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Lean Burn Technology at Rolls-Royce

Kenneth Young – Chief of R&T – Combustion Sub-System

June 2014

FORUM – AE – Technology Workshop

Rolls Royce Lean Burn Technology

For an optimised solution, lean-burn is developed as a system within other engine systems:

Control system

Control laws

Turbines

Heat management system

Installation

As with the rest of industry, certification values of NOx are reducing continuously.

Rich Burn (phase 5 technology) is a robust, proven technology but is fundamentally limited in the level of NOx and smoke achievable.

Lean premixing of fuel and air is needed for a step change in high power NOx and smoke performance.

Fuel staging is used for operability:

Rich pilot for low power stability

Lean main zone for minimised NOx and smoke

Corporate and Regional

Short Term MediumTerm Long Term

Phase 5 Rich Burn

Lean Burn, Staged combustion

Combustor Technology Implementation Options

Phase 5 Rich Burn with incremental improvements

Current rich burn combustor technology can deliver NOx in the range of 55-70% CAEP6

Combustion design influenced more strongly by complexity & weight than emissions.

Phase 5 Rich Burn

Lean Burn with incremental improvements

Lean Burn, Staged Combustion

Large Engine

Middle of the Market

Phase 5 Rich Burn with incremental improvements

Current rich burn combustor technology can deliver NOx in the range of 55-65% CAEP6

Combustion choice influenced by complexity, weight and emissions requirements. Future engine architecture will play a large role.

Lean Burn, staged combustion

Current combustor technology can deliver NOx in the range of 60-80% CAEP6

Combustion architecture choice dominated by emissions requirements

Engine cycle

Phase 5 Rich Burn

RR Lean Burn Development – A long term partnership 4

• ATAP10 • EFE • Samulet • SILOET 1 & 2

UK Government

• EEFAE (ANTLE, POA) • FW7: Tecc, First, Impact,

Lopocotep, Intellect, Lemcotep

• Clean Skies, SAGE 6 (ALECSYS)

European Commission

German Government

• Luftfahrtforschungs-programme Lufo IV, V

• AG Turbo 2020

Rolls Royce Lean Burn Combustion System Architecture

Compact nested pilot staged lean burn fuel injector

Mounting in line with large engine practice

3rd generation cooling technology for ultra efficient cooling

Movement tolerant FSN design

Conventional ignition system

High efficiency dump diffuser

Optimised combustor volume

Image Removed from Public Disclosure

Rolls Royce Lean Burn Fuel Spray Nozzle Tip Architecture

Staged fuelling with two flow circuits (pilot and main)

Both pilot and main based on well established airblast technologies

Smooth operation, enhanced mixing comparable with longer premixed ducts. Arrangement flashback and auto-ignition free

Novel heat management of mains fuel by pilot fuel flow

Currently uses state of the art conventional manufacture. Design is Additive manufacture capable.

Servicability is a key design feature

Technology scalable, proven on E3E and EFE test vehicles

Fuel delivery system is heatshielded for improved thermal management

Image Removed from Public Disclosure

Airblast Atomiser Technology Focus

Both pilot and mains utilise airblast atomisation of a thin annular film of fuel by co-linear airstreams

• Used in entire RR aerospace product range

• Maintenance of a high relative velocity between liquid film and atomising airstream key performance parameter

Airblast atomisation performance not greatly affected by injector flow number

• Atomisation dominated by air stream - insensitivity arises due to high atomising air velocities utilised by airblast atomiser

• No change across engine operating range in relative positions between fuel and air streams

• No reliance on discrete jet ‘cross flow’ atomisation/jet trajectory/mixing mechanism

• Low sensitivity to fuel / air momentum ratio

• Flow number insensitivity facilitates 2 fuel circuit design and robust scaling.

Air Liquid Ratio

Dro

ple

t Sau

ter

Mea

n d

iam

eter

Rolls-Royce injector operation range (Rig and Engine)

Typ

ical

alt

itu

de

win

dm

illin

g ra

nge

FN = Flow number

(a measure of fuel

flow rate for given

fuel pressure drop)

Airblast Atomiser Technology Focus

Substantial development has been conducted on the detailed tip and atomiser technology

Primary focus has been on:

Ignition performance

Aerodynamic stability

High power mixing

Impact on combustion performance and operability.

Thermo-acoustics

Development of fuel galleries for optimised thermal management performance and fuel draining.

Design for production manufacture.

Pilot stream - no air

Pilot stream – with air

Mains stream – no air

Mains stream – with air

Single Injector Test in a 20bar optical rig in lean burn mode at DLR Koln

Design Considerations for Aero Combustion Systems

Low NOx

Operability

Safety and Reliability

Pressure loss

Weight

System Integration

and Interaction

Combustion efficiency

Power Modulation

Life

ANTLE POA test Configuration

– Water fed directly into core engine

– Water loading scaled to match Trent 500 cert test

– Trent 500 bleed schedule overwritten (HP compressor bleed forced closed)

• Engines must be fully responsive to sudden changes in water content in transient manoeuvres

• Testing involves steady state, transient manoeuvres (slam decels) and sudden changes in water

• This is one of the most severe tests of the combustion system.

System Level Issues Combustor Stability in Inclement Weather – Water / Hail Ingestion

Transient Response to Water / Hail Ingestion

Engine idling before sudden increase in water

Accompanying dip in TGT triggers recovery logic

Engine recovers and is maneuvered.

Water is removed and engine returns to normal operation

0

100

200

300

400

500

600

700

800

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1000

1100

12

:38

:53

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:02

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Time

WA

TE

R F

LO

W (

GP

H),

FU

EL

FL

OW

(GP

H),

T3

0

& T

GT

(K

), P

30

(p

si)

0

10

20

30

40

50

60

70

80

90

100

110

N3

%

WATERFLOWGPH

T30K

TGTK

P30psi

PILOTfuelflowGPHMAINSfuelflowGPHN3%

TGT

Speed

T30

Water

25

Wind - milling

starting

Wind - milling starting

Certification requirement to restart the engine in - flight within a set time after a commanded or un - commanded in - flight shut - down

Starter

assist

starting

Starter assist starting

Certification requirement to restart the engine in - flight with starter assistance within a set time after a commanded or un - commanded in - flight shut - down

Quick relight

Certification requirement to immediately relight the engine in - flight while spooling down after a flame out. This can be caused e.g. by pilot error or compressor surge

20s - 30s

from idle

Quick

Relight

1s - 5s

in climb

0

10000

20000

30000

100 200 300 400

Indicated Airspeed (knots)

Alt

itu

de

(ft

)

System Level Issues Altitude restart

• Engines must demonstrate restart capability across a range of forward speeds and altitudes.

• Testing is conducted in an altitude cell to get the correct boundary conditions of pressure and inlet temperature

• Two series of core tests have been undertaken in the E3E programme.

• Tests differed in configuration of fuel spray nozzle and controls architecture.

• Conditions across the full envelope were successfully achieved.

Results from the E3E Core Test Programme

Full windmill relight loops achieved across the required forward speed envelope beyond 30,000ft altitude

Test results exceeded certification and customer requirements

Quick windmill relight loops also demonstrated without adverse affect on turbo-machinery

Cold day starting achieved down to below -40C.

0

5000

10000

15000

20000

25000

30000

35000

40000

160 180 200 220 240 260 280 300 320 340 360 380 400 420 440

VCAS (kts)

Alt

idu

de [

ft]

Core 3/2b test limit

Successful start within 90sec

Successful start, time-to-idle > 90sec

No ignition or pull-away

Windmill ignition envelope of E3E

• Emissions are strongly affected by inlet pressure and temperature.

• The EFE high temperature demonstrator is designed to operate at extreme conditions allowing emissions to be fully validated across the full range of future engine cycles.

• Testing shows NOx levels in the region of 35 to 45% CAEP6 (dependent on cycle) – 30-35% reduction to rich burn.

• In lean burn mode, the smoke emissions are virtually zero and in some cases, measured values are lower than ambient.

System Level Issues Emissions

nVPM measured in mains operation – lean burning mode

Next Steps

• All sub system and component technologies are now at a high level of readiness.

• Given the number of systems affected, there are many opportunities for undesirable emergent behaviour.

• As part of the CleanSky SAGE6 programme, RR are preparing for full system integration and validation on 2 retrofitted Trent 1000 engines:

• Icing testing – Manitoba

• External noise testing – NASA Stennis

• Flight testing – company 747 flying test bed

15