Med Colket, Steve Zeppieri, Zhongtao Dai,

and Don Hautman

5th Annual Fuel Research Meeting Multi-Agency Coordinating Council for Combustion Research

Sandia National Laboratories, Livermore, CA

September 17-20, 2012

Fuel Research at UTRC

2

Background

Secure supply

Military needs guaranteed fuel supply in time of war

Global Warming:

Combustion of fossil-derived fuels

Combustion emissions (soots/particulates)

Physics-based combustor models

Existing models barely sufficient for design predictions

Physical vs. chemical effects

Typically, physical effects presumed to dominate (except soot)

Complexity of fuels

Large number of species

Unknown/uncertain reaction rate laws

DoD needs

AF – 50% utilization of alternative fuels by 2016 (in US)

Navy - Sailing the 'Great Green Fleet' by 2016/50% Utilization by 2020

SERDP – Understand impact on emissions

3

Acknowledgements

Sharon Beermann-Curtin

Jennifer Klamo

Mel Roquemore

Tim Edwards

Dale Shouse

Bruce Sartwell

Fokion Egolfopoulos

Matt Oehlschlaeger

Tonghun Lee

Tony Dean

Bob Kee

Bill Pitts

Tom Litzinger

Jeff Lovett

Heidi Hollick

4

Objectives and Outline

Objectives:

Develop/apply methods/tools that can incorporate both physical and chemical effects to predicting impact on engine performance

Outline:

New data sets – performance of fuels in research combustor

Fuel selection

Combustor

Emissions, LBO data

Surrogates and Predictions

Hydrocarbon Emission Fingerprint

Discussion of controlling phenomena

Quantitative comparisons

Brief update/comments on AF Rules and Tools program

Summary

Recommendations

5

Combustor Validation Data – Fuels Tested

Feedback from ONR – We need combustor data for different fuels!

Fuels Description

Mean

MW

Flash

Point [C]

Density

[g/ml]

Cetane

#

IBP FBP

Jet-A Baseline

JP-5 Baseline 63 0.815 182 253 43.0

HRJ

JP-5

ONR Supplied, Camelina

based alternate fuel 62 0.768 174 286 66.0

Sasol

IPK

Coal-derived kerosene,

supplied by AFRL (POS

7629) 149 53 0.765 174 232 31.3

Shell

GTL

Natural gas based gas-to-

liquid kerosene, supplied by

AFRL (POS 5729) 137 43 0.736 154 195 58.4

LinPar

1416 Low aromatic solvent 201 117 0.768 247 277 81.8*

L-142 Low aromatic solvent 156 61 0.804 177 233 46.5*

L-210 Low aromatic solvent 193 96 0.825 240 283 53.1*

Boiling Pt.

[C]

6

Combustor Validation Data – Fuels

(cyclo: sum of monocyclic and dicyclic compounds

0

10

20

30

40

50

60

70

8 9 10 11 12 13 14 8 9 10 11 12 13 14 15 16 8 9 10 11 12 13 14 15 13 14 15 16

Ma

ss F

ract

ion

[%

]

Carbon Number

normal-

iso-

cyclo-

Sasol IPK Shell GTL

LinPar 1416

L-142 L-210

Wide range of chemical properties

Solvents and synthetic fuels explore contrasting physical/chemical changes

7

Combustor Validation

Validation data sets for JP-5 and alternatives

Testing performed in UTRC JBTS facility

Rig simulates conventional combustor flowpath/operation

8

Rich-Quench-Lean (RQL) Combustor Technology

Optimized for operability while minimizing

NOx emissions and combustor length

9

Combustor Validation Data – Emissions

Small changes for NOx and CO (emission indexes)

0

5

10

15

20

25

30

0.5 1 1.5 2 2.5

EIN

Ox

Front End Equivalence Ratio

T4=735F, P4=128psi

JetA-08_01_2012

JetA-08_07_2012

JP5-08_01_2012

SJP5-08_03_2012

Sasol-08_28_2012

Linpar-08_29_2012

L142-08_06_2012

L210-09_10_2012

Alkane based fuels produce

slightly lower NOx

0

40

80

120

160

0.5 1 1.5 2 2.5E

ICO

Front End Equivalence Ratio

T4=735F, P4=128psi

JetA-08_01_2012

JetA-08_07_2012

JP5-08_01_2012

SJP5-08_03_2012

Sasol-08_28_2012

Linpar-8_29_2012

L142-09_06_2012

L210-09_10_2012

NOx

CO

10

Combustor Validation Data – Emissions

Smoke data for several jet fuels and solvents

10

Alkane based fuels

(synthetic jet fuels and

solvents) produce less

soot.

Anomalous high soot

levels at low f/a ratios

for Camelina HRJ

(SJP5)

0

20

40

60

80

0.5 1 1.5 2 2.5

Smo

ke N

um

ber

f - Front End

T4=735F, P4=128psi

JetA-08_01_2012

JetA-08_07_2012

JP5-08_01_2012

SJP5-08_03_2012

Sasol-08_28_2012

Linpar-08_29_2012

L142-09_07_2012

L210-09_10_2012

11

Fuels Analyzed (courtesy of Tonghun Lee (MSU))

11

• Navy & Air Force Fuels Total Ion Chromatograms

Petroleum JP-5

Camelina HRJ

(JP-5)

Camelina HRJ

(JP-8)

Retention Time [min]

Anomalous soot possibly due to large concentration of high MW species

12

0.55

0.56

0.57

0.58

0.59

0.60

0.61

0.62

0.63

0.64

0.65

Sasol IPK L-210 JP-5 Jet-A L-142 HRJ JP-5 Linpar

1416

Fro

nt-

End

Eq

uiv

ale

nce

Ra

tio

Test 1

Test 2

Test 3

Combustor Validation Data – Lean Blow Off

Lean Blow-Out (LBO) data

Highest temperature (most robust)

Lowest Pressure (least robust)

13

Combustor Validation Data – Lean Blow Off

LBO data

Highest temperature (most robust)

Lowest Pressure (least robust)

0.55

0.56

0.57

0.58

0.59

0.60

0.61

0.62

0.63

0.64

0.65

Sasol IPK L-210 JP-5 Jet-A L-142 HRJ JP-5 Linpar

1416

Fro

nt-

End

Eq

uiv

ale

nce

Ra

tio

Test 1

Test 2

Test 3

Uncertainties are significant

14

Combustor Validation Data – Lean Blow Off

LBO data for jet fuels and solvents

Highest temperature (most robust)

Lowest Pressure (least robust)

0.55

0.56

0.57

0.58

0.59

0.60

0.61

0.62

0.63

0.64

0.65

Sasol IPK L-210 JP-5 Jet-A L-142 HRJ JP-5 Linpar

1416

Fro

nt-

End

Eq

uiv

ale

nce

Ra

tio

Test 1

Test 2

Test 3

Petroleum fuels are similar;

HRJ maybe slightly better

15

Modeling Methods – Physical Models

Lean Blow Off – Extinction of a ‘Perfectly Stirred Reactor’

Simplified, kinetics-based model of physical problem (CHEMKIN based)

1600

2100

2600

3100

3600

1.00E-06 1.00E-05 1.00E-04 1.00E-03

Tau (sec)

Tem

pera

ture

(F

)

n-Heptane/Air

Ti = 1857 F

P = 6 atm.

Phi = 2.0

PSR

Extinction Time

PSR Ignition Time

Extinction

Time

Ignition

Time

Te

mp

era

ture

Tau (sec)

Volume, V

Residence time,

Temperature, T

Enthalpy, hk

Mass Fraction, Yk

inlet outletm

Y*k

h*k

m

Yk

hk

Heat loss

Q

. .Volume, V

Residence time,

Temperature, T

Enthalpy, hk

Mass Fraction, Yk

inlet outletm

Y*k

h*k

m

Yk

hk

Heat loss

Q

Volume, V

Residence time,

Temperature, T

Enthalpy, hk

Mass Fraction, Yk

inlet outletm

Y*k

h*k

m

Yk

hk

Heat loss

Q

. .

16

Surrogate Selection – preliminary (awaiting new data)

Targets –

Chemical

classes, MW

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

n-decane 0 0 0 0

n-dodecane 0 35 0.358 35 0.349 0

n-tetradecane 0 0 0 0

n-cetane (n-hexadecane) 43 0.428 25 0.264 25 0.257 0

iso-octane (2,2,4-trimethylpentane) 20 0.178 40 0.378 0 20 0.188

2,2,4,6,6-pentamethylheptane 0 0 40 0.394 70 0.704

methylcyclohexane 15 0.149 0 0 0

n-butylcyclohexane 0 0 0 10 0.109

m-xylene (1,3) 22 0.245 0 0 0

grams/cc 0.776 grams/cc 0.732 grams/cc 0.751 grams/cc 0.736

MW 137.5 MW 152.1 MW 181.9 MW 152.7

H/C 1.903 H/C 2.19 H/C 2.16 H/C 2.16

BP(K) 462.8 BP(K) 463.8 BP(K) 493.3 BP(K) 438.1

ONR - JP-5 ONR - JP-5 (HRJ) ONR - JP-5 (HRJ) - a Sasol IPK

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

Liq vol

fraction

Mass

fraction

n-decane 30 0.305116 0 0 0

n-dodecane 0 30 0.293 0 10 0.099

n-tetradecane 0 0 0 0

n-cetane (n-hexadecane) 0 70 0.707 0 5 0.051

iso-octane (2,2,4-trimethylpentane) 40 0.386 0 0 0

2,2,4,6,6-pentamethylheptane 30 0.309 0 30 0.286 60 0.589

methylcyclohexane 0 0 20 0.198 0

n-butylcyclohexane 0 0 50 0.515 15 0.159

m-xylene (1,3) 0 0 0 0

grams/cc 0.718 grams/cc 0.766 grams/cc 0.775 grams/cc 0.753

MW 136.3 MW 206.5 MW 135.6 MW 171.0

H/C 2.21 H/C 2.14 H/C 2.05 H/C 2.13

BP(K) 420.2 BP(K) 539.4 BP(K) 438.0 BP(K) 466.4

Shell GTL Linpar 1416 L-142 L-210Reaction model

complied from

JetSurf,

SERDP, LLNL

(iso-octane) +

new

isododecane

model

17

Iso-dodecane Combustion Model

Iso-Octane

(2,2,4 tri-methyl-pentane)

Iso-Dodecane

(2,2,4,6,6 penta-methyl-heptane)

Iso-Cetane

(2,2,4,4,6,8,8 hepta-methyl-nonane)

-Gasoline primary reference fuel -Diesel reference fuel

Constructed by analogy from Curran, et al iso-octane model

Pyrolysis portion validated against data (see Zeppieri, et al)

Higher MW iso-alkane oxidation model needed to match jet fuel MW

Detailed model unavailable

18

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

0.0004 0.0006 0.0008 0.001 0.0012

Ign

itio

n D

ela

y [s

ec.

]

1/Temperature [K-1]

Iso-Octane

Iso-Dodecane

P=10 atm.Stoichiometric Fuel-Air

Oxidation Model Benchmarked Against Iso-Octane Model

Iso-Dodecane ignition delay comparable to iso-octane value above ~1500 K;

Iso-C12 delay ~ 1.3-1.75 x Iso-C8 delay below 1500K

19

Computed Stirred Reactor Extinction Times

surrogates

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9

Exti

nct

ion

Tim

e [

sec.

]

PSR Equivalence Ratio

Sasol IPK

L-210

L-142

Jet A

JP-5

HRJ JP-5

Linpar 1416

Test Conditions:

T3: 430 F

P3: 80 psia

Combustor LBO Calibration (1.1E-04 sec)

20

Comparison to Model Calculations

PSR Extinction Times consistent with Experimental Trends

0.54

0.56

0.58

0.6

0.62

0.64

0.66

0.68

0.56 0.58 0.6 0.62 0.64 0.66

Sim

ula

ted

Fro

nt-

End

LB

O E

qu

iv. R

atio

Experimental Front-End LBO Equiv. Ratio

Sasol IPK

L-210

L-142

Jet-A

JP-5

HRJ JP-5

Linpar 1416

Based on calibrated

LBO time

21

Comparison to Model Calculations

0.54

0.56

0.58

0.6

0.62

0.64

0.66

0.68

0.56 0.58 0.6 0.62 0.64 0.66

Sim

ula

ted

Fro

nt-

End

LB

O E

qu

iv. R

atio

Experimental Front-End LBO Equiv. Ratio

Sasol IPK

L-142

Jet-A

JP-5

HRJ JP-5

Linpar 1416

PSR Extinction Times consistent with Experimental Trends

Homogeneous reaction chemistry appear

to dominate – Physical effects would

suggest counter trends

22

Or ---- LBO Correlates with DCN even Better!

30

40

50

60

70

80

90

0.55 0.56 0.57 0.58 0.59 0.6 0.61 0.62

(Der

ived

) C

eta

ne

Nu

mb

er

Average Experimental Front-End LBO Equiv. Ratio

Sasol IPK

L210

L-142

Jet-A

JP-5

HRJ JP-5

Linpar 1416

23

Objectives and Outline

Objectives:

Develop/apply methods/tools that can incorporate both physical and chemical effects to predicting impact on engine performance

Outline:

New data sets – performance of fuels in research combustor

Fuel selection

Combustor

Emissions, LBO data

Surrogates and Predictions

Hydrocarbon Emission Fingerprint

Discussion of controlling phenomena

Quantitative comparisons

Brief update on AF Rules and Tools program

Summary

Recommendations

24

Challenge Problem: HC Emissions from Gas turbine Engines

Empirical evidence that emissions scale linearly – independent of engine or power

• What physical/chemical processes control this scaling?

• Can impact of alternative fuels on atmospheric pollution be anticipated?

APEX 2 APEX 3

25

Approach – presented last year

Identify chemistry and physics controlling scalability of HC emissions

Methodology:

• Utilize reactor-network formulation to simulate flowfield of burner • Fuel used: 77% dodecane, 23% m-xylene (vol %) – SERDP mechanism

• Initially assumed “bulk flow” conditions (e.g., total flow rates, total burner volume,

etc.)

• Modified to focus on conditions with measurable emission levels and those

exhibiting scaling

• Approximate “Idle”/low-power conditions:

P3 = 4.08 atm,

T3 = 478 K

F overall ~ 0.25

•

• Good Results – but Reactor Model: Too Complex!!!!

26

Reactor Network Solutions – Phi Sweep

UHC EI are functions of equivalence ratio of first quench reactor

0

20

40

60

80

100

120

140

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25

C2

H4

Exi

t E

I [g

m/k

g-fu

el]

HC

Exi

t E

I [gm

/kg-

fue

l]

CH2O Exit EI [gm/kg-fuel]

CH4-EI

CH3CHO-EI

C3H6-EI

C4H6-EI

C6H6-EI

C2H4-EI

Fuel (initial)

Primary Air

Secondary/Dilution Air

(evenly added over 20 reactors)

Fuel (final)

Lean Quench Inlet

Rich Quench Inlet

Idle (5% Power)

27

Hypothesis for Fingerprint

Fuel CO CO2 Prod1,2

Fuel => Prod1 + Prod2

Prod1 Prod2 (?) - or just decomposition species

Prod1,2 + oxidizer => CO, CO2

Prod1 , Prod2 stay in constant ratio – formation and decay

Related to known oxidation sequence

28

Example: Structure of Opposed Jet Flame (premixed)

Scaling of HC species corresponds to fuel chemistry (decomposition of parent fuel

(Burned gas vs. fuel/air)

0

500

1000

1500

2000

2500

0

10

20

30

40

50

60

70

80

90

1.1 1.105 1.11 1.115 1.12 1.125 1.13 1.135 1.14

Fue

l, C

O,

CO

2 E

I [gm

/kg-

fue

l]

EI [

gm/k

g-fu

el]

Distance [cm.]

CH2O

CH4

C2H4

C3H6

C4H6

C6H6

NC12H26

MXYLENE

CO

CO2

Reactant side

of flame

(premixed)

29

Example: Computed HC Ratios in Opposed Jet Flames

HC-EI Trends vs. CH2O-EI very similar to trends from PSR Network Analysis

(Burned gas vs. fuel/air)

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20

HC

EI [

gm/k

g-fu

el]

CH2O EI [gm/kg-fuel]

CH4

C2H4

C3H6

C4H6

C6H6

Premixed

(phi=1)

30

Extended studies

Opposed jet – premixed (variable phi)

Premixed flames (variable phi)

Altered Network reactor assumptions

Variable initial equivalence ratio

Variable initial reactor residence time

Variable quench time

O2

heated fuel/N2

flame

31

Example : Impact of Initial Equivalence Ratio

Lower branch shows scaling of EI values

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25

Eth

en

e E

I [gm

/kg-

fue

l]

Formaldehyde EI [gm/kg-fuel]

0.6

0.8

1.0

1.2

2.0

Initial Streak Equivalence Ratio:

32

Impact of Quench Time (in first quench reactor)

Scaling independent of injection time up to point of peak CH2O formation

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25

Eth

en

e E

I [gm

/kg-

fue

l]

Formaldehyde EI [gm/kg-fuel]

0.8 microsec.

1.6 microsec.

2.4 microsec.

3.2 microsec.

Quench Fuel Addition Injection Time:

33

Computed Scaling Factors vs. Experiments

- Scaling factors are slopes of HC-EI/CH2O-EI correlations

- All models used SERDP mechanism with n-Dodecane/m-Xylene Fuel

Similar results amongst model assumptions AND reasonable agreement with

experimental data

PSR

Network Opposed Jet Opposed Jet

Pre-

mixed

Pre-

mixed Spicer Aerodyne

(Lean Side)

(Burned (0.6)

vs. Fuel/Air

(Fuel/Air (1.0)

vs. Fuel/Air

Phi =

0.6

Phi =

1.0

(JP-5/CFM-

56/idle)

(AAFEX/J

P-8)

CH4 0.44 0.49 0.72 0.42 0.76 0.43 -

C2H4 3.27 4.25 3.93 3.2 4.2 2.69 1.33

C3H6 0.61 1.63 1.59 1.45 1.66 0.79 0.51

C4H6 0.06 0.23 0.14 0.14 0.15 0.3 -

C6H6 0.17 0.18 0.09 0.05 0.1 0.32 0.16

Engine DataModel Predictions

Lean side –

independent of

model

assumptions

34

0

500

1000

1500

2000

2500

3000

0

50

100

150

200

250

300

350

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tem

pe

ratu

re [K

]

Ve

loci

ty [c

m/s

ec]

Distance [cm.]

Vel.

Temp.

Time Scale Considerations

Quench time-scales need to be significantly less than reactive flame-front

residence times

0

500

1000

1500

2000

2500

-150

-100

-50

0

50

100

150

200

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Tem

pe

ratu

re [K

]

Ve

loci

ty [c

m/s

ec]

Distance [cm.]

V(cm/s)

T(K)

tau-res:

~ 250 msec. tau-res:

~ 175 msec.

PSR-quench time scales: 20 msec. Fuel (initial)

Primary Air

Secondary/Dilution Air

(evenly added over 20 reactors)

Fuel (final)

“Idle”/low-power conditions

P3 = 4.08 atm,

T3 = 478 K

35

AF – Rules and Tools Program

Restarted late last spring

Combustor rig preliminary design complete

Rig construction and testing not expected until mid next year

Fuels selected (~10)

Combustion tests recommended for the fuels

Extinction strain rate

Ignition

Flow reactor speciation

36

Conclusions – Emission and LBO tests

Lean Blow-off limits trend with chemical nature of fuel

Pure n-alkane fuel is most robust

Largely branched i-alkanes least robust

Physical effects not quantified but appear to be minor

Correlates with PSR extinction and DCN

Near to blow-off (not shown) CO emissions trend similarly

Higher power CO emissions – no clear trend

NOx emissions nearly identical

Small decrease with alkane fuels

37

Conclusions – Hydrocarbon Fingerprint

• Network PSR quench model yields linear relationship amongst selected

hydrocarbon products

• relatively independent of initial assumptions

• Linear relationships also observed through flame-fronts of opposed-jet

and premixed fuel-air systems

• Calculated emission index ratios (HCEI/CH2OEI) from PSR Network,

opposed-jet and premixed flame calculations are qualitatively similar to

each other and to experimental values

• Quenching must occur faster than progression of reaction front, e.g., 10-

50 microseconds

• Preliminary results (not shown) indicate results dependent on surrogate

chemistry

38

Recommendations - 2012

Assess LBO – DCN correlation generality – or limitations

Plot of DCN vs. extinction for surrogate compounds?

Reactivity index

Mechanisms – with defined accuracies/uncertainties – how to

quantify?

Robust surrogate generation method

(Better) Validated mechanisms for monocyclic and bicyclic

alkanes

39

Thank You!!!!!