Master Degree / Yüksek Lisans Tezleri

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

Browse

Filters

20153

Settings

Has files: YesSubject: search.filters.subject.CFD

Search Results

Now showing 1 - 3 of 3
  • Master Thesis
    Experimental Investigation of Gdi Injectoer
    (Izmir Institute of Technology, 2015) Abuzahra, Fakhry; Rodriguez, Alvaro Diez
    Among the challenges in the internal combustion - spark ignition Gasoline Direct Injection (GDI) engines stayed under spotlight for its ability to be developed in terms of fuel conversion efficiency and emission contaminants. Spray analysis is of great importance for the combustion operation and it is a prerequisite for improving the mixing capabilities of the air/fuel mixture. Momentum flux measurement technique is one of the most interesting approaches that aims to study the spray structure which can be a complement for high-speed imaging and Phase Doppler Anemometry (PDA) analysis. In the present study, two GDI single-hole research injectors, Magneti Marelli with Length to Diameter parameter (L/D)=1; 3 are investigated by means of momentum flux, global and local, under both low and high temperatures. The flash-boiling phenomenon is triggered when static pressure is below fuel saturation pressure at the same temperature which drastically affects the spray structure in terms of decrement in the penetration rate accompanied with an enlargement in the cone angle. N-heptane is used as a fuel under a temperature range 30-120 C, vessel ambient pressure range 40 303 KPa ,energizing time 1500 -3000 distance for the global momentum 5--40 mm and two horizontal planes for local momentum flux 10; 30 mm. Results of high-speed imaging were integrated in terms of cone angle and penetration rate. Furthermore, the results of this study can verify the Computational Fluid Dynamic (CFD) numerical analysis and provide wealthy understanding of the spray evolution.
  • Master Thesis
    Numerical Study on Gasoline Direct Injection Sprays
    (Izmir Institute of Technology, 2015) Güleç, Yağmur; Diez, Alvaro; Mobedi, Moghtada
    Gasoline direct injection technology is a combination of the advantages of diesel engine and spark ignition engines. Hence, the gasoline fuel is injected directly to combustion chamber. It provides finer atomization to allow evaporation more rapidly than traditional gasoline engines and less emissions in terms of NOx and particulate than diesel engines. The understanding of spray behaviour is a significant point to control optimal air/fuel mixture and misfiring. This thesis presents a numerical investigation of a GDI injector under flash and non-flash boiling conditions. The study is performed with sprays injected into a constant volume chamber. The purpose of the thesis is to develop a CFD model to compare it with experimental spray penetration and spray angle results. Firstly, the model is validated in terms of spray penetration. Secondly, the model is applied to nine different conditions including flash and non-flash boiling conditions. The spray penetration and angle comparisons between numerical and experimental results were done.
  • Master Thesis
    Investigation of Oil Flow and Heat Transfer in Transformer Radiator
    (Izmir Institute of Technology, 2015) Kaymaz, Özben; Başaran, Tahsin; Erek, Aytunç
    Transformer losses are produced by the current passing through resistance on the winding conductors. These losses are converted to heat energy as all electrical machines. Transformer life depends on the aging of cellulose-based insulation material in winding. Winding temperature must be kept below a certain temperature limit, because the excess heat in the windings directly accelerates the aging of insulation material. Oil-immersed transformers are cooled by using transformer oil. In this study, flow and heat transfer of transformer radiator filled with mineral oil, silicone oil and ester oil were investigated. Oil in radiator was modelled in 3D, thereby oil flow volume was created, heat transfer calculations were made with using different type transformer oils and investigation of flow behavior is studied. Temperature dependent density, thermal conductivity and viscosity values are obtained from oil suppliers. Transformer oil database was composed by using curve fitting methods in MathCAD Software to use in CFD (Computational Fluid Dynamics) analysis in Fluent software. Finally, the pressure differences were obtained for each oil type. According to the velocity versus pressure difference graph that was obtained from the results of this study, inertial resistance and viscous resistance could be described which are required in future studies to use porous medium approach. Number of elements and computation domain will be decreased by using porous medium approach, then complete transformer model could be analyzed. Additionally, thermal characteristics of transformer oils were obtained and compared in this study. Accordingly, natural ester oil had the best heat transfer and pressure drop.