59780 - Cfd Evaluation of Turbine Blade Leading Edge Film Cooling With Varying Shaped Hole Geometries 

In gas turbine engines, the highest heat loads occur at the leading-edge areas of turbine blades and vanes. To protect the blades and vanes, a “showerhead” configuration of film cooling holes is often used for this location, in which several rows of holes are configured closely together to maximize film coverage. Typically, these film cooling holes are fed by impingement cooling jets, which enter the internal coolant chamber and impinge on the inner surface of the leading edge. This impingement helps to cool the leading edge internally, but also changes the internal flow field, affecting the coolant flow through the film cooling holes and thus the film cooling performance. The effects of this internal flow field on film cooling are not well known, and experimental research is very limited in its ability to analyze them, particularly the flow inside the film cooling holes. Because of this, computational fluid dynamic (CFD) simulations were used as a way to analyze these internal flow fields and their effects. To isolate the effects of the impingement jet, results were compared to a pseudo-plenum internal feed. Computational showerhead blade models were created with both a realistic impingement feed and a pseudo-plenum feed, and then simulated using RANS. The models were created to match as closely as possible with experimental blade models that had been studied previously. The RANS simulations were also run for both configurations with the wall thermal conductivities adjusted so that the Biot numbers matched those expected at real engine conditions. This allowed determination of overall cooling effectiveness which includes internal cooling effects. Performance was primarily analyzed by looking at adiabatic effectiveness contours on the blade surface, thermal fields normal to the blade surface, and the flow fields inside of the film cooling holes. Computational results from both configurations were compared to experimental results for the same configurations, obtained in an earlier study. The CFD RANS results were found to follow the same trends as the experimental results for both the impingement-fed and plenum-fed cases, suggesting that RANS is able to accurately model some of the important physics associated with leading-edge film cooling. This led to the conclusion that CFD may be used as a tool to analyze the effects of internal flow fields on film cooling when experimental methods cannot.