scholarly journals New Airfoils for Small Horizontal Axis Wind Turbines

1998 ◽  
Vol 120 (2) ◽  
pp. 108-114 ◽  
Author(s):  
P. Gigue`re ◽  
M. S. Selig
Keyword(s):  
Wind Turbines ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Horizontal Axis ◽  
Variable Speed ◽  
Edge Roughness ◽  
Horizontal Axis Wind Turbines ◽  
Wind Energy Systems ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In a continuing effort to enhance the performance of small wind energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1–5 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Vol 125 (4) ◽  
pp. 468-478 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Vortex Generators ◽  
Wind Turbine Blades ◽  
High Lift ◽  
Edge Roughness ◽  
Proper Design ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades, airfoils of more than 25% thickness can be found at mid-span and inboard locations. At mid-span, aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root, structural requirements become more important. In this paper, the performance for the airfoil series DU FFA, S8xx, AH, Risø and NACA are reviewed. For the 25% and 30% thick airfoils, the best performing airfoils can be recognized by a restricted upper-surface thickness and an S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Risø-A1-24 (24%) airfoils are small. For a 30% thickness, the DU 97-W-300 meets the requirements best. Reduction of roughness sensitivity can be achieved both by proper design and by application of vortex generators on the upper surface of the airfoil. Maximum lift and lift-to-drag ratio are, in general, enhanced for the rough configuration when vortex generators are used. At inboard locations, 2-D wind tunnel tests do not represent the performance characteristics well because the influence of rotation is not included. The RFOIL code is believed to be capable of approximating the rotational effect. Results from this code indicate that rotational effects dramatically reduce roughness sensitivity effects at inboard locations. In particular, the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, DU 00-W-350 and DU 00-W-401, respectively, is remarkable. As a result of the strong reduction of roughness sensitivity, the design for inboard airfoils can primarily focus on high lift and structural demands.

Modification of the NACA 632-415 Leading Edge for Better Aerodynamic Performance

2002 ◽  
Vol 124 (4) ◽  
pp. 327-334 ◽  
Author(s):  
Christian Bak ◽  
Peter Fuglsang
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Power Level ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Dynamic Stall ◽  
Wind Tunnel Tests ◽  
Damping Characteristics ◽  
Edge Roughness ◽  
Drag Ratio

Double stall causes more than one power level when stall-regulated wind turbines operate in stall. This involves significant uncertainty on power production and loads. To avoid double stall, a new leading edge was designed for the NACA 632-415 airfoil, an airfoil that is often used in the tip region of wind turbines. A numerical optimization tool incorporating XFOIL was used with a special formulation for the airfoil leading edge shape. The EllipSys2D CFD code was used to analyze the modified airfoil. In theory and in wind tunnel tests, the modified airfoil showed smooth and stable stall characteristics with no tendency to double stall. Also, both theory and wind tunnel tests showed that the overall aerodynamic characteristics were similar to NACA 632-415 except for an increase in the lift-drag ratio below maximum lift and an increase in maximum lift. The wind tunnel tests showed that dynamic stall and aerodynamic damping characteristics for the modified airfoil and the NACA 632-415 airfoil were the same. The modified airfoil with leading edge roughness in general had better characteristics compared with the NACA 632-415 airfoil.

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Wind Turbine Blades ◽  
Strong Reduction ◽  
High Lift ◽  
Edge Roughness ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades airfoils of more than 25% thickness can be found at mid-span and inboard locations. In particular at mid-span aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root srtuctural requirements become more important. In this paper the performance for the airfoil series DU, FFA, S8xx, AH, Riso̸ and NACA are reviewed. For the 25% and 30% thick airfoils the best performing airfoils can be recognized by a restricted upper surface thickness and a S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Riso̸-A1-24 (24%) airfoil are small. For a 30% thickness the DU 97-W-300 meets the requirements best. At inboard locations the influence of rotation can be significant and 2d wind tunnel tests do not represent the characteristics well. The RFOIL code is believed to be capable of approximating the rotational effect. In particular the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, respectively DU 00-W-350 and DU 00-W–401, is remarkable. Due to the strong reduction of roughness sensitivity the design for inboard airfoils could primarily focus on high lift and structural demands.

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