Introduction to Modern Wind Turbines - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 77

2.4

1.0

2.0

( ACL 1 , CL 1max)

S 1

RCL 1

1.6

1.0

RCL 2

- 0.0320

1.2

0.8

(41.0 , CL 2max)

0.4

(92.0, 0.0)

( A 0, 0.0)

0.0

-0.4

Sample test data: NACA 4418 airfoil
Pre-stall model
Post-stall model
Model position points

-0.8

-100 10 20 30 40 50 60 70 80 90 100 110

Angle of attack, α, deg

(a) Lift coefficient models.

Figure 2-16. Pre- and post-stall models of the variation of airfoil lift and drag coefi-
cients with angle of attack. Input data are underlined. [Spera 2008]

regime where it is assumed that airfoil contour has only a secondary effect on aerodynamic
forces. All the governing equations are available in the reference.
The peak power of wind turbine rotors equipped with modern airfoils designed specii-
cally for ixed-pitch wind turbines [Tangler and Somers 1985, 1986; Tangler 1987] is limited
by aerodynamic stall in higher winds. Therefore power calculations for these rotors require
the joint application of both the pre- and post-stall equations.