Film-Cooling Flowfields With Trenched Holes on an Endwall

The leading edge region along the endwall of a stator vane experiences high heat transfer rates resulting from the formation of horseshoe vortices. Typical gas turbine endwall designs include a leakage slot at the combustor-turbine interface as well as film-cooling holes. Past studies have documented the formation of a horseshoe vortex at the leading edge of a vane, but few studies have documented the flowfield in the presence of an interface slot and film-cooling jets. In this paper, a series of flowfield measurements is evaluated at the leading edge with configurations including a baseline with neither film-cooling holes nor an upstream slot, a row of film-cooling holes and an interface slot, and a row of film-cooling holes in a trench and an interface slot. The results indicated the formation of a second vortex present for the case with film-cooling holes and a slot relative to the baseline study. In addition, turbulence intensity levels as high as 50% were measured at the leading edge with film-cooling holes and a slot compared with the 30% measured for the baseline study. A trench was shown to provide improved overall cooling relative to the no trench configuration as more of the coolant stayed attached to the endwall surface with the trench.

[1]  David G. Bogard,et al.  Scaling of Performance for Varying Density Ratio Coolants on an Airfoil With Strong Curvature and Pressure Gradient Effects , 2001 .

[2]  K. Thole,et al.  Flowfield Measurements in the Endwall Region of a Stator Vane , 2000 .

[3]  Martin Nicklas,et al.  Film-Cooled Turbine Endwall in a Transonic Flow Field: Part II—Heat Transfer and Film-Cooling Effectiveness , 2001 .

[4]  Howard P. Hodson,et al.  Aerodynamic Aspects of Endwall Film-Cooling , 1996 .

[5]  M. F. Blair,et al.  An Experimental Study of Heat Transfer and Film Cooling on Large-Scale Turbine Endwalls , 1974 .

[6]  S. Ekkad,et al.  Film Cooling From a Row of Holes Embedded in Transverse Slots , 2005 .

[7]  Friedrich Kost,et al.  Film-Cooled Turbine Endwall in a Transonic Flow Field: Part I—Aerodynamic Measurements , 2001 .

[8]  Karen A. Thole,et al.  Heat Transfer and Flowfield Measurements in the Leading Edge Region of a Stator Vane Endwall , 1999 .

[9]  Luzeng J. Zhang,et al.  Turbine Nozzle Endwall Film Cooling Study Using Pressure-Sensitive Paint , 2001 .

[10]  Karen A. Thole,et al.  Bump and trench modifications to film-cooling holes at the vane-endwall junction , 2008 .

[11]  W. Colban,et al.  Combustor turbine interface studies: Part 2: Flow and thermal field measurements , 2003 .

[12]  Karen A. Thole,et al.  The Effect of Combustor-Turbine Interface Gap Leakage on the Endwall Heat Transfer for a Nozzle Guide Vane , 2008 .

[13]  Axel Dannhauer,et al.  Experimental Investigation of Turbine Leakage Flows on the Three-Dimensional Flow Field and Endwall Heat Transfer , 2007 .

[14]  Karen A. Thole,et al.  Flowfield Measurements for a Highly Turbulent Flow in a Stator Vane Passage , 1999 .

[15]  D. Bogard,et al.  High-Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations , 2007 .

[16]  R. Bunker,et al.  Film Effectiveness Performance for Coolant Holes Imbedded in Various Shallow Trench and Crater Depressions , 2007 .

[17]  Karen A. Thole,et al.  The Effects of Varying the Combustor-Turbine Gap , 2007 .

[18]  W. Colban,et al.  Combustor Turbine Interface Studies—Part 1: Endwall Effectiveness Measurements , 2003 .

[19]  Friedrich Kost,et al.  Migration of Film-Coolant From Slot and Hole Ejection at a Turbine Vane Endwall , 2006 .

[20]  H. Hodson,et al.  Heat Transfer Committee Best Paper of 1995 Award: Distribution of Film-Cooling Effectiveness on a Turbine Endwall Measured Using the Ammonia and Diazo Technique , 1996 .

[21]  Karen A. Thole,et al.  Adiabatic Effectiveness Measurements of Endwall Film-Cooling for a First Stage Vane , 2004 .

[22]  Terrence W. Simon,et al.  Measurements Over a Film-Cooled, Contoured Endwall With Various Coolant Injection Rates , 2001 .

[23]  R. Bunker,et al.  Turbine Airfoil Net Heat Flux Reduction With Cylindrical Holes Embedded in a Transverse Trench , 2007 .

[24]  Ronald Scott Bunker,et al.  Film Cooling Effectiveness Due to Discrete Holes Within a Transverse Surface Slot , 2002 .

[25]  Terrence W. Simon,et al.  Effects of Slot Bleed Injection Over a Contoured Endwall on Nozzle Guide Vane Cooling Performance: Part I — Flow Field Measurements , 2000 .

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