Superposition of Overall Cooling Effectiveness on a Turbine Blade Leading Edge

Abstract

Increasingly harsh turbine environments necessitate the design of more advanced cooling techniques as well as the prediction of those cooling schemes' performance at engine conditions. For several decades, film cooling design has been accelerated through a low-order superposition of adiabatic effectiveness in order to quickly approximate the combined effect of multiple rows of cooling holes, the individual rows of which have already been characterized. While that legacy technique can approximately superpose the benefits of multiple rows of external film cooling holes, it is unable to superpose the added benefits of additional internal cooling features. This limitation of traditional film cooling superposition has been overcome with a new technique that allows superposition of overall effectiveness, which is influenced by both external film cooling and internal cooling. In this article, the new overall effectiveness superposition technique is evaluated in a turbine airfoil leading edge showerhead region. The superposition technique is effective at predicting the added benefit of an additional row of cooling holes in the leading-edge region along with the associated internal cooling that accompanies the additional row of cooling holes. Special care must be taken, however, due to pressure gradients associated with the leading-edge curvature.