Modern aircraft engine designs have to realize high performance while managing important weight and cost issues. For high bypass ratio engines this results in high demands for the low pressure turbine component. The combination of a low speed parameter due to large fan diameters with reduced number of turbine stages due to weight and cost considerations leads to high stage loading requirements. Realizing high turbine efficiencies at low Reynolds Number operation at high altitudes for these high stage loadings is a key for state-of-the-art turbofan engines. For the aerodynamic design, high stage loading factors directly translate into increased airfoil flow turning. These increased turning levels have to be realized in combination with elevated airfoil load in order to keep low airfoil counts. This is particularly challenging in combination and requires minimization of negative effects on the airfoil losses and secondary losses. In this paper the development of a five-stage turbine with high stage loading is discussed with focus on the aerodynamic design. A specially designed cascade test has been part of the turbine design, which showed the need for improvement of the transition modeling within the CFD code used for design and analysis. The derived modeling enhancement is then employed for the analysis of the five-stage rig, which was tested at the altitude test facility at Stuttgart University. The modeling achieved significant improvements in the quality of the numerical results. The analysis includes sensitivities to Reynolds number and a detailed view of the suction side flow.

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