SIROCCO, SIlant ROtors by aCoustiC Optimisation Participants: Energy Research Centre of the...
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Transcript of SIROCCO, SIlant ROtors by aCoustiC Optimisation Participants: Energy Research Centre of the...
SIROCCO, SIlant ROtors by aCoustiC OptimisationParticipants:
Energy Research Centre of the Netherlands, ECN (Gerard Schepers and Toine Curvers)
National Aerospace Laboratory, NLR(Stefan Oerlemans)
University of Stuttgart, Ustutt(Kurt Braun, Andreas Herrig, Thorsten Lutz, Werner Wuerz)
Gamesa Aeólica, Gamesa(Beatriz Mendez López, Alvaro Matesanz)
GE Wind Energy/Global Research, GE (Rainer Arelt, Thierry Maeder)
Funded by: EU 5th Framework SenterNOVEM (ECN/NLR)
OUTLINE
OBJECTIVE PROJECT SET-UP (Period, participants, tasks) MAIN RESULTS
• RESULTS FROM PHASE 1: ACOUSTIC ARRAY MEASUREMENTS
• RESULTS FROM PHASE 2: DESIGN AND VALIDATION OF ACOUSTIC AIRFOIL DESIGN
CONCLUSIONS/FUTURE WORK
SIROCCO, OBJECTIVE
To develop ‘tip’-airfoils (r/R >0.75) by which aerodynamic noise of wind turbines can be reduced significantly without loss in aerodynamic performance;
Focus is on reduction of trailing edge noise!
Background: Previous EU project ‘DATA’:
• Noise reduction of 3-6dB(A) on model wind turbine in the DNW wind tunnel;
•Trailing edge noise dominant
SIROCCO, OBJECTIVE Ctd.Two ‘baseline’ turbines:
Gamesa (G58, D=58 m, 850 kW, at Zaragoza) GE (2.3 MW, D=94 m, at ECN test field)
OUTLINE
OBJECTIVE PROJECT SET-UP (Period, participants, tasks) MAIN RESULTS
• RESULTS FROM PHASE 1: ACOUSTIC ARRAY MEASUREMENTS
• RESULTS FROM PHASE 2: DESIGN AND VALIDATION OF ACOUSTIC AIRFOIL DESIGN
CONCLUSIONS/FUTURE WORK
Sirocco: Project period
January 1st 2003 until February 28th 2007
GE joined project in May 2005
SIROCCO, 4 phases
1) Start-up phase: Is acoustic behaviour of baseline turbines as expected, i.e. is trailing edge noise dominant? • Acoustic array measurements: Location and quantification of
noise sources on wind turbine blade
2) 2D design phase: Design and test acoustically optimised airfoils• Development of aero-acoustic design method• Supported by 2D wind tunnel measurements
3) 3D design and manufacturing4) Final validation in the field: Compare acoustic and ‘aerodynamic’
behaviour of optimised turbine and reference turbine
SIROCCO: Participants, main role
Energy Research Centre of the Netherlands, ECN: Coordination, design consultancy, ‘aerodynamic’ field measurements
National Aerospace Laboratory, NLR: Acoustic measurements: Field and wind tunnel (2D)
University of Stuttgart: Development design methodology for acoustically optimised airfoils; Design of acoustically optimised airfoils; Validation: Wind tunnel (2D): Aerodynamic and acoustic
Gamesa: Design of blades with optimised airfoils and manufacturing
GE Wind Energy Design of blades with optimised airfoils and manufacturing
OUTLINE
OBJECTIVE PROJECT SET-UP (Period, participants, tasks) MAIN RESULTS
• RESULTS FROM PHASE 1: ACOUSTIC ARRAY MEASUREMENTS
• RESULTS FROM PHASE 2: DESIGN AND VALIDATION OF ACOUSTIC AIRFOIL DESIGN
CONCLUSIONS /FUTURE WORK
Is trailing edge noise the dominant noise source?
Answer yes as derived from NLR’s acoustic array measurements on GE2.3 turbine/G58 turbine
Assume monopole source at scan point Location and quantification of noise
sources on rotating wind turbine blades
Sound rays
Scan points
Microphone array
Delay&sum
GE
G58
-70
-65
-60
-55
-50
-10 -5 0 5 10
[m]
[m]
Platform: 15 x 18 m2
152 mics
Acoustic array measurements: Some observations
•Turbine noise dominated by rotor blades
•Noise radiated from outer part of blades (but not the very tip)
•Practically all blade noise (emitted to ground) produced during downward movement
GE
G58
Dominance of down-going blades
The down-going blades are dominant for all frequencies and all measurements
Indication for trailing edge noise to be dominant
Can be explained by combination of: Convective amplification Trailing edge noise directivity
sin2(/2)
4
22
)cos1(
sin )2/(sin2
MD
0 60 120 180 240 300 360-10
-5
0
5
10
Rotor azimuth (degrees)
dirconvtotal
dSP
L (d
B)
Noise sources on individual G58 blades (clean, untreated, tripped)Typical source plots for individual blades
Rotating focus plane for each blade Averaged over downward part of one rotation
– Tripped blade significantly noisier than other two
– Indication for TE-noise to be dominant
Clean Untreated Tripped
0 dB
12 dB
TE-noise dominant in calculations, but howgood are the calculations?
Spin-off: Use measurements to validate wind turbine noise prediction code SILANT
SILANT
Originally developed by Stork Product Engineering, NLR and TNO ECN
Divide blade in a number of blade elements Calculate noise spectrum per element:
–Inflow noise: Amiet and Lowson–Trailing edge noise: Brooks Pope and
Marcolini–
p and s at trailing edge from XFOIL and
blade element momentum model Sum over elements
SILANT/meas (noise vs. power)
90
95
100
105
110
0 100 200 300 400 500 600 700 800 900
Power (kW)
OA
SP
L (
dB
A)
measured (cleanblades)
SILANT
2nd order fit (SILANT)
2nd order fit (measured)
Measured spectrum vs SILANT spectrum: Total noise, trailing edge noise, inflow noise
Indications for TE-noise to be dominant
1. Practically all blade noise (emitted to the ground) produced during downward movement Directivity of trailing edge noise
2. Tripped blade significantly noisier than other two Tripping influences trailing edge noise
3. Calculated results show TE noise to be dominant above inflow noise
4. Blade noise levels scale with 5th power of local speed Dependancy of trailing edge noise
Broadband TE noise is the dominant noise source
OUTLINE
OBJECTIVE PROJECT SET-UP (Period, participants, tasks) MAIN RESULTS
• RESULTS FROM PHASE 1: ACOUSTIC ARRAY MEASUREMENTS
• RESULTS FROM PHASE 2: DESIGN AND VALIDATION OF ACOUSTIC AIRFOIL DESIGN
CONCLUSIONS/FUTURE WORK
Main results: Phase 2: 2D design phase
Design philosophy: Modify boundary layer at trailing edge Improved noise airfoil prediction code coupled to an aerodynamic
airfoil prediction code and optimizer– Requirements/constraints of manufacturers implemented
Aerodynamics Acoustics Mean boundary layer profile + turbulent properties at trailing edge
Using boundary layer wind tunnel measurements on airfoil with Variable Trailing Edge (VTE)
ORIGINAL LINK BETWEEN AERODYNAMIC/AERO-ACOUSTIC MODELLING
– Mean boundary layer profile assumed to be a Coles profile:
- Derived from integral boundary-layer parameters
– Turbulence properties:- v’2 ,Kt derived from mean boundary layer profile
with mixing length approach- Vertical integral length scale (Λ2) from mixing
length scale and scaling law– Equilibrium approach!!– Anisotropy is constant factor
DESIGN METHOD: IMPROVEMENTS MADE DURING SIROCCO PROJECT
History and anisotropy effects important for flow regions with acceleration/deceleration
– EDDYBL FD boundary-layer code with stress-ω model (Wilcox)
Vertical integral length scale Λ2 is not provided by available turbulence models
– adequate scaling laws required
– Directly found from Λ2 measurements in the wind tunnel
Aerodynamic validationLWT tunnel of USTUTT
closed test section 0.73x2.73 m2
Aerodynamic/Acoustic validation in windtunnel
LWT AWB
Acoustic validation: 1) AWB tunnel (NLR): Array technique
•Open jet•1.2x0.8 m2
2) LWT tunnel (USTUTT): CPV technique
CPV: Coherent Particle Velocimetry:Measurement of particle velocitieswith hot-wire at pressure and suction side of airfoil TE, instead of(microphone) measurement of pressure fluctuations
Re=1.6 106
Clean/tripped airfoils
GE Gamesa
Dragpolars
Noisepolars
OUTLINE
OBJECTIVE PROJECT SET-UP (Period, participants, tasks) MAIN RESULTS
• RESULTS FROM PHASE 1: ACOUSTIC ARRAY MEASUREMENTS
• RESULTS FROM PHASE 2: DESIGN AND VALIDATION OF ACOUSTIC AIRFOIL DESIGN
CONCLUSIONS/FUTURE WORK
Conclusions/Future work
Acoustic array measurements very successfully applied on full scale turbine: Trailing edge noise is dominant
Design methodology for acoustically optimised airfoil has been improved and validated successfully in wind tunnel
New airfoils:– Noise reduction: 1-1.5 dB and 2.5-2.9 dB– Aerodynamic characteristics hardly changed
Blade design/manufacturing underway Full scale validation with hybrid rotor in April 2006/Autumn
2006