Utilization of the Transient Liquid Crystal Technique for Film Cooling Effectiveness and Heat Transfer Investigations on a Flat Plate and a Turbine Airfoil

Abstract

The transient liquid crystal technique has been used to measure film cooling effectiveness and heat transfer on a flat plate in a free jet, and a turbine airfoil in a linear cascade. A multiple-test regression method has been developed for the data reduction, considering a transient coolant temperature evolution. Flat plate film cooling was investigated for a single row of 35° inclined holes at Mach numbers of 0.3 and 0.5, and two turbulence intensities. Downstream of injection heat transfer was increased in-between the holes due to enhanced turbulence caused by the shearing of the coolant and the mainstream. At higher turbulence intensity the range of blowing ratios was broader as lift-off was delayed. Rim cooling measurements on the airfoil were conducted at engine-representative flow conditions. A maximum effectiveness of 0.3 behind injection was observed on the suction side, with slightly higher values for a double row in comparison to a single row configuration. Due to a high coolant momentum, the effectiveness on the pressure side was very low at about 0.05 for a single row configuration.