Browsing by Subject "Gambit"
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Item Labyrinth Seal Leakage Analysis(2012-10-19) Inam, OrcunAnnular seals are devices used in turbomachinery to avoid flow losses which reduce efficiency. The dynamic stability of the machine is also improved by the seal. Thus, it is an important subject to understand the flow behavior through the seal. Straight through triangular labyrinth seals are one of the most commonly used types of non-contacting annular seals. The energy dissipation through these seals is achieved by a series of teeth and cavities. As the flow passes above each tooth, a portion of its pressure energy is converted into kinetic energy. A portion of this kinetic energy is dissipated through turbulence-viscosity interaction in the cavity that follows. Moreover, some portion of the pressure energy is also lost through viscosity of the fluid. This research aims to understand the effects of flow parameters and seal geometry on these losses. This will make it possible to estimate the mass flow leakage through the seal. ANSYS Fluent is used to simulate the flow through the seal. The effect of seal geometry is studied by varying clearance, pitch, tooth height, tooth width and upstream side angle. It was found that, amongst other geometrical parameters, tooth clearance and pitch has a strong influence on carryover coefficient. Smaller values of c/s have better kinetic energy dissipation in the cavity. Carryover coefficient is also found to be a function of the Reynolds number and shaft speed. Discharge coefficient of the seal presents the overall efficiency while carryover coefficient only shows the cavity performance. Discharge coefficient is also found to be a strong function of tooth clearance, pitch, Reynolds number and shaft speed. Remaining parameters have smaller effects. It was observed that the discharge coefficient of first tooth is always lower than those of intermediate teeth. The compressibility effects are presented by using an expansion factor which is the ratio of compressible flow discharge coefficient to incompressible flow discharge coefficient. It was found that the expansion factor is fairly independent of geometrical parameters but a strong function of flow parameters. Considering the effects of seal geometry and flow parameters on carryover coefficient, discharge coefficient and expansion factor, the seal geometry is optimized to increase the kinetic energy dissipation and pressure head loss which in turn will reduce the mass flow leakage.Item Numerical Investigation of Temperature Distribution on a High Pressure Gas Turbine Blade(2014-08-10) Zirakzadeh, HootanA numerical code is developed to calculate the temperature distributions on the surface of a gas turbine blade. This code is a tool for quick prediction of the temperatures by knowing the boundary conditions and the flow conditions, and doesn?t necessarily provide the most accurate results that could be obtained by performing an experiment or precise CFD simulations. Different systems of blade external and internal cooling, such as rib turbulated cooling, impingement cooling, pin-fins, and injection holes for film cooling, are considered in the code by using the appropriate correlations or factors. When the code is run and the results are obtained a gas turbine blade designer can modify his blade terms and conditions such as mass flow rate, number of injection holes in each passage, even the blade material thickness to find an optimum design for cooling purposes. Code is first applied to an E? blade; the external heat transfer coefficients for this blade is inserted as a known boundary condition; Next, code is run for the same blade but this time using the flat plate and convectional correlations for predicting transition on suction side of the blade for external heat transfer coefficient. This code provides an easy way to get a better understanding of the cooling design and its ability to be modified for any gas turbine blade makes it more flexible to be developed as a commercial tool in future. In the next step, code is applied to a Samsung-Rotor2 blade with different cooling design than an E? blade and results are presented. Another part is introduced to this project by running a CFD simulation using commercial software Fluent and Gambit, to capture heat transfer coefficient distributions around the surface of the blade and the obtained values is used back in the code. In the meanwhile some interesting observations made during the CFD simulation is discussed. The CFD simulation is performed for the cases where there are not any data available for external heat transfer coefficient distribution already. Two turbulence models, k-epsilon and SST-Transition were utilized for the 2D CFD study; and for the 3D CFD case, only k-epsilon model was applied. It was revealed that even though SST- Transition has a better prediction of Mach number, but in terms of heat transfer coefficient k-epsilon model provides closer values to the reference values from previous works. Finally, combining the code and the CFD results could act as a useful assistant to give a designer a general and quick idea of how his blade design will perform at the end.