Spatio-Temporal Behavior of End-Wall Film Cooling of a Turbine Vane with Purge Flow Measured by Fast-Response Pressure-Sensitive Paint

The demand for high-efficiency, low-emission gas turbines has intensified with growing global energy consumption. In modern turbines, elevated inlet temperatures and uniform combustor-exit profiles expose the first-stage vane endwall to severe thermal loads. Complex vortex structures, such as horseshoe and secondary vortices, further enhance local heat transfer, making effective endwall cooling essential. This study investigates the combined cooling effects of film cooling and purge flow on the endwall of a turbine vane using a low-speed linear cascade. The influences of blowing ratio (BR), mass flow ratio (MFR), and density ratio (DR) on film cooling performance were systematically examined. A fast-response polymer–ceramic pressure-sensitive paint (PC-PSP) and a high-speed camera were employed to capture time-resolved film cooling effectiveness distributions. Results show that cooling effectiveness peaks at BR = 1.00 and decreases at higher BR due to excessive jet penetration. Increasing MFR broadens the purge flow and enhances lateral coverage, while higher DR suppresses jet penetration and promotes wall attachment, though pitch-averaged effectiveness slightly declines. Time-resolved data reveal streak-like RMS patterns linked to vortex interactions. Dominant spatial modes and their temporal variations are analyzed using spectral proper orthogonal decomposition (SPOD).