Effect of bleeding holes on heat transfer characteristics inside u-shaped channel with 60° skewed ribs

The internal coolant channel in an actual turbine blade was simplified into a variable cross-section channel with ribs and bleeding holes. The effect of bleeding holes on the heat transfer characteristics was experimentally studied. The bleeding holes were located in the secondary pass only. Hole opening ratio was defined, and the local analysis method was applied. The effects of the hole opening ratio and the exit mass flow rate on heat transfer and the effect on the pressure distributions at the location of the bleeding holes were experimentally studied. Analysis of the results lead to the following conclusions: with the increase of the hole opening ratio, the heat transfer is enhanced while the exit mass flow rate keeps constant; the local Nusselt Numbers decrease with the increase of the exit mass flow rate while the hole opening ratio keeps unchanged.