Infrared Assessment of an Optimized Vane Pressure Side Film Cooling Array

Abstract

The following experimental work described here entails the investigation by infrared thermography (IRT) of full-scale flat plates intended to model the pressure side (PS) of a modern fully-cooled turbine inlet vane called the High-Impact Technologies (HIT) Research Turbine Vane (RTV). The imaging system is used to make detailed full-coverage, two-dimensional, steady-state measurements of flat plate surface temperature. The PS has a total of 282 film cooling holes including three rows of showerhead holes near the leading edge and a handful of rows downstream depending on the design. The flat plates precisely match the material, thickness, and cooling hole sizes on the RTV, however they are not intended to match the external pressure field or the characteristics of internal cooling beneath the airfoil surface. Surface temperature relative to individual trial freestream gas temperatures is reported for an uncooled plate, a plate with the baseline RTV cooling scheme, and for four different hole types on a plate with a 3D-optimized cooling array designed for the RTV in previous work using genetic algorithms and computational fluid dynamics (CFD). The four different cooling hole shapes tested on the downstream rows of the optimized array plates include cylindrical holes, fan-shaped holes, Vehr holes, and a new cooling hole called a mini-trench shaped (MTS) hole. Experimentation on flat plate models using infrared thermography provides large amounts of valuable data, is inexpensive and highly repeatable relative to large rotating blowdown rigs. The results provide key insights into the differences between full-PS film cooling performance on the plate versus the 3D RTV and suggests to designers the best cooling hole shape for the next build of the RTV which will soon be tested in a full-scale blowdown rig instrumented with heat flux gauges. Overall, results clearly corroborate how cooling was redistributed and improved over the PS of the RTV in the original computational design effort and suggest that certain hole shapes are best suited for certain locations on the flat plate models.