Analysis of Flow Structures in a High Pressure Turbine Stator Based on Optimized Endwalls

To further enhance the ability of the non-axisymmetric endwalls profiling technique to improve the flow field structure in the high pressure turbine stator passage, numerical optimization methods based on Bezier curves were applied to design non-axisymmetric endwalls for the hub and shroud of a high pressure turbine stator. In order to investigate the flow mechanism of the improvement in flow field by non-axisymmetric endwalls, the flow structures in the passage of stator were compared pre and post optimization by using 3-D streamlines in the vicinity of endwalls. By compared with the results of aerodynamic performance, after using non-axisymmetric endwalls, the total pressure loss coefficient at the stator exit is markedly reduced by 9.93%, while the mass flow increased no more than 0.13%, at the same time, the distribution of exit flow yaw angle becomes more uniform. The analyses of flow field show that the passage vortex in the stator mainly consists of the low-energy fluid from the endwall boundary layer, and the strength of passage vortex is primarily determined by both the migration of endwall boundary layer and the strength of pressure side of horseshoe vortex. And by modifying local static pressure distribution, the non-axisymmetric endwalls accomplish to control the boundary layer movement and achieve the goals of improvement in flow structures and reduction of flow loss.