Unsteady Heat Transfer and Pressure Measurements on the Airfoils of a Rotating Transonic Turbine With Multiple Cooling Configurations

Abstract

Measurements are presented for a high-pressure transonic turbine stage operating at design-corrected conditions with forward and aft purge flow and blade film cooling in a short-duration blow-down facility. Four different film-cooling configurations are investigated: simple cylindrical-shaped holes, diffusing fan-shaped holes, an advanced-shaped hole, and uncooled blades. A rainbow turbine approach is used so each of the four blade types comprise a wedge of the overall bladed disk and are investigated simultaneously at identical speed and vane exit conditions. Double-sided Kapton heat-flux gauges are installed at midspan on all three film-cooled blade types, and single-sided Pyrex heat-flux gauges are installed on the uncooled blades. Kulite pressure transducers are installed at midspan on cooled blades with round and fan-shaped cooling holes. Experimental results are presented both as time-averaged values and as time-accurate encoder-averages. In addition, the results of a steady RANS CFD computation are compared to the time-averaged data. The computational and experimental results show that the cooled blades reduce heat transfer into the blade significantly from the uncooled case, but the overall differences in heat transfer among the three cooling configurations is small. This challenges previous conclusions for simplified geometries that show shaped cooling holes outperforming cylindrical holes by a great margin. It suggests that the more complicated flow physics associated with an airfoil operating in an engine-representative environment reduces the effectiveness of the shaped cooling holes. The experimental results appear to show a small benefit to the advanced cooling holes, but this is on the order of the variation caused by changes in the alignment of heat-flux gauges with cooling holes.

An Investigation of Coolant Within Serpentine Passages of a High-Pressure Axial Gas Turbine Blade

“…The experiment that provided the boundary conditions for this model generated an extensive dataset, the vast majority of which is beyond the scope of this paper. A more complete description of the experiment is provided in the accompanying papers by Nickol et al [5]. This paper will focus on calculating the properties of coolant within the serpentine passages using the measurements obtained from the experiments.…”

“…The internal flow model presented in this paper requires an accompanying 3D full-stage CFD prediction to provide cooling hole outlet boundary conditions. A full description of the computational setup, as well as an analysis of its results on the airfoil, is provided in an accompanying paper [5] but a brief description of its setup is provided here for completeness.…”