Numerical Analysis of Leakage Flow and Film Cooling Characteristics of the Inclined Slashface on Gas Turbine Endwall

Abstract

Targeting the severe mainstream ingestion and non-uniform coolant leakage problems of the endwall slashface, a novel inclined slashface structure is proposed based on a typical perpendicular slashface. The flow characteristics within different slashfaces and turbine cascades as well as the interaction between endwall gap leakages are numerically analyzed. The endwall cooling and blade phantom cooling performance with different slashface designs are compared. The results show that the mainstream ingests at a high axial velocity near the slashface leading edge and ejects out before the normalized axial location z/Cax of 0.6, forming a curved ingestion region. The inclined slashface, especially for α = 60 deg, directly prevents the mainstream ingestion at low blowing ratio, and it nearly eliminates the ingestion at high blowing ratio. The inclined slashface is also able to diminish the ingestion region on the downstream part at high blowing ratio. The slashface leakage influences the phantom cooling effect near the blade trailing edge by modifying the separation vortex. When M = 0.5, the length of endwall coolant coverage between 0.35 < z/Cax < 0.65 shrinks at α = 75 deg, and the cooling effectiveness at z/Cax > 0.8 is increased by 8.1%. When M = 1.0, two inclined designs separately increase the cooling effectiveness of upstream and downstream endwalls by 5.5–16.7% by placing the coolant in the crossflow region of the separation vortex. When M = 1.5, the slashface leakage ameliorates the cooling performance degradation at α = 90 deg. The phantom cooling effectiveness with α = 90 deg is decreased by 11.5% compared with inclined slashface. In summary, the slashface inclination angles of 60 deg and 75 deg have obvious endwall cooling and phantom cooling advantages over 90 deg under high blowing ratios, while they only gain a less advantage on the downstream part endwall under low blowing ratio. This research can provide guidelines for the design of multiple gaps on the turbine endwall.