Infrared Heat Transfer Coefficient Measurements in an Engine-Scaled Turbine Stage

Abstract This article presents full-field heat transfer coefficient measurements using infrared thermography in an engine-scaled, partially cooled turbine stage in the NG-Turb facility at DLR Göttingen. The work was carried out as part of the European Commission-funded FACTOR programme. Full-field heat transfer coefficient measurements are needed to account for the effects of combustor turbulence, hot spot location, and migration on turbine stage heat transfer, which remain a challenge for state-of-the-art design methods. Measurements were made on stationary vanes and struts and in the rotating frame of the blades. The work utilizes a traditional transient measurement method and a novel phase-based technique. The phase-based technique exploits the phase shift between oscillating fluid and wall temperatures, which varies with local heat transfer coefficient. Compared to the traditional transient method, the phase-based approach enhances spatial resolution by an order of magnitude, increases robustness against measurement noise and calibration errors, and lowers the heating power input. The measurement methodology is described in detail and full-field Nusselt numbers are presented on a film-cooled nozzle guide vane, a rotor blade, and a low-pressure strut. The conditioning of the measurements allows them to resolve the effects of film cooling injection, shock-boundary layer interaction, boundary layer transition, and tip leakage flow on local heat transfer coefficients.