Transcript Document 7143424

Wind
Turbine
Noise and
Vibration
Dr. Colin Kestell
[email protected]
Noise, Where does it come from?
7
Noise, Where does it come from?
An audible vibration transported to the
observer through an elastic solid or fluid.
vibrating
body
malleus
(hammer)
cochlea
disturbed
viscous fluid
tympanic
membrane
(eardrum)
incus stapes
(anvil) (stirrup)
8
Sound – Our perception of sound
9
A weighting
50dB
20Hz
1KHz
22KHz
μPascals
Sound
p2
dB  10 log 2
pref
p
 20 log
pref
pref = 20 x10-6 Pascals
100,000,000
10,000,000
1,000,000
100,000
10,000
350m away
1000
Important to state
distance from source
100
20
10
150dB
140dB
130dB
120dB
Pain
110dB
100dB
90dB
80dB
70dB
60dB
50dB
40dB
30dB
20dB
10dB
0dB Hearing threshold
Measuring Sound
11
For a point source radiating into a
free field, where the object is small
relative to the distance
r
Lp  LW  20Log(r )  8dB
Lw  Lp  20Log(r )  8dB
Lp 2
r2
 Lp1  20Log( )
r1
Lp 2  Lp1  6dB
if r2  2r1
LW  10Log(
Wsource
)
Wref
2
pmeas
Lp  10Log( 2 . )
pref
Wref  1x1012Watts
pref  20Pascals
Fundamentals of Noise and Vibration. M.P.Norton
Measuring Sound
12
For a line source radiating into
a free field, where the object is
small relative to the distance
r
Lp  LW  10Log(r )  5dB
Lw  Lp  10Log(r )  5dB
Lp 2
r2
 Lp1  10Log( )
r1
Lp 2  Lp1  3dB
if r2  2r1
LW  10Log(
Wsource
)
Wref
2
pmeas
Lp  10Log( 2 . )
pref
Wref  1x1012Watts
pref  20Pascals
Fundamentals of Noise and Vibration. M.P.Norton
Measuring Sound
13
Measuring Sound
LpT  10Log(10
Lp1
10
14
 10
Lp2
10
 .......)
Measuring Sound
Types of noise
Time domain
(s)
15
Time averaged
Frequency domain (Hz)
Tonal Noise
440Hz
1000Hz
10000 Hz
Time (s)
Random Noise
White Noise
Pink Noise
Frequency (Hz)
16
Measuring Sound
Instrumentation - sound
A windsock
A Microphone
A Sound Level Meter
Conditioning amplifier
Spectrum Analyser
Vibration
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’
17
Measuring Vibration
18
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 Vibration
and Part IIB 4C6 Advanced Linear Vibration
Measuring sound and vibration
Instrumentation - vibration
Conditioning amplifier
Laser vibrometer
Accelerometer
Strain gauge
Spectrum Analyser
19
Measuring sound and vibration
Calibration
20
Wind turbines
21
Wind Turbine Noise
22
23
What generates the noise in wind
turbines ?
Wind Turbine Noise
10. Wind Vane
11. Nacelle
12. High speed shaft
1.
2.
3.
4.
5.
6.
7.
8.
9.
Blades
24
Rotor
Pitch
Brake
Low speed shaft
Gear box
Generator
Controller
Anemometer
13. Yaw drive
14. Yaw Motor
15. Tower
25
Note, much larger gearbox and
hence many more moving parts
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
26
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
27
28
Shaft noise
29
unbalanced
bent shafts
non-concentric alignment
RPM
frequency (Hz) 
60
Shaft noise
RPM
frequency (Hz) 
60
30
31
Shaft noise
Amplitude
Varies with shaft speed
Frequency (Hz)
RPM
frequency (Hz) 
60
Shaft noise
32
33
Gear Noise
Amplitude
RPM
Shaft frequency (Hz) 
60
Vary with speed
Frequency (Hz)
RPM
Mesh frequency (Hz)  N.
60
Gear with N teeth
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
34
Gear Noise
Gears that share common multiples also
mesh the same two teeth periodically.
Consider:
a 40 tooth pinion and
a 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.
35
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
36
37
Gear Noise
Probable 14 tooth
gear issue
Drive speed
F2
F1
Gear Noise
http://www.vibanalysis.co.uk/
38
Gear Noise
Gear Box Failure
39
Gear Noise
Normal spur gears – cost effective
Helical gears – smoother mesh,
more expensive, produce an axial
force component as well as a tangential
Herring bone gears (far more expensive)
realign the resultant force
40
Bearing Noise
http://www.vibanalysis.co.uk/
41
Generator Noise
A typical 3-phase generator will have
3 pairs of (6) opposing wound coils
4 rotating permanent magnets
Producing 12 pulses per revolution
42
Vibration isolation
m
k
m

c
k
Increase mass or
decreased stiffness
Displacement
Increased damping
Frequency (Hz)
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
44
Radiation
45
Examples
Vesta 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
46
Examples
WindWorld 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
47
48
Examples
Canadian 1.5 MW Wind Turbine Spectogram
0
20
40
dBA from 70m
60
Frequency (Hz)
5000
Wind turbines and sound: Review and
best practice guidelines. HGC Engineering
25
0
5
Time (s)
10
Examples
Acoustic model of
typical wind turbine
sound propagation
Wind turbines and sound: Review and
best practice guidelines. HGC Engineering
49
Noisy or quiet? μPascals
p2
dB  10 log 2
pref
p
 20 log
pref
pref = 20 x10-6 Pascals
100,000,000
10,000,000
1,000,000
100,000
10,000
350m away
1000
Important to state
distance from source
100
20
50
150dB
140dB
130dB
120dB
Pain
110dB
100dB
90dB
80dB
70dB
60dB
50dB
40dB
30dB
20dB
10dB
0dB Hearing threshold
Noisy or quiet?
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
Thermal inversion
layers
51
Noisy or quiet?
Normal conditions
52
Noisy or quiet?
One of a few meteorological effects
Warmer air thermal inversion layer
53
54
55
56
100km
57
Starfish Hill
(or Cape Jervis)
Wind Farm
Starfish Hill, South Australia
58
http://www.auswind.org
Starfish Hill, South Australia
59
http://www.auswind.org
http://www.youtube.com/watch?v=YwcJEqOwKxs
Starfish Hill, South Australia
60
http://www.auswind.org
Starfish Hill, South Australia
61
http://www.auswind.org
Machinery health monitoring
Baseline measurement
Subsequent measurement
In-situ microphones,
strain gauges and
accelerometers on
Rotating machinery
Critical structures
63
Noise, Where does it come from?
64
2007 World Solar Car Challenge
Greenfleet class
Darwin (Sunday)
Katherine
Tennant Creek
Uluru
Alice Springs
Cobber Pedy
Port Augusta
Adelaide (Saturday)
65
Noise – Where is it coming from?
66
67
68
South Port Beach (nr Adelaide)
69