Environmental Engineering Reference
In-Depth Information
6.4 Characteristics of the tandem wind rotors
Figure 37 shows the output coeffi cient
C
P
against the relative tip speed ratio
l
T
[=(relative tip speed)/(wind velocity)], in comparison with
C
P
of Single Wind
Rotor G. The relative tip speed ratio giving the maximum output of Tandem
Wind Rotor GE is faster than that of Single Wind Rotor G, but the output coef-
fi cient of Tandem Wind Rotor GE is unacceptable. The latter is caused by the rear
wind rotor without the twist. Then, the rear baled E was modifi ed to the blade G
(see Fig. 31) designed so as to get the desirable angle of attack (
a
= 11°) irrespective
of the radial position taking account of the fl ow conditions at the rear wind rotor
inlet. The maximum output coeffi cient can be improved successfully but the rela-
tive tip speed ratio
l
T
may be unacceptable as shown in Fig. 38. That is, the blade
profi les must be optimized more as the tandem wind rotors.
(a)
L
=0.08
(b)
L
=0.12
Figure 36 : Flow through the tandem wind rotors.
0.5
Single Wind Rotor G :
b
F
= 0 deg.
Tandem Wind Rotor GE :
b
F
= 10 deg.
0.4
b
R
= 16 deg.
0.3
V
= 10 m/s
D
RF
= 0.84
0.2
L
= 0.08
0.1
0
0
2
4
6
8
10
l
T
Figure 37 : Output of tandem wind rotor GE.
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