Improving Turbine Endwall Overall Cooling Effectiveness Using Curtain Cooling and Redistributed Film-Hole Layouts: An Experimental and Computational Study

To enhance the cooling deficiency that occurs in a baseline endwall using axially-arranged cooling holes, this paper proposes a new locally-enhanced hole layout using curtain cooling and fan-shaped film holes being arranged on iso-Mach lines. The objective of cooling hole redesign is to minimize secondary flows and thus to provide better film coverage. In experiments, infrared thermography techniques are applied to validate overall cooling effectiveness of the newly-designed endwall, and aero-thermal fields at the cascade exit are detected by five-hole and thermocouple probes. Additionally, computational fluid dynamic simulations are performed to provide complementary flow insights. A comparison with the baseline hole layout reveals that for a given total coolant flowrate, the newly-designed endwall significantly improves the cooling performance by up to 27% without a noticeable aerodynamic penalty, resulting in a lower and more uniform temperature field. Curtain coolant effectively suppresses the development of horseshoe vortex and provides adequate thermal protection for leading-edge junctures and pressure-side corner regions. The redistribution of fan-shaped film holes reinforces the cooling performance in the passage throat and trailing-edge regions. At low and high total mass flowrates, the coolant split between various cooling sources has a substantial impact on cooling performance.