NUMERICAL AND EXPERIMENTAL INVESTIGATION OF TURNING FLOW EFFECTS ON INNOVATIVE PIN FIN ARRANGEMENTS FOR TRAILING EDGE COOLING CONFIGURATIONS

The effect of the array configuration of circular pin-fins is investigated from a numerical and experimental point of view reproducing a typical cooling scheme of a real high pressure aero-engine blade. The airstream enters the domain of interest radially from the hub inlet and exits axially from the trailing edge (TE) outlet section. More than one hundred turbulators are inserted in the wedge shaped TE duct to enhance the heat transfer: a reference array implementing 7 rows of staggered pins is compared with an innovative pentagonal arrangement. Investigations were made considering real engine flow conditions: both numerical calculations and experimental measurements were performed fixing Re=18000 and Ma=0.3 in the TE throat section. The effect of the tip mass flow rate was also taken into account, investigating 0% and 25% of the TE mass flow rate. The experimental activity was aimed at obtaining detailed heat transfer coefficient maps over the internal pressure side (PS) surface by means of the transient technique with thermochromic liquid crystals. Particle Image Velocimetry measurements were performed and surface flow visualizations were made by means of the oil&dye technique on the PS surface. Steady-state RANS simulations were performed with two different CFD codes: the commercial software Ansys CFX (R) 11.0 and an in-house solver based on the opensource toolbox OpenFOAM (R), to compare the performance and predictive capabilities. Turbulence was modeled by means of the k - omega SST model with an hybrid near wall treatment allowing strong clustering of the wall of interest as well as quite coarse refinement on the other viscous surfaces.