Rotor / Stator Heat Transfer Measurements and CFD Predictions for Short-Duration Turbine Rig Tests

Abstract

This paper describes aerodynamic and heat transfer measurements, improved data analysis techniques, and CFD predictions for an extensive series of high-pressure turbine tests carried out in a large-scale, short-duration test facility. The focus of this work is on the test methods, aerodynamic and heat transfer instrumentation, and the heat flux data obtained on the HPT blade and vane pressure and suction surfaces, and on the blade platform. Heat transfer data are presented along three spanwise stream surfaces, and at five platform locations, for two Reynolds numbers, and for three different initial blade temperature levels. An analytical method for improving the interpretation of transient heat flux gage measurements and estimating the uncertainties in heat transfer coefficients is applied based on test facility characteristics, established 2D boundary layer heat transfer theory, and a detailed calculation of the transient temperature response of the heat flux gages as installed in the airfoils. The result is a systematic procedure for improved data reduction and correction of bias errors resulting from in-situ heat flux gage behavior in complex rotating rig tests. Three-dimensional aerodynamic calculations are compared with time-averaged unsteady pressure measurements on the airfoils. Boundary-layer heat transfer predictions are shown to be in fair agreement with the pitchline data but sensitive to assumptions regarding free-stream turbulence, uncertainties in inlet conditions, and variations in the applied surface Mach number distribution. Finally, full 3D heat transfer computations for the blade are discussed, with an emphasis on capturing overall 3D flow effects with sufficient accuracy for practical turbine airfoil cooling design. The results suggest that advanced analysis techniques, including 3D CFD, can be used effectively to compute not only mean values of the surface heat transfer coefficients, but also to quantify the uncertainties in the predictions and to identify the dominant sources of those uncertainties. This is an important step in creating a robust turbine cooling design process that accounts for environmental, manufacturing, and modeling variations. Future papers will present experimental and computational results for the blade tip and shroud, the vane endwalls, and TBC-coated airfoils.