MAXIMIZATION OF COOLING EFFECTIVENESS OF TURBINE BLADE SURFACES USING DIFFERENT ARRANGEMENT OF COOLING HOLES AND VARIOUS BLOWING RATIOS

In gas turbines, the operating temperature of the primary fluid is very high. In order to lessen the damage of turbine blades due to severe working temperature, film cooling holes are commonly implemented during designing of turbine blades. Film cooling effectiveness has been studied numerically to determine the arrangement of cooling holes and optimum blowing ratio. In this study, three dimensional standard Reynold's Average Navier Stokes (RANS) shear stress transport turbulence model have been used for the simulation purpose. Three different shapes of cooling holes have been considered to find out optimum shape of the hole geometry. The blowing ratios equal to 0.2, 0.4, 0.6, 0.8 and 1.0 and the free stream Reynolds number based on the free stream velocity and hydraulic diameter of the mainstream channel as 15316 have been taken for the present study. 3D domain has been used in order to capture recirculation zone near the wall. Effectiveness obtained for fan-shaped hole at M = 0.8 and 1 is maximum compared to conventional hole shapes. Film cooling effectiveness is highest near the hole region which decreases further downstream of cooling holes due to coolant and mainstream intermixing. The simulation results show that best effective blade surface cooling is achieved for fan-shaped staggered row at blowing ratio equal to 1.0.