Doctor of Philosophy (PhD)
At a fixed pressure ratio, the thermodynamic efficiency and net power output of a gas turbine engine increases with an increase in the turbine inlet temperature. Cooling is necessary because of the thermal limits of the engine materials. This research studies through experimentation, the heat transfer and cooling of critical gas turbine components including the shroud and blade tip. In the first phase, the shroud heat transfer behavior and the effectiveness of shroud cooling under the conditions of rotation is undertaken in a single stage turbine at a design rotation speed of 550 rpm, at off-design speeds and for varying cooling configurations and injection methods. At the design speed, as the blowing ratio is increased, the normalized Nusselt number in the shroud hole region decreases. At the off-design speeds, the results show that the high Nu/Nu0 region migrates on the shroud surface. This migration affects the coolant coverage in the shroud hole region. The slot cooling study shows increasing cooling effectiveness up to a blowing ratio of 1.25 followed by a drop off in the cooling effectiveness with blowing ratio due to jet lift off. In the second phase of this investigation, the heat transfer and film cooling of a gas turbine blade tip with a blade rotation speed of 1200 rpm have been studied. The heat transfer results for the no coolant injection show a region of high heat transfer on the blade tip near the blade leading edge region. This region of high heat transfer extends and stretches on the tip as more coolant is introduced through the tip holes at higher blowing ratios. The tip film cooling profile is such that the tip coolant is pushed towards the blade suction side due to the effects of blade relative motion. Cooling the blade tip using coolant injection from the shroud holes and slots in combination with tip injection results in better overall cooling coverage of the blade tip with the shroud hole and blade tip cooling combination being the most effective. The level of coolant protection is strongly dependent on the blowing ratio and combination of blowing ratios.
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Tamunobere, Onieluan, "Heat Transfer and Film Cooling on a Gas Turbine Blade and Shroud" (2015). LSU Doctoral Dissertations. 3331.