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 A. Kolhe; Suyash Y. Pawar; Vishal D. Chaudhari; Ravindra L. Edlabadkar; Kailas V. 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 ...
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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 the 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 the performance of a CMFM device 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.
Welding
Saadat Ali Rizvi; S P Tewari
Abstract
This study investigated the optimization of three welding parameters (wire feed speed, arc voltage, and shielding gas flow rate) for SS 304H by using Taguchi based Grey relational analysis. In this research work, pure argon was used as shielding gas. Numbers of trials were performed as per ...
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This study investigated the optimization of three welding parameters (wire feed speed, arc voltage, and shielding gas flow rate) for SS 304H by using Taguchi based Grey relational analysis. In this research work, pure argon was used as shielding gas. Numbers of trials were performed as per L16 (4xx3) orthogonal array design and the mechanical quality such ultimate tensile strength, microhardness, Toughness, and microstructure of SS304H optimized by Grey-based Taguchi analysis and result shows that the optimal parameters combination were as A4B4C3 i.e. flow rate at 23L/min, voltage at 25 V and welding speed at 350IPM and it was observed that wire feed speed had the most significant effect followed by voltage and gas flow rate. An optimal combined parameter of the welding operation was obtained via Grey relational analysis. By analyzing Grey relational grade matrix, the degree of influence for each controllable process factor onto individual quality targets can be found.
Forming
A. H. Rabiee; E. Sherkatghanad; A. Zeinolabedin Beygi; H. Moslemi Naeini; L. Lang
Abstract
In this paper, by considering the processing parameters, including blank holder force, blank holder gap, and cavity pressure as the most important input factors in the hydroforming process, an experimental design is performed, and an adaptive neural-fuzzy inference system (ANFIS) is applied to model ...
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In this paper, by considering the processing parameters, including blank holder force, blank holder gap, and cavity pressure as the most important input factors in the hydroforming process, an experimental design is performed, and an adaptive neural-fuzzy inference system (ANFIS) is applied to model and predict the behavior of aluminum thinning rate (upper layer and lower layer), the height of wrinkles and achieved depths that are extracted in hydroforming process. Also, the optimal constraints of the network structure are obtained by the gray wolf optimization algorithm. Accordingly, the results of experimental tests are utilized for training and testing of the ANFIS. The accurateness of the attained network is examined using graphs and also based on the statistical criteria of root mean square error, mean absolute error, and correlation coefficient. The results show that the attained model is very effective in approximating the aluminum thinning rate (upper layer and lower layer), the height of wrinkles, and achieved depth in the hydroforming process. Finally, the results also show that the root means of the square error of aluminum thinning rate (upper layer and lower layer), the height of wrinkles, and achieved depth of the test section are 1.67, 2.25, 0.05, and 2.67, respectively. It is also observed that the correlation coefficient for the test data is very close to 1, which demonstrates the high precision of the ANFIS in predicting the outputs of the hydroforming procedure.
Energy Science and Technology
I. Vinothkanna; K. Subramani; A. Devaraj
Abstract
The petroleum product has seen a drastic demand in the recent past. Biofuels are the only solution to overcome this power crisis. In the view of sustainable energy development, biodiesel and its additives have become the best options for fossil fuel-based engines. In this work, a biodiesel mix was used ...
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The petroleum product has seen a drastic demand in the recent past. Biofuels are the only solution to overcome this power crisis. In the view of sustainable energy development, biodiesel and its additives have become the best options for fossil fuel-based engines. In this work, a biodiesel mix was used to show the possible utilization of different biofuels. An experimental investigation was carried out on a direct-injection constant-speed (Rated speed- 1500 rpm) diesel engine at different injection pressures of 180, 220 and 260 bar with natural aspiration and supercharging modes. The blends of Biodiesel (used cooking oil, with a mix of algae) and diesel fuels are the selected fuel to investigate. At lower injection pressures, brake specific fuel consumption of the engine was low and further lowered with supercharging operation. With the reduction of injection pressures, brake thermal efficiency values are improved, and the same was observed with supercharging. With the rise in injection pressures, NOx emissions increased due to rise in temperature, and unburnt hydrocarbon emissions were slightly increased. The algae biodiesel was used as an additive to increase the stability of biodiesel. The overall observation indicates that a moderate injection pressure of 220 bar is advisable.
Nonlinear Solution
Adnan Maqsood; Muhammad Kamran Khan Tareen; Rizwan Riaz; Laurent Dala
Abstract
The paper discusses the effect of compressor characteristic on surge phenomena in axial flow compressors. Specifically, the effect of nonlinearities on the compressor dynamics is analyzed. For this purpose, generalized multiple time scales method is used to parameterize equations in amplitude and frequency ...
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The paper discusses the effect of compressor characteristic on surge phenomena in axial flow compressors. Specifically, the effect of nonlinearities on the compressor dynamics is analyzed. For this purpose, generalized multiple time scales method is used to parameterize equations in amplitude and frequency explicitly. The pure surge case of the famous Moore-Greitzer model is used as the basis of the study. The compressor characteristic used in the Moore-Greitzer model is generalized to evaluate the effect of the parameters involved. Subsequently, bifurcation theory is used to study the effect of nonlinear dynamics on surge behavior. It has been found that the system exhibits supercritical Hopf bifurcation under specific conditions in which surge manifests as limit cycle oscillations. Key parameters have been identified in the analytical solution which govern the nonlinear dynamic behavior and are responsible for the existence of limit cycle oscillations. Numerical simulations of the Moore-Greitzer model are carried out and found to be in good agreement with the analytical solution
Heat and Mass Transfer
B. Malleswari; T. Poornima; P. Sreenivasulu; N. Bhaskar Reddy
Abstract
This study emphasizes the upshots of non-linear radiation and electrical resistance heating on a three dimensional Jeffrey dissipating nanoflow in view of convective surface conditions. The initial set of nonlinear dimensional boundary layer equations are transformed into a system of ordinary differential ...
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This study emphasizes the upshots of non-linear radiation and electrical resistance heating on a three dimensional Jeffrey dissipating nanoflow in view of convective surface conditions. The initial set of nonlinear dimensional boundary layer equations are transformed into a system of ordinary differential equations with suitable similarity variables and then solved by shooting method using Mathematica software. For various representative quantities, the behavior of the momentum, energy and species diffusion along with engineering quantities near the surface are figured for different estimations of the fluid properties. The examination of the present outcomes has been made with the existing work which is in good agreement. This study helps in understanding that the heat transfer rate is predominant in the non-linear radiation compared to linear radiation. Jeffrey fluid model has the capacity of describing the stress relaxation property, that usually viscous fluid lags and this is exhibited clearly in the study. Shear stress descends as the fluid pertinent parameter ascends.
Forming
S. Izadpanah; S. H. Ghaderi; M. Gerdooei
Abstract
This paper investigates the earing phenomenon in deep drawing of AA3105 aluminum alloy, experimentally and numerically. Earing defect is mainly attributed to the plastic anisotropy of sheet metal. In order to control such defect, predicting the evolution of ears in sheet metal forming analyses becomes ...
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This paper investigates the earing phenomenon in deep drawing of AA3105 aluminum alloy, experimentally and numerically. Earing defect is mainly attributed to the plastic anisotropy of sheet metal. In order to control such defect, predicting the evolution of ears in sheet metal forming analyses becomes indispensable. In this regard, the present study implements the advanced yield criterion BBC2003. Based on this yield function and the associated flow rule of plasticity, the constitutive model is derived. Accordingly, a user material VUMAT subroutine is developed and adopted in the commercial finite element software ABAQUS/Explicit. Several plane stress loading problems are designed, through which, the accuracy of the developed subroutine is verified. In addition, cylindrical cups of AA3105 aluminum alloy are fabricated using a deep drawing die. The earing defect was clearly observed on the recovered parts. Using the experimentally obtained constants of BBC2003 yield criterion for this alloy in VUMAT, deep drawing of the cylindrical cups was simulated. The results demonstrate that the earing profile can successfully be predicted using BBC2003 yield function.
Fluid Mechanics
Abolfazl Khalkhali*; Hamed Safikhani
Abstract
In this paper, lift and drag coefficients were numerically investigated using NUMECA software in a set of 4-digit NACA airfoils. Two metamodels based on the evolved group method of data handling (GMDH) type neural networks were then obtained for modeling both lift coefficient (CL) and drag coefficient ...
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In this paper, lift and drag coefficients were numerically investigated using NUMECA software in a set of 4-digit NACA airfoils. Two metamodels based on the evolved group method of data handling (GMDH) type neural networks were then obtained for modeling both lift coefficient (CL) and drag coefficient (CD) with respect to the geometrical design parameters. After using such obtained polynomial neural networks, modified non-dominated sorting genetic algorithm (NSGAII) was used for Pareto based optimization of 4-digit NACA airfoils considering two conflicting objectives such as (CL) and (CD). Further evaluations of the design points in the obtained Pareto fronts using the NUMECA software showed the effectiveness of such an approach. Moreover, it was shown that some interesting and important relationships as the useful optimal design principles involved in the performance of the airfoils can be discovered by the Pareto-based multi-objective optimization of the obtained polynomial meta-models. Such important optimal principles would not have been obtained without using the approach presented in this paper.
Control
Seyed Vahab Shojaedini; Armin Parsiannejad
Abstract
This paper describes a new method for harvesting maximum electrical energy in wind farms. In proposing technique, the stochastic process principles are applied for detecting fault measurements of sensors. On the other hand, the wind farm is modeled by using fuzzy concept. Thereby the turbines are controlled ...
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This paper describes a new method for harvesting maximum electrical energy in wind farms. In proposing technique, the stochastic process principles are applied for detecting fault measurements of sensors. On the other hand, the wind farm is modeled by using fuzzy concept. Thereby the turbines are controlled against continuous changes in speed, direction and eddy currents of the blowing wind. To evaluate the performance of the proposed method three practical conditions of wind blowing are simulated. In the first scenario, the normal wind is simulated with low turbulence and slow changes. The second scenario belongs to high turbulence winds with sudden shifts in their parameters, and finally in the most complex scenario, several eddy currents are considered in blowing winds too. The obtained results show that the proposed method provides greater and more uniform harvested power compared to alternative methods. Furthermore, its superiority against other techniques has increased in parallel with the scenario become more complicated.
Robotics
Abstract
This paper shows the coordinates influence on singularity of a three degree-of-freedom structure, namely, three-Universal-Prismatic-Spherical (3-UPS) parallel manipulator. Rotational coordinates, which are chosen to define the orientation of the platform, affect the singularity of the manipulator. Euler ...
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This paper shows the coordinates influence on singularity of a three degree-of-freedom structure, namely, three-Universal-Prismatic-Spherical (3-UPS) parallel manipulator. Rotational coordinates, which are chosen to define the orientation of the platform, affect the singularity of the manipulator. Euler parameters, which don't have any inherent geometrical singularity are utilized, however they are dependent coordinates. This paper shows the advantage of Euler parameters rather than Euler angles as the rotational coordinates for the manipulator. Additionally, the real loci of singularity for the manipulator due to its structure are predicted.
Vibration
Seyed javid Zakavi; Behzad Shiralivand; Mohammad nourbakhsh
Abstract
In this paper the ratcheting behavior of carbon steel(ASTM A106B) and stainless steel(304L) elbows is studied under steady internal pressure and in-plane external moments at frequencies typical of seismic excitations. The finite element analysis with the nonlinear isotropic/kinematic (combined) hardening ...
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In this paper the ratcheting behavior of carbon steel(ASTM A106B) and stainless steel(304L) elbows is studied under steady internal pressure and in-plane external moments at frequencies typical of seismic excitations. The finite element analysis with the nonlinear isotropic/kinematic (combined) hardening model has been used to evaluate ratcheting behavior of the elbows. Material parameters have been obtained from several stabilized cycles of specimens that are subjected to symmetric strain cycles. The rate of ratcheting depends significantly on the magnitudes of the internal pressure, dynamic bending moment and material constants for combined hardening model. The results show that the maximum ratcheting is occurred in the hoop direction at crown. Also, the results show that initially, the calculated rate of ratcheting is large and then decreases with the increasing of cycles. Also, the results obtained by using the Combined hardening model gives acceptable adaptation in comparison with the other hardening models(AF and Chaboche hardening models); however this model gives over estimated values comparing with the experimental data.
Vibration
N. Mellel; M. Ouali; M. Dougdag; B. Mohammedi
Abstract
This paper presents an extended cross modal strain energy change method to estimate the severity of damage associated with limited modal data in beam-like structures. This method takes in account the correlation between the analytical modal data and the measured incomplete modal data. A procedure ...
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This paper presents an extended cross modal strain energy change method to estimate the severity of damage associated with limited modal data in beam-like structures. This method takes in account the correlation between the analytical modal data and the measured incomplete modal data. A procedure was proposed and the analytical elemental stiffness of the damaged element after it is localized is included in quantification of the measured single damage extent. A three-dimensional numerical beam model with different damage cases is used to simulate the CMSE method application and to getting the bending displacements of the damaged element. An experimental modal analysis (EMA) on a cantilever beam with and without crack was carried out to evaluate the effectiveness of the extended CMSE method. The severity magnitude of the damage was predicted within an acceptable error range through the using validation process. Results reveal that the proposed damage estimation method successfully evaluates single damage severity in beam like structure and can be useful in maintenance technology and structural health monitoring system.
Nonlinear Solution
M. Matinfar; M. Ghasemi
Abstract
Variational Iteration method using He's polynomials can be used to construct solitary solution and compacton-like solution for nonlinear dispersive equatioons. The chosen initial solution can be determined in compacton-like form or in solitary form with some compacton-like or solitary forms with ...
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Variational Iteration method using He's polynomials can be used to construct solitary solution and compacton-like solution for nonlinear dispersive equatioons. The chosen initial solution can be determined in compacton-like form or in solitary form with some compacton-like or solitary forms with some unknown parameters, which can be determined in the solution procedure. The compacton-like solution and solitary solution can be converted into each other.
Thermodynamics and Cumbustion
A. A. Mirmohammadi; F. Ommi
Abstract
The purpose of this paper is to studying nonlinear k-ε turbulence models and its advantages in internal combustion engines, since the standard k-ε model is incapable of representing the anisotropy of turbulence intensities and fails to express the Reynolds stresses adequately in rotating ...
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The purpose of this paper is to studying nonlinear k-ε turbulence models and its advantages in internal combustion engines, since the standard k-ε model is incapable of representing the anisotropy of turbulence intensities and fails to express the Reynolds stresses adequately in rotating flows. Therefore, this model is not only incapable of expressing the anisotropy of turbulence in an engine cylinder, but also is unable to provide good performance when computing the swirling and tumbling flows is important in engine cylinders. Thus, in this paper, the results of nonlinear k-ε model are compared with those of the linear one. Results of diesel engine simulation with linear and nonlinear k-ε models in comparison show that turbulence intensity in the nonlinear model simulation is higher than that of the linear model; also, nonlinear k-ε models predict the second peak value because of the bowl shape in expansion stroke for turbulence intensity. Gas injection results show that nonlinear turbulence models predict spray penetration accurately because of correctly turbulence intensities predicting. Also, the results demonstrate that, for high pressure gas injection, turbulence intensity is high and predicted accurately using nonlinear models. Then, its spray penetration length is predicted accurately in comparison to experimental data’s. Although CPU time spending in the nonlinear model is more than that of the linear one, the non-linear stress model is found to increase computation time by 19%.
Aerodynamics
Sarallah Abbasi; Marhamat zienali
Abstract
Characteristics of rotor blade tip clearance flow in axial compressors can significantly affect their performance and stable operation. It may also increase blade vibrations and cause detrimental noises. Therefore, this paper is contributed to investigate tip leakage flow in a low speed isolated axial ...
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Characteristics of rotor blade tip clearance flow in axial compressors can significantly affect their performance and stable operation. It may also increase blade vibrations and cause detrimental noises. Therefore, this paper is contributed to investigate tip leakage flow in a low speed isolated axial compressor rotor blades row. Simulations are carried out on near-stall condition, which is valuable of being studied in detail. In turbomachines, flows are non-isotropic and highly three-dimensional. The reason arises from the complicated structure of bounded walls, tip leakage flows, secondary flows, swirl effects, streamlines curvatures and pressure gradients along different directions. As a result, accurate studies on tip leakage flow would be accompanied by many challenges such as adopting suitable turbulence models. So, investigations are carried out numerically utilizing two well-known turbulence models of k-ε and k-ω-SST, separately. It is shown that the k-ε model yields poor results in comparison to the k-ω-SST model. To realize reasons for this discrepancy, turbulence parameters such as turbulent kinetic energy, dissipation and eddy viscosity terms at the tip clearance region were surveyed in detail. It is found out that estimation for eddy viscosity term is too high in the k-ε model due to excessive growth of turbulent kinetic energy, time scale, and lack of effective damping coefficient. This leads to dissipation of vortical structure of flow and wrong estimation of flow field at the rotor tip clearance region. Nevertheless, k-ω-SST turbulence model provides results consistent with reality.
Heat and Mass Transfer
M. Nasiri; B. Ghasemi
Abstract
This paper modeled heating air of a room through examining free convection in a 3D chamber. The chamber had cold and hot sources with Tc and Th temperatures, respectively. Its other walls were adiabatic. This study aimed at predicting effect of temperature difference, displacement of hot and cold sources ...
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This paper modeled heating air of a room through examining free convection in a 3D chamber. The chamber had cold and hot sources with Tc and Th temperatures, respectively. Its other walls were adiabatic. This study aimed at predicting effect of temperature difference, displacement of hot and cold sources and their aspect ratio on flow field, temperature and heat transfer rate. To conduct the study, mass conservation, momentum and energy equations were applied in laminar and 3D states while assuming fluid constant properties, except density, in the power of buoyancy (Boussinesq approximation). Final difference method (FDM) was used for numerical solution of the governing equations based on the volume control and SIMPLE algorithm. According to the modeling results, the most favorable temperature distribution in the chamber (room) was obtained when the heat source (radiator) was located on the wall under the cold source (window). Reducing the distance between the two sources would result in increasing heat transfer from the heating sources.
Nhu-Tung Nguyen; Dong Van Pham; Cuong Duc Pham; Dung Hoang Tien
Abstract
Cutting force coefficients (CFCs) are the most important factors in the prediction of CFs (CFs) and other machining characteristics (MCs). This study was conducted to model the CFs and MCs in the milling process based on the calculated values of CFCs. From the relationship of average values of CFs and ...
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Cutting force coefficients (CFCs) are the most important factors in the prediction of CFs (CFs) and other machining characteristics (MCs). This study was conducted to model the CFs and MCs in the milling process based on the calculated values of CFCs. From the relationship of average values of CFs and feed rate, CFCs were determined and used to predict dynamic CFs (DCFs) in the flat milling process. In static models, the average values of CFs were presented as a linear regression of feed rate. The DCFs and other MCs were modeled depending on the cutting parameters, cutter geometry, CFCs, and structure parameters of the machine-tool system. By performing the flat-milling process of gray cast iron GG25 using HSS-Co solid tool, the average CFs were modeled as the linear regression of feed rate with large determination coefficients (R2 > 93%). Besides, all CFCs of a pairs of tool and workpiece for each cutting type were successfully determined based on the measured data of CFs from the experimental process. Moreover, the proposed models of DCFs were successfully verified based on the compared results between the predicted CFs and measured CFs in several cutting tests with different cutting parameters. The proposed models of cutting force in this study were successfully used to predict the DCFs and several MCs in milling processes using a flat milling tool. And can be used to design and develop tools and machine in industrial manufacturing.
Heat and Mass Transfer
Seyed Mostafa Moafi Madani; Javad Alinejad; Yasser Rostamiyan; Keivan Fallah
Abstract
In the present study, the effect of the heating pipe profile on natural convection in a two-phase fluid inside a cavity has been investigated. This geometry has been simulated with the LB Method based on the D2Q9 model for analyzing stream lines, dimensionless velocity field of fluid flow, solid particles ...
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In the present study, the effect of the heating pipe profile on natural convection in a two-phase fluid inside a cavity has been investigated. This geometry has been simulated with the LB Method based on the D2Q9 model for analyzing stream lines, dimensionless velocity field of fluid flow, solid particles volume fraction, temperature arrangement, and Nusselt number. These parameters have been studied in three different cases of the cavity. The results are signified by changing the geometry from a horizontal ellipse to a circular one and a vertical ellipse;the maximum particle volume fraction is decreased. Also, by changing the geometry from a horizontal ellipse to a circular and vertical ellipse, larger velocity vectors have been formed around the geometry. The Nusselt number variations of circular and vertical ellipse geometries are from 90⁰ to 270⁰. The Nusselt number variation of horizontal ellipse geometry is negligible from 90⁰ to 270⁰. Also, the Nusselt number of the circular geometry is larger than the other geometries from 270⁰ to 90⁰. The highest average Nusselt number belongs to circular, vertical and horizontal ellipse geometries, respectively.
Vibration
Mahesh Chandra Luintel; Tri Ratna Bajracharya
Abstract
The performance and reliability of any rotating machine can be studied by proper dynamic analysis of the machine. This paper presents a method to study the dynamic response of a Pelton turbine shaft due to the impact of a water jet. Equations of motion for the bending vibration of the Pelton turbine ...
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The performance and reliability of any rotating machine can be studied by proper dynamic analysis of the machine. This paper presents a method to study the dynamic response of a Pelton turbine shaft due to the impact of a water jet. Equations of motion for the bending vibration of the Pelton turbine assembly, in two transverse directions, are developed using the Lagrange equation of motion with the help of assumed mode’s method. The Pelton wheel is assumed as a rigid disk attached to an Euler-Bernoulli shaft. The impact provided by the water jet is represented in the form of a Fourier series. Critical speeds of the system are determined by performing free vibration analysis and presented in the form of the Campbell diagram. The response plots due to the impact of water are generated by performing forced response analysis. Both free and forced analyses are carried out by considering the first three modes of vibration.
Computational Fluid Dynamics (CFD)
Brahim Rostane; Aliane Khaled; Said Abboudi
Abstract
The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes ...
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The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes were used to solve the fluid dynamics equations .The finite volume method are employed to solve the governing equations using the ANSYS CFX code and the turbulence model k-ω SST. The streamwise velocity profiles, the Time-averaged streamlines, the turbulence kinetic energy and the drag coefficient are presented. The results showed the appearance of a second vortex behind obstacles with hole from diameter D/H=0.2. The turbulence kinetic energy was greater on top of the obstacle, it was more intense for the obstacle without hole, this intensity decreased as the hole diameter increased. The drag coefficient was improved only for the case D/H=0.32
Energy Science and Technology
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 a major impact on fuel-air mixing and combustion. In the current study, the geometry of the injector orifice is changed from ...
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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 a major impact on fuel-air mixing and combustion. In the current study, the 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 droplet distribution and breakup. At low injection pressures, due to the long injection duration, most of the fuel energy release occurs after the 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 the TDC. By changing the injector geometry to the injector with an 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%. The maximum power increase was 15% for a 2.5% fuel increase at an 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 was well oxidized before the end of the work phase, and its amount reached less than 2e-6.
Welding
Saman Khalilpourazary; Reza Abdi Behnagh; Ramezanali Mahdavinejad; Nasib Payam
Abstract
This study focused on the optimization of Al—Mg to CuZn34 friction stir lap welding (FSLW) process for optimal combination of rotational and traverse speeds in order to yield favorable fracture load using Grey relational analysis (GRA). First, the degree of freedom was calculated for the system. ...
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This study focused on the optimization of Al—Mg to CuZn34 friction stir lap welding (FSLW) process for optimal combination of rotational and traverse speeds in order to yield favorable fracture load using Grey relational analysis (GRA). First, the degree of freedom was calculated for the system. Then, the experiments based on the target values and number of considered levels, corresponding orthogonal array, Grey relational coefficient and Grey relational grade were performed. In the next step, Grey relational graph of each level was sketched. The performed graph and analysis of Grey results proved the impact of rotational speed and traverse speed on fracture load of resultant joints. Finally, the optimum amount of each parameter for better strength of the welds was obtained. This study showed feasibility of the application of Grey relational analysis for achieving dissimilar friction stir lap welds with the highest quality.
