Validation of Flat Plate Infrared Assessment for Vane Pressure Side Film Cooling Designs

Abstract

Ongoing work is being conducted to create an improved pressure-side cooling array design for a modern non-proprietary high-pressure turbine vane called the Research Turbine Vane (RTV) using novel optimization techniques. As part of a thorough benchmarking of the baseline vane cooling design, a flat plate model is assessed through the use of conjugate heat transfer (CHT) computational fluid dynamics (CFD) at design-level free stream and film cooling hole blowing conditions. This flat plate model represents the pressure side (PS) film cooling array of the RTV, which has a total of 282 fan-shaped and cylindrical cooling holes and has been tested experimentally using infrared thermography (IRT). The CFD used in this work simulates these IR film cooling experiments. The CHT solver uses high-density unstructured grid which models the fluid in the hot flow, fluid in the cooling plenum, the fluid in each individual cooling hole passage, as well as factoring in the conduction of the plate solid. This is accomplished with a heat flux balance at the solid-fluid interfaces. The code used is called Leo and is a Reynolds-Averaged Navier Stokes (RANS) solver with the Wilcox k-ω turbulence model. Three film-cooled flat plate meshes with total grid cell counts ranging from 4.6 to 25.1 million cells were studied along with an uncooled plate with over 2.5 million cells. To aid in validation of the CHT CFD code, contours of surface temperature, streamwise surface temperature, spanwise surface temperature, and plenum-side plate characteristics are compared to experimental infrared flat plate data of the same scale, conditions and materials. Results also include streamwise net temperature reduction (NTR) comparison between simulations and experimental data. To show the appropriateness of using flat plate models in evaluating modern complex pressure side film-cooling designs, the plate data are also compared to CHT CFD 3-D vane heat flux contours. The CFD tended to under-predict surface temperature with film cooling and over-predict the IRT experiment temperatures without cooling. Disparities between the CFD and experiments are attributed to potential inaccuracies in the simulations, which showed similar differences against two types of experimental temperature instrumentation. Future work will further investigate parameters at multiple spans and streamwise locations including heat flux, net heat flux reduction, and heat transfer coefficient in order to reduce the differences between experiments and the CHT CFD.