Session: 12-02: End-wall and Tip Film Cooling

Paper Number: 153362

Experimental Study of Endwall Film Cooling and Heat Transfer for Different Upstream Slot and Hole Geometries in an Annular Sector Cascade Under High-Speed and Low-Speed Conditions – Part 1: Film Cooling Effectiveness 

Today's dry-low emission (DLE) gas turbines pose high requirements on endwall cooling as the flat temperature profile results in increased thermal load. Endwall film cooling can be provided by using discrete holes but also by utilizing purge air exiting the gaps between turbine components. In either case, the downstream propagation of coolant is highly influenced by secondary flow that emerges from the interaction of the endwall boundary layer with the vane surface. To account for the effects of Reynolds- and Mach numbers but also for the influence of the radial pressure gradient, high-speed tests on different slot and hole geometries were performed in an annular sector cascade consisting of four axisymmetrically contoured nozzle guide vanes. The cascade was integrated into the high-speed turbine test rig of the Institute of Fluid Mechanics and Fluid Machinery of the University of Kaiserslautern-Landau, Germany.

The slot geometries were varied in terms of slot width, axial location, and exit angle. The hole geometries were modified with respect to shape (e.g., cylindrical, laidback, fan-shaped), spatial arrangement (e.g., single row, double row), diameter, and exit angle. All geometry variants were tested for a broad range of blowing ratios at both unity and engine-like density ratios. In addition, to investigate the influence of Mach and Reynolds numbers on the interaction of coolant and secondary flow, the study was carried out at three different pressure ratios of 1.48, 1.15, and 1.05.

Part 1 of this study focuses on the local and averaged film cooling effectiveness that was measured using high-resolution pressure-sensitive paint technique.

Presenting Author: Moritz Klappenberger University of Kaiserslautern-Landau

Presenting Author Biography: Studied mechanical engineering at the University of Kaiserslautern-Landau, currently doing his PhD Institute of Fluid Mechanics and Fluid Machinery (SAM), research focus: film cooling in highly loaded nozzle guide vanes.

Authors:

Christian Landfester German Aerospace Center
Moritz Klappenberger University of Kaiserslautern-Landau
Martin Böhle University of Kaiserslautern-Landau
Robert Krewinkel Graz University of Technology