impact of alternative fuels on gas turbine and …...lawrence livermore national laboratory impact...

Lawrence Livermore National LaboratoryLawrence Livermore National Laboratory

Impact of Alternative Fuels on Gas Turbine and Diesel Engine Combustion

Mani Sarathy, William J. Pitz (PI), Charles K. Westbrook, Marco Mehl, LLNLHans-Heinrich Carstensen, Lam K. Huynh, Stephanie M. Villano, Anthony M.

Dean (PI), Colorado School of MinesFuel Summit, 20-23 September 2010, Princeton, NJ

LLNL-PRES-456812

Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, CA 94551This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

Acknowledgment: Sponsor

Office of Naval Research

Dr. Dave Shifler, Program Manager

2Lawrence Livermore National Laboratory2

Assess fuel impact on gas turbine engine performance

3Lawrence Livermore National Laboratory

From Med Colket, UTRC

Examine effects of alternative fuel (F-T and biofuels) on diesel engine combustion

• Navy has many diesel engines

•With Jim Cowart and Patrick Caton U S Naval Academy•With Jim Cowart and Patrick Caton, U.S. Naval Academy

N l A d C iNaval Academy Cooperative Fuels Research (CFR) diesel test engine


Navy is interested in Fischer-Tropsch (FT) fuels: They can contain large amounts of singly-methylated iso-alkanes

FT analysis (NIST*)57% single

0.20cycloalkanes

other isoalkanes

Syntroleum S-8 synthetic jet fuel

• 57% single methyl branch alkanes

• 25% n-alkanes

0.16

single methyl branch

n-alkanes

• 16% multiple branched alkanes

• 2% cycloalkanes

0.12

e f

ract

ion

* Smith et al. Int. J. Propulsion (2008) 2% cycloalkanes

0.08Mo

le Propulsion (2008)

0.04


0.00

C8 C9 C10 C11 C12 C13 C14 C15 C16

We are first focusing on 2-methyl alkanes have a single methyl branch and interesting ignition behavior

Species Cetane No.

nC7H16 54

C7H16-2 42

nC8H18 65

C8H18-2 49

nC9H20 75

C9H20-2 54


Chemical Kinetic Mechanism for 2-methyl alkanesy

Includes all 2-methyl alkanes up to C20 which covers the entire distillation range for gasoline, jet and diesel fuels

Built with the same reaction rate rules as our successful iso-octane and iso-cetane mechanisms

7,900 species

mechanisms.

27,000 reactions


Why do we need to get the distillation curve right for diesel combustion?

6- component diesel surrogate

diesel spray calculationVaporized fuel mass fraction

0.3 0.3

MW 165 0 MW 186 5

g

0.15

0.2

0.25

fract

ion

0.15

0.2

0.25

fract

ion

MW=165.0 MW=186.5

0

0.05

0.1mol

e

0

0.05

0.1mol

e

0c7h8 c10h22 c12h26 c14h30 c16h34 c18h38

component

0c7h8 c10h22 c12h26 c14h30 c16h34 c18h38

component

Light components come off first near the upstream portion of the diesel jet


From : Ra Y, Reitz RD. A vaporization model for discrete multi-component fuel sprays. Int. J. Multiphase Flow 2009

Experimental Validation• Idealized chemically reacting flow systems with/without simplified

transport phenomenonCombustion Parameters

Jet Stirred Reactors Premixed Laminar FlamesCombustion Parameters

Temperature

Pressure

Mixture fraction (air-fuel ratio)

Shock tube

Non Premixed Flames

( )

Mixing of fuel and air

Engine

RCM

High pressure flow reactors

Engine CombustionElectric Resistance

Heater

Evaporator

Fuel Inlet

Wall Heaters


Slide Table

Oxidizer Injector

Optical Access Ports

Sample Probe

2-methylhexane comparison in the RCM

45

50

Stoichiometric/’air’ mixtures15 t

Entire compression stroke

30

35

40

me (m

s)

15 atmExperimental data:

Galway:

stroke simulated and heat loss simulated after end of

20

25

30

n Delay Tim Galway:

Silke et al. Proc. Comb. Inst. (2005)

compression

5

10

15

Ignition

SimulationsExperiments

RCM

0650 700 750 800 850 900 950


Temperature at End of Compression (K)

2-methyl heptane model behaves well under high temperature shock tube conditionsp

100000 =3, P=21 atm, 1.355% fuel, O2/Ar

1000

10000

ay (μ

s)

Experiment Model

100

nitio

n de

l

10

Ign

experiment simulationExperiments: Dayton high pressure shock tubeKahandwala et al. Energy & Fuels (2008)

10.50 0.70 0.90 1.10 1.30 1.50

1000/T (1/K)


1000/T (1/K)

Previously shown that simulated ignition behavior of n-alkanes showed little dependence with carbon length

1.0E-0113 bar

1.0E-02

[s]

Stoichiometric fuel/air mixtures

1.0E-03

elay

Tim

e

nC8H18nC9H20

1.0E-04

Igni

tion

De nC9H20

nC10H22nC11H24nC12H26nC13H28nc14H30

1.0E-050.7 0.9 1.1 1.3 1.5 1.7

I

nC15H31nC16H34Westbrook et al. Comb. Flame 2009


1000/T [K]

2-methyl alkanes show effect of chain length at higher equivalence ratio and pressure (Dayton conditions):q p ( y )

10000 =3, P=21 atm, 1.355% fuel, O2/ArReactivity increases

(us)

increases with chain length

C10

1000

on d

elay

c10h22-2 - sarathy c12h26-2

C20

Igni

ti

y

c13h28-2 c14h30-2

c15h32-2 c16h34-2

Biggest fuel effect of chain length found in NTC region

1000 90 1 00 1 10 1 20 1 30 1 40 1 50 1 60

c18h38-2 c20h42-2region


0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.601000/T (1/K)

2-methylalkanes show less NTC than n-alkanes

10000 (=3, P=21 atm, 1.355% fuel, O2/Ar)2-methylalkane

(us)

less reactive than n-alkane

1000

on d

elay

Less NTC behavior in 2 th l lk

Igni

ti

nc12h26 c12h26-2

2-methylalkane

1000 90 1 00 1 10 1 20 1 30 1 40 1 50 1 60


0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.601000/T (1/K)

Comparison of reactivity for all the n-alkanes and 2-methyl alkanesy

10000 (=3, P=21 atm, 1.355% fuel, O2/Ar)Reactivity increases

2-methyl alkanes

(us)

increases with chain length

C10

1000

on d

elay

nc10h22 - westbrook c10h22-2 - sarathyn-alkanesC20

Igni

ti nc12h26 c12h26-2nc13h28 c13h28-2nc14h30 c14h30-2nc15h32 c15h32-2

Effect of chain length for n-alkanes now observed

1000 90 1 00 1 10 1 20 1 30 1 40 1 50 1 60

nc16h35 c16h34-2c18h38-2 c20h42-2


0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.601000/T (1/K)

Opposed-flow Diffusion Flame (OPPDIF) comparisons for a 2-methyl heptane

Oxidizer

Fuel Mixture• The one dimensional flame structure is ideal

Port diameter = 25.4 mm

P t G 20

for modeling.

• The emissions and temperature profiles are dependent on chemical kinetics due to the non-turbulent flame


Port Gap = 20 mmnon turbulent flame.

Overall good prediction of major and minor species of 2-methylheptane

8%

9%

N (%

) CO26000

7000

PM) C2H4

5%

6%

7%

NTR

ATIO

N CO

C8H18-24000

5000

RAT

ION

(P C2H2

CH4

2%

3%

4%

AR

CO

NC

EN

2000

3000

CO

NC

ENTR

C2H2

0%

1%

2%

0 2 4 6 8 10 12 14 16 18 20

MO

LA

0

1000M

OLA

R C

0 2 4 6 8 10 12 14 16 18 20

DISTANCE FROM FUEL PORT (mm)

Good prediction of

2 4 6 8 10DISTANCE FROM FUEL PORT (mm)


Good prediction of major species profiles

Important minor species are well predicted

Further experimental validations planned,2-methylheptane

• Counterflow Flame Ignition/ExtinctionUC San Diego

y p

g

•Jet Stirred ReactorCNRS Orleans, FranceCNRS Orleans, France

• Shock TubeRensselaer Polytechnic Institute New YorkRensselaer Polytechnic Institute, New York

• Ignition Quality Tester (IQT)NREL ColoradoNREL, Colorado

•Flow ReactorPrinceton University New Jersey

Electric ResistanceHeater

Evaporator


Princeton University, New Jersey Fuel Inlet

Slide Table

Oxidizer Injector

Optical Access Ports

Sample ProbeWall Heaters

Collaborating with the Naval Academy on fuel effects in diesel engine

10

100

ec]

Phi=4, 55 atm, fuel/air100% Hex

50%H

Mixtures of n-hexadecane and tolueneSimulations

0.1

1

10

nitio

n D

elay

[ms 50%Hex;

50%Tol30%Hex; 70%Tol20%Hex; 80%Tol10%Hex;

toluene(mixtures are by liquid volume)(Midshipman Aaron Carr)

Experiments on n hexadecane/toluene100% Hex

10% Hex; 90% Tol

770 K0.01

0.8 1 1.2 1.4

Ig

1000/T[K]

10%Hex; 90%Tol

Experiments on n-hexadecane/toluene mixtures in a Diesel CRF engine

(SAE 2010-01-2188: Mathes, Ries, Caton, Cowart, Prak, Hamilton, US Naval Academy)

Ignition delay is defined from start of injection

100% Hex 770 K

3

4

sec]

T=770K; Phi=4, 55 atm, fuel/air

AD)

Ignition delay is defined from start of injection to 10% mass burned

Simulations

Experiments

0

1

2

3

0 20 40 60 80 100gniti

on D

elay

[ms

Igni

tion

Del

ay (C

A


Ig

%Toluene by Volume

Summary for LLNL work

A new chemical kinetic mechanism for 2-methyl alkanes has been developed:p• The mechanism covers the entire distillation curve of practical gasoline, jet and diesel fuels (C7-C20).• The model successfully reproduces the experimental data currently available for this class of fuels.•Further validations plannedFurther validations planned.• Key differences between 2-methylalkanes and n-alkanes are reproduced by the model.


Detailed Modeling of Low-Temperature Alkane Oxidation:

High-Pressure Rate Rules for Alkyl+O2 Reactions

Hans-Heinrich Carstensen, Lam K. Huynh, Stephanie M. Villano, and Anthony M. Dean

Chemical Engineering DeptChemical Engineering Dept.

Colorado School of Mines

Third Fuels Summit

September 20 23 2010September 20-23, 2010

Development of large detailed chemical models facilitated by the use of rate estimation techniques

• Typical hydrocarbon gas phase reaction mechanisms contain — Hundreds of speciesHundreds of species— Thousands of reactions, many pressure-dependent

• Problem: How to assure consistency in rate constant assignments?— Experimental info only available for small fraction of reactions— Often literature data over limited range of conditions

High level calculations restricted to small molecules— High level calculations restricted to small molecules

• Solution: Develop accurate rate constant estimation method— Use high-level theory to calculate rate constants for smaller speciesg y p— Generalize results on a per-site basis and use these for larger species — Use rate rule based rate constants as input for pressure-dependence

l i


analysis— Approach applicable to either hand-generated or computer-generated

mechanisms

Model development: from electronic structure calculations to pressure-dependent rate constants

Geometry, Frequencies, Electronic Energy,

Gaussian Software®

Dipole Moment, Polarizability, …FANCY

Heat of Formation Entropy Heat Capacity

TSTdG

Heat of Formation, Entropy, Heat Capacity

3-Freq Representation, NASA Polynomials

CHEMDIS

High-pressure Rate Constants k(T) for

Elementary Reactions

k(T,P)

Pressure-dependent Rate Constants k(T,P) for Apparent Reactions


Reaction classes analyzed

H and CH3 Abstraction from Alkanes, Cycloalkanes, AlkenesRate Constant Rules for the Automated Generation of Gas-Phase Reaction Mechanisms, J. Phys. Chem. A, 2009, 113, 367-380

• Intramolecular H-AbstractionThe Kinetics of Pressure-Dependent Reactions, in Comprehensive ChemicalKinetics (Elsevier), 2007, 42 105-187

H and CH3 Abstraction from Alcohols, Elimination of Water from AlcoholsDevelopment of Detailed Kinetic Models For The Thermal Conversion of Biomass Via First Principle Methods And Rate Estimation Rules, inComputational Modeling in Lignocellulosic Biofuel Production, ACS Symposium Series

(in press)

• RO2 Isomerizations• RO2 Concerted Elimination of HO2

QOOH C li Eth + OH• QOOH = Cyclic Ether + OH• O2QOOH Isomerization• O2QOOH Concerted Elimination of HO2


Alkyl isomerizations consistent with expectations

Primary to secondary H- atom shift reactions:

Lower activation energy for 5 and 6-

Alkyl radicals(primary/secondary)(Primary to secondary)

energy for 5 and 6member ring TS s with less ring strain

Lower A-factor as more CH2 rotors tied up in TS Additional calculations ongoing to confirm consistent behavior

• Results used as basis for rate rules


N-propyl + O2 chemistry: Fast isomerization of CCCOO• adductleads to chain branching

CCCOO● adduct

This is the O2QOOH that leads to chain

• Only important pathways for n-propyl + O2 are isomerization, concerted elimination and

leads to chain branching


y p p y p py 2redissociation

i-propyl+O2: Slower isomerization of CC(OO•)C adductleads to chain inhibition

CC(OO●)C adduct

• Concerted elimination dominant for isopropyl + O2b hi th i hibit d


– branching pathway inhibited• Detailed calculations show other pathways can be neglected

RO2 isomerizations show same qualitative behavior as alkyl radicals

5-member TS 6-member TSOH

OHR

tertiaryprimary

RO O

primarytertiary

Activation energy depends on ring size and overall thermochemistry Again amenable to rule generation


g g

Comparison of model predictions to propane ignition over the NTC region in a RCM

Expect all predictions to be faster than data • Predictions adiabatic

Experiments27 atm=0.5fuel/”air” mixtures

• Expect heat loss at longer times in data

All models capture NTC behaviorNTC i t hi h T ith CSM• NTC region at higher T with CSM model

• Reduced CSM model, with much smaller reaction subsets for both 37 atmRO2 and O2QOOH, very similar to full model

Analysis suggests substantial differences in Galway and CSMGalway

Experiments

=0.5fuel/”air” mixtures

differences in Galway and CSM models• Galway model* uses LLNL rate

rules

CSMReduced CSM

y


Experimental data from Galway RCM:* Gallagher et al. Combustion and Flame 2008, 153, 316.

Significant differences in CSM vs. LLNL rate constants (e.g. RO2 isomerization)

CBS-QB3 results generally lower than LLNL values for 5-member TS CBS-QB3 results much higher than LLNL values for 6-member TS

• Mainly due to higher A-factors (much higher than alkyl i i ti )


isomerizations) Differences lead to significantly different reaction pathways

Summary/Next Steps Mechanism constructed with rate constants based on unadjusted CBS-

QB3 potential energy surfaces captures NTC behavior in propane oxidation• Need to extend mechanism to larger systems where more data

available to reach firm conclusions on its success Relatively few reactions of RO2 found to be important for ignition

calculations• Significantly simplifies accounting for effects of pressure on

reaction rates and branching ratios Extension to larger systems facilitated by ability to generalize results

into reaction rate rules Extend approach to consider second addition of O2 (to QOOH) that

leads to low temperature chain branchingleads to low temperature chain branching


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impact of alternative fuels on gas turbine and …...lawrence livermore national laboratory impact...

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