Understanding Turbine Cooling Physics
Film Cooling
The use of film cooling in gas turbines creates the opportunity to operate at higher temperatures, resulting in greater power and efficiency. At ExCCL, much of our recent film cooling research has looked at how film cooling effectiveness is affected by various deviations from the targeted shape. To do this the 7-7-7 film cooling hole was developed by Penn State, taking into consideration over 120 different geometries creating a baseline that represents current film cooling technologies. The 7-7-7 shaped hole has been used to study how meter-diffuser misalignment and thermal barrier coating buildup influence the film cooling effectiveness, as well as the unique flowfield of compound angle shaped holes.
IR and PIV data for an angled 7-7-7 film cooling hole
Non-axisymmetric Endwall Contouring
Three-dimensional shaping of the endwall of a gas turbine is known to reduce aerodynamic loss, but the heat transfer and cooling impact is also important in the hot section of an engine. We have studied industry-relevant geometries to determine the aerothermal impact of contouring. Results like shown on the right indicate important changes to local heat transfer that need to be considered in the design.
Heat transfer coefficient augmentation on a 3D contoured endwall
Improving Heat Transfer Predictions with High Fidelity CFD
High fidelity computational fluid dynamics methods such as Large Eddy Simulation (LES) are time consuming, but can significantly improve prediction accuracy. We are investigating computational models that bridge the gap between design turnaround time and prediction accuracy, particularly for convective heat transfer. This will enable turbine designers to push the limits of turbine performance, with more confidence in their design.
Video of instantaneous heat transfer on the endwall of a turbine blade, calculated using large eddy simulation.