Abolhassan Asgarshamsi

Golpayegan University of Engineering

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Mohammad Hassan Saidi

Sharif University of Technology

Ahmad Assempour

Sharif University of Technology

Arman Sadeghi

University of Kurdistan

Hossein Pourfarzaneh

Pasargad Institute for Advanced Innovative Solutions

Ali Hajilouy Benisi

Sharif University of Technology

Ali Hajilouy-Benisi

Sharif University of Technology

Hasan Barzegar Avval

Iran University of Science and Technology

H. Karrabi

Sharif University of Technology

Mohammad Goharkhah

Sahand University of Technology

Ahmad Hashemi

Islamic Azad University of Kermanshah

Cooperative Institutions

Sharif University of Technology

Marymount University

University of Tehran

Pasargad Institute for Advanced Innovative Solutions

Iran University of Science and Technology

Atomic Energy Organization of Iran

University of Ontario Institute of Technology

Institut Universitaire de France

Imam Khomeini International University

Centre National de la Recherche Scientifique

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Multi-Point Optimization of Lean and Sweep Angles for Stator and Rotor Blades of an Axial Turbine

Abolhassan Asgarshamsi Ali Hajilouy-Benisi Ahmad Assempour Hossein Pourfarzaneh

In this research, numerical optimization of the rear part of a gas turbine, consisting of a single stage axial turbine is carried out. Automated aerodynamic shape optimization is performed by coupling a CFD flow simulation code with the Genetic Algorithm. An effective multi-point optimization method to improve efficiency and/or pressure ratio of the axial turbine is performed. Some variations of optimization parameters such as lean and sweep angels of stator and rotor blades are accomplished. Furthermore, during the optimization process, three-dimensional and turbulent flow field is numerically investigated using a compressible Navier-Stokes solver. The gas turbine experimental investigations are used for choosing optimization points, specifying the boundary conditions and validation of the simulations. Two operating speeds of the gas turbine are selected for the optimization. Using verified numerical simulation models and the genetic algorithm, the effects of stator and rotor lean and sweep angles on the turbine performance are studied. The present optimization method successfully obtains a result that improves 1.31% and 1.17% in the turbine stage total-to-total efficiency in its design and off-design speeds, respectively. The modified turbine mass parameter at choke condition increases 2.40%.

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10.1115/gt2014-27016

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Citations (6)

Second Law Analysis of Slip Flow Heat Transfer in Annulus Microchannel

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Heat Transfer Equipment; Heat Transfer in Electronic Equipment (2009)

Arman Sadeghi Abolhassan Asgarshamsi Mohammad Hassan Saidi

In the present work, the second law of thermodynamics analysis has been carried out for steady state hydrodynamically and thermally fully developed laminar gas flow in annulus microchannels with asymmetrically heated walls. The rarefaction effects are taken into consideration using first order slip velocity and temperature jump boundary conditions. Viscous heating is also included for both the hot wall and the cold wall cases. Using the velocity distribution obtained in earlier works, the energy equation is solved to get analytically the temperature distribution and consequently to compute the entropy generation rate. The effects of rarefaction and the annulus geometrical aspect ratio on velocity distribution are discussed. The complicated interactive effects of rarefaction, viscous dissipation, the ratio of Brinkman number to dimensionless temperature difference, annulus geometrical aspect ratio and asymmetry on entropy generation rate and Bejan number are shown in graphical form and also discussed in details. The analytical results obtained are compared with those available in the literature and an excellent agreement is observed. It is realized that the effect of the wall heat fluxes ratio on entropy generation is negligible at great values of the ratio of Brinkman number to dimensionless temperature difference, while the effect of increasing values of the annulus geometrical aspect ratio is to severely increase entropy generation. The entropy generation decreases as Knudsen number increases, however the effect of increasing values of Brinkman number and the ratio of Brinkman number to dimensionless temperature difference is to increase entropy generation.

Brinkman number

Bejan number

Dimensionless quantity

Temperature jump

Microchannel

Annulus (botany)

10.1115/ht2009-88383

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Citations (3)

Analytical Solution for Large amplitude Vibrations of Micro-beams Actuated by an Electro-static Force

Scientia Iranica (2013)

Mostafa Baghani Abolhassan Asgarshamsi Mohammad Goharkhah

An analytical study using Variational Iteration Method (VIM) is carried out in order to investigate the vibrations of electro-statically actuated double-clamped and simply-supported micro-beams. Effects of applied voltage and residual axial load on the nonlinear natural frequency and deflection of the micro-beams are studied. It shows that pre-compression in micro-beams increases the amplitude of deflections for a specific applied voltage. Also, an increase in pre-tension motivates the micro-beam to show more nonlinear behavior in an applied voltage. Predicted results are compared with the experimental data available in the literature and also with numerical results which shows a good agreement. It is concluded that the second order approximation of the VIM leads to highly accurate solutions which are valid for a wide range of vibration amplitudes.

Natural frequency

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Analysis of Laminar Flow in the Entrance Region of Parallel Plate Microchannels for Slip Flow

ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels (2009)

Arman Sadeghi Abolhassan Asgarshamsi Mohammad Hassan Saidi

Microscale fluid dynamics has received intensive interest due to the emergence of microelectromechanical systems (MEMS) technology. Fluid flow in microdevices has some characteristics which one of them is rarefaction effect related with gas flow. In this work, the steady state laminar rarefied gas flow in the entrance region of parallel plate microchannels is investigated by the integral method with slip flow conditions at solid surface. The effects of Knudsen number on friction factor and Nusselt number are presented in graphical form as well as analytical form. Also the effect of Knudsen number on hydrodynamic entry length is presented. The results show that as Knudsen number increases the local friction factor and Nusselt number decrease. Also an increment of Knudsen number leads to a larger amount of hydrodynamic entry length.

Microscale chemistry

Knudsen flow

Rarefaction (ecology)

10.1115/icnmm2009-82012

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Citations (10)

Multi-objective optimization of lean and sweep angles for stator and rotor blades of an axial turbine

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering (2014)

Abolhassan Asgarshamsi Ali Hajilouy Benisi Ahmad Assempour Hossein Pourfarzaneh

The axial turbine is one of the most challenging components of gas turbines for industrial and aerospace applications. With the ever-increasing requirement for high-aerodynamic performance blades, three-dimensional aerodynamic shape optimization is of great importance. In this research, the rear part of a gas turbine consisting of a one-stage axial turbine is optimized numerically. A useful optimization algorithm is presented to improve the efficiency and/or pressure ratio of the axial turbine with two different objective functions. The three-dimensional blade-shape optimization is employed to study the effects of the turbine stator and rotor lean and sweep angles on the turbine performance. The investigation is carried out at the turbine design speed. By coupling a verified computational fluid dynamics simulation code with the genetic algorithm, an automated design procedure is prepared. Geometry candidates for the optimization algorithm are generated by re-stacking of the two-dimensional airfoil sections. Three-dimensional, turbulent, and compressible flow field is numerically investigated via a Navier–Stokes solver to calculate various objective functions. Experimental results of the gas turbine are used for specifying the boundary conditions and validation of the simulation results. The proposed method results in 1.3% and 1.5% improvements in the turbine stage efficiency in design speed and reduced mass parameter at choke condition, respectively.

Axial Compressor

Solver

10.1177/0954410014541080

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Citations (21)

GENETIC ALGORITHM APPLICATION FOR AN AXIAL TURBINE STATOR AND ROTOR CASCADE OPTIMIZATION

Abolhassan Asgarshamsi Ali Hajilouy Benisi A Assempour Ahmad Hashemi

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Laminar Forced Convection in Annular Microchannels With Slip Flow Regime

ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels (2009)

Arman Sadeghi Abolhassan Asgarshamsi Mohammad Hassan Saidi

Fluid flow and heat transfer at microscale have attracted an important research interest in recent years due to the rapid development of microelectromechanical systems (MEMS). Fluid flow in microdevices has some characteristics which one of them is rarefaction effect related with gas flow. In this research, hydrodynamically and thermally fully developed laminar rarefied gas flow in annular microducts is studied using slip flow boundary conditions. Two different cases of the thermal boundary conditions are considered, namely: uniform temperature at the outer wall and adiabatic inner wall (Case A) and uniform temperature at the inner wall and adiabatic outer wall (Case B). Using the previously obtained velocity distribution, energy conservation equation subjected to relevant boundary conditions is numerically solved using fourth order Runge-Kutta method. The Nusselt number values are presented in graphical form as well as tabular form. It is realized that for the case A increasing aspect ratio results in increasing the Nusselt number, while the opposite is true for the case B. The effect of aspect ratio on Nusselt number is more notable at smaller values of Knudsen number, while its effect becomes slighter at large Knudsen numbers. Also increasing Knudsen number leads to smaller values of Nusselt number for the both cases.

Rarefaction (ecology)

Temperature jump

10.1115/icnmm2009-82013

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Citations (4)

Numerical Simulation of Turbulent Heat Transfer on a Rotating Disk With an Impinging Jet

ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, Volume 3 (2010)

Mohammad Hassan Saidi H. Karrabi Hasan Barzegar Avval Abolhassan Asgarshamsi

A numerical study has been earned out to investigate the fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk. The temperature distribution and convection heat transfer coefficient on the disk are calculated. Flow is considered to be steady, incompressible and turbulent. k-ε RNG model is used to model the turbulent flow. Two new criteria are introduced and used to evaluate the performance of cooling process which are maximum temperature difference on the disk and the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the effect of both thermo physical properties of the disk material and cooling process. In order to verify the numerical approach, results have been compared with the experimental data which shows a good agreement.

10.1115/esda2010-24661

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Citations (1)

Multi-point Optimization of Lean and Sweep Angles for Stator and Rotor Blades of an Axial Turbine

Iranian Journal of Science and Technology Transactions of Mechanical Engineering (2016)

Abolhassan Asgarshamsi Ali Hajilouy-Benisi Ahmad Assempour Hossein Pourfarzaneh

Axial Compressor

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10.1007/s40997-016-0033-5

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Citations (8)

Multi-objective optimum stator and rotor stagger angle distributions of an axial turbine stage

Scientia Iranica (2015)

Abolhassan Asgarshamsi Ali Hajilouy Benisi Ahmad Assempour

Gas turbine aerodynamic shape optimization has been the subject of several numerical studies in the past decades. In this research, numerical optimization of a one stage axial turbine is considered. A practical and eective optimization method to improve efficiency and/or pressure ratio of the axial turbine is presented. Particular modications are accomplished with a limited number of optimization parameters, by stator and rotor blades re-staggering. A three-dimensional numerical model has been prepared and veried through experimental data, which are obtained from the reference gas turbine engine test rig. Coupling the veried numerical simulation solver and genetic algorithm, the effects of stator and rotor stagger angle distributions on the turbine performance are investigated. The optimization is carried out at the turbine design operating condition. To accelerate the GA convergence rate, the numerical mesh sizes are rened in each generation. As a result, the overall computational time decreases by 20%. Dening two objective functions, this optimization approach resulted in the turbine stage isentropic eciency improvement of 0.85% and 0.86%, in the rst and second objective functions, respectively.

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Isentropic process

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Citations (1)