Using Gurney Flaps to Control Laminar Separation on Linear Cascade Blades

This paper describes an experimental investigation of the use of Gurney flaps to control laminar separation on turbine blades in a linear cascade. Measurements were made at Reynolds numbers (based upon inlet velocity and axial chord) of 28×10 3 , 65×10 3 and 167×10 3 . The freestream turbulence intensity for all three cases was 0.8%. Laminar separation was present on the suction surface of the Langston blade shape for the two lower Reynolds numbers. In an effort to control the laminar separation, Gurney flaps were added to the pressure surface close to the trailing edge. The measurements indicate that the flaps turn and accelerate the flow in the blade passage toward the suction surface of the neighboring blade thereby eliminating the separation bubble. Five different sizes of Gurney flaps, ranging from 0.6 to 2.7% of axial chord, were tested. The laser thermal tuft technique was used to determine the influence of the Gurney flaps on the location and size of the separation bubble. Additionally, measurements of wall static pressure, profile loss, and blade-exit flow angle were made. The blade pressure distribution indicates that the lift generated by the blade is increased. As was expected, the Gurney flap also produced a larger wake. In practice, Gurney flaps might possibly be implemented in a semi-passive manner. They could be deployed for low Reynolds number operation and then retracted at high Reynolds numbers when separation is not present. This work is important because it describes a successful means for eliminating the separation bubble while characterizing both the potential performance improvement and the penalties associated with this semi-passive flow control technique.

[1]  Roy Y. Myose,et al.  Gurney Flap Experiments on Airfoils, Wings, and Reflection Plane Model , 1998 .

[2]  Hugh W. Coleman,et al.  Experimentation and Uncertainty Analysis for Engineers , 1989 .

[3]  R. P. Dring,et al.  The Effects of Turbulence and Stator/Rotor Interactions on Turbine Heat Transfer: Part II—Effects of Reynolds Number and Incidence , 1988 .

[4]  Kambiz Vafai,et al.  EFFECT OF VARIABLE AXIAL CHORD ON A LOW-PRESSURE TURBINE BLADE , 1999 .

[5]  Richard B. Rivir,et al.  Transition on Turbine Blades and Cascades at Low Reynolds Numbers. , 1996 .

[6]  C. P. van Dam,et al.  ACTIVE LOAD CONTROL FOR WIND TURBINE BLADES USING MEM TRANSLATIONAL TABS , 2001 .

[7]  Paul I. King,et al.  Low Reynolds number loss reduction on turbine blades with dimples and V-grooves , 2000 .

[8]  T. Simon,et al.  Measurements in a Turbine Cascade Flow Under Ultra Low Reynolds Number Conditions , 2002 .

[9]  David W. Hurst,et al.  Aerodynamics of Gurney Flaps on a Single-Element High-Lift Wing , 2000 .

[10]  James W. Baughn,et al.  The effect of turbulence intensity and length scale on low-pressure turbine blade aerodynamics , 2001 .

[11]  M. Selig,et al.  High-Lift Low Reynolds Number Airfoil Design , 1997 .

[12]  J. H. Horlock.  Axial Flow Turbines , 1966 .

[13]  James W. Baughn,et al.  An Experimental Investigation of Heat Transfer, Transition and Separation on Turbine Blades at Low Reynolds Number and High Turbulence Intensity. , 1995 .

[14]  R. P. Dring,et al.  The Effects of Turbulence and Stator/Rotor Interactions on Turbine Heat Transfer: Part I—Design Operating Conditions , 1988 .

[15]  Bruce L. Storms,et al.  Lift enhancement of an airfoil using a Gurney flap and vortex generators , 1993 .

[16]  J. Janus,et al.  Analysis of industrial fan designs with Gurney flaps , 2000 .

[17]  Ioannis Antoniou,et al.  Design and verification of the Risø-B1 airfoil family for wind turbines , 2001 .

[18]  Richard B. Rivir,et al.  Effect of Passive and Active Air-Jet Turbulence on Turbine Blade Heat Transfer , 1997 .