Master Degree / Yüksek Lisans Tezleri

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

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Author: search.filters.author.Çelik, Hasan

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  • Master Thesis
    Numerical Investigations of Flash-Boiling Gasoline Direct Injection Sprays
    (Izmir Institute of Technology, 2019) Oral, Orhan; Barışık, Murat; Barışık, Murat; Çelik, Hasan
    Gasoline Direct Injection (GDI) system is a new technology that is the combination of injection in diesel engines and ignition in gasoline engines. Comparing with the conventional methods of injection, it has many advantages including, fuel economy, higher engine power, lower engine knock tendency, NOx and cold-start HC emission rates. The operation of the GDI engine is affected by the processes of fuel injection, spray atomization and vaporization, charge cooling, air/fuel mixture preparation, and incylinder charge motion. Therefore, numerical modeling has an important role to improve all these factors affecting the engine. This thesis focuses on numerical analyses of the fuel sprays injected into a constant volume chamber by a single hole GDI injector under flash-boiling and non-flashboiling conditions. The aim of this thesis is to develop a numerical model that can be used in flash-boiling spray simulations and to validate the results of the numerical model against experimental data in terms of spray angle and spray penetration. Initially the GDI sprays were simulated by the standard spray simulation model of OpenFOAM solver package that was tuned for gasoline injections. Then the model was modified for both non-flashing and flashing spray simulations and the results were compared with experimental ones. It is concluded that; discharge coefficient and spray initial angle have critical impacts on the numerical results.
  • Master Thesis
    A Study on Mixed Convection Heat Transfer Through a Channel Partially Filled With Porous Medium
    (Izmir Institute of Technology, 2012) Çelik, Hasan; Mobedi, Moghtada
    A study on mixed convection heat transfer in a laminar, fully developed, vertical channel is performed for three different cases: i) clear fluid channel ii) saturated porous medium filled channel iii) partially porous medium filled channel. For the all analyzed cases, motion and heat transfer equations are solved both analytically and numerically. The governing equations are presented both in dimensional and dimensionless forms. The dimensional forms of the governing equations are solved by numerical method while dimensionless equations are solved analytically. The dimensional results, obtained by numerical method, are converted into dimensionless values and compared with dimensionless results of analytical solutions. Good agreement between analytical and numerical results is observed. Based on the obtained results, velocity and temperature profiles are plotted for different values of Gr/Re, Da and porous layer thickness. A detailed discussion is performed on the obtained results. Moreover, heatline functions are obtained and plotted for different values of Gr/Re, Da and Peclet number. It is found that flow reversals in the channel highly depends on Gr/Re value and flow reversals occurs in the channel if Gr/Re exceeds threshold value. It is also found that for low Peclet numbers (i.e., Pe = 0.01), the path of heat flow is independent of Gr/Re and Darcy number. However, for high Peclet numbers (i.e., Pe = 5), the ratio of Gr/Re, Darcy number and thermal conductivity ratio influence heatline patterns, considerably.