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Adapting Aviation to a Changing Climate: Identifying Future Priorities Manchester Metropolitan University, 3rd September 2015
Rory Clarkson
Rolls-Royce, Engine Environmental Protection
The Potential Impact Climate
Change will have ON Jet Engines
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Introduction 2
Cumulonimbus cloud seen
from 38,000 feet
Freezing fog at Heathrow
Freezing cloud
Rain and Hail
Lightning
Sand and Dust
Dusty day at Dubai
Sandstorm in Doha
Birds
Volcanic ash
Corrosive
chemicals X X Turbulence
• Environmental agents that can damage aircraft engines
• How we protect engines from such damage
• How climate change may affect the rate of damage and means of
protection
• What this means for aviation
X
• What we design engines for… but then there is.....
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Real weather
Tropical Lapse Rate
Icing Conditions
• Atmospheric temperature
3
km
C
ISA Lapse Rate
and water
Freezing Fog
Ice Crystal Clouds
Freezing Cloud
Supercooled water droplets
Water increasingly frozen
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Freezing Cloud
Freezing Fog
Icing Conditions
• Freezing Fog & Freezing
Cloud
4
km
C
Supercooled water droplets
ISA Lapse Rate
Duration of exposure
Problems start when ice sheds
Temperature vs Pressure
Altitude
Liquid water content (LWC) vs Mean
Effective Drop Diameter
LWC vs Cloud horizontal
distance
1/1000 severity icing conditions
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Tropical Lapse Rate
Ice Crystal Clouds
Icing Conditions
• Ice crystal icing (ICI)
5
km
C
ISA Lapse Rate
Ice crystal
shapes &
sizes -40°C
-15°C
Freezing level
35000 ft
23000 ft
16000 ft
High concentration of ice crystals
Mostly ice crystals
Mostly supercooled water droplets
All water droplets
Wind
Water increasingly frozen
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Ice Crystal Clouds
Icing Conditions
• Ice crystal icing (ICI)
6
km
C
ISA Lapse Rate
Water Increasingly
Frozen
Engine impact
Again, most problems start when ice sheds
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Tropical Lapse Rate
Ice Crystal Clouds
Icing Conditions
• Ice crystal icing (ICI)
7
km
C
ISA Lapse Rate
Incidents and Flight
Envelope
Water increasingly frozen
Inter-Tropical Convergence Zone (ITCZ)
Aircraft incidents
Flight path
across MCS
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Icing Conditions
• When the ice sheds…
8
Compressor surge
& flame out
Ice crystal damage Core inlet SLW
icing damage Fan track liner
damage
Fan OoB &
LP vibration
Engine surge –
Boeing training
video on YouTube
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Icing Conditions • Engine protection
- Difficult to avoid icing conditions
- So by robust design…
9 Heat accretion sites with hot air
Fan track impact
liner
Red – high LWC, clear line of
sight from fan exit
Blue – low LWC, in shadow of
ESS
Effective water extraction
via handling bleeds
Stronger blades
Clever design
All come at a price: increased cost, weight and fuel burn
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Rain and Hail
Fan breaks up hail, centrifuges
rain – but some rain or hail will
enter core
10
• Threat to engine:
- Damage from large hail
stone impact
- Rain or hail core ingestion leading
to surge or flame out
Engine surge – Boeing
training video on YouTube
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Rain and Hail
• Engine protection
- By engine design to deal with a defined threat – hail stone size and
ice/water concentration
11
Core inlet protection Effective core
water extraction
Severe weather over Taiwan
- The defined threat covers severe encounters,
effectively events that might be encountered
once in 109 flight hours
- Some reliance on avoiding severe weather
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Lightning
• Good understanding of impact lightning can
have on engines and airframe
• Particularly vulnerable parts of the engine are:
- Electronic/electrical systems
- Engine surge following inlet flow distortion
• Defined lightning threat level of 200 kA is derived via a statistical
approach, however maximum measured is ~250 kA
- Difference accounted for by incorporating margin into design
- Plus avoidance of severe weather systems associated with lightning
12
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Mineral Dust and Sand
• Essentially an in-service ‘cost of ownership’ concern
• Qualitatively damage mechanisms are known:
13
Fan and
compressor
erosion
Lubrication system
contamination
Hot section cooling
feature damage
• More fuel efficient engines are tending to increase vulnerability
- Hotter, more complex cooling systems, tighter clearances…
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© 2015 Rolls-Royce plc
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Mineral Dust and Sand
• Global occurrence and concentrations
14
Cairo Airport
• Major new international hubs around e.g. Persian Gulf are
increasing sand and dust exposure
- Operators are less willing to sit sandstorms out
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Turbulence
• Clear air turbulence and
the jet stream
• Severe weather – storms
• Engines designed to cope with severe gust loads
- Although performance can be deteriorated
15
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Summing Up
• There are plenty of atmospheric phenomena that can impair engine
operation
• To prevent excessive economic damage or unsafe scenarios, we rely
on:
- Designing in tolerance, and demonstrating this tolerance at certification
- And that acceptable tolerance levels are based on some level of threat
avoidance and/or very low probability of encountering extreme threat
• Two factors are already presenting challenges to these strategies:
- The push for quieter, cleaner, lower cost and more fuel efficient engines
makes them generally less tolerant
- The economic push to operate in more challenging environments, more
often, i.e.
• Not sitting out severe weather events – i.e. avoid flight cancellations
• More direct routes – fewer diversions
• Large hubs in arid regions – e.g. Persian Gulf
• New markets in e.g. SE Asia, South & Central America – severe weather more
frequent
16
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And Then There’s Climate Change
• Severe weather – icing, rain, hail, turbulence, sandstorms – more
often
- Although severest weather may be only slightly more severe, say 1-2%
• Increasing number of airports becoming dry and dusty for more of the
year – southern states of US, southern Europe, India, China…
• Longer term population centres – human and avian – may move
17
What to Do?
• Restrict operation during severe weather events?
- Commercial and wider socioeconomic pressures?
• Design engines to be more robust?
- At the expense of fuel burn, cost, …?
- Airframe has to follow same approach