Integrated Combustor - Turbine Design for Improved Aerothermal Performance : Effect of Dilution Air Control

The effect of dilution air control in a combustor on the heat load distribution of an axial turbine with non-axisymmetric endwall profiling is examined. Endwall profiling is a more common design feature in new engine types, due to the effectiveness of the endwall profiling in reducing secondary flows, and their associated losses. In the present work, the effect of dilution air control is examined by using two different circumferentially non-uniform hot-streak shapes; the two cases differ in their spanwise extents either side of the stator, and therefore represent different approaches for dilution air control. This numerical study details the impact of these two different strategies for dilution air control on the rotor blade heat load distribution. The inlet boundary conditions simulate the experiment that is conducted in the axial research turbine facility "LISA" at ETH Zurich. A circumferential non-uniformity in the spanwise migration pattern of the hot streak inside the stator is observed. Even though this circumferential non-uniformity in the spanwise migration is alleviated by the non-axisymmetric endwall profiling, the two hot-streak cases result in considerably different heat load distributions on the rotor blade, emphasizing the importance of the integrated combustor - turbine approach. Finally, the implications for dilution air control on the liner are discussed for the realization of the simulated hot streak shapes in a real combustor.