Effect of blade tip structure on tip flow characteristics in turbine rotor

Numerical simulations of three blade tip configurations were conducted using the commercial CFD software Ansys CFX. The k-ω SST (shear stress transport) turbulence model was applied to compute the models under varying tip structures, blowing ratios, and blade tips. The findings demonstrated a direct correlation between the blade tip and the leakage flow entering the recessed area of the blade tip. Smaller blade tip gaps led to heightened flow resistance for the leakage flow, resulting in a corresponding reduction in leakage flow volume. When the cooling air blowing ratio increased, the cooling air directly impacted the interior casing wall, creating a backflow pattern around the point of impact. This backflow vortex was induced by the vortices within the crevice of the blade tip. In the case of configuration 3, the mid-section partition served as an obstruction to the entering leakage flow, thereby augmenting the cooling efficiency on the suction side of the blade tip. However, the partition also triggered the development of uneven crevice vortices and corner vortices on its opposing sides, leading to an elevation in thermal stress gradient. Entropy increment analysis underscored the pivotal role of the blade tip gap in determining the primary leakage loss in the blade tip region. Decreasing the blade tip gap markedly reduced losses in the blade trailing edge region.