Turbine Platform Cooling and Blade Suction Surface Phantom Cooling From Simulated Swirl Purge Flow

Abstract

This paper presents the swirl purge flow on a 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 the platform and phantom cooling effectiveness on the blade suction surface. Experiments were conducted 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 50 inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes pass through nozzle endwall and a dolphin nose axisymmetric contour before reaching the platform and blade suction surface. Different “coolant injection angles” and “coolant injection velocity to cascade inlet velocity” result in various swirl ratios to simulate real engine conditions. Simulated swirl purge flow uses coolant injection angles of 30 deg, 45 deg, and 60 deg to produce swirl ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has a coolant injection angle of 90 deg to generate swirl ratio of 1. Coolant to mainstream mass flow rate (MFR) ratio is 0.5%, 1.0%, and 1.5% for all the swirl ratios. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Most of the swirl purge and purge coolant approach the platform; however, a small amount of the coolant migrates to the blade suction surface. Swirl ratio of 0.4 has the highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffers from apparent decrement of the effectiveness while increasing relative motion.