Computational Fluid Dynamics (CFD)
D. K. Baghel; S. L. Sinha; S. K. Dewangan
Abstract
Neonatal incubators provide an artificial thermal environment to maintain the thermoregulation of premature babies. Several studies revealed the dry and latent heat exchange estimation between the newborn's body and the surrounding environment. Heat ...
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Neonatal incubators provide an artificial thermal environment to maintain the thermoregulation of premature babies. Several studies revealed the dry and latent heat exchange estimation between the newborn's body and the surrounding environment. Heat transfer due to convection is leading over the thermal radiation in incubators. The aim of this article is to study the airflow modeling and heat transfer coefficient over an infant’s body inside the incubator. For this purpose, an experiment and a numerical simulation are carried out to develop the methodology, and subsequently computational fluid dynamics (CFD) analysis is accomplished to evaluate the heat transfer coefficient of a preterm infant. By means of the shear stress transport (SST K-ω) turbulence model, 3-D computational, models are numerically studied using the commercial CFD tool Star CCM+. Flow visualization reveals that a large-scale flow circulation pattern is produced in the mean region of the enclosed chamber, and small-scale eddies are generated at corners and close to the walls. The numerical results obtained for heat transfer assessment in the present study are validated with experimental and numerical results available in biomedical open literature.
Manufacturing Processes
Elhachemi Bahloul
Abstract
In contour milling, to render the machining process more automated with significant productivity without remaining material after machining, a new recovery coefficient was developed. The coefficient was inserted in the computation of contour parallel tool paths to fix the radial depth of cut in the way ...
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In contour milling, to render the machining process more automated with significant productivity without remaining material after machining, a new recovery coefficient was developed. The coefficient was inserted in the computation of contour parallel tool paths to fix the radial depth of cut in the way to ensure an optimized overlap area between the passes in the corners, without residuals. Thus, this parameter, which has been earlier inserted by the user, is now being independent and is implemented automatically from the input data of the contour shape of the pocket. In order to prove the effectiveness of the present approach, a detailed comparison with the classical methods found in the literature we also performed. The results clearly show that the new method removes the residuals efficiently in an automatic way and minimizes the toolpath length respect to the other methods. Furthermore, this proposed approach can easily be worked on the actual machine tool.
A. Mahamani; S. Jawahar; J. P. Davim
Abstract
In-situ composites have gained the attention of worldwide researchers in the interest of their greater mechanical properties at the lower reinforcement ratio. Controlling the surface quality of components is a paramount task in the grinding process in order to withstand the creep and fatigue load at ...
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In-situ composites have gained the attention of worldwide researchers in the interest of their greater mechanical properties at the lower reinforcement ratio. Controlling the surface quality of components is a paramount task in the grinding process in order to withstand the creep and fatigue load at service conditions. The current effort is intended to examine the mechanism of surface generation in grinding AA6061-TiB2/ZrB2 in-situ composite under different reinforcement ratios, grinding parameters, and wheel materials. The analysis of results indicates that the grinding of the unreinforced alloy is complicated than the composites. Diamond wheel yields superior performance by generating lesser surface roughness and subsurface hardness at all grinding conditions. Among the various grinding parameters, grinding speed and grinding depth are more sensitive than other parameters. This experimental investigation helps to control the surface roughness and subsurface at various grinding conditions.
Heat and Mass Transfer
S. Ravikumar; D. Vijaya Sekhar; Sk. Abzal
Abstract
Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure ...
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Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure gradient, temperature, and heat transfer coefficient rate expressions are calculated. Plotting diagrams were used to analyse the impact of physical parameters on flow characteristics, which were then addressed in greater depth. It is worth noting that raising the gravitational parameter, Jeffery fluid parameter, Hartmann number and Porosity parameter raises the fluid’s velocity. Also, as the Ohmic heating (Jeffery fluid) parameter and porosity parameter increase, the axial pressure gradient drop;, and the temperature of the fluid rises. The rate of heatt transfer coefficient rises in region with an increase in the Radiation parameter, Heat generator parameter and Jeffery fluid parameter. Mathematica software is employed to seek out numerical results.
Composite Materials
Hossein Lexian; Javad Gholampour Darzi; Mohammad Hossein Alaei; Seyed Ali Khalife Soltani
Abstract
This research investigates the effect of feed rate, cutting speed, and orientation of fabric layers on milling forces in high-speed milling of bidirectional C/C composite using the Al2O3 grinding tool in order to decrease the machining time and increase the tool life based on the response surface method ...
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This research investigates the effect of feed rate, cutting speed, and orientation of fabric layers on milling forces in high-speed milling of bidirectional C/C composite using the Al2O3 grinding tool in order to decrease the machining time and increase the tool life based on the response surface method (RSM). For this reason, the above-mentioned parameters were assumed as the input parameters which their effects were investigated on the machining forces (using a milling dynamometer) and tool wear using the central composite design of RSM. Two quadratic models were developed to predict normal and tangential forces in high-speed milling of bidirectional C/C composite. The developed models were then evaluated using three experiments. The results also showed that the orientation of the composite layers has the greatest effect on the milling forces and tool wear after which the tool cutting speed and feed rate respectively. The lowest milling forces were observed at the orientation of (0°,90°), a feed rate of 0.5 m/min, and the cutting speed of 4521.6 m/min.
Composite Materials
A. Niknami; M. Shariyat
Abstract
In the present research, in contrast to the available papers, not only the superelasticity but also the shape memory effects are taken into account in determination of the impact responses. At the same time, in addition to modifying Brinson’s model for the shape memory alloys (SMAs), to include ...
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In the present research, in contrast to the available papers, not only the superelasticity but also the shape memory effects are taken into account in determination of the impact responses. At the same time, in addition to modifying Brinson’s model for the shape memory alloys (SMAs), to include new parameters and loading events, and Hertz contact law, distributions of the SMA phases are considered to be both localized and time-dependent. Furthermore, effects of the impact-induced heat generation and mechanical energy on the resulting histories of the martensite phase volume fraction, stress-strain, temperature, lateral deflection, and contact force are investigated. The generated heat in the SMA wires during the impact is determined through using a Helmholtz free energy function including the latent heat of the phase transformation. The resulting governing equations are solved by the finite element method. The nonlinear refined constitutive laws are solved through a return-mapping Newton-Raphson procedure. Results reveal that incorporation of the heat generation effects is significant in medium/high-velocity impacts or when the stress field is almost uniform.
Hydraulic and Pneumatic Systems
M. Maghroory; A. Farhadi; P. Naderi
Abstract
To maintain the stability trajectory of vehicles under critical driving conditions, anti lock-anti skid controllers, consisting of four anti-lock sub-controllers for each wheel and two anti-skid sub-controllers for left and right pair wheels have been separately designed. Wheel and body systems have ...
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To maintain the stability trajectory of vehicles under critical driving conditions, anti lock-anti skid controllers, consisting of four anti-lock sub-controllers for each wheel and two anti-skid sub-controllers for left and right pair wheels have been separately designed. Wheel and body systems have been simulated with seven degrees of freedom to evaluate the proper functioning of controllers. Anti-lock controllers control brake torque through persistent monitoring of wheels velocity and acceleration and prevent them from locking up by cutting and releasing the brake fluid flow into wheel brake cylinder. On the other hand, anti-skid controllers have been designed in order to maintain the vehicle along a stable trajectory, calculated from the stable spin theory, and to monitor the vehicle’s trajectory during braking. This controller maintains the vehicle along the desirable trajectory by monitoring vehicle yaw angle and comparing it with the reference yaw angle, and also by adjusting the level of brake fluid input into each wheel’s caliper, and subsequently by adjusting brake torque. At the end of the current research, the use of yaw rate control input in place of yaw angle control input in anti-skid controllers has been suggested through a comparative analysis.
Manufacturing Processes
Ghader Faraji*; Mahmoud Mosavi Mashhadi; Karen Abrinia
Abstract
The current study conducted a finite element (FE) and experimental investigation on tubular channel angular pressing as a noble severe plastic deformation technique for producing ultrafine grained and nanostructure tubular components. To examine the effects of the TCAP process on the strain distribution ...
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The current study conducted a finite element (FE) and experimental investigation on tubular channel angular pressing as a noble severe plastic deformation technique for producing ultrafine grained and nanostructure tubular components. To examine the effects of the TCAP process on the strain distribution and deformation behavior, FE simulations were employed. The FE results demonstrated that equivalent plastic strain of 2.1-2.9 was developed after applying one pass TCAP. Analytical investigations were carried out to calculate the accumulated strain during the process. Tube thinning in the early stages of the process was observed as a result of tensile circumferential strains but this could be compensated for by the back pressure effect resulting from the next shear zones and also compressive circumferential strain resulting from decreasing the tube diameter. Microstructural observations showed significant grain refinement after one pass TCAP on AZ91 magnesium alloy at 300 ºC. Microhardness measurements demonstrated increasing hardness to 78 HV from the initial value of 51 HV.
Thermodynamics and Cumbustion
A. H. Kakaee; J. Zareei
Abstract
Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone ...
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Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone burned/unburned model with the fuel burning rate described by aWiebe function was used for modeling in-cylinder combustion. For studying this issue, thermodynamic models such as Woshni, Isentropic, etc. were used. Then, the experiments were carried out to validate the calculated data. The objective of the present work was to examine effect of ignition timing on the performance of an SI engine. For achieving this goal, at the speed of 3400 rpm, ignition timing was changed in the range of 41 degrees before the top dead centre to 10 degrees after TDC. By changing the ignition timing, the results of some characteristics such as power, torque, indicatory pressure, exhaust emission and efficiency were obtained and compared. The results demonstrated that optimal power and torque and the maximum efficiency were achieved at 31 degrees before the top dead centre and engine performance was improved by changing timing angle. It was also indicated that the maximum thermal efficiency could be accomplished while peak pressure occurred between 5 and 15 degrees of ATDC. The amounts of O2, CO2 and CO were almost constant but HC increased with increase of ignition timing.
Heat and Mass Transfer
Sathish Kumar M; Sandeep N; Rushi Kumar B
Abstract
Effect of nonlinear thermal radiation on the unsteady magnetohydrodynamic slip flow of Casson fluid between parallel disks in the presence of thermophoresis and Brownian motion effects are investigated numerically. A similarity transformation is employed to reduce the governing partial differential equations ...
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Effect of nonlinear thermal radiation on the unsteady magnetohydrodynamic slip flow of Casson fluid between parallel disks in the presence of thermophoresis and Brownian motion effects are investigated numerically. A similarity transformation is employed to reduce the governing partial differential equations into ordinary differential equations. Further, Runge-Kutta and Newton’s methods are adopted to solve the reduced ordinary differential equations. The effect of non-dimensional governing parameters, namely magnetic field parameter, Casson parameter, thermophoresis parameter, Brownian motion parameter, thermal radiation parameter, unsteadiness parameter, velocity slip parameter and temperature slip parameter on velocity, temperature and concentration fields are discussed and presented through graphs. Reduced Nusselt and Sherwood numbers are computed and presented through a table. It is found that rising values of nonlinear thermal radiation parameter depreciate the reduced Nusselt and Sherwood numbers. Thermophoresis and Brownian motion parameters have tendency to regulate the thermal and concentration boundary layers. Rising values of Casson parameter enhances the heat and mass transfer rate.
Mohamed S. Elmasry; Hammad T. Elmetwally; Mohamed N. El-Sheikh; Ragab K. Abdel-Magied
Abstract
The tube flange is typically performed using welding, forging methods, which cost effort and time. In the present work, a metal spinning process to form tube flange was proposed. A flange-forming tool was developed based on the outer tube diameter to form the flange. It consists of three components namely; ...
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The tube flange is typically performed using welding, forging methods, which cost effort and time. In the present work, a metal spinning process to form tube flange was proposed. A flange-forming tool was developed based on the outer tube diameter to form the flange. It consists of three components namely; collet, mandrill, and roller. An experimental work was conducted to investigate the process parameters of the flange process of lead tubes. Different working conditions are considered during conducting of flanged specimens, e.g. rotating speed, feed rate, and tube wall thickness. The effects of the working conditions on the flanging loads were investigated. The results reveal that the flanging load increases with the increasing rotational speed, tube wall thickness, and with both lower and higher values of feed rate while it decreases with medium values of feed rates. To show the effect of the working conditions on the flange characteristics, a parametric study was conducted. The results show that the surface hardness and surface roughness of the formed flange is improved with increasing all working conditions. A theoretical analysis to model the flange forming loads (axial, radial and tangential) was presented. A comparison between forming loads analytically and experimentally was discussed. The comparison indicates that this percentage of error up to 4% occurs, instead of error percentage up to 28%, in case of neglecting the low feed rate.
Fracture Mechanics
Abstract
In sheet metal forming processes with complex strain paths, a part is subjected to large plastic deformation. This severe plastic deformation leads to high plastic strain localization zones and subsequent accumulation of those strains. Then internal and superficial micro-defects and in other words ductile ...
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In sheet metal forming processes with complex strain paths, a part is subjected to large plastic deformation. This severe plastic deformation leads to high plastic strain localization zones and subsequent accumulation of those strains. Then internal and superficial micro-defects and in other words ductile damage is created. This damage causes quality problems such as fracture. Therefore, design engineers need to accurately estimate the damage initiation and its growth. In this paper, initiation and evolution of damage has been predicted using Lemaitre’s damage and forming limit diagram (FLD) damage models for automotive panel forming, because of its nonlinear strain paths. Lemaitre’s damage criterion has been implemented as a subroutine for an elastic-plastic material and plane stress and finite strain theories. Using this subroutine in explicit finite element code, damage initiation and evolution is predicted for the above mentioned process and the results obtained by FLD and Lemaitre models are compared. In this paper, FLD and Lemaitre damage models results show the fact that the damage localization zones are corresponding to the equivalent plastic strain distributions. Comparison of the FLD damage and Lemaitre damage results show that in an automotive panel forming process, both models predict initiation of cracks in the edges of a sheet. Hence, it is concluded that finite element method combined with continuum damage mechanics can be used as a reliable and rapid tool to predict damage evolution in sheet metal forming processes with nonlinear and complex strain paths such as automotive panel forming.
Plasticity
F. Moayyedian; M. Kadkhodayan
Abstract
One of the new research fields in plasticity is related to choosing a proper non-associated flow rule (NAFR), instead of the associated one (AFR), to predict the experimental results more accurately. The idea of the current research is derived from combining von Mises and Tresca criteria in the places ...
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One of the new research fields in plasticity is related to choosing a proper non-associated flow rule (NAFR), instead of the associated one (AFR), to predict the experimental results more accurately. The idea of the current research is derived from combining von Mises and Tresca criteria in the places of yield and plastic potential surfaces in rate-independent plasticity. This idea is implemented using backward Euler method in non-linear finite element simulation. The results are compared with the experimental data for an internally pressurized thick-walled cylinder and it is demonstrates that, using the proposed NAFR in rate-independent plasticity, the experimental results could be predicted more accurately. Finally, it can be said that the current research confirms the results of the previous works on rate-dependent plasticity (viscoplasticity) in steady state conditions.
Forming
Mehdi Bostan Shirin; Ramin Hashemi; Ahmad Assempour
Abstract
An enhanced unfolding Inverse Finite Element Method (IFEM) has been used together with an extended strain-based forming limit diagram (EFLD) to develop a fast and reliable approach to predict the feasibility of the deep drawing process of a part and determining where the failure or defects can occur. ...
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An enhanced unfolding Inverse Finite Element Method (IFEM) has been used together with an extended strain-based forming limit diagram (EFLD) to develop a fast and reliable approach to predict the feasibility of the deep drawing process of a part and determining where the failure or defects can occur. In the developed unfolding IFEM, the meshed part is properly fold out on the flat sheet and treated as a 2D problem to reduce the computation time. The large deformation relations, nonlinear material behavior and friction conditions in the blank holder zone have also been considered to improve the accuracy and capability of the proposed IFEM. The extended strain-based forming limit diagram based on the Marciniak and Kuczynski (M-K) model has been computed and used to predict the onset of necking during sheet processing. The EFLD is built based on equivalent plastic strains and material flow direction at the end of forming. This new forming limit diagram is much less strain path dependent than the conventional forming limit diagram. Furthermore, the use and interpretation of this new diagram are easier than the stress-based forming limit diagram. Finally, two applied examples have been presented to demonstrate the capability of the proposed approach.
Production Methods
Mohammad Ali Farsi
Abstract
The reliability of manufacturing systems modeling and analysis is a complex process. Usually, their behavior is similar to multi-state systems. The configurations of such systems, possibly with load sharing and other structural dependencies, are designed to provide high reliability/availability. Consequently, ...
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The reliability of manufacturing systems modeling and analysis is a complex process. Usually, their behavior is similar to multi-state systems. The configurations of such systems, possibly with load sharing and other structural dependencies, are designed to provide high reliability/availability. Consequently, this scheme can help companies to improve efficiency and reduce operating costs. Maintenance and part replacement are implemented during operation and utilization to keep their performance. Decision-making about spare ordering is difficult because of the interconnection between spare parts inventory and maintenance strategy. In this paper, the characteristic parameters of spare parts inventory management and maintenance policies are jointly considered for multi-machine systems (manufacturing systems) with different types of dependencies among them (economic, load-sharing, and multi-state configuration). Two maintenance policies are considered: condition-based and preventive maintenance. The interactions between maintenance policies and spare parts management are considered for determining a manufacturing system’s cost and availability. The influence of these factors is investigated. Load sharing factor and ordering time are more important, and their influence is higher than others.
Fluid Mechanics
J. Jamaati; H. Niazmand; M. Renksizbulut
Abstract
A numerical study of 3D electrokinetic flows through micromixers was performed. The micromixers considered here consisted of heterogeneous rectangular microchannels with prescribed patterns of zeta-potential at their walls. Numerical simulation of electroosmotic flows within heterogeneous channels requires ...
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A numerical study of 3D electrokinetic flows through micromixers was performed. The micromixers considered here consisted of heterogeneous rectangular microchannels with prescribed patterns of zeta-potential at their walls. Numerical simulation of electroosmotic flows within heterogeneous channels requires solution of the Navier-Stokes, Ernest-Plank and species concentration equations. It is known that a 3D solution of these equations is computationally very intensive. Therefore, the well-known Helmholtz-Smoluchowski model is often used in numerical simulation of electroosmotic flows. According to 2D studies on electrokinetic mixing inside heterogeneous channels, existence of vortices within the flow field always increases mixing performance. Hence, it may be expected that similar observations pertain to mixing in 3D flows as well. However, investigations on 3D micromixers identified situations in which existence of vortices had little or no significant benefit to the mixing performance. Findings of the present work indicated degree of flow asymmetry as a key parameter for the mixing performance. Since 3D flows are more capable of developing asymmetrical flow patterns, they are expected to have better mixing performance than their 2D counterparts. The results presented here for different 3D cases showed that mixing performance could be improved significantly depending on the alignment of vortex plane relative to the mixing interface of the fluids. These observations confirmed that 2D simulations of mixing could not fully explain behavior of passive micromixers.
Machining
S. L. N. Jayasimha; Ganapathy Bawge; H. P. Raju
Abstract
Traditional methods of finishing like grinding, lapping, and honing are limited to finishing of vital shapes such as flat and circular. These conventional methods are lagging for processing components that are fabricated by hard materials, involving complicated profiles in particular. Hence, it is essential ...
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Traditional methods of finishing like grinding, lapping, and honing are limited to finishing of vital shapes such as flat and circular. These conventional methods are lagging for processing components that are fabricated by hard materials, involving complicated profiles in particular. Hence, it is essential to explore a finishing process, which addresses wide applications, better accuracy, higher efficiency, consistent quality and economy in finishing complex shaped parts. So, a new precision finishing process like extrusion honing has been implemented for polishing from several microns to the nano level. This work aims to assess the influence of a number of abrasive media passes on the surface integrity of aluminum, copper, and titanium grade-2 materials. The study has been performed by adopting an abrasive 36 mesh size with a concentration of 40% followed by 10 abrasive media passes. The influence of these process parameters has been studied in analyzing the roughness characteristics Ra, Rmax, Rz, and Rmax/Ra and the nature of surface induced by SEM characterization for the metals of consideration using the extrusion honing process.
Fluid Mechanics
Pedram Hanafizadeh; Amirmohammad Sattari; Seyed Erfan Hosseinidoost; Morteza Molaei; Mehdi Ashjaee
Abstract
Detecting bubble in two-phase flow has been a basic issue in two-phase flow systems. A new method for measuring the frequency of bubble formation is presented in this paper. For this purpose, an electronic device was designed and constructed which works based on a change in intensity of laser beam. For ...
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Detecting bubble in two-phase flow has been a basic issue in two-phase flow systems. A new method for measuring the frequency of bubble formation is presented in this paper. For this purpose, an electronic device was designed and constructed which works based on a change in intensity of laser beam. For this purpose, continues light beam is embedded just above the needle, which is received by a phototransistor. When bubbles go through this light beam, make a deviation on that and change the intensity of light. So, the electrical resistance between two bases of phototransistor changes and this variation sensed by an electronic board. According to the number of interruption and duration time, the frequency of bubble formation can be calculated. Liquid and gas phases of present work are water and air respectively. Tests are performed in constant liquid height (60 mm above the needle), constant needle diameter (1.6 mm), and gas flow rates between 50 to 1200 ml/hr. Also, three other methods utilized for measuring bubble frequency: image processing (IP), numerical modeling, and theoretical model. Results show that with increasing flow rate of the gas phase frequency of formation increases approximately in a linear manner. Validation of methods with IP method shows that the new device has very good accuracy for measuring bubble formation frequency. So because of the simplicity of using and low cost, it can be a superseded method of image processing.
Energy Science and Technology
Shaaban Ghodbanan; Reza Alizadeh; Sirous Shafiei; Javad Rahbar Shahrouzi
Abstract
In this study, the energy assessment and heat recovery analysis of the multi-cylinder drying section were carried out in a fluting paper machine. The specific heat consumption per unit of paper was determined to be about 4.7 GJ/ton of paper and accordingly, the machine consumed about 1.71 tons of steam ...
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In this study, the energy assessment and heat recovery analysis of the multi-cylinder drying section were carried out in a fluting paper machine. The specific heat consumption per unit of paper was determined to be about 4.7 GJ/ton of paper and accordingly, the machine consumed about 1.71 tons of steam per ton of produced paper. The temperature efficiency of the heat exchanger and the recovering efficiency of the heat recovery system within the paper machine have been determined to be about 50% and 4%, respectively. The results show that the steam used in the heat recovery system can be reduced by about 0.95 tons/h due to adjusting the supply air temperature to the optimum range, which corresponds to about a 5.2% reduction in energy input and 4% improvement in dryer efficiency resulting nearly 31,000 $ savings per year. Also, the CO2 emission due to gas use can be decreased by about 925 tons/y.
Fluid Mechanics
S. O. Salawu; A. Abolarinwa; O. J. Fenuga
Abstract
In this research, the transient analysis of radiative combustible viscous chemical reactive two-step exothermic fluid flow past a permeable medium with various kinetics, i.e., bimolecular, Arrhenius, and sensitized, are investigated. The hydromagnetic liquid is influenced by periodic vicissitudes in ...
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In this research, the transient analysis of radiative combustible viscous chemical reactive two-step exothermic fluid flow past a permeable medium with various kinetics, i.e., bimolecular, Arrhenius, and sensitized, are investigated. The hydromagnetic liquid is influenced by periodic vicissitudes in the axial pressure gradient and time along the channel axis in the occurrence of walls asymmetric convective cooling. The convectional heat transport at the wall surfaces with the neighboring space takes after the cooling law. The non-dimensional principal flow equations are computationally solved by applying convergent and absolutely stable semi-implicit finite difference techniques. The influences of the fluid terms associated with the momentum and energy equations are graphically presented and discussed quantitatively. The results show that the reaction parameter is very sensitive, and it, therefore, needs to be carefully monitored to avoid systems blow up. Also, a rise in the values of the second step term enhances the combustion rate and thereby reduces the release of unburned hydrocarbon that polluted the environment.
Vibration
Mahdi Karimi; Alireza Shooshtari; Soheil Razavi
Abstract
In this paper, nonlinear equations of motion for laminated composite rectangular plates based on the first order shear deformation theory were derived. Using a perturbation method, the nonlinear equation of motion was solved and analytical relations were obtained for natural and nonlinear frequencies. ...
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In this paper, nonlinear equations of motion for laminated composite rectangular plates based on the first order shear deformation theory were derived. Using a perturbation method, the nonlinear equation of motion was solved and analytical relations were obtained for natural and nonlinear frequencies. After proving the validity of the obtained analytical relations, as an alternative and simple modeling technique, ANN was also employed to model the laminated rectangular plates and predict effects of different parameters on the natural and nonlinear frequencies of the plates. In this respect, an optimal ANN was selected and trained by training data sets obtained from analytical method and also tested by testing data sets. The obtained results were in good agreement with the analytical and published results.
Thermodynamics and Cumbustion
M. V. S. Murali Krishna; V. V. R. Seshagiri Rao; P. V. K. Murthy; T. K. K. Reddy
Abstract
Experiments were conducted to evaluate the performance of a low heat rejection (LHR) diesel engine. Performance parameters and emission levels were determined at various magnitudes of brake mean effective pressure. Combustion characteristics of the engine were measured with TDC (top dead centre) encoder, ...
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Experiments were conducted to evaluate the performance of a low heat rejection (LHR) diesel engine. Performance parameters and emission levels were determined at various magnitudes of brake mean effective pressure. Combustion characteristics of the engine were measured with TDC (top dead centre) encoder, pressure transducer, console and special pressure-crank angle software package at peak load operation of the engine. Conventional engine (CE) and LHR engine showed improved performance at recommended injection timing of 27obTDC and recommended injection pressure of 190 bar, when compared with CE with pure diesel operation. Peak brake thermal efficiency increased by 18%, smoke levels decreased by 48% and NOx levels decreased by 38% with LHR engine relatively at its optimum injection timing and maximum induction of ethanol when compared with pure diesel operation of CE at manufacturer’s recommended injection timing.
Heat and Mass Transfer
M. Ghalambaz; A. Noghrehabadi
Abstract
In this paper, natural convection heat transfer over a vertical plate in a Darcy porous medium saturated with a nanofluid subject to heat generation/absorption was theoretically studied. The governing partial differential equations were transformed to a set of ordinary differential equations using similarity ...
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In this paper, natural convection heat transfer over a vertical plate in a Darcy porous medium saturated with a nanofluid subject to heat generation/absorption was theoretically studied. The governing partial differential equations were transformed to a set of ordinary differential equations using similarity transformations and solved using finite difference method. The influence of parametric variation of the Brownian motion parameter, thermophoresis parameter and heat generation/absorption parameter on velocity, temperature and nanoparticles concentration profiles was graphically shown. Impact of non-dimensional parameters on the reduced Nusselt number and reduced Sherwood number was also investigated. The results showed that an increase in the heat generation/absorption parameter would increase temperature and velocity profiles; but, it would decrease concentration profiles. Increase of thermophoresis parameter increased magnitude of concentration profiles while not showing any significant effect on velocity and temperature profiles. The results also indicated that increase of Brownian motion parameter did not demonstrate any significant effect on the magnitude of velocity and temperature profiles. It was found that an increase in the heat generation/absorption parameter decreased the reduced Nusselt number whereas it increased the reduced Sherwood number. For negative values of the Brownian motion parameter, increase of the thermophoresis parameter increased the reduced Nusselt and Sherwood numbers.
Heat and Mass Transfer
M. Sh. Mazidi; M. Alizadeh; L. Nourpour; V. Shojaee Shal
Abstract
In the design of heat exchangers, it is necessary to determine the heat transfer rate between hot and cold fluids in order to calculate the overall heat transfer coefficient and the heat exchanger efficiency. Heat transfer rate can be determined by inverse methods. In this study, the unknown space-time ...
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In the design of heat exchangers, it is necessary to determine the heat transfer rate between hot and cold fluids in order to calculate the overall heat transfer coefficient and the heat exchanger efficiency. Heat transfer rate can be determined by inverse methods. In this study, the unknown space-time dependent heat flux imposed on the wall of a heat exchanger internal tube is estimated by applying an inverse method and simulated temperature measurements at the specified points in the flow field. It is supposed that no prior information is available on the variation of the unknown heat flux function. Variable metric method which belongs to the function estimation approach is utilized to predicate the unknown function by minimizing an objective function. Four versions of the presented inverse method, named DFP, BFGS, SR1, and Biggs, are used to solve the problem and the results obtained by each version are compared. The estimation of the heat flux depends on the location of the sensor and the uncertainties associated with temperature measurements. The influence of each factor is investigated in this paper. Results show that variable metric method is a rapid and precise technique for estimating unknown boundary conditions in inverse heat convection problems.
Welding
M. Azizpour; M. Ghoreishi; A. Khorram
Abstract
This paper was aimed to report the 3D finite element analysis simulation of laser welding process of Ti6Al4V 1.7 mm sheets in butt joint in order to predict the temperature distribution, hardness, and weld geometry. The butt-joint welds were made using CO2 laser with the maximum power of 2.2 kW in the ...
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This paper was aimed to report the 3D finite element analysis simulation of laser welding process of Ti6Al4V 1.7 mm sheets in butt joint in order to predict the temperature distribution, hardness, and weld geometry. The butt-joint welds were made using CO2 laser with the maximum power of 2.2 kW in the continuous wave mode. A part of the experimental work was carried out to verify the weld geometry with specific weld parameters including power, speed, and focal position. Another part investigated the effect of focal position on the weld bead geometry. Subsequently, the shapes of the molten pool were predicted by the numerical analysis method and compared with the results obtained through the experimentation, which led to finding a good agreement.
