Influence of mainstream turbulence on turbine blade platform cooling from simulated swirl purge flow

The paper presents the combined effect of mainstream turbulence intensity and swirl ratio on the cooling performance of turbine blade platform and suction surface. Pressure sensitive paint (PSP) mass transfer technique provides detailed cooling effectiveness distribution on platform and suction surface. Experiments have been 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. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Detailed mainstream turbulence intensities for test are Tu (%) = 0.72, 3.1, 6, 8.2, and 13. Swirl ratios (S) of 1 presents without rotation effect but 0.4 simulates high relative motion between rotor and coolant to represent rotation effect. Coolant to mainstream mass flow rate ratios are MFR (%) = 0.5, 1.0 and 1.5. Results show that elevated mainstream turbulence intensity increases cooling effectiveness in general. Best cooling performance is observed for high mainstream turbulence intensity of 13% cases no matter with or without rotation effect. Rotation effect reduces coolant capability at higher MFR of 1% and 1.5% cases for tested mainstream turbulence intensities.