Effect of axial turbine non-axisymmetric endwall contouring on film cooling at different locations

摘要

Non-axisymmetric endwall contouring in axial turbines are becoming popular to improve the passage aerodynamic performance or the endwall heat transfer characteristics. Meanwhile, endwall contouring changes the film cooling performance on the endwall surface by modifying the secondary flow fields and the endwall surface shapes, thus impacting the turbine efficiency and durability. Better understandings of the non-axisymmetric contoured endwall film cooling performances are in great need. In this study, adiabatic film cooling effectiveness (η) of discrete film cooling hole injections at different axial locations on an non-axisymmetric contoured endwall and a baseline endwall with different density ratios and matched averaged blowing ratios to the engine conditions are studied experimentally using Pressure Sensitivity Paint (PSP) technique. Computational fluid dynamics (CFD) simulations are also carried out to look into the local flow fields. The results show that the differences in endwall η distributions between the contoured endwall and the baseline endwall are dominated by the streamwise pressure gradients, i.e. at locations with smaller streamwise pressure gradient values on the contoured endwall than those on the flat endwall, the local η values on the contoured endwall are smaller than those on the flat end-wall, and vice versa.