Wind Energy Handbook. Michael Barton Graham

1.50 6.0 1.13 168 Risø‐A1‐18 18 0.336 0.0025 3.00 −3.6 1.53 6.0 1.15 167 Risø‐A1‐21 21 0.298 0.005 3.00 −3.3 1.45 7.0 1.15 161 Risø‐A1‐24 24 0.302 0.01 2.75 −3.4 1.48 7.0 1.19 157 Risø‐A1‐27 27 0.303 0.01 2.75 −3.2 1.44 7.0 1.15 N/A Risø‐A1‐30 30 0.300 0.01 2.50 −2.7 1.35 7.0 1.05 N/A Risø‐A1‐33 30 0.304 0.01 2.50 −1.6 1.20 7.0 0.93 N/A

Figure 3.71 The Risø‐P series of aerofoil profiles.

The Risø‐P family of just four aerofoils, shown in Figure 3.71 and Table 3.5, was designed to replace the corresponding profiles in the Risø‐A series for use on variable‐pitch and variable‐speed rotors.

The Risø‐B family was designed as six separate aerofoils with an extended range of thickness to chord ratio from 15% to 36%. The aerofoils, generally, have high maximum lift coefficients for use on multi‐megawatt size rotors with low solidity, flexible blades having variable‐speed pitch control. This family of aerofoil profiles is shown in Figure 3.72 and Table 3.6.

Table 3.5 The principal characteristics of the Risø‐P series.

Aerofoil	Max t/c %	x/c at max t/c	y/c at TE	Re × 10^−6	α ο	cl max	Design α	Design cl	Max cl/cd
Risø‐P‐15	15	0.328	0.0025	3.00	−3.5	1.49	6.0	1.12	173
Risø‐P‐18	18	0.328	0.0025	3.00	−3.7	1.50	6.0	1.15	170
Risø‐P‐21	21	0.323	0.005	3.00	−3.5	1.48	6.0	1.14	159
Risø‐P‐24	24	0.320	0.01	2.75	−3.7	1.48	6.0	1.17	156

Figure 3.72 The Risø‐B series of aerofoil profiles.

Table 3.6 The principal characteristics of the Risø‐B series.

Aerofoil	Max t/c %	x/c at max t/c	y/c at TE	Re × 10^−6	α ο	cl max	Design α	Design cl	Max cl/cd
Risø‐B1‐15	15	0.278	0.006	6.00	−4.1	1.92	6.0	1.21	157
Risø‐B1‐18	18	0.279	0.004