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Effects of a Realistically Rough Surface on Vane Aerodynamic Losses Including the Influence of Turbulence Condition and Reynolds Number

[+] Author Affiliations
E. L. Erickson, F. E. Ames

University of North Dakota, Grand Forks, ND

J. P. Bons

Ohio State University, Columbus, OH

Paper No. GT2010-22173, pp. 23-31; 9 pages
  • ASME Turbo Expo 2010: Power for Land, Sea, and Air
  • Volume 4: Heat Transfer, Parts A and B
  • Glasgow, UK, June 14–18, 2010
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-4399-4 | eISBN: 978-0-7918-3872-3
  • Copyright © 2010 by ASME


Aerodynamic loss surveys are reported for a vane with a realistically rough surface. Aerodynamic losses are investigated over a range of turbulence levels {low (0.7%), grid (8.5%), aero-combustor, (13.5%)} and a range of chord Reynolds numbers {Rec = 500,000, 1,000,000, and 2,000,000}. The realistically rough surface distribution was generated by Brigham Young University’s accelerated deposition facility. The surface is intended to represent a TBC surface which has accumulated 7500 hours of operation with a particulate concentration of 0.02 ppmw. The realistically rough surface was scaled by 11 times for consistency with the vane geometry and cast using epoxy to comply with the vane geometry. The surface was applied over the vane pressure surface and about 10% of the suction surface. The 958 by 573 point roughness array generated by Brigham Young on a 9.5 by 5.7 mm region was averaged to a 320 by 191 array for fabrication. The calculated surface roughness parameters of this scaled and averaged array included the maximum roughness, Rt = 1.99 mm, the average roughness, Ra = 0.25 mm and the average forward facing angle, αf = 3.974°. The peak to valley roughness, Rz, was determined to be 0.784 mm. The sand grain roughness of the surface (ks = 0.466 mm) was estimated using a correlation offered by Bons [1]. Based on estimates of skin friction coefficient using a turbulence correlation with the vane chord Reynolds numbers, representative values for the surface’s roughness Reynolds number are 23, 43, and 80 for the three exit condition Reynolds numbers tested. Exit survey measurements for the realistically roughened vane have been compared with the base vane geometry. Total pressure loss measurements have shown an incremental increase above the original base vane which averages 0.68% for the low turbulence, 0.48% for the grid turbulence and 0.24% for the aero-combustor turbulence conditions. A portion of this increment, about 0.20%, could be attributed to the thicker trailing edge due to the average thickness of the roughened tile applied. The roughness on the near suction surface along with the abrupt end of the roughness tiles at about 0.05 m from the stagnation region causes early transition on the suction surface. This early transition influences the comparison of the low turbulence cases much more due to laminar flow on the base vane suction surface. The grid turbulence shows an incremental loss of 0.48% and this difference is likely due to both the thicker trailing edge and the suction surface roughness. The incremental loss increase for the aero-combustor is lower suggesting that the thicker trailing edge has the largest affect on incremental losses.

Copyright © 2010 by ASME



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