A STEADY TRANSONIC LINEAR CASCADE FOR TRUE SCALE COOLING MEASUREMENTS

The design and benchmarking measurements for a steady, transonic linear cascade for film cooled airfoils are presented. The facility holds up to 11 true scale turbine airfoils with high span to chord ratio for two-dimensional flow at the airfoil midspan. Mainstream air is continuously supplied by a compressor, while desiccant dried air is used as the cooling flow to match coolant-to-mainstream density ratios. The cooling system supplies three airfoils, each with independent circuits, to enable parametric studies of cooling with periodicity for central airfoils. Independent Mach and Reynolds number control at steady conditions is achieved by using control valves and a bypass loop. Incidence angle studies can be performed by using a turntable and modular guide wall system. Optical windows include a zinc selenide window for spatially resolved surface temperature measurements using infrared thermography, as well as glass windows for flowfield measurements using laser-based diagnostics. The infrared camera setup enables a 360 degree view around the surface of the central airfoil. For laser-based diagnostics, laser sheets can be delivered to the central airfoil through glass inserts in the guidewalls. Current benchmarking results include static pressures on the blade surface and endwall, inlet boundary layer, and freestream turbulence measurements at various Mach numbers, Reynolds numbers, and incidence angles. Results indicate excellent periodicity over a wide range of conditions. Near term work in the facility will investigate film cooling at transonic conditions for a representative modern blade geometry.