low-noise technologies for wind turbine bladeselib.dlr.de/109601/1/ewea_mherr_17-11-2016.pdf ·...

> 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

[email protected]

mailto:[email protected]

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


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


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



Part 1: Experimental approach


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 …


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


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


Part 2: Numerical approach

DLR.de • Chart 11

Numerical approach DLR‘s CAA-Code PIANO with stochastic source model FRPM*


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


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!


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


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


OASPL, dB

c L,-

70 75 80 85 900

0.5

1

1.5


DLR.de • Chart 16



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


DLR.de • Chart 17



α, °

c L,-

-5 0 5 100

0.5

1

1.5


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


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


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


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


f1/3, kHz

SPL 1/

3,dB

5 10 152030

35

40

45

50

55

60

65

70


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


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


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


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


NACA 64-618αg = 7°; α = 4°u∞= 50 m/s

DLR.de • Chart 21


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


‘tripped’

‘clean’

αa ≈ 2° αa ≈ 3.5° αa ≈ 6°

50

brush extension

u∞

Future activity in BELARWEA

DLR.de • Chart 23

Summary & conclusions


• 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!

[email protected]

• This work has been conducted within the project BELARWEA (ref. 0325726) funded by the German Federal Ministry for Economic Affairs and Energy (BMWi).


low-noise technologies for wind turbine bladeselib.dlr.de/109601/1/ewea_mherr_17-11-2016.pdf ·...

Documents