Environmental Engineering Reference
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safety. The most obvious possibility here is that the deflection of the blades under
load will cause them to hit the tower.
9.4 Simple Load Model Analysis of 500 W Turbine
This section describes the determination of the forces and moments on the com-
ponents of the turbine shown in Fig. 6.1 and converts them into equivalent
stresses. The basic operating parameters are:
P design ¼ 500 W
X design ¼ 700 rpm ¼ 73 : 30 rad = s @ U design ¼ 10 : 5m = s
ð 9 : 34 Þ
X max ¼ 1000 rpm ¼ 104 : 72 rad = s :
The design power, P design , design wind speed, U design , and angular velocity,
X design , are obviously set by the blade design for power extraction. The second
implies U ave = 7.5 m/s, and from Table 9.2 of IEC 61400-2, U ref = 37.5 m/s and
U e50 = 1.4U ref by (IEC 10) = 52.5 m/s. The third is an estimate of the maximum
blade speed from all the load cases.
k design can be calculated using Eq. 9.29 noting that the blade radius is actually
0.97 m:
k design ¼ 0 : 97
10 : 5
p 700
30
¼ 6 : 77
ð 9 : 35 Þ
From Eq. 9.2 , noting that power must be in kW, the efficiency g is
g ¼ 0 : 6 þ 0 : 005 0 : 5 ¼ 0 : 603
ð 9 : 36 Þ
Now ( 9.1 ) can be used to find Q design
Q design ¼ 30 0 : 5 1000 = 0 : 603 p 700
ð
Þ ¼ 11 : 32 Nm
ð 9 : 37 Þ
From ( 9.3 ) x yaw,max is given by:
x max ¼ 3 0 : 01 ð p 0 : 97 2 2 Þ¼ 2 : 99 rad = s
ð 9 : 38 Þ
9.4.1 Loads for Case A: Normal Operation
The centrifugal load is given by Eq. 9.4 which involves two parameters that have
not yet been determined. m B , the blade mass, is easily found by weighing, or for
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