Wind Turbine Noise and Vibration HANDOUT

8/3/2019 Wind Turbine Noise and Vibration HANDOUT

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Wind Turbine Noise and Vibration

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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 =

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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?

Wind Turbine Noise and Vibration HANDOUT

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