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Folie 1 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Applying Aircraft Noise Reduction Technologies at its Source
Progress in Technological Development Volker Gollnick Marco Weiss
Folie 2 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Content
• Motivation & Fundamentals
• Aircraft Noise
• Operational Measurements
• Future Aircraft Configurations
• Conclusion
Folie 3 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Motivation & Fundamentals
Folie 4 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Motivation
• Decoupling of noise impact from traffic growth
• The balanced approach must include - technological advances, - operational advances, - operating restrictions and - better land-use planning around airports
Source: The B
ridge-Noise E
ngineering, 2007 US-
Sou
rce:
AIR
BU
S G
MF,
201
0
50% by 2020
Folie 5 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Fundamentals: Sound pressure level SPL or L
• The reference value is set at the typical threshold of hearing of an average human,
with p0 = 0.00002 Pa or I0 = 10-12 W/m²
• Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave
• The sound pressure level (SPL) or sound level L is a logarithmic measure of the effective sound pressure of a sound relative to a reference value.
2
20 0
10 lg 10 lgp ILp I
= ⋅ = ⋅ [dB]
Halving of acoustic power (sound intensity) corresponds to
a level change of -3dB only
10dB decrease in sound level corresponds approximately to a perceived halving of loudness
but:
„challenging“
Folie 7 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Aircraft Noise
Folie 8 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Aircraft Noise = Airframe Noise + Engine Noise Airframe noise sources
Engine noise sources
Dominating sources:
• Gear
• High lift devices
Dominating sources:
• Fan / Compressor
• Exhaust jet
Empenage
Folie 9 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Aircraft Noise = Airframe Noise + Engine Noise Airframe noise sources
Engine noise sources
Dominating sources:
• Gear
• High lift devices
Dominating sources:
• Fan / Compressor
• Exhaust jet
Fan
Co
mb
ustio
n ch
am
ber
Turb
ine
Jet
Co
mp
ress
or
Engi
ne
Airf
ram
e
Airc
raft
5dB
EPN
dB
Take-off
Fan
Co
mb
ustio
n ch
am
ber
Turb
ine
Jet
Co
mp
ress
or En
gine
Airf
ram
e Airc
raft
5dB
EPN
dB
Approach
• On approach, the airframe makes as much noise as the engine.
• On take-off, the engine noise dominates
Empenage
Folie 10 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Aircraft Noise = Airframe Noise + Engine Noise Airframe noise sources
Engine noise sources
Dominating sources:
• Gear
• High lift devices
Dominating sources:
• Fan / Compressor
• Exhaust jet Airframe Noise
Folie 11 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Airframe Noise
The airframe part with the highest noise level dominates the overall aircraft airframe noise (w/o engine).
In the right diagram (example calculated) the high-lift devices are deflected and causes the highest noise pressure level over the frequency spectra.
30
35
40
45
50
55
60
65
70
75
63 100 160 250 400 630 1000 1600 2500 4000
Frequency [Hz]
Noi
se p
ress
ure
leve
l [dB
]
Wing Slats HTP Gear High-Lift (Fowler) Total Aircraft (Sum)
Folie 12 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Airframe Noise
30
35
40
45
50
55
60
65
70
75
63 100 160 250 400 630 1000 1600 2500 4000
Frequency [Hz]
Noi
se p
ress
ure
leve
l [dB
]
Wing Slats HTP Gear High-Lift (Fowler) Total Aircraft (Sum)
Academic example:
All airframe noise sources, except high-lift devices, are switched off (right picture). Nevertheless the overall airframe noise is not reduced significantly.
Consequence: The noise pressure level of all airframe parts must be reduced equally to reach significant overall airframe noise reductions!
before
after
Folie 13 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Identification of Noise Sources at Aircraft
Transfer of wind tunnel based expertise into real flight situation
Reduction of excess noise from „acoustically detrimental“ details
Examples…
Vortex generators to eliminate hole tones
Sealing of slat track cutouts
Foam filler at flap side edge
Folie 15 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
max. -5 dB through realistic partial fairing
Measures for Aircraft Noise Reductions
Bogie Fairing
Wheel Rim
Fairing Fillet
Hinge Fairing
Enlarged Landing Gear Bay Cover
Brake Fairing
Folie 16 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
-2 dB by fillets in cavities
-5 dB with slat trailing edge modifications
-5 dB by flap side edge modifications
sound intensity ~ p‘2~ v∞5
sound level scales with the fifth power of velocity
3 dB reduction ⇐ 13% decrease in speed
Measures for Aircraft Noise Reductions
Folie 17 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
flow
DLR
with slat-cove-cover landing config.: slat/flap = 26°/35°
Slat-cove-cover
-3 dB far field noise reduction
Measures for Aircraft Noise Reductions
Folie 18 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Aircraft Noise = Airframe Noise + Engine Noise Airframe noise sources
Engine noise sources
Dominating sources:
• Gear
• High lift devices
Dominating sources:
• Fan / Compressor
• Exhaust jet
Engine Noise and Reduction
Folie 19 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Engine Noise and Reduction
past (low bypass) current (high bypass)
„big share“
-40
-30
-20
-10
0
10
20
30
40
50
1960 1970 1980 1990 2000 2010 2020
Stage 2
Stage 3
Stage 4
year of certification
Cum
ulat
ive
noise
leve
l bel
ow S
tage
4 (E
PNdB
)
in accordance toICAO-Regulations
Folie 20 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Engine Noise and Reduction (jet noise)
-1 to -4 dB far field noise reduction
1 2
3
1. Core jet
2. Turbulent mixture zone
3. Fully developed turbulent jet
Forced mixing of low and high speed jet:
ø jet velocity reduced!
A320 (Test vehicle) B787 Gulfstream III
Ljet ~ v8jet
Simple assumption: Jet sound pressure level
scales with the eight power of jet velocity
Halving velocity -25dB
Hushkit
Folie 21 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Engine Noise and Reduction (fan/compressor noise)
-1 to -4 dB far field noise reduction
Active Noise Control for Aero Engines
Passive Noise Control for Aero Engines (Liner) Pressure fluctuations (sound waves)
Perforated wall
Air flow
Dissipative compression/ expansion
Resonance volume
eliminating specific tones
Folie 22 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Operational Measurements
Folie 23 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Reducing noise on the ground by around 1-5 dB per flight
Operational measures for noise reduction
Area of max. noise benefit
© E
uroc
ontr
ol
Continuous Descent Approach
Areas of noise intrusion reduction
Folie 24 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Reducing noise on the ground by around 1-5 dB per flight
© E
uroc
ontr
ol (a
dapt
ed)
Continuous Descent Approach
Increasing the glide slope angle provides further potential of noise reduction
Area of max. noise benefit
Operational measures for noise reduction
Folie 25 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Operational measurements of noise reduction
Level of noise reduction depends on CDA-profile
© D
LR A
S
Folie 26 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Relocating approach in less noise sensitive areas
© D
LR-A
S
Unconventional Approaches
Operational measures for noise reduction
Folie 27 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Other commonly applied noise management measures include:
• avoiding fly-over sensitive sites such as hospitals, schools, hometowns
• using continuous descent approaches and noise abatement departures
• avoiding use of auxiliary power units by aircraft on-stand
• towing aircraft or electrically driven landing gear instead of using jet engines to taxi
• limiting the number of operations or the extent of a critical noise contour
Operational measures for noise reduction
Folie 28 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Future Aircraft Configurations
© Airbus
Folie 29 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Future Aircraft Configurations examples
© D
LR-A
S ©
DLR
-AS
© C
ambr
idge
MIT
Inst
itute
Folie 30 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Future Aircraft Configurations (example)
-60 -42 -24 -6 12 310
18
36
54
72
91
x [m]
y [m
]
Quelle
Ejector principle to control jet noise
Wing shielding to reduce forward
emitted noise
Long intakes with liners to supress fan noise
Folie 31 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Design advantage: Noticeable noise reduction (engine)
Future Aircraft Configurations (example)
90 80 70 60 50 40 30 20 10
0
Time [s]
PN
LT [P
NdB
]
0 50 100 150
Approach = -8,7 EPNdB
Approach Conventional S/R Aircaft (Today)
Folie 32 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Design disadvantage: Deteriorated fuel efficiency
Future Aircraft Configurations (example)
90 80 70 60 50 40 30 20 10
0
Time [s]
PN
LT [P
NdB
]
0 50 100 150
Take-off = -6,6 EPNdB
Departure Conventional S/R Aircaft (Today)
Folie 33 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Conclusion
Folie 34 V. Gollnick, M. Weiss > Deutsches Zentrum für Luft- und Raumfahrt
Conclusion
• Noise impacts increase with growing air traffic
• Balanced approach: Decoupling of Noise impact from air traffic growth
• Technical and operational improvements for noise reductions have to be introduced equally to attain the highest potential of noise reduction
• The change in current aircraft design philosophies promises a high potential in future noise reductions