wind turbine noise and vibration handout
TRANSCRIPT
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Vibration
Measured in terms of
DisplacementVelocity
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 14Measuring sound and vibrationInstrumentation - vibration
Conditioning amplifier
Spectrum Analyser
Accelerometer Strain gauge
Laser vibrometer
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Measuring sound and vibrationCalibration
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Wind Turbine Noise
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What generates the noise in wind
turbines ?
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Wind Turbine Noise1. Blades2. Rotor
3. Pitch4. Brake5. Low speed shaft6. Gear box7. Generator8. Controller9. Anemometer
13. Yaw drive14. Yaw Motor15. Tower
10. Wind Vane11. Nacelle12. High speed shaft
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Note, much larger gearbox andhence many more moving parts
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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
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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
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Shaft noise unbalancedbent shafts
non-concentric alignment
60)(
RPMHzfrequency =
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Shaft noise
60)(
RPMHzfrequency =
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Shaft noise
Frequency (Hz)
Amplitude
Varies with shaft speed
60)(
RPMHzfrequency =
26
Shaft noise
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Gear Noise
Frequency (Hz)
Amplitude
Vary with speed
60)(
RPMHzfrequencyShaft =
60
.)(RPM
NHzfrequencyMesh = Gear with N teeth
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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 ofthe larger gear
One full revolution of the large gear, also returns
the small gear to the same place
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Gear Noise
Gears that share common multiples alsomesh the same two teeth periodically.
Consider: a 40 tooth pinion anda 60 tooth sprocket,
Turn the sprocket TWO FULL turns, moving120 teeth past a point.
This moves 120 teeth on the pinion, drivingit THREE FULL turns.
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Gear Noise
This cyclic nature is known as the HUNTINGTOOTH.
The frequency is equal to:Gear mesh frequency
Lowest Common Tooth Multiple
This causes uneven wear
Choose tooth numbers that result in a highlowest common multiple to keep this
frequency as low as possible
This is why gears have apparently
strange teeth numbers
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Gear Noise
F1
F2Drive speed
Probable 14 tooth
gear issue
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Gear Noise
http://www.vibanalysis.co.uk/
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Gear NoiseGear Box Failure
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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
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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
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Wind turbines and sound: Review andbest practice guidelines. HGC Engi neering
Acoustic model oftypical wind turbinesound propagation
Examples44
Noisy or quiet?
0dB
10dB
20dB
30dB
40dB
50dB
60dB
70dB
80dB
90dB
100dB110dB
120dB
130dB
140dB
150dB
20
100
1000
100,000
1,000,000
10,000,000
10,000
100,000,000
Pascals
2
2
log10ref
p
pdB =
pref= 20 x10-6 Pascals
refp
plog20=
Hearing threshold
Important to statedistance from source
Pain
350m away
Machinery health monitoring
Baseline measurementSubsequent measurement
In-situ microphones,
strain gauges andaccelerometers on
Rotating machinery
Critical structures
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Many claim that the noise is worse at nightor in the early hours of the morning.
Less masking(other noises
covering it up)
Physiological issues
Meterological effects
Noisy or quiet?
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Noisy or quiet?
Normal conditions
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Warmer air thermal inversion layer
One of a few meteorological effects
Noisy or quiet?