On the effect of geometry of w-wave trenches on film cooling performance of gas turbine blades

In the present study, three types of w-wave trenches with different amplitude configurations are compared with transverse trench (TT), and the use of variable radius fillet (VRF) on downstream lips at different blowing ratio is numerically investigated to measure heat transfer coefficient, and cooling effectiveness. The numerical results are obtained by three-dimensional Reynolds average Navier-Stokes equations (RANS) while employing shear stress transport turbulence models, which are validated by comparing with experimental data. The trench width is kept constant in all cases, yet the three different amplitudes and variable fillet radiuses offered a variety of designs in trench film cooling. The results showed that w-wave trenches impressively improved film cooling effectiveness over the transverse trench, and utilizing fillets at downstream lips of the trench caused significant enhancement on both lateral averaged and centerline cooling performance. Due to the w-wave trench configuration, anti-counter-rotating vortices responsible for pushing coolant film toward the near-wall were formed throughout of downstream wall of the trench, and the cooling flow thus had a more uniform structure. The heat transfer coefficient distributions of filleted w-wave trenches are observed to be more uniform than simple w-wave and transverse trench under all blowing ratio conditions. Moreover, enlargement of the fillet radius in Cases 2 and 3 yielded to the growth of centerline coolant flow, which in turn resulted in the improvement of film cooling effectiveness at all blowing ratios.