Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.İnal, FikretCOAR Access Rights: search.filters.coarAccessRights.open access

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Now showing 1 - 5 of 5
  • Master Thesis
    Effects of Methanol on Species Concentrations in N-Heptane Flames
    (Izmir Institute of Technology, 2019) M. Alazreg, Abdalwahab Rashed; İnal, Fikret
    Fuel oxygenate additives have been used as an alternative method to reduce the combustion emissions. The effects of methanol addition on n-heptane oxidation were investigated for one-dimensional, atmospheric pressure, laminar, premixed, fuel-rich flame at an equivalence ratio of 2.10. The Detailed Chemical Kinetic Modeling approach has been used to obtain information about the combustion characteristics of n-heptane and n-heptane/methanol flames. A detailed chemical kinetic mechanism was generated by merging two mechanisms of n-heptane (with the formation of polycyclic aromatic hydrocarbons (PAHs)) and methanol. The Master Mechanism consists of 4480 reactions and 945 species. Model validation was carried out using the experimental data available in the literature for different combustion systems. The Master Mechanism was investigated for the combustion of n-heptane and n-heptane/methanol flames using reaction sensitivity, rate of production, and reaction pathway analyses. The mole fraction profiles of low-molecular-weight stable species, single ring aromatics, and PAHs have been predicted by the model. Good agreements between the modeling and experimental results of species mole fractions for both flames have been achieved. The mole fractions of low-molecular-weight species, aromatics, and PAHs were reduced as the methanol was added to n-heptane flame. Acetylene, propargyl radical, and vinylacetylene have been found as important species for the formation of the first aromatic ring and PAH species. Model reduction was also carried out using directed relation graph method. The Reduced Mechanism consists of 1113 reactions and 156 species. The Reduced Mechanism was in a good agreement with the Master Mechanism in terms of the species mole fraction predictions of the n-heptane/methanol flame.
  • Master Thesis
    Detailed Chemical Kinetic Modeling of N-Heptane Flame
    (Izmir Institute of Technology, 2018) Değirmenci, Emre; İnal, Fikret
    To understand the complex combustion characteristics of gasoline, n-heptane is used as one of the two major reference fuels. The emissions resulted from incomplete combustion are one of the main issues caused from usage of high amount of fossil fuels in transportation and energy generation sectors. The main purpose of this study is to model one-dimensional premixed, laminar, burner-stabilized fuel-rich n-heptane flame to understand its combustion characteristics in mainly fuel-rich conditions. Detailed chemical kinetic modeling technique was used to get high amount of information about the ignition characteristics of n-heptane and formation nature of emissions. A detailed chemical kinetic mechanism was generated by combining several mechanisms from the literature that related with possible products of fuel-rich n-heptane combustion. The detailed mechanism consists of 4185 reactions and 893 species. Validations of the model were done with various experimental data available in the literature such as premixed laminar flames and jet stirred reactors. After generating the kinetic model, detailed investigation of the n-heptane flame was done by using rate of production, reaction sensitivity and reaction pathway analyses. One of the attributes of fuel-rich flames, Polycyclic aromatic hydrocarbon (PAH) formation kinetics were also investigated. Acetylene (C2H2), propargyl radical (C3H3), and vinylacetylene (C4H4) were found as the main precursors of the first aromatic ring and PAH formation as a result of pathway and rate of production analyses. The generated model was able to predict most of the major, minor and trace components that formed in the flame that modeled. A reduced model was also generated by using directed relation graph with error propagation (DRGEP) mechanism reduction technique on the detailed mechanism. The reduced mechanism consists of 1879 reactions and 359 species. The species mole fraction predictions of detailed and reduced mechanism were very close to each other. Most of the species formed in the flame were predicted by the reduced mechanism with less computational afford than detailed mechanism.
  • Master Thesis
    Investigation of Fuel Oxygenate Adsorption on Clinoptilolite Rich Natural Zeolite
    (Izmir Institute of Technology, 2006) Yetgin, Senem; İnal, Fikret
    The wide use of fuel oxygenates in gasoline as anti-knocking and emission reduction agent have recently led to serious environmental concerns due to their detection in groundwater and surface water. Among the various gasoline additives, methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) are the most frequently used fuel oxygenates worldwide. Due to the physical and chemical properties of fuel oxygenates, the conventional treatment technologies are generally ineffective for their removal from contaminated water. Adsorption is a common process frequently used to remove fuel oxygenates from water. The use of natural zeolites as adsorbent have increased significantly because of their availability and low cost. Clinoptilolite is one of the most abundant zeolites in nature, and Turkey has very large clinoptilolite reserves. In this project the adsorption properties of clinoptilolite rich natural zeolites for use in the removal of MTBE and ETBE from water have been investigated using batch equilibrium and fixed-bed column experiments. The adsorption properties have been compared with those of two activated carbons (i.e., Powdered Activated Carbon (PAC) and Granulated Activated Carbon (GAC)). In addition, bisolute (i.e., benzene and oxygenate) adsorption experiments were also carried out to determine the effectiveness of these adsorbents in the presence of other gasoline hydrocarbons. All the experiments were performed at 25 °C with initial oxygenate and benzene concentrations of 2000 ppb and 400 ppb, respectively. In batch equilibrium experiments, it has been found that the powdered and granulated activated carbons had higher adsorption capacities for MTBE and ETBE than clinoptilolite. The highest capacity for the amount of MTBE adsorbed per unit mass of adsorbent was achieved using GAC while that of ETBE was obtained using PAC. The presence of benzene decreased the adsorption capacities of GAC and PAC. However, the effect of benzene was not clear and was dependent on the adsorbent loading for clinoptilolite. In fixed-bed column experiments, GAC and clinoptilolite were tested as adsorbents. The column breakthrough curves for clinoptilolite were steep indicating fast adsorption and narrow mass transfer region. For GAC, mass transfer regions were wider due to the relatively flat breakthrough curves. There was no significant effect of benzene on the breakthrough curves for GAC and clinoptilolite.
  • Master Thesis
    Hydrogen Production From Ethanol Over Silica Supported Cu and Zn Oxide Catalysts
    (Izmir Institute of Technology, 2006) Tezel, Habibe Işıl; İnal, Fikret
    The majority of current energy needs are supplied by combustion of nonrenewable energy sources such as fossil fuels, which is associated with release of large quantities of greenhouse gases, especially carbon dioxide and other harmful emissions to the atmosphere. The gradual depletion of these fossil fuels reserves and efforts to combat pollution and greenhouse gas emissions have generated a considerable interest in using alternative sources of energy. Ethanol used in the hydrogen production process by steam reforming. The purpose of this work was to design a high performance catalyst for the production of hydrogen from steam reforming of ethanol. Ethanol steam reforming reaction is an endothermic reaction of ethanol with water to produce hydrogen and carbon dioxide. The different ZnO loading supported SiO2 catalyst and Cu promoted ZnO/SiO2 catalysts were prepared single step sol-gel method with different Cu loading. All catalysts were characterized by X-ray diffraction, BET surface area measurements and pore diameter analysis. BET surface area decreased and average pore diameter increased as the ZnO loading increased. Based on the XRD findings, it seems that zinc silicate crystallite phase is not formed under the preparation conditions used in this dissertation. The activity and selectivity tests of all catalysts were performed in a packed bed reactor with reaction temperature between 300 and 500oC. The performances of ZnO/SiO2 catalysts in ethanol steam reforming reaction were investigated as a function of ZnO loading. Cu catalysts are known as active catalysts for ethanol dehydrogenation. As the temperature was increased, the conversion increased and reached a maximum at 500oC for all Cu loadings.
  • Master Thesis
    Effects of Dimethyl Ether on N-Butane Oxidation
    (Izmir Institute of Technology, 2011) Bekat, Tuğçe; İnal, Fikret
    Effects of dimethyl ether on the oxidation of n-butane were investigated using Detailed Chemical Kinetic Modeling approach. Oxidation process was carried out in a tubular reactor under laminar flow conditions. The formations of various oxidation products, especially toxic species were investigated for the addition of dimethyl ether in different mole fractions to n-butane. Pure dimethyl ether oxidation was also investigated for comparison. Pure dimethyl ether oxidation resulted in lower mole fractions of carbon monoxide, methane, acetaldehyde and aromatic species, but higher mole fractions of formaldehyde when compared to pure n-butane oxidation. The addition of dimethyl ether to n-butane in different mole fractions was observed to decrease mole fractions of acetaldehyde and aromatic species and increase the mole fraction of formaldehyde, while other toxic species investigated were not affected significantly. The effects of three important process parameters on the formations of oxidation products were also investigated. Inlet temperatures between 500 and 1700 K, pressures of 1 and 5 atm, and equivalence ratios of 2.6 and 3.0 were studied. Increasing pressure and equivalence ratio were observed to increase the mole fractions of toxic species in general. The effect of temperature was more complicated depending on the species and the temperature interval. Reaction path analysis indicated that the most important precursors playing role in the formation of the first ring benzene were acetylene, ethylene, propargyl, allene, allyl, propene and fulvene during n-butane/dimethyl ether oxidation. Finally, a skeletal chemical kinetic mechanism was developed and validated for the oxidation of n-butane/dimethyl ether mixture.