eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
3
16
10.22060/ajme.2019.14840.5746
3365
Stall margin improvement and increase pressure ratio in transonic axial compressor using circumferential groove casing treatment
Alireza Jafar Gholi Beik
jafargholibeik@jsu.ac.ir
1
Seyed Hosein Torabi
htorabi@mail.kntu.ac.ir
2
Hassan Basirat Tabrizi
hbasirat@aut.ac.ir
3
Energy exchange, Mech. Eng. Dept., Jundi Shapor University of Technology, Dezful, Iran
Aerospace. Eng. Dept., Khaje Nasir Toosi University of Technology, Tehran, Iran
Amirkabir University of Technology(Tehran Polytechnic)*mechanical engineering
AbstractMaximum pressure ratio and aerodynamic blades loading are the most important factors in designing axial compressor restricted by minimum airflow. The present work aims to stall margin and total pressure ratio in transonic axial compressor using circumferential groove casing treatment (CGCT). In the first step, untreated compressor was simulated, compared, and agreed well with the experimental data. Then the treated rotor was simulated and results indicated that using CGCT improves the stall margin and increases the rotor pressure ratio. Stall margin was improved by 8% and the pressure ratio before stall condition and at the design point increased by 2.6% and 2.8 %, respectively. Additionally, it replaces normal shock with oblique shock near instability, causing less total pressure drop, moreover, the oblique shocks occurrence restricts separation zones and assists the rotor to perform far from instability. Furthermore, axial speed passing through rotor in a certain mass flow increases by 15 m/s, and then kinetic energy and stability increased. However, total efficiency of rotor reduces near 1%. In the last step, engine was analyzed with the aid of cycle analysis and leads to 62kW increase in shaft power as well as 1.87 g/kNs less fuel consumption due to 2.8% increase in the rotor pressure ratio.
https://ajme.aut.ac.ir/article_3365_bec88b4afa5c32d32dfea41740fd9cf0.pdf
Transonic axial compressor
Circumferential groove casing treatment
Stall margin
EFFICIENCY
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
17
30
10.22060/ajme.2019.15087.5761
3370
Air Bubble Collapse in Non-Newtonian Medium with an Application in Biology
Shahrokh Boland
shahrokhboland@ut.ac.ir
1
Sahand Majidi
s_majidi@sbu.ac.ir
2
Asghar Afshari
afsharia@ut.ac.ir
3
University of Tehran
Shahid Beheshti University
University of Tehran*
An unsteady compressible multiphase flow solver is developed and used to simulate shock-bubble interaction in a non-Newtonian fluid. A five-equation multiphase model that accounts for capillary and viscous effects is employed and discretized by finite volume methodology. Harten-Lax-van Leer-Contact (HLLC) Riemann solver is invoked to compute the convective fluxes and Tangent of Hyperbola for Interface Capturing (THINC) interface sharpening scheme is applied to reduce the excessive diffusion at the interface. Multiple benchmark problems such as Air-Helium Shock Tube, shock cavity interaction, Rayleigh-Taylor instability and underwater explosion are probed to evaluate the performance and accuracy of this method. The results obtained compare well with the available experimental and numerical data. The developed solver is then used to study shock-interface interaction in both Newtonian and non-Newtonian mediums. Non-Newtonian liquid is resembling the blood modeled by Carreau-Yasuda constitutive equation. The obtained results show an expedition of bubble-collapse with a higher jet tip velocity in non-Newtonian medium compared to that in the Newtonian surrounding liquid. Moreover, a third phase adjacent to the bubble collapse is considered and the penetration depth of the re-entrant jet in the neighboring phase is studied as a measure of tissue injury. Our results show that by increasing post shock pressure, the re-entrant jet velocity and thus the penetration depth increases. Furthermore, increasing the adjacent phase viscosity results into less penetration depth in the tissue.
https://ajme.aut.ac.ir/article_3370_13460e4524e4dd13d16892a14b55c14b.pdf
Compressible multiphase flow
Shockwave lithotripsy
Carreau-Yasuda model
Shock bubble interaction
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
31
40
10.22060/ajme.2019.15527.5778
3405
Modeling of an Upper-Convected-Maxwell fluid hammer phenomenon in the pipe system
Banafsheh Norouzi
hatami1355@yahoo.com
1
ahmad Ahmadi
a.ahmadi@shahroodut.ac.ir
2
Mahmood Norouzi
m.norouzi@shahroodut.ac.ir
3
Mohsen LashkarBolook
mlbolok@iust.ac.ir
4
Civil Engineering, Shahrood University of Technology, Shahrood, Iran
Civil Engineering, Shahrood University of Technology, Shahrood, Iran
Mechanic Engineering, Shahrood University of Technology, Shahrood, Iran
Civil Engineering, Golestan University, Gorgan, Iran
In this paper, the occurrence of water hammer phenomenon is examined in a situation that instead of water, an upper-convected-Maxwell fluid flows in a pipe system. This phenomenon is called an “upper-convected-Maxwell fluid hammer”. This expression relates to the transients of Maxwell fluid caused by the sudden alteration in the conditions of flow. Upper-convected-Maxwell fluids are a kind of non-Newtonian viscoelastic fluids. The properties of this group of fluids lead to their different behaviour during fluid hammer phenomenon compared to Newtonian fluids. The system studied is a valve- horizontal pipe and reservoir. The equations representing the conservation of mass and momentum govern the transitional flow in the pipe system. The numerical method used is a two-step variant of the Lax-Friedrichs (LxF) method. Firstly, the non-dimensional form of governing equations is defined, then, the effect of Deborah and Reynolds numbers on pressure historic is investigated. The results revealed that increasing Deborah number, indicating the elasticity of the polymer, increases the oscillation height and consequently attenuation time of the transient flow becomes longer. It was also found that in low Reynolds, in a Newtonian fluid, ‘‘line packing phenomenon’’effect is observed only at the first time period but in UCM fluid the effect of this phenomenon continues to more time periods and damping time becomes longer.
https://ajme.aut.ac.ir/article_3405_62c9cf86d20b4dbd5feb498c8e98cc91.pdf
Upper Convected Maxwell Model
Lax-Friedrichs (LxF) method
non Newtonian fluid Hammer
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
41
50
10.22060/ajme.2019.14684.5738
3286
Geometry Shape Effects of Nanoparticles on Fluid Heat Transfer Through Porous Channel
AKINBOWALE AKINSHILO
ta.akinshilo@gmail.com
1
DEPT. OF MECH. ENGR., UNIVERSITY OF LAGOS, NIGERIA.
In this paper the geometry effects of different nanoparticles such as cylindrical, spherical and lamina on heat transfer of fluid transported through contracting or expanding microchannel are considered. The nanofluid flow and heat transfer through the porous channel are described using mathematical models. Since the mathematical models are nonlinear in nature the homotopy perturbation method (HPM), an approximate analytical method is adopted to provide analytical solution to the mathematical model. The fast convergence rate coupled with analytical procedural stability motivates the use of the HPM as the favored method in providing solutions to the system of coupled, higher order differentials.The obtained analytical solution is used to investigate the influence of particle shape of the nano sized materials on heat transfer of fluid flowing through a porous medium considering a uniform magnetic field. It is illustrated from results that lamina nanoparticle shape shows higher dimensionless temperature and thermal conductivity when compared with nano shaped particles of cylinder and sphere respectively due to variations in thermal boundary layers. Results obtained from this study prove useful in the advancement of science and technology including micro mixing, nanofluidics and energy conservation. Comparing obtained analytical solution with fourth order numerical solution, good agreement was established.
https://ajme.aut.ac.ir/article_3286_ac4f55ef87a961e25194351ff3f05c51.pdf
heat transfer
Nanofluid
Porous channel
magnetic field
Homotopy Perturbation Method
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
51
66
10.22060/ajme.2019.14843.5747
3433
MHD effect on Nanofluid Flow and Heat transfer in Backward-Facing Step using two-phase Model
Farrokh Mobadersani
f.mobadersani@mee.uut.ac.ir
1
Araz Rezavand Hesari
araz.rezavand-hesari.1@ulaval.ca
2
Department of Mechanical Engineering, Urmia University of Technology
Mechanical Engineering Department, Universite Laval, Quebec, Canada
Magneto hydrodynamics (MHD) effects on nanofluid flow in backward-facing step is studied using two-fluid model of Buongiorno. The results of the current finite element simulations are compared with previous experimental and numerical analysis. Due to the utilization of two-phase model, variable nanoparticle concentration and nanofluid properties are considered. Thermophoresis and Brownian diffusivities are calculated in particle dispersion. Effects of Reynolds number, particle volume fraction, magnetic field and Hartmann numbers are studied on heat transfer and fluid flow characteristics. It is shown that introduction of nanoparticles as a second phase, pushes reattachment point further into the downstream, while magnetic field has opposite effect and pushes it backward into the upstream. Particles are shown to be migrating from hot to cold regions due to the dispersion mechanisms considered. In comparison to single phase models, there is 3.7% decrease in maximum Nusselt number and more than 40% difference in the reattachment point location. Accuracy of the reattachment point is shown through previous pure fluid studies, the comparison to which show less than 0.8% tolerance with most recent studies. Relative effect of diffusion mechanisms is compared in different flow conditions, which show up to 12.5% difference. Application of magnetic field results in average Nusselt number increase of more than 10% by Hartmann number of 12.
https://ajme.aut.ac.ir/article_3433_e93b1bfd462cb615ba73bfbfab34ec32.pdf
Nanofluid
Buongiorno Model
Brownian motion
Thermophoresis effect
MHD
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
67
78
10.22060/ajme.2019.15227.5767
3432
The effects of subcooled temperatures on transient pool boiling of deionized water under atmospheric pressure
ahmadreza ayoobi
ar.ayoobi@stu.yazd.ac.ir
1
Ahmadreza Faghih Khorasani
faghih@yazd.ac.ir
2
Mohammad Reza Tavakoli
mrtavak@cc.iut.ac.ir
3
department of mechanical engineering, yazd university
Department of Mechanical Engineering, Yazd University
Department of Mechanical Engineering, Isfahan University of Technology
Pool boiling heat transfer and critical heat flux (CHF) were experimentally studied in subcooled temperatures ranging 0 to 20 under transient power conditions. The heating rate in the test section was increased linearly depending on time by applying voltage control for 1 to 1000s. The increase in heat flux starts from the free convection regime to the film-boiling regime. The transient boiling heat transfer coefficient (TBHTC), transient wire superheat temperature, transient heat flux and transient CHF were also obtained. The results showed that in the case of all subcooled temperatures and periods, the TBHTC increased in the nucleate boiling region because of the growth, separation, motion and turbulence of the bubbles. The TBHTC also decreased in the transition from nucleate boiling to film boiling because some part of the wire covered by temporary thin vapor film. The wire isolated from the body of working fluid and the bubble separations decreased. The TBHTC again increased in film boiling due to the increment of radiation heat transfer. The TBHTC decreased in the second part of the film boiling due to the heat flux and the vapor film thickness around the wire had increased. Relative to the saturation condition, the timely average of the wire superheat temperature for subcooled temperatures of 10 and 20, respectively, decreased by 9.23 and 9.29% in the nucleate boiling region and in a time period of 1000s. A high-speed camera was used to show bubble and vapor film behavior around the heating wire for the subcooled temperatures.
https://ajme.aut.ac.ir/article_3432_356730cb0ae73e4190a95c392c830585.pdf
transient pool boiling
CHF
heating rate
subcooled temperature
TBHTC
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
79
88
10.22060/ajme.2019.14799.5745
3452
An experimental study on submerged flame in a two-layer porous burner
Seyed abdolmehdi Hashemi
hashemi@kashanu.ac.ir
1
Mohammad Reza Faridzadeh
mr.faridzadeh@gmail.com
2
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Combustion in porous media is an effective method to minimize dissipations and save energy. It enhances the efficiency of the system while reducing environmental pollution. The conditions for the formation of a steady-state submerged flame in a ceramic (SiC) porous medium were investigated at four firing rates. The results were obtained on a ceramic foam with a cross section area of 63.6 cm2 and pore density of either 10 or 30 ppi. The reactants were air and natural gas with various equivalence ratios. In this experimental study, eight thermocouples were mounted on the burner walls along its axis in order to track the flame position, and the results were presented as temperature profiles of the porous wall. It was observed that the formation of submerged flame depends on firing rate and equivalence ratio. The stability limit of submerged flame (the range between surface flame and flash back limits) is reduced by increasing the firing rate. Results show that the maximum temperature takes place near the interface of the two layers. Also, it was observed that when the mixture velocity is low, the stability limit extends. Finally, the ranges of equivalence ratio and mixture velocity for the formation of submerged flame are presented at various firing rates.
https://ajme.aut.ac.ir/article_3452_705919185bac6bda9a6ef52d05e237cd.pdf
Experimental study
Flame Formation
Porous burner
Premixed Methane-Air Combustion
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
89
102
10.22060/ajme.2019.14875.5749
3397
Thermodynamic analysis of a novel heat pipe based regenerative combined system
Vahid Beygzadeh
vbeygzadeh@gmail.com
1
Shahram Khalilarya
sh.khalilarya@urmia.ac.ir
2
Iraj Mirzaee
i.mirzaee@urmia.ac.ir
3
Vahid Zare
v.zare@uut.ac.ir
4
Gholamreza Miri
gholamreza.miri@gmail.com
5
Faculty of Mechanical Engineering, Urmia University of Technology, Urmia, Iran
Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
Mechanical Engineering Department, Faculty of Engineering, Urmia University, Urmia, Iran
Faculty of Mechanical Engineering, Urmia University of Technology, Urmia, Iran
Department of Business Management, National Iranian Oil Refining & Distribution Company, Tehran, Iran
A comprehensive thermodynamic analysis is presented of a new solar system for heating and power generation. Energy and exergy analyses are used to characterize the exergy destruction rate in any component and investigate solar system performance. The system composed of a solar heat pipe evaporator (SHPE), an auxiliary pump, a condenser, a turbine, an electrical generator, a domestic water heater, a regenerator, a water preheater and a pump. The solar system provides heating and electricity during the summer and spring in Tabriz, Iran. The analysis involves the specification of effects of varying SHPE condenser pinch point temperature, varying solar radiation intensity and varying SHPE heat removal factor on the energetic and exergetic performance of the system. The performance parameters calculated are energy flow, exergy destruction rate, energetic and exergetic efficiencies. The results also showed that the main source of the exergy destruction rate is the SHPE. In the SHPE, 291.1 kW of the input exergy was destroyed. Other main sources of exergy destruction rate are the SHPE condenser, at 6.655kW; then the turbine, at 6.228 kW; and the water preheater, at 0.907 kW. The overall energetic and exergetic efficiencies of the combined solar system was approximately 69.57% and 12.41%, respectively.
https://ajme.aut.ac.ir/article_3397_8cb29876ed834d4c5750e36f095cf3a4.pdf
Energy Efficiency
Exergy efficiency
solar heat pipe system
regenerative organic Rankine cycle
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
103
118
10.22060/ajme.2019.15375.5770
3383
Time-Dependent Creep Response of Magneto-Electro-Elastic Rotating Disc in Thermal and Humid Environmental Condition
Mahdi Saadatfar
m.saadatfar@gmail.com
1
Department of Mechanical Engineering, University of Qom
The aim of this paper is to analyze the time-dependent stress redistribution of a rotating magneto-electro-elastic (MEE) disc. The disc is supposed to be placed in an axisymmetric temperature and moisture fields. Besides, the disc is under a centrifugal body force, an induced electric potential in addition to magnetic potential. Using equilibrium, electrostatic and magnetostatic equations, strain-displacement and stress-strain relations together with hygrothermal equations, a differential equation is obtained in which there are creep strains. Primarily, disregarding the creep strain, an analytical solution for the initial stresses, electromagnetic potentials and displacement is developed. Then, using Prandtl-Reuss relations, creep stress rates and electromagnetic potentials rates are obtained. Finally, the history of stresses, electric and magnetic potentials is obtained iteratively. In the numerical section, the influence of creep evolution, hygrothermal environmental condition, angular velocity and temperature- and moisture-dependency of elastic coefficients on the behavior of MEE disc is analyzed comprehensively. The results show that the effect of hygrothermal loading and angular velocity becomes less significant after creep evolution. Also, the results imply that analysis of the effect of temperature- and moisture- dependence after creep evolution must be considered in the design progress. Besides, to avoid cracking, increasing in the tensile hoop stress at the internal surface with increasing in hygrothermal loading must be considered in design progress.
https://ajme.aut.ac.ir/article_3383_d0a0b15419b896bc636d4f3e2a4baddc.pdf
Rotating disc
magneto-electro-elastic
Time-dependent creep
Hygrothermal loading
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
119
126
10.22060/ajme.2019.15312.5771
3357
Effects of Functionalized Multi-Walled Carbon Nanotubes on the Low-Velocity Impact Response of Sandwich Plates
Ehsan Rashidi
e.rashidii@gmail.com
1
Saeid Feli
felisaeid@razi.ac.ir
2
Department of Mechanical Engineering, Razi University, Kermanshah, Iran
Department of Mechanical Engineering, Razi University, Kermanshah, Iran
One method to reduce the damage caused by low-velocity impact in sandwich composites is using nanoparticles as the reinforcement material in the face sheets. The aim of this study is to investigate the effects of different weights of functionalized multi-walled carbon nanotubes on mechanical properties of face sheets and response of sandwich plates that undergo low-velocity impact through experimental investigations. The face sheets are made of nano-modified EPIKOTE 828 with triethylenetetramine as the curing agent, and a core of polyurethane foam. The functionalized multi-walled carbon nanotubes are dispersed into the epoxy system in 0.1%, 0.3% and 0.5% weight-to-matrix. The low-velocity impact test was performed using a drop tower impact machine, at two different energy levels. The stress-strain, history of contact force, velocity-time, absorbed energy-time and force-deflection are plotted and some parameters such as elastic modulus, tensile strength, bounce time, upward velocity, peak load and maximum deflection are reported. The tensile test results show that with the slight increase in the volume fraction of carbon nanotubes, the elastic modulus and ultimate tensile strength are improved. Also, the minor amount of carbon nanotubes reduce bounce time, residual deformation, and maximum deflection and increase peak load in the sandwich plate. In addition, carbon nanotubes reduce the damaged area.
https://ajme.aut.ac.ir/article_3357_38b1dca63d81a9654b76ee0d80600ca3.pdf
Nanocomposite
Sandwich composite
Low-velocity impact
Functionalized multi-walled carbon nanotubes
Damage
eng
Amirkabir University of Technology
AUT Journal of Mechanical Engineering
2588-2945
2588-2937
2020-01-01
4
1
127
148
10.22060/ajme.2019.14979.5754
3417
Effect of Stator dynamics on the Chaotic Behavior of Rotor-Disk-Bearing System under Rub-Impact between Disk and Stator
Abbas Rahi
a_rahi@sbu.ac.ir
1
Ahmad Haghani
ahaghani70@gmail.com
2
Pedram Safarpour
p_safarpour@sbu.ac.ir
3
Faculty of Mechanical & Energy Engineering, Shahid Beheshti University
Faculty of Mechanical & Energy Engineering, Shahid Beheshti University
Faculty of Mechanical & Energy Engineering, Shahid Beheshti University
In the present study, the effect of stator dynamics on the chaotic behavior of a rotor-disk-bearing system with rub-impact between disk and stator is investigated. The governing equations of motion are derived using Jeffcott model and Newton's second law and then are made dimensionless. Governing Equations are also achieved utilizing the Short Bearing Theory and considering nonlinear forces acting on the oil film. Furthermore, unbalance force and bow shaft force which cause rub-impact between disk and stator are considered in the equations of motion. In the beginning, the system is modeled regardless of stator dynamics, and then the stator dynamics is also considered in the modeling of the system. In both cases, the system behavior is studied by bifurcation diagrams, time series diagrams, phase plane diagrams, power spectrum diagrams, Poincaré maps, and maximum Lyapunov exponent, respectively. The obtained results show that the type of stator dynamics modeling has a significant effect on the prediction of the response of a disk-bearing system with rub-impact between disk and stator. In other words, the results show the system has a chaotic behavior without considering the dynamics of the stator in mathematical modeling, while in the case of considering the stator dynamics and using the suitable values for the stator stiffness, the motion behavior of the system can be changed from the chaotic to the regular and periodic motion. Keywords: Rotor-disk-bearing, stator dynamics, rub-impact, chaotic behavior.
https://ajme.aut.ac.ir/article_3417_71d49f5931fa5967bba9fdf1ca33da3f.pdf
Rotor-disk-bearing
stator dynamics
rub-impact
chaotic behavior