Turbine Blade Surface Phantom Cooling from Upstream Nozzle Trailing-Edge Ejection

This paper presents upstream nozzle trailing-edge coolant ejection on downstream uncooled blades. A pressure-sensitive paint mass transfer technique provides detailed phantom cooling effectiveness distribution on modeled land-based turbine rotor blade surfaces. Without cavity purge and tip leakage flows, a uniform blade inlet temperature is adopted in the current study. Experiments have been completed in a low-speed wind-tunnel facility with a five-blade linear cascade. The inlet Reynolds numbers based on chord length are 100,000 and 200,000. Nozzle trailing-edge coolant ejection on a rotor blade is simulated by a spoked-wheel-type rotating facility with 32 hollow rods equipped with coolant ejection from 128 holes per rod. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Nozzle coolant discharge velocity to nozzle mainstream velocity ratio varies from 0.4 to 1.4. Velocity ratios from 0.4-0.6 are closest to typical engine conditions. Coolant to mainstream mass flow rate ratio effect is from 0.67 to 2.94%. Higher phantom cooling effectiveness occurs on suction and pressure surfaces at the velocity ratio of 0.4-0.6 and over 1.0, respectively. Velocity ratio effect impacts phantom cooling effectiveness distribution more than the mass flow rate ratio effect. Most of the trailing-edge coolant migrates toward blade inner and outer spans than the blade midspan.