Turbine vane endwall film cooling from mid-chord or downstream rows and upstream coolant injection

Abstract

Endwall film cooling investigations were carried out in a four-passage linear turbine vane cascade. The endwall film cooling is designed with two cooling-hole configurations: the mid-chord row and the downstream row. Two-row of staggered cylindrical holes in front of the vane leading edge is implemented for providing the upstream coolant injection. In this study, the injection angle of the upstream cooling hole and the endwall cooling hole are fixed at 30°. The mainstream Reynolds number at the cascade inlet is measured at 380,000 based on the vane axial chord length, and the corresponding cascade exit Ma number is 0.5. The turbulence intensity at the mainstream inlet is kept at 19% with an integral length scale of 1.7 cm. The mass flow rate of the coolant for upstream injection and the endwall injection are varying from MFR = 0, 0.5%, 1.0% to 1.5% respectively to optimize the coolant distribution. The coolant-to-mainstream density ratio effects are investigated by feeding three different coolants with DR = 1.0, 1.5 and 2.0. The film cooling effectiveness on the endwall is determined by using the PSP measurement technique. Results will provide useful information about the endwall cooling design with the mid-chord row and downstream row, especially on how to distribute the coolant consumption from the upstream or the endwall locations, which efficiently saves the coolant.