Influence of Surface Roughness on the Aerodynamic Losses of a Turbine Vane

The effects of surface roughness on the aerodynamic performance of a turbine vane are investigated for three Mach number distributions, one of which results in transonic flow. Four turbine vanes, each with the same shape and exterior dimensions, are employed with different rough surfaces. The nonuniform, irregular, three-dimensional roughness on the tested vanes is employed to match the roughness which exists on operating turbine vanes subject to extended operating times with significant particulate deposition on the surfaces. Wake profiles are measured for two different positions downstream the vane trailing edge. The contributions of varying surface roughness to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, Integrated Aerodynamics Losses (IAL), area-averaged loss coefficients, and mass-averaged loss coefficients are quantified. Total pressure losses, Mach number deficits, and deficits of kinetic energy all increase at each profile location within the wake as the size of equivalent sandgrain roughness increases, provided the roughness on the surfaces is uniform. Corresponding Integrated Aerodynamic Loss IAL magnitudes increase either as Mach numbers along the airfoil are higher, or as the size of surface roughness increases. Data are also provided which illustrate the larger loss magnitudes which are present with flow turning and cambered airfoils, than with symmetric airfoils. Also described are wake broadening, profile asymmetry, and effects of increased turbulent diffusion, variable surface roughness, and streamwise development.

[1]  David G. Bogard,et al.  Characterization and Laboratory Simulation of Turbine Airfoil Surface Roughness and Associated Heat Transfer , 1996 .

[2]  P. Ligrani,et al.  Transonic Film Cooling Effectiveness from Shaped Holes on a Simulated Turbine Airfoil , 2002 .

[3]  P. Ligrani,et al.  Mach Number/Surface Roughness Effects on Symmetric Transonic Turbine Airfoil Aerodynamic Losses , 2004 .

[4]  Phillip M. Ligrani,et al.  Transonic Aerodynamic Losses Due to Turbine Airfoil, Suction Surface Film Cooling , 1999 .

[5]  J. Nikuradse.  Laws of Flow in Rough Pipes , 1950 .

[6]  Leonhard Fottner,et al.  The Influence of Technical Surface Roughness Caused by Precision Forging on the Flow Around a Highly Loaded Compressor Cascade , 2000 .

[7]  Asher Sigal,et al.  New correlation of roughness density effect on the turbulent boundary layer , 1990 .

[8]  Sigmar Wittig,et al.  Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane , 2005 .

[9]  R. J. Kind,et al.  Measurements and Prediction of the Effects of Surface Roughness on Profile Losses and Deviation in a Turbine Cascade , 1998 .

[10]  K. Bammert,et al.  Influences of Manufacturing Tolerances and Surface Roughness of Blades on the Performance of Turbines , 1976 .

[11]  Sang Woo Lee,et al.  Effects of Surface Roughness and Turbulence Intensity on the Aerodynamic Losses Produced by the Suction Surface of a Simulated Turbine Airfoil , 2004 .

[12]  R. J. Boyle,et al.  Measurements and Predictions of Surface Roughness Effects on the Turbine Vane Aerodynamics , 2003 .

[13]  B. K. Hodge,et al.  A Re-Evaluation of Schlichting’s Surface Roughness Experiment , 1984 .

[14]  Determination of rough-surface skin friction coefficients from wake profile measurements , 2003 .

[15]  P. Ligrani,et al.  Effects of surface roughness and freestream turbulence on the wake turbulence structure of a symmetric airfoil , 2004 .

[16]  N. Abuaf,et al.  Effects of Surface Roughness on Heat Transfer and Aerodynamic Performance of Turbine Airfoils , 1997 .

[17]  S. J. Kline,et al.  Describing Uncertainties in Single-Sample Experiments , 1953 .

[18]  Phillip M. Ligrani,et al.  Analysis and Experiments on Three-Dimensional, Irregular Surface Roughness , 2002 .

[19]  Robert J. Moffat,et al.  Describing the Uncertainties in Experimental Results , 1988 .

[20]  H. Schlichting,et al.  Experimental Investigation of the Problem of Surface Roughness , 1937 .

[21]  K. Bammert,et al.  Measurements of the Boundary Layer Development along a Turbine Blade with Rough Surfaces , 1980 .

[22]  M. L. G. Oldfield,et al.  An Examination of the Contributions to Loss on a Transonic Turbine Blade in Cascade , 1990 .

[23]  M. Govardhan,et al.  Loss Reduction by Means of Two-Dimensional Roughness Elements on the Suction Surface of a Linear Turbine Rotor Cascade , 1999 .

[24]  Robert J. Boyle,et al.  Aerodynamics of a Transitioning Turbine Stator Over a Range of Reynolds Numbers , 1998 .

[25]  M. Plesniak,et al.  The Influence of Large-Scale, High-Intensity Turbulence on Vane Aerodynamic Losses, Wake Growth, and the Exit Turbulence Parameters , 1997 .