TURBINE PLATFORM COOLING AND BLADE SUCTION SURFACE PHANTOM COOLING FROM SIMULATED SWIRL PURGE FLOW

The paper presents the swirl purge flow on platform and a modeled land-based turbine rotor blade suction surface. Pressure sensitive paint (PSP) mass transfer technique provides detailed film cooling effectiveness distribution on platform and phantom cooling effectiveness on blade suction surface. Experiments have completed in a low speed wind tunnel facility with a five blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Swirl purge flow is simulated by coolant injection through fifty inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes go through nozzle endwall and a dolphin nose axisymmetric contour before reach platform and blade suction surface. Different "coolant injection angles" and "coolant injection velocity to cascade inlet velocity" results in various swirl ratios to simulate real engine conditions. Simulated swirl purge flow uses coolant injection angles of 30, 45, and 60 degrees to produce swirl ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has coolant injection angle of 90 degree to generate swirl ratio of 1. Coolant to mainstream mass flow rate ratio (MFR) is 0.5%, 1.0% and 1.5% for all swirl ratios. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Most of the swirl purge and purge coolant approaches platform, but small amount of the coolant migrates to blade suction surface. Swirl ratio of 0.4 has highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffer from apparent decrement of the effectiveness while increasing relative motion.