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Modeling of Turbulent Combustion at Supercritical Condition, Using Flamelet Based Models
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Turbulent combustion at supercritical condition have a considerable effect in modern high performance rocket propulsion systems, gas turbines and diesel engines. In such a reaction conditions, an abrupt changes occur in thermodynamics and transport properties of fluid. So numerically modeling of a real fluid behavior of the cryogenic propellants and the turbulent trans-critical mixing and combustion processes faces serious challenges.In this study, in order to realistically represent turbulence–chemistry interactions, detailed chemical kinetics and real-fluid thermodynamic behaviors related to the gaseous hydrogen and cryogenic liquid oxygen combustion under supercritical pressures, the...
Study on Pretreatment of the Uranous Effluents of the UCF & Natanz Plants by Using Supercritical Water Method
, M.Sc. Thesis Sharif University of Technology ; Otoukesh, Mohammad (Supervisor) ; Ahmadi, Javad (Co-Advisor)
Abstract
Pretreatment of nuclear waste for valuable and limited uranium resources in the nuclear industry as well as environmental protection is imperative. Wash the affected parts of the Natanz uranium enrichment plant uranium centrifuges with a standard cleaning solution of citric acid, a liquid waste is generated in this study, the preparation of these residues using supercritical water oxidation (SCWO) and near critical (HTWO1) was studied as a result, the optimum operating conditions, and conditions of solvent extraction has been studied. In the result, the optimum operating conditions, and conditions of solvent extraction has been introduced. Also in the UCF2 as a liquid waste contaminated with...
Large Eddy Simulation of Supercritical Swirling Flow of Injector in a Combustion Chamber
, Ph.D. Dissertation Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
In the present thesis, the extensive study of reactive and non-reactive supercritical and transcritical flows has been discussed in shear-axial and swirling forms. Considering the need for combustion models with the application of detailed chemistry for accurate simulation of the field, the Laminar Flamelet Models (LFM) are suitable in order to reduce computational expensive. For this purpose, it is necessary to produce thermodynamic tables specific to real gas conditions for the flamelet model. The tables related to the flamelet model in real gas conditions are extracted from the open source software Cantra. The difference point in the Flamelet tables of real gas and ideal gas is for...
Prediction of phase equilibrium of CO2/cyclic compound binary mixtures using a rigorous modeling approach
, Article Journal of Supercritical Fluids ; Vol. 90 , 2014 , pp. 110-125 ; ISSN: 08968446 ; Soroush, E ; Shokrollahi, A ; Bahadori, A ; Sharif University of Technology
Abstract
Vapor liquid equilibrium (VLE) data has significant role in designing processes which include vapor and liquid in equilibrium. Since it is impractical to measure equilibrium data at any desired temperature and pressure, particularly near critical region, thermodynamic models based on equation of state (EOS) are usually used for VLE estimating. In recent years due to the development of numerical tools like artificial intelligence methods, VLE prediction has been find new alternatives. In the present study a novel method called Least-Squares Support Vector Machine (LSSVM) used for predicting bubble/dew point pressures of binary mixtures containing carbon dioxide (CO 2) + cyclic compounds as...
Thermal-hydraulic analysis of HPLWR fuel assembly cluster
, Article Journal of Supercritical Fluids ; Volume 77 , May , 2013 , Pages 91-99 ; 08968446 (ISSN) ; Salehi, A. A ; Jahanfarnia, G ; Sharif University of Technology
2013
Abstract
The High-Performance Light Water Reactor (HPLWR) is the European version of the Supercritical-pressure Water Cooled Reactor (SCWR). Light water reactors at supercritical pressure, being currently under design, are the new generation of nuclear reactors. The present article is a thermal-hydraulic analysis of the HPLWR fuel assembly cluster. The existing thermal hydraulic codes are not capable of analyzing and designing the HPLWR fuel assembly. It is necessary to introduce a new thermal-hydraulic code that can incorporate the parameters and specifications of the HPLWR fuel assembly. The governing equations include energy, mass and momentum equations beside thermal-hydraulic equations are...
Supercritical synthesis and characterization of graphene-pbs quantum dots composite with enhanced photovoltaic properties
, Article Industrial and Engineering Chemistry Research ; Volume 54, Issue 30 , 2015 , Pages 7382-7392 ; 08885885 (ISSN) ; Tavakoli, M. M ; Outokesh, M ; Shafiekhani, A ; Simchi, A ; Sharif University of Technology
American Chemical Society
2015
Abstract
Lead sulfide quantum dots (PbS QDs) were decorated onto a graphene surface in a semi-core-shell structure using supercritical ethanol. The temperature of ethanol played significant role in controlling size and agglomeration of QDs as well as the extent of reduction of graphene. Average size of the QDs was estimated by transmission electron microscopy to be around 3.96 nm and by quantum models to be about 4.34 nm. PbS QDs prepared at 330 °C were of high purity, and the yield was 99%. Instrumental and chemical analyses demonstrated formation of a strong bond between PbS QDs and graphene, through a Pb-O-C bridge. UV and photoluminescence measurements along with theoretical considerations...
Linear yukawa isotherm regularity for dense fluids derived based on the perturbation theory
, Article Fluid Phase Equilibria ; Volume 409 , 2016 , Pages 105-112 ; 03783812 (ISSN) ; Farrokhpour, H ; Parsafar, G. A ; Sharif University of Technology
Elsevier
2016
Abstract
In the present work, the thermodynamic of dense fluids, both compressed liquids and dense supercritical fluids, has been modeled, solely, based on the contribution of attraction of effective pair potential. The intermolecular interaction is modeled by the hard-core Yukawa potential (HCY) as an effective pair potential (EPP) with temperature dependent hard-core diameter. Using this EPP in the exact thermodynamic relations, an equation of state (EoS) for the compressibility factor of dense fluid has been derived. This EoS shows that (Z - ZCS) as function of ρ1/3 must be linear for each isotherm of fluid where ZCS is the compressibility factor of the reference fluid (Carnahan-Starling (CS) EoS)...
Hydrogen-deuterium chemical exchange in supercritical water: Thermodynamic considerations for optimizing the synthesis of high degree deuterated benzene
, Article Journal of Supercritical Fluids ; Volume 125 , 2017 , Pages 96-103 ; 08968446 (ISSN) ; Hosseinpour, M ; Mohammadnezhad, F ; Ahmadi, S. J ; Khazayi, M. A ; Sharif University of Technology
Abstract
In the light of the novel physical-chemical properties of supercritical water as a green reaction medium, we studied the synthesis of deuterated benzene in supercritical heavy water, in the presence of sodium deutroxide, as a catalyst. The effects of operational parameters including temperature, time, pressure (density), catalyst amount and benzene/D2O volumetric ratio on the degree of deuteriation (D%) and deuterated benzene yield were investigated extensively and the conditions for the highest degree of deuteration and product yield, were optimized. Furthermore, because of the importance of the pressure of solution inside the reaction medium on the H/D exchange process as well as the...
Measurement and correlation of CO2 solubility in the systems of CO2 + toluene, CO2 + benzene, and CO2 + n-hexane at near-critical and supercritical conditions
, Article Journal of Chemical and Engineering Data ; Volume 51, Issue 6 , 2006 , Pages 2197-2200 ; 00219568 (ISSN) ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
2006
Abstract
The solubility of CO2 in the systems of CO2 + benzene, CO2 + n-hexane, and CO2 + toluene was meticulously measured at (293.15, 298.15, and 308.15) K and different pressures using a pressure-volume-temperature (PVT) apparatus. Also the effect of pressure on the solubility of CO2 in the organic solvents used in this work was investigated. The Peng-Robinson equation of state (PR EOS) with only one temperature-independent binary interaction parameter was used in correlating the experimental data. The results showed that the PR EOS can accurately correlate the experimental data for the solubility of CO2 in the organic solvents at high pressure. In case of the systems CO2 + benzene and CO2 +...
Experimental investigation of shock-buffet criteria on a pitching airfoil
, Article Chinese Journal of Aeronautics ; Volume 35, Issue 7 , 2022 , Pages 179-191 ; 10009361 (ISSN) ; Zeinalzadeh, A ; Abdi, M. A ; Soltani, M. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
An experimental investigation of the shock-buffet phenomenon subject to unsteady pitching supercritical airfoil around its quarter chord has been conducted in a transonic wind tunnel. The model was equipped with pressure taps connected to the fast response pressure-transducers. Measurements were conducted at different free-stream Mach number from 0.61 to 0.76. The principle goal of this investigation was to experimentally discuss the shock-buffet criterion over a SC(2)-0410 supercritical pitching related to the hysteresis loops of total drag and trailing edge pressure, the behaviour of the shock wave foot location, the pressure distribution over the upper surface, and by implementing the...
Symmetric and asymmetric performance investigation of a diverterless supersonic inlet
, Article AIAA Journal ; Volume 60, Issue 5 , 2022 , Pages 2850-2859 ; 00011452 (ISSN) ; Soltani, M. R ; Sharif University of Technology
AIAA International
2022
Abstract
A series of wind-tunnel tests were conducted on a Y-shaped diverterless supersonic inlet (DSI) in order to investigate its performance at various operating conditions. The present DSI was designed for a freestream Mach number of M∞ 1.65. The experiments were performed at supercritical, critical, and subcritical operating conditions and at 0 deg angle of attack and angle of side slip. The results showed that the present DSI had an acceptable performance at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions. At low subcritical operating conditions, the supersonic flow pattern remained symmetric too. However, at high...
A simple granulation technique for preparing high-porosity nano copper oxide(II) catalyst beads
, Article Particuology ; Volume 9, Issue 5 , 2011 , Pages 480-485 ; 16742001 (ISSN) ; Outokesh, M ; Hosseinpour, M ; Mousavand, T ; Sharif University of Technology
Abstract
A simple and efficient method was developed for fabricating spherical granules of CuO catalyst via a three-step procedure. In the first step, copper oxide nanoparticles were synthesized by hydrothermal decomposition of copper nitrate solution under supercritical condition. Then, they were immobilized in the polymeric matrix of calcium alginate, and followed by high-temperature calcination in an air stream as the third step, in which carbonaceous materials were oxidized, to result in a pebble-type catalyst of high porosity. The produced CuO nanoparticles were characterized by transmission electron microscopy (TEM) that revealed an average size of 5 nm, X-ray diffractometry (XRD), and thermo...
The role of co-solvents in improving the direct transesterification of wet microalgal biomass under supercritical condition
, Article Bioresource Technology ; Volume 193 , October , 2015 , Pages 90-96 ; 09608524 (ISSN) ; Vossoughi, M ; Pazuki, G ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In this research, direct conversion of wet algal biomass into biodiesel using supercritical methanol was studied. In this process, microalgal lipids simultaneously was extracted and converted to biodiesel under high pressure and temperature conditions without using any catalyst. Several experiments have been performed to optimize the methanol amount and it has been revealed that the best performance was achieved by using methanol/wet biomass ratio of 8:1. The effect of using various co-solvents in increasing the efficiency of the supercritical process was investigated. It has been shown that hexane was the most effective co-solvent and its optimal ratio respect to wet biomass was 6:1. The...
Preparation of new titanium nitride-carbon nanocomposites in supercritical benzene and their oxygen reduction activity in alkaline medium
, Article Electrochimica Acta ; Volume 164 , May , 2015 , Pages 114-124 ; 00134686 (ISSN) ; Ghorbani, M ; Dolati, A ; Yashiro, H ; Outokesh, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Titanium nitride-carbon nanocomposites are synthesized by the reaction of TiCl4 and NaN3 in supercritical benzene medium that also serves as a carbon source. The as-prepared precursors (SI, SII) are subjected to several heat treatments (SIII-SV). The synthesized nanoparticles are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The samples are tested as electrocatalyst for oxygen reduction reaction in an alkaline electrolyte. It is shown that the electrocatalytic properties of the synthesized nanoparticles are...
Supercritical synthesis and in situ deposition of PbS nanocrystals with oleic acid passivation for quantum dot solar cells
, Article Materials Chemistry and Physics ; Volume 156 , 2015 , Pages 163-169 ; 02540584 (ISSN) ; Simchi, A ; Aashuri, H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Colloidal quantum dot solar cells have recently attracted significant attention due to their low-processing cost and surging photovoltaic performance. In this paper, a novel, reproducible, and simple solution-based process based on supercritical fluid toluene is presented for in situ growth and deposition PbS nanocrystals with oleic-acid passivation. A lead precursor containing sulfur was mixed with oleic acid in toluene and processed in a supercritical fluid condition at different temperatures of 140, 270 and 330 °C for 20 min. The quantum dots were deposited on a fluorine-doped tin oxide glass substrate inside the supercritical reactor. Transmission electron microscopy, X-ray diffraction,...
Fractional factorial design for the optimization of hydrothermal synthesis of lanthanum oxide nanoparticles under supercritical water condition
, Article Journal of Supercritical Fluids ; Volume 52, Issue 3 , 2010 , Pages 292-297 ; 08968446 (ISSN) ; Abolghasemi, H ; Moosavian, M. A ; Golzary, A ; Ghannadi Maragheh, M ; Sharif University of Technology
2010
Abstract
In this research, synthesis of lanthanum oxide nanoparticles using supercritical water as a reaction medium in batch type reactor was studied. The crystallographic identity and morphology of the synthesized nanoparticles were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate that the well-crystallized lanthanum oxide nanocrystals can be easily obtained under the current synthetic conditions. The effect of four parameters includes temperature, reaction time; primary concentration of aqueous solution of lanthanum (III) nitrate and pH of starting solution on reaction efficiency, particle size and the BET surface area were investigated...
Biodiesel production from Spirulina microalgae feedstock using direct transesterification near supercritical methanol condition
, Article Bioresource Technology ; Volume 239 , 2017 , Pages 378-386 ; 09608524 (ISSN) ; Karimi Sabet, J ; Ghotbi, C ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Microalgae as a candidate for production of biodiesel, possesses a hard cell wall that prevents intracellular lipids leaving out from the cells. Direct or in situ supercritical transesterification has the potential for destruction of microalgae hard cell wall and conversion of extracted lipids to biodiesel that consequently reduces the total energy consumption. Response surface methodology combined with central composite design was applied to investigate process parameters including: Temperature, Time, Methanol-to-dry algae, Hexane-to-dry algae, and Moisture content. Thirty-two experiments were designed and performed in a batch reactor, and biodiesel efficiency between 0.44% and 99.32% was...
Numerical Simulations of the Coaxial Shear and Swirl Injectors’ Cryogenic Flowfields under Trans- and Supercritical Conditions
, Ph.D. Dissertation Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Characterizing the dynamics dictating injection and mixing of the coaxial shear and swirl injectors is of central importance in the context of space rockets, diesel and direct injection reciprocating engines, and modern turbine gases. Sophisticated with precise thermo-physical models along with high-fidelity turbulence approaches, a computational platform –based on OpenFOAM open source code– is developed to simulate the practical injectors flow-fields under trans- and supercritical conditions. Aiming at providing a deep insight on the underlying physics, the investigations are conducted in a hierarchical manner; the flow complexities are added step-by-step to eventually construct the...
Application of response surface methodology for optimization of paracetamol particles formation by RESS method
, Article Journal of Nanomaterials ; Volume 2012 , 2012 ; 16874110 (ISSN) ; Ghotbi, C ; Dorkoosh, F ; Sharif University of Technology
2012
Abstract
Ultrafine particles of paracetamol were produced by Rapid Expansion of Supercritical Solution (RESS). The experiments were conducted to investigate the effects of extraction temperature (313353K), extraction pressure (1018MPa), preexpansion temperature (363403K), and postexpansion temperature (273323 K) on particles size and morphology of paracetamol particles. The characterization of the particles was determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Liquid Chromatography/Mass Spectrometry (LC-MS) analysis. The average particle size of the original paracetamol was 20.8m, while the average particle size of paracetamol after nanonization via the...
Supercritical gasification of biomass: Thermodynamics analysis with Gibbs free energy minimization
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 34, Issue 2 , Dec , 2011 , Pages 163-176 ; 15567036 (ISSN) ; Pazuki, G. R ; Vossoughi, M ; Saboohi, Y ; Hashemi, N ; Sharif University of Technology
2011
Abstract
Gasification of biomass in supercritical water is a successful technology for hydrogen production especially by using wet biomass. The whole process, from feeding to purification of hydrogen, consists of a lot of equipment, such as pumps, heat exchangers, heaters, reactors, etc. Because the main reactions take place in the gasification reactor, the gasifier is the most important equipment of the process. In this article, a thermodynamic model, including chemical equilibrium in the reactor that is based on Gibbs free energy minimization, is developed to estimate equilibrium composition for gasification of biomass in supercritical water for hydrogen production. For this analysis, we use three...