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Session 3: Novel fuels
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04/04/2017 © The University of Sheffield
Dr. S. Blakey
Objectives
• Inform on current position
• Introduce concept of “fit for purpose” testing + examples
• Set the scene for technical requirements of fuel in the future
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… from yesterday – why?
• Security of supply
• Environmental Sustainability
• Keep in mind, drivers for novel alternative fuels are not technical alone (as will be discussed here) but also economic / substantiality criteria.
• Part of this is the pull to novel automotive diesels – bigger market – not as difficult to get into. New starters are likely to ignore Jet and make diesel.
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0
5
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30
35
40
800 1000 1200 1400 1600 1800 2000
Turbine entry temperature (K)
Over
all pre
ssure
rat
io .
WR1
DerwentSapphire
Avon
Olympus 101 Adour
Olympus 22R Pegasus 11
RB199-101
Spey
V2527-A5
Early AF work• Low pr, T3 dominated
by physical
characteristics of fuel
• High pr, T3 dominated
by fuel chemistry /
mixing
• Broad range of fuels
tested (12 – 15%H
wt.)
1990 study
1980 study
Engines certified in 2000
• Focus on Combustion alone
- not other properties
Synthetic fuels
• Aviation kerosene
• Narrower Boiling ranges
• FT / HEFA
• (But would be broader if not for Diesel)
• Specific isomers
Sugar / fermentation
Microbial routes
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Significance of change
• Boiling range
• Freeze point
• Clear reduction in density Change in PM emissions Interaction with fuel system
• Seal compatibility, thermal stability, …
• But… potentially something simpler to predict!
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Loss of aromatic fraction
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0
20
40
60
80
100
%m
as
s
HDCJ #1
Alternative fuels: changes to fuel composition
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20
40
60
80
100
%m
as
s
Conventional fuel #1
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%m
as
s
HEFA #1
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20
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%m
as
s
pure FT-SPK #1
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%m
as
s
DSHC/SIP#1•
•
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%m
as
s
ATJ-SKA#1
0
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60
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100%
ma
ss
SK #1
Source: FAA
FT‐SPK: FT Synthetic Paraffinic Kerosene
HEFA: Hydroprocessed Esters and Fatty
Acids
SIP: Synthesized Iso-Paraffins (formerly
Direct Sugar to Hydrocarbons) – limited to
10% blends
ATJ – Alcohol to Jet Synthesized Paraffinic
Kerosene (also ATJ-SKA, containing
aromatics)
HDCJ – Hydroprocessed Depolymerized
Cellulosic Jet (Pyrolysis amongst others)
HDO-SK Hydrodeoxygenated Synthesized
Kerosene
Fuel Composition Change? Fuel properties
Physical mechanisms Atomisation, Chemical kinetics,
biocontamination, low temp
performance,…
Combustor performance LBO, Altitude relight, gaseous
emissions, PM emissions,
acoustics…
Interaction with fuel system Hot end durability, Seal
compatibility, thermal stability,
lubricity,
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Aromatic content
Paraffinic groups
Carbon number
distribution…
Pathways and fuels
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Reality check
• One size doesn’t fit all – diversity is good?
• Many small new players – maintaining quality?
• Environmental sustainability of feedstock
• Beyond specification testing
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M. Rumizen, (2017)
US perspective
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J. Hileman, (2017)
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J. Hileman, (2017)
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J. Hileman, (2017)
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J. Hileman, (2017)
Reality check
• One size doesn’t fit all – diversity is good?
• Many small new players – maintaining quality?
• Environmental sustainability of feedstock
• Beyond specification testing
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Novel?
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A. Roth (2017)
Efficiency
• Photosynthesis: is inefficient for the harnessing solar energy
• Less than 1% overall efficiency
• Solar-to- fuel around 9%
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A. Roth (2017)
Using waste streams
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J, Harmon, (2017)
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J, Harmon, (2017)
Generic Properties
• Simpler chemistries potentially something simpler to predict!
• Significant amounts of data now available for the performance of novel fuels –trends are emerging…
• Where possible these should be exploited to reduce requirements for testing.
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20Moses, (2016)
Generic Properties
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600
650
700
750
800
850
900
-50 0 50 100 150 200
Den
sity
(kg
/m^3
)
Temperature (degC)
Octane (C8)
Dodecane (C12)Decane (C10)
Benzene (C16)
CRC Jet A-1 average
• Build up performance from GCxGC
• Applicable where models for properties exist / significant amounts of fundamental data exists.
• Much simpler for well defined properties.
• Issues with extrapolation
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200
220
240
260
280
300
320
340
10 15 20 25 30
Wall
tem
pera
ture
(d
eg
C)
Rise in Bulk fuel temperature (degC)
Baseline
Baseline-Dittus-Boelter
GtL
GtL-Dittus-Boelter
Stage 1
Stage 2
Stage 3
Stage 4
Bulk properties not in spec.
• Heat transfer characteristics
• Not Jet fuel as we know it…
• Uncertainty in k measurement
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Calculated based on extrapolated physical properties andDittus-Boelter correlationUncertainty in k large ±25%?*
*Moses, C., et al., IASH 2011
Fuel at 180C
What is a Fit for Purpose test?
• Scaled down testing to assess technical suitability for
• properties not supported by the specification
• Properties beyond the specification
• no-one has agreed the conditions that show FFP
• all done by comparison
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Techniques
• Scaled testing
• Using scaled down experiments – cost / availability of AF fuels
• Test still need to be representative – limits of scale?
• Fit For Purpose testing
• Modelling to bridge …
Initial Population
Fitness Function
Objective Function
Filter Function
New Population
Parent pop
Children pop
Intermediate pop
GA Operations (Tournament, Crossover, Mutation) and
construction of Intermediate population
Old Population
Sending the whole population for GA
Operations
Intermediate pop
Copy
Evaluation and return
fitness
Evaluation and
return fitness
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Assessing emissions performance
• APU engine as test vehicle• RR Artouste MK113
• Honeywell GTP GTCP85
• Wide range of AFs tested, both commercial and fundamental programmes
• Standard gaseous emissions
• PM and UHC speciation
• Smaller scale testing for smoke
• Modelling – allows scaling of results
Examples
Impact on PM
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Lobo et al. (2015)
APU
Main engine start
Mass
• APU engine results
• SAE AIR 6241 Specification
• Mass based – Artium LII-300
• Number – AVL APC
• Low aromatics challenge for
seals – system needs to be
assessed multidimensionally
APU
Main engine start
Number
Assessing seal performance?
• Doesn’t leak!
• Result artefact of test:
• Only capable relative ranking
• Static - Volume swell, diameter change, hardness, mass
• Discrete dynamic - Cycle then perform static test at intervals
• Continuous dynamic tests - Stress Relaxation / temperature cycling
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Examples
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paraffinssaturated and linear chains
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
paraffinssaturated and linear chains
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
iso-paraffinssaturated and branched chains
C
H
C
C
C
H
C
H
H
C
H
C
C
H
C
C
C
H
C
C
H
C
H
H
C
H
H
iso-paraffinssaturated and branched chains
C
H
C
C
C
H
C
H
H
C
H
C
C
H
C
C
C
H
C
C
H
C
H
H
C
H
H
0.7
0.8
0.9
1
1.1
1.2
0 40 80 120 160
F/F
0
Time, hrs
Change in SPK
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Seal swell
Seal relaxation / polymer extraction
Nitrile
Liu, Wilson, Advances in Mech. Eng, 2012
Elastomer Comp. conclusions
• Increase in SPKs in blends can reduce swell
• Volume of decalin required to swell nitrile O-ring in order to be comparable to Jet A-1 is too high (over 60%)
• Temperature effects – low temperature performance?
• Selection of specific components (cyclic paraffins / aromatics can provide swell)
… but what other FfP properties will be affected by this?
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Assessing thermal stability
• Not possible to sum up in single property of fuel / system interaction
• Artefact of test (again!)
• Static – Flask Oxidation
• Discrete Flowing - JFTOT
• Continuous Flowing – HiReTSand research rigs & large scale simulators
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Examples
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Scale and Thermal Stability
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Fue
l vo
lum
e (
L)
tim
e o
r co
st
Engine bed tests
Flight tests
Flow tests
Static tests
0.1
Simulator rig tests
1
10
102
103
104
105
a. Stainless-steel tubing before testing
b. Stainless-steel after 24 hours
**S97112
0.0
0.1
0.2
0.3
0.4
0.5
0.6
A
b
s
o
r
b
a
n
c
e
1000 1500 2000 2000 3000 4000
Wavenumbers (cm-1)
Approach to reality
QCM
SEM
FTIR
ICOT
After Spence Taylor (2008)
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30 0
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150
Time (min)
Run 5, 1000ppm + 400ppm water
Distance fromDatum (mm)
De
lta
Te
mp
era
ture
(d
eg
C)
Small scale: HiReTS (IP/EI 482)
Flow
Final ΔT
Min ΔT
• Flow through 250m 150mm heated capillary
• Fuel heated to 290C at outlet
• Temp measured externally
• Total HiReTS number
• More to be gained by using complete data set
Time (mins)
Blakey et al., IASH 2011
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30 0
50
100
0
50
100
150
Time (min)
Run 5, 1000ppm + 400ppm water
Distance fromDatum (mm)
De
lta
Te
mp
era
ture
(d
eg
C)
Small scale: HiReTS (IP/EI 482)
Flow
Final ΔT
Min ΔT
• Flow through 250m 150mm heated capillary
• Fuel heated to 290C at outlet
• Temp measured externally
• Total HiReTS number
• More to be gained by using complete data set
Time (mins)
Blakey et al., IASH 2011
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Conventional fuel
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• Spec test - Pass / fail, Fit for Purpose - quantative
• What is a conventional fuel?
• Presence of Sulphur, hetroatomic species and other leftovers after refining process.
• Careful selection of baseline required
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30 0
50
100
0
10
20
30
Time (min)
IBC 08
Distance from Datum (mm)
De
lta
Te
mp
era
ture
(d
eg
C)
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30 0
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Time (min)
Distance fromDatum (mm)
De
lta
Te
mp
era
ture
(d
eg
C)
Description HiReTS
Total No.
HiReTS
Peak No.
Straight run Jet A-1 605 72
Hydrotreated Jet A-1 104 21
Pure SPKs
• Very high thermal stability
• Lack of “other” species
• Lack of saturated bonds
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0
10
20
30 0
50
100
0
20
40
60
80
Time (min)
0ppm
Distance from Datum (mm)
De
lta T
em
pe
ratu
re (
de
gC
)
Description HiReTS
Total No.
HiReTS
Peak No.
Neat GtL 7 4
Aromatics
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• GtL base
• Addition of aromatic components (more C than H)
Blakey et al., IASH 2013
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10
20
30 0
50
100
0
20
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60
80
Time (min)
10000ppm
Distance from Datum (mm)
De
lta T
em
pe
ratu
re (
de
gC
)
1000ppm
Description HiReTS
Total No.
HiReTS
Peak No.
GtL + 2% Toluene 19 4
GtL + 8% Toluene 20 5
GtL + 16% Toluene 42 6
GtL + 16% Tetralin 40 6
GtL + 8% Naphthalene 58 10
GtL + 1% m-toluidine 645 72
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Thermal Stability Conclusions
• Move to synthetic fuels beneficial
• Not all aromatics are bad – careful selection of blend
• High(er) impact of trace components
• Continued assessment required
• Can benefit result in improvements in engine hardware?
• Challenge: if all future engines were designed to take advantage of these good new fuels, new engines would still have to cope with the overwhelming volume of “conventional” jet fuel, or else have fuel supply issues
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Conclusions
• Wider fit for purpose testing well supported by D4054 (Novel Fuels Approval Process)
• Component by component selection is a reality
• Research effort required
• Can specification envelope be widened?
• Imposed limit on aromatics for seal swell is not the only solution
• Impact beyond FfP tests will need to be assessed
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Upcoming questions
• Inside Specification box – how far can we go?
• Effect of increasing isomerisation
Boiling point range, LBO, altitude relight…
• Effect of lower levels of aromatics or which ones?
Fuel gauging, range / payload, emissions, seal performance, thermal stability…
• Outside Specification box
• Cost / Benefit needs assessing – no downside
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Session 3: Novel fuels
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04/04/2017 © The University of Sheffield
Dr. S. Blakey
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