Investigation of an adjoint optimized film cooling hole under varying operating conditions

In recent studies, a turbine film cooling shaped hole designed by adjoint optimization techniques (X-AOpt) was found to have substantially increased film cooling performance. This thesis investigated the X-AOpt film cooling hole under varying operating conditions, to include experimentation with geometry variations of the hole itself and integration into a multirow configuration to model the pressure side of a turbine airfoil. Two aspects of the X-AOpt hole's geometry contribute to its improved cooling effectiveness: the shape of the internal geometry (which improves the diffuser performance) and the external protrusions (which generate counter rotating vortices that laterally spread the coolant more effectively over the surface of the model airfoil). Results from experimental evaluations of the X-AOpt hole with the external protrusions removed showed that 40% of the improvement in film cooling effectiveness is due to the internal geometry, and 60% of the improvement is due to the external protrusions. Variations in lateral spacing, or pitch, of the X-AOpt holes provided further insight into the optimized interaction of the counter rotating vortices generated by the hole's external protrusions. The X-AOpt hole was then integrated into a multirow configuration, where it was evaluated in both adiabatic and overall cooling effectiveness experiments. The improvements in film cooling effectiveness from the implementation of the X-AOpt hole were characterized, and a superposition analysis was completed to compare actual performance to predicted performance.