Parametric Optimization of Film Cooling Hole Geometry

Abstract

In this study, a combination of computational simulation and experimental testing was used to evaluate a broad range of forward and lateral expansion angles for a turbine film cooling shaped holes. The study demonstrates the utilizing of RANS based CFD to quickly screen potential optimized geometries, followed by experimental determination of true performance characteristics. As a baseline, the performance of all film cooling holes was evaluated using an internal coolant channel cross-flow. Also, all hole geometries incorporated a filleted inlet-plenum interface, which presumes use of additive manufacturing to construct the turbine components. Experimental validation confirmed that the computational simulations predicted the correct relative performance of various hole geometries, even though actual performance levels were not predicted well. This investigation showed that the performance of laidback, fan shaped holes was much more sensitive to the lateral expansion angle than the forward expansion angle. The optimum shaped hole configuration was found to be a hole with a 15° lateral expansion angle and a 1° forward expansion angle (15-15-1 configuration), which had a maximum average adiabatic effectiveness 40% greater than the baseline 7-7-7 open literature hole. This study also showed that the shaped hole diffuser performance is primarily a function only three parameters: the coolant jet velocity ratio, VR, the shaped hole area ratio, AR, and the hole exit width relative to the pitch between holes, t/P.