Aerodynamic loss prediction of axial flow turbine blade rows with coolant injection

This work presents a calculation routine for the prediction of the aerodynamic loss of axial flow turbines with coolant injection, which can be easily incorporated into throughflow calculation programs. The concept of the mixing layer is introduced and the one-dimensional method is used to estimate the local mixing pressure loss. For a real annular nozzle guide vane, calculations are performed with the aid of the mixing model and viscous loss correlations in order to predict loss at the blade mid-height. Predictions for various single-row configurations show favourable agreement with experimental results. Losses are also calculated for the multi-row configuration with a consideration of flow recirculation among cooling holes. It is found that the coolant recirculation may cause a considerable increase in the pressure loss when the amount of net coolant supplied is relatively small. The effect of coolant temperature is also examined for both single-row and multi-row cases.