Table of content

Journal of Engineering

مجلة الهندسة

ISSN: 17264073
Publisher: Baghdad University
Faculty: Engineering
Language: Arabic and English

This journal is Open Access

About

The Journal Engineering was issued in 1986. It was Stopped from 1990 – 1997 because of the economic blockade. It restarted publication after the fourth scientific engineering conference for it published the papers that were accepted in the conference.
It is a scientific engineering journal refereed by specialized and qualified professors in most of the engineering fields and those Specialists in the issued by the college of Engineering university of Baghdad .It was serenely publibued , but from 2011 it has issued of monthly for the numerous papers submitted to the journal to publish their papers in this scientific journal in addition to some of the Arabs professors because the journal is considered one of the valued journals in the Arabic homelan .
Many professions were the head editor of the journal from its first issue. The first one was prof.dr. Laith Ismail Namiq then prof.dr. Mohammed A.Alawis ,prof.dr.Ali A Al – kilidar prof.dr. Abdul-Ilah Younis and currently Prof.dr.Qais S. Ismail.

Loading...
Contact info

Jadriyah, Baghdad
Iraq
Mobile:
Email: joengbag@uobaghdad.edu.iq

Table of content: 2010 volume:16 issue:3

Article
Damaging Effect Of Moving Tank Loads On Flexible Pavement
التأثير التخريبي لأحمال ألدبابات المتحركة على التبليط ألإسفلتي

Loading...
Loading...
Abstract

Presented in this paper is a new study of the damaging effect of the tank loads on flexible pavements. The equivalent load was developed on the basis of mechanistic - empirical approach. It was found that the damaging effect of the studied tank loads is 0.898 to 2.356 times the damaging effect of the standard 18 kips (80 kN) axle load. It was found that the damaging effect of tank braking forces is 2.375 times the damaging effect of tank weight only in terms of tensile stain (fatigue cracking). It was found that the damaging effect of tank turning maneuver is 1.216 times the damaging effect of tank weight only in terms of tensile stain (fatigue cracking). These loads have also severe damaging effects on the functional serviceability of the surface of asphalt layer.


Article
Investigation On The Use Of Micropiles For Substitution Of Defected Piles By The Finite Element Method
تحري عن استعمال الركائز المصغرة كبديل عن الركائز المتضررة بطريقة العناصر المحددة

Loading...
Loading...
Abstract

Micropiles are small diameter, cast in – place or grouted piles with steel pipes of (50 to 300 mm) diameters and driven by boring machine. Despite their small wall thickness, high bearing capacity of micropiles provides both axial and pullout resistance. This paper is directed to study the behavior of micropiles under static and dynamic loading conditions using the finite element method. The program OpenSees is used in the analysis, it is open – source program, provides information about the software architecture, access to the source code, and the development process. The program is based on the basic commands, which are written in Tcl (pronounced, "tickle"; tool command language). A model for groups of laterally loaded pipe piles in sand was adopted to study the effect of defects on their lateral performance. The geometric arrangement consisted of group series of 2, 4 and 6 equally spaced piles. Eight node brick elements are used to model the pile and the surrounding soil. It was concluded that the deflection of laterally loaded piles decreases when inserting steel micropiles beside the defect pile at two opposite directions. The increase in the group deflection is greater when the defected pile is modeled in the front row.

Keywords


Article
Finite Element Analysis Of A Friction Pendulum Bearing Base Isolation System For Earthquake Loads
التحليل بالعناصر المحددة لنظام العزل بقاعدة بندول الاحتكاك للأحمال الزلزالية

Loading...
Loading...
Abstract

Base isolation systems have become a significant element of a structural system to enhance reliability during an earthquake. One type of base isolation system is Friction Pendulum Bearing in which the superstructure is isolated from the foundation using specially designed concave surface and bearing to allow sway under its own natural period during the seismic events. This study presents the finite element analysis of Friction Pendulum System (FPS) of a multi-story building and without base isolation, subjected to two real different earthquakes (El Centro & Loma Prieta) by use engineering program (ETABS Nonlinear version 9.5). Comparing with the available experimental data, the application of the current model gives close prediction. It has been shown that as a result of isolation, base shear acting are reduced considerably. A parametric study dealing with the coefficient of friction µ (0.08,0.15 and 0.25) and radius of concave surface R (40 in, 80 in and 400 in) to study the base shear and the displacement of Friction Pendulum System. Overall the base isolated system showed a significant improvement in dynamic response of the model structure by reducing the base shear and increasing the damping of the system.


Article
Seismic Design Of Single Span Steel Girder Bridges And Bridges In Seismic Performance Category A

Authors: Esraa Mubder Edaan --- Abdul Muttalib I. Said
Pages: 5337-5351
Loading...
Loading...
Abstract

This paper studies the validity and accuracy of the seismic design force recommended by AASHTO for single span bridges. A parametric study for single steel girder bridges is presented, included the effect of span length and elastomeric bearing and lateral bracing (cross-frame) stiffness. The results of simplified AASHTO method are compared with response spectrum and time history analysis. Also studying the seismic design reqiurements for continuous steel girder bridges in seismic performance category (A), included the effect of span length, seismic zone, effect of elastomeric bearing and cross-frame stiffness and bridge skew on their seismic responses. It is concluded that the AASHTO simplified analysis method for single span bridges underestimates the seismically induced forces at supports and the proposed seismic design force of (2.5 multiplied by acceleration coefficient multiplied by tributary weight w(x)) has been recommended for single span bridges for seismic zone 3 and 4 and for soil type II. Also it is observed that the seismic design force for two span continuous bridges in performance category A is safe and conservative method to predict the shear forces transferred by connection elements to the substructures.


Article
Effect Of Mineral Filler Type And Content On Properties Of Asphalt Concrete Mixes

Authors: Noor M. Asmael
Pages: 5352 -5362
Loading...
Loading...
Abstract

Some of the newly constructed highway pavements in Iraq have shown premature failures with consequential negative impacts on both roadway safety and economy. Major types of these failures are permanent deformation (rutting) and cracking. Fillers were suspected to be a major contributor to these failures. The objective of this study is to evaluate the influence of new different fillers extracted from different local sources on the performance of asphalt mixtures. The effect of filler type and content on the failures potential of asphalt concrete as well as other mixes properties was investigated. A detailed laboratory study is carried out by preparing asphalt mixtures specimens using aggregate from Al-Taji quarry, (40-50) grade asphalt from dourah refinery and three different types of fillers (Portland cement, Silica fume, and Fly ash) were tested in the laboratory. Marshal Mix design was made using all types of fillers and different ratios to evaluate the performance of different types and filler quantities in the asphalt mixture. The mechanical properties of mixes were studied using indirect tensile strength, creep and marshal tests. Three different tests temperature (15,30,45C°) were employed in the indirect tensile test to investigate the susceptibility of these mixes to change in temperature. Results of this study indicate that replacement of Portland cement by 9.8% of silica fume aggravates resistance of the mixes to rutting and cracking. Furthermore, coal fly ash cannot be used as mineral filler in hot mix asphalt paving applications.


Article
Frequency Domain Equalization Techniques for Multicode DS-CDMA in Frequency Selective Rayleigh Fading Channel

Authors: Sameer Akram Dawood --- Maha George Zia
Pages: 5363-5376
Loading...
Loading...
Abstract

Orthogonal multicode direct sequence code division multiple access (DS-CDMA) has the flexibility in offering high data rate services. However, in a frequency-selective fading channel, the bit error rate (BER) performance is severely degraded since the orthogonality among spreading codes is partially lost. In this paper, frequency-domain equalization (FDE) and space antenna diversity combining are applied to orthogonal multicode DS-CDMA in order to restore the code orthogonality and improve the BER performance of the system. Two methods of FDE are considered, the first method based on fast Fourier transform (FFT), while the second method based on circulant matrices. Moreover, a channel interleaving method, called chip interleaving is used to improve the performance of multicode DS-CDMA system.


Article
Modeling And Simulation Of A Buck Converter Controlled A Sensorless DC Series Motor

Authors: Tagreed M. Ali --- Bassim M.H. Jassim
Pages: 5377-5391
Loading...
Loading...
Abstract

This paper presents modeling and simulation of a speed sensorless control for dc series motor driven by a buck converter through computation of the motor speed from converter output voltage and current. The system model considers the nonlinearity of the series motor magnetization characteristics including the variation of the field inductance with the motor current.


Article
Derivation Of The Lorentz-Einstein Transformation Via One Observer

Authors: Faiz T. Omara --- O. M. AL-Kazalchi
Pages: 5392-5397
Loading...
Loading...
Abstract

Lorentz-Einstein transformation derived by Einstein in his theory of special relativity. Physical laws and principles are invariant in all Galilean reference frames under this transformation. The transformation in every day use in a host of contexts as in free solution of the Dirac equation in the modern field of heavy ion in atomic physics. Most books on theoretical physics and special theory of relativity and all research papers have derived the Eorentz-Einstein transformation using various propositions and employing two observers each located in Galilean system with relative motion receding the same events in the space-time manifold. This paper derives Lorentz-Einstein transformation by proposing just one observer using local coordinates of two Galilean system with relative motion following the track of a spherical pulse of light, which to our knowledge is not found in the literature.


Article
Hydrodynamic Studies of Bed Expansion in Liquid Solid Fluidized Bed
دراسة هيدروديناميكية لتمدد الاعمدة المسالة المتكونة من الصلب والسائل

Authors: Sawsan A. M. Mohammed
Pages: 5398-5410
Loading...
Loading...
Abstract

Expanded bed behavior was modeled by using the Richardson-Zaki correlation between the superficial velocity of the feed stream and the void fraction of the bed at moderate Reynolds number. The terminal velocity expression was developed by introducing two empirical parameters, the effective diameter of the particles and an exponent for the term. The Richardson-Zaki exponent constant (n) was found to vary with the density ratio and diameter ratio . It was noted that when the density ratio is less than one, there is no dense phase at the bottom of the test section. However, for density ratio greater than unity, there exists accelerating or dense regime at the bottom of the test section.


Article
Removal Of Copper Ions From Waste Water By Adsorption With Modified And Unmodified Sunflower Stalks

Authors: Besma Ismael Hussein
Pages: 5411-5421
Loading...
Loading...
Abstract

Unmodified and modified sunflower stalks were examined for adsorption as a replacement of expensive activated carbon which has been recognized as a highly effective adsorbent for the removal of heavy metal-ion. Two modes of operation were used, batch mode and fixed bed mode. In batch experiment the effect of sunflower stalk doses (2,3,4,5 and 6g/L) with constant initial copper concentration of 100 mg/L and constant particle size less than1.18 mm was studied. Batch kinetics experiments showed that the adsorption rate of copper ion by sunflower stalks was rapid and reached equilibrium within 60 min. Adsorption models Freundlich, Langmuir and Freundlich-Langmuir were fitted to experimental data and the goodness of their fit for adsorption was compared. In the fixed bed isothermal adsorption column, the effect of particle size (1.18-2.36, 2.36-4.75 and 4.75-9.00) mm, influent flow rate (2,4and 6) L/hr, bed depth (25, 30 and 35) cm and initial metal concentration (100 and 150) mg/L was studied. In addition, the modification of sunflower stalks could enhance their natural capacity. Sunflower stalks were modified by activation with nitric acid. The results of this study show that sunflower stalk, both modified and unmodified, is an efficient adsorbent for the removal of copper from waste water. Percent removal of copper reaches 100% when particle size (2.36-4.75)mm ,bed depth 35 cm and influent flow rate 4 L/h.


Article
Removal of Kerosene from Waste Water Using Iraqi Bentonite

Authors: Ziad T. Abd Ali --- Abbas H. Sulaymon
Pages: 5422-5437
Loading...
Loading...
Abstract

The aim of the present research is to study the potentiality of Iraqi bentonite as adsorbent for removing of kerosene from wastewater. Also the capacity of bentonite for kerosene removal was compared to the activated carbon capacity. The sorption of kerosene onto bentonite and AC. were described by two well – known adsorption isotherm models namely Langmuir and Freundlich models. It was found that the Freundlich model can fit very well the equilibrium isotherm adsorption of kerosene onto bentonite and AC. Batch experiments were carried out to study the effect of adsorption of kerosene onto bentonite using various conditions such as initial concentrations of kerosene (100-500) mg/L, agitation speeds (125, 250, 500, 800) RPM, and weights of bentonite (0.05, 0.5,1.1) gm, particle sizes (0.5- 0.6) mm, and temperature 303 k. It was found that the best results for removing kerosene onto bentonite were obtained at Co=500 mg/L, RPM =800. Activated carbon was used as powder and granular of particle sizes ranged (1-1.18) mm and (0.5-0.6) mm. The results indicated that the activated carbon was more active than bentonite for removing of kerosene from wastewater.


Article
Simulation of Sulfur Dioxide Removal from a Gas Stream in a Fluidized-Bed Reactor

Authors: Waleed M. S, Kadhem --- Nibras M. Abdulrasol
Pages: 5438-5458
Loading...
Loading...
Abstract

The object of this work is to model and simulate a fluidized bed desulfurization reactor by coupling a reactor kinetic model with a fluidized bed model based on two –phase theory(bubbling-bed model) proposed by Kunni and Levenspiel(1968).This model is useful for analysis of a reaction involving gas and solid. It generates the conversion data with respect to reaction time of both reacting gas and solids in a continuous flow(for both gas and solids) in fluidized bed. The flue gas or stack gas from a combustor which normally contains sulfur dioxide mixed with excess air is used as the fluidizing gas with calcium oxide as the fluidized solids . Calcium oxide is quite capable of reacting with to effect its removal from the gas phase according to the exothermic reaction. The effects of the solid feed rate, SO2 concentration in the flue gas, bed height, bed diameter, particle size, fluidizing velocity and operating temperature on the extent of conversion of both gas and solid were investigated, for a fixed feed rate of flue gas and SO2concentration (50.000 cm3/sec ,3-5% by volume)at temperature range of (950-1000oC)and pressure 1 atm.

Keywords


Article
Prediction Of Natural Convection Heat Transfer In Complex Partitions Cavity

Authors: ISRAA Y. DAOUD --- SATTAR J. HABBEB
Pages: 5459-5480
Loading...
Loading...
Abstract

A numerical investigation has been carried out to examine the effects of insulated baffle mounted in complex cavity representing as an industrial building on flow pattern and heat transfer characteristics. The cavity is formed by adiabatic horizontal bottom, inclined upper walls and vertical isothermal walls. This problem is solved by using flow-energy equations in terms of stream-vorticity formulation in curvilinear coordinates. Two cases are considered; in the first (case 1) the insulated baffle position attached to the horizontal bottom wall of the cavity while in the second case (case 2) the insulated baffle position attached the upper inclined wall. A parametric study is carried out using following parameters: Rayleigh number from 103 to 106, Prandtl number for 0.7 and 10, baffle height (HB=0, 0.3H*, 0.4H*, and 0.5H*), baffle location for (LB=0.25L and 0.75L) with or without baffle in the cavity (total of 100 tests). For case 1 results show that, the flow strength generally increasing with increasing Ra values, increasing baffle height, and decreasing values of Pr, while in case 2 the same behavior of above could be show except the flow strength decreasing with increasing baffle height, also, increase Ra leads to increase the rate of heat transfer. The configuration of the cavity in case 2 leads to increase in heat transfer rate comparing with that in case 1.


Article
Dynamic Behavior Of Non - Return Valves Operating At Small Opening

Authors: Ali W. Abbas --- Hameed D. Lafta --- Ali A. M. Al-Asadi
Pages: 5481 -5502
Loading...
Loading...
Abstract

In the present work a general dynamic behavior of non return valves subjected to jet flow is presented. The differential equations of valve motion and discharge were developed in a non-dimensional from, in terms of suitable dimensionless variables and parameters of the valve system. The derived equations are coupled nonlinear differential equations. Thus, a computer program was developed using a package called (MatLab) to solve these equations. The study shows that there are three types of the valve responses depending on the overall hydrostatic pressure difference and it is found that the valve vibrating at a constant limit cycle, which is leading to the failure of the system. It is also shown that the limit cycle frequency decreases with increasing the stiffness parameter and inertia factor. Finally the study shows that the losses factor has negligible effect on valve vibration and discharge.


Article
Separation of oil from O/W emulsion by electroflotation technique

Authors: Ali Jassim Mohammed Al-Gurany --- Ahmed A. Mohammed
Pages: 5503 -5515
Loading...
Loading...
Abstract

Dilute emulsified oil in water (50-500 ppm) was removed by electrocoagulatin and electroflotation process. Effects of various parameters such as current density, initial pH, sodium chloride concentration, different electrodes material, gap, temperature, electrodes surface area, and treatment time on the removal efficiency were studied in batch and continuous mode.It was found that the higher removal efficiency (99%) achieved at pH of 7.5 for Al/Al electrodes while for iron electrodes at pH 8 in the batch mode. The removal efficiency increased and the treatment time decreased with increasing the current density and decreasing the gap distance between electrodes. The removal efficiency was (99%) at 10 min for Al/Al electrodes, (98.6%) at 12 min for Al/St.St. electrodes, and (97.4%) at 12 min for Fe/St.St. electrodes. The present results showed that the best temperature was 60ºC .The best concentration of sodium chloride was found to be (400 ppm) when the oil concentration was (500 ppm). Also it was found that a vertical Al/Al electrode was the best type with an electrical energy consuming (3.36 kWh/m3). In the continuous experiments, the removal efficiency enhanced with increasing flow rate. A multiple linear regression model was used in order to relate experimental data to a statistical model with a correlation coefficient of (0.909) and variance (0.827).


Article
Vertical Vibrations of Base Isolated Machine Foundations

Authors: Salim Y. Awad --- Thmir K. Mahmood
Pages: 5516-5535
Loading...
Loading...
Abstract

Vibration of base isolated machine foundations has been studied using the Scaled Boundary Finite Element Method (SBFEM) and the cone model method. The dynamic stiffness of soil supporting rigid massless foundation was determined. This stiffness is of complex value. The real part represents the reflected energy of the restoring and inertial forces while the imaginary part represents the energy dissipated within the endless extent of the soil as a geometric damping. The effect of geometric and material properties of soil upon the real and imaginary parts of the dynamic stiffness was determined and represented in terms of dimensionless charts for the frequency range of interest. Results have shown that increasing the embedment ratio has a significant effect on the dynamic stiffness, it increases the dynamic stiffness considerably. The effect of stiffness ratio(stiffness of isolator/ stiffness of soil) was demonstrated for isolated machine foundations. The use of soft isolators reduces the dynamic response of foundation and the soil reaction.


Article
Experimental Study On The Presence Of Open Cavity Effects On Internal Flow And Convection Heat Transfer Characteristics

Loading...
Loading...
Abstract

An experimental study is conducted to investigate the effect of open cavity on the pattern of fully developed internal flow and convection heat transfer. In this experimental work the velocity profile, temperature distribution, heat transfer coefficient and Nusselt number were determined at various Reynolds numbers (1.9*104 ≤ Re ≤ 2.7*104) for smooth surface as well as for flow over open cavity (with and without excitation). The results showed that the presence of the cavity led to change the downstream velocity profile and the dissimilarity of downstream skin friction coefficient between the upper and lower surfaces around (64 %) at distance to the length cavity (x/L= + 20.5). As a result the heat transfer coefficient and Nu increased downstream of the cavity especially at (x/L= + 20.5) around (30 %). The effect of cavity excitation with different sound levels (100,107.5 and 115) dB and frequencies (25,50 and 100) Hz was small compared with the cavity itself.

Keywords


Article
Damage Detection In Rotating Blade By Vibrational Analysis Using Finite Element Method

Authors: Shwan A. Z. --- Nabil H. H.
Pages: 5548-5568
Loading...
Loading...
Abstract

The development of monitoring systems for rotating blade has been driven by a desire to reduce the maintenance costs and human interaction to improve the safety, reliability and operational life, so it is urgent to monitor the integrity of a structural systems. In this study four different coordinate system has been used to describe the blade motion, then an element stiffness and mass matrices has been formulated by using Hamilton,s principle and finite element method, where each element has been described by seven degrees of freedom, so the method has been demonstrated analytically on a finite element model to estimate the modal parameters under rotating and non-rotating conditions in vacuum (to eliminate aerodynamic effect and damping coefficient) and to capture centrifugal effect, so the damage has been simulated by stiffness reduction of assumed elements and by crack form . These results was reasonable, so many parameters has been investigated such as, damage severity, damage location and the effect of rotation speed on these methods have been studied, as well as an assessment has been provided for these methods via statistic to suggest the effective method and this is the main objective, so The Residual Error Method was the best,compared with other methods. All formulations and computations has been coded in MATLAB version 7.


Article
Analysis of Concrete Flexural Members Reinforced with Fibre Polymer
تحليل الأعضاء الخرسانية المنحنية المسلحة بالألياف البوليميرية

Authors: Ahlam Ali Al-Asadi --- Nazar K. Oukaili
Pages: 5569-5587
Loading...
Loading...
Abstract

Analytical model is used in this paper to predict the load carrying capacity of structural concrete members under flexural and normal force which can be concentric or eccentric. The analysis is based on requirement of equilibrium and compatibility of strain in concrete and steel or FRP. The adopted model is based on the real stress - strain diagrams for materials. In accordance with this model, the member cross section is covered by a mesh with the smallest cells. After that, stress or strain is determined in each cell and the integral is substituted by the process of summation to define the elements of stiffness matrix. The force vectors equations have nonlinear behaviour. However, in this model, these nonlinear equations are changed to linear equations using the iteration methods with fixity of secant modulus of elasticity in each iteration cycle. In this paper, FORTRAN computer program language is used to compute the force and strains vectors. The comparison between the analytical results obtained from the used model and experimental data for other researchers is performed. The analytical model is giving a reasonable agreement between the theoretical and experimental results.


Article
Design Of A Sliding Mode Controller For A Tora System

Authors: Shibly Ahmed Hameed --- Waladin Khairi Sa'id
Pages: 5588-5605
Loading...
Loading...
Abstract

This paper presents the design of a sliding mode controller for an uncertain model of a TORA system (Translational Oscillations with a Rotational Actuator) as a two DOF underactuated mechanical system. The switching function is selected to make the TORA system an asymptotically stable mass-spring system with a nonlinear damping effect when the sliding mode controller constrains the state to the sliding manifold. This sliding mode controller is derived here according to a new formula consisting of continuous and discontinuous parts. The main obstacle in the controller design is the uncertainty in the switching function, which appears in the controller formula. The sliding controller is found effective in bringing the system state to the neighborhood of the equilibrium point in spite of the uncertainty in the switching function. In addition, the chattering problem is solved via the use of approximate signum function.


Article
Investigation And Modification OF Aerodynamic Characteristics OF Supersonic

Loading...
Loading...
Abstract

Increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft (F-16A) is presented. Aerodynamic characteristics, surface pressure distribution and maximum lift are are estimated for the baseline configuration for different Mach number and angles of attack in subsonic and supersonic potential flow, using a low order three-dimensional panel method supported with semi-empirical formulas of Datcom. Estimation of the total nose-up and nose-down pitching moments about the center of gravity of the completed aircraft in subsonic region depending on the flight conditions and aircraft performance limitations. A modern program was implemented by suggesting a two dimensional thrust vectoring technique (pitch vectoring up and down) controlled by the best design of advanced aerodynamic and control surface (foreplane or canard). Work results shows that the canard (as a control surface) with thrust vectoring produces enough nose-down moment and can support the stabilator at high maneuvers, while for an aerodynamic surface, a rate of (5-6%) increase was achieved in the aerodynamic efficiency (lift-to-drag ratio) of the baseline configuration in both subsonic and supersonic flight.

Keywords


Article
Flash Evaporation Enhancement By Electrolysis Of Saturated Water Flowing Upwards In Vertical Pipe

Authors: Radwan Muhammad Addaiy --- Akram. W. Izzat
Pages: 5620 -5632
Loading...
Loading...
Abstract

An experimental system was designed and built to produce the flash evaporation of upward water flow in a (1.8 m) vertical mounted glass test section pipe. The water loses the static head as it moves up, accordingly flash evaporation occurs somewhere inside the test section, where the water local temperature reaches its saturation temperature at that position, which is dependent on the water inlet temperature and its mass flow rate. The steam quality in the test section exit was measured by collecting the steam generated in the test section outlet and condensed in the condenser at specified time. The hydrogen bubbles are injected inside the two – phase mixture flow within the test section. These bubbles act as an exciter for steam generation inside saturated water. Water electrolysis using (12 V) and ionization current (7 A), increases steam quality at test section outlet by (33%) when it is compared to that obtained without water electrolysis. A reduction of (42%) in non-equilibrium temperature difference is achieved using the same ionization settings. The effect of ionization process on flash inception point and temperature is investigated from the experiments. The experimental results are compared to the theoretical results obtained using mathematical model based on solving the mass, momentum and energy equations for two –phase flow assuming separated flow model. The effect of the electrical power used for water ionization is simply simulated in these calculations using mass and heat balance equation that covers the boundary conditions of the system.


Article
Use Of Availability Simulation To Find Optimum Period Of Time Between Schedule Maintenance

Authors: HUSSAIN A. M. AL-BAWI --- Z. I. AL-DAOUD
Pages: 5633-5643
Loading...
Loading...
Abstract

This paper is concerned with the investigation of the optimum period of time between maintenance by the aid of Monte Carlo simulation technique of an old water tube boiler, double identical drums; its capacity is 70 ton/ hour of super heated steam. There are a multitude of failures that are caused by boiler operator's errors, boiler inspector, boiler maintainer and faults of boiler auxiliary equipments which lead to operation parameter deviations and boiler shut down. Changing maintenance plan to be based on optimum period of time between scheduled maintenance and inspection will achieve maximum boiler availability.


Article
Developing Laminar Mixed Convection Heat Transfer Through Concentric Annuli

Loading...
Loading...
Abstract

Theoretical and experimental study has been conducted on developing laminar mixed convection heat transfer air flow through an annulus for both aiding and opposing flow with uniformly heated inner cylinder and adiabatic outer cylinder for the theoretical part and with uniformly heated inner cylinder while the outer cylinder is subjected to the ambient for the experimental part. In the theoretical investigation the energy equation was first solved using (ADI) method, and then the momentum equations and continuity equation were combined as the pressure correction formula and solved by the SIMPLE algorithm. The present theoretical work covers Ra range from 4.55*105 to 5.649*106 and Re range from 300 to 1000 with radius ratio of 0.555 and Pr=0.72. The velocity and temperature profile results have revealed that the secondary flow created by natural convection have significant effects on the heat transfer process and the results reveal an increase in the Nusselt number values as Ra increases. The experimental setup consists of an annulus which has a radius ratio of 0.555 and inner cylinder with a heated length 1.2m subjected to a constant heat flux while the outer cylinder is subjected to the ambient temperature. The investigation covers Reynolds number range from 154 to 724, heat flux varied from 93 W/m2 to 857 W/m2, and annulus angles of inclinations α=0° (horizontal), α=20°, 60° (inclined aiding flow), α=-20,-60 (inclined opposing flow) and α=90° (vertical). The experimental results show an increase in the local Nusselt number values as the heat flux increases and as the angle of the inclination moves from the positive angles (inclined aiding flow) to the horizontal position and from the negative angles (inclined opposing flow) to the horizontal position. The experimental results show that the local Nusselt number values of the aiding flow are higher than that of the opposing flow at the same Reynolds number and heat flux.


Article
Flow Separation Of Axial Compressor Cascade Blades

Authors: Sabah Faleh Habeeb --- Arkan Kh. Al-Taie
Pages: 5663- 5682
Loading...
Loading...
Abstract

An experimental and theoretical investigation of the effect of flow separation on the performance of a cascade NACA 65_(12)10 axial compressor blade has been carried out. The experimental work includes the fabrication of three blades from wood, each having a chord (100mm) but one of these blades having a span of (90mm) for smoke tunnel testing and the other two blades having a span of (380mm) for wind tunnel testing.The two blades were connected by suitable mechanism in order to be fixed in the wind tunnel protractor and rotated in the required stagger angle. The cascade was tested in an open type low-speed subsonic (Mach number=0.117) wind tunnel, for Reynolds number (Re=239605) based on maximum velocity (35 m/s) and airfoil chord length. The total and static pressures were measured in selected points between the two blades for stagger angles of (4 , 0 ,-4 ,-8 and -120) by using a multi-tube manometer and a pitot static tube. The small blade (90mm span) is tested in the smoke tunnel to visualize the real behavior of flow separation. The theoretical work includes using the software FLUENT (V6.2) to simulate the flow between the two blades. The study shows that the flow separation begins when the cascade are inclined at a stagger angle of (-4 ) on the suction side of the lower blade at a position (96%chord experimentally and 98%chord theoretically). Then, the separation zone increases with increased stagger angle (in clockwise direction) and reach to the position (61%chord experimentally and 63%chord theoretically) at a stagger angle (-12 ).These results are validated by a smoke tunnel tests.This separation affects the performance of the compressor, where the static pressure ratio ( / ) decreases as the separation zone gets bigger. The range of working stagger angle is then calculated. It was found in the range (-18 to 36 ). The flow behavior between the two blades shows that the blade-to-blade configuration works as nozzle-diffuser. The theoretical results were compared with the experimental results and good agreement was obtained.


Article
Mathematical Model To Investigate The Temperature And Hardness Distributions During The Annealing And Normalizing Treatment

Authors: B. Shaheen. Bachy
Pages: 5683-5698
Loading...
Loading...
Abstract

Annealing and normalizing treatment are one of the most important heat treatment for the steel and its alloys. In the present work a mathematical model has been used to simulate this process, this model taken in account the variation in the physical material properties and heat transfer coefficient for the surface of metal. A numerical scheme based on control finite volume method has been used. A computer program with C++ language was constricted to found the final solution of the numerical equations. The model was used to estimate the temperatures distribution and the hardness value at each point of the workpiece. Good agreement has been obtained when compared the result of the present model with other experimental published data.


Article
Three-Dimensional Finite Element Analyses of a Single Pile in an Elastoplastic Clayey Soil

Loading...
Loading...
Abstract

A three-dimensional coupled finite element analysis algorithm is developed to predict the behaviour of single piles in clay. Three dimensional 20-noded brick elements are used in the analyses carried out on three documented field studies. Each node carries four degrees of freedom, three being for displacements in the three perpendicular space dimensions while the fourth is allocated for pore water pressure. The behaviour of the material of the pile is idealized through a linear elastic constitutive relationship while that for the soil by the Modified Cam-Clay model both extended to cover three-dimensional characteristics. The load-displacement results from the developed algorithm on the three selected problems from literature show a very good agreement with the observations. Moreover, the build-up of pore fluid pressures and their dissipations were found to be consistent with field measurements also.


Article
PCCC MC-CDMA Combination Performance over Multipath Rayleigh Fading Channel

Authors: Husam Abduldaem. Mohammed
Pages: 5724-5735
Loading...
Loading...
Abstract

This work presents the simulation of a Parallel Concatenation Convolution Coding PCCC with Multi-Carrier Code Division Multiple Access (MC-CDMA) system over multipath fading channels with a comparison with the uncoded data and that uses Serial Concatenated Convolutional Coding SCCC. The decoding technique used in the simulation was iterative decoding since it gives maximum efficiency with six iteration. Modulation schemes that used are Phase Shift Keying (BPSK, QPSK and 16 PSK), along with the Orthogonal Frequency Division Multiplexing (OFDM). The channel models used are as specified in the Third Generation Partnership Project (3GPP) Technical Specification TS 25.101v2.10 with a channel bandwidth of 5 MHz. It was noticed that there is an improvement in the performance of the use of the PCCC data over the SCCC and uncoded data of SNR by many dBs as summarized in table [2] but with 8 and 16 PSK modulation schemes with the multipath fading channel a convergence of the BER to 10-4 cannot be obtained and it remains fluctuating around BER of 10-2.

Keywords


Article
Voltage Stability Enhancement And Loss Reduction Via Optimum Location Of A Series Capacitor
تحسين استقرارية الفولتية وتقليل الخسائر عبر تحديد مكان امثل لوضع متسعة على التوالي

Authors: Firas Mohammed Tuaimah
Pages: 5736-5752
Loading...
Loading...
Abstract

Series compensation is frequently found on long transmission lines used to improve voltage stability. Due to the long transmission lines, voltage begins to decay as the line moves further from the source. Series compensation devices placed strategically on the line to increase the voltage profile of the line to levels near 1.0 p.u.. This paper presents a novel optimum location and optimum percentage compensation value of a series capacitor as a compensation method to enhance the voltage stability and loss reduction. The proposed method is applied to a 11-bus power system. The load flow analysis using Newton-Raphson approach for the 11-bus test system was designed and tested using MATLAB 7 programming language.


Article
Strengthening Of Cracked Reinforced Concrete T-Beam By Jacketing

Authors: ADNAN SADIQ AL-KUAITY
Pages: 5753-5771
Loading...
Loading...
Abstract

This investigation presents an extensive experimental study on the behaviour and strength of reinforced concrete T-beams before and after strengthening by using reinforced concrete jacket. Four full scale beams were first loaded to certain levels of ultimate capacity (0, 60%, 77%, 100% of failure load). Then, after formation of cracks or failure, they were repaired by reinforced concrete jacketing method and tested again up to failure. The main objective of this study is to restore the full ultimate capacity beams failed by flexure and to strengthen the cracked beam. Also, it is aimed to investigate the effect of loadig condition on beam before repair on the ultimate capacity after repair. Extensive measurements of deformations, cracking and strength were made before and after repair throughout all stages of loading. Test results showed that the repairing by reinforced jacketing can effectively restore more than 150% of the full flexural capacity of the original beam. Also reinforced jacket can effectively increase the ultimate capacity of cracked T-beam after repair up to 250%. Furthermore, the use of reinforced jacket for the cracked or failed beams is greatly improved serviceability, deformation behaviour, cracking behaviour as well as ductility of T- beams compared to those of the original beams.The ultimate flexural strength of T-beams failed by flexure and repaired by reinforced concrete jacket can accurately be predicted using conventional ultimate strength method of reinforced concrete .


Article
Copper Etching In Air RegeneratedCupric Chloride Solution

Authors: Baseem H. Fadhil
Pages: 5771-5777
Loading...
Loading...
Abstract

One of the most important steps in the world of printed circuit board manufacturing (PCB) is the copper etching process. Because of its low cost, environment aspects, and simple regeneration techniques, cupric chloride was chosen to be the most attractive etchant. Etching of copper from standard single-sided copper boards used usually for printed circuit board fabrication was conducted in a cell containing cupric chloride solution. Average etching rates were recorded as a function of time, etchant specific gravity, free acid concentration, and temperature. Air was injected continuously in the etching cell during the process enabling mixing and solution regeneration. It is found that best operating conditions to obtain maximum etching rate is at 45-55C, specific gravity of 1.3-1.4, and free acid concentration of 1.3-1.4 M.

Table of content: volume: issue: