Endwall losses contribute significantly to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. Hence, reducing the extent and intensity of the secondary flow structures helps to enhance overall efficiency. This work focusses on secondary flow reduction in typical aero engine low pressure turbines. From the large range of viable approaches, a promising combination of axis symmetric endwall contouring and 3D airfoil thickening was chosen. Aerodynamic design, experimental verification and further analysis based on numerical simulation are described in a two part paper. In the first part, the aerodynamic design intent and the experimental setup embedded in the closed circuit test facility of the Institute of Aeronautical Propulsion at Stuttgart University are presented. For this work, a three stage turbine of realistic aero engine size was investigated with a conventional and a modified first stage. In order to gain detailed information about the complex flow different advanced measurement techniques were employed. In addition to multiple surface pressure tappings, extensive traverses were taken in several measurement planes with pneumatic probes, 3-component hot-wire probes and non-intrusive laser transit velocimetry. Time-averaged results of these measurements are reported for two different points of operation. By comparing the two configurations of the first stage the influencing of the secondary flow structure is made apparent through a variation in the radial extent and intensity of the endwall secondary flow motion.

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