Waveforms of Time-Resolved Film-Cooling Parameters on a Leading-Edge Model

Abstract

It is necessary to understand how film cooling both reduces the adiabatic wall temperature and influences the heat transfer coefficient in order to predict its benefit to a gas turbine hot gas path component. Although a great number of studies have considered steady film-cooling flows, unsteadiness has only recently been considered. Unsteadiness in the freestream flow or the coolant flow can cause fluctuations in both the adiabatic effectiveness and heat transfer coefficient, the dynamics of which have been difficult to measure. In previous studies, only time-averaged effects have been measured. The present study has determined time-resolved and waveforms using a novel inverse heat transfer methodology. Unsteady interactions between and were examined near a coolant hole on the leading-edge region of a circular cylinder simulating the leading edge of a turbine blade. The coolant plume is shown to shift back and forth as the jet’s momentum fluctuates, resulting in an increased spread of coolant coverage but less than ideal performance at any instant in time. The phase behavior of the and waveforms was also examined; in some locations, they fluctuate in phase, and in others, they fluctuate out of phase, again impacting the overall film-cooling coverage from the steady-state value. This is the first time that time-resolved waveforms for and have been determined experimentally.