Fluid Mechanics and Thermodynamics of Turbomachinery, 5e

368 Fluid Mechanics, Thermodynamics of Turbomachinery
(a)
Direction of
rotation
(b)
coefficient). CC is a combination of both the lift and drag coefficients, as described
below:
C = C sina -C
cosa
C L D
Plain
p
Direction
of rotation
Aileron
blade tip
Wind
Balanced
FIG. 10.26. Aileron control surfaces: (a) showing position of ailerons on two-bladed
rotor; (b) two types of aileron in fully deflected position (adapted from Miller and
Sirocky 1985).
C L
1.5
1
0.5
–0
0.5
–1
0 deg
–60 deg
–90 deg
0 20 40 60 80 100
Angle of attack, deg
(a) Lift coefficient
(10.65)
where a = angle of attack.
The reason for using C C to describe aileron-control braking effectiveness is that only
the chordwise force produces torque (assuming a wind turbine blade with no pitch or
C D
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
p
s
0 deg
–60 deg
–90 deg
20 40 60 80 100
Angle of attack, deg
(b) Drag coefficient
FIG. 10.27. Variation of (a) lift and (b) drag coefficients for the 38% chord ailerons
when set at 0, -60 deg and at -90 deg. (Adapted from Savino et al. 1985. Courtesy
of NASA.)