the potential impact climate change will have on jet engines

Trusted to deliver excellence

© 2015 Rolls-Royce plc

The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other

than that for which it is supplied without the express written consent of Rolls-Royce plc.

This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning

such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or

associated companies.

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


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.....


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


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


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



Ice Crystal Clouds

Icing Conditions


6

km

C

ISA Lapse Rate

Water Increasingly

Frozen

Engine impact

Again, most problems start when ice sheds


Tropical Lapse Rate

Ice Crystal Clouds

Icing Conditions


7

km

C

ISA Lapse Rate

Incidents and Flight

Envelope


Inter-Tropical Convergence Zone (ITCZ)

Aircraft incidents

Flight path

across MCS


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





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




Trusted to deliver excellence 10

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


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


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


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…





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


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


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


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

the potential impact climate change will have on jet engines

Documents