Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Optimal distribution ofbraking and steering tire forces subject to stabilityconstraints
1709
1719
EN
Ali
Tavasoli
Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran 15914, Iran
tavasoli@aut.ac.ir
Mahyar
Naraghi
Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran 15914, Iran
naraghi@aut.ac.ir
This paper presents an integrated vehicle dynamics control which managesto coordinatesteering and braking subsystems using optimal distribution of tire forces (ODF). Specifically,we introduce an ODF scheme which treats thestandard stability conditions of the phase-plane as inequality constraints in the optimization problem. The established scheme works to fulfill the objectives of a higher-level controller as much as possible without violating vehicle dynamics stability conditions. A sliding mode enhanced adaptive high-level control assesses the desired total yaw moment and lateral force for the vehicle control. The proposed controller only requires the online adaptation of control gains without acquiring the knowledge of upper bounds on system uncertainties. An optimization problem incorporating six inequality constraints is solved analytically by Karush-Kuhn-Tucker (KKT) conditions. To coordinate braking and steering subsystems, a phase-plane based adaptation mechanism is suggestedto adjust the weighting coefficients in the considered cost function. The simulation cases show that the vehicle stability can be improved effectively by the suggested scheme
vehicle dynamics,adaptive sliding mode control,optimal tire force distribution,stability constraint
http://scientiairanica.sharif.edu/article_3413.html
http://scientiairanica.sharif.edu/article_3413_4fb9704290fd77b60746b75b6da0dcc6.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Thermodynamic Analysis of Performance of Vapour Compression Refrigeration System Working with R290 and R600a Mixtures
1720
1728
EN
B.O.
Bolaji
Department of Mechanical Engineering, Federal University of Agriculture, PMB 2240, Abeokuta, Nigeria
bolajibo@funaab.edu.ng
Z.
Huan
Department of Mechanical Engineering, Faculty of Engineering and Built Environment, Tshwane University of Technology, Pretoria, South Africa
huanz@tut.ac.za
Environmentally benign natural refrigerants have recently attracted a considerable attention due to refrigerant contributions to ozone depletion and global warming.In the groupof natural refrigerants, hydrocarbons are most closely related to the HFCs. In addition to their zero ODP and very low GWP, they are compatible with common materials found in refrigerating systems. Therefore, in this study, the performance simulation of R290 and R600a mixtures (80/20, 70/30, 60/40 and 50/50 proportion by mass, designated by RM1, RM2, RM3 and RM4, respectively) in vapour compression refrigeration system is conducted by thermodynamic calculation of performance parameters using REFPROP software. The results showed that the mixtures exhibited higher refrigerating effect than R134a. The average pressure ratio obtained for RM1, RM2, RM3 and RM4 were 19.5, 16.5, 14.0 and 11.8% lower than that of R134a, respectively. All the mixtures, except RM1, exhibited low discharge pressure which is more desirable in refrigeration systems. The COPs of the mixtures were close to that of R134a with advantage of higher values. Generally, the overall performance of the selected mixtures was better than that of R134a. The performance of RM4 was the best in terms of low compressor work and discharge pressure, and high COP at varying evaporating temperature.
Thermodynamic,alternative refrigerants,hydrocarbon mixtures,R290,R600a,R134a
http://scientiairanica.sharif.edu/article_3414.html
http://scientiairanica.sharif.edu/article_3414_c1eae7aa36819a87ebcf8b46c6857da1.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Multidimensional Modeling of CNG Direct Injection and Mixture Preparation in a SI Engine Cylinder
1729
1741
EN
B.
Yadollahi
Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
byadollahi@aut.ac.ir
M.
Boroomand
Amirkabir University of Technology (Tehran polytechnic), Tehran, Iran
boromand@aut.ac.ir
In this study, a numerical model has been developed in AVL FIRE software to perform investigation of direct natural gas injection into the cylinder of spark ignition internal combustion engines. Two main parts have been taken into consideration, aiming to convert an MPFI gasoline engine to direct injection NG engine. In the first part multi-dimensional numerical simulation of transient injection process, mixing and flow field have been performed via different validation cases in order to assure the numerical model validity of results. In all cases, present results were found to have excellent agreement with experimental and numerical results from literature.
In the second part the validated model has been applied to methane Injection into the cylinder of a direct injection engine. Five different piston head shapes have been taken into consideration and a centrally mounted inwardly-opening single-hole injector has been adapted to all cases. The effects of injection and combustion chamber geometry have been studied on mixing of air-fuel inside cylinder via quantitative and qualitative representation of results. Furthermore the effect of real engine cylinder head shape on the gas injection has been investigated. Based on the results, suitable geometrical configuration for a NG DI engine has been discussed.
CNG direct injection,Spark ignition,Mixture preparation,DISI,High pressure injection,cylinder head shape,Multidimensional modeling,numerical simulation
http://scientiairanica.sharif.edu/article_3415.html
http://scientiairanica.sharif.edu/article_3415_4d79e15e2b771a3812e473f848f8c9dc.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Kinematic Control of a New Hyper-Redundant Manipulator with Lockable Joints
1742
1752
EN
Ali
Taherifar
Center of Excellence in Design, Robotics and Automation (CEDRA), Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, Tehran, Postal code: 1458889694, Iran
taherifar@mech.sharif.ir
Hassan
Salarieh
Center of Excellence in Design, Robotics and Automation (CEDRA), Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, Tehran, Postal code: 1458889694, Iran
salarieh@sharif.edu
Aria
Alasty
Center of Excellence in Design, Robotics and Automation (CEDRA), Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, Tehran, Postal code: 1458889694, Iran
aalasty@sharif.edu
Kinematic control of a special hyper-redundant manipulator with lockable joints is studied. In this manipulator, the extra cables are replaced by a locking system to reduce the weight of the structure and the number of actuators. This manipulator has discrete and continuous variables due to its locking system. Therefore, a hybrid approach has been adopted in control. At first the forward kinematics and velocity kinematics of this manipulator is derived, and then a novel closed-loop control algorithm is presented. This algorithm consists of decision making, inner loop controller, andkinematic calculation blocks. The decision making block is the logical part of the control scheme in which suitable switches will be chosen. The control block usestheend-effector position feedback to generate appropriate commands. The performance of the proposed hybrid control scheme in position tracking is assessed for several trajectories.
Redundant Manipulator,Kinematic Control,Lockable Joints,Tendon-Actuated Manipulator
http://scientiairanica.sharif.edu/article_3416.html
http://scientiairanica.sharif.edu/article_3416_9d6e41ada1ff382d83f10c67a6be1d22.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Experimental and Numerical Investigation of Radial Flow Compressor Volute Shape effects in Characteristics and Circumferential Pressure Non-uniformity
1753
1764
EN
Mohammad
Mojaddam
Mechanical Engineering Department, Sharif University of Technology, Tehran, P.O. Box 11155-9567, Iran
Ali
Hajilouy-Benisi
Center of Excellence for Energy Conversion,Sharif University of Technology, Tehran,P.O. Box 11155-9567, Iran
hajilouy@sharif.edu
Mohammad Reza
Movahhedy
Mechanical Engineering Department, Sharif University of Technology, Tehran, P.O. Box 11155-9567, Iran
In this article, the effects of volute cross section shape and centroid profile of a radial flow compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and flow parameters at the inlet and outlet of the compressor. The three-dimensional flow field model of the compressor was obtained numerically solving Navier-Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement.
Modification of a volute was performed by introducing a shape factor for volute cross section geometry. By varying this parameter, new external volutes were generated and modeled while the original volute was intermediate volute. The effect of volute cross section shape on compressor pressure ratio and isentropic efficiency at design rotational speed were investigated.
Also pressure non-uniformity around compressor impeller was investigated using pressure taps around the impeller outlet to verify numerical results. This effect was considered and reported for new cases using numerical results.
The results show how the shape and centroid profile of volute circumferential cross sections can influence the compressor characteristics and circumferential static pressure non-uniformity.
Radial flow compressor,Turbocharger,Volute,Performance characteristic,Pressure non-uniformity
http://scientiairanica.sharif.edu/article_3417.html
http://scientiairanica.sharif.edu/article_3417_addd203e266d7d7d0a925d538a1fac2e.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
SOME OPERATORS ACTING ON WEIGHTED SEQUENCE SPACES AND APPLICATIONS
1765
1772
EN
CARLOS
LIZAMA
Departamento de Matematica y Ciencia de la Computacion, Facultad de Ciencias, Universidad de Santiago de Chile, Casilla 307-Correo2, Santiago, Chile
carlos.lizama@usach.cl
This paper considers the problem of constructing an evolution family for
the linear non autonomous Cauchy problem
()
@
@t
u(t) ???? A(t)u(t) = 0; u(????1) = x 2 RN;
where A 2 C([????1; 1];RNN): The essence of the method is that the evolution family is
sought in the form of a series of Chebyshev polynomials. Then, by de ning appropriate
weighted sequence spaces and matrices of linear operators, we are able to obtain a suf-
cient condition - based only in the given data - for the representation of the solution
of the initial value problem (). The method is motivated for practical considerations in
the context of Magnetic Resonance Imaging.
Weighted sequence spaces,Chebyshev polynomials,non autonomous Cauchy problem,Operator theory,Bloch equation,Magnetic resonance imaging
http://scientiairanica.sharif.edu/article_3418.html
http://scientiairanica.sharif.edu/article_3418_7813bde404e86370d150b9de6bbe5e64.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
EFFECTS OF WELDING OPERATING FACTOR ON SHIPYARD PANEL LINE’S PRODUCTION QUANTITY
1773
1780
EN
Murat
OZKOK
Department of Naval Architecture and Marine Engineering, Karadeniz Technical University, 61530 Camburnu,Trabzon, Turkey
muratozkok@ktu.edu.tr
Welding process plays a major role in ship production. As welding process can be performed in less time, ship fabrication can be completed in a shorter time. Therefore, it is a significant issue that welding time is able to be ended as soon as possible. For this, operator factor, which is a component of welding time calculation, could be increased. If this is done, welding time could be decreased. The purpose of this study is to determine the effects of operator factor on the production quantity of panel line. In the work, panel line of a shipyard situated in Turkey was illustrated as an example. Whole workstations of panel line were taken into consideration and modeled in SIMIO simulation environment. Changing operator factor in web welding work station on panel line, different welding time values were achieved. These welding time values were then inserted in simulation model and model was run along a specified period and finally production quantities of panel line were obtained as an output. So, the effects of operator factor changing on panel line throughput were determined.
Operator factor,welding time,web welding,panel line,Simulation
http://scientiairanica.sharif.edu/article_3419.html
http://scientiairanica.sharif.edu/article_3419_63a3612c296c1423d302f0de73380e17.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Lycopodium Dust Flame Characteristics Considering Char Yield
1781
1791
EN
M.
Bidabadi
School of Mechanical Engineering Department of Energy Conversion, Combustion Research Laboratory, Iran university of Science and Technology, Narmak, Tehran, Iran
bidabadi@iust.ac.ir
S. A.
Mostafavi
School of Mechanical Engineering Department of Energy Conversion, Combustion Research Laboratory, Iran university of Science and Technology, Narmak, Tehran, Iran
mostafavi@iust.ac.ir
H.
Beidaghy Dizaji
School of Mechanical Engineering Department of Aerospace Engineering, Iran university of Science and Technology, Narmak, Tehran, Iran
beidaghy_hossein@mecheng.iust.ac.ir
F.
Faraji Dizaji
School of Mechanical Engineering Department of Energy Conversion, Combustion Research Laboratory, Iran university of Science and Technology, Narmak, Tehran, Iran
farzadfaraji@mecheng.iust.ac.ir
Organic dust flames deal with a field of science in which many complicated phenomena like pyrolysis or devolatization of solid particles and combustion of volatile and char particles take place. One-dimensional flame propagation in the cloud of fuel mixture has been analyzed in which flame structure is divided into three zones: preheat zone, reaction zone and post flame zone.It is assumed that particles pyrolyze first to yield a fuel mixture consisting of gaseous and charry fuel. In this research, the effect of char content on pyrolysis process has taken into account and a novel non-linear burning velocity correlation is obtained. Our results are in a reasonable agreement with experimental data.
analytical model,Lycopodium particle,Flame temperature,Burning velocity,Char content
http://scientiairanica.sharif.edu/article_3420.html
http://scientiairanica.sharif.edu/article_3420_ffc42a16b088d21fe3d0595c72fac229.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
The Comparison and Successive Iteration of Approximate Solution of Ordinary Differential Equation with Initial Condition by New Modified Krasnoselskii Iteration Method
1792
1804
EN
Necdet
Bildik
Celal Bayar University, Faculty of Arts and Science, Department of Mathematics,Muradiye Campus, 45030, Manisa/TURKEY
necdet.bildik@bayar.edu.tr
Yasemin
BAKIR
Celal Bayar University, Faculty of Arts and Science, Department of Mathematics,Muradiye Campus, 45030, Manisa/TURKEY
jasmin_demirel@hotmail.com
Ali
MUTLU
Celal Bayar University, Faculty of Arts and Science, Department of Mathematics,Muradiye Campus, 45030, Manisa/TURKEY
ali.mutlu@bayar.edu.tr
In this paper, we used the Picard successive iteration method and behind the new Modified Krasnoselskii iteration method in order to solve the different type of the ordinary linear differential equation having initial condition.
By applying the new Modified Krasnoselskii iteration method not only we obtain the approximate solutions for the problem, but also establish the corresponding iterative schemes. Finally, it is shown that the accuracy of the new iteration method (which is called new Modified Krasnoselskii iteration
method) is substantially improved by employing variable steps which adjust themselves to the solution of the differential equation.
Ordinary Differential Equation,Euler Method,Fix Point,Modified Krasnoselskii Iteration Method,Numerical analysis,Picard Successive Iteration Method
http://scientiairanica.sharif.edu/article_3421.html
http://scientiairanica.sharif.edu/article_3421_83f24545f8e4e64a64b2ec92a4839c09.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Finite Volume - Lattice Boltzmann Modeling of Time Dependent Flows
1812
1823
EN
Ahad
Zarghami
Department of Engineering, Science and Research Branch, Islamic Azad University, Fars, Iran
a.zarghami@fsriau.ac.ir
Pourya
Omidvar
Department of Mechanical Engineering, The University of Yasouj, Yasouj, Iran
pourya.omidvar@gmail.com
In this paper, a stable finite volume formulation of lattice Boltzmann method is used to study time dependent flows. For simulation purpose, a cell-centered scheme is implemented to discretize the convection operator and weighting factors are used as flux correctors to enhance the stability. Also, additional lattices at the edge of each boundary cell are used, which allow a much better description of the actual geometrical shape. Compared with previous finite volume formulations, the proposed approach resulted in a wider domain of stability and faster convergence. The scheme is validated through simulations on flow over circular cylinder and mixing layer flow. The results show that the method is a promising scheme in simulating time dependent flows.
LBM,Finite volume,Time Dependent Flow,Circular Cylinder,Mixing Layer
http://scientiairanica.sharif.edu/article_3422.html
http://scientiairanica.sharif.edu/article_3422_9b02108090ecf6b9d572dbfa15af8c0b.pdf
Sharif University of Technology
Scientia Iranica
1026-3098
2345-3605
20
6
2013
12
01
Stabilization of a Vibrating Non-Classical Micro-Cantilever Using Electrostatic Actuation
1824
1831
EN
Ramin
Vatankhah
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
rvatankhah@mech.sharif.edu
Farzad
Karami
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
farzad.karami@gmail.com
Hassan
Salarieh
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
salarieh@sharif.edu
Aria
Alasty
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
aalasti@sharif.edu
A closed-loop control methodology is investigated for stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam with nonlinear electrostatic actuation. The dimensionless form of governing nonlinear partial differential equation (PDE) of the system is introduced. The Galerkin projection method is used to reduce the PDE of system to a set of nonlinear ordinary differential equations (ODE). In non-classical micro-beams, the constitutive equations are obtained based on the non-classical continuum mechanics. In this work, proper control laws are constructed to stabilize the free vibration of non-classical micro-beams whose governing PDE is derived based on the modified strain gradient theory as one of the most inclusive non-classical continuum theories. Numerical simulations are provided to illustrate the effectiveness and performance of the designed control scheme. Also, the results have been compared with those obtained by the classical model of micro-beam.
vibration control,Non-classical micro-beam,Galerkin projection,Electrostatic actuation
http://scientiairanica.sharif.edu/article_3423.html
http://scientiairanica.sharif.edu/article_3423_b80f99b289799bb2cad200eccf09efda.pdf