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Description
One of the limiting factors for the advance of gas turbines has been the turbine inlet temperature. Advancements in efficiency gas turbines engines are often measured by increasing level of turbine inlet temperature and rising optimal compressor pressure ratio. To overcome these limiting factors, a big focus has been on new schemes of internal cooling designs of turbine blades, using pressurized air from the engine compressor. The challenge related to improving the efficiency come with the need to maximize the efficiency of the internal cooling of the turbine blade to withstand the high turbine inlet temperature. Understanding the fluid mechanics and heat transfer of internal blade cooling is therefore of paramount importance. This dissertation presents the impact of vortex flow cooling on the heat transfer of a gas turbine blade cooling passage to understand the mechanics of internal blade cooling. The vortex flow is generated through continuous injection of tangential flow. The experimental investigation is presented first with 3-D Stereo-Particle Image Velocimetry (Stereo-PIV) and second Thermochromic Liquid Crystal (TLC). The study provides an evaluation of the developments of vortex cooling methodology utilizing 3-D Stereo-PIV and TLC. The objective of the experimental models is to determine the critical swirl number that has the potential to deliver the maximum axial velocity results with the highest heat transfer at three different Reynolds numbers, 7,000, 14,000, and 21,000. Additionally, a 3-D domain fluent setup employing a steady-state pressure-based solver with a standard k-epsilon turbulence model was applied. The cyclindrical chamber with seven air inlets with elbow produced the optimum results. As part of the results relatively low heat transfer rates were observed near the upstream end of the cylindrical chamber, resulting from a low momentum vortex flow as well as crossflow effects. The TLC heat transfer results exemplify how the Nusselt Number (Nu) measured favorably at the midstream of the chamber. Experimental results are consistent with the Computational Fluid Dynamics analysis (CFD) results. Introducing air through the inside of the blade utilizing seven air inlets can remove as much heat from the blade surface, increasing heat transfer, and subsequantly increasing turbine rotor inlet temperature.
