Heat and Mass Transfer
Hasan Najafi Khaboshan; Hamid Reza Nazif
Abstract
In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the ...
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In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the effect of two schemesfor the domain discretization to be used in the solution variables’ gradients on simulation results is investigated. The secondary flow causes an increase in the numbers of multi-longitudinal vortices (MLV) by changing the angle of pitches. These phenomena permit the cold fluid flow to stream in more paths from center to tube wall and better condition for mixing of fluids. Consequently, the heat transfer enhances by using the alternating oval tubes. However, forming the multi-longitudinal vortices causes an increase in pressure drop. Also, by raising the angle of pitches, the friction factor and the average of Nusselt number are amplified. It is also observed that the average heat transfer coefficient in the transition range is more than other areas. The mean Nussult numbers of this kind of tubes in the angles of 40, 60, 80, and 90 improved 7.77%, 14.6%, 16.93%, and 24.42%, respectively in comparison with the round tube. The performance evaluation criteria (PEC) for all alternating oval tubes under the constant inlet velocity boundary condition indicated that the highest value (PEC=1.09) had been obtained at the lowest Reynolds number (Re=10,000) in the alternating oval tube 90°.
Deepak Kumar Sharma; Tikendra Nath Verma
Abstract
The present study focuses on the optimization in the use of non-petroleum fuel derived from waste fish oil fuels, as a replacement for petroleum diesel fuel for compression ignition engine. The study comprises of comparison between results of fish oil biodiesel-diesel blends in a compression ignition ...
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The present study focuses on the optimization in the use of non-petroleum fuel derived from waste fish oil fuels, as a replacement for petroleum diesel fuel for compression ignition engine. The study comprises of comparison between results of fish oil biodiesel-diesel blends in a compression ignition engine. Fuel properties such as viscosity, density, heat value of fuel, cetane number and a flash point of fish oil biodiesel and its blends with diesel were studied. The fish oil biodiesel (60, 40, 20, and 0%) – diesel (40, 60, 80 and 100%) are blended at volume basis. The results show reduction in thermal efficiency, temperature, particulate matter and nitrogen oxides emission; while showing an increase in higher specific fuel consumption, ignition delay, carbon dioxide and smoke emissions. The B20 fuel blend improves BTE by 4.7%, CO2 emissions has been increased by 2.56%, while SFC is lowered by 7.92% as compared to diesel fuel. In biodiesel blend (B20), the highest reduction in NOx by 14.9%, particulate by 4.22% is observed although smoke emission slightly rises with an increase in fish oil in the blends, as compared to diesel fuel.
Fatigue
Liela Abbasiniyan; Seyed hamed Hoseini; Shirko faroughi
Abstract
In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate various features of dynamic brittle fracture such as crack ...
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In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate various features of dynamic brittle fracture such as crack propagation, asymmetries of crack paths and successive branching. The fracture simulation of thin plates made of a brittle material with different crack and notch patterns has been considered. The molecular dynamics open-source free LAMMPS code has been updated to implement the peridynamic theory based modeling tool for two-dimensional numerical analysis. The simulations show that, the simulation time significantly decreases which is the core and distracting deficiency of the peridynamic method. Moreover, the simulated results demonstrate the capability of peridynamic theory to precisely predict the crack propagation paths as well as crack branching during dynamic fracture process. The good agreement between simulation and experiments is achieved.
Rasool Esmaelnajad; Navid Farrokhi
Abstract
Increasing the power and improving the performance of diesel engines is always considered by diesel engine manufacturers. Changing the geometry of the injector outlet orifice has major impact on fuel-air mixing and combustion. In the current study, geometry of the injector orifice is changed from circular ...
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Increasing the power and improving the performance of diesel engines is always considered by diesel engine manufacturers. Changing the geometry of the injector outlet orifice has major impact on fuel-air mixing and combustion. In the current study, geometry of the injector orifice is changed from circular to annular cross-section, and the effect of different injection pressures on diesel engine performance is investigated. All numerical simulations are performed by using AVL Fire code. The results show that the annular injector improves combustion and engine performance by forming better fuel distribution. Fuel injection pressure affects the performance of the annular injector in terms of droplets distribution and breakup. At low injection pressures, due to the long injection duration, most of the fuel energy release occurs after top dead center (TDC). Therefore, the engine performance is improved, and the combustion chamber temperature and pressure are limited. However, at high injection pressures, less combustion occurs after TDC. By changing the injector geometry to the injector with annular cross-section orifice, the maximum reduction in SFC value is for case P5 and injection durations 10 degrees, which is decreased by 21.4%. In the studied cases, the maximum power increase was 15% for a 2.5% increase of fuel at injection pressure of 100MPa. While NO pollutant increased slightly by changing the type of injector at different injection pressures, the soot produced at the beginning of the combustion process is well oxidized before the end of the work phase, and its amount reached less than 2e-6.
Heat and Mass Transfer
L. Ramamohan Reddy; M. C. Raju; G. S. S. Raju; S. M. Ibrahim
Abstract
The paper aims at investigating the effects of chemical reaction and thermal radiation on the steady two-dimensional laminar flow of viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium. The radiative heat flux is assumed to ...
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The paper aims at investigating the effects of chemical reaction and thermal radiation on the steady two-dimensional laminar flow of viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium. The radiative heat flux is assumed to follow Rosseland approximation. The governing equations of momentum, angular momentum, energy, and species equations are solved numerically using Runge-Kutta fourth order method with the shooting technique. The effects of various parameters on the velocity, microrotation, temperature and concentration field as well as skin friction coefficient, Nusselt number and Sherwood number are shown graphically and tabulated. It is observed that the micropolar fluid helps the reduction of drag forces and also acts as a cooling agent. It was found that the skin-friction coefficient, heat transfer rate, and mass transfer rate are decreased, and the gradient of angular velocity increases as the inverse Darcy number, porous medium inertia coefficient, or magnetic field parameter increase. Increases in the heat generation/absorption coefficient caused increases in the skin-friction coefficient and decrease the heat transfer rate. It was noticed that the increase in radiation parameter or Prandtl number caused a decrease in the skin-friction coefficient and an increase in the heat transfer rate. In addition, it was found that the increase in Schmidt number and chemical reaction caused a decrease in the skin-friction coefficient and an increase in the mass transfer rate.
Fluid Mechanics
Aminreza Noghrehabadi; Mohammad Ghalambaz; Mehdi Ghalambaz; Afshin Ghanbarzadeh
Abstract
In the present paper, the flow and heat transfer of two types of nanofluids, namely, silver-water and silicon dioxide-water, were theoretically analyzed over an isothermal continues stretching sheet. To this purpose, the governing partial differential equations were converted to a set of nonlinear differential ...
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In the present paper, the flow and heat transfer of two types of nanofluids, namely, silver-water and silicon dioxide-water, were theoretically analyzed over an isothermal continues stretching sheet. To this purpose, the governing partial differential equations were converted to a set of nonlinear differential equations using similarity transforms and were then analytically solved. It was found that the magnitude of velocity profiles in the case of SiO2-water nanofluid was higher than that of Ag-water nanofluid. The results showed that the increase of nanoparticle volume fraction increased the non-dimensional temperature and thickness of thermal boundary layer. In both cases of silver and silicon dioxide, increase of nanoparticle volume fraction increased the reduced Nusselt number and shear stress. It was also demonstrated that the increase of the reduced Nusselt number was higher for silicon dioxide nanoparticles than silver nanoparticles. However, the thermal conductivity of silver was much higher than that of silicon dioxide.
Composite Materials
S. Khalilpourazary; N. Payam
Abstract
Warpage and shrinkage control are important factors in proving the quality of thin-wall parts in injection modeling process. In the present paper, grey relational analysis was used in order to optimize these two parameters in manufacturing plastic bush of articulated garden tractor. The material used ...
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Warpage and shrinkage control are important factors in proving the quality of thin-wall parts in injection modeling process. In the present paper, grey relational analysis was used in order to optimize these two parameters in manufacturing plastic bush of articulated garden tractor. The material used in the plastic bush is Derlin 500. The input parameters in the process were selected according to their effect on shrinkage and warpage values, melt temperature, mold temperature, injection rate, injection pressure, and packing pressure. Then, the Taguchi method was applied to design the experiments, and through the use of Mold Flow software injection molding process was simulated based on these experiments and the input parameters. Based on the results obtained from the simulation, the input parameters were analyzed in three levels using grey relational analysis. Then, analysis of variance and confirmation tests were carried out on the output of grey relational analysis to predict the optimum values of the input parameters and to calculate the dimensional changes of the plastic bush. Gaining these values, the plastic bush sample was manufactured, and its 3D point cloud model was generated by a scanner. At the end, by generating 3D solid model of the plastic bush its dimensional features were studied. The comparison of the warpage and shrinkage values between grey relational analysis and 3D CAD model indicates the precision of the method in controlling and measuring these two parameters.
Manufacturing Processes
Abstract
Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet ...
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Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet metal parts. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. Material property of AISI 1010 is used in FE model and experiments. The aim of this study is to identify the response related to deformation and characterize the effect of laser power with respect to the bending angle for a square sheet part. An experimental setup including a Nd:YAG laser Model IQL-10 with maximum mean laser power of 500 W is used for the experiments to verify FE analysis results. It is observed that numerical results are relatively in good agreement with the experimental results. Results also show that increasing laser power increases the bending angle.
Heat and Mass Transfer
Aminreza Noghrehabadi; Mohammad Ghalambaz; Amin Samimi
Abstract
In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective ...
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In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective surface boundary condition. As both boundary conditions tended to infinity, the combination of series solutions with the Padé approximants was used for handling boundary conditions on the semi-infinite domain of solution. The combination of power series and Padé proposed an alternative approach of solution which did not require small parameters and avoided linearization and physically unrealistic assumptions. The results of the present approach were compared with numerical results as well as those of previous works reported in the literature. The obtained results represented remarkable accuracy in comparison with the numerical ones. Finally, reduced Nusselt number, as an important parameter in heat transfer, was calculated by the obtained analytical solution. The present power series-Padé technique was very simple and effective, which could develop a simple analytic solution for flow and heat transfer over the flat plate. The results of the present study could be easily used in practical applications.
Fluid Mechanics
Javad Shahbazi Karami; GH. Payganeh
Abstract
In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity ...
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In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity distribution of fluid inside the tube as well as the fluid in the gap between tube and matrices. As a result of non-homogenous distribution of temperature on tube surface, circulating flows are generated inside the tube which may have considerable effects on heat transfer phenomenon. It is seen that in 600 s after start, number of the circulating flows doubles. Analysis of temperature distribution reveals thatmiddle part of the tube reaches 500 ̊C after 600 s from process start and other parts have higher temperature. By applying an efficient control method for heater elements, temperature distribution of the tube reaches a homogenous form.
Manufacturing Processes
Dastagiri Mabbu -; Srinivasa Rao P.; Madar Valli P.
Abstract
Electro Discharge Machining (EDM) is an incredibly recognizable machining for ticklishness profiles in ’difficult to machine ‘materials. In EDM, the material ejection of the cathode is cultivated through exact controlled electric pulse (the flash), which changes the metals of two terminals ...
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Electro Discharge Machining (EDM) is an incredibly recognizable machining for ticklishness profiles in ’difficult to machine ‘materials. In EDM, the material ejection of the cathode is cultivated through exact controlled electric pulse (the flash), which changes the metals of two terminals into dissolve and vaporize, as a result of the breakdown of the dielectric medium. The most commonly used dielectric media are kerosene, paraffin, glycerin, transformer oil, and EDM oil; all are derived from petroleum. These dielectric media undergo pyrolysis and carbon soot formation is deposited on work electrode, and sometimes carbon precipitates into work. To overcome these effects vegetable oils are tried as alternate dielectric media. Pongamia Pinnetta is abundantly available in most countries; and it is cheaper and non-edible. Pongamia Pinnata (PP) oil is extracted from plant seeds, and is blended with EDM oil and several experimentations are done to find its suitability. Operational variables with respect to input and output parameters are identified. Some of these are best EWR, MRR, TWR, and SR with applied current (I), pulse on time (Ton), and pulse off time (Toff) are the ones picked as the input process factors; because for the industrial application many machinists choose these three as the input parameters; and other is constant and picked under specific requirements only. After the successful completion of this experimentations, Pongamia Pinnata oil blends are fit for the industrial application using technique of order preferancing with similar to ideal solution [TOPSIS]. It is observed that no carbon soot formation takes place in the work component with PP oil as the dielectric fluid.
Fracture Mechanics
Alireza Hassani; Amin Hassani; Mojtaba Mahmoudi Monfared
Abstract
Abstract: The solution to problem of an orthotropic long cylinder subjected to torsional loading is first obtained by means of separation valuables. The cylinder is twisted by two lateral shear tractions and the ends of the cylinder surface of the cylinder are stress-free. First, the domain under consideration ...
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Abstract: The solution to problem of an orthotropic long cylinder subjected to torsional loading is first obtained by means of separation valuables. The cylinder is twisted by two lateral shear tractions and the ends of the cylinder surface of the cylinder are stress-free. First, the domain under consideration is weakened by an axisymmetric rotational Somigliana ring dislocation. The dislocation solution is employed to derive a set of Cauchy singular integral equations for the analysis of multiple axisymmetric planner cracks. The numerical solution to these integral equations is used to determine the stress intensity factors (SIFs) for the tips of the concentric planar cracks A preliminary comparison between results of this study and those available in the literature is performed to confirm the validity of the proposed technique. Several examples of multiple concentric planner cracks are solved and displayed graphically. Furthermore, Configuration of the cracks and the interaction between cracks is studied.
Vibration
Nadia Parandeh Afshar; Farhad S. Samani; Moslem Molaie
Abstract
Recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. The purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an Euler-Bernoulli beam with a nonlinear vibratory behavior under ...
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Recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. The purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an Euler-Bernoulli beam with a nonlinear vibratory behavior under concentrated moving load. The goal parameter in the optimization is maximum deflection of the beam. The large deformation for beam modeling is considered, i.e. the relation between strains and deflections is nonlinear. The force magnitude and beam length are two effective factors for the beam deflection. Vibration absorber with linear damping and linear or nonlinear stiffness is also considered in this manuscript. The results show that, for normal forces and short beams, linear and nonlinear models have similar behaviors, while surveying nonlinear behavior is necessary by increasing the force and length of the beam, i.e. large deflections. Moreover, the difference between linear and nonlinear beam models for regular force magnitudes and beam lengths is negligible. For higher loads and longer beams, beam model nonlinearity can be important. Results demonstrate that,in the presented numerical values (train bridge application) for cubic nonlinear vibration absorber, there are two optimal locations for vibration absorber installation: one inclined from the middle of the beam to the direction of moving loads and the second which is more interestingly inclined from the middle of the beam to moving loads in the opposite direction. Moreover, depending on the model's numerical parameters, for short beams, linear vibration absorber is more effective, while for long beams, cubic nonlinear beam behaves better than the linear one.
Mahdi Zakyani
Abstract
Large eddy simulations of non-reactive Delft II and Sydney bluff body flow are performed using different sub-grid scale models. Simulation of non-reactive burners is useful when studying flow characteristics inside reactive burners. As turbulent combustion simulation is rather an intricate task, it is ...
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Large eddy simulations of non-reactive Delft II and Sydney bluff body flow are performed using different sub-grid scale models. Simulation of non-reactive burners is useful when studying flow characteristics inside reactive burners. As turbulent combustion simulation is rather an intricate task, it is helpful to study cold air flow inside the combustion chamber before igniting the chamber. In order to study the flow inside the mentioned test cases, different sub-grid scale models, i.e., constant Smagorinsky, dynamic Smagorinsky and dynamic WALE model are used to model the unresolved small scales. For the numerical simulations, a finite volume in-house code is used. The code adopts the projection method to solve the fluid flow equations. A second-order accurate scheme is used for spatial discretization. The time integration is done using a second-order accurate predictor-corrector scheme. For solving the resultant pressure Poisson equation, TDMA (Tridiagonal Matrix Algorithm) is used with multi-grid convergence acceleration. Generally, the results show good agreement with available experimental data. As expected, the dynamic WALE model performs better than the other models. To further improve the results, a rather realistic type of velocity inlet boundary conditions are applied to Sydney bluff body flow, i.e., digital filter velocity inflow boundary conditions. The results show drastic improvement using digital filter inflow, which is mainly due to the turbulent nature of the flow field.
Heat and Mass Transfer
T. Sudhakar Reddy; M. C. Raju; S. V. K. Varm
Abstract
In the present paper, an analysis was carried out to investigate effects of radiation on a free convection flow bounded by a vertical surface embedded in a porous medium with constant suction velocity. It was under the influence of uniform magnetic field in the presence of a homogenous chemical reaction ...
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In the present paper, an analysis was carried out to investigate effects of radiation on a free convection flow bounded by a vertical surface embedded in a porous medium with constant suction velocity. It was under the influence of uniform magnetic field in the presence of a homogenous chemical reaction and viscous dissipation with constant heat and mass flux. The non-dimensional governing equations were solved analytically and the expressions were found for velocity, temperature and concentration fields. Also, the expression for skin friction near the plate was derived and the results were discussed in a table.
Hydraulic and Pneumatic Systems
Lokesh Kumar; Nimai Pada Mandal
Abstract
This study focuses on the flow and pressure fluctuations of a fixed displacement radial piston pump with a valve plate with silencing grooves, and the effect of the number of pistons (5, 6, and 7) is investigated. Over the manifolds of the pump, valve plate silencing grooves are regarded as Top Dead ...
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This study focuses on the flow and pressure fluctuations of a fixed displacement radial piston pump with a valve plate with silencing grooves, and the effect of the number of pistons (5, 6, and 7) is investigated. Over the manifolds of the pump, valve plate silencing grooves are regarded as Top Dead Center and Bottom Dead Center. The mathematical modeling is run in MATLAB Simulink. Analyzing the flow characteristics and volumetric efficiency of the pump with and without silencing groove valve plate configuration of the pump is done. The opening and closing area pattern of the kidney port is also analyzed. The percentage reduction of flow and pressure fluctuation with the silencing groove is 19% and 16.16%, respectively, for Z = 7, as compared to the model without silencing groove valve plate. The volumetric efficiency of the model with silencing groove valve plate is improved from 1% to 2% as compared to the model without silencing groove valve plate. The lower the flow and pressure fluctuation coefficients, the higher the flow rate and volumetric efficiency of the pump for the model with silencing groove valve plate.
Plasticity
Sadjad Pirmohammad; Sobhan Esmaeili-Marzdashti; Arameh Eyvazian
Abstract
In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular ...
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In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular shape. In the first step, finite element simulations performed in LS-DYNA were validated by comparing with experimental data. The code generated in LS-DYNA was then used to investigate energy absorption behavior of the tapered structures. Response surface methodology and historical data design technique were employed to optimize the cross section perimeter (tapered angle) of the tapered structures by considering two conflicting crashworthiness criteria including EA (energy absorption) and PCF (peak crushing force). The optimization results showed that the optimal tapered angle enhanced by increasing the number of cross section sides (or number of corners). Then, the optimized tapered structures with different cross-sections were compared with each other using a ranking method called TOPSIS to introduce the most efficient energy absorber. The decagonal structure was finally found to be the best energy absorber.
Internal Combustion Engine
Ali Shaafi; Mohammad Javad Noroozi; Vahid Manshaei
Abstract
In this computational research, the separate and simultaneous impacts of diesel direct injection timing, fuel spraying cone angle, and hydrogen gas addition on combustion characteristics, output emissions, and performance in a single-cylinder direct injection diesel engine was studied. In order to conduct ...
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In this computational research, the separate and simultaneous impacts of diesel direct injection timing, fuel spraying cone angle, and hydrogen gas addition on combustion characteristics, output emissions, and performance in a single-cylinder direct injection diesel engine was studied. In order to conduct the simulations, valid and reliable models for combustion, break-up, and for turbulence was used. The effects of fifteen fuel injection strategies based on characteristics such as time of fuel spraying (-15, -10 CA BTDC, and TDC) and nozzle cone angle (105, 115, 125, 145, and 160 degrees) under neat diesel combustion and diesel-hydrogen combustion engine operations conditions were explored. The obtained results indicated that the addition of H2 due to significant heating value has increased indicated power and improved indicated specific energy consumption at the expense of NOx emissions but considerably decreased CO and soot emissions simultaneously. By advancing injection timing, maximum pressure peak point, maximum temperature peak point, and maximum heat release rate peak point have increased and caused lower indicated specific energy consumption. However, using a wide spray angle (e.g., 160 cone degrees), resulted in lower indicated power and higher indicated specific energy consumption due to more fuel could spray in regions with lower oxygen concentrations compared to baseline operation case.
Heat and Mass Transfer
Mohammad Riahi; Mohamad Hoseinpour Gollo; Seiied Nader Ameli Kalkhoran
Abstract
Laser forming is a modern process which is mainly used for forming metals. Different Lasers are used in this regard that includes Nd: YAG and CO2. In this study, forming bi-layer sheets of Aluminum/Ceramic by Laser was investigated. Furthermore, effect of Uniform and Gaussian heat flux distribution in ...
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Laser forming is a modern process which is mainly used for forming metals. Different Lasers are used in this regard that includes Nd: YAG and CO2. In this study, forming bi-layer sheets of Aluminum/Ceramic by Laser was investigated. Furthermore, effect of Uniform and Gaussian heat flux distribution in different power, velocity, and beam diameters on bending angle was studied. FEM simulation indicated that, in the same conditions of analysis, Uniform heat flux distribution caused higher bending angle than Gaussian heat flux distribution. Moreover, the results showed that there was an optimum point at different speeds and laser beam diameters, at which the bending angle was maximum. In order to evaluating the numerical results, a set of experiments was conducted, which showed good agreement.
Fluid Mechanics
Gh. Payganeh; A. Hadidi; M. Hallaji; N. Garjasi
Abstract
Over the last ten years, robustness of schemes has raised an increasing interest among the CFD community. The objective of this article is to solve the quasi-one-dimensional compressible flow inside a “Shubin nozzle” and to investigate Bean-Warming and flux vector splitting methods for numerical ...
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Over the last ten years, robustness of schemes has raised an increasing interest among the CFD community. The objective of this article is to solve the quasi-one-dimensional compressible flow inside a “Shubin nozzle” and to investigate Bean-Warming and flux vector splitting methods for numerical solution of compressible flows. Two different conditions have been considered: first, there is a supersonic flow in the entry and a supersonic flow in the outlet, without any shock in the nozzle. Second, there is a supersonic flow in the inlet and a subsonic flow in the outlet of the nozzle and a shock occur inside the nozzle. The results show that the run time of the flux vector splitting scheme is more than the Bean-Warming scheme, and, the flux vector splitting scheme is more accurate than the Bean-Warming scheme. However the flux vector splitting scheme is more complicated.
Forming
Hashem Zamanian; Mehdi Bostan Shirin; Ahmad Assempour
Abstract
In this work, an inverse finite element formulation was modified for considering material anisotropy in obtaining blank shape and forming severity of deep drawn orthotropic parts. In this procedure, geometry of final part and thickness of initial blank sheet were known. After applying ideal forming formulations ...
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In this work, an inverse finite element formulation was modified for considering material anisotropy in obtaining blank shape and forming severity of deep drawn orthotropic parts. In this procedure, geometry of final part and thickness of initial blank sheet were known. After applying ideal forming formulations between material points of initial blank and final shape, an equation system was obtained in terms of unknown initial positions on the blank sheet. Initial positions of material points were obtained by solving this equation system. In this algorithm, the Hill's anisotropic plasticity and associated plastic flow rule were used. Strain distribution on the final part was obtained by comparing the initial blank and final part. The method was applied for the simulation of drawing an orthotropic blank to a rectangular cup. Accuracy of the presented method was evaluated by comparing the results with numerical forward method and experiment results.
Heat and Mass Transfer
M. Rahimi; M. Khalafi-Salout
Abstract
Heat transfer from the internal surfaces of a vertical pipe to the adjacent air gives rise to the air flow establishment within the pipe. With the aim of optimizing the convective air flow rate in a vertical pipe, the details of the flow and thermal fields were investigated in the present study. Conservation ...
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Heat transfer from the internal surfaces of a vertical pipe to the adjacent air gives rise to the air flow establishment within the pipe. With the aim of optimizing the convective air flow rate in a vertical pipe, the details of the flow and thermal fields were investigated in the present study. Conservation equations of mass, momentum, and energy were solved numerically using simple implicit forward-marching finite difference scheme for a two-dimensional axis-symmetric flow. In order to evaluate and optimize the air flow rate passing through the pipe, the position and intensity of the wall heat flux were altered when the total employed heat transfer rate was constant. Based on the results of the numerical analysis, relatively more air flow rate was achieved when more intensified heat flux was employed at the lowest part of the vertical pipe. This finding was then validated using a simple experimental setup. The results of the present study could be useful in the design and application of buoyancy-assisted natural ventilation systems.
Turbulance
S. F. Ahmed; M. S. A. Sarker Sarker
Abstract
The energy equation for turbulent flow of fiber suspensions was derived in terms of second order correlation tensors. Fiber motion of turbulent energy including the correlation between pressure fluctuations and velocity fluctuations was discussed at two points of flow field, at which the correlation ...
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The energy equation for turbulent flow of fiber suspensions was derived in terms of second order correlation tensors. Fiber motion of turbulent energy including the correlation between pressure fluctuations and velocity fluctuations was discussed at two points of flow field, at which the correlation tensors were the functions of space coordinates, distance between two points, and time.
Automation
Pardeep kumar Rohilla; Feras Hakkak; Vineet Kumar
Abstract
Inherent nonlinearities like, deadband, stiction and hysteresis in control valves degenerate plant performance. Valve stiction standouts as a more widely recognized reason for poor execution in control loops. Measurement of valve stiction is essential to maintain scheduling. For industrial scenarios, ...
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Inherent nonlinearities like, deadband, stiction and hysteresis in control valves degenerate plant performance. Valve stiction standouts as a more widely recognized reason for poor execution in control loops. Measurement of valve stiction is essential to maintain scheduling. For industrial scenarios, loss of execution due to nonlinearity in control valves is an imperative issue that should be tackled. Thus, an intelligent technique is required for automated execution, observation and enhancement. The paper shows the creative utilization of an intelligent controller for nonlinearity diagnosis in control valves. This is a Fuzzy Gain Scheduling (FGS) PID smart controller that tunes its gain parameters in real time to manage a control valve’s inherent nonlinearity. The viability of the FGS PID controller is experimentally verified in a laboratory scale plant. An execution comparison between FGS PID and classical PID controllers are undertaken for their set point following and disturbance rejection at different operating points. Experimental results show that the FGS PID controller outperforms the classical PID controller for all explored cases effectively managing stiction based oscillation in the controller output.
Computational Fluid Dynamics (CFD)
Vikram Ashok Kolhe; Vishal D Chaudhari; Suyash Yashwant Pawar; Ravindra L Edlabadkar; Kailas Chandratre
Abstract
Measuring flow rate precisely in laminar flow has been a difficult task, especially when utilizing a Coriolis mass flow meter (CMFM) for low flow rate measurements. The meter often under reads the mass flow rate, making it less useful in these conditions. The dominant factor affecting the CMFM's performance ...
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Measuring flow rate precisely in laminar flow has been a difficult task, especially when utilizing a Coriolis mass flow meter (CMFM) for low flow rate measurements. The meter often under reads the mass flow rate, making it less useful in these conditions. The dominant factor affecting the CMFM's performance in laminar regions is secondary flow, which overshadows the generated Coriolis force, leading to an under-reading of flow rate. Previous studies have indicated that tube curvature is the most significant parameter affecting secondary flow generation and the overall performance of the meter. An omega-shaped tube configuration featuring a continuous curvature has been identified as the optimal shape for maximizing a CMFM device’s performance in laminar flow. The purpose of the investigation is to study and compare the efficiency of various Omega tube designs that have undergone slight geometric alterations. Four different configurations were evaluated for maximum time lag by vibrating at their respective natural frequencies and keeping the sensor position along the centerline of the tube configuration.
