Film cooling in the trailing edge cutback with different land shapes and blowing ratios

The cutback was widely used in advanced gas turbines to protect the trailing edge. The land was a main structure in the cutback region. Therefore, the present study describes a numerical investigation on the film cooling performance in the cutback region with various land shapes (straight-expanding land, arch-expanding land, contracting-expanding land and campaniform land) and blowing ratios (0.2, 0.8 and 1.25). According to the numerical validation, the detached eddy simulations agreed well with the experimental results compared to other turbulence models. The flow structure, film cooling effectiveness and total pressure loss in the cutback region were displayed. Results indicated that the main flow separation vortex, cooling separation vortex, Kelvin-Helmholtz vortex and counter rotating vortices were strongly associated with the land shape and blowing ratio. The Kelvin-Helmholtz vortex was invisible at low blowing ratio and was small at the campaniform land shape. The contracting-expanding land resulted in weak counter rotating vortices within the cutback region. The stronger counter-rotating vortices brought lower film cooling effectiveness. Therefore, the contracting expanding land provided relatively high film cooling effectiveness for most blowing ratios. The different land shape also caused different total pressure losses both in the cooling passage and main flow.