Upstream Film Cooling on the Contoured Endwall of a Transonic Turbine Vane in an Annular Cascade

The effects of mainstream flow velocity, density ratio (DR), and coolant-to-mainstream mass flow ratio (MFR) on a vane endwall in a transonic, annular cascade were investigated. A blow down facility consisting of five vanes was used. The film cooling effectiveness was measured using binary pressure-sensitive paint (BPSP). The mainstream flow was set using isentropic exit Mach numbers of 0.7 and 0.9. The coolant-to-mainstream density ratio varied from 1.0 to 2.0. The coolant-to- mainstream MFR varied from 0.75% to 1.25%. The endwall was cooled by 18 discrete holes located upstream of the vane passage to provide cooling to the upstream half of the endwall. Due to the curvature of the vane endwall, the upstream holes provided uniform coverage entering the endwall passage. The coverage was effective leading to the throat of the passage, where the downstream holes could provide additional protection. Increasing the coolant flowrate increased the effectiveness provided by the film cooling holes. Increasing the density of the coolant increases the effectiveness on the endwall while enhancing the lateral spread of the coolant. Finally, increasing the velocity of the mainstream while holding the MFR constant also yields increased protection on the endwall. Over the range of flow conditions considered in this study, the binary pressure-sensitive paint proved to be a valuable tool for obtaining detailed pressure and film effectiveness distributions.