Entrance effect of curved endwall on heat transfer and flow structure in a confluent channel with pin fins

In advanced turbine blade internal cooling channels, the majority of the remaining coolant converges into the trailing edge and constitutes a confluent flow before the slot entrance. The entrance effects of curved endwalls (convex, concave) for confluent internal cooling channel are numerically investigated in this paper. The overall heat transfer performances and flow structures are compared in the slot channel with pin fin cooling at the five momentum ratios (M = 0.1–2.1). Among all the cases studied, the higher momentum inflow not only enhance heat transfer but also reduce pressure loss in the slot channel with concave endwalls. In particular, the substantial comprehensive heat transfer factor (η) increase reaches 29.4% higher than the flat endwalls at the given relative curvature height ratio of 1.83. For the models with convex endwalls, the jet-like flow improves the η at the most by 12.1% compared to the flat endwalls. As the curvature height ratio increases, the effects of curved endwalls diminish eventually. In addition, the momentum ratio determines the formation and specified impact of the above flow characteristics in the confluent flow. The curved endwalls exhibit more increase in the η at lower M.