The effects of optimized rim seal geometry on the end wall flow of a high-lift low-pressure turbine

To reduce the secondary flow losses of a high-lift low-pressure turbine, a new contour method for the rim seal geometry is proposed in this paper. The numerical simulation and experiment are used to investigate the effects of different rim seal geometries on secondary flow losses at the end wall. The total pressure loss coefficient at the cascade outlet serves as the optimization objective, and the rim seal geometry coupled with the hub of the cascade leading edge is optimized using the radial basis function–genetic algorithm method. The results indicate that compared with the straight rim seal geometry, the optimized rim seal geometry reduces the strength of passage vortex (PV) and corner vortex, and the additional secondary flow losses caused by sealed flow are reduced as well. At three different seal mass flow ratios, the optimized geometry changes the structure of the secondary flow vortices at the end wall. The optimized geometry splits the shear-induced vortex (SIV) into SIV1 and SIV2. The formation and development of SIV1 are suppressed, resulting in the horseshoe vortex pressure-side leg merging with SIV1 to reach the suction surface position further downstream. Meanwhile, SIV2 counteracts the horseshoe vortex suction-side leg in the cascade passage, inhibiting the formation and development of PV. The optimized geometry changes the development of the vortex structure at the leading edge of the cascade by changing the characteristics of the purge flow, thus reducing the strength of PV and improving the aerodynamic performance at the end wall.