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Wind Turbine Noise and Vibration
9/05/20081
Wind Wind
Turbine Turbine
Noise and Noise and
VibrationVibration
Dr. Colin KestellDr. Colin Kestell
[email protected]@adelaide.edu.au
2
Introduction
Colin Kestell
Senior Lecturer
School of Mechanical Engineering
The University of Adelaide
Engineering Manager until 1997
PhD (Active control of sound in a small single engine
aircraft cabin with virtual error sensors) in 2000
Teach Engineering Design
3
An audible vibration transported to the
observer through an elastic solid or fluid.
tympanicmembrane(eardrum)
malleus(hammer)
incus(anvil)
cochlea
stapes (stirrup)
vibratingbody
disturbed viscous fluid
Noise, Where does it come from?4
Sound – Our perception of sound
20Hz 1KHz 22KHz
50dBA weighting
5
Sound
0dB
10dB
20dB
30dB
40dB
50dB
60dB
70dB
80dB
90dB
100dB
110dB
120dB
130dB
140dB
150dB
20
100
1000
100,000
1,000,000
10,000,000
10,000
100,000,000
µPascals
2
2
log10refp
pdB =
pref = 20 x10-6 Pascals
refp
plog20=
Hearing threshold
Important to state
distance from source
Pain
350m away
6Measuring SoundFor a point source radiating into a
free field, where the object is small
relative to the distance
)(10
)(10
2
2.
ref
measp
ref
sourceW
p
pLogL
W
WLogL
=
=
Pascalspref µ20=
WattsxWref
12101
−=
rif rLL
r
rLogLL
dBrLogLL
dBrLogLL
pp
pp
pw
Wp
1212
1
212
2 dB6
)(20
8)(20
8)(20
=−=
−=
++=
−−=
Fundamentals of Noise and Vibration. M.P.Norton
r
Wind Turbine Noise and Vibration
9/05/20082
7Measuring SoundFor a line source radiating into
a free field, where the object is
small relative to the distance
rif rLL
r
rLogLL
dBrLogLL
dBrLogLL
pp
pp
pw
Wp
1212
1
212
2 dB3
)(10
5)(10
5)(10
=−=
−=
++=
−−=
Fundamentals of Noise and Vibration. M.P.Norton
)(10
)(10
2
2.
ref
measp
ref
sourceW
p
pLogL
W
WLogL
=
=
Pascalspref µ20=
WattsxWref
12101
−=
r
8
50 dB
Measuring Sound
9
.......)1010(10 101021
++=
LpLp
T LogLp
53 dB
Measuring Sound 10
Types of noise
Tonal Noise
440Hz
1000Hz
10000 Hz
Random Noise
White Noise
Pink Noise
Time domain Time averaged(s) Frequency domain (Hz)
Time (s) Frequency (Hz)
Measuring Sound
11
Instrumentation - sound
A Sound Level Meter
A Microphone
A windsock
Conditioning amplifier
Spectrum Analyser
Measuring Sound12Vibration
Structure-borne vibration transmits energy throughout the entire system.
The displacement of a surface is the combined contribution of all of its modes. Which mode is
excited the most is dependent on the source.
Each and every exterior surface will radiate sound
energy
The effectiveness of this radiation is known as the ‘radiation efficiency’
Wind Turbine Noise and Vibration
9/05/20083
13
Vibration
Measured in terms of
Displacement
Velocity
Acceleration – sometimes in terms of ‘g’ (gravity)
dB also used … or
absolute units on either a logarithmic or linear scale
Be careful of units!
All this and more covered in Part IIA 3C6 Vibrationand Part IIB 4C6 Advanced Linear Vibration
Measuring Vibration 14
Measuring sound and vibrationInstrumentation - vibration
Conditioning amplifier
Spectrum Analyser
Accelerometer Strain gauge
Laser vibrometer
15
Measuring sound and vibrationCalibration
16
Wind Turbine Noise
17
What generates the noise in wind
turbines ?
18
Wind Turbine Noise1. Blades2. Rotor3. Pitch4. Brake5. Low speed shaft6. Gear box7. Generator8. Controller9. Anemometer
13. Yaw drive14. Yaw Motor15. Tower
10. Wind Vane11. Nacelle12. High speed shaft
Wind Turbine Noise and Vibration
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Note, much larger gearbox and hence many more moving parts
20
Aerodynamic Noise
Blade passes through turbulent, often gusty flow
Blade motion causes turbulence
Wing tip vortices
cause turbulence
Turbulence
creates sound
(broadband audible
pressure perturbations)
Turbulence higher as
each blade passes tower
Consider a 3 blade, 26 RPM rotor
will have a BPF of 1.3 Hz
21
Aerodynamic Noise
A 3 blade, 26 RPM rotor will have a tower BPF of
1.3 Hz, or a periodic time of 0.77 seconds
0.77s
22
23
Shaft noise unbalanced
bent shafts
non-concentric alignment
60)(
RPMHzfrequency =
24
Shaft noise
60)(
RPMHzfrequency =
Wind Turbine Noise and Vibration
9/05/20085
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Shaft noise
Frequency (Hz)
Amplitude
Varies with shaft speed
60)(
RPMHzfrequency =
26
Shaft noise
27
Gear Noise
Frequency (Hz)
Amplitude
Vary with speed
60)(
RPMHzfrequencyShaft =
60.)( RPM
NHzfrequencyMesh = Gear with N teeth
28
Gear Noise
Consider gear pairs with a simple ratio: 2:1, 3:1 etc
Periodically the same teeth will mesh
At a frequency equal to the shaft frequency of the larger gear
One full revolution of the large gear, also returns the small gear to the same place
29
Gear Noise
Gears that share common multiples also mesh the same two teeth periodically.
Consider: a 40 tooth pinion anda 60 tooth sprocket,
Turn the sprocket TWO FULL turns, moving 120 teeth past a point.
This moves 120 teeth on the pinion, driving it THREE FULL turns.
30
Gear Noise
This cyclic nature is known as the HUNTING TOOTH.
The frequency is equal to:Gear mesh frequency
Lowest Common Tooth Multiple
This causes uneven wear
Choose tooth numbers that result in a high ‘lowest common multiple’ to keep this
frequency as low as possible
This is why gears have apparently
strange teeth numbers
Wind Turbine Noise and Vibration
9/05/20086
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Gear Noise
F1
F2Drive speed
Probable 14 tooth gear issue
32
Gear Noise
http://www.vibanalysis.co.uk/
33
Gear NoiseGear Box Failure
34
Normal spur gears – cost effective
Helical gears – smoother mesh,more expensive, produce an axialforce component as well as a tangential
Herring bone gears (far more expensive)realign the resultant force
Gear Noise
35
Bearing Noise http://www.vibanalysis.co.uk/36Generator Noise
A typical 3-phase generator will have
3 pairs of (6) opposing wound coils
4 rotating permanent magnets
Producing 12 pulses per revolution
Wind Turbine Noise and Vibration
9/05/20087
Vibration isolation
m
k=ω
Frequency (Hz)
Displacement
Increased damping
Increase mass ordecreased stiffness
m
c k
38
Acoustic resonance
The large tower will act like an organ pipe
Broadband and tonal noise will propagate through
the duct and excite standing wave resonances
39
Radiation40
ExamplesVesta V52-850 kW, 3 Blade, 26 RPM
Psycho-acoustic characters of relevance for annoyance of wind turbine noise.K. Persson Waye and E. Og Hrstrog M. journal of sound and vibration (2002) 250(1), 65-73
41
ExamplesWindWorld 600kW, Enecon 500kW
Psycho-acoustic characters of relevance for annoyance of wind turbine noise.K. Persson Waye and E. Og Hrstrog M. journal of sound and vibration (2002) 250(1), 65-73
42
0 5 10Time (s)
25
5000
Frequency (Hz)
0 20dBAfrom 70m
40 60
Wind turbines and sound: Review andbest practice guidelines. HGC Engineering
Canadian 1.5 MW Wind Turbine SpectogramExamples
Wind Turbine Noise and Vibration
9/05/20088
43
Wind turbines and sound: Review andbest practice guidelines. HGC Engineering
Acoustic model oftypical wind turbine
sound propagation
Examples44
Noisy or quiet?
0dB
10dB
20dB
30dB
40dB
50dB
60dB
70dB
80dB
90dB
100dB
110dB
120dB
130dB
140dB
150dB
20
100
1000
100,000
1,000,000
10,000,000
10,000
100,000,000
µPascals
2
2
log10refp
pdB =
pref = 20 x10-6 Pascals
refp
plog20=
Hearing threshold
Important to state distance from source
Pain
350m away
Machinery health monitoring
Baseline measurementSubsequent measurement
In-situ microphones, strain gauges and
accelerometers on
Rotating machinery
Critical structures
46
Many claim that the noise is worse at night or in the early hours of the morning.
Less masking(other noises
covering it up)
Physiological issues
Meterological effects
Noisy or quiet?
47
Noisy or quiet?
Normal conditions
48
Warmer air thermal inversion layer
One of a few meteorological effects
Noisy or quiet?
