Increasing film cooling effectiveness of a gas turbine blade by using an upstream ramp

In the present investigation, a new design is proposed in order to increase the adiabatic film cooling effectiveness over a symmetric gas turbine blade. Apart from using a row of forward diffused shaped holes for coolant injection, the present study suggests a modification at the upstream of the coolant holes by adding a backward step ramp nearby the hole. Numerical solutions of the Reynolds-Averaged Navier-Stokes and energy equations are obtained by using three-dimensional finite element formulation of Galerkin weighted residual method. Numerical simulation is performed for a row of 25° forward-diffused shaped hole injected at 35° to an advanced gas turbine (AGT) symmetric blade. For parametric investigation, three different ramp heights, h = 0.125D, 0.2D and 0.41D, where D is the diameter of the coolant hole at inlet, along with the blowing ratios, M = 0.3, 0.5, 0.9 and 1.3 are considered, while the turbulence intensity is kept constant at 0.5%. For different combinations of blowing ratio and ramp height, enhanced cooling effects are observed in terms of both local and averaged adiabatic film effectiveness (AFE). Notably this enhancement is of higher magnitude for a higher M-h combination. Additionally, diffusion of the coolant increases in lateral direction in the proposed model.