Effect of side-wall ribs on heat transfer and flow characteristics in internal cooling passage of gas turbine blade

The effect of the side-wall ribs on the heat transfer and flow characteristics in the blade internal cooling passage was conducted by both experiments and CFD calculations, and its optimal shape, arrangement and further development were investigated. It is necessary for the side-wall ribs to optimize the shape for the purpose of not increasing the total pressure loss as much as possible. In this study, Λ and V shaped side-wall ribs with aspect ratio of 1.0 were numerically and experimentally investigated. In addition, with the aim of reducing the total pressure loss, the side-wall ribs with slit which were modified by removing the central part of the Λ and V shaped ribs and those combinations were investigated. As a result, it was confirmed that the combination of V and V shaped with slit were promising and multi-objective optimization using a genetic algorithm was conducted for it. The design parameters were the angle of attack (AoA) for both V shaped with slit and V shaped side-wall ribs, the slit width of V shaped and the height of ribs. The objective functions were Nusselt number, total pressure loss coefficient and thermal performance. The optimized shape has the highest thermal performance, although there exists a strong trade-off relationship between heat transfer coefficient and total pressure loss coefficient. Moreover, the effect of aspect ratio was investigated with considering the vortices distributions in the three-dimensional space. In this study, two kinds of aspect ratio, W/H=0.5 and 2.0 were numerically investigated. As a result, it was found that W/H=0.5 is the best with respect to thermal performance due to pressure loss reduction because the interaction of vortices were suppressed. In conclusion, the side-wall ribs promote the reattachment of separated cooling air flow and the high heat transfer coefficient region can be expanded and the thermal performance can be improved.