Evaluation of Superposition Predictions for Showerhead Film Cooling on a Vane

Abstract

The leading edge of a turbine vane is subject to some of the highest temperature loading within an engine, and an accurate understanding of leading edge film coolant behavior is essential for modern engine design. Although there have been many investigations of the adiabatic effectiveness for showerhead film cooling of a vane leading edge region, there have been no previous studies in which individual rows of the showerhead were tested with the explicit intent of validating superposition models. For the current investigation, a series of adiabatic effectiveness experiments were performed with a five-row and threerow showerhead. The experiments were repeated separately with each individual row of holes active. This allowed evaluation of superposition methods on both the suction side of the vane, which was moderately convex, and the pressure side of the vane, which was mildly concave. Superposition was found to accurately predict performance on the suction side of the vane at lower momentum flux ratios, but not at higher momentum flux ratios. On the pressure side of the vane, the superposition predictions were consistently lower than measured values, with significant errors occurring at the higher momentum flux ratios. Reasons for the underprediction by superposition analysis are presented.

State-of-the-Art Cooling Technology for a Turbine Rotor Blade

“…For rotor blades, showerhead film cooling designs are somewhat constrained in the number of rows and holes. For a first-stage vane design, it is common to have as many as seven rows of film cooling holes as studied by Nathan et al [15] and Anderson et al [16]. Such aggressive cooling is not needed for a blade, and in some cases, seven rows of film cooling holes are not practical for a rotor blade configuration.…”