Experimental Study on the Influence of Film Cooling Hole Extraction on Heat Transfer and Flow Field in Internal Ribbed Cooling Channels of Turbine Blades

Film cooling and internal passage cooling play a fundamental role in turbine blade cooling. As the cooling holes are fed by the internal crossflow, interaction of these both cooling strategies is implicated. The influence of film hole extraction on the internal flow field and heat transfer of a ribbed cooling channel is investigated in this study. Therefore, a rectangular cooling channel (AR = 2:1) is equipped with parallel ribs of four different geometries (90 deg ribs, 60 deg ribs, 60 deg V-shaped ribs, and 60 deg Λ-shaped ribs) and also with bleed holes at varying positions between the ribs. The different geometrical configurations are examined using 2D-particle image velocimetry (PIV) for flow measurements and transient thermochromic liquid crystal (TLC) technique for heat transfer measurements. Depending on the rib-induced heat transfer pattern, cooling hole positions in the rib segments are found, which can enhance passage internal heat transfer. 90 deg and 60 deg ribs show the best results for upstream hole positions regardless of the lateral positioning. V and Λ ribs reveal a benefit for lateral positioned cooling holes near the upstream rib.