Environmental Engineering Reference
In-Depth Information
Table 14.2 Effect of number of blades on power generation and aerodynamic efficiency
Rotor 2-blades 3-blades 4-blades 6-blades
X
r
(rpm) 86.32 412.35 494.22 502.44
P
g
(mW) 9.89 158.08 216.24 214.97
g
g
(per unit) 0.0545 0.4011 0.4595 0.4614
P
a
(mW) 181 394 470 466
k 0.28 1.32 1.59 1.61
C
p
0.073 0.159 0.190 0.188
where X
r
the rotor speed, P
g
is the power supplied by the electrical generator, g
g
the electrical
generator efficiency, P
a
the power at the shaft given by the aerodynamics and C
p
the aerodynamic
power coefficient
Statistical Plot of Power Based on
Blade Number
Statistical Plot of Rotor Speed Based on
Blade Number
550
250
500
225
450
200
400
175
350
150
300
125
250
100
200
75
150
50
100
25
0
50
2
3
4
5
6
2
3
4
5
6
Number of Blades
Number of Blades
Fig. 14.19 Effect of the number of blades on the rotor speed X
r
and on the generator power P
g
(a)
(b)
0.7
0.25
6 blades
4 blades
6 blades
4 blades
0.6
0.2
0.5
3 blades
0.15
0.4
2 blades
0.3
0.1
3 blades
0.2
0.05
0.1
2 blades
0
0
0
200
400
600
800
1000
1200
0
0.5
1
1.5
2
rotor speed (rpm)
tip speed ratio: lambda
Fig. 14.20 a Efficiency g
g
of the electrical generator: all the experimental cases presented in
Sects.
14.4.1
,
14.6.1
,
14.6.2
and
14.6.3
. The maximum generator efficiency is 0.6131 at 945 rpm.
b Aerodynamic power coefficient versus tip speed ratio as a function of number of blades for
N = 2, 3, 4, 6
