Environmental Engineering Reference
In-Depth Information
Figure 12-12. Hub model geometry and loads.
[Spera 1994]
Figure 12-12 shows the geometry of the HAWT hub area and the nomenclature used in the
empirical equations [Spera 1994].
Equation Factors
The derivation of equation factors relies heavily on knowledge of the physical phenom-
ena present, plus intuition and trial-and-error. For this set of fatigue load data, the follow-
ing six factors have been defined that combine basic rotor, tower, and site parameters from
Tables 12-4 and 12-5:
Hub rigidity factor:
a
=
0.5 (1 - cos 2d
3
)
(12-5a)
Tower blockage factor:
b
=
2.5 Upwind truss
(12-5b)
=
1.0
Upwind shell
=
0.2
Downwind shell
Tip chord factor:
c
=
50
c
t
/D
(12-5c)
Air density factor:
d
=
1 - 0.00009 (
Z
+
H
)
(12-5d)
Chordwise dynamic amplification factor:
e =
1 /[1 - (
N
/w
c
)
2
]
(12-5e)
Wind variability factor:
g =
a
D/H
(12-5f )
Search WWH ::
Custom Search