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inlet-flow
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An investigation on turbocharger turbine performance parameters under inlet pulsating flow
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 134, Issue 8 , 2012 ; 00982202 (ISSN) ; Masoud, B ; Mohammad, T. R ; Sharif University of Technology
ASME
2012
Abstract
Three-dimensional steady and unsteady (pulsating) compressible flows in a vane-less turbocharger turbine of a 1.7 liter SI engine are simulated numerically, and the results are validated experimentally using a turbocharged on-engine test cell. Simulations are carried out for a 720° engine cycle at three engine speeds, and the complete forms of volute and rotor vanes are modeled. Two ways for modeling the rotating wheel, multiple reference frames (MRF), and sliding mesh (SM) techniques are also examined. Finally, the effects of pulsating flow on the turbocharger turbine performance parameters (TTPP) such as the inlet static pressure, reduced mass flow rate, and efficiency are obtained and...
Zero D and 3D analysis of the centrifugal compressor of a gas turbine and its evaluation using experimental results
, Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 1 , November , 2011 , Pages 897-906 ; 9780791854877 (ISBN) ; Pourfarzaneh, H ; Hajilouy Benisi, A ; Sharif University of Technology
Abstract
In compressor design, it is necessary to simulate the compressor before manufacturing and performing experimental studies. One of the most efficient and common modeling methods is zero D analysis using scaling method with constant coefficients. Although it is efficient in the vicinity of the design point, its results are not acceptable in the off design points due to the growing error by getting away from design points. In this research, a novel zero D analysis method is developed predict accurately the compressor performance not only in the design point but also in the off design pint. In this method, variable coefficients are used instead of constant coefficients, which are obtained based...
Performance prediction of axial flow gas turbine by using of different models of energy loss and its comparison with experimental results
, Article 2011 Proceedings of the 3rd Conference on Thermal Power Plants, CTPP 2011 ; 2011 ; 9781479905911 (ISBN) ; Eftari, M ; Taheri, E. M. F ; Shahhosseini, M. R ; Rad, M ; Sharif University of Technology
Abstract
The aim of present research is the performance simulation of axial flow turbine on different operating conditions by using of one dimentional modeling method. In this method by receiving the flow inlet conditions and turbine geometry, velocity triangles at blade inlet and outlet are obtained and performance characteristics of the turbine are calculated. As respects the importance of modeling for performance prediction and optimization in initial desing level, in following work, that is based on one dimentional modeling method, after the presentation of solution algorithm by trial and error method and introduction of different loss models for modeling, the obtained results of modeling were...
Proposal of a new design for valveless micropumps
, Article Scientia Iranica ; Volume 18, Issue 6 , December , 2011 , Pages 1261-1266 ; 10263098 (ISSN) ; Movahhedy, M. R ; Assempour, A ; Sharif University of Technology
2011
Abstract
A new design for a valveless micropumping device has been proposed that integrates two existing pumping technologies, namely, the wall induced traveling wave and the obstacle-type valveless micropump. The liquid in the microchannel is transported by generating a traveling wave on the channel, while the placing of two asymmetric trapezoid obstacles, along the centerline of the channel inlet and outlet, leads to a significant (up to seven times) increase of the net flow rate of the device. The effectiveness of this innovative design has been proved through a verified three-dimensional finite element model. FluidStructure Interaction (FSI) analysis is performed in the framework of an Arbitrary...
Performance study of a supersonic inlet in the presence of a heat source
, Article Scientia Iranica ; Volume 18, Issue 3 B , 2011 , Pages 375-382 ; 10263098 (ISSN) ; Farahani, M ; Sepahi Younsi, J ; Sharif University of Technology
2011
Abstract
The flow over a supersonic inlet has been investigated experimentally and numerically at a free stream Mach number of 2 and a zero degree angle of attack. Wind tunnel tests were performed to obtain the performance parameters of the inlet and were used as a baseline and validation tools for the numerical code. A heat source was added to the flow field at a distance ahead of the inlet. The effect of heat source addition on the main performance parameters of the inlet is investigated numerically. Results show that the heat source considerably reduces drag coefficient; however, its effect on pressure recovery is not favorable. This unfavorable effect was then minimized by controlling heat source...
An experimental study of buzz instability in an axisymmetric supersonic inlet
, Article Scientia Iranica ; Volume 18, Issue 2 B , 2011 , Pages 241-249 ; 10263098 (ISSN) ; Farahani, M ; Asgari Kaji, M. H ; Sharif University of Technology
Abstract
An experimental study was carried out on an axisymmetric supersonic inlet with external compression. The scope of this study was to investigate the general characteristics of the inlet buzz under various design and off-design conditions. The model was equipped with accurate and high frequency pressure sensors and the tests were conducted at Mach numbers varying from 1.8 to 2.5, at various angles of attack, and at different mass flow rates. Shadowgraph flow visualization, together with a high speed camera, was used to capture the external shock structure in front of the inlet. Frequencies of buzz were obtained from both the shadowgraph pictures and analysis of the pressure data. The amplitude...
Experimental observation of the flow structure of turbidity currents
, Article Journal of Hydraulic Research ; Volume 49, Issue 2 , 2011 , Pages 168-177 ; 00221686 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Abstract
The structure of turbidity currents released on a sloping bed below fresh water is investigated. Kaolin is used as a suspended material. Laboratory observations indicate that if a dense layer moves through the channel, the current thickness increases due to a hydraulic jump. This phenomenon occurs under special inlet conditions and has a significant effect on the current structure including velocity profile, current height and bed shear stress. Flows with different inlet Froude numbers based on various inlet concentrations behave more distinctly than those based on different inlet opening heights. Laboratory experiments indicate that an increase in the inlet Froude number causes an increase...
Numerical anaysis of a thermopneumatic micropump
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; 2010 , Pages 1135-1140 ; 9780791854501 (ISBN) ; Shafii, M. B ; Saidi, M. H ; Sharif University of Technology
2010
Abstract
Thermopneumatic micropump is one type of positive displacement micropump, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet channels of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which...
Experimental and numerical investigation of a centrifugal compressor
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 3 , 2010 , Pages 447-458 ; 9780791849170 (ISBN) ; Hajilouy Benisi, A ; Nili Ahmadabadi, M ; Sharif University of Technology
2010
Abstract
In this research, centrifugal compressor of a gas turbine is investigated experimentally and numerically. Operation line of the compressor as a component of the gas turbine is obtained experimentally by measurements of impeller rotational speed, and flow parameters at the compressor inlet and outlet during the gas turbine operation. The flow field inside the impeller and diffusers are analyzed numerically using a full 3D Navier-Stokes program with SST turbulence model. Boundary conditions for the numerical simulation are specified from the experimental measurements. The operation line of the compressor is obtained numerically, which is compared with that of the experimental results, and...
Experimental investigation of flow instability in a supersonic inlet
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 3 , 2010 , Pages 515-521 ; 9780791849170 (ISBN) ; Farahani, M ; Sharif University of Technology
2010
Abstract
An extensive wind tunnel test series were conducted on an axisymmetric supersonic inlet. The model was tested at Mach numbers from 1.8 to 2.2 and at different values of mass flow rate. Shadowgraph flow visualization was used to capture the external shock structure in front of the inlet. The goal of this study is to find out the general characteristics of the inlet buzz. Frequencies of the buzz have been achieved from the analysis of the pressure data as well as the shadowgraph pictures. The amplitude of the shock waves motion has been measured from the visualization pictures too. In the some large value of mass flow rate, the frequency of shock oscillation increased versus Mach number. Also...
A novel QUASI-3D design method for centrifugal compressor meridional plane
, Article Proceedings of the ASME Turbo Expo, 14 June 2010 through 18 June 2010 ; Volume 7, Issue PARTS A, B, AND C , 2010 , Pages 919-931 ; 9780791844021 (ISBN) ; Durali, M ; Hajilouy Benisi, A ; Sharif University of Technology
Abstract
This paper is concerned with a quasi-3D design method for centrifugal compressor impeller in the meridional plane. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain of which some unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called spines. The difference between target and current pressure distribution causes to deform flexible boundary at each modification...
A molecular dynamics study of fluid flows through slit-like nanochannels using two different driving systems
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010 ; Issue PARTS A AND B , 2010 , Pages 1029-1033 ; Khaledi Alidusti, R ; Sabouri, M ; Abbasi, H. R ; Sharif University of Technology
Abstract
The Poiseuille flow through slit-like nanochannels is investigated using the nonequilibrium molecular dynamics simulations. To drive a dense flow through the channel, we use two self-adjusting vertical plates strategy. These plates force the liquid to flow through the nanochannel under adjustable inlet and outlet boundary conditions. Comparing with the dual-control-volume grand-canonical molecular dynamics method, the current strategy provides many advantages. The current strategy does not need particle insertion and deletion, therefore, the system dynamics would not be affected at all. Moreover, the number of particles in the simulation system is fixed due to inserting the two...
Inferential closed-loop control of particle size and molecular weight distribution in emulsion polymerization of styrene
, Article Polymer Engineering and Science ; Volume 50, Issue 12 , 2010 , Pages 2306-2320 ; 00323888 (ISSN) ; Shahrokhi, M ; Abedini, H ; Sharif University of Technology
Abstract
In this work, simultaneous inferential control of particle size distribution (PSD) and molecular weight distribution (MWD) in a semi-batch emulsion polymerization reactor of styrene has been addressed. Using a comprehensive dynamic model for PSD and MWD predictions and performing a sensitivity analysis, it has been revealed that free surfactant and chain transfer agent (CTA) concentrations in the reactor are the most suitable candidates for inferential control of PSD and MWD, respectively. To control concentrations of these species in the reactor, their inlet feed flow rates are used as manipulated variables. It is assumed that the concentration of CTA is measured infrequently and therefore...
On the application of fuzzy predictive control based on multiple models strategy to a tubular heat exchanger system
, Article Transactions of the Institute of Measurement and Control ; Volume 32, Issue 4 , 2010 , Pages 395-418 ; 01423312 (ISSN) ; Sadati, N ; Sharif University of Technology
2010
Abstract
The purpose of the paper presented here is to control the fluid temperature that flows in the inner tube of a tubular heat exchanger system by means of the fluid flow pressure. This system in its present form has a specified range of the coefficients' variation, while the temperature of the outlet fluid could generally be controlled by either the temperature or the flow of the inlet fluid flowing in the shell tube. The control realization for the system presented is often complicated, because the variation of the system coefficients and the reference signal must be thoroughly covered by the control action. In such a case, the system behaviour must first be represented by the multiple...
Effect of bubble size and angle of tapering upriser pipe on the performance of airlift pumps
, Article Particulate Science and Technology ; Volume 28, Issue 4 , Aug , 2010 , Pages 332-347 ; 02726351 (ISSN) ; Saidi, M. H ; Karimi, A ; Zamiri, A ; Sharif University of Technology
2010
Abstract
Airlift pumps are devices with the ability to lift liquid phase by injecting the gas phase. Parameters that affect the performance of these pumps are divided into two groups. The first group contains design parameters such as diameter of the pipe, tapering angle of the upriser pipe, and the submergence ratio, which is the ratio of immersed length to the total length of the upriser. The second group includes operating parameters such as the gas flow rate, bubble diameter, bubble distribution, and inlet gas pressure. In this research, the performance of an airlift pump is investigated numerically for different submergence ratios and different diameter of the upriser pipe. For this purpose, an...
Three dimensional numerical investigation of air flow over domed roofs
, Article Journal of Wind Engineering and Industrial Aerodynamics ; Volume 98, Issue 3 , 2010 , Pages 161-168 ; 01676105 (ISSN) ; Bahadori, M. N ; Sharif University of Technology
2010
Abstract
Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. However their favorable thermal performance made them to be employed in other buildings such as bazaars, or market places, in Iran. The aim of this study was to determine the air pressure distribution over domed roofs, employing a numerical method. In this investigation, a three-dimensional model and a laminar inlet air flow were considered. The k-ε RNG method was employed for the turbulent flow simulation method. Simulation was run under three conditions of windows and a hole on top of the dome being open, or closed. The results were compared with the...
Hydrodynamics of secondary settling tanks and increasing their performance using baffles
, Article Journal of Environmental Engineering ; Volume 136, Issue 1 , 2010 , Pages 32-39 ; 07339372 (ISSN) ; Firoozabadi, B ; Ashjari, M. A ; Sharif University of Technology
Abstract
Generally, the flow in settling tanks is stratified, but the effect of buoyancy force on the flow field depends on the inlet concentration of particles and flow bulk velocity. A common approach for increasing settling tanks performance is to use baffles which can reduce effects of the unfavorable phenomena such as short circuiting between inlet and outlet and density currents in primary and secondary settling tanks, respectively. The suitable position of the baffles is related to the importance of buoyancy force. As a result, effects of inlet Reynolds and Froude numbers on the strength of buoyancy force are studied for a secondary settling tank and the results show that neither Reynolds nor...
Numerical simulation of collision between two droplets in the T-shaped microchannel with lattice Boltzmann method
, Article AIP Advances ; Volume 6, Issue 11 , 2016 ; 21583226 (ISSN) ; Ebrahimi, S ; Moosavi, A ; Shafii, M. B ; Kowsary, F ; Sharif University of Technology
American Institute of Physics Inc
Abstract
In this study, the Lattice Boltzmann Method (LBM) is used to investigate the deformation of two droplets within microfluidic T-junctions (MFTD). In order to increase the accuracy the two immiscible fluids are modeled using the He-Chen-Zhang model. First, this model is applied to ensure that the surface tension effect existing between the droplets and the continuous fluid is properly implemented in the model. Then the collision and merging of the two droplets within the intersection of a T-shaped microchannel is investigated. For generating droplet formation the effects of relevant dimensionless parameters such as the Reynolds, the Weber numbers as well as a collision parameter affecting the...
Effect of bubble size and angle of tapered upriser pipe on the effectiveness of a two phase lifting pump
, Article 2009 ASME Fluids Engineering Division Summer Conference, 2nd August 2009 through 6 August 2009 ; Volume 1, Issue PART B , 2009 , Pages 807-814 ; 9780791843727 (ISBN) ; Saidi, M. H ; Zamiri, A ; Karimi, A ; Sharif University of Technology
2009
Abstract
Two phase lifting pumps are devices with the ability of lifting liquid phase by injecting the gas phase. Parameters which affect the performance of these pumps are divided into two groups. The first group contains design parameters such as diameter of the pipe, tapering angle of the upriser pipe and the submergence ratio which is the ratio of immersed length to the total length of the upriser. The second group includes operating parameters, such as the gas flow rate, bubble diameter, bubble distribution and inlet gas pressure. In this research, the performance of two phase lifting pump is investigated numerically for different submergence ratios and different diameter of the upriser pipe....
Physical aspects of rarefied gas flow in micro to nano scale geometries using DSMC
, Article 39th AIAA Fluid Dynamics Conference, 22 June 2009 through 25 June 2009, San Antonio, TX ; 2009 ; 9781563479755 (ISBN) ; Darbandi, M ; Mirjalili, V ; Schneider, G. E ; Sharif University of Technology
Abstract
Rarefied gas flow in micro/nano electro mechanical systems (MEMS/NEMS) does not perform exactly as that in macro-scale devices. The main goal in this study is to investigate mixed subsonic-supersonic flows in micro/nano channels and nozzles and to provide physical descriptions on their behaviors. We use DSMC method as a reliable numerical tool to extend our simulation. It is because the DSMC provides accurate solution for the Boltzmann equations over the entire range of rarefied flow regime or Knudsen numbers. As is known, the appearance of oblique/normal shocks at the inlet of a channel or a nozzle adds to the complexity of internal flow field analyses. We found some very unique physical...