Rotating Effects on Heat Transfer Rate in a Cooling Air Passage of a Gas Turbine Blade

In this paper numerical results on the effects of rotation on heat transfer rates in a cooling air passage that belongs to a gas turbine blade are presented. A 180° turn about has been considered into the computations. Rotation rates of 1145, 2800 and 3600 rpm were considered into the analysis. Comparisons for a Re = 53 000 with literature published results showed a good agreement. The simulation has been based on the finite volume approach of a 3-D flow using a second moment closure model for modeling the turbulence in the air passage. The results indicate that the rotation rate produces important changes in the heat transfer rate. In this work heat transfer has been characterized through the Nusselt number, along the air flowing path. A rotation rate of 3600 rpm produces an increment of the heat transfer rate by 14% along the inlet edge of the blade compared with the condition of no rotation. However, a decrease of 16.7% is observed in the outlet edge under the same conditions, compared against the non rotating condition. The situation is drastic in the tip region of the blade where more than 18.5% higher heating rate is observed for the same rotating speed. These results correspond to the outer internal wall of the blade passage, while the situation for the inner wall are in general less severe. The velocity field shows the formation of several secondary cells of flow which may represent stagnation regions for both pressure and heat transfer. These secondary cells are observed mainly in the region of the turn of 180°. The dynamics of these cells are important for the performance and design of the cooling system in gas turbines.