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    Numerical Analysis of An Annular Gas Turbine Combustor

    , M.Sc. Thesis Sharif University of Technology Gandomi, Mohammad Hossein (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar... 

    Large Eddy Simulation of Supercritical Swirling Flow of Injector in a Combustion Chamber

    , Ph.D. Dissertation Sharif University of Technology (Author) ; 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... 

    Study of Cryogenic LOX/Kerosene Ignition and Flame Characteristics in a Single injector Combustion Chamber

    , M.Sc. Thesis Sharif University of Technology Eskandari, Mohammad Amin (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    This thesis discusses design and, simulation procedure of a mono-injector combustion chamber, in order to study and, analyze the ignition and, stable combustion characteristics, for Kerosene and, liquid Oxygen cryogenic propellants. Accordingly, the design and, simulation for the combustion chamber, for Kerosene and, liquid Oxygen propellants is performed. Also, effective parameters on the flame taking place are studied, and finally an algorithm for design and, properties study of cryogenic propellant ignition is presented  

    Dynamic behavior Analysis of a Swirl Burner using Recurrence Plotting Method

    , M.Sc. Thesis Sharif University of Technology Talebi, Mohammad Sadegh (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    In this dissertation, based on the method of recurrence plot and its application in dynamic system analysis we examine the behavior and dynamic analysis of a swirl burner. Though retrospective studies on thermoacoustic instability have been performed on single-blown premixed cone shape flames and several combustion systems but so far this method has not been considered for a real combustion system. There have also been more work on phenomena known as the flame separation from the burner (blowout) and its propagation into the burner (flashback), which is almost conscious of their process. In fact, selecting a single flame has been to eliminate the flame-flame interactions in the... 

    Study of the Effects of Mass Fraction and Flow Velocity Fluctuations on Diffusion Flame

    , M.Sc. Thesis Sharif University of Technology Khosousi, Ali (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    In this work, the unsteady response of a laminar diffusion flame to harmonic mass fraction oscillations and also to flow velocity fluctuations is investigated. Flame-sheet assumption is utilized to model the laminar unsteady two-dimensional co-flow diffusion flame mathematically. The initial combustion of most combustion chambers is through diffusion mechanism. Therefore, developing analytical model of diffusion combustion is of great importance. The flow is assumed subsonic (incompressible), inviscid, and uniform. The convection-diffusion equation for conserved scalar variable with appropriate boundary conditions is solved. Considering stoichiometric mass fraction surface to be the flame... 

    Investigation of Premixed V-shaped Flame Response to Acoustic Oscillations

    , M.Sc. Thesis Sharif University of Technology Nabatian, Negar (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Low emissions combustion V-flame combustors are exceptionally prone to combustion instabilities. These systems for land based gas turbines rely on a premixed or partially premixed combustion process. As V-flames do not anchored on the lip of combustor, an experimental study of the transfer function of these flames shows that they are more sensitive to fuel oscillations and in the range of frequencies, they behave like an amplifier. This paper presents an experimental study of the transfer function of a ducted, laminar, premixed V and M-flames. V-flame, laminar, propane/air premixed flame stabilised at the rim of the burner. The limit of M and V-flame are identified without excitation, then... 

    Experimental Study of Low Swirl Burners Interferences

    , M.Sc. Thesis Sharif University of Technology Shahsavari, Mohammad (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    One of the problems associated with lean premixed combustion is their stability. Low swirl flame is a modern technology for reducing NOx emissions and increasing stability.In this thesis, first, the effect of geometric parameters on the flame stability was investigated. This study was carried out in high fuel and oxidizer mixture flow rate. Having find, the most stable burner, two other burners with the same geometrical parameters were built. Stability of these three burners were analyzed. Second, they were located in a ring together in three different relative positions. In each configuration stability and NOx emissions of the burners were determined.The study shows that NOx and CO... 

    Investigations on Stability of Premixed Flames in Turbine Engines

    , Ph.D. Dissertation Sharif University of Technology Riazi, Rouzbeh (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    This thesis is a complementary experimental and theoretical investigation on stability of premixed flames and a study of combustion instability and combustion dynamics in a swirl-stabilized combustor, aiming to understand the fundamental mechanisms responsible for combustion oscillations in gas turbine combustors. Theoretical investigations on acoustic modeling of a simple combustor and a study on kinematic response of premixed flames to flow perturbations have been discussed in the first part of this work. In another part of thesis, experimental studies on the response of premixed flames to acoustic perturbations have been performed. In addition, experimental investigations on combustion... 

    Experimental Study of Flame Stability on a Reheat System

    , M.Sc. Thesis Sharif University of Technology Nozari, Hadi (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    In conventional afterburning systems, the burnt products of the primary combustion enter the afterburning zone, where the fuel is injected and the mixture is ignited to form a flame which is stabilized by a flameholder.
    The present experimental study focuses on concepts of afterburning and flame stability in a reheat system. For this purpose an afterburner setup is designed and manufactured. The setup comprises of two main regions; the preheating region and the reheat zone. Fuel used in preheater is LPG while jet fuel is injected in reheat zone. Through the tests the key parameters which are adjusted to be in similar ranges as the conventional afterburners are the oxygen amount of the... 

    Unsteady Analysis of a Slinger Combustion Chamber by the Chemical Reactor Network Model

    , M.Sc. Thesis Sharif University of Technology Soroush, Fariborz (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Up to early seventies, Gas turbine combustor design was very time consuming and costly process including trial and errors through test rigs. Over the time analytical-experimental relationships take place as one of the key rules in the design processes. With the increasing power of computer calculations, computational fluid dynamics find its way in the procedure. Obtaining a deeper understanding of flow conditions and geometry inside the chamber, a great reduction in production time and cost of revisions to rigs and samples were achieved. Finding a precise prediction of polluting elements like NOx (less than 10 ppm) after many run hours and enormous computing resources, CFD methods must... 

    Numerical Study of Accelerating Flame and Flame-Sound Interaction in Tubes

    , M.Sc. Thesis Sharif University of Technology Jafari, Samira (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Numerical study of the interaction mechanism of the premixed flame and the acoustic field is performed in this work. The geometry similar to those used in experiments, is a two-dimensional tube in which flame travels form open end towards the closed end. The numerical study is done using PPM method. Results show that the shape and speed of laminar flame is strongly affected by the induced acoustic field. Stronger interaction is observed in the closed-end tube with no slip boundary conditions. The effect of the Lewis number on the interaction mechanism is also investigated. Premixed flame- accelerated flame – interaction of flame and acoustic field  

    Numerical Investigation of Laminar Premixed Flame Response to Acoustic Excitation

    , M.Sc. Thesis Sharif University of Technology Behzadi, Milad (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Flame Response to acoustic excitation which plays an important role in combustion chamber stability state may be found through numerical simulation. A finite volume code of higher order accuracy developed for compressible flows was adopted. Species equations along with a single-step irreversible reaction model were added to this non-reacting program. Changes were also made to the energy equation. Premixed methane/air flame in tubes was studied and the same problem was solved with FLUENT software. It was found that whether the Lewis number is considered constant or temperature dependent has a strong effect on flame structure and shape and that using mean values for gas properties yields out... 

    Aeroacoustic Simulation of Rod-Airfoil Noise

    , M.Sc. Thesis Sharif University of Technology Yazdani, Mostafa (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Wall systems are an essential part of the buildings and their capacity should be properly considered in their design. However, the seismic behavior of building systems with in-filled walls and their interaction is a very complex issue, yet to be understood. Using the in-filled walls in the buildings without including them in the design process changes the whole behavior of the structural system as well as their failure mechanism under earthquake excitations. On the other hand, there have been extensive researches on rehabilitation of the structures with in-filled walls or designing them as the main or one of the lateral load carrying systems against seismic input. In this research, first the... 

    Numerical Analysis of an Afterburner Combustion Stability

    , M.Sc. Thesis Sharif University of Technology Rezaei, Vahid (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Inlet flow of afterburners comes from the burnt products of the primary combustion chamber. The fuel is injected and the mixture is ignited to form a flame which is stabilized behind a flameholder in the afterburner. Flame stability stems from wake (recirculation zone) of flameholder. With the aid of high residence time of flow behind the flameholder reactants get the time to catch activation energy. Some parameters like oxygen content, mass flow rate, inlet temperature, and nozzle area ratio play an important role in afterburner combustion efficiency and flame stability. In this study we focused on afterburner combustion stability in GE J85-21 engine. This engine will be in service through... 

    Numerical Study of Spray Formation in Slinger Injection

    , M.Sc. Thesis Sharif University of Technology Karimi, Hamed (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    In this M.S. dissertation numerical study of slinger fuel distributer has been studied. This type of atomizer has been used in mini turbojets like Teledyne CAE.
    The main purpose of this work was obtaining spray structure of slinger atomizers. This goal was achieved by implementing a UDF code in FLUENT® software to model the primary atomization that include variation of fluid from exit of slinger disk bores till formation of primary droplet. In FLUENT® the DPM method and its ability to utilizing Lagrangian approaches have been used. The result of this model is validated by the data from experimental test that can be found in Articles. This is the first time that spray structure of slinger... 

    Experimental Study on Liquid Breakup Process in Slinger Injection

    , M.Sc. Thesis Sharif University of Technology Rezayat, Sajjad (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    In small turbojet engines, it is important to find a suitable fuel injector with good spray quality. However, the rotating fuel injection system can potentially provide high atomization quality without the high-pressure fuel pump through the centrifugal forces of the engine shaft. The spray characteristics of rotary atomization for small gas turbines can be investigated using a high-speed camera. To analyze the breakup process of the liquid column and liquid film, spray visualization tests should performed under varied test conditions.In this research, experimental study on liquid breakup process has performed in rotary atomizer of j402 turbojet engine with the name of slinger injector, to... 

    Numerical Simulation of Cellular Structure of Detonation Wave and Evaluation of Linear Instability Analysis

    , Ph.D. Dissertation Sharif University of Technology Barkhordari, Alireza (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Experimental studies of regular cell structure of a weak detonation wave in a gaseous mixture of hydrogen and oxygen diluted with argon have shown that for a constant initial thermodynamic condition, the final cell size differs by repeating the tests. The question is that if these different final cell sizes for a constant initial condition are because of test errors, or the experiments would lead to a domain of solution in the form of different final cell sizes? Therefore, the aim of this study is to investigate, numerically, the evolution process and domain of variation of cellular structure of a weak detonation, and their dependency to unstable wavelengths obtained from linear instability... 

    Large Eddy Simulation of Excited Jet Flow

    , Ph.D. Dissertation Sharif University of Technology Ghadimi, Masoud (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Excited jet flow has many physical and industrial applications, e.g. in aeroacoustics and the combustion instability. Analysis of this type of flow needs an accurate simulation of flow dynamics. This work presents the large eddy simulation of this type of flow. The numerical method used in the large eddy simulation must have low numerical dissipation and high order of accuracy. Compact methods which satisfy these requirements and have high resolution of frequency, are favorable ones for the large eddy simulation. A fourth-order compact finite volume method which had been developed in the MSc thesis of the author is extended and completed in the present work. This extension includes the... 

    Numerical Simulation of A Vortex Cooled Combustion Chamber

    , M.Sc. Thesis Sharif University of Technology Azardar, Milad (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    The aim of the present research is to investigate the combustion chamber cooling with vortex method in presence of kerosene and liquid oxygen as propellants. For this purpose, a part of oxidizer is entered into the cylindrical combustion chamber tangentially (from bottem of the chamber), and creates a vortex flow (outer vortex). With motion of created outer vortex along the wall and eventually hit its top wall (the head of the chamber), secondary vortex (inner vortex) occurs along the center line, with a downward direction (opposite to the primary vortex). The fuel and other part of the oxidizer injection is also carried in the head of chamber, so by mixing the fuel and oxidizer that happens... 

    Detail Design of a Supercritical Injection Tester, Based on Numerical Simulation of the Spray Structures under Supercritical Conditions

    , M.Sc. Thesis Sharif University of Technology Pourmahmoud, Ataollah (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Based on the results of a cryogenic swirl flow numerical simulation under supercritical conditions, a global injection tester has been designed. For numerical simulation of the injection process by using ANSYS FLUENT as the CFD solver, the full 3D flowfield has been meshed by a fully structure manner. k-ω(SST) has been used as the turbulence model which has been captured many of the swirl cryogenic flow structures in the both steady and unsteady conditions. Also, the modified Soave-Redlich-Kwong EOS has been accommodated in a broad range of supercritical pressures for estimating state functions, thermodynamic properties and transport properties. The results show that increasing ambient...