Combustor Fundamentals and Key Issues in Future · PDF fileThomas Doerr – Teamleader Combustion Aero-Thermal RRD Combustor Fundamentals and Key Issues in Future Combustor Technology

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June 2014 – Paris

FORUM-AE – Combustor Technology Workshop

Thomas Doerr – Teamleader Combustion Aero-Thermal RRD

Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective

Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop

Emissions:

NOx Smoke / PMs CO UHC

Temperature Profile

Weak Extinction Stability

Pressure Loss

Efficiency

Weight Length Cost

Cold Start Comb. Instabilities

Altitude Relight

Cooling /

Durability

Aero-Engine Combustor Requirements

Rolls-Royce proprietary data

Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Low Emission Combustion Technologies –

Operating range for low emissions

NOx reduction principles:

reduce residence time within stoichiometric

condition

initiate combustion under lean conditions


Conventional Combustion Chamber optimised for low NOx and smoke

Primary

Zone

Dilution

Zone

Air

Fuel

R Q L

Secondary

Zone

Typical Cycle

Data at T/O:

P30 ~ 30 bar

T30 ~ 850 K

AFR ~ 40

Combustor – Stoichiometry Control

RQL – Rich burn – Quick quench – Lean burn


Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Fuel Burn & CO2 Mitigation Technology Workshop


Primary

Zone

Secondary

Zone

Quenching

Dilution

Zone

Combustor

Exit

NOx – Smoke trade-off

Combustor – Stoichiometry Control

RQL – Rich burn – Quick quench – Lean burn


Rich Burn Combustion – RQL – Improvements Fuel Spray Nozzle (FSN) Development

Improvement of primary atomisation of current film layer design for low smoke production without compromising current levels of weak extinction margin and operability

Optimisation of FSN aerodynamics to improve droplet transport and mixing

Low Smoke Primary Zone

Optimisation of primary zone flows to control stoichiometry

Mixing Zone

Optimisation of combustor jet mixing zone for low residence time within stoichiometric operation

Low power operation and smoke consumption not to be compromised

Combustor Cooling – Liner Architecture

High efficient cooling schemes to free combustor air for quenching

Double wall / tiled combustor architectures

New manufacturing technologies (e.g. additive laser manufacturing) enabling complex cooling arrangements at acceptable cost levels

Introduction of ceramic structures for ultimate cooling flow reduction



Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Technology Readiness Staircase – Rich Burn Improvement


Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Low Emission Combustion Technologies –

Operating range for low emissions

NOx reduction principles:

reduce residence time within stoichiometric

condition

initiate combustion under lean conditions



NOx Cooling

1400

1600

1800

2000

2200

2400

2600

2800

0 10 20 30 40 50 60

Air-to-Fuel-Ratio at T/O

T40

Moderate Cycle

Requirements

Nozzle Primary Zone Secondary Zone Dilution Conventional RQL Combustion

Advanced Cycle

Requirements

Nozzle Lean Burn Combustion

Lean Burn Requirement

Cycle

Principles of Lean Burn Combustion


Take-off Idle Weak Extinction

Combustor 35 - 40 70 - 90 200 - 300

Turn-Down-Ratio 1 : 2 - 3 <6

Fuel Injector, conventional

~4 ~10 ~25

Fuel Injector, premixing

~25

Weak Extinction of the lean injector

50 150-200

Air – Fuel – Ratios within Combustor – Comparison

Lean Burn Combustion – Fuel Staging




Fuel & Controls System

pilot/main staging

circumferential main staging may be needed

Stability control

Lean burn injector

dominates combustion performance

partially premixing, up to 70% air flow through fuel injector

internally staged with nested pilot injector

separated pilot and main stage combustion

Combustor

cooling optimised to enable lean operation and life targets

no mixing ports

Pilot flame

Main flame

Lean Burn Combustion –

RR Lean Burn Technology (ANTLE, E3E)



Air

60 - 70%

AirStoich 40% 40 - 30%

Lean Burn injector performance dominating combustor characteristic

Premixing with up to 70% of combustor air mass flow within lean burn injector

RR – Lean Burn Combustion Technology

AirCool

R Q L

Main flame

Pilot flame 10% +20% AirStoich

AirCool

Conventional (RQL) vs Lean Burn Combustor

+30%



N Ox D istribu tion w ith in LTO C ycle

0%

10%

20%

30%

40%

50%

60%

70%

R Q L Lean B urn

%C

AE

P2

7%

30%

85%

100 %

impr. mixing, red. cooling

High power NOx

Lean Burn Combustion – Impact of pilot stage on total emissions

For low emission lean burn systems the rich pilot zone cause

significant amounts of NOx at low power operating conditions

Further NOx reduction of lean burn systems need to include NOx

reduction measures of piloting devices



BOSS/ HBK1 HPSS/ HBK3

New Big Optical Single Sector High Pressure Single Sector

Emissions up to 40 bars Emissions up to 20 bars

Non-intrusive measurements, e.g.

PDA droplet characterisation

Chemiluminescence volumetric OH*-concentration

LIF OH- / fuel concentration

Mie-scattering fuel droplet

PIV 2D velocity field

Method Variables

‚Working horse‘ for lean burn injector development


concentration

Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Lean Burn Injector – Staged Operation at Elevated Pressures

Internally staged lean burn fuel injector kit of

parts with

pressure atomiser

prefilmer and

discrete jet injection 6bar, 700K, Variation Pilot-Main Fuel Split

100% Pilot

Only

50%

10% 0% Main Only

20%30%

100% Pilot

Only

50%

10% 0% Main Only

20%30%



Take-off emissions in single sector combustor (35 bars, 850K)

Lowest NOx at lowest pilot fuel split

Aerodynamic separation of pilot and main combustion zones

Main fuel preparation critical for low emissions at take-off

Laser diagnostics in optical high pressure sector at DLR (20 bars, 850K)

Flame & flow field visualisation

Heat release (OH* chemiluminesence)

Investigation of fuel preparation, pilot and main interaction, correlation to CFD

Module AFR

V1C7, V1C10, V2C1, V3D3C22: 31bar, 820K

0

5

10

15

20

25

30

35

20 25 30 35 40 45

Module AFR

EIN

Ox

V1C7, 10:90

V1C7, 30:70

V1C10, 10:90

V1C10, 30:70

V2C1, 10:90

V2C1, 30:70

V3D3C22, 5:95

V3D3C22, 20:80

C-B low pilot

C-B high pilot

C-E low pilot

C-E high pilot

C-F low pilot

C-F high pilot

C-G low pilot

C-G high pilot

Lean Burn Injector Performance at Take-Off Condition



Very strong influence of fuel split on NOx and efficiency

Below 40% main flame is burning lean in a lifted mode (separated from pilot)

Above 40% pilot/ main flames are merged, dominated by pilot

Optimal fuel split at this condition for low NOx and high efficiency: 30-45%

Lean Burn Injector Performance at Cruise Condition


Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Principle Design Trades of Lean Burn Technology

Pilot / Main Interaction

separated combustion zones to control NOx and smoke emissions at mid and high power

interacting/communicating combustion zones at low and mid power to control efficiency and CO/UHC emissions

Burner to burner / burner to liner interaction ignition capability, altitude relight on pilot only mode pilot zone (reaction) volume for efficiency and pull-away light-around and efficiency

Operability

weak extinction stability and efficiency through entire operating range and fuel staging scenarios (entire flight mission)

steady state and transient with sufficient margin to cope for inclement weather conditions




Combustion Efficiency

especially cruise efficiency and mission fuel burn optimisation of fuel staging strategy strongly influenced by scaling and engine cycle conditions optimisation of combustor geometry and cooling

Thermoacoustics

susceptibility of fuel preparation/injection to unsteady heat release

trade with emission performance optimising fuel staging strategy strongly influenced by scaling and engine cycle conditions

Thermal Management

degradation of stagnant fuel at part power conditions for fuel circuits being not operative

heat shielding and active cooling of stagnant fuel especially in the vicinity of discharge orifice



System Integration

Combustor mechanical integrity – wall cooling to achieve combustor life

Fuel and controls system for fuel staged system; fail safe scenarios

Cost, Weight, Complexity of combustor module and fuel system

.....

Lean Burn is a revolutionary step in combustion technology

development (no evolution from advanced state-of-the-art technology)

Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris – FORUM-AE - Combustor Technology Workshop Combustor Technology Implementation Strategy




Key Enablers Fuel Spray Nozzles

- Atomisation and fuel placement

- Low smoke production

- Thermal management

Combustion / Mixing

- Premixing

- Smoke consumption and NOx control

- Combustor turbine interaction CTI

- Combustion Modelling - Two Phase Flows; Primary/Secondary fuel break -up - Chemistry, Turbulence - Emissions Focus Soot and CO/UHC

Liner Architecture / Durability

- High efficient wall cooling

- Alternative designs, material and manufacturing (e.g. DLD, CMC)

- Costs


23


Rolls-Royce Advance and UltraFan Engine Architectures


Questions ?


Combustor Fundamentals and Key Issues in Future Combustor Technology – The Rolls-Royce Perspective June 2014 – Paris FORUM-AE - Combustor Technology Workshop

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Combustor Fundamentals and Key Issues in Future · PDF fileThomas Doerr – Teamleader Combustion Aero-Thermal RRD Combustor Fundamentals and Key Issues in Future Combustor Technology