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> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 1
Low-Noise Technologies for Wind Turbine Blades Michaela Herr, Roland Ewert, Benjamin Faßmann, Christof Rautmann, Susanne Martens, Claas-Hinrik Rohardt & Alexandre Suryadi Institute of Aerodynamics and Flow Technology – Technical Acoustics German Aerospace Center (DLR), Braunschweig, Germany WindEurope Tech Workshop Wind Turbine Sound 2016 17–18 November 2016, Gdansk, Poland
michaela.herr@dlr.de
DLR.de • Chart 2
Background
source: R. Drobietz, GE Wind Energy
rotor blade noise
frequency
dB(A
)
blade tip trailing edge
frequency
dB(A
)
trailing edge (TE)
• Modern large turbines typically involve sufficient treatment of machinery noise, so that mainly flow-induced noise by the blades contributes to the total noise emission.
• Trailing-edge noise (TEN) in the outer 20–25% of rotor radius is the dominant contributor to total wind turbine noise.
• Knowledge from aerospace-related TEN studies & applications can be directly transferred due to same noise generation (& reduction) mechanisms.
Source: http://www.acoustic-camera.com
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
source: S. Oerlemans, AIAA 2016
• Development and validation of improved methods for the design of both efficient and low-noise wind turbine rotors, i.e. high-fidelity 2D/3D CFD- & CAA- methods for
• 2D profile design • 3D winglet design
• Demonstration of minimum 3-dB noise reduction for given rotor performance through 3D redesign of outer 20% of rotor radius (phase 1: in AWB & DNW-NWB wind tunnels)
• Adaptation of passive noise reduction technologies from aerospace applications
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 3
Research aim in BELARWEA Blattspitzen für Effiziente und Lärmarme Rotoren von Windenergieanlagen
‘DESIGNBOX‘ (struct. & aero. constraints) @ scaled NREL-5MW reference rotor
2D-profile design: XFOIL polars (forces + moments) 2D CAA noise driving parameters ‘acoustic profile catalogue‘
variant 1: rotor blade with new profile @ outer 20% R
3D-blade design: Lifting line method + CFD 3D CAA aeroacoustic analysis variant 2: rotor blade with winglet
@ outer 4% R ( reduction of R)
TE add-ons to reference / variant 1 / variant 2
NACA 64-618
• Development and validation of improved methods for the design of both efficient and low-noise wind turbine rotors, here: high-fidelity 2D CFD- & CAA- methods for
• 2D profile design • 3D winglet design
• Demonstration of minimum 3-dB noise reduction for given reference performance in AWB wind tunnel
• Adaptation of passive noise reduction technologies from aerospace applications
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 4
Research aim in BELARWEA Blattspitzen für Effiziente und Lärmarme Rotoren von Windenergieanlagen
TODAY‘S PRESENTATION
2D-profile design:
2D CAA
aeroacoustic assessment of new profile design RoH-W-18%c37
TE add-ons to reference / new profile
NACA 64-618
DLR.de • Chart 5
Scope
• Part 1: Experimental approach Limitations of current TEN data sets (TEN benchmarks) • Part 2: 2D Numerical approach
• Part 3: Results
Results for design conditions vs. wind tunnel conditions Comparison of numerical with experimental data Noise reduction potential of porous TE extensions
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 6
Part 1: Experimental approach
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 7
TEN measurements Experience from ongoing TEN benchmark activities (AIAA BANC* workshops) • TEN is a very low intensity noise source, i.e. focusing measurement technos. or
specific source correlation technologies are necessary! • High-quality measurements are challenging, in particular, if efficient noise reduction
devices are applied! • Single free-field microphone measurements will contain all existent facility-
inherent extraneous noise sources & TEN is generally masked • Side-plate / model junction noise sets low frequency limit (≥ 1–1.25 kHz in the
current study) TEN maximum often located at these low frequencies!
• TEN benchmark data are limited (and still reflect a large +/- 3 dB scatter band among test facilities!) because data rely on individual calibrations & source assumptions…
• Combined numerical/experimental approaches are necessary (common rationale
behind BANC activity) reconstruction of the low-frequency range
AIAA-2013-2123 AIAA-2015-2847 2012: BANC-II-1 2014: BANC-III-1
*BANC: Benchmark Problems for Airframe Noise Computations Category 1: TEN 2016: BANC-IV-1 …
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 8
TEN measurements DLR‘s Acoustic Wind Tunnel Braunschweig (AWB) • AWB operational data:
• nozzle: 0.8 m by 1.2 m • max. speed: 65 m/s • Tu < 0.3 % @ 60 m/s
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 9
TEN measurements DLR‘s Acoustic Wind Tunnel Braunschweig (AWB) • AWB operational data:
• nozzle: 0.8 m by 1.2 m • max. speed: 65 m/s • Tu < 0.3 % @ 60 m/s
• 2 WT blade airfoils: • NACA64-618 vs. RoH-W-18%c37 (new low-
noise design) • profile chord length lc = 0.3 m (0.8 m span) • @ ‘clean’ and ‘tripped’ TBL conditions • @ varying a-o-a • @ varying WT speeds u∞ = 40/50/60 m/s
(Remax = 1.2 Mio.)
NACA 64-618
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 10
Part 2: Numerical approach
DLR.de • Chart 11
Numerical approach DLR‘s CAA-Code PIANO with stochastic source model FRPM*
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
000 ,, pu ρCFD
RANS
4D-Stochastic Sound Sources FRPM*
CAA APE Sound Field
vortex sound sources
turbulence
source
p′
Spectral analysis
*Ewert, Comp. & Fluids (Vol. 37)
mean flow; here: DLR code TAU with SST
AIAA-2009-3269 AIAA-2014-3298
DLR.de • Chart 12
Example benchmark results • Overview on selected comparison measurement data from BANC-IV
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
array @ VTST CPV @ IAG LWT fc, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
90CASE#2, averaged measurement dataCASE#5, DLR AWB (60 m/s, 4deg, 0.3m)CASE#7, VTST (44.98m/s, 4.62deg)
DTU/VTST + Kevlar - array
DLR - mirror
average IAG/DLR – CPV/mirror
NACA 64-618
fc, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
90CASE#2, DLRCASE#5, DLRCASE#7, DLR, θ = 255.8°
fc, kHzL p
(1/3
),dB
5 10 15 2030
40
50
60
70
80
90CASE#2, DTUCASE#5, DTUCASE#7, DTU, θ = 255.8°
DTU simulation DLR simulation
BANC-IV-1
DLR.de • Chart 13
Example benchmark results • Results are promising & indicate the applicability of PIANO/FRPM for low-noise
design purposes!
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
fc, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
90CASE#2, averaged measurement dataCASE#5, DLR AWB (60 m/s, 4deg, 0.3m)CASE#7, VTST (44.98m/s, 4.62deg)
DTU/VTST + Kevlar - array
DLR - mirror
average IAG/DLR – CPV/mirror
NACA 64-618
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016 DLR.de • Chart 14
Part 3: Results
DLR.de • Chart 15
Numerical results for design conditions > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
• Re = 3 Mio. • M = 0.2 • u∞ = 68 m/s • lc = 0.65 m • targeted cL = 1.15
α, °
c L,-
-5 0 5 100
0.5
1
1.5
NACA 64-618; FULRoH-W-18%c37; FULNACA 64-618; NATRoH-W-18%c37; NAT
cD, -c L,
-
0.005 0.01 0.0150
0.5
1
1.5
NACA 46-618; FULRoH-W-18%c37; FULNACA 46-618; NATRoH-W-18%c37; NAT
OASPL, dB
c L,-
70 75 80 85 900
0.5
1
1.5
NACA 46-618; FULRoH-W-18%c37; FULNACA 46-618; NATRoH-W-18%c37; NAT
DLR.de • Chart 16
Numerical results for design conditions > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
• Re = 3 Mio. • M = 0.2 • u∞ = 68 m/s • lc = 0.65 m • targeted cL = 1.15
α, °
c L,-
-5 0 5 100
0.5
1
1.5
NACA 64-618; FULRoH-W-18%c37; FULNACA 64-618; NATRoH-W-18%c37; NAT f1/3, kHz
SPL 1/
3,dB
5 10 15
60
70
80
OASPL, dB(A)
c L,-
70 75 80 85 900
0.5
1
1.5
NACA 46-618; FULRoH-W-18%c37; FULNACA 46-618; NATRoH-W-18%c37; NAT
DLR.de • Chart 17
Numerical results for design conditions > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
• Re = 3 Mio. • M = 0.2 • u∞ = 68 m/s • lc = 0.65 m • targeted cL = 1.15
α, °
c L,-
-5 0 5 100
0.5
1
1.5
NACA 64-618; FULRoH-W-18%c37; FULNACA 64-618; NATRoH-W-18%c37; NAT f1/3, kHz
SPL 1/
3,dB
5 10 15
60
70
80
OASPL, dB
c L,-
70 75 80 85 900
0.5
1
1.5
DLR.de • Chart 18
Numerical results for AWB conditions > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
α, °
c L,-
-5 0 5 100
0.5
1
1.5
NACA 64-618; FULRoH-W-18%c37; FULNACA 64-618; NATRoH-W-18%c37; NAT f1/3, kHz
SPL 1/
3,dB
5 10 15
60
70
80• Re = 1.23 Mio. • M = 0.176 • u∞ = 60 m/s • lc = 0.3 m • targeted cL = 1.15
DLR.de • Chart 19
Comparison of numerical with experimental data > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 4°; α = 2°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 7°, α = 3.5°u∞= 50 m/s
f1/3, kHzSP
L 1/3,
dB5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 11°, α = 6°u∞= 50 m/s
• Almost perfect predictions for new design RoH-W-18%c37 • ‘CLEAN’ (42%/57%) vs. ‘TRIPPED’ (5%/10%):
• Significant effect of laminar TBL extent on noise!
• But…
DLR.de • Chart 20
Comparison of numerical with experimental data > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 4°; α = 2°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 7°, α = 3.5°u∞= 50 m/s
f1/3, kHzSP
L 1/3,
dB5 10 152030
35
40
45
50
55
60
65
70
AWB; tripped (42%/57%)AWB; tripped (5%/10%)CAA; tripped (42%/57%)CAA; tripped (5%/10%)
RoH-W-18%c37αg = 11°, α = 6°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; cleanAWB; tripped (5%/10%)CAA; cleanCAA; tripped (5%/10%)
NACA 64-618αg = 4°; α = 2°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; cleanAWB; tripped (5%/10%)CAA; cleanCAA; tripped (5%/10%)
NACA 64-618αg = 11°; α = 6.7°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; cleanAWB; tripped (5%/10%)CAA; cleanCAA; tripped (5%/10%)
NACA 64-618αg = 7°; α = 4°u∞= 50 m/s
DLR.de • Chart 21
Comparison of numerical with experimental data > WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; RoH-W-18%c37AWB; NACA 64-618CAA; RoH-W-18%c37CAA; NACA 64-618
tripped (5%/10%)αg = 11°, α = 6°/6.7°u∞= 50 m/s
f1/3, kHz
SPL 1/
3,dB
5 10 152030
35
40
45
50
55
60
65
70
AWB; RoH-W-18%c37AWB; NACA 64-618CAA; RoH-W-18%c37CAA; NACA 64-618
'clean'αg = 11°, α = 6°/6.7°u∞= 50 m/s
x/lc, -
c p,-
0 0.2 0.4 0.6 0.8 1
-2.5
-2
-1.5
-1
-0.5
0
0.5
1AWB MeasurementCFD Simulation (Tau)
NACA 64-618cleanαg = 11°, α = 6.7°u∞= 50 m/s
x/lc, -
c p,-
0 0.2 0.4 0.6 0.8 1
-2.5
-2
-1.5
-1
-0.5
0
0.5
1AWB MeasurementCFD Simulation (Tau)
NACA 64-618tripped (5%/10%)αg = 11°, α = 6.7°u∞= 50 m/s
• …poor prediction quality for ‘TRIPPED’ NACA 64-618 reference profile leads to wrong TEN deltas between the two airfoils!
• Design conditions cannot be reproduced in open-jet AWB experiment due to early TE separation (which is not predicted)
• principle noise reduction effect for selected TEN reduction technologies confirmed, here shown for low-noise RoH-W-18%c37 airfoil
DLR.de • Chart 22
Experimental results for TE add-ons Additional noise reduction potential of selected TE extensions
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
‘tripped’
‘clean’
αa ≈ 2° αa ≈ 3.5° αa ≈ 6°
50
brush extension
u∞
Future activity in BELARWEA
DLR.de • Chart 23
Summary & conclusions
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
• Results from a numerical & experimental aeroacoustic assessment of 2D wind turbine blade sections were presented
• 2–4 dB (OASPL) noise benefit RoH-W-18%c37 re. NACA 64-618 (predicted for design conditions)
• Up to 8 dB noise benefit, if a maximum laminar extent of the TBL can be realized • Additional 4–6 dB reduction of TEN peak levels realizable through flow-
permeable TE extensions (note that the lift either remains unchanged or increases for the tested flap extensions)
• Overall, very promising results obtained w.r.t. the next steps within BELARWEA; open questions are related to the ‘TRIPPED’ NACA 64-618 reference profile
• 3D winglet design & 3D CFD/CAA simulations
• Test of 3D blade sections (outer 20% R) in DNW-NWB to validate 3D approach;
model instrumentation with Kulites & measurements in open vs. closed test section environment will provide additional clarification of the observed discrepancies between simulations and measurements for the ‘TRIPPED’ NACA 64-618
DLR.de • Chart 24
Thank you for your attention!
michaela.herr@dlr.de
• This work has been conducted within the project BELARWEA (ref. 0325726) funded by the German Federal Ministry for Economic Affairs and Energy (BMWi).
> WindEurope Tech Workshop Wind Turbine Sound 2016 > Michaela Herr > 17 November 2016
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