Table Of ContentSchool of Innovation, Design and Engineering
Bachelor Thesis in
Aeronautical Engineering
15 credits, Basic level 300
Investigation of Different Airfoils on Outer
Sections of Large Rotor Blades
Authors: Torstein Hiorth Soland and Sebastian Thuné
Report code: MDH.IDT.FLYG.0254.2012.GN300.15HP.Ae
Sammanfattning
Vindkraft
står
för
ca
3
%
av
jordens
produktion
av
elektricitet.
I
jakten
på
grönare
kraft,
så
ligger
mycket
av
uppmärksamheten
på
att
få
mer
elektricitet
från
vindens
kinetiska
energi
med
hjälp
av
vindturbiner.
Vindturbiner
har
använts
för
elektricitetsproduktion
sedan
1887
och
sedan
dess
så
har
turbinerna
blivit
signifikant
större
och
med
högre
verkningsgrad.
Driftsförhållandena
förändras
avsevärt
över
en
rotors
längd.
Inre
delen
är
oftast
utsatt
för
mer
komplexa
driftsförhållanden
än
den
yttre
delen.
Den
yttre
delen
har
emellertid
mycket
större
inverkan
på
kraft
och
lastalstring.
Här
är
efterfrågan
på
god
aerodynamisk
prestanda
mycket
stor.
Vingprofiler
för
mitten/yttersektionen
har
undersökts
för
att
passa
till
en
7.0
MW
rotor
med
diametern
165
meter.
Kriterier
för
bladprestanda
ställdes
upp
och
sensitivitetsanalys
gjordes.
Med
hjälp
av
programmen
XFLR5
(XFoil)
och
Qblade
så
sattes
ett
blad
ihop
av
varierande
vingprofiler
som
sedan
testades
med
bladelement
momentum
teorin.
Huvuduppgiften
var
att
göra
en
simulering
av
rotorn
med
en
aero-‐elastisk
kod
som
gav
information
beträffande
driftsbelastningar
på
rotorbladet
för
olika
vingprofiler.
Dessa
resultat
validerades
i
ett
professionellt
program
för
aeroelasticitet
(Flex5)
som
simulerar
steady
state,
turbulent
och
wind
shear.
De
bästa
vingprofilerna
från
denna
rapportens
profilkatalog
är
NACA
63-‐6XX
och
NACA
64-‐6XX.
Genom
att
implementera
dessa
vingprofiler
på
blad
design
2
och
3
så
erhölls
en
mycket
hög
prestanda
jämfört
med
stora
kommersiella
HAWT
rotorer.
Abstract
Wind
power
counts
for
roughly
3
%
of
the
global
electricity
production.
In
the
chase
to
produce
greener
power,
much
attention
lies
on
getting
more
electricity
from
the
wind,
extraction
of
kinetic
energy,
with
help
of
wind
turbines.
Wind
turbines
have
been
used
for
electricity
production
since
1887
and
have
since
then
developed
into
more
efficient
designs
and
become
significantly
bigger
and
with
a
higher
efficiency.
The
operational
conditions
change
considerably
over
the
rotor
length.
Inner
sections
are
typically
exposed
to
more
complex
operational
conditions
than
the
outer
sections.
However,
the
outer
blade
sections
have
a
much
larger
impact
on
the
power
and
load
generation.
Especially
here
the
demand
for
good
aerodynamic
performance
is
large.
Airfoils
have
to
be
identified
and
investigated
on
mid/outer
sections
of
a
7.0
MW
rotor
with
165
m
diameter.
Blade
performance
criteria
were
determined
and
investigations
like
sensitivity
analysis
were
made.
With
the
use
of
XFLR5
(XFoil)
and
Qblade,
the
airfoils
were
made
into
a
blade
and
tested
with
the
blade
element
momentum
theory.
This
simulation
gave
detailed
information
regarding
performance
and
operational
loads
depending
on
the
different
airfoils
used.
These
results
were
then
validated
in
a
professional
aero-‐elastic
code
(Flex5),
simulating
steady
state,
turbulent
and
wind
shear
conditions.
The
best
airfoils
to
use
from
this
reports
airfoil
catalogue
are
the
NACA
63-‐6XX
and
NACA
64-‐6XX.
With
the
implementation
of
these
airfoils,
blade
design
2
and
3
have
a
very
high
performance
coefficient
compared
to
large
commercial
HAWT
rotors.
Carried
out
at:
Statoil
ASA,
R&D
NEH
OWI
Advisor
at
MDH:
Sten
Wiedling
(KTH)
Advisor
at
Statoil
ASA:
Andreas
Knauer,
Dr.-‐Ing.
Examiner:
Mirko
Senkovski
Nomenclature
B
–
Number
of
Blades
BEM
–
Blade
Element
Momentum
theory
c
–
Chord
length
(m)
C
–
Section
Drag
Coefficient
d
C
–
Total
Drag
Coefficient
D
C
–
Section
Lift
Coefficient
l
C –
Total
Lift
Coefficient
L
Cl/Cd
–
L/D
–
Lift
to
drag
ratio
C –
Pitching
Moment
Coefficient
m
C –
Pressure
Coefficient
/
Performance
Coefficient
P
H ,
H
–
Shape
factor
12 32
HAWT
–
Horizontal-‐Axis
Wind
Turbine
M
–
Mach
number
NACA
–
National
Advisory
Committee
for
Aeronautics
P
–
Power
output
(W)
p
–
Pressure
(Pa)
R
–
Global
radius
(m)
r
–
Local
radius
(m)
RPM
–
Revolutions
Per
Minute
S.U.,
S.L.
–
Separation
Upper
and
Separation
Lower
T.U.,
T.L
–
Transition
Upper
and
Transition
Lower
t/c
–
Thickness
to
chord
ratio
(%)
V
–
Free
stream
wind
speed
(m/s)
W
–
Relative
blade
velocity
(m/s)
x/c
–
Location
along
the
chord
(m)
α
–
AoA
–
Angle
of
Attack
(degrees
°)
β
–
Inflow
angle
(degrees
°)
Γ
–
Circulation
γ
–
Twist
angle
(degrees
°)
δ ,
δ ,
δ
–
Displacement,
Momentum
and
Energy
thickness
1 2 3
η
–
Efficiency
λ
-‐
TSR
–
Tip
Speed
Ratio
μ
–
Dynamic
viscosity
(𝑃𝑎⋅𝑠)
ρ
–
density
(kg/m3)
Ω
–
Angular
velocity
(rad/s)
SAMMANFATTNING
2
ABSTRACT
3
NOMENCLATURE
5
1.
INTRODUCTION
9
2.
HISTORICAL
PERSPECTIVE
10
3.
AIRFOILS
15
3.1
National
Advisory
Committee
for
Aeronautics
(NACA)
15
3.2
National
Renewable
Energy
Laboratory
(NREL)
17
4.
METHODS
18
4.1
Historical
Turbines
18
4.2
General
Blade
Design
Criteria
18
4.2.1
Blade
Performance
Criteria
19
4.2.2
Inner
Root
Section
Criteria
20
4.2.3
Middle
Section
Criteria
21
4.2.4
Outer
Section
Criteria
21
4.2.5
Blade
Section
Calculation
21
4.2.6
Specific
Blade
Design
22
4.2.7
Blade
Design
Procedure
23
4.3
Airfoil
Catalogue
and
Roughness
Insensitivity
Analysis
24
4.3.1
Airfoil
Design
for
Wind
Turbines
With
Roughness
Insensitivity
25
4.3.2
Boundary
Layer
Theory
28
4.4
Blade
Element
Momentum
(BEM)
Theory
32
4.4.1
Momentum
Theory
32
4.4.2
Blade
Element
Theory
33
4.5
Qblade
38
4.5.1
General
Validation
of
Simulation
Results
38
4.6
Javafoil
39
4.6.1
Roughness
analyses
39
4.6.2
Limitations
40
4.7
Flex5
41
5.
RESULTS
42
5.1
Historical
Turbines
42
5.1.1
Gedser
Wind
Turbine
42
5.1.2
MOD-‐2
Turbine
44
5.2
Blade
Design
Criteria
47
5.3
Roughness
Insensitivity
Analysis
48
5.4
Qblade
Blade
Design
and
Turbine
Simulation
50
5.4.1
Blade
Design
1
50
5.4.2
Blade
Design
2
56
5.4.3
Blade
Design
3
61
5.5
Flex5
66
5.5.1
Blade
Design
2
67
5.5.2
Blade
Design
3
71
6.
DISCUSSION
74
6.1
Historical
Turbines
74
6.1.1
Gedser
Wind
Turbine
74
6.1.2
MOD-‐2
Turbine
74
6.2
Roughness
Insensitivity
Analysis
76
6.3
Qblade
76
6.3.1
Blade
Design
1
76
6.3.2
Blade
Design
2
77
6.3.3
Blade
Design
3
78
6.4
Flex5
79
6.4.1
Blade
Design
2
80
6.4.2
Blade
Design
3
81
6.5
Comparison
of
Qblade
and
Flex5
82
7.
CONCLUSION
83
8.
FURTHER
WORK
84
APPENDIX
A
85
Airfoil
Catalogue
85
APPENDIX
B
104
Use
of
Qblade
104
APPENDIX
C
108
Airfoil
Catalogue
108
APPENDIX
D
111
Example
of
Aerodynamic
Data
and
Blade
Geometry
Input
for
Flex5
111
APPENDIX
E
113
Wind
Shear
Simulation
in
Flex5
113
Turbulence
Simulation
in
Flex5
115
REFERENCES
117
1.
Introduction
The
selection
of
airfoil
shape
directly
influences
the
efficiency
and
loading
of
wind
turbine
rotors.
In
this
graduate
project
at
Mälardalens
Högskola
and
carried
out
at
Statoil
Research
Center
in
Bergen,
Norway,
several
airfoils
have
been
investigated
for
use
in
offshore
wind
turbine
operation.
The
selected
airfoils
are
for
the
use
on
a
7.0
MW
turbine
with
a
diameter
of
165
m.
Statoil,
primary
an
oil
company,
is
also
involved
in
the
offshore
wind
turbine
industry,
especially
as
an
operator
of
wind
farms.
Statoil
has
an
interest
in
the
trends
in
turbine
size
and
airfoils
being
used.
The
first
part
of
the
report
is
a
study
of
performance
criteria
for
airfoils
and
blade
design.
Since
wind
turbine
operation
is
somewhat
different
to
aircraft
operation,
a
literature
study
was
performed.
An
introduction
to
the
history
of
wind
energy
and
development
trends
is
also
included.
Historical
wind
turbine
blades
were
studied
and
analyzed,
so
that
operational/test
data
and
software
data
could
be
compared
to
newer
turbines.
The
second
part
consists
of
airfoil
analyses,
primarily
for
the
middle
and
outer
sections
of
a
large
rotor
blade,
based
on
performance
criteria.
An
airfoil
catalogue
was
developed
including
aerodynamic
performance
data
and
roughness
insensitivity.
Experimental
data
and
analysis
tools,
such
as
XFoil
(XFLR5)
and
Javafoil
were
used.
The
third
part
of
the
report
is
the
main
part.
Blade
design
optimization
was
developed
in
Qblade.
By
combining
2D
airfoil
aerodynamic
performance
coupled
with
the
Blade
element
momentum
theory
and
a
3D
correction,
a
viable
result
was
achieved.
The
last
part
is
a
rotor
investigation
of
the
results
from
part
three.
This
was
done
in
aero-‐elastic
simulation
with
Flex5.
The
blade
optimized
in
Qblade
was
verified
by
employing
professional
software.
Since
this
is
a
public
report
in
collaboration
with
industry,
there
were
certain
limitations
to
the
use
of
airfoil
geometry.
Because
of
license
and
other
limitations,
only
airfoil
geometry
found
easily
on
the
Internet
was
investigated.
Therefore,
a
handful
of
different
airfoils
have
not
been
studied
in
this
project
and
entire
airfoil
families
have
been
excluded,
especially
the
Risøe
A-‐
family,
which
is
licensed,
tailored
wind
turbine
airfoils.
Since
the
airfoils
used
were
open
source,
there
was
no
opportunity
to
validate
the
correctness
of
the
airfoil
geometry.
An
assumption
was
made
that
they
are.
XFoil,
Qblade
and
Javafoil
only
account
for
steady
state,
incompressible
laminar
flow
while
the
real
operational
state
would
differ
from
this.
Compressibility
was
not
taken
account
of,
since
the
blade
rotation
will
be
less
than
Mach
0.3.
As
for
9
turbulent
flow
and
wind
shear,
which
a
real
turbine
will
encounter
during
normal
operation,
this
is
checked
in
Flex5.
A
wind
turbine
blade
designer
has
to
take
account
of
structural
limitations.
Because
of
the
limited
time,
the
project
did
not
include
a
structural
investigation
of
the
blades.
Avoiding
very
sophisticated
blade
structures
and
keeping
to
industry
standards,
the
structural
limitations
would
presumably
not
need
detailed
investigation.
General
losses
due
to
mechanical
and
electrical
efficiencies
have
not
been
analyzed.
Losses
have
been
set
at
3
%
for
calculations,
except
when
other
values
were
given.
2.
Historical
Perspective
A
wind
turbine
is
a
machine
that
converts
kinetic
energy
into
mechanical
energy
and
the
mechanical
energy
is
then
usually
converted
into
electrical
energy
through
a
generator.
There
are
two
major
types
of
wind
turbines:1
Horizontal-‐
axis
and
Vertical-‐axis,
the
horizontal
being
the
primary
type
used.
The
first
use
of
windmills
where
in
old
Persia
in
the
7th
century,
introduced
in
Europe
during
the
15th
century.
The
windmills
got
towers,
twisted
blades,
tapered
planforms
and
control
devices
to
point
the
mill
into
the
wind
in
the
17th
century.
The
Dutch
brought
the
windmill
expertise
to
North
America
in
the
18th
century,
where
wind
energy
was
used
to
pump
water.
The
first
horizontal-‐axis
wind
turbine
(HAWT)
for
generating
electricity
was
built
in
Scotland,
in
1887.
In
the
early
1890s,
the
Danish
scientist
Poul
la
Cour
was
the
first
to
discover
that
fast
rotating
turbines
with
fewer
rotor
blades
were
more
efficient
in
generating
electricity
over
slow
rotating
drag
or
impulse
wind
turbines.
In
1931
in
Yalta,
in
the
Soviet
Union,
a
predecessor
to
the
modern
HAWT
was
built.
It
had
a
30
m
high
tower
producing
100
kW.
The
wind
turbine
had
a
maximum
efficiency
of
32
%,
which
is
still
respectable
at
today’s
standards.
Ten
years
later,
the
pioneering
Smith
Putman
wind
turbine
was
built
in
Pennsylvania
and
ran
for
four
years,
until
it
encountered
a
blade
failure.
The
device
had
a
two-‐bladed
variable
pitch
rotor
working
downwind
of
the
tower.
The
rotor
was
53
meters
in
diameter
with
a
rotational
speed
of
28
rpm,
giving
a
peak
output
rating
of
1.25
MW
and
was
therefore
the
first
producing
in
excess
of
1
MW.
The
blades
were
untwisted
and
rectangular
with
a
chord
of
3.7m
and
consisted
of
NACA
4418
airfoil.
Ulrich
Hütter
pioneered
the
industry
in
Germany
during
the
1950´s
using
innovative
materials
and
designs
for
several
different
horizontal
axis
wind
turbines.
The
turbines
were
medium
sized
with
rotors
made
of
glass
fiber
10
Description:4.3.1 Airfoil Design for Wind Turbines With Roughness Insensitivity. 25. 4.3.2 Boundary Layer Theory. 28. 4.4 Blade Element Momentum (BEM) Theory. 32. 4.4.1 Momentum Theory. 32. 4.4.2 Blade Element Theory. 33. 4.5 Qblade. 38. 4.5.1 General Validation of Simulation Results. 38. 4.6 Javafoil. 39.
