, Adalbert Kovacs

Following statistics, currently prosperous and have high GDP / capita, only countries that have and fructify intensively large natural resources and/or produce and export products massive based on patented inventions accordingly. Without great natural wealth and the lowest GDP / capita in the EU, Romania will prosper only with such products. Starting from the top experience in the country, some patented, can develop new and competitive technologies and patentable and exportable products, based on exact calculations of developed areas, such as that double shells welded assemblies and plating of ships' propellers and blade pump and hydraulic turbines.

Keywords: invention, developed area, welded assembly, plated blades

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Considerations on the Approach of Rolling Contact Fatigue Assuming Multiaxial States of Stress
Tiberiu Manescu Jr, Gilbert-Rainer Gillich, Ion Dumitru, Lorand Kun

Rolling contact fatigue appears in many mechanical elements, in the presence of variable local loadings. During the last years an increasing attention has been awarded macroscopic and mesoscopic analysis of repetitive rolling contact, taking into consideration local triaxial states of stress. Given the above, the authors analyze a fatigue criterion based on the stress state invariants, which is validated using original results as well as existing data from the literature. The criterion is applied to the case of linear contact with friction, which has analytical solutions for the elastic state of stress on the rolling surface and in the adjacent zone. A durability calculation method is presented for the case of rolling contact, based on the ratio between the maximum and experimentally obtained critical (limit) value of a damage parameter.

Keywords: rolling contact, bearing, multiaxial fatigue, stress invariants

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Naval Power System Dynamics with Proportional Type Regulators
Eugen-Marius Afronie, Tiberiu Stefan Manescu

The purpose of this paper is to verify through finite element analysis, behaviour of road impact railing. The vehicle used is a hard type, in our case a bus. By definition, the railing is a wall or a railing of little height witch serves to delimit the edge of a road, a bridge, aimed at stopping vehicles and restoration mainly on carriageway, pedestrians and conveyance of other road users.

Keywords: safety, railing, protection, steel, deformation

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Climate Changes and their Influence on the Design of Hydraulic Structures from Romania
Florin Trofin

During the last decades, the human being influenced environmentally the Earth, causing global environmental changes of such a size that have become global phenomena.These changes include the climate, ozone layer depletion, biogeochemical cycles, hydrological cycle, and water resources, raising the ocean levels or thermohaline circulation. The hydrological cycle and water resources changes have significant effects on the design of hydraulic structures, provided they are exploited in the presence or absence of major climatic factors, such as water, air, or soil.

Keywords: hydrological cycle, water resources, theoretical probability curve

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Examination of Cyclic Plasticity Models Under Uniaxial Loading by Finite Elements Method
Hossein Jarrahzadeh, Shahram Shahrooi

One of the main characteristics of the existing plasticity theories is the lack of a theory and specific equations for them. There are various methods with different results for solution of a plasticity problem. In this paper, two cyclic plasticity models of non-linear (Chaboche) and multilinear (Bessel) kinematic hardening are evaluated based on experimental data for 1% Cr-Mo-V steel alloy. Uniaxial loading on the specimen in seven steps is done by control stress method and using Ansys software. In each step, strains of elastic, plastic and then total have been calculated. The values obtained from simulation compared to experimental results is shown a good agreement on the both results, particularly in non-linear solution.

Keywords: Plasticity Models, Cyclic Kinematics, Plastic Strain, Finite Element Method

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Potential of Biogas Power Plant Produced by Anaerobic Digestion of Biodegradable Materials
Nur Shuhada Ghazali, Md Azree Othuman Mydin, Nik Fuaad Nik Abllah

Biogas typically refers to a gas produced by the breakdown of organic matter in the absence of oxygen. It is a renewable energy source, like solar and wind energy. Furthermore, biogas can be produced from regionally available raw materials and recycled waste and is environmentally friendly and CO2 neutral. Biogas is produced by the anaerobic digestion or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops. Biogas comprises primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes. The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel. Biogas can be compressed, much like natural gas, and used to power motor vehicles. Biogas is a renewable fuel so it qualifies for renewable energy subsidies in some parts of the world. Biogas can also be cleaned and upgraded to natural gas standards when it becomes bio methane. This paper will discuss the potential of biogas in order to provide a clean, easily controlled source of renewable energy from organic waste materials for a small labour input, replacing firewood or fossil fuels which are becoming more expensive as supply falls behind demand.

Keywords: biogas, anaerobic digestion, waste management, anaerobic digestion, sewage, municipal waste

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Effect of Nanofluids on Heat Pipe Thermal Performance: A Review of the Recent Literature
Navid Bozorgan, Nariman Bozorgan

The addition of the nanoparticles to the base fluid is one of the significant issues to enhance the heat transfer of heat pipes. The purpose of this review is to summarize the research done on heat pipes using nanofluids as working fluids in recent years (2012 to 2013). The peer reviewed papers published in citation index journals have been selected for review in this paper. This review article provides additional information for the design of heat pipes with optimum conditions regarding the heat transfer characteristics of nanofluids in heat pipes. Moreover, this paper identifies several important issues that should be considered further in future works.

Keywords: Heat pipes, Nanofluids, Thermal resistance, Heat transfer

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Railways Factory in Resita
Cornel Iacob-Mare

This paper proposes an exemption Analysis railway factory in Resita impressed having experience and also provide some technical characteristics of freight wagons representative technology, used to transport products made in factories in ResiNa.

Keywords: railways factory, rail technology, transport, steel industries

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Evaluation of the Moldboard Structure Resistance of the Grader Equipment
Carmen Debeleac

In this paper, the author presents a method for evaluation of the moldboard structure resistance of the motor-graders. Usual grader model was chosen to be analyzed by the FEM. Horizontal force of the blade was estimated using the classical soil mechanics theories for cutting soil proposed by McKyes. The simulation results can be useful for structural performance evaluation of these machine used in construction and agricultural fields.

Keywords: grader, moldboard, analysis, FEM

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Opnet Analyze for FTP and Video Networktraffic using IP over MPLS Protocol
Ioan Fitigau, Gavril Toderean

MPLS provide an efficient forwarding mechanism, scalability with an important role in switching and routing of packets through the next step in networking evolution, in order to meet the most complex service demands for these users. In this paper we analyze the performance impact of FTP and Video traffic for mpls network and conventional IP network, using Opnet Modeller for simulations. The simulation results are analyzed, showing that MPLS based solution provide a better performance for the traffic over the network.

Keywords: MPLS, IP, Opnet, FTP, Video

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The Analysis Regarding the Building of a Hydraulic Power Plant on the Black Sea Shore
Gheorghe Samoilescu, Sergiu Nicolae, Florentiu Deliu, Raluca Apostol – Mates

The present paper represents the result of a research project regarding the construction of a wave driven hydraulic plant that is going to be installed on the Black Sea shore in the area of the city of Constanta. Several phases were analyzed: numerical simulations for the micro plant – wave energy theory; finite element simulation – results and conclusions; generating the blueprint for the construction of the plant.

Keywords: hydro-pneumatic installation, micro-power station, floor coverings, profiles, resistance module

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Dependence of the maximum power and wind speed
Florentiu Deliu, Gheorghe Samoilescu, Paul Burlacu

The issue paper is to present renewable energy sources insisting mainly on wind energy. This source is analyzed in the context of Romania in particular and the EU in general. A turbine with horizontal axis is usually coupled with vessel power systems. Wind energy knows an increased growth rate. At the end of the paper are presented possible structure of coupled a wind to power systems.

Keywords: renewable energy, wind energy, wind turbine, vessel energy system

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The Possibility of Functioning at Maximum Power for Solar Photovoltaic - Electric Battery Systems
Cristian P. Chioncel, Marius Babescu, Petru Chioncel

The paper presents the functioning of a solar photovoltaic module (PVM) that debits direct to on electric battery (EB). By a good adapting of PVM to EB, so that the no load voltage of the two components (PVM and EB) are well suited, during a day the energy value can be reached near to the maximum possible value, when the PVM functions in the maximum power point (MPP). The proposed solution is much more economic than the classical: PVM + DC – DC + EB because the direct current - direct current power converter, is not necessary (DC - DC).

Keywords: solar photovoltaic module, maximum power point

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The Possibility of Functioning at Maximum Power for Solar Photovoltaic - Electric Battery Systems
Cristian P. Chioncel, Marius Babescu, Petru Chioncel

The paper presents the functioning of a solar photovoltaic module (PVM) that debits direct to on electric battery (EB). By a good adapting of PVM to EB, so that the no load voltage of the two components (PVM and EB) are well suited, during a day the energy value can be reached near to the maximum possible value, when the PVM functions in the maximum power point (MPP). The proposed solution is much more economic than the classical: PVM + DC – DC + EB because the direct current - direct current power converter, is not necessary (DC - DC).

Keywords: solar photovoltaic module, maximum power point

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Solution for Improve the Efficiency of Solar Photovoltaic Installation
Petru Chioncel, Cristian Paul Chioncel, Nicoleta Gillich

This paper present a solution for improving efficiency of solar photovoltaic installation, realized with fixed solar photovoltaic modules, placed in solar parks or individual installations. The proposed solution to increase the radiation on the solar photovoltaic panels is to use some thin plates covered with a reflective blanket, mounted in front of the solar photovoltaic modules, with the possibility of their adjustment.

Keywords: solar radiation, photovoltaic module, improving efficiency

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Modulated Field Synchronous Generator for Wind Turbines
Petru Chioncel, Cristian Paul Chioncel

This paper presents a modern electromechanical conversion system solution as the modulated field synchronous generator, offering on the one hand, an output voltage with constant frequency in terms of speed variation of the wind turbine and on the other hand an advantage power / weight ratio due to the high frequency for which the magnetic circuit of the electric machine is sized. The mathematical model of the modulated field synchronous generator is implemented in MatLAB modeling language, highlighting the command structure on the transistors bases of the inverter transistors, through which the functioning of the electric machine can be studied, especially in terms of the frequency of the delivered voltage.

Keywords: modulated field synchronous generator, inverter, mathematic model

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Influence of Urban Traffic Driving Conditions and Vehicle Cubic Capacity on CO and VOC Emissions
Arina Negoitescu, Adriana Tokar

The reports regarding the global warming warn on the urgent need to reduce pollutant emissions and in particular greenhouse emissions. The performed analysis shows that cars equipped with engines operating on petrol, lead to a lower level of pollution, from the point of view of CO (carbon monoxide) and VOCs (volatile organic compounds) emissions at speeds above 50km/ h. Since driving in urban traffic mode involves driving with a speed up to 50km/h, it was comparatively analyzed the automobile engines operation with different cubic capacities. In conclusion, in terms of the analyzed emissions in accordance with the emission standards requirements for urban driving situations, it results that the accepted values of these emissions are recorded for automobile engines of low cubic capacities (under 1.4 l).

Keywords: urban traffic, pollutant emissions, passenger car, cubic capacity

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The Influence of the Water Supply Indoor Installations Pipes Wear and Clogging on Water Consumption and Hygiene and Sanitary Comfort Level
Adriana Tokar, Arina Negoitescu

To ensure and increase the hygiene and sanitary comfort degree in buildings older than 25 years, rehabilitation and modernization of water supply indoor installations is required. The rate at which these capital repairs were made to the common facilities is very low, which explains the increasing number of commercial buildings that claims flooded basements due to rusty, clogged or broken pipes. In this regard, the paper analyzes the situation of an apartment building, located in Timisoara, which is 48 years old and to which were made only partial rehabilitation works. The solutions resulted from the performed analysis lead to the necessity of performing the rehabilitation and modernization works by replacing the installation distribution and columns that shows a high wear and clogging degree.

Keywords: hygiene and sanitary comfort, flow, pressure, clogging, rehabilitation

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Some Theoretical Observations Concerning the Reverberation Time for the Case of a Harmonic Emitting Source
Dusan Popov, Nicolina Pop, Cornel Hatiegan

In the paper, the reverberation phenomenon produced by the harmonic emission of a sound source is theoretically examined, taking into consideration the absorption of the sound in the air. We obtain a formula which contains, as particular cases, the similar formulae presented in the literature.

Keywords: reverberation time; absorption of sound; acoustic energy

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The Evaluation of the Functional Performances for Microhydroaggregates Endowed with Asynchronous Generators by Vibrations Measurements
Valentin Nedelea, Ladislau Augustinov

By this study we aim to establish some methodologies for the estimation of performances for microhydroaggregates by limiting the power according to the vibrations level.

Keywords: asynchronous generator, vibration, turbine, active power, reactive power

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The Synchronous Generators Rated Speed’s Influence on Electromagnetic Stresses and on Costs
Elisabeta Spunei, Laurentiu Padeanu, Florina Piroi, ion Piroi, Gheorghe Liuba

During the design of synchronous generators is very important to establish the values of their electromagnetic stresses. The specific literature recommends that these stress values are to be chosen from the curves obtained during experimental design, where the independent values are the polar pitch and the number of pole pairs. The authors of this work propose a method of finding the dependency between the electromagnetic stress and the synchronous generator rated speed to rapidly estimate the stresses in a given interval of rated speed values.

Keywords: synchronous generator, rated speed, electromagnetic stresses, optimal designing, total cost

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Research on the Command of a Single-Phase Frequency Converter at High Frequencies
Ioan Ruja, Constantin Marta, Florin Breaban

The present paper forwards several results obtained during the study of the induction heating installations of metallic materials at high frequencies [1]. It details aspects related to the command of a monophase (half-bridge) inverter with PWM signals (Pulse-With-Modulation). The command of the MOS transistors is done with frequencies ranging between [0¸400] KHz and modulation factor variable within the [0-1] range. The possibility to modify the command frequency of the inverter, as well as the possibility to modify the PWM signal modulation factor allows the user to establish various resonance frequencies for the LC (parallel) circuit which, together with the metallic sample, constitutes the inverter charge.

Keywords: heating, melting metallic, signal, induction, resonance

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Development and Evaluation of a 2KVA Inverter
Ajayi Adedayo, Olotu Yahaya, D.K Jerome

A 2KV inverter was designed, developed and tested for household applications. It consists of a heavy duty (24 V, 80 AH), oscillator unit, PWM (Pulse-width modulation) controller unit, driver unit, amplifier unit, center-tap step up transformer and battery charger unit. The battery powered the circuitry and the oscillator section generates the drive signal that is amplified and set up the transformer to produce 240 V supply at the secondary winding connected to the output socket of inverter. The feedback control circuit uses discrete components such as: full wave rectifier, pulse width modulator (IC), diodes and other components to sense the output voltage (or load current). When the feedback senses that the load on the inverter output has increased, the inverter control circuitry acts by increasing the width of the switching pulse in the oscillator section which turn on the MOSFETS. MOSFETS turns on for longer time each cycle, automatically correcting the R.M.S value of the output to compensate for any drop in peak-peak output voltage as well as continuous charging of battery, consequently, maintaining a steady output voltage level in inverter irrespective of the load characteristics. The outputs of the tests carried on the unit shows that that instrument performs satisfactory well.

Keywords: Inverter, transformer, voltage, control circuit, current, output, MOSFETS, PWM

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Development and Performance Evaluation of a Ceramic Filter for Point-of-Use Water Purification
Bukola Olalekan Bolaji, Olugbenga Oluseyi Akande

In this work, a ceramic filter for point-of-use water purification was designed, fabricated and tested to evaluate its performance in filtering water to the World Health Organisation (WHO) standards. The results of pH of water samples obtained after filtration ranged from 7.68 to 8.11. The range of values obtained after filtration for turbidity, hardness, conductivity, total dissolved solid (TDS) and total suspended solid (TSS) from water samples were 0.07 to 0.55 NTU, 6.0 to 34 mg/L, (1.5 to 3.3) x 10-3S/m, 4 to 25 mg/L and 0.04 to 0.11 mg/L, respectively, while the filter average removal efficiencies of these parameters were 93.1, 85.1, 91.6, 92.3 and 91.4%, respectively. Comparison of the results with the WHO standards for drinking water showed that the ceramic water filter can provide potable drinking water of required standards.

Keywords: ceramic, drinking water, filter, performance, standards

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Anul XX (2013), Nr. 3

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TABLE OF CONTENTS

ARTICLES

Theoretical Assessments on Dynamics of Helical Flexible Coupling within Vibratory Equipments
Silviu Nastac, Cristian Simionescu

This study deals with vibratory equipments dynamic behaviour and especially reveals some critical aspects regarding the flexible coupling within and those influences on entire system evolution. Changing of dynamic characteristics, additional dynamic loadings and variances reducing of vibration parameters frame the main hypothesis of the research. This paper briefly presents a few theoretical assessments in terms of linear and nonlinear approaches of driving chain elements. Realistic expanded, also computational simplified models have been provided. Simulated behaviors denote that many of the reported observation regarding the serviceable dynamic distortions are correctly, and impose a set of additional instrumental tests in order to obtain a good accuracy for mathematical models.

Keywords: vibratory equipment, computational dynamics, helical flexible coupling, functional optimization> full text