A Frequency Domain Analysis: Turbine Pressure Side Heat Transfer

Abstract

Simultaneous time-resolved surface heat flux and velocity measurements have been made along the pressure side of an engine-similar turbine blade in a linear cascade. Direct heat flux was measured using inserted Heat Flux Microsensors at three axial locations along the high turning transonic blade. Miniature hot-wires measured velocity above these locations. Grids produced two turbulence fields with different inlet length scales at constant turbulence intensity. This work allows a unique look at fluctuating heat transfer on the blade and its relationship to the fluctuating velocity field above. While fluctuating free-stream flow energy and length scale decays continuously in the passage, surface heat flux energy increases continuously. Low frequency flow energy is attenuated in the constricted passage, while growth of low frequency energy in the heat flux is attributed to boundary layer transition activity. Coherence between heat flux and velocity is seen at all frequencies near the leading edge of the blade but only at higher frequencies farther downstream on the pressure side. Existing mean heat transfer correlations do not perform well in this complicated flow.