Aircraft turbine blade trailing edges commonly are cooled by blowing air through pressure-side cutback slots. The surface effectiveness is governed by the rate of mixing of the coolant with the mainstream, which is typically much faster than predicted by CFD models. Three-dimensional velocity and coolant concentration fields were measured in and around a cutback slot using a simple uncambered airfoil with a realistic trailing edge cooling geometry at a Reynolds number of 110,000 based on airfoil chord length, which is lower than practical engines but still in the turbulent regime. The results were obtained using magnetic resonance imaging (MRI) techniques in a water flow apparatus. Magnetic resonance concentration (MRC) scans measured the concentration distribution with a spatial resolution of 0.5 mm3 (compared to a slot height of 5 mm) and an uncertainty near 5%. Magnetic resonance velocimetry (MRV) was used to acquire 3D, three-component mean velocity measurements with a resolution of 1.0 mm3. Coupled concentration and velocity measurements were used to identify flow structures contributing to the rapid mixing, including longitudinal vortices and separation bubbles. Velocity measurements at several locations were compared with an unsteady RANS model. Concentration measurements extrapolated to the surface provided film cooling effectiveness and showed that the longitudinal vortices decreased effectiveness near the lands and reduced the average film cooling effectiveness.
Film-Cooled Trailing Edge Measurements: 3D Velocity and Scalar Field
Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 4, 2011; final manuscript received August 10, 2011; published online October 30, 2012. Editor: David Wisler.
This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release, distribution is unlimited.
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Benson, M., Laskowski, G., Elkins, C., and Eaton, J. K. (October 30, 2012). "Film-Cooled Trailing Edge Measurements: 3D Velocity and Scalar Field." ASME. J. Turbomach. January 2013; 135(1): 011030. https://doi.org/10.1115/1.4006425
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