<p dir="ltr">This research presents a culmination of work into uncovering the underlying fluid dynamic behaviors of supercritical CO2 as it relates to high pressure turbine design using a combined fundamental and practical numerical and experimental analysis. The fundamental analysis of the thermo-fluid dynamic properties of supercritical CO2 boundary layers and separation is analyzed against the air counterparts for non-dimensional quantities of interest – pressure ratio, Mach number, Reynolds number – and combinations of these quantities. The coupling of density derivatives with pressure and temperature are investigated within the operating conditions of the first stage turbine of a supercritical CO2 oxyfuel power cycle. Armed with the information garnered from this analysis, a 3D optimization is run using computational fluid dynamics to investigated nearly 3000 unique blade shapes, focusing on increasing the isothermal corrected efficiency and decreasing the heat load to the blade. Three different families of blade shapes are identified from the analysis and their aerodynamic qualities discussed. A single advanced blade design is chosen for in depth analysis and experimental testing against the baseline blade from which the optimization was started. Mechanical design for the experimental campaign in the Big Rig for Aerothermal Stationary Turbine Analysis (BRASTA) is presented for a novel sector-based off-axis design and the results of the aerothermal measurements discussed. In tandem with blade design and analysis, the Tip Gap Experimental Research Article for Large Scale Injection Layouts (Tiger Lily), a canonical model for the large-scale investigation of tip flows in high Reynolds number flows, is developed and the mechanical and aerodynamic design discussed. Aerothermal analysis for different tip coolant injection configurations is performed using Improved Delayed Detached Eddy Simulation (IDDES) computational fluid dynamics analysis to resolve turbulent structures resulting from coolant injection and over tip flow interaction. Experimental investigation of Tiger Lily is presented, validating the structures and features seen in the numerical analysis. The conclusion of these investigations results in the increased understanding of the underlying fluid dynamic behaviors of supercritical CO2 in high pressure turbines.</p>