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© 2012 Rolls-Royce Deutschland Ltd & Co KG
The information in this document is the property of Rolls-Royce Deutschland Ltd & Co KG 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 Deutschland Ltd &
Co KG.
This information is given in good faith based upon the latest information available to Rolls-Royce Deutschland Ltd & Co KG, 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 Deutschland Ltd & Co KG or any of its subsidiary or associated companies.
©2012 Rolls-Royce Group
The information in this document is the property of Rolls-Royce Group 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 Group.
This information is given in good faith based upon the latest information available to Rolls-Royce Group, 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 Group or any
of its subsidiary or associated companies.
Tuesday, 20 December 2018, Sydney
Gas turbine Combustion
Modelling
Lean combustion and fuels
Dr. Ir. Ruud Eggels
and contributions of Dr. Thomas Doerr
Rolls-Royce Deutschland Ltd & co KG
Eschenweg 11
Dahlewitz-Berlin
15827 Blankenfelde-Mahlow
Germany
Objectives of this presentation
Overview of Lecture:
Gas turbine combustors performance
Emissions of aero gas turbines
CFD in aero combustion design
Alternative fuels in aero-space
Rolls-Royce proprietary information - private
1-3 3
Combustion Chamber
Aero-engine Architecture – RR Trent
Rolls-Royce proprietary data
HC,is HC
HT,is
HT
30
40
heat release q = cP(TT,40–TT,30)/hcomb
‚The Job‘
C12.5H24 + 18.5 O2 + 69.6 N2 12.5 CO2 + 12 H2O + 69.6 N2
1 kg fuel is burnt to 3.16 kg CO2 and 1.29 kg H20
‚The Challenge‘
Fundamental problem:
Average turbomachinery through flow > 150 m/sec
Burning velocity of kerosene in air ~ 5 to 9 m/sec
Required range of AFRs 35 ~ 150
Stable burning AFR range 4 ~ 30
Air-to-Fuel-Ratio:
Equivalence Ratio:
fuel
air
m
mAFR
30,
AFR
AFR tricstoichiome
Aero-engine Emissions –
Typical sub-sonic cruise emissions
Fuel C12.5H24 +S
Air
N2 + O2
Engine mass flow
percentage
(Jet A-1)
N2
75.2%
O2 16.3%
CO2
72%
H2O
27.6%
Combustion
products
8.5%
SOx
~ 0.02%
NOx
84%
CO 11.8%
UHC
4% Soot 0.1%
Pollutants
0.4 %
1-7
Efficiency corrected to different AFRs
99,0
99,1
99,2
99,3
99,4
99,5
99,6
99,7
99,8
99,9
100,0
0,00 0,01 0,02 0,03 0,04 0,05 0,06Loading theta [-]
Co
mb
. e
ffic
ien
cy [
-]
AFR 30
AFR 40
AFR 50
AFR 75
AFR100
Combustion Efficiency –
Combustor Loading Parameter for annular combustors
correlation for BR700 combustor
)(),(),(
10)(
3030
530
300/308.130
KTpsipfeetV
w
Vepimp
CC
CCKT
We control this !!!
AFR
operating line idle
take-off
Loading Theta
1-8
Stability Limits –
Ignition and Extinction
Combustor Operability Limits –
Influence of pressure
on stability/extinction on ignition
Ignition loops
Wc
8 psi 6 psi 4 psi
massflow
CAEP/2 superseding CAEP/1 on 1st Jan 1996
CAEP/4 superseding CAEP/2 on 1st Jan 2004
with ~16% reduction for NOx at OPR=30
CAEP/6 superseding CAEP/4 on 1st Jan 2008
with ~12% reduction for NOx at OPR=30
CAEP/8 superseding CAEP/6 on 1st Jan 2014
with ~15% reduction for NOx at OPR=30
CAEP/10 will follow on 1st Jan 2020
Non-Volatile Particulate Matter (nvPM ) will be regulated (mass
and numbers)
Emissions Legislation –
NOx Stringency
UHCCOx
NOj
Fji
EIi
time
ii
flowfuelFjP
D
,,
/))(4
1
(/)(
Emissions Legislation –
ICAO Landing-Take-Off (LTO)- Cycle
e.g. for
one engine tested f (NOx) = 0.8627
two engines tested f (NOx) = 0.9094
UHCCONOj
jfFjDFjD
x
measPcharP
,,
)(//)(/)(
Emissions Legislation –
Determination of Emissions Margins vs Legislation
UHCCONOj
FjEItimeflowfuelFjD
x
ii
i
iP
,,
/))((/)(4
1
Calculate characteristic value from measured value for Dp/Foo (factor
for engine scatter)
The characteristic value is then compared to the legislative limits for
emissions, which is depending on engine pressure ratio (OPR) and
rated thrust (Foo)
4-13
Emissions Legislation –
ICAO Emissions Data Sheet
Emissions Legislation –
DpNOx/Foo of aero-engines in comparison to legislation
ICAO Emission Limits for engines above FN 20000 lbf ( 89 kN)
CAEP/2
CAEP/4
CAEP/6
CAEP/8
0
20
40
60
80
100
120
10 15 20 25 30 35 40 45 50
Overall Pressure Ratio
ICA
O L
TO
Dp
NO
x/F
oo
[g
/kN
]
RR
RRD
RRC
Pratt & Whitney Aircraft Group
International Aero Engines
General Electric
CFM International
ACARE target 2020: 40% CAEP/2
Low Emissions Requirements –
Further Drivers
Local landing charges at some European airports
(additional charges for emissions), others may follow
ACARE targets for CO2 and NOx
Flexibility for Future fuels
synthetic fuels, ‚bio‘-fuels; current and new combustor
technologies must be capable burning future fuels while
maintaining operability and emission levels
Low Emissions Requirements –
ACARE targets for CO2 and NOx for Aviation Emissions In January 2001 EU‘s ‚Advisory Council for Aeronautics Research
in Europe‘ set emission reduction targets for 2020 with
CO2 reduction of 50% and
NOx reduction of 80%
The reduction targets comprise aircraft, engine and air traffic
management improvements.
Flightpath 2050 environmental goals
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.700
0.725
0.975
1.000
0.950
0.925
0.900
0.875
0.825
0.850
0.800
0.775
0.750
0.4
0.425
0.450
0.475
0.500
0.525
0.550
0.575
0.600
0.625
Current High
Bypass ratio
Engines
Approaching
Theoretical
Limit, of
Propulsive
Efficiency
Approaching
Theoretical Limit of
thermal efficiency
Theoretical SFC Improvements S
pe
cific
Fue
l C
on
su
mption lb
/hr
/ lb
f @
0.8
Mn
Propulsive
Efficiency
Thermal
“Cycle”
Efficiency
Higher Pressures
Temperatures, Efficiencies
Novel Core Systems
Higher bypass ratios
Novel LP Systems
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 19
Technology Readiness Staircase – Rich Burn Improvement 20
UTC Loughborough
Combustor CFD Modelling of aero combustors
Requirements:
Short turn around times, easy to use
Support understanding of flow and combustion processes
prediction of combustor exit temperature and velocity profiles
prediction combustor wall temperatures and heat transfer
prediction of NOx, CO, UHC and soot emissions
prediction of combustion efficiency
optimisation process of combustor and fuel injector configurations
CFD in aero combustor design
Challenges:
• Complex geometries
• Complex physics
• Flow field (high swirl, recirculation, jet mixing)
• Liquid fuel spray (2-phase flow, atomisation)
• Combustion (diffusion flames, premixed)
• Large range of length scales:
- Size of effusion cooling holes < 1mm, combustor > 0.3m
- thermal boundary layer < 0.1 mm
• Large range of time scales:
- Time-scales of heat transfer is in order of 1-10 s
- Typical flow through time scale 1ms
- Typical turbulent time scale: 1μs
Not all details can be resolved
Rolls-Royce Combustion CFD code
In-house CFD code PRECISE-UNS
Both Incompressible & compressible
unstructured meshes
RANS/URANS: k-epsilon turbulence models, RSM
LES & RANS capability in same code
Different 2nd order discretisation schemes
Different solvers Hypre multi-grid solvers, AGMG …
Langrangian spray model
Combustion models:
Global chemistry, flamelets, FGM, detailed chemistry
Combustion chemistry interaction modelling
EBU, Presumed PDF, stochastic field PDF
Parallelised using MPI
Heat release modelling
When applying Flamelet Generated Manifolds
Heat release loss options:
a) Using a FGM table for one enthalpy, correct temperature by:
T = TFGM + (H - HFGM) / Cp
b) FGM table for a range of enthalpies:
Different unburned mixture temperature
By using burning stabilised flames
In gas turbines
• The heat loss is limited: no nett heat release through walls
• The air temperature is in the range of 800-1000 K
For most application option (a) is sufficient
2
4
Modelling of combustion
Flamelet Generated Manifolds & Heat Loss
• Within the NGV, both the enthalpy and pressure are not constant
• An additional control variable for the pressure would make the look-
up table too large
• Therefore, isotropic expansion in the NGV is assumed:
Texit / Tref = ( P / Pref ) (γ-1/γ) ), with γ the heat capacity ratio
• An iterative process is required to compute burned mixture
temperature:
The mixture composition depends on the temperature, and the
equilibrium temperature depends on the mixture composition
2
5
Temperature Combustor and high pressure turbine
Overview
Combustor design
Emissions
CFD approach
Validation of CFD
Application to aero-engine gas turbines
Conventional combustion systems
Lean combustion systems
The way forward
Validation of combustion CFD
Validation against small scale well known test cases, for which detailed validation data is available
Sandia Flame D
Generic test cases, more realistic for gas turbine combustion, some experimental data available
Generic combustor
Full combustion system
Application to real gas turbine combustors, limited validation data available
Rich burn combustors
Lean burn combustors
Validation of combustion CFD
Validation against small scale well known test cases, for which detailed validation data is available
Sandia Flame D
Generic test cases, more realistic for gas turbine combustion, some experimental data available
Generic combustor
Full combustion system
Application to real gas turbine combustors, very limited validation data available
Rich burn combustors
Lean burn combustors
Validation data: Sandia Flame D
11/10/11
Flame D LES Results
Experiment Mean Temperature Instantaneous temperature
11/10/11
Flame D LES Results
Velocities
Temperature
Validation of combustion CFD
Validation against small scale well known test cases, for which detailed validation data is available
Sandia Flame D
Generic test cases, more realistic for gas turbine combustion, some experimental data available
Generic combustor
Full combustion system
Application to real gas turbine combustors, very limited validation data available
Rich burn combustors
Lean burn combustors
-30
-20
-10
0
10
20
30
40
50
60
-30 -20 -10 0 10 20 30
r
Axia
l V
elo
city
Uax (10mm) exp. LDA
Uax (10mm) RANS
Uax (10mm) LES ext.
-20
-10
0
10
20
30
40
50
60
70
-0.025 -0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025
r [m]
Axia
l V
elo
city [
m/s
]
Uax-Exp 1mm
Uax-RANS 1mm
Uax LES refined (1mm)
Generic combustor: Burner exit
10 mm above burner
Model includes swirlers
Pressure field
• Improved turbulence modelling and
unsteady phenomena
• Velocity better captured by LES
• Vortex core structure resolved.
Generic combustor
600
800
1000
1200
1400
1600
1800
2000
2200
-30 -25 -20 -15 -10 -5 0 5Radius
Tem
pera
ture
Temp FGM 10mm
Temp FGM 14 mm
Temp FGM 18 mm
Temp FGM 22mm
TEMP FGM 26mm
T [K] exp. 10mm
T [K] exp. 14mm
T [K] exp. 18mm
T [K] exp. 22mm
T [K] exp. 26mm
Computed
temperature
Internal data available for generic combustor
• which has typical features of aero engine combustor
• representative operating conditions
Quite good agreement between CFD & Experiments
Validation of combustion CFD
Validation against small scale well known test cases, for which detailed validation data is available
Sandia Flame D
Generic test cases, more realistic for gas turbine combustion, some experimental data available
Generic combustor
Full combustion system (cold flow)
Application to real gas turbine combustors, very limited validation data available
Rich burn combustors
Lean burn combustors
36
KIAI-ITR4-KIT- 22-23/09/2011
Modelling isothermal aero dynamics
36
Realistic aero engine geometry
Including pre-diffusor, annuli and full fuel injector
Challenge
Modelling aero dynamics of pre-diffusor and dump gap
Experimental velocity data available (measured at LU)
37
KIAI-ITR4-KIT- 22-23/09/2011
Applied grid
Hexa dominant
Grid (12.5 M cells)
38
KIAI-ITR4-KIT- 22-23/09/2011
Boundary conditions
Axial and tangential velocity at OGV inlet: applied
measured profiles
Axial velocity Swirl velocity Measured axial velocity
39
KIAI-ITR4-KIT- 22-23/09/2011
Velocities
RANS
results
Velocity results
KIAI-ITR4-KIT- 22-23/09/2011
40
URANS, time avaraged
Small changes between RANS and URANS. LES shows
different angle of outer swirler flow
LES, time averaged
41
KIAI-ITR4-KIT- 22-23/09/2011
Results at OGV exit
Steady RANS, LES and measurements
Large scale effects captured, but considerable local
differences
CFD results combustion system modelling
42
KIAI-ITR4-KIT- 22-23/09/2011
CFD results combustion system modelling
OGV exit: turbulent kinetic energy
CFD (RANS) Measured
KIAI-ITR4-KIT- 22-23/09/2011
Results at diffuser exit
Measured
Total velocity
CFD
Mean velocity structure captured, however:
• refined grids required
• results strongly dependent on pre-diffusor inlet boundary condition, which is
inherent unsteady (compressor aerodynamics)
Full combustor system modelling
Velocity field Temperature field
As many details of the
geometry is taken into
account, while these may
have an impact on the
results
Full combustion system traverse
Predicted combustor exit temperature within measured uncertainty
Prediction of NOx and CO emissions
NOx and CO trends can be predicted reasonably well
NOx predictions against rig data
Rolls-Royce proprietary information - private
• Very good prediction of NOx trend.
• However, absolute value is off by a factor of 3.
• CFD (LES) results compared with LII soot
measurement data from EDS rig DLR Cologne
using aero engine injector.
• 130k time steps
• FGM combustion model
• Modified IC (Lindstedt) two-equation soot model
• Good quantitative agreement of predicted soot
with measured data within primary zone
• However measurements
are performed with
aromatic free fuel
• Oxidation too slow
4
8
LII (DLR)
Precise-UNS
Soot modelling / EDS Rig DLR Cologne
CTI- Simulations with PRECISE-UNS
Large Eddy Simulation BR710 full annular combustor with NGV
Light-around modelling: temperature and spray evolution after ignition
4
9
Aero Engine Combustor modelling
Combusting CFD application
Rich Quench Lean combustor
Combustor only
Including annuli / part of fuel injector
Full combustor system
Using CFD for combustor development;
optimisation
Lean combustors
Rolls-Royce proprietary information - private
Combustor design
More refined combustor design using CFD
Maxim Gessel, UBWM, IMPACT-AE
Combustor port optimisation example
Objective: to improve NOx and soot emissions
By moving and resizing dilution ports
20-50 different configurations have been considered
Rolls-Royce proprietary information - private
Combustor port optimisation example
EINOX ~ - 21%
SOOT ~ - 75 %
Torsten Voigt
54 CAD Combustor Development
DLD
CFD optimisation
Full combustor system model
Grids generated using ICEM-CFD and BoXer
RANS, FGM combustion model, NOx and soot
emissions
Parameters modified in the design optimisation
Position of dilution holes
Number of dilution holes
Angle of dilution holes
Optimisation objectives
NOx emissions, ICAO cycle
Soot emissions, ICAO cycle
Temperature traverse, to meet turbines requirement
55
Optimization example, for single row combustor
Variation of the number of mixing holes per row (2 to 5)
Single row combustor
Equally distributed mixing holes on both liner sides
Central port on fuel spray nozzle axis
56
Optimization example
NOx emission results for ICAO cycle:
Significant decrease of EINOx for ICAO100 and ICAO85 with increasing number
of dilution holes
However soot is increasing significantly: additional changes are required to
reduce soot, e.g. fuel injector
With increasing number of dilution holes, distance between holes becomes
smaller leading to mechanical issues
57
Results of CFD optimisation
Results of CFD optimisation:
- Manual driven process
Most interesting
Optimized
geometries
Baseline
configuration
58
Optimised combustor
Reduction in peak temperatures, therefore reduced NOx formation
59
Validation agains Full annular rig testing
Rolls-Royce proprietary information - private
• Combustor has been
optimised in relative small
steps using CFD (only)
• Next combustors have been
manufactured FANN test are
performed
• Correlation between CFD
and experimental data are
good
Low Emission Combustion Technologies –
Low emissions approaches:
Rich Burn Combustion
Optimised RQL (Rich burn - Quick quench - Lean burn)
combustion concepts with rapid quenching and reduced
residence times
staged rich burn combustors operating within narrow
stoichiometry limits
Lean Burn Combustion
Lean Direct Injection LDI
Lean Premix Prevaporise LPP, LP(P)
Air Staging – Variable Geometry
Lean Burn Combustion Technology – Principle
4-63
63
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%
Lean burn combustors
For lean burn combustor, a large percentage (60-80) of the combustor
air flow goes through the fuel injector.
The fuel /air mixing process is very important
Often pre-cessing vortex cores are observed.
Lean burn fuel injector
11/10/11
Lean combustor CFD validation
The Big Optical Single Sector located at DLR Cologne
Rolls-Royce proprietary information - private
Lean burn CFD validation
Set-up:
~ 10m Cells
Combusting Large Eddy Simulation
Hybrid Mesh
Hexa cells in core
FGM Combustion model
Liquid kerosene fuel
~ 150k Time steps to achieve good
statistics
Lean burn systems are much more difficult to model:
• Lean combustion: stabilisation through flame propagation
• Combustion is staged: pilot & mean combustion zones
• Much more swirl dominated, associated unsteady behaviour
Rolls-Royce proprietary information - private
Lean combustor modelling
- Temperature
Instantaneous
Results
- Velocity
11/10/11
Lean combustor CFD verification: Results
Private - Rolls - Royce Data
Mean Temperature
OH* Temperature
Mean Fuel (C12H23) Mass-fraction
C* spectral response
11/10/11
Lean combustor CFD verification- Results
Axial Velocity PIV (Spray & Seeding)
Mean Axial Velocity LES
A
B
Velocity field behind fuel injector well captured by CFD
Rolls-Royce proprietary information - private
A B
Plane A
Axial Velocity
Radius
Radial Velocity
Radius V
elo
cit
y
Averaged ~ 0.04 s Averaged ~ 0.08 s
Lean combustor CFD verification
Velocity field behind fuel injector well captured by LES, but long averaging times are
required.
Rolls-Royce proprietary information - private
A B
Plane B
Axial Velocity
Radius
Ve
loc
ity
Radius V
elo
cit
y
Radial Velocity
Lean combustor CFD verification
Long integration time required to get predict pilot velocity correctly
Emissions Modelling: NOx
Lean combustor
Using different injector geometries
Trend predicted reasonably
However, higher accuracy required for
reliable design process
Uncertainties in temperature field and
spray modelling have large effect on
emissions 4
6
8
10
8 12 16 20
Computed EINOx
Me
asu
red
EIN
Ox
Combustor CFD Modelling –
Lean burn combustor exit traverse prediction
14 ·106 grid cells
0 20 40 60 80 100
Duct Height [%]
RT
DF
FANN tes t
CFD
Polynomisch(CFD)Polynomisch
(FANN tes t)
FANN testCFD
full annular test
Radial averaged temperature well
predicted. However, considerable
differences in 2D temperature field
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
Lean Burn Combustion –
RR Lean Burn Technology
0% 20% 40% 60% 80% 100%
%FN
NOx Smoke
ICAO idle ICAO approach ICAO climb ICAO MTO cruise
Pilot only
As Power increases Pilot to Main split reduces
1st staging
point above
idle power
Pilot, all mains
2nd staging
point at mid
power
CO
Pilot, part mains
Staging optimised for
emissions. CO and PM (invisible
smoke) only produced during
transients.
Lean Burn Combustion –Fuel Staging Scenario
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
77
BOSS/ HBK1 HPSS/ HBK3
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 concentration
PIV 2D velocity field
Method Variables
Test rigs for lean burn injector development
Injectors easily exchangable between
both rigs
HPSS: very robust and reliable, focus:
full scale emission performance*
BOSS: optical access / non-intrusive
measurements, focus: investigation of
detailed flow/ mixing/ combustion
effects, generation of design rules
4-78
78
Lean Burn Injector – Staged Operation at Elevated Pressures
Internally staged lean burn fuel injector
kit of parts with
pressure atomiser
pre-filmer 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
C-B high pilot split
Lean Burn Injector Performance at Take-Off Condition
97,0
97,5
98,0
98,5
99,0
99,5
100,0
0 20 40 60 80
Pilot Fuel@AFRm=30
eta
CC
%
0
2
4
6
8
10
12
14
EIN
Ox(
g/k
g)
BOSS
HPSS-eta
HPSS-EINOx
Fuel Split (%)
Combustion
Efficiency
[%]
EI(NOx)
[g NOx/ kg Fuel]
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%
20% Split 40% Split 60% Split
Fuel Splitting Effect (Split = Pilot/ Total Fuel Flow) Cruise Condition (P30 = 9.4 bar,
T30 = 713 K, AFR = 30)
Lean Burn Injector Performance at Cruise Condition
4-81
Spray before ignition
1st burner ignition
2nd burner ignition
SARS – Sub-atmospheric Relight Sector Rig, RR Derby Twin sector – Subatm. Tests for Ignition, Light-across and Efficiency
Pilot only – narrow cone spray
Pilot only – wide cone spray
82
Lean Burn Validation on System Level – Rolls-Royce demonstration of low emission lean burn combustor
module and fuels and control system within real engine
environment on ground and in flight
E3E March 2008 Core 3/2
March/April 2010 Core 3/2b
July/August 2011 Core 3/2c
Juni 2012 Core 3/2d, Rain ingestion testing
Test at ILA Stuttgart, Germany
Trent 1000 - New Technology Demonstrator
ALECSYS – System validation on flying test bed
B747 with mod Trent 1000 engine, planned for 2019
EFE - Feb 2010 Bristol, UK
Low Emission Combustion Technology –
NOx emissions reduction potential
ICAO Emission Limits for engines above FN 20000 lbf ( 89 kN)
ANTLE
E3EII
PW TALON X
CAEP/2
CAEP/4
CAEP/6
CAEP/8
ACARE target 2020: 40%
CAEP/2
0
20
40
60
80
100
120
10 15 20 25 30 35 40 45 50
Overall Pressure Ratio
ICA
O L
TO
Dp
NO
x/F
oo
[g
/kN
]
RR
RRD
RRC
Pratt & Whitney Aircraft Group
International Aero Engines
General Electric
CFM International
GE TAPS Lean Burn
RR Rich Burn
© 2012 Rolls-Royce Deutschland Ltd & Co KG
The information in this document is the property of Rolls-Royce Deutschland Ltd & Co KG 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 Deutschland Ltd &
Co KG.
This information is given in good faith based upon the latest information available to Rolls-Royce Deutschland Ltd & Co KG, 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 Deutschland Ltd & Co KG or any of its subsidiary or associated companies.
©2012 Rolls-Royce Group
The information in this document is the property of Rolls-Royce Group 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 Group.
This information is given in good faith based upon the latest information available to Rolls-Royce Group, 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 Group or any
of its subsidiary or associated companies.
Tuesday, 20 December 2018, Sydney
Gas turbine Combustion
Modelling
Alternative fuels
Dr. Ir. Ruud Eggels
Rolls-Royce Deutschland Ltd & co KG
Eschenweg 11
Dahlewitz-Berlin
15827 Blankenfelde-Mahlow
Germany
Fuel criteria
Safety and operability issues Energy density
Chemical characteristics
Environmental and social issues Fuel lifecycle CO2 emissions
Change in land and water usage
Feedstock competition with food crops
Large-scale commercial production issues Fuel technology maturity level
Production capability and readiness level
Impact of fuel properties
Material
Compatibility
Aromatics, freezing pt.
Acidity, Copper Strip
Certification
All Characteristics
Durability
As Above
Lubricity
Acidity
Safety
Flash Pt., Freezing Pt.
Microsep
Maintenance
Same as Durability
Legacy Hardware
Aromatics, lubricity
Cost of
Ownership
ThermalStab.
Exist. Gum
Sulfur
Future Technology
Specific Heat, Thermal Stab.
Aromatics, Sulfur/polar Materials
System Design
& Materials
All Characteristics
Performance
Heating Value
Density
Flash/Freezing Pts.
Cold Start &
Alt re-light
Flash Pt., Heating Value
Distillation, viscosity
Deposition
(coking)
Thermal stability, Gum,
Distillation
Hot-End Life
Thermal Stability, Acidity
Aromatics, Sulfur
Physical
Properties
Chemical
Properties
Fluid Performance
Prediction
Freezing Pt., viscosity
Distillation, Thermal stability
Emissions
Aromatics, Sulfur
distillation
Growth in Aviation
Rolls-Royce proprietary information - private
Ref: Airbus
Eco-Efficient Aviation
Aviation needs to flourish with reduced
environmental impact
Aviation is necessary for development
Facts:
8% Global GDP
2% man made CO2 emissions
Over 40 years the focus on innovation
has lead to
70% reduced aviation fuel
consumption and related CO2
emissions
Targets:
Carbon Neutral growth by 2020
50% CO2 reductions by 2050
compared to 2005
Sustainable Aviation Growth with Environmental targets
Page 88
CO2 Emissions Trends
Ref: ICAO
Background: What’s Required?
• Meet all current safety requirements
• Same Aircraft performance considerations
• Same properties as Aviation Jet-fuel Kerosene
Consistent, thermally stable,
High energy content
Low freezing point, high flash point...
- Freezing point (- 47 °C)
• Meets Jet-fuel specifications
Any new fuel has to meet the above characteristics
Page 90 Ref: Airbus
Background: Short/Medium Term Requirement
• Use existing airport fuel storage
• Common aviation fuel distribution network
• With common piping and transport infrastructure / mechanisms
• Any alternative should be “drop-in”
…..and mixable with fossil fuel
A “Drop-in” solution is required
Page 91 Ref: Airbus
Where we are: What are the Options?
Non-Renewable
(Fossil)
Renewable
Jet Fuel
CTL
GTL
Hydrogenated Biomass Oils
(HBO)
Low energy content per unit volume, Availability,
Infrastructure
Cryogenic Fuels
Ethanol … Fame
Hydrogenated Biomass
BTL
Liquefied Natural Gas
Conventional (“Kerosene”)
Alcohols Bio Esters Synthetic Fuels
10% lower energy
content,
-5°C Freeze point…
35% lower energy content
Liquid Hydrogen
TYPE
BIO- JET
FUELS
* FAME =Fatty Acid Methyl Esters CTL, GTL & BTL =Coal, Gas or Biomass to Liquid
Not all options are suitable for aviation today Page 92
Ref: Airbus
Algae
Jatropha
Salicornia Camelina
Wood waste
Yeast
What are the alternative fuels? Potential sustainable feedstocks
Multi options in different locations
Page 93 Ref: Airbus
Production route for alternative fuels
Rolls-Royce proprietary information - private
The supply of large quantities of alternative kerosene within low GHG emissions
is (theoretically) possible by coupling the sectors electricity generation and fuel
markets (without biomass imports).
Ref: DLR
Comparison of CO2 Emissions from alternative fuels
6
8
10
12
14
16
18
20 n-P
i-P
N
DiN
MoArNmoAr
DiAr
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
%
C numberChemical type
n-P
i-P
N
DiN
MoAr
NmoAr
DiAr
Fuel composition example
Typical Jet A-1
Shell Bintulu
GTL fuel
Rolls-Royce joins Air New Zealand and Boeing in renewable fuels study programme Flight evaluation of a renewable bio fuel blended with kerosene fuel source
Part of research programme to understand renewable fuels and potential future applications.
Aircraft – ANZ 747-400, Engine – RB211-524GT – only one engine will use the fuel
Timing –Dec 2008
Fuel analysis shows fuel meets/exceeds current specification technical requirements
50:50 Blend – Jatropha derived SPK (HVO) and std Jet A-1
Therefore is drop-in.
Data gathered throughout the test process will contribute to understanding of the capabilities
and limitations of renewable fuels
After the evaluation, the engine was examined/overhauled prior to returning to service.
Airbus / Shell / Rolls-Royce A380 demo Flight evaluation of a 40% GTL kerosene fuel blended with conventional fuel
Part of research programme to understand renewable fuels and potential future
applications.
Aircraft - Airbus A380 MSN4
Engine - Trent 900 – only one engine used the derived fuel
Timing – 1 Feb 2008
Data gathered throughout the test process reported and contributing to
understanding of the capabilities and limitations of renewable synthetic fuels
GTL Fuel used in A380
GTL fuel manufactured at the Shell Bintulu plant.
This plant produces 14000 barrels of product per day
Plant is tuned to deliver diesel fuel.
For flight test fuel was blended with Jet A1 to produce min SG
from def stan91-91.
Flight from Bristol to Toulouse.
3 Hr flight
1 engine of 4 was fuelled with alternative fuel.
Handling of the engine was carried out at several altitudes.
Altitude relight tests were also performed.
All the testing was successful.
Airbus GTL* Flights
*GTL = Gas To Liquid
Synthetic fuels work and are a precursor for Biofuels
• February 2008 Flight test
~50% GTL
A380 on one out of the four engines
Rolls-Royce engines
• October 2009 First ever commercial revenue
flight
~50% GTL
A340-600 all engines
Rolls-Royce engines
Page 100 Ref: Airbus
Cost of aviation fuels
Rolls-Royce proprietary information - private
ECLIF Measurement results
Rolls-Royce proprietary information - private
ECLIF Measurement results
Rolls-Royce proprietary information - private
CO and NOX emissions very
similar
ECLIF Measurement results
Rolls-Royce proprietary information - private
ECLIF Measurement results
Rolls-Royce proprietary information - private
ECLIF Measurement results
Rolls-Royce proprietary information - private
ECLIF Measurement results
Rolls-Royce proprietary information - private
ECLIF key conclusions
Alternative jet fuels with lower aromatic content (i.e. higher H
content) produce less soot emissions.
First measurement showing the effect of naphthalene's.
First ground and in-flight emissions measurements with a Fully
Synthetic Jet Fuel (Sasol’s FSJF). .
Synthetic jet fuels yield a decrease in concentration and size of
soot particles.
Ice particles measurements show a definite correlation with soot
emissions characteristics.
First experimental validation of impact of soot particle size on
contrail characteristic (radiative properties).
Rolls-Royce proprietary information - private
Summarising
Potential for significant emissions reductions
Depends on feedstock type and cultivation, conversion
process…
Emissions reductions achievable with existing aircraft
Benefits will depend on:
the availability of such fuels and the time profile of their
deployment
their actual lifecycle emissions reduction
Challenges
Decreasing production cost
Investment in feedstock production and conversion facilities
Ensuring a sustainable deployment
Recommended