Environmental Engineering Reference
In-Depth Information
The shaft bending moment is found from Eq. 9.16 :
M shaft ¼ 3 : 98 9 : 81 0 : 026 þ 3 : 98 0 : 0049 104 : 72 2 0 : 026
¼ 6 : 52 Nm
ð 9 : 50 Þ
9.4.6 Loads for Case F: Short at Electrical Connection
Now consider the load due to a short circuit at the generator. The turbine has a
permanent generator, so G = 2 (the short circuit torque factor). Thus,
M x shaft ¼ 2 11 : 32 ¼ 22 : 64 Nm
ð 9 : 51 Þ
from ( 9.17 ) and
M xB ¼ 22 : 64 = 3 ¼ 7 : 55 Nm
ð 9 : 52 Þ
from ( 9.18 ).
Load case G does not apply to this turbine, as it does not use any form of
braking.
9.4.7 Loads for Case H: Parked Wind Loading
This wind loading is applied to the parked turbine at a wind speed of U e50 . It will
be assumed that the turbine has furled and the blades are effectively stationary.
Because of the furling the blades will not be normal to the wind direction, so if we
use ( 9.23 ) with a projected blade area of 0.231 m 2 , then the resulting bending
moment will be over-estimated:
M yB ¼ 1
4 1 : 5 1 : 225 52 : 5 2 0 : 231 0 : 97 ¼ 283 : 71 Nm
ð 9 : 53 Þ
Similarly, from ( 9.25 )
F x shaft ¼ 0 : 5 3 1 : 5 1 : 225 52 : 5 2 0 : 231 ¼ 1754 : 89 N
ð 9 : 54 Þ
where C d is taken as 1.5 from Table 9.5 .
9.5 Equivalent Component Stresses and Ultimate Material
Strengths
The loads that have been calculated in Sect. 9.4 must be converted to equivalent
stresses. This requires additional information, principally of component areas with
the generic symbol A, and values for the section modulus, W, the second moment
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